xref: /external/mesa3d/src/mesa/main/image.c

/*
 * Mesa 3-D graphics library
 * Version:  7.1
 *
 * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


/**
 * \file image.c
 * Image handling.
 */


#include "glheader.h"
#include "colormac.h"
#include "context.h"
#include "image.h"
#include "imports.h"
#include "macros.h"
#include "pixel.h"


/**
 * NOTE:
 * Normally, BYTE_TO_FLOAT(0) returns 0.00392  That causes problems when
 * we later convert the float to a packed integer value (such as for
 * GL_RGB5_A1) because we'll wind up with a non-zero value.
 *
 * We redefine the macros here so zero is handled correctly.
 */
#undef BYTE_TO_FLOAT
#define BYTE_TO_FLOAT(B)    ((B) == 0 ? 0.0F : ((2.0F * (B) + 1.0F) * (1.0F/255.0F)))

#undef SHORT_TO_FLOAT
#define SHORT_TO_FLOAT(S)   ((S) == 0 ? 0.0F : ((2.0F * (S) + 1.0F) * (1.0F/65535.0F)))



/** Compute ceiling of integer quotient of A divided by B. */
#define CEILING( A, B )  ( (A) % (B) == 0 ? (A)/(B) : (A)/(B)+1 )


/**
 * \return GL_TRUE if type is packed pixel type, GL_FALSE otherwise.
 */
GLboolean
_mesa_type_is_packed(GLenum type)
{
   switch (type) {
   case GL_UNSIGNED_BYTE_3_3_2:
   case GL_UNSIGNED_BYTE_2_3_3_REV:
   case GL_UNSIGNED_SHORT_5_6_5:
   case GL_UNSIGNED_SHORT_5_6_5_REV:
   case GL_UNSIGNED_SHORT_4_4_4_4:
   case GL_UNSIGNED_SHORT_4_4_4_4_REV:
   case GL_UNSIGNED_SHORT_5_5_5_1:
   case GL_UNSIGNED_SHORT_1_5_5_5_REV:
   case GL_UNSIGNED_INT_8_8_8_8:
   case GL_UNSIGNED_INT_8_8_8_8_REV:
   case GL_UNSIGNED_INT_10_10_10_2:
   case GL_UNSIGNED_INT_2_10_10_10_REV:
   case GL_UNSIGNED_SHORT_8_8_MESA:
   case GL_UNSIGNED_SHORT_8_8_REV_MESA:
   case GL_UNSIGNED_INT_24_8_EXT:
      return GL_TRUE;
   }

   return GL_FALSE;
}

/**
 * Flip the 8 bits in each byte of the given array.
 *
 * \param p array.
 * \param n number of bytes.
 *
 * \todo try this trick to flip bytes someday:
 * \code
 *  v = ((v & 0x55555555) << 1) | ((v >> 1) & 0x55555555);
 *  v = ((v & 0x33333333) << 2) | ((v >> 2) & 0x33333333);
 *  v = ((v & 0x0f0f0f0f) << 4) | ((v >> 4) & 0x0f0f0f0f);
 * \endcode
 */
static void
flip_bytes( GLubyte *p, GLuint n )
{
   GLuint i, a, b;
   for (i = 0; i < n; i++) {
      b = (GLuint) p[i];        /* words are often faster than bytes */
      a = ((b & 0x01) << 7) |
	  ((b & 0x02) << 5) |
	  ((b & 0x04) << 3) |
	  ((b & 0x08) << 1) |
	  ((b & 0x10) >> 1) |
	  ((b & 0x20) >> 3) |
	  ((b & 0x40) >> 5) |
	  ((b & 0x80) >> 7);
      p[i] = (GLubyte) a;
   }
}


/**
 * Flip the order of the 2 bytes in each word in the given array.
 *
 * \param p array.
 * \param n number of words.
 */
void
_mesa_swap2( GLushort *p, GLuint n )
{
   GLuint i;
   for (i = 0; i < n; i++) {
      p[i] = (p[i] >> 8) | ((p[i] << 8) & 0xff00);
   }
}



/*
 * Flip the order of the 4 bytes in each word in the given array.
 */
void
_mesa_swap4( GLuint *p, GLuint n )
{
   GLuint i, a, b;
   for (i = 0; i < n; i++) {
      b = p[i];
      a =  (b >> 24)
	| ((b >> 8) & 0xff00)
	| ((b << 8) & 0xff0000)
	| ((b << 24) & 0xff000000);
      p[i] = a;
   }
}


/**
 * Get the size of a GL data type.
 *
 * \param type GL data type.
 *
 * \return the size, in bytes, of the given data type, 0 if a GL_BITMAP, or -1
 * if an invalid type enum.
 */
GLint
_mesa_sizeof_type( GLenum type )
{
   switch (type) {
      case GL_BITMAP:
	 return 0;
      case GL_UNSIGNED_BYTE:
         return sizeof(GLubyte);
      case GL_BYTE:
	 return sizeof(GLbyte);
      case GL_UNSIGNED_SHORT:
	 return sizeof(GLushort);
      case GL_SHORT:
	 return sizeof(GLshort);
      case GL_UNSIGNED_INT:
	 return sizeof(GLuint);
      case GL_INT:
	 return sizeof(GLint);
      case GL_FLOAT:
	 return sizeof(GLfloat);
      case GL_DOUBLE:
	 return sizeof(GLdouble);
      case GL_HALF_FLOAT_ARB:
	 return sizeof(GLhalfARB);
      default:
         return -1;
   }
}


/**
 * Same as _mesa_sizeof_type() but also accepting the packed pixel
 * format data types.
 */
GLint
_mesa_sizeof_packed_type( GLenum type )
{
   switch (type) {
      case GL_BITMAP:
	 return 0;
      case GL_UNSIGNED_BYTE:
         return sizeof(GLubyte);
      case GL_BYTE:
	 return sizeof(GLbyte);
      case GL_UNSIGNED_SHORT:
	 return sizeof(GLushort);
      case GL_SHORT:
	 return sizeof(GLshort);
      case GL_UNSIGNED_INT:
	 return sizeof(GLuint);
      case GL_INT:
	 return sizeof(GLint);
      case GL_HALF_FLOAT_ARB:
	 return sizeof(GLhalfARB);
      case GL_FLOAT:
	 return sizeof(GLfloat);
      case GL_UNSIGNED_BYTE_3_3_2:
         return sizeof(GLubyte);
      case GL_UNSIGNED_BYTE_2_3_3_REV:
         return sizeof(GLubyte);
      case GL_UNSIGNED_SHORT_5_6_5:
         return sizeof(GLushort);
      case GL_UNSIGNED_SHORT_5_6_5_REV:
         return sizeof(GLushort);
      case GL_UNSIGNED_SHORT_4_4_4_4:
         return sizeof(GLushort);
      case GL_UNSIGNED_SHORT_4_4_4_4_REV:
         return sizeof(GLushort);
      case GL_UNSIGNED_SHORT_5_5_5_1:
         return sizeof(GLushort);
      case GL_UNSIGNED_SHORT_1_5_5_5_REV:
         return sizeof(GLushort);
      case GL_UNSIGNED_INT_8_8_8_8:
         return sizeof(GLuint);
      case GL_UNSIGNED_INT_8_8_8_8_REV:
         return sizeof(GLuint);
      case GL_UNSIGNED_INT_10_10_10_2:
         return sizeof(GLuint);
      case GL_UNSIGNED_INT_2_10_10_10_REV:
         return sizeof(GLuint);
      case GL_UNSIGNED_SHORT_8_8_MESA:
      case GL_UNSIGNED_SHORT_8_8_REV_MESA:
         return sizeof(GLushort);
      case GL_UNSIGNED_INT_24_8_EXT:
         return sizeof(GLuint);
      default:
         return -1;
   }
}


/**
 * Get the number of components in a pixel format.
 *
 * \param format pixel format.
 *
 * \return the number of components in the given format, or -1 if a bad format.
 */
GLint
_mesa_components_in_format( GLenum format )
{
   switch (format) {
      case GL_COLOR_INDEX:
      case GL_COLOR_INDEX1_EXT:
      case GL_COLOR_INDEX2_EXT:
      case GL_COLOR_INDEX4_EXT:
      case GL_COLOR_INDEX8_EXT:
      case GL_COLOR_INDEX12_EXT:
      case GL_COLOR_INDEX16_EXT:
      case GL_STENCIL_INDEX:
      case GL_DEPTH_COMPONENT:
      case GL_RED:
      case GL_GREEN:
      case GL_BLUE:
      case GL_ALPHA:
      case GL_LUMINANCE:
      case GL_INTENSITY:
         return 1;
      case GL_LUMINANCE_ALPHA:
	 return 2;
      case GL_RGB:
	 return 3;
      case GL_RGBA:
	 return 4;
      case GL_BGR:
	 return 3;
      case GL_BGRA:
	 return 4;
      case GL_ABGR_EXT:
         return 4;
      case GL_YCBCR_MESA:
         return 2;
      case GL_DEPTH_STENCIL_EXT:
         return 2;
      case GL_DUDV_ATI:
      case GL_DU8DV8_ATI:
         return 2;
      default:
         return -1;
   }
}


/**
 * Get the bytes per pixel of pixel format type pair.
 *
 * \param format pixel format.
 * \param type pixel type.
 *
 * \return bytes per pixel, or -1 if a bad format or type was given.
 */
GLint
_mesa_bytes_per_pixel( GLenum format, GLenum type )
{
   GLint comps = _mesa_components_in_format( format );
   if (comps < 0)
      return -1;

   switch (type) {
      case GL_BITMAP:
         return 0;  /* special case */
      case GL_BYTE:
      case GL_UNSIGNED_BYTE:
         return comps * sizeof(GLubyte);
      case GL_SHORT:
      case GL_UNSIGNED_SHORT:
         return comps * sizeof(GLshort);
      case GL_INT:
      case GL_UNSIGNED_INT:
         return comps * sizeof(GLint);
      case GL_FLOAT:
         return comps * sizeof(GLfloat);
      case GL_HALF_FLOAT_ARB:
         return comps * sizeof(GLhalfARB);
      case GL_UNSIGNED_BYTE_3_3_2:
      case GL_UNSIGNED_BYTE_2_3_3_REV:
         if (format == GL_RGB || format == GL_BGR)
            return sizeof(GLubyte);
         else
            return -1;  /* error */
      case GL_UNSIGNED_SHORT_5_6_5:
      case GL_UNSIGNED_SHORT_5_6_5_REV:
         if (format == GL_RGB || format == GL_BGR)
            return sizeof(GLushort);
         else
            return -1;  /* error */
      case GL_UNSIGNED_SHORT_4_4_4_4:
      case GL_UNSIGNED_SHORT_4_4_4_4_REV:
      case GL_UNSIGNED_SHORT_5_5_5_1:
      case GL_UNSIGNED_SHORT_1_5_5_5_REV:
         if (format == GL_RGBA || format == GL_BGRA || format == GL_ABGR_EXT)
            return sizeof(GLushort);
         else
            return -1;
      case GL_UNSIGNED_INT_8_8_8_8:
      case GL_UNSIGNED_INT_8_8_8_8_REV:
      case GL_UNSIGNED_INT_10_10_10_2:
      case GL_UNSIGNED_INT_2_10_10_10_REV:
         if (format == GL_RGBA || format == GL_BGRA || format == GL_ABGR_EXT)
            return sizeof(GLuint);
         else
            return -1;
      case GL_UNSIGNED_SHORT_8_8_MESA:
      case GL_UNSIGNED_SHORT_8_8_REV_MESA:
         if (format == GL_YCBCR_MESA)
            return sizeof(GLushort);
         else
            return -1;
      case GL_UNSIGNED_INT_24_8_EXT:
         if (format == GL_DEPTH_STENCIL_EXT)
            return sizeof(GLuint);
         else
            return -1;
      default:
         return -1;
   }
}


/**
 * Test for a legal pixel format and type.
 *
 * \param format pixel format.
 * \param type pixel type.
 *
 * \return GL_TRUE if the given pixel format and type are legal, or GL_FALSE
 * otherwise.
 */
GLboolean
_mesa_is_legal_format_and_type( GLcontext *ctx, GLenum format, GLenum type )
{
   switch (format) {
      case GL_COLOR_INDEX:
      case GL_STENCIL_INDEX:
         switch (type) {
            case GL_BITMAP:
            case GL_BYTE:
            case GL_UNSIGNED_BYTE:
            case GL_SHORT:
            case GL_UNSIGNED_SHORT:
            case GL_INT:
            case GL_UNSIGNED_INT:
            case GL_FLOAT:
               return GL_TRUE;
            case GL_HALF_FLOAT_ARB:
               return ctx->Extensions.ARB_half_float_pixel;
            default:
               return GL_FALSE;
         }
      case GL_RED:
      case GL_GREEN:
      case GL_BLUE:
      case GL_ALPHA:
#if 0 /* not legal!  see table 3.6 of the 1.5 spec */
      case GL_INTENSITY:
#endif
      case GL_LUMINANCE:
      case GL_LUMINANCE_ALPHA:
      case GL_DEPTH_COMPONENT:
         switch (type) {
            case GL_BYTE:
            case GL_UNSIGNED_BYTE:
            case GL_SHORT:
            case GL_UNSIGNED_SHORT:
            case GL_INT:
            case GL_UNSIGNED_INT:
            case GL_FLOAT:
               return GL_TRUE;
            case GL_HALF_FLOAT_ARB:
               return ctx->Extensions.ARB_half_float_pixel;
            default:
               return GL_FALSE;
         }
      case GL_RGB:
         switch (type) {
            case GL_BYTE:
            case GL_UNSIGNED_BYTE:
            case GL_SHORT:
            case GL_UNSIGNED_SHORT:
            case GL_INT:
            case GL_UNSIGNED_INT:
            case GL_FLOAT:
            case GL_UNSIGNED_BYTE_3_3_2:
            case GL_UNSIGNED_BYTE_2_3_3_REV:
            case GL_UNSIGNED_SHORT_5_6_5:
            case GL_UNSIGNED_SHORT_5_6_5_REV:
               return GL_TRUE;
            case GL_HALF_FLOAT_ARB:
               return ctx->Extensions.ARB_half_float_pixel;
            default:
               return GL_FALSE;
         }
      case GL_BGR:
         switch (type) {
            /* NOTE: no packed types are supported with BGR.  That's
             * intentional, according to the GL spec.
             */
            case GL_BYTE:
            case GL_UNSIGNED_BYTE:
            case GL_SHORT:
            case GL_UNSIGNED_SHORT:
            case GL_INT:
            case GL_UNSIGNED_INT:
            case GL_FLOAT:
               return GL_TRUE;
            case GL_HALF_FLOAT_ARB:
               return ctx->Extensions.ARB_half_float_pixel;
            default:
               return GL_FALSE;
         }
      case GL_RGBA:
      case GL_BGRA:
      case GL_ABGR_EXT:
         switch (type) {
            case GL_BYTE:
            case GL_UNSIGNED_BYTE:
            case GL_SHORT:
            case GL_UNSIGNED_SHORT:
            case GL_INT:
            case GL_UNSIGNED_INT:
            case GL_FLOAT:
            case GL_UNSIGNED_SHORT_4_4_4_4:
            case GL_UNSIGNED_SHORT_4_4_4_4_REV:
            case GL_UNSIGNED_SHORT_5_5_5_1:
            case GL_UNSIGNED_SHORT_1_5_5_5_REV:
            case GL_UNSIGNED_INT_8_8_8_8:
            case GL_UNSIGNED_INT_8_8_8_8_REV:
            case GL_UNSIGNED_INT_10_10_10_2:
            case GL_UNSIGNED_INT_2_10_10_10_REV:
               return GL_TRUE;
            case GL_HALF_FLOAT_ARB:
               return ctx->Extensions.ARB_half_float_pixel;
            default:
               return GL_FALSE;
         }
      case GL_YCBCR_MESA:
         if (type == GL_UNSIGNED_SHORT_8_8_MESA ||
             type == GL_UNSIGNED_SHORT_8_8_REV_MESA)
            return GL_TRUE;
         else
            return GL_FALSE;
      case GL_DEPTH_STENCIL_EXT:
         if (ctx->Extensions.EXT_packed_depth_stencil
             && type == GL_UNSIGNED_INT_24_8_EXT)
            return GL_TRUE;
         else
            return GL_FALSE;
      case GL_DUDV_ATI:
      case GL_DU8DV8_ATI:
         switch (type) {
            case GL_BYTE:
            case GL_UNSIGNED_BYTE:
            case GL_SHORT:
            case GL_UNSIGNED_SHORT:
            case GL_INT:
            case GL_UNSIGNED_INT:
            case GL_FLOAT:
               return GL_TRUE;
            default:
               return GL_FALSE;
         }
      default:
         ; /* fall-through */
   }
   return GL_FALSE;
}


/**
 * Return the address of a specific pixel in an image (1D, 2D or 3D).
 *
 * Pixel unpacking/packing parameters are observed according to \p packing.
 *
 * \param dimensions either 1, 2 or 3 to indicate dimensionality of image
 * \param image  starting address of image data
 * \param width  the image width
 * \param height  theimage height
 * \param format  the pixel format
 * \param type  the pixel data type
 * \param packing  the pixelstore attributes
 * \param img  which image in the volume (0 for 1D or 2D images)
 * \param row  row of pixel in the image (0 for 1D images)
 * \param column column of pixel in the image
 *
 * \return address of pixel on success, or NULL on error.
 *
 * \sa gl_pixelstore_attrib.
 */
GLvoid *
_mesa_image_address( GLuint dimensions,
                     const struct gl_pixelstore_attrib *packing,
                     const GLvoid *image,
                     GLsizei width, GLsizei height,
                     GLenum format, GLenum type,
                     GLint img, GLint row, GLint column )
{
   GLint alignment;        /* 1, 2 or 4 */
   GLint pixels_per_row;
   GLint rows_per_image;
   GLint skiprows;
   GLint skippixels;
   GLint skipimages;       /* for 3-D volume images */
   GLubyte *pixel_addr;

   ASSERT(dimensions >= 1 && dimensions <= 3);

   alignment = packing->Alignment;
   if (packing->RowLength > 0) {
      pixels_per_row = packing->RowLength;
   }
   else {
      pixels_per_row = width;
   }
   if (packing->ImageHeight > 0) {
      rows_per_image = packing->ImageHeight;
   }
   else {
      rows_per_image = height;
   }

   skippixels = packing->SkipPixels;
   /* Note: SKIP_ROWS _is_ used for 1D images */
   skiprows = packing->SkipRows;
   /* Note: SKIP_IMAGES is only used for 3D images */
   skipimages = (dimensions == 3) ? packing->SkipImages : 0;

   if (type == GL_BITMAP) {
      /* BITMAP data */
      GLint comp_per_pixel;   /* components per pixel */
      GLint bytes_per_comp;   /* bytes per component */
      GLint bytes_per_row;
      GLint bytes_per_image;

      /* Compute bytes per component */
      bytes_per_comp = _mesa_sizeof_packed_type( type );
      if (bytes_per_comp < 0) {
         return NULL;
      }

      /* Compute number of components per pixel */
      comp_per_pixel = _mesa_components_in_format( format );
      if (comp_per_pixel < 0) {
         return NULL;
      }

      bytes_per_row = alignment
                    * CEILING( comp_per_pixel*pixels_per_row, 8*alignment );

      bytes_per_image = bytes_per_row * rows_per_image;

      pixel_addr = (GLubyte *) image
                 + (skipimages + img) * bytes_per_image
                 + (skiprows + row) * bytes_per_row
                 + (skippixels + column) / 8;
   }
   else {
      /* Non-BITMAP data */
      GLint bytes_per_pixel, bytes_per_row, remainder, bytes_per_image;
      GLint topOfImage;

      bytes_per_pixel = _mesa_bytes_per_pixel( format, type );

      /* The pixel type and format should have been error checked earlier */
      assert(bytes_per_pixel > 0);

      bytes_per_row = pixels_per_row * bytes_per_pixel;
      remainder = bytes_per_row % alignment;
      if (remainder > 0)
         bytes_per_row += (alignment - remainder);

      ASSERT(bytes_per_row % alignment == 0);

      bytes_per_image = bytes_per_row * rows_per_image;

      if (packing->Invert) {
         /* set pixel_addr to the last row */
         topOfImage = bytes_per_row * (height - 1);
         bytes_per_row = -bytes_per_row;
      }
      else {
         topOfImage = 0;
      }

