1/* 2 * jquant1.c 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1991-1996, Thomas G. Lane. 6 * libjpeg-turbo Modifications: 7 * Copyright (C) 2009, D. R. Commander 8 * For conditions of distribution and use, see the accompanying README file. 9 * 10 * This file contains 1-pass color quantization (color mapping) routines. 11 * These routines provide mapping to a fixed color map using equally spaced 12 * color values. Optional Floyd-Steinberg or ordered dithering is available. 13 */ 14 15#define JPEG_INTERNALS 16#include "jinclude.h" 17#include "jpeglib.h" 18 19#ifdef QUANT_1PASS_SUPPORTED 20 21 22/* 23 * The main purpose of 1-pass quantization is to provide a fast, if not very 24 * high quality, colormapped output capability. A 2-pass quantizer usually 25 * gives better visual quality; however, for quantized grayscale output this 26 * quantizer is perfectly adequate. Dithering is highly recommended with this 27 * quantizer, though you can turn it off if you really want to. 28 * 29 * In 1-pass quantization the colormap must be chosen in advance of seeing the 30 * image. We use a map consisting of all combinations of Ncolors[i] color 31 * values for the i'th component. The Ncolors[] values are chosen so that 32 * their product, the total number of colors, is no more than that requested. 33 * (In most cases, the product will be somewhat less.) 34 * 35 * Since the colormap is orthogonal, the representative value for each color 36 * component can be determined without considering the other components; 37 * then these indexes can be combined into a colormap index by a standard 38 * N-dimensional-array-subscript calculation. Most of the arithmetic involved 39 * can be precalculated and stored in the lookup table colorindex[]. 40 * colorindex[i][j] maps pixel value j in component i to the nearest 41 * representative value (grid plane) for that component; this index is 42 * multiplied by the array stride for component i, so that the 43 * index of the colormap entry closest to a given pixel value is just 44 * sum( colorindex[component-number][pixel-component-value] ) 45 * Aside from being fast, this scheme allows for variable spacing between 46 * representative values with no additional lookup cost. 47 * 48 * If gamma correction has been applied in color conversion, it might be wise 49 * to adjust the color grid spacing so that the representative colors are 50 * equidistant in linear space. At this writing, gamma correction is not 51 * implemented by jdcolor, so nothing is done here. 52 */ 53 54 55/* Declarations for ordered dithering. 56 * 57 * We use a standard 16x16 ordered dither array. The basic concept of ordered 58 * dithering is described in many references, for instance Dale Schumacher's 59 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991). 60 * In place of Schumacher's comparisons against a "threshold" value, we add a 61 * "dither" value to the input pixel and then round the result to the nearest 62 * output value. The dither value is equivalent to (0.5 - threshold) times 63 * the distance between output values. For ordered dithering, we assume that 64 * the output colors are equally spaced; if not, results will probably be 65 * worse, since the dither may be too much or too little at a given point. 66 * 67 * The normal calculation would be to form pixel value + dither, range-limit 68 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual. 69 * We can skip the separate range-limiting step by extending the colorindex 70 * table in both directions. 71 */ 72 73#define ODITHER_SIZE 16 /* dimension of dither matrix */ 74/* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */ 75#define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */ 76#define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */ 77 78typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE]; 79typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE]; 80 81static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = { 82 /* Bayer's order-4 dither array. Generated by the code given in 83 * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I. 84 * The values in this array must range from 0 to ODITHER_CELLS-1. 