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, 2015, D. R. Commander. 8 * For conditions of distribution and use, see the accompanying README.ijg 9 * file. 10 * 11 * This file contains 1-pass color quantization (color mapping) routines. 12 * These routines provide mapping to a fixed color map using equally spaced 13 * color values. Optional Floyd-Steinberg or ordered dithering is available. 14 */ 15 16 #define JPEG_INTERNALS 17 #include "jinclude.h" 18 #include "jpeglib.h" 19 20 #ifdef QUANT_1PASS_SUPPORTED 21 22 23 /* 24 * The main purpose of 1-pass quantization is to provide a fast, if not very 25 * high quality, colormapped output capability. A 2-pass quantizer usually 26 * gives better visual quality; however, for quantized grayscale output this 27 * quantizer is perfectly adequate. Dithering is highly recommended with this 28 * quantizer, though you can turn it off if you really want to. 29 * 30 * In 1-pass quantization the colormap must be chosen in advance of seeing the 31 * image. We use a map consisting of all combinations of Ncolors[i] color 32 * values for the i'th component. The Ncolors[] values are chosen so that 33 * their product, the total number of colors, is no more than that requested. 34 * (In most cases, the product will be somewhat less.) 35 * 36 * Since the colormap is orthogonal, the representative value for each color 37 * component can be determined without considering the other components; 38 * then these indexes can be combined into a colormap index by a standard 39 * N-dimensional-array-subscript calculation. Most of the arithmetic involved 40 * can be precalculated and stored in the lookup table colorindex[]. 41 * colorindex[i][j] maps pixel value j in component i to the nearest 42 * representative value (grid plane) for that component; this index is 43 * multiplied by the array stride for component i, so that the 44 * index of the colormap entry closest to a given pixel value is just 45 * sum( colorindex[component-number][pixel-component-value] ) 46 * Aside from being fast, this scheme allows for variable spacing between 47 * representative values with no additional lookup cost. 48 * 49 * If gamma correction has been applied in color conversion, it might be wise 50 * to adjust the color grid spacing so that the representative colors are 51 * equidistant in linear space. At this writing, gamma correction is not 52 * implemented by jdcolor, so nothing is done here. 53 */ 54 55 56 /* Declarations for ordered dithering. 57 * 58 * We use a standard 16x16 ordered dither array. The basic concept of ordered 59 * dithering is described in many references, for instance Dale Schumacher's 60 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991). 61 * In place of Schumacher's comparisons against a "threshold" value, we add a 62 * "dither" value to the input pixel and then round the result to the nearest 63 * output value. The dither value is equivalent to (0.5 - threshold) times 64 * the distance between output values. For ordered dithering, we assume that 65 * the output colors are equally spaced; if not, results will probably be 66 * worse, since the dither may be too much or too little at a given point. 67 * 68 * The normal calculation would be to form pixel value + dither, range-limit 69 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual. 70 * We can skip the separate range-limiting step by extending the colorindex 71 * table in both directions. 72 */ 73 74 #define ODITHER_SIZE 16 /* dimension of dither matrix */ 75 /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */ 76 #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */ 77 #define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */ 78 79 typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE]; 80 typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE]; 81 82 static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = { 83 /* Bayer's order-4 dither array. Generated by the code given in 84 * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I. 85 * The values in this array must range from 0 to ODITHER_CELLS-1. 