      /* compute final pixel address */
      pixel_addr = (GLubyte *) image
                 + (skipimages + img) * bytes_per_image
                 + topOfImage
                 + (skiprows + row) * bytes_per_row
                 + (skippixels + column) * bytes_per_pixel;
   }

   return (GLvoid *) pixel_addr;
}


GLvoid *
_mesa_image_address1d( const struct gl_pixelstore_attrib *packing,
                       const GLvoid *image,
                       GLsizei width,
                       GLenum format, GLenum type,
                       GLint column )
{
   return _mesa_image_address(1, packing, image, width, 1,
                              format, type, 0, 0, column);
}


GLvoid *
_mesa_image_address2d( const struct gl_pixelstore_attrib *packing,
                       const GLvoid *image,
                       GLsizei width, GLsizei height,
                       GLenum format, GLenum type,
                       GLint row, GLint column )
{
   return _mesa_image_address(2, packing, image, width, height,
                              format, type, 0, row, column);
}


GLvoid *
_mesa_image_address3d( const struct gl_pixelstore_attrib *packing,
                       const GLvoid *image,
                       GLsizei width, GLsizei height,
                       GLenum format, GLenum type,
                       GLint img, GLint row, GLint column )
{
   return _mesa_image_address(3, packing, image, width, height,
                              format, type, img, row, column);
}



/**
 * Compute the stride (in bytes) between image rows.
 *
 * \param packing the pixelstore attributes
 * \param width image width.
 * \param format pixel format.
 * \param type pixel data type.
 *
 * \return the stride in bytes for the given parameters, or -1 if error
 */
GLint
_mesa_image_row_stride( const struct gl_pixelstore_attrib *packing,
                        GLint width, GLenum format, GLenum type )
{
   GLint bytesPerRow, remainder;

   ASSERT(packing);

   if (type == GL_BITMAP) {
      if (packing->RowLength == 0) {
         bytesPerRow = (width + 7) / 8;
      }
      else {
         bytesPerRow = (packing->RowLength + 7) / 8;
      }
   }
   else {
      /* Non-BITMAP data */
      const GLint bytesPerPixel = _mesa_bytes_per_pixel(format, type);
      if (bytesPerPixel <= 0)
         return -1;  /* error */
      if (packing->RowLength == 0) {
         bytesPerRow = bytesPerPixel * width;
      }
      else {
         bytesPerRow = bytesPerPixel * packing->RowLength;
      }
   }

   remainder = bytesPerRow % packing->Alignment;
   if (remainder > 0) {
      bytesPerRow += (packing->Alignment - remainder);
   }

   if (packing->Invert) {
      /* negate the bytes per row (negative row stride) */
      bytesPerRow = -bytesPerRow;
   }

   return bytesPerRow;
}


#if _HAVE_FULL_GL

/*
 * Compute the stride between images in a 3D texture (in bytes) for the given
 * pixel packing parameters and image width, format and type.
 */
GLint
_mesa_image_image_stride( const struct gl_pixelstore_attrib *packing,
                          GLint width, GLint height,
                          GLenum format, GLenum type )
{
   ASSERT(packing);
   ASSERT(type != GL_BITMAP);

   {
      const GLint bytesPerPixel = _mesa_bytes_per_pixel(format, type);
      GLint bytesPerRow, bytesPerImage, remainder;

      if (bytesPerPixel <= 0)
         return -1;  /* error */
      if (packing->RowLength == 0) {
         bytesPerRow = bytesPerPixel * width;
      }
      else {
         bytesPerRow = bytesPerPixel * packing->RowLength;
      }
      remainder = bytesPerRow % packing->Alignment;
      if (remainder > 0)
         bytesPerRow += (packing->Alignment - remainder);

      if (packing->ImageHeight == 0)
         bytesPerImage = bytesPerRow * height;
      else
         bytesPerImage = bytesPerRow * packing->ImageHeight;

      return bytesPerImage;
   }
}


/*
 * Unpack a 32x32 pixel polygon stipple from user memory using the
 * current pixel unpack settings.
 */
void
_mesa_unpack_polygon_stipple( const GLubyte *pattern, GLuint dest[32],
                              const struct gl_pixelstore_attrib *unpacking )
{
   GLubyte *ptrn = (GLubyte *) _mesa_unpack_bitmap(32, 32, pattern, unpacking);
   if (ptrn) {
      /* Convert pattern from GLubytes to GLuints and handle big/little
       * endian differences
       */
      GLubyte *p = ptrn;
      GLint i;
      for (i = 0; i < 32; i++) {
         dest[i] = (p[0] << 24)
                 | (p[1] << 16)
                 | (p[2] <<  8)
                 | (p[3]      );
         p += 4;
      }
      _mesa_free(ptrn);
   }
}


/*
 * Pack polygon stipple into user memory given current pixel packing
 * settings.
 */
void
_mesa_pack_polygon_stipple( const GLuint pattern[32], GLubyte *dest,
                            const struct gl_pixelstore_attrib *packing )
{
   /* Convert pattern from GLuints to GLubytes to handle big/little
    * endian differences.
    */
   GLubyte ptrn[32*4];
   GLint i;
   for (i = 0; i < 32; i++) {
      ptrn[i * 4 + 0] = (GLubyte) ((pattern[i] >> 24) & 0xff);
      ptrn[i * 4 + 1] = (GLubyte) ((pattern[i] >> 16) & 0xff);
      ptrn[i * 4 + 2] = (GLubyte) ((pattern[i] >> 8 ) & 0xff);
      ptrn[i * 4 + 3] = (GLubyte) ((pattern[i]      ) & 0xff);
   }

   _mesa_pack_bitmap(32, 32, ptrn, dest, packing);
}


/*
 * Unpack bitmap data.  Resulting data will be in most-significant-bit-first
 * order with row alignment = 1 byte.
 */
GLvoid *
_mesa_unpack_bitmap( GLint width, GLint height, const GLubyte *pixels,
                     const struct gl_pixelstore_attrib *packing )
{
   GLint bytes, row, width_in_bytes;
   GLubyte *buffer, *dst;

   if (!pixels)
      return NULL;

   /* Alloc dest storage */
   bytes = ((width + 7) / 8 * height);
   buffer = (GLubyte *) _mesa_malloc( bytes );
   if (!buffer)
      return NULL;

   width_in_bytes = CEILING( width, 8 );
   dst = buffer;
   for (row = 0; row < height; row++) {
      const GLubyte *src = (const GLubyte *)
         _mesa_image_address2d(packing, pixels, width, height,
                               GL_COLOR_INDEX, GL_BITMAP, row, 0);
      if (!src) {
         _mesa_free(buffer);
         return NULL;
      }

      if ((packing->SkipPixels & 7) == 0) {
         _mesa_memcpy( dst, src, width_in_bytes );
         if (packing->LsbFirst) {
            flip_bytes( dst, width_in_bytes );
         }
      }
      else {
         /* handling SkipPixels is a bit tricky (no pun intended!) */
         GLint i;
         if (packing->LsbFirst) {
            GLubyte srcMask = 1 << (packing->SkipPixels & 0x7);
            GLubyte dstMask = 128;
            const GLubyte *s = src;
            GLubyte *d = dst;
            *d = 0;
            for (i = 0; i < width; i++) {
               if (*s & srcMask) {
                  *d |= dstMask;
               }
               if (srcMask == 128) {
                  srcMask = 1;
                  s++;
               }
               else {
                  srcMask = srcMask << 1;
               }
               if (dstMask == 1) {
                  dstMask = 128;
                  d++;
                  *d = 0;
               }
               else {
                  dstMask = dstMask >> 1;
               }
            }
         }
         else {
            GLubyte srcMask = 128 >> (packing->SkipPixels & 0x7);
            GLubyte dstMask = 128;
            const GLubyte *s = src;
            GLubyte *d = dst;
            *d = 0;
            for (i = 0; i < width; i++) {
               if (*s & srcMask) {
                  *d |= dstMask;
               }
               if (srcMask == 1) {
                  srcMask = 128;
                  s++;
               }
               else {
                  srcMask = srcMask >> 1;
               }
               if (dstMask == 1) {
                  dstMask = 128;
                  d++;
                  *d = 0;
               }
               else {
                  dstMask = dstMask >> 1;
               }
            }
         }
      }
      dst += width_in_bytes;
   }

   return buffer;
}


/*
 * Pack bitmap data.
 */
void
_mesa_pack_bitmap( GLint width, GLint height, const GLubyte *source,
                   GLubyte *dest, const struct gl_pixelstore_attrib *packing )
{
   GLint row, width_in_bytes;
   const GLubyte *src;

   if (!source)
      return;

   width_in_bytes = CEILING( width, 8 );
   src = source;
   for (row = 0; row < height; row++) {
      GLubyte *dst = (GLubyte *) _mesa_image_address2d(packing, dest,
                       width, height, GL_COLOR_INDEX, GL_BITMAP, row, 0);
      if (!dst)
         return;

      if ((packing->SkipPixels & 7) == 0) {
         _mesa_memcpy( dst, src, width_in_bytes );
         if (packing->LsbFirst) {
            flip_bytes( dst, width_in_bytes );
         }
      }
      else {
         /* handling SkipPixels is a bit tricky (no pun intended!) */
         GLint i;
         if (packing->LsbFirst) {
            GLubyte srcMask = 128;
            GLubyte dstMask = 1 << (packing->SkipPixels & 0x7);
            const GLubyte *s = src;
            GLubyte *d = dst;
            *d = 0;
            for (i = 0; i < width; i++) {
               if (*s & srcMask) {
                  *d |= dstMask;
               }
               if (srcMask == 1) {
                  srcMask = 128;
                  s++;
               }
               else {
                  srcMask = srcMask >> 1;
               }
               if (dstMask == 128) {
                  dstMask = 1;
                  d++;
                  *d = 0;
               }
               else {
                  dstMask = dstMask << 1;
               }
            }
         }
         else {
            GLubyte srcMask = 128;
            GLubyte dstMask = 128 >> (packing->SkipPixels & 0x7);
            const GLubyte *s = src;
            GLubyte *d = dst;
            *d = 0;
            for (i = 0; i < width; i++) {
               if (*s & srcMask) {
                  *d |= dstMask;
               }
               if (srcMask == 1) {
                  srcMask = 128;
                  s++;
               }
               else {
                  srcMask = srcMask >> 1;
               }
               if (dstMask == 1) {
                  dstMask = 128;
                  d++;
                  *d = 0;
               }
               else {
                  dstMask = dstMask >> 1;
               }
            }
         }
      }
      src += width_in_bytes;
   }
}


/**********************************************************************/
/*****                  Pixel processing functions               ******/
/**********************************************************************/

/*
 * Apply scale and bias factors to an array of RGBA pixels.
 */
void
_mesa_scale_and_bias_rgba(GLuint n, GLfloat rgba[][4],
                          GLfloat rScale, GLfloat gScale,
                          GLfloat bScale, GLfloat aScale,
                          GLfloat rBias, GLfloat gBias,
                          GLfloat bBias, GLfloat aBias)
{
   if (rScale != 1.0 || rBias != 0.0) {
      GLuint i;
      for (i = 0; i < n; i++) {
         rgba[i][RCOMP] = rgba[i][RCOMP] * rScale + rBias;
      }
   }
   if (gScale != 1.0 || gBias != 0.0) {
      GLuint i;
      for (i = 0; i < n; i++) {
         rgba[i][GCOMP] = rgba[i][GCOMP] * gScale + gBias;
      }
   }
   if (bScale != 1.0 || bBias != 0.0) {
      GLuint i;
      for (i = 0; i < n; i++) {
         rgba[i][BCOMP] = rgba[i][BCOMP] * bScale + bBias;
      }
   }
   if (aScale != 1.0 || aBias != 0.0) {
      GLuint i;
      for (i = 0; i < n; i++) {
         rgba[i][ACOMP] = rgba[i][ACOMP] * aScale + aBias;
      }
   }
}


/*
 * Apply pixel mapping to an array of floating point RGBA pixels.
 */
void
_mesa_map_rgba( const GLcontext *ctx, GLuint n, GLfloat rgba[][4] )
{
   const GLfloat rscale = (GLfloat) (ctx->PixelMaps.RtoR.Size - 1);
   const GLfloat gscale = (GLfloat) (ctx->PixelMaps.GtoG.Size - 1);
   const GLfloat bscale = (GLfloat) (ctx->PixelMaps.BtoB.Size - 1);
   const GLfloat ascale = (GLfloat) (ctx->PixelMaps.AtoA.Size - 1);
   const GLfloat *rMap = ctx->PixelMaps.RtoR.Map;
   const GLfloat *gMap = ctx->PixelMaps.GtoG.Map;
   const GLfloat *bMap = ctx->PixelMaps.BtoB.Map;
   const GLfloat *aMap = ctx->PixelMaps.AtoA.Map;
   GLuint i;
   for (i=0;i<n;i++) {
      GLfloat r = CLAMP(rgba[i][RCOMP], 0.0F, 1.0F);
      GLfloat g = CLAMP(rgba[i][GCOMP], 0.0F, 1.0F);
      GLfloat b = CLAMP(rgba[i][BCOMP], 0.0F, 1.0F);
      GLfloat a = CLAMP(rgba[i][ACOMP], 0.0F, 1.0F);
      rgba[i][RCOMP] = rMap[IROUND(r * rscale)];
      rgba[i][GCOMP] = gMap[IROUND(g * gscale)];
      rgba[i][BCOMP] = bMap[IROUND(b * bscale)];
      rgba[i][ACOMP] = aMap[IROUND(a * ascale)];
   }
}


/*
 * Apply the color matrix and post color matrix scaling and biasing.
 */
void
_mesa_transform_rgba(const GLcontext *ctx, GLuint n, GLfloat rgba[][4])
{
   const GLfloat rs = ctx->Pixel.PostColorMatrixScale[0];
   const GLfloat rb = ctx->Pixel.PostColorMatrixBias[0];
   const GLfloat gs = ctx->Pixel.PostColorMatrixScale[1];
   const GLfloat gb = ctx->Pixel.PostColorMatrixBias[1];
   const GLfloat bs = ctx->Pixel.PostColorMatrixScale[2];
   const GLfloat bb = ctx->Pixel.PostColorMatrixBias[2];
   const GLfloat as = ctx->Pixel.PostColorMatrixScale[3];
   const GLfloat ab = ctx->Pixel.PostColorMatrixBias[3];
   const GLfloat *m = ctx->ColorMatrixStack.Top->m;
   GLuint i;
   for (i = 0; i < n; i++) {
      const GLfloat r = rgba[i][RCOMP];
      const GLfloat g = rgba[i][GCOMP];
      const GLfloat b = rgba[i][BCOMP];
      const GLfloat a = rgba[i][ACOMP];
      rgba[i][RCOMP] = (m[0] * r + m[4] * g + m[ 8] * b + m[12] * a) * rs + rb;
      rgba[i][GCOMP] = (m[1] * r + m[5] * g + m[ 9] * b + m[13] * a) * gs + gb;
      rgba[i][BCOMP] = (m[2] * r + m[6] * g + m[10] * b + m[14] * a) * bs + bb;
      rgba[i][ACOMP] = (m[3] * r + m[7] * g + m[11] * b + m[15] * a) * as + ab;
   }
}


/**
 * Apply a color table lookup to an array of floating point RGBA colors.
 */
void
_mesa_lookup_rgba_float(const struct gl_color_table *table,
                        GLuint n, GLfloat rgba[][4])
{
   const GLint max = table->Size - 1;
   const GLfloat scale = (GLfloat) max;
   const GLfloat *lut = table->TableF;
   GLuint i;

   if (!table->TableF || table->Size == 0)
      return;

   switch (table->_BaseFormat) {
      case GL_INTENSITY:
         /* replace RGBA with I */
         for (i = 0; i < n; i++) {
            GLint j = IROUND(rgba[i][RCOMP] * scale);
            GLfloat c = lut[CLAMP(j, 0, max)];
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] =
            rgba[i][ACOMP] = c;
         }
         break;
      case GL_LUMINANCE:
         /* replace RGB with L */
         for (i = 0; i < n; i++) {
            GLint j = IROUND(rgba[i][RCOMP] * scale);
            GLfloat c = lut[CLAMP(j, 0, max)];
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] = c;
         }
         break;
      case GL_ALPHA:
         /* replace A with A */
         for (i = 0; i < n; i++) {
            GLint j = IROUND(rgba[i][ACOMP] * scale);
            rgba[i][ACOMP] = lut[CLAMP(j, 0, max)];
         }
         break;
      case GL_LUMINANCE_ALPHA:
         /* replace RGBA with LLLA */
         for (i = 0; i < n; i++) {
            GLint jL = IROUND(rgba[i][RCOMP] * scale);
            GLint jA = IROUND(rgba[i][ACOMP] * scale);
            GLfloat luminance, alpha;
            jL = CLAMP(jL, 0, max);
            jA = CLAMP(jA, 0, max);
            luminance = lut[jL * 2 + 0];
            alpha     = lut[jA * 2 + 1];
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] = luminance;
            rgba[i][ACOMP] = alpha;;
         }
         break;
      case GL_RGB:
         /* replace RGB with RGB */
         for (i = 0; i < n; i++) {
            GLint jR = IROUND(rgba[i][RCOMP] * scale);
            GLint jG = IROUND(rgba[i][GCOMP] * scale);
            GLint jB = IROUND(rgba[i][BCOMP] * scale);
            jR = CLAMP(jR, 0, max);
            jG = CLAMP(jG, 0, max);
            jB = CLAMP(jB, 0, max);
            rgba[i][RCOMP] = lut[jR * 3 + 0];
            rgba[i][GCOMP] = lut[jG * 3 + 1];
            rgba[i][BCOMP] = lut[jB * 3 + 2];
         }
         break;
      case GL_RGBA:
         /* replace RGBA with RGBA */
         for (i = 0; i < n; i++) {
            GLint jR = IROUND(rgba[i][RCOMP] * scale);
            GLint jG = IROUND(rgba[i][GCOMP] * scale);
            GLint jB = IROUND(rgba[i][BCOMP] * scale);
            GLint jA = IROUND(rgba[i][ACOMP] * scale);
            jR = CLAMP(jR, 0, max);
            jG = CLAMP(jG, 0, max);
            jB = CLAMP(jB, 0, max);
            jA = CLAMP(jA, 0, max);
            rgba[i][RCOMP] = lut[jR * 4 + 0];
            rgba[i][GCOMP] = lut[jG * 4 + 1];
            rgba[i][BCOMP] = lut[jB * 4 + 2];
            rgba[i][ACOMP] = lut[jA * 4 + 3];
         }
         break;
      default:
         _mesa_problem(NULL, "Bad format in _mesa_lookup_rgba_float");
         return;
   }
}



