1 /* 2 * jquant1.c 3 * 4 * Copyright (C) 1991-1996, Thomas G. Lane. 5 * Modified 2011 by Guido Vollbeding. 6 * This file is part of the Independent JPEG Group's software. 7 * For conditions of distribution and use, see the accompanying README file. 8 * 9 * This file contains 1-pass color quantization (color mapping) routines. 10 * These routines provide mapping to a fixed color map using equally spaced 11 * color values. Optional Floyd-Steinberg or ordered dithering is available. 12 */ 13 14 #define JPEG_INTERNALS 15 #include "jinclude.h" 16 #include "jpeglib.h" 17 18 #ifdef QUANT_1PASS_SUPPORTED 19 20 21 /* 22 * The main purpose of 1-pass quantization is to provide a fast, if not very 23 * high quality, colormapped output capability. A 2-pass quantizer usually 24 * gives better visual quality; however, for quantized grayscale output this 25 * quantizer is perfectly adequate. Dithering is highly recommended with this 26 * quantizer, though you can turn it off if you really want to. 27 * 28 * In 1-pass quantization the colormap must be chosen in advance of seeing the 29 * image. We use a map consisting of all combinations of Ncolors[i] color 30 * values for the i'th component. The Ncolors[] values are chosen so that 31 * their product, the total number of colors, is no more than that requested. 32 * (In most cases, the product will be somewhat less.) 33 * 34 * Since the colormap is orthogonal, the representative value for each color 35 * component can be determined without considering the other components; 36 * then these indexes can be combined into a colormap index by a standard 37 * N-dimensional-array-subscript calculation. Most of the arithmetic involved 38 * can be precalculated and stored in the lookup table colorindex[]. 39 * colorindex[i][j] maps pixel value j in component i to the nearest 40 * representative value (grid plane) for that component; this index is 41 * multiplied by the array stride for component i, so that the 42 * index of the colormap entry closest to a given pixel value is just 43 * sum( colorindex[component-number][pixel-component-value] ) 44 * Aside from being fast, this scheme allows for variable spacing between 45 * representative values with no additional lookup cost. 46 * 47 * If gamma correction has been applied in color conversion, it might be wise 48 * to adjust the color grid spacing so that the representative colors are 49 * equidistant in linear space. At this writing, gamma correction is not 50 * implemented by jdcolor, so nothing is done here. 51 */ 52 53 54 /* Declarations for ordered dithering. 55 * 56 * We use a standard 16x16 ordered dither array. The basic concept of ordered 57 * dithering is described in many references, for instance Dale Schumacher's 58 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991). 59 * In place of Schumacher's comparisons against a "threshold" value, we add a 60 * "dither" value to the input pixel and then round the result to the nearest 61 * output value. The dither value is equivalent to (0.5 - threshold) times 62 * the distance between output values. For ordered dithering, we assume that 63 * the output colors are equally spaced; if not, results will probably be 64 * worse, since the dither may be too much or too little at a given point. 65 * 66 * The normal calculation would be to form pixel value + dither, range-limit 67 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual. 68 * We can skip the separate range-limiting step by extending the colorindex 69 * table in both directions. 70 */ 71 72 #define ODITHER_SIZE 16 /* dimension of dither matrix */ 73 /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */ 74 #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */ 75 #define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */ 76 77 typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE]; 78 typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE]; 79 80 static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = { 81 /* Bayer's order-4 dither array. Generated by the code given in 82 * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I. 83 * The values in this array must range from 0 to ODITHER_CELLS-1. 