86 */ 87 { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 }, 88 { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 }, 89 { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 }, 90 { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 }, 91 { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 }, 92 { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 }, 93 { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 }, 94 { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 }, 95 { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 }, 96 { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 }, 97 { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 }, 98 { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 }, 99 { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 }, 100 { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 }, 101 { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 }, 102 { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 } 103 }; 104 105 106 /* Declarations for Floyd-Steinberg dithering. 107 * 108 * Errors are accumulated into the array fserrors[], at a resolution of 109 * 1/16th of a pixel count. The error at a given pixel is propagated 110 * to its not-yet-processed neighbors using the standard F-S fractions, 111 * ... (here) 7/16 112 * 3/16 5/16 1/16 113 * We work left-to-right on even rows, right-to-left on odd rows. 114 * 115 * We can get away with a single array (holding one row's worth of errors) 116 * by using it to store the current row's errors at pixel columns not yet 117 * processed, but the next row's errors at columns already processed. We 118 * need only a few extra variables to hold the errors immediately around the 119 * current column. (If we are lucky, those variables are in registers, but 120 * even if not, they're probably cheaper to access than array elements are.) 121 * 122 * The fserrors[] array is indexed [component#][position]. 123 * We provide (#columns + 2) entries per component; the extra entry at each 124 * end saves us from special-casing the first and last pixels. 125 */ 126 127 #if BITS_IN_JSAMPLE == 8 128 typedef INT16 FSERROR; /* 16 bits should be enough */ 129 typedef int LOCFSERROR; /* use 'int' for calculation temps */ 130 #else 131 typedef JLONG FSERROR; /* may need more than 16 bits */ 132 typedef JLONG LOCFSERROR; /* be sure calculation temps are big enough */ 133 #endif 134 135 typedef FSERROR *FSERRPTR; /* pointer to error array */ 136 137 138 /* Private subobject */ 139 140 #define MAX_Q_COMPS 4 /* max components I can handle */ 141 142 typedef struct { 143 struct jpeg_color_quantizer pub; /* public fields */ 144 145 /* Initially allocated colormap is saved here */ 146 JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */ 147 int sv_actual; /* number of entries in use */ 148 149 JSAMPARRAY colorindex; /* Precomputed mapping for speed */ 150 /* colorindex[i][j] = index of color closest to pixel value j in component i, 151 * premultiplied as described above. Since colormap indexes must fit into 152 * JSAMPLEs, the entries of this array will too. 153 */ 154 boolean is_padded; /* is the colorindex padded for odither? */ 155 156 int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */ 157 158 /* Variables for ordered dithering */ 159 int row_index; /* cur row's vertical index in dither matrix */ 160 ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */ 161 162 /* Variables for Floyd-Steinberg dithering */ 163 FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */ 164 boolean on_odd_row; /* flag to remember which row we are on */ 165 } my_cquantizer; 166 167 typedef my_cquantizer *my_cquantize_ptr; 168 169 170 /* 171 * Policy-making subroutines for create_colormap and create_colorindex. 172 * These routines determine the colormap to be used. The rest of the module 173 * only assumes that the colormap is orthogonal. 174 * 175 * * select_ncolors decides how to divvy up the available colors 176 * among the components. 177 * * output_value defines the set of representative values for a component. 