/**
 * Apply a color table lookup to an array of ubyte/RGBA colors.
 */
void
_mesa_lookup_rgba_ubyte(const struct gl_color_table *table,
                        GLuint n, GLubyte rgba[][4])
{
   const GLubyte *lut = table->TableUB;
   const GLfloat scale = (GLfloat) (table->Size - 1) / (GLfloat)255.0;
   GLuint i;

   if (!table->TableUB || table->Size == 0)
      return;

   switch (table->_BaseFormat) {
   case GL_INTENSITY:
      /* replace RGBA with I */
      if (table->Size == 256) {
         for (i = 0; i < n; i++) {
            const GLubyte c = lut[rgba[i][RCOMP]];
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] =
            rgba[i][ACOMP] = c;
         }
      }
      else {
         for (i = 0; i < n; i++) {
            GLint j = IROUND((GLfloat) rgba[i][RCOMP] * scale);
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] =
            rgba[i][ACOMP] = lut[j];
         }
      }
      break;
   case GL_LUMINANCE:
      /* replace RGB with L */
      if (table->Size == 256) {
         for (i = 0; i < n; i++) {
            const GLubyte c = lut[rgba[i][RCOMP]];
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] = c;
         }
      }
      else {
         for (i = 0; i < n; i++) {
            GLint j = IROUND((GLfloat) rgba[i][RCOMP] * scale);
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] = lut[j];
         }
      }
      break;
   case GL_ALPHA:
      /* replace A with A */
      if (table->Size == 256) {
         for (i = 0; i < n; i++) {
            rgba[i][ACOMP] = lut[rgba[i][ACOMP]];
         }
      }
      else {
         for (i = 0; i < n; i++) {
            GLint j = IROUND((GLfloat) rgba[i][ACOMP] * scale);
            rgba[i][ACOMP] = lut[j];
         }
      }
      break;
   case GL_LUMINANCE_ALPHA:
      /* replace RGBA with LLLA */
      if (table->Size == 256) {
         for (i = 0; i < n; i++) {
            GLubyte l = lut[rgba[i][RCOMP] * 2 + 0];
            GLubyte a = lut[rgba[i][ACOMP] * 2 + 1];;
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] = l;
            rgba[i][ACOMP] = a;
         }
      }
      else {
         for (i = 0; i < n; i++) {
            GLint jL = IROUND((GLfloat) rgba[i][RCOMP] * scale);
            GLint jA = IROUND((GLfloat) rgba[i][ACOMP] * scale);
            GLubyte luminance = lut[jL * 2 + 0];
            GLubyte alpha     = lut[jA * 2 + 1];
            rgba[i][RCOMP] =
            rgba[i][GCOMP] =
            rgba[i][BCOMP] = luminance;
            rgba[i][ACOMP] = alpha;
         }
      }
      break;
   case GL_RGB:
      if (table->Size == 256) {
         for (i = 0; i < n; i++) {
            rgba[i][RCOMP] = lut[rgba[i][RCOMP] * 3 + 0];
            rgba[i][GCOMP] = lut[rgba[i][GCOMP] * 3 + 1];
            rgba[i][BCOMP] = lut[rgba[i][BCOMP] * 3 + 2];
         }
      }
      else {
         for (i = 0; i < n; i++) {
            GLint jR = IROUND((GLfloat) rgba[i][RCOMP] * scale);
            GLint jG = IROUND((GLfloat) rgba[i][GCOMP] * scale);
            GLint jB = IROUND((GLfloat) rgba[i][BCOMP] * scale);
            rgba[i][RCOMP] = lut[jR * 3 + 0];
            rgba[i][GCOMP] = lut[jG * 3 + 1];
            rgba[i][BCOMP] = lut[jB * 3 + 2];
         }
      }
      break;
   case GL_RGBA:
      if (table->Size == 256) {
         for (i = 0; i < n; i++) {
            rgba[i][RCOMP] = lut[rgba[i][RCOMP] * 4 + 0];
            rgba[i][GCOMP] = lut[rgba[i][GCOMP] * 4 + 1];
            rgba[i][BCOMP] = lut[rgba[i][BCOMP] * 4 + 2];
            rgba[i][ACOMP] = lut[rgba[i][ACOMP] * 4 + 3];
         }
      }
      else {
         for (i = 0; i < n; i++) {
            GLint jR = IROUND((GLfloat) rgba[i][RCOMP] * scale);
            GLint jG = IROUND((GLfloat) rgba[i][GCOMP] * scale);
            GLint jB = IROUND((GLfloat) rgba[i][BCOMP] * scale);
            GLint jA = IROUND((GLfloat) rgba[i][ACOMP] * scale);
            CLAMPED_FLOAT_TO_CHAN(rgba[i][RCOMP], lut[jR * 4 + 0]);
            CLAMPED_FLOAT_TO_CHAN(rgba[i][GCOMP], lut[jG * 4 + 1]);
            CLAMPED_FLOAT_TO_CHAN(rgba[i][BCOMP], lut[jB * 4 + 2]);
            CLAMPED_FLOAT_TO_CHAN(rgba[i][ACOMP], lut[jA * 4 + 3]);
         }
      }
      break;
   default:
      _mesa_problem(NULL, "Bad format in _mesa_lookup_rgba_chan");
      return;
   }
}



/*
 * Map color indexes to float rgba values.
 */
void
_mesa_map_ci_to_rgba( const GLcontext *ctx, GLuint n,
                      const GLuint index[], GLfloat rgba[][4] )
{
   GLuint rmask = ctx->PixelMaps.ItoR.Size - 1;
   GLuint gmask = ctx->PixelMaps.ItoG.Size - 1;
   GLuint bmask = ctx->PixelMaps.ItoB.Size - 1;
   GLuint amask = ctx->PixelMaps.ItoA.Size - 1;
   const GLfloat *rMap = ctx->PixelMaps.ItoR.Map;
   const GLfloat *gMap = ctx->PixelMaps.ItoG.Map;
   const GLfloat *bMap = ctx->PixelMaps.ItoB.Map;
   const GLfloat *aMap = ctx->PixelMaps.ItoA.Map;
   GLuint i;
   for (i=0;i<n;i++) {
      rgba[i][RCOMP] = rMap[index[i] & rmask];
      rgba[i][GCOMP] = gMap[index[i] & gmask];
      rgba[i][BCOMP] = bMap[index[i] & bmask];
      rgba[i][ACOMP] = aMap[index[i] & amask];
   }
}


/**
 * Map ubyte color indexes to ubyte/RGBA values.
 */
void
_mesa_map_ci8_to_rgba8(const GLcontext *ctx, GLuint n, const GLubyte index[],
                       GLubyte rgba[][4])
{
   GLuint rmask = ctx->PixelMaps.ItoR.Size - 1;
   GLuint gmask = ctx->PixelMaps.ItoG.Size - 1;
   GLuint bmask = ctx->PixelMaps.ItoB.Size - 1;
   GLuint amask = ctx->PixelMaps.ItoA.Size - 1;
   const GLubyte *rMap = ctx->PixelMaps.ItoR.Map8;
   const GLubyte *gMap = ctx->PixelMaps.ItoG.Map8;
   const GLubyte *bMap = ctx->PixelMaps.ItoB.Map8;
   const GLubyte *aMap = ctx->PixelMaps.ItoA.Map8;
   GLuint i;
   for (i=0;i<n;i++) {
      rgba[i][RCOMP] = rMap[index[i] & rmask];
      rgba[i][GCOMP] = gMap[index[i] & gmask];
      rgba[i][BCOMP] = bMap[index[i] & bmask];
      rgba[i][ACOMP] = aMap[index[i] & amask];
   }
}


void
_mesa_scale_and_bias_depth(const GLcontext *ctx, GLuint n,
                           GLfloat depthValues[])
{
   const GLfloat scale = ctx->Pixel.DepthScale;
   const GLfloat bias = ctx->Pixel.DepthBias;
   GLuint i;
   for (i = 0; i < n; i++) {
      GLfloat d = depthValues[i] * scale + bias;
      depthValues[i] = CLAMP(d, 0.0F, 1.0F);
   }
}


void
_mesa_scale_and_bias_depth_uint(const GLcontext *ctx, GLuint n,
                                GLuint depthValues[])
{
   const GLdouble max = (double) 0xffffffff;
   const GLdouble scale = ctx->Pixel.DepthScale;
   const GLdouble bias = ctx->Pixel.DepthBias * max;
   GLuint i;
   for (i = 0; i < n; i++) {
      GLdouble d = (GLdouble) depthValues[i] * scale + bias;
      d = CLAMP(d, 0.0, max);
      depthValues[i] = (GLuint) d;
   }
}



/*
 * Update the min/max values from an array of fragment colors.
 */
static void
update_minmax(GLcontext *ctx, GLuint n, const GLfloat rgba[][4])
{
   GLuint i;
   for (i = 0; i < n; i++) {
      /* update mins */
      if (rgba[i][RCOMP] < ctx->MinMax.Min[RCOMP])
         ctx->MinMax.Min[RCOMP] = rgba[i][RCOMP];
      if (rgba[i][GCOMP] < ctx->MinMax.Min[GCOMP])
         ctx->MinMax.Min[GCOMP] = rgba[i][GCOMP];
      if (rgba[i][BCOMP] < ctx->MinMax.Min[BCOMP])
         ctx->MinMax.Min[BCOMP] = rgba[i][BCOMP];
      if (rgba[i][ACOMP] < ctx->MinMax.Min[ACOMP])
         ctx->MinMax.Min[ACOMP] = rgba[i][ACOMP];

      /* update maxs */
      if (rgba[i][RCOMP] > ctx->MinMax.Max[RCOMP])
         ctx->MinMax.Max[RCOMP] = rgba[i][RCOMP];
      if (rgba[i][GCOMP] > ctx->MinMax.Max[GCOMP])
         ctx->MinMax.Max[GCOMP] = rgba[i][GCOMP];
      if (rgba[i][BCOMP] > ctx->MinMax.Max[BCOMP])
         ctx->MinMax.Max[BCOMP] = rgba[i][BCOMP];
      if (rgba[i][ACOMP] > ctx->MinMax.Max[ACOMP])
         ctx->MinMax.Max[ACOMP] = rgba[i][ACOMP];
   }
}


/*
 * Update the histogram values from an array of fragment colors.
 */
static void
update_histogram(GLcontext *ctx, GLuint n, const GLfloat rgba[][4])
{
   const GLint max = ctx->Histogram.Width - 1;
   GLfloat w = (GLfloat) max;
   GLuint i;

   if (ctx->Histogram.Width == 0)
      return;

   for (i = 0; i < n; i++) {
      GLint ri = IROUND(rgba[i][RCOMP] * w);
      GLint gi = IROUND(rgba[i][GCOMP] * w);
      GLint bi = IROUND(rgba[i][BCOMP] * w);
      GLint ai = IROUND(rgba[i][ACOMP] * w);
      ri = CLAMP(ri, 0, max);
      gi = CLAMP(gi, 0, max);
      bi = CLAMP(bi, 0, max);
      ai = CLAMP(ai, 0, max);
      ctx->Histogram.Count[ri][RCOMP]++;
      ctx->Histogram.Count[gi][GCOMP]++;
      ctx->Histogram.Count[bi][BCOMP]++;
      ctx->Histogram.Count[ai][ACOMP]++;
   }
}


/**
 * Apply various pixel transfer operations to an array of RGBA pixels
 * as indicated by the transferOps bitmask
 */
void
_mesa_apply_rgba_transfer_ops(GLcontext *ctx, GLbitfield transferOps,
                              GLuint n, GLfloat rgba[][4])
{
   /* scale & bias */
   if (transferOps & IMAGE_SCALE_BIAS_BIT) {
      _mesa_scale_and_bias_rgba(n, rgba,
                                ctx->Pixel.RedScale, ctx->Pixel.GreenScale,
                                ctx->Pixel.BlueScale, ctx->Pixel.AlphaScale,
                                ctx->Pixel.RedBias, ctx->Pixel.GreenBias,
                                ctx->Pixel.BlueBias, ctx->Pixel.AlphaBias);
   }
   /* color map lookup */
   if (transferOps & IMAGE_MAP_COLOR_BIT) {
      _mesa_map_rgba( ctx, n, rgba );
   }
   /* GL_COLOR_TABLE lookup */
   if (transferOps & IMAGE_COLOR_TABLE_BIT) {
      _mesa_lookup_rgba_float(&ctx->ColorTable[COLORTABLE_PRECONVOLUTION], n, rgba);
   }
   /* convolution */
   if (transferOps & IMAGE_CONVOLUTION_BIT) {
      /* this has to be done in the calling code */
      _mesa_problem(ctx, "IMAGE_CONVOLUTION_BIT set in _mesa_apply_transfer_ops");
   }
   /* GL_POST_CONVOLUTION_RED/GREEN/BLUE/ALPHA_SCALE/BIAS */
   if (transferOps & IMAGE_POST_CONVOLUTION_SCALE_BIAS) {
      _mesa_scale_and_bias_rgba(n, rgba,
                                ctx->Pixel.PostConvolutionScale[RCOMP],
                                ctx->Pixel.PostConvolutionScale[GCOMP],
                                ctx->Pixel.PostConvolutionScale[BCOMP],
                                ctx->Pixel.PostConvolutionScale[ACOMP],
                                ctx->Pixel.PostConvolutionBias[RCOMP],
                                ctx->Pixel.PostConvolutionBias[GCOMP],
                                ctx->Pixel.PostConvolutionBias[BCOMP],
                                ctx->Pixel.PostConvolutionBias[ACOMP]);
   }
   /* GL_POST_CONVOLUTION_COLOR_TABLE lookup */
   if (transferOps & IMAGE_POST_CONVOLUTION_COLOR_TABLE_BIT) {
      _mesa_lookup_rgba_float(&ctx->ColorTable[COLORTABLE_POSTCONVOLUTION], n, rgba);
   }
   /* color matrix transform */
   if (transferOps & IMAGE_COLOR_MATRIX_BIT) {
      _mesa_transform_rgba(ctx, n, rgba);
   }
   /* GL_POST_COLOR_MATRIX_COLOR_TABLE lookup */
   if (transferOps & IMAGE_POST_COLOR_MATRIX_COLOR_TABLE_BIT) {
      _mesa_lookup_rgba_float(&ctx->ColorTable[COLORTABLE_POSTCOLORMATRIX], n, rgba);
   }
   /* update histogram count */
   if (transferOps & IMAGE_HISTOGRAM_BIT) {
      update_histogram(ctx, n, (CONST GLfloat (*)[4]) rgba);
   }
   /* update min/max values */
   if (transferOps & IMAGE_MIN_MAX_BIT) {
      update_minmax(ctx, n, (CONST GLfloat (*)[4]) rgba);
   }
   /* clamping to [0,1] */
   if (transferOps & IMAGE_CLAMP_BIT) {
      GLuint i;
      for (i = 0; i < n; i++) {
         rgba[i][RCOMP] = CLAMP(rgba[i][RCOMP], 0.0F, 1.0F);
         rgba[i][GCOMP] = CLAMP(rgba[i][GCOMP], 0.0F, 1.0F);
         rgba[i][BCOMP] = CLAMP(rgba[i][BCOMP], 0.0F, 1.0F);
         rgba[i][ACOMP] = CLAMP(rgba[i][ACOMP], 0.0F, 1.0F);
      }
   }
}


/*
 * Apply color index shift and offset to an array of pixels.
 */
static void
shift_and_offset_ci( const GLcontext *ctx, GLuint n, GLuint indexes[] )
{
   GLint shift = ctx->Pixel.IndexShift;
   GLint offset = ctx->Pixel.IndexOffset;
   GLuint i;
   if (shift > 0) {
      for (i=0;i<n;i++) {
         indexes[i] = (indexes[i] << shift) + offset;
      }
   }
   else if (shift < 0) {
      shift = -shift;
      for (i=0;i<n;i++) {
         indexes[i] = (indexes[i] >> shift) + offset;
      }
   }
   else {
      for (i=0;i<n;i++) {
         indexes[i] = indexes[i] + offset;
      }
   }
}



/**
 * Apply color index shift, offset and table lookup to an array
 * of color indexes;
 */
void
_mesa_apply_ci_transfer_ops(const GLcontext *ctx, GLbitfield transferOps,
                            GLuint n, GLuint indexes[])
{
   if (transferOps & IMAGE_SHIFT_OFFSET_BIT) {
      shift_and_offset_ci(ctx, n, indexes);
   }
   if (transferOps & IMAGE_MAP_COLOR_BIT) {
      const GLuint mask = ctx->PixelMaps.ItoI.Size - 1;
      GLuint i;
      for (i = 0; i < n; i++) {
         const GLuint j = indexes[i] & mask;
         indexes[i] = IROUND(ctx->PixelMaps.ItoI.Map[j]);
      }
   }
}


/**
 * Apply stencil index shift, offset and table lookup to an array
 * of stencil values.
 */
void
_mesa_apply_stencil_transfer_ops(const GLcontext *ctx, GLuint n,
                                 GLstencil stencil[])
{
   if (ctx->Pixel.IndexShift != 0 || ctx->Pixel.IndexOffset != 0) {
      const GLint offset = ctx->Pixel.IndexOffset;
      GLint shift = ctx->Pixel.IndexShift;
      GLuint i;
      if (shift > 0) {
         for (i = 0; i < n; i++) {
            stencil[i] = (stencil[i] << shift) + offset;
         }
      }
      else if (shift < 0) {
         shift = -shift;
         for (i = 0; i < n; i++) {
            stencil[i] = (stencil[i] >> shift) + offset;
         }
      }
      else {
         for (i = 0; i < n; i++) {
            stencil[i] = stencil[i] + offset;
         }
      }
   }
   if (ctx->Pixel.MapStencilFlag) {
      GLuint mask = ctx->PixelMaps.StoS.Size - 1;
      GLuint i;
      for (i = 0; i < n; i++) {
         stencil[i] = (GLstencil)ctx->PixelMaps.StoS.Map[ stencil[i] & mask ];
      }
   }
}


/**
 * Used to pack an array [][4] of RGBA float colors as specified
 * by the dstFormat, dstType and dstPacking.  Used by glReadPixels,
 * glGetConvolutionFilter(), etc.
 * Note: the rgba values will be modified by this function when any pixel
 * transfer ops are enabled.
 */
void
_mesa_pack_rgba_span_float(GLcontext *ctx, GLuint n, GLfloat rgba[][4],
                           GLenum dstFormat, GLenum dstType,
                           GLvoid *dstAddr,
                           const struct gl_pixelstore_attrib *dstPacking,
                           GLbitfield transferOps)
{
   GLfloat luminance[MAX_WIDTH];
   const GLint comps = _mesa_components_in_format(dstFormat);
   GLuint i;

   /* XXX
    * This test should probably go away.  Have the caller set/clear the
    * IMAGE_CLAMP_BIT as needed.
    */
   if (dstType != GL_FLOAT || ctx->Color.ClampReadColor == GL_TRUE) {
      /* need to clamp to [0, 1] */
      transferOps |= IMAGE_CLAMP_BIT;
   }

   if (transferOps) {
      _mesa_apply_rgba_transfer_ops(ctx, transferOps, n, rgba);
      if ((transferOps & IMAGE_MIN_MAX_BIT) && ctx->MinMax.Sink) {
         return;
      }
   }

   if (dstFormat == GL_LUMINANCE || dstFormat == GL_LUMINANCE_ALPHA) {
      /* compute luminance values */
      if (transferOps & IMAGE_CLAMP_BIT) {
         for (i = 0; i < n; i++) {
            GLfloat sum = rgba[i][RCOMP] + rgba[i][GCOMP] + rgba[i][BCOMP];
            luminance[i] = CLAMP(sum, 0.0F, 1.0F);
         }
      }
      else {
         for (i = 0; i < n; i++) {
            luminance[i] = rgba[i][RCOMP] + rgba[i][GCOMP] + rgba[i][BCOMP];
         }
      }
   }