85 */ 86 { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 }, 87 { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 }, 88 { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 }, 89 { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 }, 90 { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 }, 91 { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 }, 92 { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 }, 93 { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 }, 94 { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 }, 95 { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 }, 96 { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 }, 97 { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 }, 98 { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 }, 99 { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 }, 100 { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 }, 101 { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 } 102}; 103 104 105/* Declarations for Floyd-Steinberg dithering. 106 * 107 * Errors are accumulated into the array fserrors[], at a resolution of 108 * 1/16th of a pixel count. The error at a given pixel is propagated 109 * to its not-yet-processed neighbors using the standard F-S fractions, 110 * ... (here) 7/16 111 * 3/16 5/16 1/16 112 * We work left-to-right on even rows, right-to-left on odd rows. 113 * 114 * We can get away with a single array (holding one row's worth of errors) 115 * by using it to store the current row's errors at pixel columns not yet 116 * processed, but the next row's errors at columns already processed. We 117 * need only a few extra variables to hold the errors immediately around the 118 * current column. (If we are lucky, those variables are in registers, but 119 * even if not, they're probably cheaper to access than array elements are.) 120 * 121 * The fserrors[] array is indexed [component#][position]. 122 * We provide (#columns + 2) entries per component; the extra entry at each 123 * end saves us from special-casing the first and last pixels. 124 * 125 * Note: on a wide image, we might not have enough room in a PC's near data 126 * segment to hold the error array; so it is allocated with alloc_large. 127 */ 128 129#if BITS_IN_JSAMPLE == 8 130typedef INT16 FSERROR; /* 16 bits should be enough */ 131typedef int LOCFSERROR; /* use 'int' for calculation temps */ 132#else 133typedef INT32 FSERROR; /* may need more than 16 bits */ 134typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */ 135#endif 136 137typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */ 138 139 140/* Private subobject */ 141 142#define MAX_Q_COMPS 4 /* max components I can handle */ 143 144typedef struct { 145 struct jpeg_color_quantizer pub; /* public fields */ 146 147 /* Initially allocated colormap is saved here */ 148 JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */ 149 int sv_actual; /* number of entries in use */ 150 151 JSAMPARRAY colorindex; /* Precomputed mapping for speed */ 152 /* colorindex[i][j] = index of color closest to pixel value j in component i, 153 * premultiplied as described above. Since colormap indexes must fit into 154 * JSAMPLEs, the entries of this array will too. 155 */ 156 boolean is_padded; /* is the colorindex padded for odither? */ 157 158 int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */ 159 160 /* Variables for ordered dithering */ 161 int row_index; /* cur row's vertical index in dither matrix */ 162 ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */ 163 164 /* Variables for Floyd-Steinberg dithering */ 165 FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */ 166 boolean on_odd_row; /* flag to remember which row we are on */ 167} my_cquantizer; 168 169typedef my_cquantizer * my_cquantize_ptr; 170 171 172/* 173 * Policy-making subroutines for create_colormap and create_colorindex. 174 * These routines determine the colormap to be used. The rest of the module 175 * only assumes that the colormap is orthogonal. 176 * 177 * * select_ncolors decides how to divvy up the available colors 178 * among the components. 179 * * output_value defines the set of representative values for a component. 180 * * largest_input_value defines the mapping from input values to 181 * representative values for a component. 