1 /* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5 /* 6 * jquant1.c 7 * 8 * Copyright (C) 1991-1996, Thomas G. Lane. 9 * This file is part of the Independent JPEG Group's software. 10 * For conditions of distribution and use, see the accompanying README file. 11 * 12 * This file contains 1-pass color quantization (color mapping) routines. 13 * These routines provide mapping to a fixed color map using equally spaced 14 * color values. Optional Floyd-Steinberg or ordered dithering is available. 15 */ 16 17 #define JPEG_INTERNALS 18 #include "jinclude.h" 19 #include "jpeglib.h" 20 21 #ifdef QUANT_1PASS_SUPPORTED 22 23 24 /* 25 * The main purpose of 1-pass quantization is to provide a fast, if not very 26 * high quality, colormapped output capability. A 2-pass quantizer usually 27 * gives better visual quality; however, for quantized grayscale output this 28 * quantizer is perfectly adequate. Dithering is highly recommended with this 29 * quantizer, though you can turn it off if you really want to. 30 * 31 * In 1-pass quantization the colormap must be chosen in advance of seeing the 32 * image. We use a map consisting of all combinations of Ncolors[i] color 33 * values for the i'th component. The Ncolors[] values are chosen so that 34 * their product, the total number of colors, is no more than that requested. 35 * (In most cases, the product will be somewhat less.) 36 * 37 * Since the colormap is orthogonal, the representative value for each color 38 * component can be determined without considering the other components; 39 * then these indexes can be combined into a colormap index by a standard 40 * N-dimensional-array-subscript calculation. Most of the arithmetic involved 41 * can be precalculated and stored in the lookup table colorindex[]. 42 * colorindex[i][j] maps pixel value j in component i to the nearest 43 * representative value (grid plane) for that component; this index is 44 * multiplied by the array stride for component i, so that the 45 * index of the colormap entry closest to a given pixel value is just 46 * sum( colorindex[component-number][pixel-component-value] ) 47 * Aside from being fast, this scheme allows for variable spacing between 48 * representative values with no additional lookup cost. 49 * 50 * If gamma correction has been applied in color conversion, it might be wise 51 * to adjust the color grid spacing so that the representative colors are 52 * equidistant in linear space. At this writing, gamma correction is not 53 * implemented by jdcolor, so nothing is done here. 54 */ 55 56 57 /* Declarations for ordered dithering. 58 * 59 * We use a standard 16x16 ordered dither array. The basic concept of ordered 60 * dithering is described in many references, for instance Dale Schumacher's 61 * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991). 62 * In place of Schumacher's comparisons against a "threshold" value, we add a 63 * "dither" value to the input pixel and then round the result to the nearest 64 * output value. The dither value is equivalent to (0.5 - threshold) times 65 * the distance between output values. For ordered dithering, we assume that 66 * the output colors are equally spaced; if not, results will probably be 67 * worse, since the dither may be too much or too little at a given point. 68 * 69 * The normal calculation would be to form pixel value + dither, range-limit 70 * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual. 71 * We can skip the separate range-limiting step by extending the colorindex 72 * table in both directions. 73 */ 74 75 #define ODITHER_SIZE 16 /* dimension of dither matrix */ 76 /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */ 77 #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */ 78 #define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around 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 * Note: on a wide image, we might not have enough room in a PC's near data 128 * segment to hold the error array; so it is allocated with alloc_large. 