   /*
    * Pack/store the pixels.  Ugh!  Lots of cases!!!
    */
   switch (dstType) {
      case GL_UNSIGNED_BYTE:
         {
            GLubyte *dst = (GLubyte *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UBYTE(rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UBYTE(rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UBYTE(luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_UBYTE(luminance[i]);
                     dst[i*2+1] = FLOAT_TO_UBYTE(rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                     dst[i*3+1] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_UBYTE(rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                     dst[i*4+1] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_UBYTE(rgba[i][BCOMP]);
                     dst[i*4+3] = FLOAT_TO_UBYTE(rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_UBYTE(rgba[i][BCOMP]);
                     dst[i*3+1] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_UBYTE(rgba[i][BCOMP]);
                     dst[i*4+1] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                     dst[i*4+3] = FLOAT_TO_UBYTE(rgba[i][ACOMP]);
                  }
                  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_UBYTE(rgba[i][ACOMP]);
                     dst[i*4+1] = FLOAT_TO_UBYTE(rgba[i][BCOMP]);
                     dst[i*4+2] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                     dst[i*4+3] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_UBYTE(rgba[i][RCOMP]);
                     dst[i*2+1] = FLOAT_TO_UBYTE(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_BYTE:
         {
            GLbyte *dst = (GLbyte *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_BYTE(rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_BYTE(rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_BYTE(luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_BYTE(luminance[i]);
                     dst[i*2+1] = FLOAT_TO_BYTE(rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                     dst[i*3+1] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_BYTE(rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                     dst[i*4+1] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_BYTE(rgba[i][BCOMP]);
                     dst[i*4+3] = FLOAT_TO_BYTE(rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_BYTE(rgba[i][BCOMP]);
                     dst[i*3+1] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_BYTE(rgba[i][BCOMP]);
                     dst[i*4+1] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                     dst[i*4+3] = FLOAT_TO_BYTE(rgba[i][ACOMP]);
                  }
		  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_BYTE(rgba[i][ACOMP]);
                     dst[i*4+1] = FLOAT_TO_BYTE(rgba[i][BCOMP]);
                     dst[i*4+2] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                     dst[i*4+3] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
                     dst[i*2+1] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_UNSIGNED_SHORT:
         {
            GLushort *dst = (GLushort *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     CLAMPED_FLOAT_TO_USHORT(dst[i], rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     CLAMPED_FLOAT_TO_USHORT(dst[i], rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     CLAMPED_FLOAT_TO_USHORT(dst[i], rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     CLAMPED_FLOAT_TO_USHORT(dst[i], rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     UNCLAMPED_FLOAT_TO_USHORT(dst[i], luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     UNCLAMPED_FLOAT_TO_USHORT(dst[i*2+0], luminance[i]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*2+1], rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     CLAMPED_FLOAT_TO_USHORT(dst[i*3+0], rgba[i][RCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*3+1], rgba[i][GCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*3+2], rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+0], rgba[i][RCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+1], rgba[i][GCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+2], rgba[i][BCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+3], rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     CLAMPED_FLOAT_TO_USHORT(dst[i*3+0], rgba[i][BCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*3+1], rgba[i][GCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*3+2], rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+0], rgba[i][BCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+1], rgba[i][GCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+2], rgba[i][RCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+3], rgba[i][ACOMP]);
                  }
                  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+0], rgba[i][ACOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+1], rgba[i][BCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+2], rgba[i][GCOMP]);
                     CLAMPED_FLOAT_TO_USHORT(dst[i*4+3], rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_USHORT(rgba[i][RCOMP]);
                     dst[i*2+1] = FLOAT_TO_USHORT(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_SHORT:
         {
            GLshort *dst = (GLshort *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_SHORT(rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_SHORT(rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_SHORT(luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_SHORT(luminance[i]);
                     dst[i*2+1] = FLOAT_TO_SHORT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                     dst[i*3+1] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_SHORT(rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                     dst[i*4+1] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_SHORT(rgba[i][BCOMP]);
                     dst[i*4+3] = FLOAT_TO_SHORT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_SHORT(rgba[i][BCOMP]);
                     dst[i*3+1] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_SHORT(rgba[i][BCOMP]);
                     dst[i*4+1] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                     dst[i*4+3] = FLOAT_TO_SHORT(rgba[i][ACOMP]);
                  }
		  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_SHORT(rgba[i][ACOMP]);
                     dst[i*4+1] = FLOAT_TO_SHORT(rgba[i][BCOMP]);
                     dst[i*4+2] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                     dst[i*4+3] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_SHORT(rgba[i][RCOMP]);
                     dst[i*2+1] = FLOAT_TO_SHORT(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_UNSIGNED_INT:
         {
            GLuint *dst = (GLuint *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UINT(rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UINT(rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_UINT(luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_UINT(luminance[i]);
                     dst[i*2+1] = FLOAT_TO_UINT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                     dst[i*3+1] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_UINT(rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                     dst[i*4+1] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_UINT(rgba[i][BCOMP]);
                     dst[i*4+3] = FLOAT_TO_UINT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_UINT(rgba[i][BCOMP]);
                     dst[i*3+1] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_UINT(rgba[i][BCOMP]);
                     dst[i*4+1] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                     dst[i*4+3] = FLOAT_TO_UINT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_UINT(rgba[i][ACOMP]);
                     dst[i*4+1] = FLOAT_TO_UINT(rgba[i][BCOMP]);
                     dst[i*4+2] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                     dst[i*4+3] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_UINT(rgba[i][RCOMP]);
                     dst[i*2+1] = FLOAT_TO_UINT(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_INT:
         {
            GLint *dst = (GLint *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_INT(rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_INT(rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_INT(rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_INT(rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = FLOAT_TO_INT(luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_INT(luminance[i]);
                     dst[i*2+1] = FLOAT_TO_INT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_INT(rgba[i][RCOMP]);
                     dst[i*3+1] = FLOAT_TO_INT(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_INT(rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_INT(rgba[i][RCOMP]);
                     dst[i*4+1] = FLOAT_TO_INT(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_INT(rgba[i][BCOMP]);
                     dst[i*4+3] = FLOAT_TO_INT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = FLOAT_TO_INT(rgba[i][BCOMP]);
                     dst[i*3+1] = FLOAT_TO_INT(rgba[i][GCOMP]);
                     dst[i*3+2] = FLOAT_TO_INT(rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_INT(rgba[i][BCOMP]);
                     dst[i*4+1] = FLOAT_TO_INT(rgba[i][GCOMP]);
                     dst[i*4+2] = FLOAT_TO_INT(rgba[i][RCOMP]);
                     dst[i*4+3] = FLOAT_TO_INT(rgba[i][ACOMP]);
                  }
                  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = FLOAT_TO_INT(rgba[i][ACOMP]);
                     dst[i*4+1] = FLOAT_TO_INT(rgba[i][BCOMP]);
                     dst[i*4+2] = FLOAT_TO_INT(rgba[i][GCOMP]);
                     dst[i*4+3] = FLOAT_TO_INT(rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = FLOAT_TO_INT(rgba[i][RCOMP]);
                     dst[i*2+1] = FLOAT_TO_INT(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_FLOAT:
         {
            GLfloat *dst = (GLfloat *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = rgba[i][RCOMP];
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = rgba[i][GCOMP];
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = rgba[i][BCOMP];
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = rgba[i][ACOMP];
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = luminance[i];
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = luminance[i];
                     dst[i*2+1] = rgba[i][ACOMP];
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = rgba[i][RCOMP];
                     dst[i*3+1] = rgba[i][GCOMP];
                     dst[i*3+2] = rgba[i][BCOMP];
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = rgba[i][RCOMP];
                     dst[i*4+1] = rgba[i][GCOMP];
                     dst[i*4+2] = rgba[i][BCOMP];
                     dst[i*4+3] = rgba[i][ACOMP];
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = rgba[i][BCOMP];
                     dst[i*3+1] = rgba[i][GCOMP];
                     dst[i*3+2] = rgba[i][RCOMP];
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = rgba[i][BCOMP];
                     dst[i*4+1] = rgba[i][GCOMP];
                     dst[i*4+2] = rgba[i][RCOMP];
                     dst[i*4+3] = rgba[i][ACOMP];
                  }
                  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = rgba[i][ACOMP];
                     dst[i*4+1] = rgba[i][BCOMP];
                     dst[i*4+2] = rgba[i][GCOMP];
                     dst[i*4+3] = rgba[i][RCOMP];
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = rgba[i][RCOMP];
                     dst[i*2+1] = rgba[i][GCOMP];
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_HALF_FLOAT_ARB:
         {
            GLhalfARB *dst = (GLhalfARB *) dstAddr;
            switch (dstFormat) {
               case GL_RED:
                  for (i=0;i<n;i++)
                     dst[i] = _mesa_float_to_half(rgba[i][RCOMP]);
                  break;
               case GL_GREEN:
                  for (i=0;i<n;i++)
                     dst[i] = _mesa_float_to_half(rgba[i][GCOMP]);
                  break;
               case GL_BLUE:
                  for (i=0;i<n;i++)
                     dst[i] = _mesa_float_to_half(rgba[i][BCOMP]);
                  break;
               case GL_ALPHA:
                  for (i=0;i<n;i++)
                     dst[i] = _mesa_float_to_half(rgba[i][ACOMP]);
                  break;
               case GL_LUMINANCE:
                  for (i=0;i<n;i++)
                     dst[i] = _mesa_float_to_half(luminance[i]);
                  break;
               case GL_LUMINANCE_ALPHA:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = _mesa_float_to_half(luminance[i]);
                     dst[i*2+1] = _mesa_float_to_half(rgba[i][ACOMP]);
                  }
                  break;
               case GL_RGB:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = _mesa_float_to_half(rgba[i][RCOMP]);
                     dst[i*3+1] = _mesa_float_to_half(rgba[i][GCOMP]);
                     dst[i*3+2] = _mesa_float_to_half(rgba[i][BCOMP]);
                  }
                  break;
               case GL_RGBA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = _mesa_float_to_half(rgba[i][RCOMP]);
                     dst[i*4+1] = _mesa_float_to_half(rgba[i][GCOMP]);
                     dst[i*4+2] = _mesa_float_to_half(rgba[i][BCOMP]);
                     dst[i*4+3] = _mesa_float_to_half(rgba[i][ACOMP]);
                  }
                  break;
               case GL_BGR:
                  for (i=0;i<n;i++) {
                     dst[i*3+0] = _mesa_float_to_half(rgba[i][BCOMP]);
                     dst[i*3+1] = _mesa_float_to_half(rgba[i][GCOMP]);
                     dst[i*3+2] = _mesa_float_to_half(rgba[i][RCOMP]);
                  }
                  break;
               case GL_BGRA:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = _mesa_float_to_half(rgba[i][BCOMP]);
                     dst[i*4+1] = _mesa_float_to_half(rgba[i][GCOMP]);
                     dst[i*4+2] = _mesa_float_to_half(rgba[i][RCOMP]);
                     dst[i*4+3] = _mesa_float_to_half(rgba[i][ACOMP]);
                  }
                  break;
               case GL_ABGR_EXT:
                  for (i=0;i<n;i++) {
                     dst[i*4+0] = _mesa_float_to_half(rgba[i][ACOMP]);
                     dst[i*4+1] = _mesa_float_to_half(rgba[i][BCOMP]);
                     dst[i*4+2] = _mesa_float_to_half(rgba[i][GCOMP]);
                     dst[i*4+3] = _mesa_float_to_half(rgba[i][RCOMP]);
                  }
                  break;
               case GL_DUDV_ATI:
               case GL_DU8DV8_ATI:
                  for (i=0;i<n;i++) {
                     dst[i*2+0] = _mesa_float_to_half(rgba[i][RCOMP]);
                     dst[i*2+1] = _mesa_float_to_half(rgba[i][GCOMP]);
                  }
                  break;
               default:
                  _mesa_problem(ctx, "bad format in _mesa_pack_rgba_span\n");
            }
         }
         break;
      case GL_UNSIGNED_BYTE_3_3_2:
         if (dstFormat == GL_RGB) {
            GLubyte *dst = (GLubyte *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 7.0F) << 5)
                      | (IROUND(rgba[i][GCOMP] * 7.0F) << 2)
                      | (IROUND(rgba[i][BCOMP] * 3.0F)     );
            }
         }
         break;
      case GL_UNSIGNED_BYTE_2_3_3_REV:
         if (dstFormat == GL_RGB) {
            GLubyte *dst = (GLubyte *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 7.0F)     )
                      | (IROUND(rgba[i][GCOMP] * 7.0F) << 3)
                      | (IROUND(rgba[i][BCOMP] * 3.0F) << 6);
            }
         }
         break;
      case GL_UNSIGNED_SHORT_5_6_5:
         if (dstFormat == GL_RGB) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 31.0F) << 11)
                      | (IROUND(rgba[i][GCOMP] * 63.0F) <<  5)
                      | (IROUND(rgba[i][BCOMP] * 31.0F)      );
            }
         }
         break;
      case GL_UNSIGNED_SHORT_5_6_5_REV:
         if (dstFormat == GL_RGB) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 31.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 63.0F) <<  5)
                      | (IROUND(rgba[i][BCOMP] * 31.0F) << 11);
            }
         }
         break;
      case GL_UNSIGNED_SHORT_4_4_4_4:
         if (dstFormat == GL_RGBA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 15.0F) << 12)
                      | (IROUND(rgba[i][GCOMP] * 15.0F) <<  8)
                      | (IROUND(rgba[i][BCOMP] * 15.0F) <<  4)
                      | (IROUND(rgba[i][ACOMP] * 15.0F)      );
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 15.0F) << 12)
                      | (IROUND(rgba[i][GCOMP] * 15.0F) <<  8)
                      | (IROUND(rgba[i][RCOMP] * 15.0F) <<  4)
                      | (IROUND(rgba[i][ACOMP] * 15.0F)      );
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 15.0F) << 12)
                      | (IROUND(rgba[i][BCOMP] * 15.0F) <<  8)
                      | (IROUND(rgba[i][GCOMP] * 15.0F) <<  4)
                      | (IROUND(rgba[i][RCOMP] * 15.0F)      );
            }
         }
         break;
      case GL_UNSIGNED_SHORT_4_4_4_4_REV:
         if (dstFormat == GL_RGBA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 15.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 15.0F) <<  4)
                      | (IROUND(rgba[i][BCOMP] * 15.0F) <<  8)
                      | (IROUND(rgba[i][ACOMP] * 15.0F) << 12);
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 15.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 15.0F) <<  4)
                      | (IROUND(rgba[i][RCOMP] * 15.0F) <<  8)
                      | (IROUND(rgba[i][ACOMP] * 15.0F) << 12);
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 15.0F)      )
                      | (IROUND(rgba[i][BCOMP] * 15.0F) <<  4)
                      | (IROUND(rgba[i][GCOMP] * 15.0F) <<  8)
                      | (IROUND(rgba[i][RCOMP] * 15.0F) << 12);
            }
         }
         break;
      case GL_UNSIGNED_SHORT_5_5_5_1:
         if (dstFormat == GL_RGBA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 31.0F) << 11)
                      | (IROUND(rgba[i][GCOMP] * 31.0F) <<  6)
                      | (IROUND(rgba[i][BCOMP] * 31.0F) <<  1)
                      | (IROUND(rgba[i][ACOMP] *  1.0F)      );
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 31.0F) << 11)
                      | (IROUND(rgba[i][GCOMP] * 31.0F) <<  6)
                      | (IROUND(rgba[i][RCOMP] * 31.0F) <<  1)
                      | (IROUND(rgba[i][ACOMP] *  1.0F)      );
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 31.0F) << 11)
                      | (IROUND(rgba[i][BCOMP] * 31.0F) <<  6)
                      | (IROUND(rgba[i][GCOMP] * 31.0F) <<  1)
                      | (IROUND(rgba[i][RCOMP] *  1.0F)      );
            }
         }
         break;
      case GL_UNSIGNED_SHORT_1_5_5_5_REV:
         if (dstFormat == GL_RGBA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 31.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 31.0F) <<  5)
                      | (IROUND(rgba[i][BCOMP] * 31.0F) << 10)
                      | (IROUND(rgba[i][ACOMP] *  1.0F) << 15);
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 31.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 31.0F) <<  5)
                      | (IROUND(rgba[i][RCOMP] * 31.0F) << 10)
                      | (IROUND(rgba[i][ACOMP] *  1.0F) << 15);
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLushort *dst = (GLushort *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 31.0F)      )
                      | (IROUND(rgba[i][BCOMP] * 31.0F) <<  5)
                      | (IROUND(rgba[i][GCOMP] * 31.0F) << 10)
                      | (IROUND(rgba[i][RCOMP] *  1.0F) << 15);
            }
         }
         break;
      case GL_UNSIGNED_INT_8_8_8_8:
         if (dstFormat == GL_RGBA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 255.F) << 24)
                      | (IROUND(rgba[i][GCOMP] * 255.F) << 16)
                      | (IROUND(rgba[i][BCOMP] * 255.F) <<  8)
                      | (IROUND(rgba[i][ACOMP] * 255.F)      );
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 255.F) << 24)
                      | (IROUND(rgba[i][GCOMP] * 255.F) << 16)
                      | (IROUND(rgba[i][RCOMP] * 255.F) <<  8)
                      | (IROUND(rgba[i][ACOMP] * 255.F)      );
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 255.F) << 24)
                      | (IROUND(rgba[i][BCOMP] * 255.F) << 16)
                      | (IROUND(rgba[i][GCOMP] * 255.F) <<  8)
                      | (IROUND(rgba[i][RCOMP] * 255.F)      );
            }
         }
         break;
      case GL_UNSIGNED_INT_8_8_8_8_REV:
         if (dstFormat == GL_RGBA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 255.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 255.0F) <<  8)
                      | (IROUND(rgba[i][BCOMP] * 255.0F) << 16)
                      | (IROUND(rgba[i][ACOMP] * 255.0F) << 24);
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 255.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 255.0F) <<  8)
                      | (IROUND(rgba[i][RCOMP] * 255.0F) << 16)
                      | (IROUND(rgba[i][ACOMP] * 255.0F) << 24);
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 255.0F)      )
                      | (IROUND(rgba[i][BCOMP] * 255.0F) <<  8)
                      | (IROUND(rgba[i][GCOMP] * 255.0F) << 16)
                      | (IROUND(rgba[i][RCOMP] * 255.0F) << 24);
            }
         }
         break;
      case GL_UNSIGNED_INT_10_10_10_2:
         if (dstFormat == GL_RGBA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 1023.0F) << 22)
                      | (IROUND(rgba[i][GCOMP] * 1023.0F) << 12)
                      | (IROUND(rgba[i][BCOMP] * 1023.0F) <<  2)
                      | (IROUND(rgba[i][ACOMP] *    3.0F)      );
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 1023.0F) << 22)
                      | (IROUND(rgba[i][GCOMP] * 1023.0F) << 12)
                      | (IROUND(rgba[i][RCOMP] * 1023.0F) <<  2)
                      | (IROUND(rgba[i][ACOMP] *    3.0F)      );
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 1023.0F) << 22)
                      | (IROUND(rgba[i][BCOMP] * 1023.0F) << 12)
                      | (IROUND(rgba[i][GCOMP] * 1023.0F) <<  2)
                      | (IROUND(rgba[i][RCOMP] *    3.0F)      );
            }
         }
         break;
      case GL_UNSIGNED_INT_2_10_10_10_REV:
         if (dstFormat == GL_RGBA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][RCOMP] * 1023.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 1023.0F) << 10)
                      | (IROUND(rgba[i][BCOMP] * 1023.0F) << 20)
                      | (IROUND(rgba[i][ACOMP] *    3.0F) << 30);
            }
         }
         else if (dstFormat == GL_BGRA) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][BCOMP] * 1023.0F)      )
                      | (IROUND(rgba[i][GCOMP] * 1023.0F) << 10)
                      | (IROUND(rgba[i][RCOMP] * 1023.0F) << 20)
                      | (IROUND(rgba[i][ACOMP] *    3.0F) << 30);
            }
         }
         else if (dstFormat == GL_ABGR_EXT) {
            GLuint *dst = (GLuint *) dstAddr;
            for (i=0;i<n;i++) {
               dst[i] = (IROUND(rgba[i][ACOMP] * 1023.0F)      )
                      | (IROUND(rgba[i][BCOMP] * 1023.0F) << 10)
                      | (IROUND(rgba[i][GCOMP] * 1023.0F) << 20)
                      | (IROUND(rgba[i][RCOMP] *    3.0F) << 30);
            }
         }
         break;
      default:
         _mesa_problem(ctx, "bad type in _mesa_pack_rgba_span_float");
         return;
   }

   if (dstPacking->SwapBytes) {
      GLint swapSize = _mesa_sizeof_packed_type(dstType);
      if (swapSize == 2) {
         if (dstPacking->SwapBytes) {
            _mesa_swap2((GLushort *) dstAddr, n * comps);
         }
      }
      else if (swapSize == 4) {
         if (dstPacking->SwapBytes) {
            _mesa_swap4((GLuint *) dstAddr, n * comps);
         }
      }
   }
}


#define SWAP2BYTE(VALUE)			\
   {						\
      GLubyte *bytes = (GLubyte *) &(VALUE);	\
      GLubyte tmp = bytes[0];			\
      bytes[0] = bytes[1];			\
      bytes[1] = tmp;				\
   }

#define SWAP4BYTE(VALUE)			\
   {						\
      GLubyte *bytes = (GLubyte *) &(VALUE);	\
      GLubyte tmp = bytes[0];			\
      bytes[0] = bytes[3];			\
      bytes[3] = tmp;				\
      tmp = bytes[1];				\
      bytes[1] = bytes[2];			\
      bytes[2] = tmp;				\
   }


static void
extract_uint_indexes(GLuint n, GLuint indexes[],
                     GLenum srcFormat, GLenum srcType, const GLvoid *src,
                     const struct gl_pixelstore_attrib *unpack )
{
   ASSERT(srcFormat == GL_COLOR_INDEX || srcFormat == GL_STENCIL_INDEX);