84 */ 85 { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 }, 86 { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 }, 87 { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 }, 88 { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 }, 89 { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 }, 90 { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 }, 91 { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 }, 92 { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 }, 93 { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 }, 94 { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 }, 95 { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 }, 96 { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 }, 97 { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 }, 98 { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 }, 99 { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 }, 100 { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 } 101 }; 102 103 104 /* Declarations for Floyd-Steinberg dithering. 105 * 106 * Errors are accumulated into the array fserrors[], at a resolution of 107 * 1/16th of a pixel count. The error at a given pixel is propagated 108 * to its not-yet-processed neighbors using the standard F-S fractions, 109 * ... (here) 7/16 110 * 3/16 5/16 1/16 111 * We work left-to-right on even rows, right-to-left on odd rows. 112 * 113 * We can get away with a single array (holding one row's worth of errors) 114 * by using it to store the current row's errors at pixel columns not yet 115 * processed, but the next row's errors at columns already processed. We 116 * need only a few extra variables to hold the errors immediately around the 117 * current column. (If we are lucky, those variables are in registers, but 118 * even if not, they're probably cheaper to access than array elements are.) 119 * 120 * The fserrors[] array is indexed [component#][position]. 121 * We provide (#columns + 2) entries per component; the extra entry at each 122 * end saves us from special-casing the first and last pixels. 123 * 124 * Note: on a wide image, we might not have enough room in a PC's near data 125 * segment to hold the error array; so it is allocated with alloc_large. 126 */ 127 128 #if BITS_IN_JSAMPLE == 8 129 typedef INT16 FSERROR; /* 16 bits should be enough */ 130 typedef int LOCFSERROR; /* use 'int' for calculation temps */ 131 #else 132 typedef INT32 FSERROR; /* may need more than 16 bits */ 133 typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */ 134 #endif 135 136 typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */ 137 138 139 /* Private subobject */ 140 141 #define MAX_Q_COMPS 4 /* max components I can handle */ 142 143 typedef struct { 144 struct jpeg_color_quantizer pub; /* public fields */ 145 146 /* Initially allocated colormap is saved here */ 147 JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */ 148 int sv_actual; /* number of entries in use */ 149 150 JSAMPARRAY colorindex; /* Precomputed mapping for speed */ 151 /* colorindex[i][j] = index of color closest to pixel value j in component i, 152 * premultiplied as described above. Since colormap indexes must fit into 153 * JSAMPLEs, the entries of this array will too. 154 */ 155 boolean is_padded; /* is the colorindex padded for odither? */ 156 157 int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */ 158 159 /* Variables for ordered dithering */ 160 int row_index; /* cur row's vertical index in dither matrix */ 161 ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */ 162 163 /* Variables for Floyd-Steinberg dithering */ 164 FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */ 165 boolean on_odd_row; /* flag to remember which row we are on */ 166 } my_cquantizer; 167 168 typedef my_cquantizer * my_cquantize_ptr; 169 170 171 /* 172 * Policy-making subroutines for create_colormap and create_colorindex. 173 * These routines determine the colormap to be used. The rest of the module 174 * only assumes that the colormap is orthogonal. 175 * 176 * * select_ncolors decides how to divvy up the available colors 177 * among the components. 178 * * output_value defines the set of representative values for a component. 179 * * largest_input_value defines the mapping from input values to 180 * representative values for a component. 