178 * * largest_input_value defines the mapping from input values to 179 * representative values for a component. 180 * Note that the latter two routines may impose different policies for 181 * different components, though this is not currently done. 182 */ 183 184 185 LOCAL(int) 186 select_ncolors (j_decompress_ptr cinfo, int Ncolors[]) 187 /* Determine allocation of desired colors to components, */ 188 /* and fill in Ncolors[] array to indicate choice. */ 189 /* Return value is total number of colors (product of Ncolors[] values). */ 190 { 191 int nc = cinfo->out_color_components; /* number of color components */ 192 int max_colors = cinfo->desired_number_of_colors; 193 int total_colors, iroot, i, j; 194 boolean changed; 195 long temp; 196 int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE }; 197 RGB_order[0] = rgb_green[cinfo->out_color_space]; 198 RGB_order[1] = rgb_red[cinfo->out_color_space]; 199 RGB_order[2] = rgb_blue[cinfo->out_color_space]; 200 201 /* We can allocate at least the nc'th root of max_colors per component. */ 202 /* Compute floor(nc'th root of max_colors). */ 203 iroot = 1; 204 do { 205 iroot++; 206 temp = iroot; /* set temp = iroot ** nc */ 207 for (i = 1; i < nc; i++) 208 temp *= iroot; 209 } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */ 210 iroot--; /* now iroot = floor(root) */ 211 212 /* Must have at least 2 color values per component */ 213 if (iroot < 2) 214 ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp); 215 216 /* Initialize to iroot color values for each component */ 217 total_colors = 1; 218 for (i = 0; i < nc; i++) { 219 Ncolors[i] = iroot; 220 total_colors *= iroot; 221 } 222 /* We may be able to increment the count for one or more components without 223 * exceeding max_colors, though we know not all can be incremented. 224 * Sometimes, the first component can be incremented more than once! 225 * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.) 226 * In RGB colorspace, try to increment G first, then R, then B. 227 */ 228 do { 229 changed = FALSE; 230 for (i = 0; i < nc; i++) { 231 j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i); 232 /* calculate new total_colors if Ncolors[j] is incremented */ 233 temp = total_colors / Ncolors[j]; 234 temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */ 235 if (temp > (long) max_colors) 236 break; /* won't fit, done with this pass */ 237 Ncolors[j]++; /* OK, apply the increment */ 238 total_colors = (int) temp; 239 changed = TRUE; 240 } 241 } while (changed); 242 243 return total_colors; 244 } 245 246 247 LOCAL(int) 248 output_value (j_decompress_ptr cinfo, int ci, int j, int maxj) 249 /* Return j'th output value, where j will range from 0 to maxj */ 250 /* The output values must fall in 0..MAXJSAMPLE in increasing order */ 251 { 252 /* We always provide values 0 and MAXJSAMPLE for each component; 253 * any additional values are equally spaced between these limits. 254 * (Forcing the upper and lower values to the limits ensures that 255 * dithering can't produce a color outside the selected gamut.) 256 */ 257 return (int) (((JLONG) j * MAXJSAMPLE + maxj/2) / maxj); 258 } 259 260 261 LOCAL(int) 262 largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj) 263 /* Return largest input value that should map to j'th output value */ 264 /* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */ 265 { 266 /* Breakpoints are halfway between values returned by output_value */ 267 return (int) (((JLONG) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj)); 268 } 269 270 271 /* 272 * Create the colormap. 