   ASSERT(srcType == GL_BITMAP ||
          srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_UNSIGNED_INT_24_8_EXT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT);

   switch (srcType) {
      case GL_BITMAP:
         {
            GLubyte *ubsrc = (GLubyte *) src;
            if (unpack->LsbFirst) {
               GLubyte mask = 1 << (unpack->SkipPixels & 0x7);
               GLuint i;
               for (i = 0; i < n; i++) {
                  indexes[i] = (*ubsrc & mask) ? 1 : 0;
                  if (mask == 128) {
                     mask = 1;
                     ubsrc++;
                  }
                  else {
                     mask = mask << 1;
                  }
               }
            }
            else {
               GLubyte mask = 128 >> (unpack->SkipPixels & 0x7);
               GLuint i;
               for (i = 0; i < n; i++) {
                  indexes[i] = (*ubsrc & mask) ? 1 : 0;
                  if (mask == 1) {
                     mask = 128;
                     ubsrc++;
                  }
                  else {
                     mask = mask >> 1;
                  }
               }
            }
         }
         break;
      case GL_UNSIGNED_BYTE:
         {
            GLuint i;
            const GLubyte *s = (const GLubyte *) src;
            for (i = 0; i < n; i++)
               indexes[i] = s[i];
         }
         break;
      case GL_BYTE:
         {
            GLuint i;
            const GLbyte *s = (const GLbyte *) src;
            for (i = 0; i < n; i++)
               indexes[i] = s[i];
         }
         break;
      case GL_UNSIGNED_SHORT:
         {
            GLuint i;
            const GLushort *s = (const GLushort *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLushort value = s[i];
                  SWAP2BYTE(value);
                  indexes[i] = value;
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = s[i];
            }
         }
         break;
      case GL_SHORT:
         {
            GLuint i;
            const GLshort *s = (const GLshort *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLshort value = s[i];
                  SWAP2BYTE(value);
                  indexes[i] = value;
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = s[i];
            }
         }
         break;
      case GL_UNSIGNED_INT:
         {
            GLuint i;
            const GLuint *s = (const GLuint *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLuint value = s[i];
                  SWAP4BYTE(value);
                  indexes[i] = value;
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = s[i];
            }
         }
         break;
      case GL_INT:
         {
            GLuint i;
            const GLint *s = (const GLint *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLint value = s[i];
                  SWAP4BYTE(value);
                  indexes[i] = value;
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = s[i];
            }
         }
         break;
      case GL_FLOAT:
         {
            GLuint i;
            const GLfloat *s = (const GLfloat *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLfloat value = s[i];
                  SWAP4BYTE(value);
                  indexes[i] = (GLuint) value;
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = (GLuint) s[i];
            }
         }
         break;
      case GL_HALF_FLOAT_ARB:
         {
            GLuint i;
            const GLhalfARB *s = (const GLhalfARB *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLhalfARB value = s[i];
                  SWAP2BYTE(value);
                  indexes[i] = (GLuint) _mesa_half_to_float(value);
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = (GLuint) _mesa_half_to_float(s[i]);
            }
         }
         break;
      case GL_UNSIGNED_INT_24_8_EXT:
         {
            GLuint i;
            const GLuint *s = (const GLuint *) src;
            if (unpack->SwapBytes) {
               for (i = 0; i < n; i++) {
                  GLuint value = s[i];
                  SWAP4BYTE(value);
                  indexes[i] = value & 0xff;  /* lower 8 bits */
               }
            }
            else {
               for (i = 0; i < n; i++)
                  indexes[i] = s[i] & 0xfff;  /* lower 8 bits */
            }
         }
         break;

      default:
         _mesa_problem(NULL, "bad srcType in extract_uint_indexes");
         return;
   }
}


/*
 * This function extracts floating point RGBA values from arbitrary
 * image data.  srcFormat and srcType are the format and type parameters
 * passed to glDrawPixels, glTexImage[123]D, glTexSubImage[123]D, etc.
 *
 * Refering to section 3.6.4 of the OpenGL 1.2 spec, this function
 * implements the "Conversion to floating point", "Conversion to RGB",
 * and "Final Expansion to RGBA" operations.
 *
 * Args:  n - number of pixels
 *        rgba - output colors
 *        srcFormat - format of incoming data
 *        srcType - data type of incoming data
 *        src - source data pointer
 *        swapBytes - perform byteswapping of incoming data?
 */
static void
extract_float_rgba(GLuint n, GLfloat rgba[][4],
                   GLenum srcFormat, GLenum srcType, const GLvoid *src,
                   GLboolean swapBytes)
{
   GLint redIndex, greenIndex, blueIndex, alphaIndex;
   GLint stride;
   GLint rComp, bComp, gComp, aComp;

   ASSERT(srcFormat == GL_RED ||
          srcFormat == GL_GREEN ||
          srcFormat == GL_BLUE ||
          srcFormat == GL_ALPHA ||
          srcFormat == GL_LUMINANCE ||
          srcFormat == GL_LUMINANCE_ALPHA ||
          srcFormat == GL_INTENSITY ||
          srcFormat == GL_RGB ||
          srcFormat == GL_BGR ||
          srcFormat == GL_RGBA ||
          srcFormat == GL_BGRA ||
          srcFormat == GL_ABGR_EXT ||
          srcFormat == GL_DUDV_ATI);

   ASSERT(srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT ||
          srcType == GL_UNSIGNED_BYTE_3_3_2 ||
          srcType == GL_UNSIGNED_BYTE_2_3_3_REV ||
          srcType == GL_UNSIGNED_SHORT_5_6_5 ||
          srcType == GL_UNSIGNED_SHORT_5_6_5_REV ||
          srcType == GL_UNSIGNED_SHORT_4_4_4_4 ||
          srcType == GL_UNSIGNED_SHORT_4_4_4_4_REV ||
          srcType == GL_UNSIGNED_SHORT_5_5_5_1 ||
          srcType == GL_UNSIGNED_SHORT_1_5_5_5_REV ||
          srcType == GL_UNSIGNED_INT_8_8_8_8 ||
          srcType == GL_UNSIGNED_INT_8_8_8_8_REV ||
          srcType == GL_UNSIGNED_INT_10_10_10_2 ||
          srcType == GL_UNSIGNED_INT_2_10_10_10_REV);

   rComp = gComp = bComp = aComp = -1;

   switch (srcFormat) {
      case GL_RED:
         redIndex = 0;
         greenIndex = blueIndex = alphaIndex = -1;
         stride = 1;
         break;
      case GL_GREEN:
         greenIndex = 0;
         redIndex = blueIndex = alphaIndex = -1;
         stride = 1;
         break;
      case GL_BLUE:
         blueIndex = 0;
         redIndex = greenIndex = alphaIndex = -1;
         stride = 1;
         break;
      case GL_ALPHA:
         redIndex = greenIndex = blueIndex = -1;
         alphaIndex = 0;
         stride = 1;
         break;
      case GL_LUMINANCE:
         redIndex = greenIndex = blueIndex = 0;
         alphaIndex = -1;
         stride = 1;
         break;
      case GL_LUMINANCE_ALPHA:
         redIndex = greenIndex = blueIndex = 0;
         alphaIndex = 1;
         stride = 2;
         break;
      case GL_INTENSITY:
         redIndex = greenIndex = blueIndex = alphaIndex = 0;
         stride = 1;
         break;
      case GL_RGB:
         redIndex = 0;
         greenIndex = 1;
         blueIndex = 2;
         alphaIndex = -1;
         rComp = 0;
         gComp = 1;
         bComp = 2;
         aComp = 3;
         stride = 3;
         break;
      case GL_BGR:
         redIndex = 2;
         greenIndex = 1;
         blueIndex = 0;
         alphaIndex = -1;
         rComp = 2;
         gComp = 1;
         bComp = 0;
         aComp = 3;
         stride = 3;
         break;
      case GL_RGBA:
         redIndex = 0;
         greenIndex = 1;
         blueIndex = 2;
         alphaIndex = 3;
         rComp = 0;
         gComp = 1;
         bComp = 2;
         aComp = 3;
         stride = 4;
         break;
      case GL_BGRA:
         redIndex = 2;
         greenIndex = 1;
         blueIndex = 0;
         alphaIndex = 3;
         rComp = 2;
         gComp = 1;
         bComp = 0;
         aComp = 3;
         stride = 4;
         break;
      case GL_ABGR_EXT:
         redIndex = 3;
         greenIndex = 2;
         blueIndex = 1;
         alphaIndex = 0;
         rComp = 3;
         gComp = 2;
         bComp = 1;
         aComp = 0;
         stride = 4;
         break;
      case GL_DUDV_ATI:
         redIndex = 0;
         greenIndex = 1;
         blueIndex = -1;
         alphaIndex = -1;
         stride = 2;
         break;
      default:
         _mesa_problem(NULL, "bad srcFormat in extract float data");
         return;
   }


#define PROCESS(INDEX, CHANNEL, DEFAULT, TYPE, CONVERSION)		\
   if ((INDEX) < 0) {							\
      GLuint i;								\
      for (i = 0; i < n; i++) {						\
         rgba[i][CHANNEL] = DEFAULT;					\
      }									\
   }									\
   else if (swapBytes) {						\
      const TYPE *s = (const TYPE *) src;				\
      GLuint i;								\
      for (i = 0; i < n; i++) {						\
         TYPE value = s[INDEX];						\
         if (sizeof(TYPE) == 2) {					\
            SWAP2BYTE(value);						\
         }								\
         else if (sizeof(TYPE) == 4) {					\
            SWAP4BYTE(value);						\
         }								\
         rgba[i][CHANNEL] = (GLfloat) CONVERSION(value);		\
         s += stride;							\
      }									\
   }									\
   else {								\
      const TYPE *s = (const TYPE *) src;				\
      GLuint i;								\
      for (i = 0; i < n; i++) {						\
         rgba[i][CHANNEL] = (GLfloat) CONVERSION(s[INDEX]);		\
         s += stride;							\
      }									\
   }

   switch (srcType) {
      case GL_UNSIGNED_BYTE:
         PROCESS(redIndex,   RCOMP, 0.0F, GLubyte, UBYTE_TO_FLOAT);
         PROCESS(greenIndex, GCOMP, 0.0F, GLubyte, UBYTE_TO_FLOAT);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLubyte, UBYTE_TO_FLOAT);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLubyte, UBYTE_TO_FLOAT);
         break;
      case GL_BYTE:
         PROCESS(redIndex,   RCOMP, 0.0F, GLbyte, BYTE_TO_FLOAT);
         PROCESS(greenIndex, GCOMP, 0.0F, GLbyte, BYTE_TO_FLOAT);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLbyte, BYTE_TO_FLOAT);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLbyte, BYTE_TO_FLOAT);
         break;
      case GL_UNSIGNED_SHORT:
         PROCESS(redIndex,   RCOMP, 0.0F, GLushort, USHORT_TO_FLOAT);
         PROCESS(greenIndex, GCOMP, 0.0F, GLushort, USHORT_TO_FLOAT);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLushort, USHORT_TO_FLOAT);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLushort, USHORT_TO_FLOAT);
         break;
      case GL_SHORT:
         PROCESS(redIndex,   RCOMP, 0.0F, GLshort, SHORT_TO_FLOAT);
         PROCESS(greenIndex, GCOMP, 0.0F, GLshort, SHORT_TO_FLOAT);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLshort, SHORT_TO_FLOAT);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLshort, SHORT_TO_FLOAT);
         break;
      case GL_UNSIGNED_INT:
         PROCESS(redIndex,   RCOMP, 0.0F, GLuint, UINT_TO_FLOAT);
         PROCESS(greenIndex, GCOMP, 0.0F, GLuint, UINT_TO_FLOAT);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLuint, UINT_TO_FLOAT);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLuint, UINT_TO_FLOAT);
         break;
      case GL_INT:
         PROCESS(redIndex,   RCOMP, 0.0F, GLint, INT_TO_FLOAT);
         PROCESS(greenIndex, GCOMP, 0.0F, GLint, INT_TO_FLOAT);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLint, INT_TO_FLOAT);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLint, INT_TO_FLOAT);
         break;
      case GL_FLOAT:
         PROCESS(redIndex,   RCOMP, 0.0F, GLfloat, (GLfloat));
         PROCESS(greenIndex, GCOMP, 0.0F, GLfloat, (GLfloat));
         PROCESS(blueIndex,  BCOMP, 0.0F, GLfloat, (GLfloat));
         PROCESS(alphaIndex, ACOMP, 1.0F, GLfloat, (GLfloat));
         break;
      case GL_HALF_FLOAT_ARB:
         PROCESS(redIndex,   RCOMP, 0.0F, GLhalfARB, _mesa_half_to_float);
         PROCESS(greenIndex, GCOMP, 0.0F, GLhalfARB, _mesa_half_to_float);
         PROCESS(blueIndex,  BCOMP, 0.0F, GLhalfARB, _mesa_half_to_float);
         PROCESS(alphaIndex, ACOMP, 1.0F, GLhalfARB, _mesa_half_to_float);
         break;
      case GL_UNSIGNED_BYTE_3_3_2:
         {
            const GLubyte *ubsrc = (const GLubyte *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLubyte p = ubsrc[i];
               rgba[i][rComp] = ((p >> 5)      ) * (1.0F / 7.0F);
               rgba[i][gComp] = ((p >> 2) & 0x7) * (1.0F / 7.0F);
               rgba[i][bComp] = ((p     ) & 0x3) * (1.0F / 3.0F);
               rgba[i][aComp] = 1.0F;
            }
         }
         break;
      case GL_UNSIGNED_BYTE_2_3_3_REV:
         {
            const GLubyte *ubsrc = (const GLubyte *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLubyte p = ubsrc[i];
               rgba[i][rComp] = ((p     ) & 0x7) * (1.0F / 7.0F);
               rgba[i][gComp] = ((p >> 3) & 0x7) * (1.0F / 7.0F);
               rgba[i][bComp] = ((p >> 6)      ) * (1.0F / 3.0F);
               rgba[i][aComp] = 1.0F;
            }
         }
         break;
      case GL_UNSIGNED_SHORT_5_6_5:
         if (swapBytes) {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               SWAP2BYTE(p);
               rgba[i][rComp] = ((p >> 11)       ) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  5) & 0x3f) * (1.0F / 63.0F);
               rgba[i][bComp] = ((p      ) & 0x1f) * (1.0F / 31.0F);
               rgba[i][aComp] = 1.0F;
            }
         }
         else {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               rgba[i][rComp] = ((p >> 11)       ) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  5) & 0x3f) * (1.0F / 63.0F);
               rgba[i][bComp] = ((p      ) & 0x1f) * (1.0F / 31.0F);
               rgba[i][aComp] = 1.0F;
            }
         }
         break;
      case GL_UNSIGNED_SHORT_5_6_5_REV:
         if (swapBytes) {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               SWAP2BYTE(p);
               rgba[i][rComp] = ((p      ) & 0x1f) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  5) & 0x3f) * (1.0F / 63.0F);
               rgba[i][bComp] = ((p >> 11)       ) * (1.0F / 31.0F);
               rgba[i][aComp] = 1.0F;
            }
         }
         else {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               rgba[i][rComp] = ((p      ) & 0x1f) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  5) & 0x3f) * (1.0F / 63.0F);
               rgba[i][bComp] = ((p >> 11)       ) * (1.0F / 31.0F);
               rgba[i][aComp] = 1.0F;
            }
         }
         break;
      case GL_UNSIGNED_SHORT_4_4_4_4:
         if (swapBytes) {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               SWAP2BYTE(p);
               rgba[i][rComp] = ((p >> 12)      ) * (1.0F / 15.0F);
               rgba[i][gComp] = ((p >>  8) & 0xf) * (1.0F / 15.0F);
               rgba[i][bComp] = ((p >>  4) & 0xf) * (1.0F / 15.0F);
               rgba[i][aComp] = ((p      ) & 0xf) * (1.0F / 15.0F);
            }
         }
         else {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               rgba[i][rComp] = ((p >> 12)      ) * (1.0F / 15.0F);
               rgba[i][gComp] = ((p >>  8) & 0xf) * (1.0F / 15.0F);
               rgba[i][bComp] = ((p >>  4) & 0xf) * (1.0F / 15.0F);
               rgba[i][aComp] = ((p      ) & 0xf) * (1.0F / 15.0F);
            }
         }
         break;
      case GL_UNSIGNED_SHORT_4_4_4_4_REV:
         if (swapBytes) {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               SWAP2BYTE(p);
               rgba[i][rComp] = ((p      ) & 0xf) * (1.0F / 15.0F);
               rgba[i][gComp] = ((p >>  4) & 0xf) * (1.0F / 15.0F);
               rgba[i][bComp] = ((p >>  8) & 0xf) * (1.0F / 15.0F);
               rgba[i][aComp] = ((p >> 12)      ) * (1.0F / 15.0F);
            }
         }
         else {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               rgba[i][rComp] = ((p      ) & 0xf) * (1.0F / 15.0F);
               rgba[i][gComp] = ((p >>  4) & 0xf) * (1.0F / 15.0F);
               rgba[i][bComp] = ((p >>  8) & 0xf) * (1.0F / 15.0F);
               rgba[i][aComp] = ((p >> 12)      ) * (1.0F / 15.0F);
            }
         }
         break;
      case GL_UNSIGNED_SHORT_5_5_5_1:
         if (swapBytes) {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               SWAP2BYTE(p);
               rgba[i][rComp] = ((p >> 11)       ) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  6) & 0x1f) * (1.0F / 31.0F);
               rgba[i][bComp] = ((p >>  1) & 0x1f) * (1.0F / 31.0F);
               rgba[i][aComp] = ((p      ) & 0x1)  * (1.0F /  1.0F);
            }
         }
         else {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               rgba[i][rComp] = ((p >> 11)       ) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  6) & 0x1f) * (1.0F / 31.0F);
               rgba[i][bComp] = ((p >>  1) & 0x1f) * (1.0F / 31.0F);
               rgba[i][aComp] = ((p      ) & 0x1)  * (1.0F /  1.0F);
            }
         }
         break;
      case GL_UNSIGNED_SHORT_1_5_5_5_REV:
         if (swapBytes) {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               SWAP2BYTE(p);
               rgba[i][rComp] = ((p      ) & 0x1f) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  5) & 0x1f) * (1.0F / 31.0F);
               rgba[i][bComp] = ((p >> 10) & 0x1f) * (1.0F / 31.0F);
               rgba[i][aComp] = ((p >> 15)       ) * (1.0F /  1.0F);
            }
         }
         else {
            const GLushort *ussrc = (const GLushort *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLushort p = ussrc[i];
               rgba[i][rComp] = ((p      ) & 0x1f) * (1.0F / 31.0F);
               rgba[i][gComp] = ((p >>  5) & 0x1f) * (1.0F / 31.0F);
               rgba[i][bComp] = ((p >> 10) & 0x1f) * (1.0F / 31.0F);
               rgba[i][aComp] = ((p >> 15)       ) * (1.0F /  1.0F);
            }
         }
         break;
      case GL_UNSIGNED_INT_8_8_8_8:
         if (swapBytes) {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               rgba[i][rComp] = UBYTE_TO_FLOAT((p      ) & 0xff);
               rgba[i][gComp] = UBYTE_TO_FLOAT((p >>  8) & 0xff);
               rgba[i][bComp] = UBYTE_TO_FLOAT((p >> 16) & 0xff);
               rgba[i][aComp] = UBYTE_TO_FLOAT((p >> 24)       );
            }
         }
         else {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               rgba[i][rComp] = UBYTE_TO_FLOAT((p >> 24)       );
               rgba[i][gComp] = UBYTE_TO_FLOAT((p >> 16) & 0xff);
               rgba[i][bComp] = UBYTE_TO_FLOAT((p >>  8) & 0xff);
               rgba[i][aComp] = UBYTE_TO_FLOAT((p      ) & 0xff);
            }
         }
         break;
      case GL_UNSIGNED_INT_8_8_8_8_REV:
         if (swapBytes) {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               rgba[i][rComp] = UBYTE_TO_FLOAT((p >> 24)       );
               rgba[i][gComp] = UBYTE_TO_FLOAT((p >> 16) & 0xff);
               rgba[i][bComp] = UBYTE_TO_FLOAT((p >>  8) & 0xff);
               rgba[i][aComp] = UBYTE_TO_FLOAT((p      ) & 0xff);
            }
         }
         else {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               rgba[i][rComp] = UBYTE_TO_FLOAT((p      ) & 0xff);
               rgba[i][gComp] = UBYTE_TO_FLOAT((p >>  8) & 0xff);
               rgba[i][bComp] = UBYTE_TO_FLOAT((p >> 16) & 0xff);
               rgba[i][aComp] = UBYTE_TO_FLOAT((p >> 24)       );
            }
         }
         break;
      case GL_UNSIGNED_INT_10_10_10_2:
         if (swapBytes) {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               SWAP4BYTE(p);
               rgba[i][rComp] = ((p >> 22)        ) * (1.0F / 1023.0F);
               rgba[i][gComp] = ((p >> 12) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][bComp] = ((p >>  2) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][aComp] = ((p      ) & 0x3  ) * (1.0F /    3.0F);
            }
         }
         else {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               rgba[i][rComp] = ((p >> 22)        ) * (1.0F / 1023.0F);
               rgba[i][gComp] = ((p >> 12) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][bComp] = ((p >>  2) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][aComp] = ((p      ) & 0x3  ) * (1.0F /    3.0F);
            }
         }
         break;
      case GL_UNSIGNED_INT_2_10_10_10_REV:
         if (swapBytes) {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               SWAP4BYTE(p);
               rgba[i][rComp] = ((p      ) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][gComp] = ((p >> 10) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][bComp] = ((p >> 20) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][aComp] = ((p >> 30)        ) * (1.0F /    3.0F);
            }
         }
         else {
            const GLuint *uisrc = (const GLuint *) src;
            GLuint i;
            for (i = 0; i < n; i ++) {
               GLuint p = uisrc[i];
               rgba[i][rComp] = ((p      ) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][gComp] = ((p >> 10) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][bComp] = ((p >> 20) & 0x3ff) * (1.0F / 1023.0F);
               rgba[i][aComp] = ((p >> 30)        ) * (1.0F /    3.0F);
            }
         }
         break;
      default:
         _mesa_problem(NULL, "bad srcType in extract float data");
         break;
   }
}