181 * Note that the latter two routines may impose different policies for 182 * different components, though this is not currently done. 183 */ 184 185 186 LOCAL(int) 187 select_ncolors (j_decompress_ptr cinfo, int Ncolors[]) 188 /* Determine allocation of desired colors to components, */ 189 /* and fill in Ncolors[] array to indicate choice. */ 190 /* Return value is total number of colors (product of Ncolors[] values). */ 191 { 192 int nc = cinfo->out_color_components; /* number of color components */ 193 int max_colors = cinfo->desired_number_of_colors; 194 int total_colors, iroot, i, j; 195 boolean changed; 196 long temp; 197 static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE }; 198 199 /* We can allocate at least the nc'th root of max_colors per component. */ 200 /* Compute floor(nc'th root of max_colors). */ 201 iroot = 1; 202 do { 203 iroot++; 204 temp = iroot; /* set temp = iroot ** nc */ 205 for (i = 1; i < nc; i++) 206 temp *= iroot; 207 } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */ 208 iroot--; /* now iroot = floor(root) */ 209 210 /* Must have at least 2 color values per component */ 211 if (iroot < 2) 212 ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp); 213 214 /* Initialize to iroot color values for each component */ 215 total_colors = 1; 216 for (i = 0; i < nc; i++) { 217 Ncolors[i] = iroot; 218 total_colors *= iroot; 219 } 220 /* We may be able to increment the count for one or more components without 221 * exceeding max_colors, though we know not all can be incremented. 222 * Sometimes, the first component can be incremented more than once! 223 * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.) 224 * In RGB colorspace, try to increment G first, then R, then B. 225 */ 226 do { 227 changed = FALSE; 228 for (i = 0; i < nc; i++) { 229 j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i); 230 /* calculate new total_colors if Ncolors[j] is incremented */ 231 temp = total_colors / Ncolors[j]; 232 temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */ 233 if (temp > (long) max_colors) 234 break; /* won't fit, done with this pass */ 235 Ncolors[j]++; /* OK, apply the increment */ 236 total_colors = (int) temp; 237 changed = TRUE; 238 } 239 } while (changed); 240 241 return total_colors; 242 } 243 244 245 LOCAL(int) 246 output_value (j_decompress_ptr cinfo, int ci, int j, int maxj) 247 /* Return j'th output value, where j will range from 0 to maxj */ 248 /* The output values must fall in 0..MAXJSAMPLE in increasing order */ 249 { 250 /* We always provide values 0 and MAXJSAMPLE for each component; 251 * any additional values are equally spaced between these limits. 252 * (Forcing the upper and lower values to the limits ensures that 253 * dithering can't produce a color outside the selected gamut.) 254 */ 255 return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj); 256 } 257 258 259 LOCAL(int) 260 largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj) 261 /* Return largest input value that should map to j'th output value */ 262 /* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */ 263 { 264 /* Breakpoints are halfway between values returned by output_value */ 265 return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj)); 266 } 267 268 269 /* 270 * Create the colormap. 271 */ 272 273 LOCAL(void) 274 create_colormap (j_decompress_ptr cinfo) 275 { 276 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 277 JSAMPARRAY colormap; /* Created colormap */ 278 int total_colors; /* Number of distinct output colors */ 279 int i,j,k, nci, blksize, blkdist, ptr, val; 280 281 /* Select number of colors for each component */ 282 total_colors = select_ncolors(cinfo, cquantize->Ncolors); 283 284 /* Report selected color counts */ 285 if (cinfo->out_color_components == 3) 286 TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS, 287 total_colors, cquantize->Ncolors[0], 288 cquantize->Ncolors[1], cquantize->Ncolors[2]); 289 else 290 TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors); 291 292 /* Allocate and fill in the colormap. */ 293 /* The colors are ordered in the map in standard row-major order, */ 294 /* i.e. rightmost (highest-indexed) color changes most rapidly. */ 295 296 colormap = (*cinfo->mem->alloc_sarray) 297 ((j_common_ptr) cinfo, JPOOL_IMAGE, 298 (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components); 299 300 /* blksize is number of adjacent repeated entries for a component */ 301 /* blkdist is distance between groups of identical entries for a component */ 302 blkdist = total_colors; 303 304 for (i = 0; i < cinfo->out_color_components; i++) { 305 /* fill in colormap entries for i'th color component */ 306 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 307 blksize = blkdist / nci; 308 for (j = 0; j < nci; j++) { 309 /* Compute j'th output value (out of nci) for component */ 310 val = output_value(cinfo, i, j, nci-1); 311 /* Fill in all colormap entries that have this value of this component */ 312 for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) { 313 /* fill in blksize entries beginning at ptr */ 314 for (k = 0; k < blksize; k++) 315 colormap[i][ptr+k] = (JSAMPLE) val; 316 } 317 } 318 blkdist = blksize; /* blksize of this color is blkdist of next */ 319 } 320 321 /* Save the colormap in private storage, 322 * where it will survive color quantization mode changes. 