182 * Note that the latter two routines may impose different policies for 183 * different components, though this is not currently done. 184 */ 185 186 187LOCAL(int) 188select_ncolors (j_decompress_ptr cinfo, int Ncolors[]) 189/* Determine allocation of desired colors to components, */ 190/* and fill in Ncolors[] array to indicate choice. */ 191/* Return value is total number of colors (product of Ncolors[] values). */ 192{ 193 int nc = cinfo->out_color_components; /* number of color components */ 194 int max_colors = cinfo->desired_number_of_colors; 195 int total_colors, iroot, i, j; 196 boolean changed; 197 long temp; 198 int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE }; 199 RGB_order[0] = rgb_green[cinfo->out_color_space]; 200 RGB_order[1] = rgb_red[cinfo->out_color_space]; 201 RGB_order[2] = rgb_blue[cinfo->out_color_space]; 202 203 /* We can allocate at least the nc'th root of max_colors per component. */ 204 /* Compute floor(nc'th root of max_colors). */ 205 iroot = 1; 206 do { 207 iroot++; 208 temp = iroot; /* set temp = iroot ** nc */ 209 for (i = 1; i < nc; i++) 210 temp *= iroot; 211 } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */ 212 iroot--; /* now iroot = floor(root) */ 213 214 /* Must have at least 2 color values per component */ 215 if (iroot < 2) 216 ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp); 217 218 /* Initialize to iroot color values for each component */ 219 total_colors = 1; 220 for (i = 0; i < nc; i++) { 221 Ncolors[i] = iroot; 222 total_colors *= iroot; 223 } 224 /* We may be able to increment the count for one or more components without 225 * exceeding max_colors, though we know not all can be incremented. 226 * Sometimes, the first component can be incremented more than once! 227 * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.) 228 * In RGB colorspace, try to increment G first, then R, then B. 229 */ 230 do { 231 changed = FALSE; 232 for (i = 0; i < nc; i++) { 233 j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i); 234 /* calculate new total_colors if Ncolors[j] is incremented */ 235 temp = total_colors / Ncolors[j]; 236 temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */ 237 if (temp > (long) max_colors) 238 break; /* won't fit, done with this pass */ 239 Ncolors[j]++; /* OK, apply the increment */ 240 total_colors = (int) temp; 241 changed = TRUE; 242 } 243 } while (changed); 244 245 return total_colors; 246} 247 248 249LOCAL(int) 250output_value (j_decompress_ptr cinfo, int ci, int j, int maxj) 251/* Return j'th output value, where j will range from 0 to maxj */ 252/* The output values must fall in 0..MAXJSAMPLE in increasing order */ 253{ 254 /* We always provide values 0 and MAXJSAMPLE for each component; 255 * any additional values are equally spaced between these limits. 256 * (Forcing the upper and lower values to the limits ensures that 257 * dithering can't produce a color outside the selected gamut.) 258 */ 259 return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj); 260} 261 262 263LOCAL(int) 264largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj) 265/* Return largest input value that should map to j'th output value */ 266/* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */ 267{ 268 /* Breakpoints are halfway between values returned by output_value */ 269 return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj)); 270} 271 272 273/* 274 * Create the colormap. 275 */ 276 277LOCAL(void) 278create_colormap (j_decompress_ptr cinfo) 279{ 280 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 281 JSAMPARRAY colormap; /* Created colormap */ 282 int total_colors; /* Number of distinct output colors */ 283 int i,j,k, nci, blksize, blkdist, ptr, val; 284 285 /* Select number of colors for each component */ 286 total_colors = select_ncolors(cinfo, cquantize->Ncolors); 287 288 /* Report selected color counts */ 289 if (cinfo->out_color_components == 3) 290 TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS, 291 total_colors, cquantize->Ncolors[0], 292 cquantize->Ncolors[1], cquantize->Ncolors[2]); 293 else 294 TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors); 295 296 /* Allocate and fill in the colormap. */ 297 /* The colors are ordered in the map in standard row-major order, */ 298 /* i.e. rightmost (highest-indexed) color changes most rapidly. */ 299 300 colormap = (*cinfo->mem->alloc_sarray) 301 ((j_common_ptr) cinfo, JPOOL_IMAGE, 302 (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components); 303 304 /* blksize is number of adjacent repeated entries for a component */ 305 /* blkdist is distance between groups of identical entries for a component */ 306 blkdist = total_colors; 307 308 for (i = 0; i < cinfo->out_color_components; i++) { 309 /* fill in colormap entries for i'th color component */ 310 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 311 blksize = blkdist / nci; 312 for (j = 0; j < nci; j++) { 313 /* Compute j'th output value (out of nci) for component */ 314 val = output_value(cinfo, i, j, nci-1); 315 /* Fill in all colormap entries that have this value of this component */ 316 for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) { 317 /* fill in blksize entries beginning at ptr */ 318 for (k = 0; k < blksize; k++) 319 colormap[i][ptr+k] = (JSAMPLE) val; 320 } 321 } 322 blkdist = blksize; /* blksize of this color is blkdist of next */ 323 } 324 325 /* Save the colormap in private storage, 326 * where it will survive color quantization mode changes. 