/*
 * Unpack a row of color image data from a client buffer according to
 * the pixel unpacking parameters.
 * Return GLchan values in the specified dest image format.
 * This is used by glDrawPixels and glTexImage?D().
 * \param ctx - the context
 *         n - number of pixels in the span
 *         dstFormat - format of destination color array
 *         dest - the destination color array
 *         srcFormat - source image format
 *         srcType - source image  data type
 *         source - source image pointer
 *         srcPacking - pixel unpacking parameters
 *         transferOps - bitmask of IMAGE_*_BIT values of operations to apply
 *
 * XXX perhaps expand this to process whole images someday.
 */
void
_mesa_unpack_color_span_chan( GLcontext *ctx,
                              GLuint n, GLenum dstFormat, GLchan dest[],
                              GLenum srcFormat, GLenum srcType,
                              const GLvoid *source,
                              const struct gl_pixelstore_attrib *srcPacking,
                              GLbitfield transferOps )
{
   ASSERT(dstFormat == GL_ALPHA ||
          dstFormat == GL_LUMINANCE ||
          dstFormat == GL_LUMINANCE_ALPHA ||
          dstFormat == GL_INTENSITY ||
          dstFormat == GL_RGB ||
          dstFormat == GL_RGBA ||
          dstFormat == GL_COLOR_INDEX);

   ASSERT(srcFormat == GL_RED ||
          srcFormat == GL_GREEN ||
          srcFormat == GL_BLUE ||
          srcFormat == GL_ALPHA ||
          srcFormat == GL_LUMINANCE ||
          srcFormat == GL_LUMINANCE_ALPHA ||
          srcFormat == GL_INTENSITY ||
          srcFormat == GL_RGB ||
          srcFormat == GL_BGR ||
          srcFormat == GL_RGBA ||
          srcFormat == GL_BGRA ||
          srcFormat == GL_ABGR_EXT ||
          srcFormat == GL_COLOR_INDEX);

   ASSERT(srcType == GL_BITMAP ||
          srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT ||
          srcType == GL_UNSIGNED_BYTE_3_3_2 ||
          srcType == GL_UNSIGNED_BYTE_2_3_3_REV ||
          srcType == GL_UNSIGNED_SHORT_5_6_5 ||
          srcType == GL_UNSIGNED_SHORT_5_6_5_REV ||
          srcType == GL_UNSIGNED_SHORT_4_4_4_4 ||
          srcType == GL_UNSIGNED_SHORT_4_4_4_4_REV ||
          srcType == GL_UNSIGNED_SHORT_5_5_5_1 ||
          srcType == GL_UNSIGNED_SHORT_1_5_5_5_REV ||
          srcType == GL_UNSIGNED_INT_8_8_8_8 ||
          srcType == GL_UNSIGNED_INT_8_8_8_8_REV ||
          srcType == GL_UNSIGNED_INT_10_10_10_2 ||
          srcType == GL_UNSIGNED_INT_2_10_10_10_REV);

   /* Try simple cases first */
   if (transferOps == 0) {
      if (srcType == CHAN_TYPE) {
         if (dstFormat == GL_RGBA) {
            if (srcFormat == GL_RGBA) {
               _mesa_memcpy( dest, source, n * 4 * sizeof(GLchan) );
               return;
            }
            else if (srcFormat == GL_RGB) {
               GLuint i;
               const GLchan *src = (const GLchan *) source;
               GLchan *dst = dest;
               for (i = 0; i < n; i++) {
                  dst[0] = src[0];
                  dst[1] = src[1];
                  dst[2] = src[2];
                  dst[3] = CHAN_MAX;
                  src += 3;
                  dst += 4;
               }
               return;
            }
         }
         else if (dstFormat == GL_RGB) {
            if (srcFormat == GL_RGB) {
               _mesa_memcpy( dest, source, n * 3 * sizeof(GLchan) );
               return;
            }
            else if (srcFormat == GL_RGBA) {
               GLuint i;
               const GLchan *src = (const GLchan *) source;
               GLchan *dst = dest;
               for (i = 0; i < n; i++) {
                  dst[0] = src[0];
                  dst[1] = src[1];
                  dst[2] = src[2];
                  src += 4;
                  dst += 3;
               }
               return;
            }
         }
         else if (dstFormat == srcFormat) {
            GLint comps = _mesa_components_in_format(srcFormat);
            assert(comps > 0);
            _mesa_memcpy( dest, source, n * comps * sizeof(GLchan) );
            return;
         }
      }
      /*
       * Common situation, loading 8bit RGBA/RGB source images
       * into 16/32 bit destination. (OSMesa16/32)
       */
      else if (srcType == GL_UNSIGNED_BYTE) {
         if (dstFormat == GL_RGBA) {
            if (srcFormat == GL_RGB) {
               GLuint i;
               const GLubyte *src = (const GLubyte *) source;
               GLchan *dst = dest;
               for (i = 0; i < n; i++) {
                  dst[0] = UBYTE_TO_CHAN(src[0]);
                  dst[1] = UBYTE_TO_CHAN(src[1]);
                  dst[2] = UBYTE_TO_CHAN(src[2]);
                  dst[3] = CHAN_MAX;
                  src += 3;
                  dst += 4;
               }
               return;
            }
            else if (srcFormat == GL_RGBA) {
               GLuint i;
               const GLubyte *src = (const GLubyte *) source;
               GLchan *dst = dest;
               for (i = 0; i < n; i++) {
                  dst[0] = UBYTE_TO_CHAN(src[0]);
                  dst[1] = UBYTE_TO_CHAN(src[1]);
                  dst[2] = UBYTE_TO_CHAN(src[2]);
                  dst[3] = UBYTE_TO_CHAN(src[3]);
                  src += 4;
                  dst += 4;
               }
               return;
             }
         }
         else if (dstFormat == GL_RGB) {
            if (srcFormat == GL_RGB) {
               GLuint i;
               const GLubyte *src = (const GLubyte *) source;
               GLchan *dst = dest;
               for (i = 0; i < n; i++) {
                  dst[0] = UBYTE_TO_CHAN(src[0]);
                  dst[1] = UBYTE_TO_CHAN(src[1]);
                  dst[2] = UBYTE_TO_CHAN(src[2]);
                  src += 3;
                  dst += 3;
               }
               return;
            }
            else if (srcFormat == GL_RGBA) {
               GLuint i;
               const GLubyte *src = (const GLubyte *) source;
               GLchan *dst = dest;
               for (i = 0; i < n; i++) {
                  dst[0] = UBYTE_TO_CHAN(src[0]);
                  dst[1] = UBYTE_TO_CHAN(src[1]);
                  dst[2] = UBYTE_TO_CHAN(src[2]);
                  src += 4;
                  dst += 3;
               }
               return;
            }
         }
      }
   }


   /* general solution begins here */
   {
      GLint dstComponents;
      GLint dstRedIndex, dstGreenIndex, dstBlueIndex, dstAlphaIndex;
      GLint dstLuminanceIndex, dstIntensityIndex;
      GLfloat rgba[MAX_WIDTH][4];

      dstComponents = _mesa_components_in_format( dstFormat );
      /* source & dest image formats should have been error checked by now */
      assert(dstComponents > 0);

      /*
       * Extract image data and convert to RGBA floats
       */
      assert(n <= MAX_WIDTH);
      if (srcFormat == GL_COLOR_INDEX) {
         GLuint indexes[MAX_WIDTH];
         extract_uint_indexes(n, indexes, srcFormat, srcType, source,
                              srcPacking);

         if (dstFormat == GL_COLOR_INDEX) {
            GLuint i;
            _mesa_apply_ci_transfer_ops(ctx, transferOps, n, indexes);
            /* convert to GLchan and return */
            for (i = 0; i < n; i++) {
               dest[i] = (GLchan) (indexes[i] & 0xff);
            }
            return;
         }
         else {
            /* Convert indexes to RGBA */
            if (transferOps & IMAGE_SHIFT_OFFSET_BIT) {
               shift_and_offset_ci(ctx, n, indexes);
            }
            _mesa_map_ci_to_rgba(ctx, n, indexes, rgba);
         }

         /* Don't do RGBA scale/bias or RGBA->RGBA mapping if starting
          * with color indexes.
          */
         transferOps &= ~(IMAGE_SCALE_BIAS_BIT | IMAGE_MAP_COLOR_BIT);
      }
      else {
         /* non-color index data */
         extract_float_rgba(n, rgba, srcFormat, srcType, source,
                            srcPacking->SwapBytes);
      }

      /* Need to clamp if returning GLubytes or GLushorts */
#if CHAN_TYPE != GL_FLOAT
      transferOps |= IMAGE_CLAMP_BIT;
#endif

      if (transferOps) {
         _mesa_apply_rgba_transfer_ops(ctx, transferOps, n, rgba);
      }

      /* Now determine which color channels we need to produce.
       * And determine the dest index (offset) within each color tuple.
       */
      switch (dstFormat) {
         case GL_ALPHA:
            dstAlphaIndex = 0;
            dstRedIndex = dstGreenIndex = dstBlueIndex = -1;
            dstLuminanceIndex = dstIntensityIndex = -1;
            break;
         case GL_LUMINANCE:
            dstLuminanceIndex = 0;
            dstRedIndex = dstGreenIndex = dstBlueIndex = dstAlphaIndex = -1;
            dstIntensityIndex = -1;
            break;
         case GL_LUMINANCE_ALPHA:
            dstLuminanceIndex = 0;
            dstAlphaIndex = 1;
            dstRedIndex = dstGreenIndex = dstBlueIndex = -1;
            dstIntensityIndex = -1;
            break;
         case GL_INTENSITY:
            dstIntensityIndex = 0;
            dstRedIndex = dstGreenIndex = dstBlueIndex = dstAlphaIndex = -1;
            dstLuminanceIndex = -1;
            break;
         case GL_RGB:
            dstRedIndex = 0;
            dstGreenIndex = 1;
            dstBlueIndex = 2;
            dstAlphaIndex = dstLuminanceIndex = dstIntensityIndex = -1;
            break;
         case GL_RGBA:
            dstRedIndex = 0;
            dstGreenIndex = 1;
            dstBlueIndex = 2;
            dstAlphaIndex = 3;
            dstLuminanceIndex = dstIntensityIndex = -1;
            break;
         default:
            _mesa_problem(ctx, "bad dstFormat in _mesa_unpack_chan_span()");
            return;
      }


      /* Now return the GLchan data in the requested dstFormat */

      if (dstRedIndex >= 0) {
         GLchan *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            CLAMPED_FLOAT_TO_CHAN(dst[dstRedIndex], rgba[i][RCOMP]);
            dst += dstComponents;
         }
      }

      if (dstGreenIndex >= 0) {
         GLchan *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            CLAMPED_FLOAT_TO_CHAN(dst[dstGreenIndex], rgba[i][GCOMP]);
            dst += dstComponents;
         }
      }

      if (dstBlueIndex >= 0) {
         GLchan *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            CLAMPED_FLOAT_TO_CHAN(dst[dstBlueIndex], rgba[i][BCOMP]);
            dst += dstComponents;
         }
      }

      if (dstAlphaIndex >= 0) {
         GLchan *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            CLAMPED_FLOAT_TO_CHAN(dst[dstAlphaIndex], rgba[i][ACOMP]);
            dst += dstComponents;
         }
      }

      if (dstIntensityIndex >= 0) {
         GLchan *dst = dest;
         GLuint i;
         assert(dstIntensityIndex == 0);
         assert(dstComponents == 1);
         for (i = 0; i < n; i++) {
            /* Intensity comes from red channel */
            CLAMPED_FLOAT_TO_CHAN(dst[i], rgba[i][RCOMP]);
         }
      }

      if (dstLuminanceIndex >= 0) {
         GLchan *dst = dest;
         GLuint i;
         assert(dstLuminanceIndex == 0);
         for (i = 0; i < n; i++) {
            /* Luminance comes from red channel */
            CLAMPED_FLOAT_TO_CHAN(dst[0], rgba[i][RCOMP]);
            dst += dstComponents;
         }
      }
   }
}


/**
 * Same as _mesa_unpack_color_span_chan(), but return GLfloat data
 * instead of GLchan.
 */
void
_mesa_unpack_color_span_float( GLcontext *ctx,
                               GLuint n, GLenum dstFormat, GLfloat dest[],
                               GLenum srcFormat, GLenum srcType,
                               const GLvoid *source,
                               const struct gl_pixelstore_attrib *srcPacking,
                               GLbitfield transferOps )
{
   ASSERT(dstFormat == GL_ALPHA ||
          dstFormat == GL_LUMINANCE ||
          dstFormat == GL_LUMINANCE_ALPHA ||
          dstFormat == GL_INTENSITY ||
          dstFormat == GL_RGB ||
          dstFormat == GL_RGBA ||
          dstFormat == GL_COLOR_INDEX);

   ASSERT(srcFormat == GL_RED ||
          srcFormat == GL_GREEN ||
          srcFormat == GL_BLUE ||
          srcFormat == GL_ALPHA ||
          srcFormat == GL_LUMINANCE ||
          srcFormat == GL_LUMINANCE_ALPHA ||
          srcFormat == GL_INTENSITY ||
          srcFormat == GL_RGB ||
          srcFormat == GL_BGR ||
          srcFormat == GL_RGBA ||
          srcFormat == GL_BGRA ||
          srcFormat == GL_ABGR_EXT ||
          srcFormat == GL_COLOR_INDEX);

   ASSERT(srcType == GL_BITMAP ||
          srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT ||
          srcType == GL_UNSIGNED_BYTE_3_3_2 ||
          srcType == GL_UNSIGNED_BYTE_2_3_3_REV ||
          srcType == GL_UNSIGNED_SHORT_5_6_5 ||
          srcType == GL_UNSIGNED_SHORT_5_6_5_REV ||
          srcType == GL_UNSIGNED_SHORT_4_4_4_4 ||
          srcType == GL_UNSIGNED_SHORT_4_4_4_4_REV ||
          srcType == GL_UNSIGNED_SHORT_5_5_5_1 ||
          srcType == GL_UNSIGNED_SHORT_1_5_5_5_REV ||
          srcType == GL_UNSIGNED_INT_8_8_8_8 ||
          srcType == GL_UNSIGNED_INT_8_8_8_8_REV ||
          srcType == GL_UNSIGNED_INT_10_10_10_2 ||
          srcType == GL_UNSIGNED_INT_2_10_10_10_REV);

   /* general solution, no special cases, yet */
   {
      GLint dstComponents;
      GLint dstRedIndex, dstGreenIndex, dstBlueIndex, dstAlphaIndex;
      GLint dstLuminanceIndex, dstIntensityIndex;
      GLfloat rgba[MAX_WIDTH][4];

      dstComponents = _mesa_components_in_format( dstFormat );
      /* source & dest image formats should have been error checked by now */
      assert(dstComponents > 0);

      /*
       * Extract image data and convert to RGBA floats
       */
      assert(n <= MAX_WIDTH);
      if (srcFormat == GL_COLOR_INDEX) {
         GLuint indexes[MAX_WIDTH];
         extract_uint_indexes(n, indexes, srcFormat, srcType, source,
                              srcPacking);

         if (dstFormat == GL_COLOR_INDEX) {
            GLuint i;
            _mesa_apply_ci_transfer_ops(ctx, transferOps, n, indexes);
            /* convert to GLchan and return */
            for (i = 0; i < n; i++) {
               dest[i] = (GLchan) (indexes[i] & 0xff);
            }
            return;
         }
         else {
            /* Convert indexes to RGBA */
            if (transferOps & IMAGE_SHIFT_OFFSET_BIT) {
               shift_and_offset_ci(ctx, n, indexes);
            }
            _mesa_map_ci_to_rgba(ctx, n, indexes, rgba);
         }

         /* Don't do RGBA scale/bias or RGBA->RGBA mapping if starting
          * with color indexes.
          */
         transferOps &= ~(IMAGE_SCALE_BIAS_BIT | IMAGE_MAP_COLOR_BIT);
      }
      else {
         /* non-color index data */
         extract_float_rgba(n, rgba, srcFormat, srcType, source,
                            srcPacking->SwapBytes);
      }

      if (transferOps) {
         _mesa_apply_rgba_transfer_ops(ctx, transferOps, n, rgba);
      }

      /* Now determine which color channels we need to produce.
       * And determine the dest index (offset) within each color tuple.
       */
      switch (dstFormat) {
         case GL_ALPHA:
            dstAlphaIndex = 0;
            dstRedIndex = dstGreenIndex = dstBlueIndex = -1;
            dstLuminanceIndex = dstIntensityIndex = -1;
            break;
         case GL_LUMINANCE:
            dstLuminanceIndex = 0;
            dstRedIndex = dstGreenIndex = dstBlueIndex = dstAlphaIndex = -1;
            dstIntensityIndex = -1;
            break;
         case GL_LUMINANCE_ALPHA:
            dstLuminanceIndex = 0;
            dstAlphaIndex = 1;
            dstRedIndex = dstGreenIndex = dstBlueIndex = -1;
            dstIntensityIndex = -1;
            break;
         case GL_INTENSITY:
            dstIntensityIndex = 0;
            dstRedIndex = dstGreenIndex = dstBlueIndex = dstAlphaIndex = -1;
            dstLuminanceIndex = -1;
            break;
         case GL_RGB:
            dstRedIndex = 0;
            dstGreenIndex = 1;
            dstBlueIndex = 2;
            dstAlphaIndex = dstLuminanceIndex = dstIntensityIndex = -1;
            break;
         case GL_RGBA:
            dstRedIndex = 0;
            dstGreenIndex = 1;
            dstBlueIndex = 2;
            dstAlphaIndex = 3;
            dstLuminanceIndex = dstIntensityIndex = -1;
            break;
         default:
            _mesa_problem(ctx, "bad dstFormat in _mesa_unpack_color_span_float()");
            return;
      }

      /* Now pack results in the requested dstFormat */
      if (dstRedIndex >= 0) {
         GLfloat *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[dstRedIndex] = rgba[i][RCOMP];
            dst += dstComponents;
         }
      }

      if (dstGreenIndex >= 0) {
         GLfloat *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[dstGreenIndex] = rgba[i][GCOMP];
            dst += dstComponents;
         }
      }

      if (dstBlueIndex >= 0) {
         GLfloat *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[dstBlueIndex] = rgba[i][BCOMP];
            dst += dstComponents;
         }
      }

      if (dstAlphaIndex >= 0) {
         GLfloat *dst = dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[dstAlphaIndex] = rgba[i][ACOMP];
            dst += dstComponents;
         }
      }

      if (dstIntensityIndex >= 0) {
         GLfloat *dst = dest;
         GLuint i;
         assert(dstIntensityIndex == 0);
         assert(dstComponents == 1);
         for (i = 0; i < n; i++) {
            /* Intensity comes from red channel */
            dst[i] = rgba[i][RCOMP];
         }
      }

      if (dstLuminanceIndex >= 0) {
         GLfloat *dst = dest;
         GLuint i;
         assert(dstLuminanceIndex == 0);
         for (i = 0; i < n; i++) {
            /* Luminance comes from red channel */
            dst[0] = rgba[i][RCOMP];
            dst += dstComponents;
         }
      }
   }
}