323 */ 324 cquantize->sv_colormap = colormap; 325 cquantize->sv_actual = total_colors; 326 } 327 328 329 /* 330 * Create the color index table. 331 */ 332 333 LOCAL(void) 334 create_colorindex (j_decompress_ptr cinfo) 335 { 336 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 337 JSAMPROW indexptr; 338 int i,j,k, nci, blksize, val, pad; 339 340 /* For ordered dither, we pad the color index tables by MAXJSAMPLE in 341 * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE). 342 * This is not necessary in the other dithering modes. However, we 343 * flag whether it was done in case user changes dithering mode. 344 */ 345 if (cinfo->dither_mode == JDITHER_ORDERED) { 346 pad = MAXJSAMPLE*2; 347 cquantize->is_padded = TRUE; 348 } else { 349 pad = 0; 350 cquantize->is_padded = FALSE; 351 } 352 353 cquantize->colorindex = (*cinfo->mem->alloc_sarray) 354 ((j_common_ptr) cinfo, JPOOL_IMAGE, 355 (JDIMENSION) (MAXJSAMPLE+1 + pad), 356 (JDIMENSION) cinfo->out_color_components); 357 358 /* blksize is number of adjacent repeated entries for a component */ 359 blksize = cquantize->sv_actual; 360 361 for (i = 0; i < cinfo->out_color_components; i++) { 362 /* fill in colorindex entries for i'th color component */ 363 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 364 blksize = blksize / nci; 365 366 /* adjust colorindex pointers to provide padding at negative indexes. */ 367 if (pad) 368 cquantize->colorindex[i] += MAXJSAMPLE; 369 370 /* in loop, val = index of current output value, */ 371 /* and k = largest j that maps to current val */ 372 indexptr = cquantize->colorindex[i]; 373 val = 0; 374 k = largest_input_value(cinfo, i, 0, nci-1); 375 for (j = 0; j <= MAXJSAMPLE; j++) { 376 while (j > k) /* advance val if past boundary */ 377 k = largest_input_value(cinfo, i, ++val, nci-1); 378 /* premultiply so that no multiplication needed in main processing */ 379 indexptr[j] = (JSAMPLE) (val * blksize); 380 } 381 /* Pad at both ends if necessary */ 382 if (pad) 383 for (j = 1; j <= MAXJSAMPLE; j++) { 384 indexptr[-j] = indexptr[0]; 385 indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE]; 386 } 387 } 388 } 389 390 391 /* 392 * Create an ordered-dither array for a component having ncolors 393 * distinct output values. 394 */ 395 396 LOCAL(ODITHER_MATRIX_PTR) 397 make_odither_array (j_decompress_ptr cinfo, int ncolors) 398 { 399 ODITHER_MATRIX_PTR odither; 400 int j,k; 401 INT32 num,den; 402 403 odither = (ODITHER_MATRIX_PTR) 404 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 405 SIZEOF(ODITHER_MATRIX)); 406 /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1). 407 * Hence the dither value for the matrix cell with fill order f 408 * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1). 409 * On 16-bit-int machine, be careful to avoid overflow. 410 */ 411 den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1)); 412 for (j = 0; j < ODITHER_SIZE; j++) { 413 for (k = 0; k < ODITHER_SIZE; k++) { 414 num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k]))) 415 * MAXJSAMPLE; 416 /* Ensure round towards zero despite C's lack of consistency 417 * about rounding negative values in integer division... 418 */ 419 odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den); 420 } 421 } 422 return odither; 423 } 424 425 426 /* 427 * Create the ordered-dither tables. 428 * Components having the same number of representative colors may 429 * share a dither table. 430 */ 431 432 LOCAL(void) 433 create_odither_tables (j_decompress_ptr cinfo) 434 { 435 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 436 ODITHER_MATRIX_PTR odither; 437 int i, j, nci; 438 439 for (i = 0; i < cinfo->out_color_components; i++) { 440 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 441 odither = NULL; /* search for matching prior component */ 442 for (j = 0; j < i; j++) { 443 if (nci == cquantize->Ncolors[j]) { 444 odither = cquantize->odither[j]; 445 break; 446 } 447 } 448 if (odither == NULL) /* need a new table? */ 449 odither = make_odither_array(cinfo, nci); 450 cquantize->odither[i] = odither; 451 } 452 } 453 454 455 /* 456 * Map some rows of pixels to the output colormapped representation. 