327 */ 328 cquantize->sv_colormap = colormap; 329 cquantize->sv_actual = total_colors; 330} 331 332 333/* 334 * Create the color index table. 335 */ 336 337LOCAL(void) 338create_colorindex (j_decompress_ptr cinfo) 339{ 340 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 341 JSAMPROW indexptr; 342 int i,j,k, nci, blksize, val, pad; 343 344 /* For ordered dither, we pad the color index tables by MAXJSAMPLE in 345 * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE). 346 * This is not necessary in the other dithering modes. However, we 347 * flag whether it was done in case user changes dithering mode. 348 */ 349 if (cinfo->dither_mode == JDITHER_ORDERED) { 350 pad = MAXJSAMPLE*2; 351 cquantize->is_padded = TRUE; 352 } else { 353 pad = 0; 354 cquantize->is_padded = FALSE; 355 } 356 357 cquantize->colorindex = (*cinfo->mem->alloc_sarray) 358 ((j_common_ptr) cinfo, JPOOL_IMAGE, 359 (JDIMENSION) (MAXJSAMPLE+1 + pad), 360 (JDIMENSION) cinfo->out_color_components); 361 362 /* blksize is number of adjacent repeated entries for a component */ 363 blksize = cquantize->sv_actual; 364 365 for (i = 0; i < cinfo->out_color_components; i++) { 366 /* fill in colorindex entries for i'th color component */ 367 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 368 blksize = blksize / nci; 369 370 /* adjust colorindex pointers to provide padding at negative indexes. */ 371 if (pad) 372 cquantize->colorindex[i] += MAXJSAMPLE; 373 374 /* in loop, val = index of current output value, */ 375 /* and k = largest j that maps to current val */ 376 indexptr = cquantize->colorindex[i]; 377 val = 0; 378 k = largest_input_value(cinfo, i, 0, nci-1); 379 for (j = 0; j <= MAXJSAMPLE; j++) { 380 while (j > k) /* advance val if past boundary */ 381 k = largest_input_value(cinfo, i, ++val, nci-1); 382 /* premultiply so that no multiplication needed in main processing */ 383 indexptr[j] = (JSAMPLE) (val * blksize); 384 } 385 /* Pad at both ends if necessary */ 386 if (pad) 387 for (j = 1; j <= MAXJSAMPLE; j++) { 388 indexptr[-j] = indexptr[0]; 389 indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE]; 390 } 391 } 392} 393 394 395/* 396 * Create an ordered-dither array for a component having ncolors 397 * distinct output values. 398 */ 399 400LOCAL(ODITHER_MATRIX_PTR) 401make_odither_array (j_decompress_ptr cinfo, int ncolors) 402{ 403 ODITHER_MATRIX_PTR odither; 404 int j,k; 405 INT32 num,den; 406 407 odither = (ODITHER_MATRIX_PTR) 408 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 409 SIZEOF(ODITHER_MATRIX)); 410 /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1). 411 * Hence the dither value for the matrix cell with fill order f 412 * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1). 413 * On 16-bit-int machine, be careful to avoid overflow. 414 */ 415 den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1)); 416 for (j = 0; j < ODITHER_SIZE; j++) { 417 for (k = 0; k < ODITHER_SIZE; k++) { 418 num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k]))) 419 * MAXJSAMPLE; 420 /* Ensure round towards zero despite C's lack of consistency 421 * about rounding negative values in integer division... 422 */ 423 odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den); 424 } 425 } 426 return odither; 427} 428 429 430/* 431 * Create the ordered-dither tables. 432 * Components having the same number of representative colors may 433 * share a dither table. 434 */ 435 436LOCAL(void) 437create_odither_tables (j_decompress_ptr cinfo) 438{ 439 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 440 ODITHER_MATRIX_PTR odither; 441 int i, j, nci; 442 443 for (i = 0; i < cinfo->out_color_components; i++) { 444 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 445 odither = NULL; /* search for matching prior component */ 446 for (j = 0; j < i; j++) { 447 if (nci == cquantize->Ncolors[j]) { 448 odither = cquantize->odither[j]; 449 break; 450 } 451 } 452 if (odither == NULL) /* need a new table? */ 453 odither = make_odither_array(cinfo, nci); 454 cquantize->odither[i] = odither; 455 } 456} 457 458 459/* 460 * Map some rows of pixels to the output colormapped representation. 