pngshim.c revision ee451cb395940862dad63c85adfe8f2fd55e864c 
1/***************************************************************************/
2/*                                                                         */
3/*  pngshim.c                                                              */
4/*                                                                         */
5/*    PNG Bitmap glyph support.                                            */
6/*                                                                         */
7/*  Copyright 2013 by Google, Inc.                                         */
8/*  Written by Stuart Gill and Behdad Esfahbod.                            */
9/*                                                                         */
10/*  This file is part of the FreeType project, and may only be used,       */
11/*  modified, and distributed under the terms of the FreeType project      */
12/*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
13/*  this file you indicate that you have read the license and              */
14/*  understand and accept it fully.                                        */
15/*                                                                         */
16/***************************************************************************/
17
18
19#include "../../include/ft2build.h"
20#include "../../include/freetype/internal/ftdebug.h"
21#include "../../include/freetype/internal/ftstream.h"
22#include "../../include/freetype/tttags.h"
23#include "../../include/freetype/config/ftstdlib.h"
24
25
26#ifdef FT_CONFIG_OPTION_USE_PNG
27
28  /* We always include <stjmp.h>, so make libpng shut up! */
29#define PNG_SKIP_SETJMP_CHECK 1
30#include <png.h>
31#include "pngshim.h"
32
33#include "sferrors.h"
34
35
36  /* This code is freely based on cairo-png.c.  There's so many ways */
37  /* to call libpng, and the way cairo does it is defacto standard.  */
38
39  static int
40  multiply_alpha( int  alpha,
41                  int  color )
42  {
43    int  temp = ( alpha * color ) + 0x80;
44
45
46    return ( temp + ( temp >> 8 ) ) >> 8;
47  }
48
49
50  /* Premultiplies data and converts RGBA bytes => native endian. */
51  static void
52  premultiply_data( png_structp    png,
53                    png_row_infop  row_info,
54                    png_bytep      data )
55  {
56    unsigned int  i;
57
58    FT_UNUSED( png );
59
60
61    for ( i = 0; i < row_info->rowbytes; i += 4 )
62    {
63      unsigned char*  base  = &data[i];
64      unsigned int    alpha = base[3];
65
66
67      if ( alpha == 0 )
68        base[0] = base[1] = base[2] = base[3] = 0;
69
70      else
71      {
72        unsigned int  red   = base[0];
73        unsigned int  green = base[1];
74        unsigned int  blue  = base[2];
75
76
77        if ( alpha != 0xFF )
78        {
79          red   = multiply_alpha( alpha, red   );
80          green = multiply_alpha( alpha, green );
81          blue  = multiply_alpha( alpha, blue  );
82        }
83
84        base[0] = blue;
85        base[1] = green;
86        base[2] = red;
87        base[3] = alpha;
88      }
89    }
90  }
91
92
93  /* Converts RGBx bytes to BGRA. */
94  static void
95  convert_bytes_to_data( png_structp    png,
96                         png_row_infop  row_info,
97                         png_bytep      data )
98  {
99    unsigned int  i;
100
101    FT_UNUSED( png );
102
103
104    for ( i = 0; i < row_info->rowbytes; i += 4 )
105    {
106      unsigned char*  base  = &data[i];
107      unsigned int    red   = base[0];
108      unsigned int    green = base[1];
109      unsigned int    blue  = base[2];
110
111
112      base[0] = blue;
113      base[1] = green;
114      base[2] = red;
115      base[3] = 0xFF;
116    }
117  }
118
119
120  /* Use error callback to avoid png writing to stderr. */
121  static void
122  error_callback( png_structp      png,
123                  png_const_charp  error_msg )
124  {
125    FT_Error*  error = png_get_error_ptr( png );
126
127    FT_UNUSED( error_msg );
128
129
130    *error = FT_THROW( Out_Of_Memory );
131#ifdef PNG_SETJMP_SUPPORTED
132    longjmp( png_jmpbuf( png ), 1 );
133#endif
134    /* if we get here, then we have no choice but to abort ... */
135  }
136
137
138  /* Use warning callback to avoid png writing to stderr. */
139  static void
140  warning_callback( png_structp      png,
141                    png_const_charp  error_msg )
142  {
143    FT_UNUSED( png );
144    FT_UNUSED( error_msg );
145
146    /* Just ignore warnings. */
147  }
148
149
150  static void
151  read_data_from_FT_Stream( png_structp  png,
152                            png_bytep    data,
153                            png_size_t   length )
154  {
155    FT_Error   error;
156    png_voidp  p      = png_get_io_ptr( png );
157    FT_Stream  stream = (FT_Stream)p;
158
159
160    if ( FT_FRAME_ENTER( length ) )
161    {
162      FT_Error*  e = png_get_error_ptr( png );