457 */ 458 459 METHODDEF(void) 460 color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 461 JSAMPARRAY output_buf, int num_rows) 462 /* General case, no dithering */ 463 { 464 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 465 JSAMPARRAY colorindex = cquantize->colorindex; 466 register int pixcode, ci; 467 register JSAMPROW ptrin, ptrout; 468 int row; 469 JDIMENSION col; 470 JDIMENSION width = cinfo->output_width; 471 register int nc = cinfo->out_color_components; 472 473 for (row = 0; row < num_rows; row++) { 474 ptrin = input_buf[row]; 475 ptrout = output_buf[row]; 476 for (col = width; col > 0; col--) { 477 pixcode = 0; 478 for (ci = 0; ci < nc; ci++) { 479 pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]); 480 } 481 *ptrout++ = (JSAMPLE) pixcode; 482 } 483 } 484 } 485 486 487 METHODDEF(void) 488 color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 489 JSAMPARRAY output_buf, int num_rows) 490 /* Fast path for out_color_components==3, no dithering */ 491 { 492 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 493 register int pixcode; 494 register JSAMPROW ptrin, ptrout; 495 JSAMPROW colorindex0 = cquantize->colorindex[0]; 496 JSAMPROW colorindex1 = cquantize->colorindex[1]; 497 JSAMPROW colorindex2 = cquantize->colorindex[2]; 498 int row; 499 JDIMENSION col; 500 JDIMENSION width = cinfo->output_width; 501 502 for (row = 0; row < num_rows; row++) { 503 ptrin = input_buf[row]; 504 ptrout = output_buf[row]; 505 for (col = width; col > 0; col--) { 506 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]); 507 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]); 508 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]); 509 *ptrout++ = (JSAMPLE) pixcode; 510 } 511 } 512 } 513 514 515 METHODDEF(void) 516 quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 517 JSAMPARRAY output_buf, int num_rows) 518 /* General case, with ordered dithering */ 519 { 520 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 521 register JSAMPROW input_ptr; 522 register JSAMPROW output_ptr; 523 JSAMPROW colorindex_ci; 524 int * dither; /* points to active row of dither matrix */ 525 int row_index, col_index; /* current indexes into dither matrix */ 526 int nc = cinfo->out_color_components; 527 int ci; 528 int row; 529 JDIMENSION col; 530 JDIMENSION width = cinfo->output_width; 531 532 for (row = 0; row < num_rows; row++) { 533 /* Initialize output values to 0 so can process components separately */ 534 FMEMZERO((void FAR *) output_buf[row], 535 (size_t) (width * SIZEOF(JSAMPLE))); 536 row_index = cquantize->row_index; 537 for (ci = 0; ci < nc; ci++) { 538 input_ptr = input_buf[row] + ci; 539 output_ptr = output_buf[row]; 540 colorindex_ci = cquantize->colorindex[ci]; 541 dither = cquantize->odither[ci][row_index]; 542 col_index = 0; 543 544 for (col = width; col > 0; col--) { 545 /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE, 546 * select output value, accumulate into output code for this pixel. 547 * Range-limiting need not be done explicitly, as we have extended 548 * the colorindex table to produce the right answers for out-of-range 549 * inputs. The maximum dither is +- MAXJSAMPLE; this sets the 550 * required amount of padding. 551 */ 552 *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]]; 553 input_ptr += nc; 554 output_ptr++; 555 col_index = (col_index + 1) & ODITHER_MASK; 556 } 557 } 558 /* Advance row index for next row */ 559 row_index = (row_index + 1) & ODITHER_MASK; 560 cquantize->row_index = row_index; 561 } 562 } 563 564 565 METHODDEF(void) 566 quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 567 JSAMPARRAY output_buf, int num_rows) 568 /* Fast path for out_color_components==3, with ordered dithering */ 569 { 570 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 571 register int pixcode; 572 register JSAMPROW input_ptr; 573 register JSAMPROW output_ptr; 574 JSAMPROW colorindex0 = cquantize->colorindex[0]; 575 JSAMPROW colorindex1 = cquantize->colorindex[1]; 576 JSAMPROW colorindex2 = cquantize->colorindex[2]; 577 int * dither0; /* points to active row of dither matrix */ 578 int * dither1; 579 int * dither2; 580 int row_index, col_index; /* current indexes into dither matrix */ 581 int row; 582 JDIMENSION col; 583 JDIMENSION width = cinfo->output_width; 584 585 for (row = 0; row < num_rows; row++) { 586 row_index = cquantize->row_index; 587 input_ptr = input_buf[row]; 588 output_ptr = output_buf[row]; 589 dither0 = cquantize->odither[0][row_index]; 590 dither1 = cquantize->odither[1][row_index]; 591 dither2 = cquantize->odither[2][row_index]; 592 col_index = 0; 593 594 for (col = width; col > 0; col--) { 595 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) + 596 dither0[col_index]]); 597 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) + 598 dither1[col_index]]); 