/**
 * Similar to _mesa_unpack_color_span_float(), but for dudv data instead of rgba,
 * directly return GLbyte data, no transfer ops apply.
 */
void
_mesa_unpack_dudv_span_byte( GLcontext *ctx,
                             GLuint n, GLenum dstFormat, GLbyte dest[],
                             GLenum srcFormat, GLenum srcType,
                             const GLvoid *source,
                             const struct gl_pixelstore_attrib *srcPacking,
                             GLbitfield transferOps )
{
   ASSERT(dstFormat == GL_DUDV_ATI);
   ASSERT(srcFormat == GL_DUDV_ATI);

   ASSERT(srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT);

   /* general solution */
   {
      GLint dstComponents;
      GLfloat rgba[MAX_WIDTH][4];
      GLbyte *dst = dest;
      GLuint i;

      dstComponents = _mesa_components_in_format( dstFormat );
      /* source & dest image formats should have been error checked by now */
      assert(dstComponents > 0);

      /*
       * Extract image data and convert to RGBA floats
       */
      assert(n <= MAX_WIDTH);
      extract_float_rgba(n, rgba, srcFormat, srcType, source,
                         srcPacking->SwapBytes);


      /* Now determine which color channels we need to produce.
       * And determine the dest index (offset) within each color tuple.
       */

      /* Now pack results in the requested dstFormat */
      for (i = 0; i < n; i++) {
         /* not sure - need clamp[-1,1] here? */
         dst[0] = FLOAT_TO_BYTE(rgba[i][RCOMP]);
         dst[1] = FLOAT_TO_BYTE(rgba[i][GCOMP]);
         dst += dstComponents;
      }
   }
}

/*
 * Unpack a row of color index data from a client buffer according to
 * the pixel unpacking parameters.
 * This is (or will be) used by glDrawPixels, glTexImage[123]D, etc.
 *
 * Args:  ctx - the context
 *        n - number of pixels
 *        dstType - destination data type
 *        dest - destination array
 *        srcType - source pixel type
 *        source - source data pointer
 *        srcPacking - pixel unpacking parameters
 *        transferOps - the pixel transfer operations to apply
 */
void
_mesa_unpack_index_span( const GLcontext *ctx, GLuint n,
                         GLenum dstType, GLvoid *dest,
                         GLenum srcType, const GLvoid *source,
                         const struct gl_pixelstore_attrib *srcPacking,
                         GLbitfield transferOps )
{
   ASSERT(srcType == GL_BITMAP ||
          srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT);

   ASSERT(dstType == GL_UNSIGNED_BYTE ||
          dstType == GL_UNSIGNED_SHORT ||
          dstType == GL_UNSIGNED_INT);


   transferOps &= (IMAGE_MAP_COLOR_BIT | IMAGE_SHIFT_OFFSET_BIT);

   /*
    * Try simple cases first
    */
   if (transferOps == 0 && srcType == GL_UNSIGNED_BYTE
       && dstType == GL_UNSIGNED_BYTE) {
      _mesa_memcpy(dest, source, n * sizeof(GLubyte));
   }
   else if (transferOps == 0 && srcType == GL_UNSIGNED_INT
            && dstType == GL_UNSIGNED_INT && !srcPacking->SwapBytes) {
      _mesa_memcpy(dest, source, n * sizeof(GLuint));
   }
   else {
      /*
       * general solution
       */
      GLuint indexes[MAX_WIDTH];
      assert(n <= MAX_WIDTH);

      extract_uint_indexes(n, indexes, GL_COLOR_INDEX, srcType, source,
                           srcPacking);

      if (transferOps)
         _mesa_apply_ci_transfer_ops(ctx, transferOps, n, indexes);

      /* convert to dest type */
      switch (dstType) {
         case GL_UNSIGNED_BYTE:
            {
               GLubyte *dst = (GLubyte *) dest;
               GLuint i;
               for (i = 0; i < n; i++) {
                  dst[i] = (GLubyte) (indexes[i] & 0xff);
               }
            }
            break;
         case GL_UNSIGNED_SHORT:
            {
               GLuint *dst = (GLuint *) dest;
               GLuint i;
               for (i = 0; i < n; i++) {
                  dst[i] = (GLushort) (indexes[i] & 0xffff);
               }
            }
            break;
         case GL_UNSIGNED_INT:
            _mesa_memcpy(dest, indexes, n * sizeof(GLuint));
            break;
         default:
            _mesa_problem(ctx, "bad dstType in _mesa_unpack_index_span");
      }
   }
}


void
_mesa_pack_index_span( const GLcontext *ctx, GLuint n,
                       GLenum dstType, GLvoid *dest, const GLuint *source,
                       const struct gl_pixelstore_attrib *dstPacking,
                       GLbitfield transferOps )
{
   GLuint indexes[MAX_WIDTH];

   ASSERT(n <= MAX_WIDTH);

   transferOps &= (IMAGE_MAP_COLOR_BIT | IMAGE_SHIFT_OFFSET_BIT);

   if (transferOps & (IMAGE_MAP_COLOR_BIT | IMAGE_SHIFT_OFFSET_BIT)) {
      /* make a copy of input */
      _mesa_memcpy(indexes, source, n * sizeof(GLuint));
      _mesa_apply_ci_transfer_ops(ctx, transferOps, n, indexes);
      source = indexes;
   }

   switch (dstType) {
   case GL_UNSIGNED_BYTE:
      {
         GLubyte *dst = (GLubyte *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            *dst++ = (GLubyte) source[i];
         }
      }
      break;
   case GL_BYTE:
      {
         GLbyte *dst = (GLbyte *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = (GLbyte) source[i];
         }
      }
      break;
   case GL_UNSIGNED_SHORT:
      {
         GLushort *dst = (GLushort *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = (GLushort) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_SHORT:
      {
         GLshort *dst = (GLshort *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = (GLshort) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_UNSIGNED_INT:
      {
         GLuint *dst = (GLuint *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = (GLuint) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_INT:
      {
         GLint *dst = (GLint *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = (GLint) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_FLOAT:
      {
         GLfloat *dst = (GLfloat *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = (GLfloat) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_HALF_FLOAT_ARB:
      {
         GLhalfARB *dst = (GLhalfARB *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = _mesa_float_to_half((GLfloat) source[i]);
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   default:
      _mesa_problem(ctx, "bad type in _mesa_pack_index_span");
   }
}


/*
 * Unpack a row of stencil data from a client buffer according to
 * the pixel unpacking parameters.
 * This is (or will be) used by glDrawPixels
 *
 * Args:  ctx - the context
 *        n - number of pixels
 *        dstType - destination data type
 *        dest - destination array
 *        srcType - source pixel type
 *        source - source data pointer
 *        srcPacking - pixel unpacking parameters
 *        transferOps - apply offset/bias/lookup ops?
 */
void
_mesa_unpack_stencil_span( const GLcontext *ctx, GLuint n,
                           GLenum dstType, GLvoid *dest,
                           GLenum srcType, const GLvoid *source,
                           const struct gl_pixelstore_attrib *srcPacking,
                           GLbitfield transferOps )
{
   ASSERT(srcType == GL_BITMAP ||
          srcType == GL_UNSIGNED_BYTE ||
          srcType == GL_BYTE ||
          srcType == GL_UNSIGNED_SHORT ||
          srcType == GL_SHORT ||
          srcType == GL_UNSIGNED_INT ||
          srcType == GL_INT ||
          srcType == GL_UNSIGNED_INT_24_8_EXT ||
          srcType == GL_HALF_FLOAT_ARB ||
          srcType == GL_FLOAT);

   ASSERT(dstType == GL_UNSIGNED_BYTE ||
          dstType == GL_UNSIGNED_SHORT ||
          dstType == GL_UNSIGNED_INT);

   /* only shift and offset apply to stencil */
   transferOps &= IMAGE_SHIFT_OFFSET_BIT;

   /*
    * Try simple cases first
    */
   if (transferOps == 0 &&
       !ctx->Pixel.MapStencilFlag &&
       srcType == GL_UNSIGNED_BYTE &&
       dstType == GL_UNSIGNED_BYTE) {
      _mesa_memcpy(dest, source, n * sizeof(GLubyte));
   }
   else if (transferOps == 0 &&
            !ctx->Pixel.MapStencilFlag &&
            srcType == GL_UNSIGNED_INT &&
            dstType == GL_UNSIGNED_INT &&
            !srcPacking->SwapBytes) {
      _mesa_memcpy(dest, source, n * sizeof(GLuint));
   }
   else {
      /*
       * general solution
       */
      GLuint indexes[MAX_WIDTH];
      assert(n <= MAX_WIDTH);

      extract_uint_indexes(n, indexes, GL_STENCIL_INDEX, srcType, source,
                           srcPacking);

      if (transferOps & IMAGE_SHIFT_OFFSET_BIT) {
         /* shift and offset indexes */
         shift_and_offset_ci(ctx, n, indexes);
      }

      if (ctx->Pixel.MapStencilFlag) {
         /* Apply stencil lookup table */
         const GLuint mask = ctx->PixelMaps.StoS.Size - 1;
         GLuint i;
         for (i = 0; i < n; i++) {
            indexes[i] = (GLuint)ctx->PixelMaps.StoS.Map[ indexes[i] & mask ];
         }
      }

      /* convert to dest type */
      switch (dstType) {
         case GL_UNSIGNED_BYTE:
            {
               GLubyte *dst = (GLubyte *) dest;
               GLuint i;
               for (i = 0; i < n; i++) {
                  dst[i] = (GLubyte) (indexes[i] & 0xff);
               }
            }
            break;
         case GL_UNSIGNED_SHORT:
            {
               GLuint *dst = (GLuint *) dest;
               GLuint i;
               for (i = 0; i < n; i++) {
                  dst[i] = (GLushort) (indexes[i] & 0xffff);
               }
            }
            break;
         case GL_UNSIGNED_INT:
            _mesa_memcpy(dest, indexes, n * sizeof(GLuint));
            break;
         default:
            _mesa_problem(ctx, "bad dstType in _mesa_unpack_stencil_span");
      }
   }
}


void
_mesa_pack_stencil_span( const GLcontext *ctx, GLuint n,
                         GLenum dstType, GLvoid *dest, const GLstencil *source,
                         const struct gl_pixelstore_attrib *dstPacking )
{
   GLstencil stencil[MAX_WIDTH];

   ASSERT(n <= MAX_WIDTH);

   if (ctx->Pixel.IndexShift || ctx->Pixel.IndexOffset ||
       ctx->Pixel.MapStencilFlag) {
      /* make a copy of input */
      _mesa_memcpy(stencil, source, n * sizeof(GLstencil));
      _mesa_apply_stencil_transfer_ops(ctx, n, stencil);
      source = stencil;
   }

   switch (dstType) {
   case GL_UNSIGNED_BYTE:
      if (sizeof(GLstencil) == 1) {
         _mesa_memcpy( dest, source, n );
      }
      else {
         GLubyte *dst = (GLubyte *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLubyte) source[i];
         }
      }
      break;
   case GL_BYTE:
      {
         GLbyte *dst = (GLbyte *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLbyte) (source[i] & 0x7f);
         }
      }
      break;
   case GL_UNSIGNED_SHORT:
      {
         GLushort *dst = (GLushort *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLushort) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_SHORT:
      {
         GLshort *dst = (GLshort *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLshort) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_UNSIGNED_INT:
      {
         GLuint *dst = (GLuint *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLuint) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_INT:
      {
         GLint *dst = (GLint *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLint) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_FLOAT:
      {
         GLfloat *dst = (GLfloat *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = (GLfloat) source[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_HALF_FLOAT_ARB:
      {
         GLhalfARB *dst = (GLhalfARB *) dest;
         GLuint i;
         for (i=0;i<n;i++) {
            dst[i] = _mesa_float_to_half( (float) source[i] );
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_BITMAP:
      if (dstPacking->LsbFirst) {
         GLubyte *dst = (GLubyte *) dest;
         GLint shift = 0;
         GLuint i;
         for (i = 0; i < n; i++) {
            if (shift == 0)
               *dst = 0;
            *dst |= ((source[i] != 0) << shift);
            shift++;
            if (shift == 8) {
               shift = 0;
               dst++;
            }
         }
      }
      else {
         GLubyte *dst = (GLubyte *) dest;
         GLint shift = 7;
         GLuint i;
         for (i = 0; i < n; i++) {
            if (shift == 7)
               *dst = 0;
            *dst |= ((source[i] != 0) << shift);
            shift--;
            if (shift < 0) {
               shift = 7;
               dst++;
            }
         }
      }
      break;
   default:
      _mesa_problem(ctx, "bad type in _mesa_pack_index_span");
   }
}

#define DEPTH_VALUES(GLTYPE, GLTYPE2FLOAT)                              \
    do {                                                                \
        GLuint i;                                                       \
        const GLTYPE *src = (const GLTYPE *)source;                     \
        for (i = 0; i < n; i++) {                                       \
            GLTYPE value = src[i];                                      \
            if (srcPacking->SwapBytes) {                                \
                if (sizeof(GLTYPE) == 2) {                              \
                    SWAP2BYTE(value);                                   \
                } else if (sizeof(GLTYPE) == 4) {                       \
                    SWAP4BYTE(value);                                   \
                }                                                       \
            }                                                           \
            depthValues[i] = GLTYPE2FLOAT(value);                       \
        }                                                               \
    } while (0)


/**
 * Unpack a row of depth/z values from memory, returning GLushort, GLuint
 * or GLfloat values.
 * The glPixelTransfer (scale/bias) params will be applied.
 *
 * \param dstType  one of GL_UNSIGNED_SHORT, GL_UNSIGNED_INT, GL_FLOAT
 * \param depthMax  max value for returned GLushort or GLuint values
 *                  (ignored for GLfloat).
 */
void
_mesa_unpack_depth_span( const GLcontext *ctx, GLuint n,
                         GLenum dstType, GLvoid *dest, GLuint depthMax,
                         GLenum srcType, const GLvoid *source,
                         const struct gl_pixelstore_attrib *srcPacking )
{
   GLfloat depthTemp[MAX_WIDTH], *depthValues;
   GLboolean needClamp = GL_FALSE;

   /* Look for special cases first.
    * Not only are these faster, they're less prone to numeric conversion
    * problems.  Otherwise, converting from an int type to a float then
    * back to an int type can introduce errors that will show up as
    * artifacts in things like depth peeling which uses glCopyTexImage.
    */
   if (ctx->Pixel.DepthScale == 1.0 && ctx->Pixel.DepthBias == 0.0) {
      if (srcType == GL_UNSIGNED_INT && dstType == GL_UNSIGNED_SHORT) {
         const GLuint *src = (const GLuint *) source;
         GLushort *dst = (GLushort *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = src[i] >> 16;
         }
         return;
      }
      if (srcType == GL_UNSIGNED_SHORT
          && dstType == GL_UNSIGNED_INT
          && depthMax == 0xffffffff) {
         const GLushort *src = (const GLushort *) source;
         GLuint *dst = (GLuint *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = src[i] | (src[i] << 16);
         }
         return;
      }
      if (srcType == GL_UNSIGNED_INT_24_8
          && dstType == GL_UNSIGNED_INT
          && depthMax == 0xffffff) {
         const GLuint *src = (const GLuint *) source;
         GLuint *dst = (GLuint *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = src[i] >> 8;
         }
         return;
      }
      /* XXX may want to add additional cases here someday */
   }

   /* general case path follows */

   if (dstType == GL_FLOAT) {
      depthValues = (GLfloat *) dest;
   }
   else {
      depthValues = depthTemp;
   }

   /* Convert incoming values to GLfloat.  Some conversions will require
    * clamping, below.
    */
   switch (srcType) {
      case GL_BYTE:
         DEPTH_VALUES(GLbyte, BYTE_TO_FLOAT);
         needClamp = GL_TRUE;
         break;
      case GL_UNSIGNED_BYTE:
         DEPTH_VALUES(GLubyte, UBYTE_TO_FLOAT);
         break;
      case GL_SHORT:
         DEPTH_VALUES(GLshort, SHORT_TO_FLOAT);
         needClamp = GL_TRUE;
         break;
      case GL_UNSIGNED_SHORT:
         DEPTH_VALUES(GLushort, USHORT_TO_FLOAT);
         break;
      case GL_INT:
         DEPTH_VALUES(GLint, INT_TO_FLOAT);
         needClamp = GL_TRUE;
         break;
      case GL_UNSIGNED_INT:
         DEPTH_VALUES(GLuint, UINT_TO_FLOAT);
         break;
      case GL_UNSIGNED_INT_24_8_EXT: /* GL_EXT_packed_depth_stencil */
         if (dstType == GL_UNSIGNED_INT_24_8_EXT &&
             depthMax == 0xffffff &&
             ctx->Pixel.DepthScale == 1.0 &&
             ctx->Pixel.DepthBias == 0.0) {
            const GLuint *src = (const GLuint *) source;
            GLuint *zValues = (GLuint *) dest;
            GLuint i;
            for (i = 0; i < n; i++) {
                GLuint value = src[i];
                if (srcPacking->SwapBytes) {
                    SWAP4BYTE(value);
                }
                zValues[i] = value & 0xffffff00;
            }
            return;
         }
         else {
            const GLuint *src = (const GLuint *) source;
            const GLfloat scale = 1.0f / 0xffffff;
            GLuint i;
            for (i = 0; i < n; i++) {
                GLuint value = src[i];
                if (srcPacking->SwapBytes) {
                    SWAP4BYTE(value);
                }
                depthValues[i] = (value >> 8) * scale;
            }
         }
         break;
      case GL_FLOAT:
         DEPTH_VALUES(GLfloat, 1*);
         needClamp = GL_TRUE;
         break;
      case GL_HALF_FLOAT_ARB:
         {
            GLuint i;
            const GLhalfARB *src = (const GLhalfARB *) source;
            for (i = 0; i < n; i++) {
               GLhalfARB value = src[i];
               if (srcPacking->SwapBytes) {
                  SWAP2BYTE(value);
               }
               depthValues[i] = _mesa_half_to_float(value);
            }
            needClamp = GL_TRUE;
         }
         break;
      default:
         _mesa_problem(NULL, "bad type in _mesa_unpack_depth_span()");
         return;
   }

   /* apply depth scale and bias */
   {
      const GLfloat scale = ctx->Pixel.DepthScale;
      const GLfloat bias = ctx->Pixel.DepthBias;
      if (scale != 1.0 || bias != 0.0) {
         GLuint i;
         for (i = 0; i < n; i++) {
            depthValues[i] = depthValues[i] * scale + bias;
         }
         needClamp = GL_TRUE;
      }
   }

   /* clamp to [0, 1] */
   if (needClamp) {
      GLuint i;
      for (i = 0; i < n; i++) {
         depthValues[i] = (GLfloat)CLAMP(depthValues[i], 0.0, 1.0);
      }
   }

   /*
    * Convert values to dstType
    */
   if (dstType == GL_UNSIGNED_INT) {
      GLuint *zValues = (GLuint *) dest;
      GLuint i;
      if (depthMax <= 0xffffff) {
         /* no overflow worries */
         for (i = 0; i < n; i++) {
            zValues[i] = (GLuint) (depthValues[i] * (GLfloat) depthMax);
         }
      }
      else {
         /* need to use double precision to prevent overflow problems */
         for (i = 0; i < n; i++) {
            GLdouble z = depthValues[i] * (GLfloat) depthMax;
            if (z >= (GLdouble) 0xffffffff)
               zValues[i] = 0xffffffff;
            else
               zValues[i] = (GLuint) z;
         }
      }
   }
   else if (dstType == GL_UNSIGNED_SHORT) {
      GLushort *zValues = (GLushort *) dest;
      GLuint i;
      ASSERT(depthMax <= 0xffff);
      for (i = 0; i < n; i++) {
         zValues[i] = (GLushort) (depthValues[i] * (GLfloat) depthMax);
      }
   }
   else {
      ASSERT(dstType == GL_FLOAT);
      /*ASSERT(depthMax == 1.0F);*/
   }
}