129 */ 130 131 #if BITS_IN_JSAMPLE == 8 132 typedef INT16 FSERROR; /* 16 bits should be enough */ 133 typedef int LOCFSERROR; /* use 'int' for calculation temps */ 134 #else 135 typedef INT32 FSERROR; /* may need more than 16 bits */ 136 typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */ 137 #endif 138 139 typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */ 140 141 142 /* Private subobject */ 143 144 #define MAX_Q_COMPS 4 /* max components I can handle */ 145 146 typedef struct { 147 struct jpeg_color_quantizer pub; /* public fields */ 148 149 /* Initially allocated colormap is saved here */ 150 JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */ 151 int sv_actual; /* number of entries in use */ 152 153 JSAMPARRAY colorindex; /* Precomputed mapping for speed */ 154 /* colorindex[i][j] = index of color closest to pixel value j in component i, 155 * premultiplied as described above. Since colormap indexes must fit into 156 * JSAMPLEs, the entries of this array will too. 157 */ 158 boolean is_padded; /* is the colorindex padded for odither? */ 159 160 int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */ 161 162 /* Variables for ordered dithering */ 163 int row_index; /* cur row's vertical index in dither matrix */ 164 ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */ 165 166 /* Variables for Floyd-Steinberg dithering */ 167 FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */ 168 boolean on_odd_row; /* flag to remember which row we are on */ 169 } my_cquantizer; 170 171 typedef my_cquantizer * my_cquantize_ptr; 172 173 174 /* 175 * Policy-making subroutines for create_colormap and create_colorindex. 176 * These routines determine the colormap to be used. The rest of the module 177 * only assumes that the colormap is orthogonal. 178 * 179 * * select_ncolors decides how to divvy up the available colors 180 * among the components. 181 * * output_value defines the set of representative values for a component. 182 * * largest_input_value defines the mapping from input values to 183 * representative values for a component. 184 * Note that the latter two routines may impose different policies for 185 * different components, though this is not currently done. 186 */ 187 188 189 LOCAL(int) 190 select_ncolors (j_decompress_ptr cinfo, int Ncolors[]) 191 /* Determine allocation of desired colors to components, */ 192 /* and fill in Ncolors[] array to indicate choice. */ 193 /* Return value is total number of colors (product of Ncolors[] values). */ 194 { 195 int nc = cinfo->out_color_components; /* number of color components */ 196 int max_colors = cinfo->desired_number_of_colors; 197 int total_colors, iroot, i, j; 198 boolean changed; 199 long temp; 200 static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE }; 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) (((INT32) 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) (((INT32) (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, 290 total_colors, cquantize->Ncolors[0], 291 cquantize->Ncolors[1], 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 INT32 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 * ((INT32) (ncolors - 1)); 415 for (j = 0; j < ODITHER_SIZE; j++) { 416 for (k = 0; k < ODITHER_SIZE; k++) { 417 num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k]))) 418 * 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 #ifdef __GNUC__ 443 #pragma GCC diagnostic push 444 #pragma GCC diagnostic ignored "-Warray-bounds" 445 #endif 446 for (i = 0; i < cinfo->out_color_components; i++) { 447 nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ 448 odither = NULL; /* search for matching prior component */ 449 for (j = 0; j < i; j++) { 450 if (nci == cquantize->Ncolors[j]) { 451 odither = cquantize->odither[j]; 452 break; 453 } 454 } 455 if (odither == NULL) /* need a new table? */ 456 odither = make_odither_array(cinfo, nci); 457 cquantize->odither[i] = odither; 458 } 459 #ifdef __GNUC__ 460 #pragma GCC diagnostic pop 461 #endif 462 } 463 464 465 /* 466 * Map some rows of pixels to the output colormapped representation. 