273 */ 274 275 LOCAL(void) 276 create_colormap (j_decompress_ptr cinfo) 277 { 278 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 279 JSAMPARRAY colormap; /* Created colormap */ 280 int total_colors; /* Number of distinct output colors */ 281 int i,j,k, nci, blksize, blkdist, ptr, val; 282 283 /* Select number of colors for each component */ 284 total_colors = select_ncolors(cinfo, cquantize->Ncolors); 285 286 /* Report selected color counts */ 287 if (cinfo->out_color_components == 3) 288 TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS, 289 total_colors, cquantize->Ncolors[0], 290 cquantize->Ncolors[1], cquantize->Ncolors[2]); 291 else 292 TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors); 293 294 /* Allocate and fill in the colormap. */ 295 /* The colors are ordered in the map in standard row-major order, */ 296 /* i.e. rightmost (highest-indexed) color changes most rapidly. */ 297 298 colormap = (*cinfo->mem->alloc_sarray) 299 ((j_common_ptr) cinfo, JPOOL_IMAGE, 300 (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components); 301 302 /* blksize is number of adjacent repeated entries for a component */ 303 /* blkdist is distance between groups of identical entries for a component */ 304 blkdist = total_colors; 305 306 for (i = 0; i < cinfo->out_color_components; i++) { 307 /* fill in colormap entries for i'th color component */ 308 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 309 blksize = blkdist / nci; 310 for (j = 0; j < nci; j++) { 311 /* Compute j'th output value (out of nci) for component */ 312 val = output_value(cinfo, i, j, nci-1); 313 /* Fill in all colormap entries that have this value of this component */ 314 for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) { 315 /* fill in blksize entries beginning at ptr */ 316 for (k = 0; k < blksize; k++) 317 colormap[i][ptr+k] = (JSAMPLE) val; 318 } 319 } 320 blkdist = blksize; /* blksize of this color is blkdist of next */ 321 } 322 323 /* Save the colormap in private storage, 324 * where it will survive color quantization mode changes. 325 */ 326 cquantize->sv_colormap = colormap; 327 cquantize->sv_actual = total_colors; 328 } 329 330 331 /* 332 * Create the color index table. 333 */ 334 335 LOCAL(void) 336 create_colorindex (j_decompress_ptr cinfo) 337 { 338 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 339 JSAMPROW indexptr; 340 int i,j,k, nci, blksize, val, pad; 341 342 /* For ordered dither, we pad the color index tables by MAXJSAMPLE in 343 * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE). 344 * This is not necessary in the other dithering modes. However, we 345 * flag whether it was done in case user changes dithering mode. 346 */ 347 if (cinfo->dither_mode == JDITHER_ORDERED) { 348 pad = MAXJSAMPLE*2; 349 cquantize->is_padded = TRUE; 350 } else { 351 pad = 0; 352 cquantize->is_padded = FALSE; 353 } 354 355 cquantize->colorindex = (*cinfo->mem->alloc_sarray) 356 ((j_common_ptr) cinfo, JPOOL_IMAGE, 357 (JDIMENSION) (MAXJSAMPLE+1 + pad), 358 (JDIMENSION) cinfo->out_color_components); 359 360 /* blksize is number of adjacent repeated entries for a component */ 361 blksize = cquantize->sv_actual; 362 363 for (i = 0; i < cinfo->out_color_components; i++) { 364 /* fill in colorindex entries for i'th color component */ 365 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 366 blksize = blksize / nci; 367 368 /* adjust colorindex pointers to provide padding at negative indexes. */ 369 if (pad) 370 cquantize->colorindex[i] += MAXJSAMPLE; 371 372 /* in loop, val = index of current output value, */ 373 /* and k = largest j that maps to current val */ 374 indexptr = cquantize->colorindex[i]; 375 val = 0; 376 k = largest_input_value(cinfo, i, 0, nci-1); 377 for (j = 0; j <= MAXJSAMPLE; j++) { 378 while (j > k) /* advance val if past boundary */ 379 k = largest_input_value(cinfo, i, ++val, nci-1); 380 /* premultiply so that no multiplication needed in main processing */ 381 indexptr[j] = (JSAMPLE) (val * blksize); 382 } 383 /* Pad at both ends if necessary */ 384 if (pad) 385 for (j = 1; j <= MAXJSAMPLE; j++) { 386 indexptr[-j] = indexptr[0]; 387 indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE]; 388 } 389 } 390 } 391 392 393 /* 394 * Create an ordered-dither array for a component having ncolors 395 * distinct output values. 396 */ 397 398 LOCAL(ODITHER_MATRIX_PTR) 399 make_odither_array (j_decompress_ptr cinfo, int ncolors) 400 { 401 ODITHER_MATRIX_PTR odither; 402 int j,k; 403 JLONG num,den; 404 405 odither = (ODITHER_MATRIX_PTR) 406 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 407 sizeof(ODITHER_MATRIX)); 408 /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1). 