461 */ 462 463METHODDEF(void) 464color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 465 JSAMPARRAY output_buf, int num_rows) 466/* General case, no dithering */ 467{ 468 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 469 JSAMPARRAY colorindex = cquantize->colorindex; 470 register int pixcode, ci; 471 register JSAMPROW ptrin, ptrout; 472 int row; 473 JDIMENSION col; 474 JDIMENSION width = cinfo->output_width; 475 register int nc = cinfo->out_color_components; 476 477 for (row = 0; row < num_rows; row++) { 478 ptrin = input_buf[row]; 479 ptrout = output_buf[row]; 480 for (col = width; col > 0; col--) { 481 pixcode = 0; 482 for (ci = 0; ci < nc; ci++) { 483 pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]); 484 } 485 *ptrout++ = (JSAMPLE) pixcode; 486 } 487 } 488} 489 490 491METHODDEF(void) 492color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 493 JSAMPARRAY output_buf, int num_rows) 494/* Fast path for out_color_components==3, no dithering */ 495{ 496 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 497 register int pixcode; 498 register JSAMPROW ptrin, ptrout; 499 JSAMPROW colorindex0 = cquantize->colorindex[0]; 500 JSAMPROW colorindex1 = cquantize->colorindex[1]; 501 JSAMPROW colorindex2 = cquantize->colorindex[2]; 502 int row; 503 JDIMENSION col; 504 JDIMENSION width = cinfo->output_width; 505 506 for (row = 0; row < num_rows; row++) { 507 ptrin = input_buf[row]; 508 ptrout = output_buf[row]; 509 for (col = width; col > 0; col--) { 510 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]); 511 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]); 512 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]); 513 *ptrout++ = (JSAMPLE) pixcode; 514 } 515 } 516} 517 518 519METHODDEF(void) 520quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 521 JSAMPARRAY output_buf, int num_rows) 522/* General case, with ordered dithering */ 523{ 524 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 525 register JSAMPROW input_ptr; 526 register JSAMPROW output_ptr; 527 JSAMPROW colorindex_ci; 528 int * dither; /* points to active row of dither matrix */ 529 int row_index, col_index; /* current indexes into dither matrix */ 530 int nc = cinfo->out_color_components; 531 int ci; 532 int row; 533 JDIMENSION col; 534 JDIMENSION width = cinfo->output_width; 535 536 for (row = 0; row < num_rows; row++) { 537 /* Initialize output values to 0 so can process components separately */ 538 jzero_far((void FAR *) output_buf[row], 539 (size_t) (width * SIZEOF(JSAMPLE))); 540 row_index = cquantize->row_index; 541 for (ci = 0; ci < nc; ci++) { 542 input_ptr = input_buf[row] + ci; 543 output_ptr = output_buf[row]; 544 colorindex_ci = cquantize->colorindex[ci]; 545 dither = cquantize->odither[ci][row_index]; 546 col_index = 0; 547 548 for (col = width; col > 0; col--) { 549 /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE, 550 * select output value, accumulate into output code for this pixel. 551 * Range-limiting need not be done explicitly, as we have extended 552 * the colorindex table to produce the right answers for out-of-range 553 * inputs. The maximum dither is +- MAXJSAMPLE; this sets the 554 * required amount of padding. 555 */ 556 *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]]; 557 input_ptr += nc; 558 output_ptr++; 559 col_index = (col_index + 1) & ODITHER_MASK; 560 } 561 } 562 /* Advance row index for next row */ 563 row_index = (row_index + 1) & ODITHER_MASK; 564 cquantize->row_index = row_index; 565 } 566} 567 568 569METHODDEF(void) 570quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 571 JSAMPARRAY output_buf, int num_rows) 572/* Fast path for out_color_components==3, with ordered dithering */ 573{ 574 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 575 register int pixcode; 576 register JSAMPROW input_ptr; 577 register JSAMPROW output_ptr; 578 JSAMPROW colorindex0 = cquantize->colorindex[0]; 579 JSAMPROW colorindex1 = cquantize->colorindex[1]; 580 JSAMPROW colorindex2 = cquantize->colorindex[2]; 581 int * dither0; /* points to active row of dither matrix */ 582 int * dither1; 583 int * dither2; 584 int row_index, col_index; /* current indexes into dither matrix */ 585 int row; 586 JDIMENSION col; 587 JDIMENSION width = cinfo->output_width; 588 589 for (row = 0; row < num_rows; row++) { 590 row_index = cquantize->row_index; 591 input_ptr = input_buf[row]; 592 output_ptr = output_buf[row]; 593 dither0 = cquantize->odither[0][row_index]; 594 dither1 = cquantize->odither[1][row_index]; 595 dither2 = cquantize->odither[2][row_index]; 596 col_index = 0; 597 598 for (col = width; col > 0; col--) { 599 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) + 600 dither0[col_index]]); 601 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) + 