163
164
165      *e = FT_THROW( Invalid_Stream_Read );
166      png_error( png, NULL );
167
168      return;
169    }
170
171    memcpy( data, stream->cursor, length );
172
173    FT_FRAME_EXIT();
174  }
175
176
177  static FT_Error
178  Load_SBit_Png( FT_Bitmap*       map,
179                 FT_Int           x_offset,
180                 FT_Int           y_offset,
181                 FT_Int           pix_bits,
182                 TT_SBit_Metrics  metrics,
183                 FT_Memory        memory,
184                 FT_Byte*         data,
185                 FT_UInt          png_len )
186  {
187    FT_Error      error = FT_Err_Ok;
188    FT_StreamRec  stream;
189
190    png_structp  png;
191    png_infop    info;
192    png_uint_32  imgWidth, imgHeight;
193
194    int         bitdepth, color_type, interlace;
195    FT_Int      i;
196    png_byte*  *rows;
197
198
199    if ( x_offset < 0 || x_offset + metrics->width  > map->width ||
200         y_offset < 0 || y_offset + metrics->height > map->rows  ||
201         pix_bits != 32 || map->pixel_mode != FT_PIXEL_MODE_BGRA )
202    {
203      error = FT_THROW( Invalid_Argument );
204      goto Exit;
205    }
206
207    FT_Stream_OpenMemory( &stream, data, png_len );
208
209    png = png_create_read_struct( PNG_LIBPNG_VER_STRING,
210                                  &error,
211                                  error_callback,
212                                  warning_callback );
213    if ( !png )
214    {
215      error = FT_THROW( Out_Of_Memory );
216      goto Exit;
217    }
218
219    info = png_create_info_struct( png );
220    if ( !info )
221    {
222      error = FT_THROW( Out_Of_Memory );
223      png_destroy_read_struct( &png, NULL, NULL );
224      goto Exit;
225    }
226
227    if ( ft_setjmp( png_jmpbuf( png ) ) )
228    {
229      error = FT_THROW( Invalid_File_Format );
230      goto DestroyExit;
231    }
232
233    png_set_read_fn( png, &stream, read_data_from_FT_Stream );
234
235    png_read_info( png, info );
236    png_get_IHDR( png, info,
237                  &imgWidth, &imgHeight,
238                  &bitdepth, &color_type, &interlace,
239                  NULL, NULL );
240
241    if ( error != FT_Err_Ok                   ||
242         (FT_Int)imgWidth  != metrics->width  ||
243         (FT_Int)imgHeight != metrics->height )
244      goto DestroyExit;
245
246    /* convert palette/gray image to rgb */
247    if ( color_type == PNG_COLOR_TYPE_PALETTE )
248      png_set_palette_to_rgb( png );
249
250    /* expand gray bit depth if needed */
251    if ( color_type == PNG_COLOR_TYPE_GRAY )
252    {
253#if PNG_LIBPNG_VER >= 10209
254      png_set_expand_gray_1_2_4_to_8( png );
255#else
256      png_set_gray_1_2_4_to_8( png );
257#endif
258    }
259
260    /* transform transparency to alpha */
261    if ( png_get_valid(png, info, PNG_INFO_tRNS ) )
262      png_set_tRNS_to_alpha( png );
263
264    if ( bitdepth == 16 )
265      png_set_strip_16( png );
266
267    if ( bitdepth < 8 )
268      png_set_packing( png );
269
270    /* convert grayscale to RGB */
271    if ( color_type == PNG_COLOR_TYPE_GRAY       ||
272         color_type == PNG_COLOR_TYPE_GRAY_ALPHA )
273      png_set_gray_to_rgb( png );
274
275    if ( interlace != PNG_INTERLACE_NONE )
276      png_set_interlace_handling( png );
277
278    png_set_filler( png, 0xFF, PNG_FILLER_AFTER );
279
280    /* recheck header after setting EXPAND options */
281    png_read_update_info(png, info );
282    png_get_IHDR( png, info,
283                  &imgWidth, &imgHeight,
284                  &bitdepth, &color_type, &interlace,
285                  NULL, NULL );
286
287    if ( bitdepth != 8                              ||
288        !( color_type == PNG_COLOR_TYPE_RGB       ||
289           color_type == PNG_COLOR_TYPE_RGB_ALPHA ) )
290    {
291      error = FT_THROW( Invalid_File_Format );
292      goto DestroyExit;
293    }
294
295    switch ( color_type )
296    {
297    default:
298      /* Shouldn't happen, but fall through. */
299
300    case PNG_COLOR_TYPE_RGB_ALPHA:
301      png_set_read_user_transform_fn( png, premultiply_data );
302      break;
303
304    case PNG_COLOR_TYPE_RGB:
305      /* Humm, this smells.  Carry on though. */
306      png_set_read_user_transform_fn( png, convert_bytes_to_data );
307      break;
308    }
309
310    if ( FT_NEW_ARRAY( rows, imgHeight ) )
311    {
312      error = FT_THROW( Out_Of_Memory );
313      goto DestroyExit;
314    }
315
316    for ( i = 0; i < (FT_Int)imgHeight; i++ )
317      rows[i] = map->buffer + ( y_offset + i ) * map->pitch + x_offset * 4;
318
319    png_read_image( png, rows );
320
321    FT_FREE( rows );
322
323    png_read_end( png, info );
324
325  DestroyExit:
326    png_destroy_read_struct( &png, &info, NULL );
327    FT_Stream_Close( &stream );
328
329  Exit:
330    return error;
331  }
332
333#endif /* FT_CONFIG_OPTION_USE_PNG */
334
335
336/* END */
337