409 * Hence the dither value for the matrix cell with fill order f 410 * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1). 411 * On 16-bit-int machine, be careful to avoid overflow. 412 */ 413 den = 2 * ODITHER_CELLS * ((JLONG) (ncolors - 1)); 414 for (j = 0; j < ODITHER_SIZE; j++) { 415 for (k = 0; k < ODITHER_SIZE; k++) { 416 num = ((JLONG) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k]))) 417 * MAXJSAMPLE; 418 /* Ensure round towards zero despite C's lack of consistency 419 * about rounding negative values in integer division... 420 */ 421 odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den); 422 } 423 } 424 return odither; 425 } 426 427 428 /* 429 * Create the ordered-dither tables. 430 * Components having the same number of representative colors may 431 * share a dither table. 432 */ 433 434 LOCAL(void) 435 create_odither_tables (j_decompress_ptr cinfo) 436 { 437 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 438 ODITHER_MATRIX_PTR odither; 439 int i, j, nci; 440 441 for (i = 0; i < cinfo->out_color_components; i++) { 442 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 443 odither = NULL; /* search for matching prior component */ 444 for (j = 0; j < i; j++) { 445 if (nci == cquantize->Ncolors[j]) { 446 odither = cquantize->odither[j]; 447 break; 448 } 449 } 450 if (odither == NULL) /* need a new table? */ 451 odither = make_odither_array(cinfo, nci); 452 cquantize->odither[i] = odither; 453 } 454 } 455 456 457 /* 458 * Map some rows of pixels to the output colormapped representation. 459 */ 460 461 METHODDEF(void) 462 color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 463 JSAMPARRAY output_buf, int num_rows) 464 /* General case, no dithering */ 465 { 466 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 467 JSAMPARRAY colorindex = cquantize->colorindex; 468 register int pixcode, ci; 469 register JSAMPROW ptrin, ptrout; 470 int row; 471 JDIMENSION col; 472 JDIMENSION width = cinfo->output_width; 473 register int nc = cinfo->out_color_components; 474 475 for (row = 0; row < num_rows; row++) { 476 ptrin = input_buf[row]; 477 ptrout = output_buf[row]; 478 for (col = width; col > 0; col--) { 479 pixcode = 0; 480 for (ci = 0; ci < nc; ci++) { 481 pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]); 482 } 483 *ptrout++ = (JSAMPLE) pixcode; 484 } 485 } 486 } 487 488 489 METHODDEF(void) 490 color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 491 JSAMPARRAY output_buf, int num_rows) 492 /* Fast path for out_color_components==3, no dithering */ 493 { 494 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 495 register int pixcode; 496 register JSAMPROW ptrin, ptrout; 497 JSAMPROW colorindex0 = cquantize->colorindex[0]; 498 JSAMPROW colorindex1 = cquantize->colorindex[1]; 499 JSAMPROW colorindex2 = cquantize->colorindex[2]; 500 int row; 501 JDIMENSION col; 502 JDIMENSION width = cinfo->output_width; 503 504 for (row = 0; row < num_rows; row++) { 505 ptrin = input_buf[row]; 506 ptrout = output_buf[row]; 507 for (col = width; col > 0; col--) { 508 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]); 509 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]); 510 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]); 511 *ptrout++ = (JSAMPLE) pixcode; 512 } 513 } 514 } 515 516 517 METHODDEF(void) 518 quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 519 JSAMPARRAY output_buf, int num_rows) 520 /* General case, with ordered dithering */ 521 { 522 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 523 register JSAMPROW input_ptr; 524 register JSAMPROW output_ptr; 525 JSAMPROW colorindex_ci; 526 int *dither; /* points to active row of dither matrix */ 527 int row_index, col_index; /* current indexes into dither matrix */ 528 int nc = cinfo->out_color_components; 529 int ci; 530 int row; 531 JDIMENSION col; 532 JDIMENSION width = cinfo->output_width; 533 534 for (row = 0; row < num_rows; row++) { 535 /* Initialize output values to 0 so can process components separately */ 536 jzero_far((void *) output_buf[row], (size_t) (width * sizeof(JSAMPLE))); 537 row_index = cquantize->row_index; 538 for (ci = 0; ci < nc; ci++) { 539 input_ptr = input_buf[row] + ci; 540 output_ptr = output_buf[row]; 541 colorindex_ci = cquantize->colorindex[ci]; 542 dither = cquantize->odither[ci][row_index]; 543 col_index = 0; 544 545 for (col = width; col > 0; col--) { 546 /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE, 547 * select output value, accumulate into output code for this pixel. 