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