602 dither1[col_index]]); 603 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) + 604 dither2[col_index]]); 605 *output_ptr++ = (JSAMPLE) pixcode; 606 col_index = (col_index + 1) & ODITHER_MASK; 607 } 608 row_index = (row_index + 1) & ODITHER_MASK; 609 cquantize->row_index = row_index; 610 } 611} 612 613 614METHODDEF(void) 615quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 616 JSAMPARRAY output_buf, int num_rows) 617/* General case, with Floyd-Steinberg dithering */ 618{ 619 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 620 register LOCFSERROR cur; /* current error or pixel value */ 621 LOCFSERROR belowerr; /* error for pixel below cur */ 622 LOCFSERROR bpreverr; /* error for below/prev col */ 623 LOCFSERROR bnexterr; /* error for below/next col */ 624 LOCFSERROR delta; 625 register FSERRPTR errorptr; /* => fserrors[] at column before current */ 626 register JSAMPROW input_ptr; 627 register JSAMPROW output_ptr; 628 JSAMPROW colorindex_ci; 629 JSAMPROW colormap_ci; 630 int pixcode; 631 int nc = cinfo->out_color_components; 632 int dir; /* 1 for left-to-right, -1 for right-to-left */ 633 int dirnc; /* dir * nc */ 634 int ci; 635 int row; 636 JDIMENSION col; 637 JDIMENSION width = cinfo->output_width; 638 JSAMPLE *range_limit = cinfo->sample_range_limit; 639 SHIFT_TEMPS 640 641 for (row = 0; row < num_rows; row++) { 642 /* Initialize output values to 0 so can process components separately */ 643 jzero_far((void FAR *) output_buf[row], 644 (size_t) (width * SIZEOF(JSAMPLE))); 645 for (ci = 0; ci < nc; ci++) { 646 input_ptr = input_buf[row] + ci; 647 output_ptr = output_buf[row]; 648 if (cquantize->on_odd_row) { 649 /* work right to left in this row */ 650 input_ptr += (width-1) * nc; /* so point to rightmost pixel */ 651 output_ptr += width-1; 652 dir = -1; 653 dirnc = -nc; 654 errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */ 655 } else { 656 /* work left to right in this row */ 657 dir = 1; 658 dirnc = nc; 659 errorptr = cquantize->fserrors[ci]; /* => entry before first column */ 660 } 661 colorindex_ci = cquantize->colorindex[ci]; 662 colormap_ci = cquantize->sv_colormap[ci]; 663 /* Preset error values: no error propagated to first pixel from left */ 664 cur = 0; 665 /* and no error propagated to row below yet */ 666 belowerr = bpreverr = 0; 667 668 for (col = width; col > 0; col--) { 669 /* cur holds the error propagated from the previous pixel on the 670 * current line. Add the error propagated from the previous line 671 * to form the complete error correction term for this pixel, and 672 * round the error term (which is expressed * 16) to an integer. 673 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct 674 * for either sign of the error value. 675 * Note: errorptr points to *previous* column's array entry. 676 */ 677 cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4); 678 /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE. 679 * The maximum error is +- MAXJSAMPLE; this sets the required size 680 * of the range_limit array. 681 */ 682 cur += GETJSAMPLE(*input_ptr); 683 cur = GETJSAMPLE(range_limit[cur]); 684 /* Select output value, accumulate into output code for this pixel */ 685 pixcode = GETJSAMPLE(colorindex_ci[cur]); 686 *output_ptr += (JSAMPLE) pixcode; 687 /* Compute actual representation error at this pixel */ 688 /* Note: we can do this even though we don't have the final */ 689 /* pixel code, because the colormap is orthogonal. */ 690 cur -= GETJSAMPLE(colormap_ci[pixcode]); 691 /* Compute error fractions to be propagated to adjacent pixels. 692 * Add these into the running sums, and simultaneously shift the 693 * next-line error sums left by 1 column. 694 */ 695 bnexterr = cur; 696 delta = cur * 2; 697 cur += delta; /* form error * 3 */ 698 errorptr[0] = (FSERROR) (bpreverr + cur); 699 cur += delta; /* form error * 5 */ 700 bpreverr = belowerr + cur; 701 belowerr = bnexterr; 702 cur += delta; /* form error * 7 */ 703 /* At this point cur contains the 7/16 error value to be propagated 704 * to the next pixel on the current line, and all the errors for the 705 * next line have been shifted over. We are therefore ready to move on. 706 */ 707 input_ptr += dirnc; /* advance input ptr to next column */ 708 output_ptr += dir; /* advance output ptr to next column */ 709 errorptr += dir; /* advance errorptr to current column */ 710 } 711 /* Post-loop cleanup: we must unload the final error value into the 712 * final fserrors[] entry. Note we need not unload belowerr because 713 * it is for the dummy column before or after the actual array. 