599 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) + 600 dither2[col_index]]); 601 *output_ptr++ = (JSAMPLE) pixcode; 602 col_index = (col_index + 1) & ODITHER_MASK; 603 } 604 row_index = (row_index + 1) & ODITHER_MASK; 605 cquantize->row_index = row_index; 606 } 607 } 608 609 610 METHODDEF(void) 611 quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 612 JSAMPARRAY output_buf, int num_rows) 613 /* General case, with Floyd-Steinberg dithering */ 614 { 615 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 616 register LOCFSERROR cur; /* current error or pixel value */ 617 LOCFSERROR belowerr; /* error for pixel below cur */ 618 LOCFSERROR bpreverr; /* error for below/prev col */ 619 LOCFSERROR bnexterr; /* error for below/next col */ 620 LOCFSERROR delta; 621 register FSERRPTR errorptr; /* => fserrors[] at column before current */ 622 register JSAMPROW input_ptr; 623 register JSAMPROW output_ptr; 624 JSAMPROW colorindex_ci; 625 JSAMPROW colormap_ci; 626 int pixcode; 627 int nc = cinfo->out_color_components; 628 int dir; /* 1 for left-to-right, -1 for right-to-left */ 629 int dirnc; /* dir * nc */ 630 int ci; 631 int row; 632 JDIMENSION col; 633 JDIMENSION width = cinfo->output_width; 634 JSAMPLE *range_limit = cinfo->sample_range_limit; 635 SHIFT_TEMPS 636 637 for (row = 0; row < num_rows; row++) { 638 /* Initialize output values to 0 so can process components separately */ 639 FMEMZERO((void FAR *) output_buf[row], 640 (size_t) (width * SIZEOF(JSAMPLE))); 641 for (ci = 0; ci < nc; ci++) { 642 input_ptr = input_buf[row] + ci; 643 output_ptr = output_buf[row]; 644 if (cquantize->on_odd_row) { 645 /* work right to left in this row */ 646 input_ptr += (width-1) * nc; /* so point to rightmost pixel */ 647 output_ptr += width-1; 648 dir = -1; 649 dirnc = -nc; 650 errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */ 651 } else { 652 /* work left to right in this row */ 653 dir = 1; 654 dirnc = nc; 655 errorptr = cquantize->fserrors[ci]; /* => entry before first column */ 656 } 657 colorindex_ci = cquantize->colorindex[ci]; 658 colormap_ci = cquantize->sv_colormap[ci]; 659 /* Preset error values: no error propagated to first pixel from left */ 660 cur = 0; 661 /* and no error propagated to row below yet */ 662 belowerr = bpreverr = 0; 663 664 for (col = width; col > 0; col--) { 665 /* cur holds the error propagated from the previous pixel on the 666 * current line. Add the error propagated from the previous line 667 * to form the complete error correction term for this pixel, and 668 * round the error term (which is expressed * 16) to an integer. 669 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct 670 * for either sign of the error value. 671 * Note: errorptr points to *previous* column's array entry. 672 */ 673 cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4); 674 /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE. 675 * The maximum error is +- MAXJSAMPLE; this sets the required size 676 * of the range_limit array. 677 */ 678 cur += GETJSAMPLE(*input_ptr); 679 cur = GETJSAMPLE(range_limit[cur]); 680 /* Select output value, accumulate into output code for this pixel */ 681 pixcode = GETJSAMPLE(colorindex_ci[cur]); 682 *output_ptr += (JSAMPLE) pixcode; 683 /* Compute actual representation error at this pixel */ 684 /* Note: we can do this even though we don't have the final */ 685 /* pixel code, because the colormap is orthogonal. */ 686 cur -= GETJSAMPLE(colormap_ci[pixcode]); 687 /* Compute error fractions to be propagated to adjacent pixels. 688 * Add these into the running sums, and simultaneously shift the 689 * next-line error sums left by 1 column. 690 */ 691 bnexterr = cur; 692 delta = cur * 2; 693 cur += delta; /* form error * 3 */ 694 errorptr[0] = (FSERROR) (bpreverr + cur); 695 cur += delta; /* form error * 5 */ 696 bpreverr = belowerr + cur; 697 belowerr = bnexterr; 698 cur += delta; /* form error * 7 */ 699 /* At this point cur contains the 7/16 error value to be propagated 700 * to the next pixel on the current line, and all the errors for the 701 * next line have been shifted over. We are therefore ready to move on. 702 */ 703 input_ptr += dirnc; /* advance input ptr to next column */ 704 output_ptr += dir; /* advance output ptr to next column */ 705 errorptr += dir; /* advance errorptr to current column */ 706 } 707 /* Post-loop cleanup: we must unload the final error value into the 708 * final fserrors[] entry. Note we need not unload belowerr because 709 * it is for the dummy column before or after the actual array. 