/*
 * Pack an array of depth values.  The values are floats in [0,1].
 */
void
_mesa_pack_depth_span( const GLcontext *ctx, GLuint n, GLvoid *dest,
                       GLenum dstType, const GLfloat *depthSpan,
                       const struct gl_pixelstore_attrib *dstPacking )
{
   GLfloat depthCopy[MAX_WIDTH];

   ASSERT(n <= MAX_WIDTH);

   if (ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0) {
      _mesa_memcpy(depthCopy, depthSpan, n * sizeof(GLfloat));
      _mesa_scale_and_bias_depth(ctx, n, depthCopy);
      depthSpan = depthCopy;
   }

   switch (dstType) {
   case GL_UNSIGNED_BYTE:
      {
         GLubyte *dst = (GLubyte *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = FLOAT_TO_UBYTE( depthSpan[i] );
         }
      }
      break;
   case GL_BYTE:
      {
         GLbyte *dst = (GLbyte *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = FLOAT_TO_BYTE( depthSpan[i] );
         }
      }
      break;
   case GL_UNSIGNED_SHORT:
      {
         GLushort *dst = (GLushort *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            CLAMPED_FLOAT_TO_USHORT(dst[i], depthSpan[i]);
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_SHORT:
      {
         GLshort *dst = (GLshort *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = FLOAT_TO_SHORT( depthSpan[i] );
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   case GL_UNSIGNED_INT:
      {
         GLuint *dst = (GLuint *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = FLOAT_TO_UINT( depthSpan[i] );
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_INT:
      {
         GLint *dst = (GLint *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = FLOAT_TO_INT( depthSpan[i] );
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_FLOAT:
      {
         GLfloat *dst = (GLfloat *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = depthSpan[i];
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap4( (GLuint *) dst, n );
         }
      }
      break;
   case GL_HALF_FLOAT_ARB:
      {
         GLhalfARB *dst = (GLhalfARB *) dest;
         GLuint i;
         for (i = 0; i < n; i++) {
            dst[i] = _mesa_float_to_half(depthSpan[i]);
         }
         if (dstPacking->SwapBytes) {
            _mesa_swap2( (GLushort *) dst, n );
         }
      }
      break;
   default:
      _mesa_problem(ctx, "bad type in _mesa_pack_depth_span");
   }
}



/**
 * Pack depth and stencil values as GL_DEPTH_STENCIL/GL_UNSIGNED_INT_24_8.
 */
void
_mesa_pack_depth_stencil_span(const GLcontext *ctx, GLuint n, GLuint *dest,
                              const GLfloat *depthVals,
                              const GLstencil *stencilVals,
                              const struct gl_pixelstore_attrib *dstPacking)
{
   GLfloat depthCopy[MAX_WIDTH];
   GLstencil stencilCopy[MAX_WIDTH];
   GLuint i;

   ASSERT(n <= MAX_WIDTH);

   if (ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0) {
      _mesa_memcpy(depthCopy, depthVals, n * sizeof(GLfloat));
      _mesa_scale_and_bias_depth(ctx, n, depthCopy);
      depthVals = depthCopy;
   }

   if (ctx->Pixel.IndexShift ||
       ctx->Pixel.IndexOffset ||
       ctx->Pixel.MapStencilFlag) {
      _mesa_memcpy(stencilCopy, stencilVals, n * sizeof(GLstencil));
      _mesa_apply_stencil_transfer_ops(ctx, n, stencilCopy);
      stencilVals = stencilCopy;
   }

   for (i = 0; i < n; i++) {
      GLuint z = (GLuint) (depthVals[i] * 0xffffff);
      dest[i] = (z << 8) | (stencilVals[i] & 0xff);
   }

   if (dstPacking->SwapBytes) {
      _mesa_swap4(dest, n);
   }
}




/**
 * Unpack image data.  Apply byte swapping, byte flipping (bitmap).
 * Return all image data in a contiguous block.  This is used when we
 * compile glDrawPixels, glTexImage, etc into a display list.  We
 * need a copy of the data in a standard format.
 */
void *
_mesa_unpack_image( GLuint dimensions,
                    GLsizei width, GLsizei height, GLsizei depth,
                    GLenum format, GLenum type, const GLvoid *pixels,
                    const struct gl_pixelstore_attrib *unpack )
{
   GLint bytesPerRow, compsPerRow;
   GLboolean flipBytes, swap2, swap4;

   if (!pixels)
      return NULL;  /* not necessarily an error */

   if (width <= 0 || height <= 0 || depth <= 0)
      return NULL;  /* generate error later */

   if (type == GL_BITMAP) {
      bytesPerRow = (width + 7) >> 3;
      flipBytes = unpack->LsbFirst;
      swap2 = swap4 = GL_FALSE;
      compsPerRow = 0;
   }
   else {
      const GLint bytesPerPixel = _mesa_bytes_per_pixel(format, type);
      GLint components = _mesa_components_in_format(format);
      GLint bytesPerComp;

      if (_mesa_type_is_packed(type))
          components = 1;

      if (bytesPerPixel <= 0 || components <= 0)
         return NULL;   /* bad format or type.  generate error later */
      bytesPerRow = bytesPerPixel * width;
      bytesPerComp = bytesPerPixel / components;
      flipBytes = GL_FALSE;
      swap2 = (bytesPerComp == 2) && unpack->SwapBytes;
      swap4 = (bytesPerComp == 4) && unpack->SwapBytes;
      compsPerRow = components * width;
      assert(compsPerRow >= width);
   }

   {
      GLubyte *destBuffer
         = (GLubyte *) _mesa_malloc(bytesPerRow * height * depth);
      GLubyte *dst;
      GLint img, row;
      if (!destBuffer)
         return NULL;   /* generate GL_OUT_OF_MEMORY later */

      dst = destBuffer;
      for (img = 0; img < depth; img++) {
         for (row = 0; row < height; row++) {
            const GLvoid *src = _mesa_image_address(dimensions, unpack, pixels,
                               width, height, format, type, img, row, 0);

            if ((type == GL_BITMAP) && (unpack->SkipPixels & 0x7)) {
               GLint i;
               flipBytes = GL_FALSE;
               if (unpack->LsbFirst) {
                  GLubyte srcMask = 1 << (unpack->SkipPixels & 0x7);
                  GLubyte dstMask = 128;
                  const GLubyte *s = src;
                  GLubyte *d = dst;
                  *d = 0;
                  for (i = 0; i < width; i++) {
                     if (*s & srcMask) {
                        *d |= dstMask;
                     }
                     if (srcMask == 128) {
                        srcMask = 1;
                        s++;
                     }
                     else {
                        srcMask = srcMask << 1;
                     }
                     if (dstMask == 1) {
                        dstMask = 128;
                        d++;
                        *d = 0;
                     }
                     else {
                        dstMask = dstMask >> 1;
                     }
                  }
               }
               else {
                  GLubyte srcMask = 128 >> (unpack->SkipPixels & 0x7);
                  GLubyte dstMask = 128;
                  const GLubyte *s = src;
                  GLubyte *d = dst;
                  *d = 0;
                  for (i = 0; i < width; i++) {
                     if (*s & srcMask) {
                        *d |= dstMask;
                     }
                     if (srcMask == 1) {
                        srcMask = 128;
                        s++;
                     }
                     else {
                        srcMask = srcMask >> 1;
                     }
                     if (dstMask == 1) {
                        dstMask = 128;
                        d++;
                        *d = 0;
                     }
                     else {
                        dstMask = dstMask >> 1;
                     }
                  }
               }
            }
            else {
               _mesa_memcpy(dst, src, bytesPerRow);
            }

            /* byte flipping/swapping */
            if (flipBytes) {
               flip_bytes((GLubyte *) dst, bytesPerRow);
            }
            else if (swap2) {
               _mesa_swap2((GLushort*) dst, compsPerRow);
            }
            else if (swap4) {
               _mesa_swap4((GLuint*) dst, compsPerRow);
            }
            dst += bytesPerRow;
         }
      }
      return destBuffer;
   }
}

#endif /* _HAVE_FULL_GL */



/**
 * Convert an array of RGBA colors from one datatype to another.
 * NOTE: src may equal dst.  In that case, we use a temporary buffer.
 */
void
_mesa_convert_colors(GLenum srcType, const GLvoid *src,
                     GLenum dstType, GLvoid *dst,
                     GLuint count, const GLubyte mask[])
{
   GLuint tempBuffer[MAX_WIDTH][4];
   const GLboolean useTemp = (src == dst);

   ASSERT(srcType != dstType);

   switch (srcType) {
   case GL_UNSIGNED_BYTE:
      if (dstType == GL_UNSIGNED_SHORT) {
         const GLubyte (*src1)[4] = (const GLubyte (*)[4]) src;
         GLushort (*dst2)[4] = (GLushort (*)[4]) (useTemp ? tempBuffer : dst);
         GLuint i;
         for (i = 0; i < count; i++) {
            if (!mask || mask[i]) {
               dst2[i][RCOMP] = UBYTE_TO_USHORT(src1[i][RCOMP]);
               dst2[i][GCOMP] = UBYTE_TO_USHORT(src1[i][GCOMP]);
               dst2[i][BCOMP] = UBYTE_TO_USHORT(src1[i][BCOMP]);
               dst2[i][ACOMP] = UBYTE_TO_USHORT(src1[i][ACOMP]);
            }
         }
         if (useTemp)
            _mesa_memcpy(dst, tempBuffer, count * 4 * sizeof(GLushort));
      }
      else {
         const GLubyte (*src1)[4] = (const GLubyte (*)[4]) src;
         GLfloat (*dst4)[4] = (GLfloat (*)[4]) (useTemp ? tempBuffer : dst);
         GLuint i;
         ASSERT(dstType == GL_FLOAT);
         for (i = 0; i < count; i++) {
            if (!mask || mask[i]) {
               dst4[i][RCOMP] = UBYTE_TO_FLOAT(src1[i][RCOMP]);
               dst4[i][GCOMP] = UBYTE_TO_FLOAT(src1[i][GCOMP]);
               dst4[i][BCOMP] = UBYTE_TO_FLOAT(src1[i][BCOMP]);
               dst4[i][ACOMP] = UBYTE_TO_FLOAT(src1[i][ACOMP]);
            }
         }
         if (useTemp)
            _mesa_memcpy(dst, tempBuffer, count * 4 * sizeof(GLfloat));
      }
      break;
   case GL_UNSIGNED_SHORT:
      if (dstType == GL_UNSIGNED_BYTE) {
         const GLushort (*src2)[4] = (const GLushort (*)[4]) src;
         GLubyte (*dst1)[4] = (GLubyte (*)[4]) (useTemp ? tempBuffer : dst);
         GLuint i;
         for (i = 0; i < count; i++) {
            if (!mask || mask[i]) {
               dst1[i][RCOMP] = USHORT_TO_UBYTE(src2[i][RCOMP]);
               dst1[i][GCOMP] = USHORT_TO_UBYTE(src2[i][GCOMP]);
               dst1[i][BCOMP] = USHORT_TO_UBYTE(src2[i][BCOMP]);
               dst1[i][ACOMP] = USHORT_TO_UBYTE(src2[i][ACOMP]);
            }
         }
         if (useTemp)
            _mesa_memcpy(dst, tempBuffer, count * 4 * sizeof(GLubyte));
      }
      else {
         const GLushort (*src2)[4] = (const GLushort (*)[4]) src;
         GLfloat (*dst4)[4] = (GLfloat (*)[4]) (useTemp ? tempBuffer : dst);
         GLuint i;
         ASSERT(dstType == GL_FLOAT);
         for (i = 0; i < count; i++) {
            if (!mask || mask[i]) {
               dst4[i][RCOMP] = USHORT_TO_FLOAT(src2[i][RCOMP]);
               dst4[i][GCOMP] = USHORT_TO_FLOAT(src2[i][GCOMP]);
               dst4[i][BCOMP] = USHORT_TO_FLOAT(src2[i][BCOMP]);
               dst4[i][ACOMP] = USHORT_TO_FLOAT(src2[i][ACOMP]);
            }
         }
         if (useTemp)
            _mesa_memcpy(dst, tempBuffer, count * 4 * sizeof(GLfloat));
      }
      break;
   case GL_FLOAT:
      if (dstType == GL_UNSIGNED_BYTE) {
         const GLfloat (*src4)[4] = (const GLfloat (*)[4]) src;
         GLubyte (*dst1)[4] = (GLubyte (*)[4]) (useTemp ? tempBuffer : dst);
         GLuint i;
         for (i = 0; i < count; i++) {
            if (!mask || mask[i]) {
               UNCLAMPED_FLOAT_TO_UBYTE(dst1[i][RCOMP], src4[i][RCOMP]);
               UNCLAMPED_FLOAT_TO_UBYTE(dst1[i][GCOMP], src4[i][GCOMP]);
               UNCLAMPED_FLOAT_TO_UBYTE(dst1[i][BCOMP], src4[i][BCOMP]);
               UNCLAMPED_FLOAT_TO_UBYTE(dst1[i][ACOMP], src4[i][ACOMP]);
            }
         }
         if (useTemp)
            _mesa_memcpy(dst, tempBuffer, count * 4 * sizeof(GLubyte));
      }
      else {
         const GLfloat (*src4)[4] = (const GLfloat (*)[4]) src;
         GLushort (*dst2)[4] = (GLushort (*)[4]) (useTemp ? tempBuffer : dst);
         GLuint i;
         ASSERT(dstType == GL_UNSIGNED_SHORT);
         for (i = 0; i < count; i++) {
            if (!mask || mask[i]) {
               UNCLAMPED_FLOAT_TO_USHORT(dst2[i][RCOMP], src4[i][RCOMP]);
               UNCLAMPED_FLOAT_TO_USHORT(dst2[i][GCOMP], src4[i][GCOMP]);
               UNCLAMPED_FLOAT_TO_USHORT(dst2[i][BCOMP], src4[i][BCOMP]);
               UNCLAMPED_FLOAT_TO_USHORT(dst2[i][ACOMP], src4[i][ACOMP]);
            }
         }
         if (useTemp)
            _mesa_memcpy(dst, tempBuffer, count * 4 * sizeof(GLushort));
      }
      break;
   default:
      _mesa_problem(NULL, "Invalid datatype in _mesa_convert_colors");
   }
}




/**
 * Perform basic clipping for glDrawPixels.  The image's position and size
 * and the unpack SkipPixels and SkipRows are adjusted so that the image
 * region is entirely within the window and scissor bounds.
 * NOTE: this will only work when glPixelZoom is (1, 1) or (1, -1).
 * If Pixel.ZoomY is -1, *destY will be changed to be the first row which
 * we'll actually write.  Beforehand, *destY-1 is the first drawing row.
 *
 * \return  GL_TRUE if image is ready for drawing or
 *          GL_FALSE if image was completely clipped away (draw nothing)
 */
GLboolean
_mesa_clip_drawpixels(const GLcontext *ctx,
                      GLint *destX, GLint *destY,
                      GLsizei *width, GLsizei *height,
                      struct gl_pixelstore_attrib *unpack)
{
   const GLframebuffer *buffer = ctx->DrawBuffer;

   if (unpack->RowLength == 0) {
      unpack->RowLength = *width;
   }

   ASSERT(ctx->Pixel.ZoomX == 1.0F);
   ASSERT(ctx->Pixel.ZoomY == 1.0F || ctx->Pixel.ZoomY == -1.0F);

   /* left clipping */
   if (*destX < buffer->_Xmin) {
      unpack->SkipPixels += (buffer->_Xmin - *destX);
      *width -= (buffer->_Xmin - *destX);
      *destX = buffer->_Xmin;
   }
   /* right clipping */
   if (*destX + *width > buffer->_Xmax)
      *width -= (*destX + *width - buffer->_Xmax);

   if (*width <= 0)
      return GL_FALSE;

   if (ctx->Pixel.ZoomY == 1.0F) {
      /* bottom clipping */
      if (*destY < buffer->_Ymin) {
         unpack->SkipRows += (buffer->_Ymin - *destY);
         *height -= (buffer->_Ymin - *destY);
         *destY = buffer->_Ymin;
      }
      /* top clipping */
      if (*destY + *height > buffer->_Ymax)
         *height -= (*destY + *height - buffer->_Ymax);
   }
   else { /* upside down */
      /* top clipping */
      if (*destY > buffer->_Ymax) {
         unpack->SkipRows += (*destY - buffer->_Ymax);
         *height -= (*destY - buffer->_Ymax);
         *destY = buffer->_Ymax;
      }
      /* bottom clipping */
      if (*destY - *height < buffer->_Ymin)
         *height -= (buffer->_Ymin - (*destY - *height));
      /* adjust destY so it's the first row to write to */
      (*destY)--;
   }

   if (*height <= 0)
      return GL_TRUE;

   return GL_TRUE;
}


/**
 * Perform clipping for glReadPixels.  The image's window position
 * and size, and the pack skipPixels, skipRows and rowLength are adjusted
 * so that the image region is entirely within the window bounds.
 * Note: this is different from _mesa_clip_drawpixels() in that the
 * scissor box is ignored, and we use the bounds of the current readbuffer
 * surface.
 *
 * \return  GL_TRUE if image is ready for drawing or
 *          GL_FALSE if image was completely clipped away (draw nothing)
 */
GLboolean
_mesa_clip_readpixels(const GLcontext *ctx,
                      GLint *srcX, GLint *srcY,
                      GLsizei *width, GLsizei *height,
                      struct gl_pixelstore_attrib *pack)
{
   const GLframebuffer *buffer = ctx->ReadBuffer;

   if (pack->RowLength == 0) {
      pack->RowLength = *width;
   }

   /* left clipping */
   if (*srcX < 0) {
      pack->SkipPixels += (0 - *srcX);
      *width -= (0 - *srcX);
      *srcX = 0;
   }
   /* right clipping */
   if (*srcX + *width > (GLsizei) buffer->Width)
      *width -= (*srcX + *width - buffer->Width);

   if (*width <= 0)
      return GL_FALSE;

   /* bottom clipping */
   if (*srcY < 0) {
      pack->SkipRows += (0 - *srcY);
      *height -= (0 - *srcY);
      *srcY = 0;
   }
   /* top clipping */
   if (*srcY + *height > (GLsizei) buffer->Height)
      *height -= (*srcY + *height - buffer->Height);

   if (*height <= 0)
      return GL_TRUE;

   return GL_TRUE;
}


/**
 * Do clipping for a glCopyTexSubImage call.
 * The framebuffer source region might extend outside the framebuffer
 * bounds.  Clip the source region against the framebuffer bounds and
 * adjust the texture/dest position and size accordingly.
 *
 * \return GL_FALSE if region is totally clipped, GL_TRUE otherwise.
 */
GLboolean
_mesa_clip_copytexsubimage(const GLcontext *ctx,
                           GLint *destX, GLint *destY,
                           GLint *srcX, GLint *srcY,
                           GLsizei *width, GLsizei *height)
{
   const struct gl_framebuffer *fb = ctx->ReadBuffer;
   const GLint srcX0 = *srcX, srcY0 = *srcY;

   if (_mesa_clip_to_region(0, 0, fb->Width, fb->Height,
                            srcX, srcY, width, height)) {
      *destX = *destX + *srcX - srcX0;
      *destY = *destY + *srcY - srcY0;

      return GL_TRUE;
   }
   else {
      return GL_FALSE;
   }
}



/**
 * Clip the rectangle defined by (x, y, width, height) against the bounds
 * specified by [xmin, xmax) and [ymin, ymax).
 * \return GL_FALSE if rect is totally clipped, GL_TRUE otherwise.
 */
GLboolean
_mesa_clip_to_region(GLint xmin, GLint ymin,
                     GLint xmax, GLint ymax,
                     GLint *x, GLint *y,
                     GLsizei *width, GLsizei *height )
{
   /* left clipping */
   if (*x < xmin) {
      *width -= (xmin - *x);
      *x = xmin;
   }

   /* right clipping */
   if (*x + *width > xmax)
      *width -= (*x + *width - xmax);

   if (*width <= 0)
      return GL_FALSE;

   /* bottom (or top) clipping */
   if (*y < ymin) {
      *height -= (ymin - *y);
      *y = ymin;
   }

   /* top (or bottom) clipping */
   if (*y + *height > ymax)
      *height -= (*y + *height - ymax);

   if (*height <= 0)
      return GL_FALSE;

   return GL_TRUE;
}