548 * Range-limiting need not be done explicitly, as we have extended 549 * the colorindex table to produce the right answers for out-of-range 550 * inputs. The maximum dither is +- MAXJSAMPLE; this sets the 551 * required amount of padding. 552 */ 553 *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]]; 554 input_ptr += nc; 555 output_ptr++; 556 col_index = (col_index + 1) & ODITHER_MASK; 557 } 558 } 559 /* Advance row index for next row */ 560 row_index = (row_index + 1) & ODITHER_MASK; 561 cquantize->row_index = row_index; 562 } 563 } 564 565 566 METHODDEF(void) 567 quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 568 JSAMPARRAY output_buf, int num_rows) 569 /* Fast path for out_color_components==3, with ordered dithering */ 570 { 571 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 572 register int pixcode; 573 register JSAMPROW input_ptr; 574 register JSAMPROW output_ptr; 575 JSAMPROW colorindex0 = cquantize->colorindex[0]; 576 JSAMPROW colorindex1 = cquantize->colorindex[1]; 577 JSAMPROW colorindex2 = cquantize->colorindex[2]; 578 int *dither0; /* points to active row of dither matrix */ 579 int *dither1; 580 int *dither2; 581 int row_index, col_index; /* current indexes into dither matrix */ 582 int row; 583 JDIMENSION col; 584 JDIMENSION width = cinfo->output_width; 585 586 for (row = 0; row < num_rows; row++) { 587 row_index = cquantize->row_index; 588 input_ptr = input_buf[row]; 589 output_ptr = output_buf[row]; 590 dither0 = cquantize->odither[0][row_index]; 591 dither1 = cquantize->odither[1][row_index]; 592 dither2 = cquantize->odither[2][row_index]; 593 col_index = 0; 594 595 for (col = width; col > 0; col--) { 596 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) + 597 dither0[col_index]]); 598 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) + 599 dither1[col_index]]); 600 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) + 601 dither2[col_index]]); 602 *output_ptr++ = (JSAMPLE) pixcode; 603 col_index = (col_index + 1) & ODITHER_MASK; 604 } 605 row_index = (row_index + 1) & ODITHER_MASK; 606 cquantize->row_index = row_index; 607 } 608 } 609 610 611 METHODDEF(void) 612 quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 613 JSAMPARRAY output_buf, int num_rows) 614 /* General case, with Floyd-Steinberg dithering */ 615 { 616 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 617 register LOCFSERROR cur; /* current error or pixel value */ 618 LOCFSERROR belowerr; /* error for pixel below cur */ 619 LOCFSERROR bpreverr; /* error for below/prev col */ 620 LOCFSERROR bnexterr; /* error for below/next col */ 621 LOCFSERROR delta; 622 register FSERRPTR errorptr; /* => fserrors[] at column before current */ 623 register JSAMPROW input_ptr; 624 register JSAMPROW output_ptr; 625 JSAMPROW colorindex_ci; 626 JSAMPROW colormap_ci; 627 int pixcode; 628 int nc = cinfo->out_color_components; 629 int dir; /* 1 for left-to-right, -1 for right-to-left */ 630 int dirnc; /* dir * nc */ 631 int ci; 632 int row; 633 JDIMENSION col; 634 JDIMENSION width = cinfo->output_width; 635 JSAMPLE *range_limit = cinfo->sample_range_limit; 636 SHIFT_TEMPS 637 638 for (row = 0; row < num_rows; row++) { 639 /* Initialize output values to 0 so can process components separately */ 640 jzero_far((void *) output_buf[row], (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 jzero_far((void *) 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 may affect the memory manager's space 849 * calculations. If the user changes to FS dither mode in a later pass, we 850 * will allocate the space then, and will possibly overrun the 851 * 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