714 */ 715 errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */ 716 } 717 cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE); 718 } 719} 720 721 722/* 723 * Allocate workspace for Floyd-Steinberg errors. 724 */ 725 726LOCAL(void) 727alloc_fs_workspace (j_decompress_ptr cinfo) 728{ 729 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 730 size_t arraysize; 731 int i; 732 733 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); 734 for (i = 0; i < cinfo->out_color_components; i++) { 735 cquantize->fserrors[i] = (FSERRPTR) 736 (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize); 737 } 738} 739 740 741/* 742 * Initialize for one-pass color quantization. 743 */ 744 745METHODDEF(void) 746start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan) 747{ 748 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 749 size_t arraysize; 750 int i; 751 752 /* Install my colormap. */ 753 cinfo->colormap = cquantize->sv_colormap; 754 cinfo->actual_number_of_colors = cquantize->sv_actual; 755 756 /* Initialize for desired dithering mode. */ 757 switch (cinfo->dither_mode) { 758 case JDITHER_NONE: 759 if (cinfo->out_color_components == 3) 760 cquantize->pub.color_quantize = color_quantize3; 761 else 762 cquantize->pub.color_quantize = color_quantize; 763 break; 764 case JDITHER_ORDERED: 765 if (cinfo->out_color_components == 3) 766 cquantize->pub.color_quantize = quantize3_ord_dither; 767 else 768 cquantize->pub.color_quantize = quantize_ord_dither; 769 cquantize->row_index = 0; /* initialize state for ordered dither */ 770 /* If user changed to ordered dither from another mode, 771 * we must recreate the color index table with padding. 772 * This will cost extra space, but probably isn't very likely. 773 */ 774 if (! cquantize->is_padded) 775 create_colorindex(cinfo); 776 /* Create ordered-dither tables if we didn't already. */ 777 if (cquantize->odither[0] == NULL) 778 create_odither_tables(cinfo); 779 break; 780 case JDITHER_FS: 781 cquantize->pub.color_quantize = quantize_fs_dither; 782 cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */ 783 /* Allocate Floyd-Steinberg workspace if didn't already. */ 784 if (cquantize->fserrors[0] == NULL) 785 alloc_fs_workspace(cinfo); 786 /* Initialize the propagated errors to zero. */ 787 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); 788 for (i = 0; i < cinfo->out_color_components; i++) 789 jzero_far((void FAR *) cquantize->fserrors[i], arraysize); 790 break; 791 default: 792 ERREXIT(cinfo, JERR_NOT_COMPILED); 793 break; 794 } 795} 796 797 798/* 799 * Finish up at the end of the pass. 800 */ 801 802METHODDEF(void) 803finish_pass_1_quant (j_decompress_ptr cinfo) 804{ 805 /* no work in 1-pass case */ 806} 807 808 809/* 810 * Switch to a new external colormap between output passes. 811 * Shouldn't get to this module! 812 */ 813 814METHODDEF(void) 815new_color_map_1_quant (j_decompress_ptr cinfo) 816{ 817 ERREXIT(cinfo, JERR_MODE_CHANGE); 818} 819 820 821/* 822 * Module initialization routine for 1-pass color quantization. 823 */ 824 825GLOBAL(void) 826jinit_1pass_quantizer (j_decompress_ptr cinfo) 827{ 828 my_cquantize_ptr cquantize; 829 830 cquantize = (my_cquantize_ptr) 831 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 832 SIZEOF(my_cquantizer)); 833 cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize; 834 cquantize->pub.start_pass = start_pass_1_quant; 835 cquantize->pub.finish_pass = finish_pass_1_quant; 836 cquantize->pub.new_color_map = new_color_map_1_quant; 837 cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */ 838 cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */ 839 840 /* Make sure my internal arrays won't overflow */ 841 if (cinfo->out_color_components > MAX_Q_COMPS) 842 ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS); 843 /* Make sure colormap indexes can be represented by JSAMPLEs */ 844 if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1)) 845 ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1); 846 847 /* Create the colormap and color index table. */ 848 create_colormap(cinfo); 849 create_colorindex(cinfo); 850 851 /* Allocate Floyd-Steinberg workspace now if requested. 852 * We do this now since it is FAR storage and may affect the memory 853 * manager's space calculations. If the user changes to FS dither 854 * mode in a later pass, we will allocate the space then, and will 855 * possibly overrun the max_memory_to_use setting. 856 */ 857 if (cinfo->dither_mode == JDITHER_FS) 858 alloc_fs_workspace(cinfo); 859} 860 861#endif /* QUANT_1PASS_SUPPORTED */ 862