710 */ 711 errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */ 712 } 713 cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE); 714 } 715 } 716 717 718 /* 719 * Allocate workspace for Floyd-Steinberg errors. 720 */ 721 722 LOCAL(void) 723 alloc_fs_workspace (j_decompress_ptr cinfo) 724 { 725 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 726 size_t arraysize; 727 int i; 728 729 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); 730 for (i = 0; i < cinfo->out_color_components; i++) { 731 cquantize->fserrors[i] = (FSERRPTR) 732 (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize); 733 } 734 } 735 736 737 /* 738 * Initialize for one-pass color quantization. 739 */ 740 741 METHODDEF(void) 742 start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan) 743 { 744 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 745 size_t arraysize; 746 int i; 747 748 /* Install my colormap. */ 749 cinfo->colormap = cquantize->sv_colormap; 750 cinfo->actual_number_of_colors = cquantize->sv_actual; 751 752 /* Initialize for desired dithering mode. */ 753 switch (cinfo->dither_mode) { 754 case JDITHER_NONE: 755 if (cinfo->out_color_components == 3) 756 cquantize->pub.color_quantize = color_quantize3; 757 else 758 cquantize->pub.color_quantize = color_quantize; 759 break; 760 case JDITHER_ORDERED: 761 if (cinfo->out_color_components == 3) 762 cquantize->pub.color_quantize = quantize3_ord_dither; 763 else 764 cquantize->pub.color_quantize = quantize_ord_dither; 765 cquantize->row_index = 0; /* initialize state for ordered dither */ 766 /* If user changed to ordered dither from another mode, 767 * we must recreate the color index table with padding. 768 * This will cost extra space, but probably isn't very likely. 769 */ 770 if (! cquantize->is_padded) 771 create_colorindex(cinfo); 772 /* Create ordered-dither tables if we didn't already. */ 773 if (cquantize->odither[0] == NULL) 774 create_odither_tables(cinfo); 775 break; 776 case JDITHER_FS: 777 cquantize->pub.color_quantize = quantize_fs_dither; 778 cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */ 779 /* Allocate Floyd-Steinberg workspace if didn't already. */ 780 if (cquantize->fserrors[0] == NULL) 781 alloc_fs_workspace(cinfo); 782 /* Initialize the propagated errors to zero. */ 783 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); 784 for (i = 0; i < cinfo->out_color_components; i++) 785 FMEMZERO((void FAR *) cquantize->fserrors[i], arraysize); 786 break; 787 default: 788 ERREXIT(cinfo, JERR_NOT_COMPILED); 789 break; 790 } 791 } 792 793 794 /* 795 * Finish up at the end of the pass. 796 */ 797 798 METHODDEF(void) 799 finish_pass_1_quant (j_decompress_ptr cinfo) 800 { 801 /* no work in 1-pass case */ 802 } 803 804 805 /* 806 * Switch to a new external colormap between output passes. 807 * Shouldn't get to this module! 808 */ 809 810 METHODDEF(void) 811 new_color_map_1_quant (j_decompress_ptr cinfo) 812 { 813 ERREXIT(cinfo, JERR_MODE_CHANGE); 814 } 815 816 817 /* 818 * Module initialization routine for 1-pass color quantization. 819 */ 820 821 GLOBAL(void) 822 jinit_1pass_quantizer (j_decompress_ptr cinfo) 823 { 824 my_cquantize_ptr cquantize; 825 826 cquantize = (my_cquantize_ptr) 827 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 828 SIZEOF(my_cquantizer)); 829 cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize; 830 cquantize->pub.start_pass = start_pass_1_quant; 831 cquantize->pub.finish_pass = finish_pass_1_quant; 832 cquantize->pub.new_color_map = new_color_map_1_quant; 833 cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */ 834 cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */ 835 836 /* Make sure my internal arrays won't overflow */ 837 if (cinfo->out_color_components > MAX_Q_COMPS) 838 ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS); 839 /* Make sure colormap indexes can be represented by JSAMPLEs */ 840 if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1)) 841 ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1); 842 843 /* Create the colormap and color index table. */ 844 create_colormap(cinfo); 845 create_colorindex(cinfo); 846 847 /* Allocate Floyd-Steinberg workspace now if requested. 848 * We do this now since it is FAR storage and may affect the memory 849 * manager's space calculations. If the user changes to FS dither 850 * mode in a later pass, we will allocate the space then, and will 851 * possibly overrun the max_memory_to_use setting. 852 */ 853 if (cinfo->dither_mode == JDITHER_FS) 854 alloc_fs_workspace(cinfo); 855 } 856 857 #endif /* QUANT_1PASS_SUPPORTED */ 858