467 */ 468 469 METHODDEF(void) 470 color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 471 JSAMPARRAY output_buf, int num_rows) 472 /* General case, no dithering */ 473 { 474 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 475 JSAMPARRAY colorindex = cquantize->colorindex; 476 register int pixcode, ci; 477 register JSAMPROW ptrin, ptrout; 478 int row; 479 JDIMENSION col; 480 JDIMENSION width = cinfo->output_width; 481 register int nc = cinfo->out_color_components; 482 483 for (row = 0; row < num_rows; row++) { 484 ptrin = input_buf[row]; 485 ptrout = output_buf[row]; 486 for (col = width; col > 0; col--) { 487 pixcode = 0; 488 for (ci = 0; ci < nc; ci++) { 489 pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]); 490 } 491 *ptrout++ = (JSAMPLE) pixcode; 492 } 493 } 494 } 495 496 497 METHODDEF(void) 498 color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 499 JSAMPARRAY output_buf, int num_rows) 500 /* Fast path for out_color_components==3, no dithering */ 501 { 502 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 503 register int pixcode; 504 register JSAMPROW ptrin, ptrout; 505 JSAMPROW colorindex0 = cquantize->colorindex[0]; 506 JSAMPROW colorindex1 = cquantize->colorindex[1]; 507 JSAMPROW colorindex2 = cquantize->colorindex[2]; 508 int row; 509 JDIMENSION col; 510 JDIMENSION width = cinfo->output_width; 511 512 for (row = 0; row < num_rows; row++) { 513 ptrin = input_buf[row]; 514 ptrout = output_buf[row]; 515 for (col = width; col > 0; col--) { 516 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]); 517 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]); 518 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]); 519 *ptrout++ = (JSAMPLE) pixcode; 520 } 521 } 522 } 523 524 525 METHODDEF(void) 526 quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 527 JSAMPARRAY output_buf, int num_rows) 528 /* General case, with ordered dithering */ 529 { 530 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 531 register JSAMPROW input_ptr; 532 register JSAMPROW output_ptr; 533 JSAMPROW colorindex_ci; 534 int * dither; /* points to active row of dither matrix */ 535 int row_index, col_index; /* current indexes into dither matrix */ 536 int nc = cinfo->out_color_components; 537 int ci; 538 int row; 539 JDIMENSION col; 540 JDIMENSION width = cinfo->output_width; 541 542 for (row = 0; row < num_rows; row++) { 543 /* Initialize output values to 0 so can process components separately */ 544 jzero_far((void FAR *) output_buf[row], 545 (size_t) (width * SIZEOF(JSAMPLE))); 546 row_index = cquantize->row_index; 547 for (ci = 0; ci < nc; ci++) { 548 input_ptr = input_buf[row] + ci; 549 output_ptr = output_buf[row]; 550 colorindex_ci = cquantize->colorindex[ci]; 551 dither = cquantize->odither[ci][row_index]; 552 col_index = 0; 553 554 for (col = width; col > 0; col--) { 555 /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE, 556 * select output value, accumulate into output code for this pixel. 557 * Range-limiting need not be done explicitly, as we have extended 558 * the colorindex table to produce the right answers for out-of-range 559 * inputs. The maximum dither is +- MAXJSAMPLE; this sets the 560 * required amount of padding. 561 */ 562 *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]]; 563 input_ptr += nc; 564 output_ptr++; 565 col_index = (col_index + 1) & ODITHER_MASK; 566 } 567 } 568 /* Advance row index for next row */ 569 row_index = (row_index + 1) & ODITHER_MASK; 570 cquantize->row_index = row_index; 571 } 572 } 573 574 575 METHODDEF(void) 576 quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 577 JSAMPARRAY output_buf, int num_rows) 578 /* Fast path for out_color_components==3, with ordered dithering */ 579 { 580 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 581 register int pixcode; 582 register JSAMPROW input_ptr; 583 register JSAMPROW output_ptr; 584 JSAMPROW colorindex0 = cquantize->colorindex[0]; 585 JSAMPROW colorindex1 = cquantize->colorindex[1]; 586 JSAMPROW colorindex2 = cquantize->colorindex[2]; 587 int * dither0; /* points to active row of dither matrix */ 588 int * dither1; 589 int * dither2; 590 int row_index, col_index; /* current indexes into dither matrix */ 591 int row; 592 JDIMENSION col; 593 JDIMENSION width = cinfo->output_width; 594 595 for (row = 0; row < num_rows; row++) { 596 row_index = cquantize->row_index; 597 input_ptr = input_buf[row]; 598 output_ptr = output_buf[row]; 599 dither0 = cquantize->odither[0][row_index]; 600 dither1 = cquantize->odither[1][row_index]; 601 dither2 = cquantize->odither[2][row_index]; 602 col_index = 0; 603 604 for (col = width; col > 0; col--) { 605 pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) + 606 dither0[col_index]]); 607 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) + 608 dither1[col_index]]); 609 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) + 610 dither2[col_index]]); 611 *output_ptr++ = (JSAMPLE) pixcode; 612 col_index = (col_index + 1) & ODITHER_MASK; 613 } 614 row_index = (row_index + 1) & ODITHER_MASK; 615 cquantize->row_index = row_index; 616 } 617 } 618 619 620 METHODDEF(void) 621 quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, 622 JSAMPARRAY output_buf, int num_rows) 623 /* General case, with Floyd-Steinberg dithering */ 624 { 625 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 626 register LOCFSERROR cur; /* current error or pixel value */ 627 LOCFSERROR belowerr; /* error for pixel below cur */ 628 LOCFSERROR bpreverr; /* error for below/prev col */ 629 LOCFSERROR bnexterr; /* error for below/next col */ 630 LOCFSERROR delta; 631 register FSERRPTR errorptr; /* => fserrors[] at column before current */ 632 register JSAMPROW input_ptr; 633 register JSAMPROW output_ptr; 634 JSAMPROW colorindex_ci; 635 JSAMPROW colormap_ci; 636 int pixcode; 637 int nc = cinfo->out_color_components; 638 int dir; /* 1 for left-to-right, -1 for right-to-left */ 639 int dirnc; /* dir * nc */ 640 int ci; 641 int row; 642 JDIMENSION col; 643 JDIMENSION width = cinfo->output_width; 644 JSAMPLE *range_limit = cinfo->sample_range_limit; 645 SHIFT_TEMPS 646 647 for (row = 0; row < num_rows; row++) { 648 /* Initialize output values to 0 so can process components separately */ 649 jzero_far((void FAR *) output_buf[row], 650 (size_t) (width * SIZEOF(JSAMPLE))); 651 for (ci = 0; ci < nc; ci++) { 652 input_ptr = input_buf[row] + ci; 653 output_ptr = output_buf[row]; 654 if (cquantize->on_odd_row) { 655 /* work right to left in this row */ 656 input_ptr += (width-1) * nc; /* so point to rightmost pixel */ 657 output_ptr += width-1; 658 dir = -1; 659 dirnc = -nc; 660 errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */ 661 } else { 662 /* work left to right in this row */ 663 dir = 1; 664 dirnc = nc; 665 errorptr = cquantize->fserrors[ci]; /* => entry before first column */ 666 } 667 colorindex_ci = cquantize->colorindex[ci]; 668 colormap_ci = cquantize->sv_colormap[ci]; 669 /* Preset error values: no error propagated to first pixel from left */ 670 cur = 0; 671 /* and no error propagated to row below yet */ 672 belowerr = bpreverr = 0; 673 674 for (col = width; col > 0; col--) { 675 /* cur holds the error propagated from the previous pixel on the 676 * current line. Add the error propagated from the previous line 677 * to form the complete error correction term for this pixel, and 678 * round the error term (which is expressed * 16) to an integer. 679 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct 680 * for either sign of the error value. 681 * Note: errorptr points to *previous* column's array entry. 682 */ 683 cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4); 684 /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE. 685 * The maximum error is +- MAXJSAMPLE; this sets the required size 686 * of the range_limit array. 687 */ 688 cur += GETJSAMPLE(*input_ptr); 689 cur = GETJSAMPLE(range_limit[cur]); 690 /* Select output value, accumulate into output code for this pixel */ 691 pixcode = GETJSAMPLE(colorindex_ci[cur]); 692 *output_ptr += (JSAMPLE) pixcode; 693 /* Compute actual representation error at this pixel */ 694 /* Note: we can do this even though we don't have the final */ 695 /* pixel code, because the colormap is orthogonal. */ 696 cur -= GETJSAMPLE(colormap_ci[pixcode]); 697 /* Compute error fractions to be propagated to adjacent pixels. 698 * Add these into the running sums, and simultaneously shift the 699 * next-line error sums left by 1 column. 700 */ 701 bnexterr = cur; 702 delta = cur * 2; 703 cur += delta; /* form error * 3 */ 704 errorptr[0] = (FSERROR) (bpreverr + cur); 705 cur += delta; /* form error * 5 */ 706 bpreverr = belowerr + cur; 707 belowerr = bnexterr; 708 cur += delta; /* form error * 7 */ 709 /* At this point cur contains the 7/16 error value to be propagated 710 * to the next pixel on the current line, and all the errors for the 711 * next line have been shifted over. We are therefore ready to move on. 712 */ 713 input_ptr += dirnc; /* advance input ptr to next column */ 714 output_ptr += dir; /* advance output ptr to next column */ 715 errorptr += dir; /* advance errorptr to current column */ 716 } 717 /* Post-loop cleanup: we must unload the final error value into the 718 * final fserrors[] entry. Note we need not unload belowerr because 719 * it is for the dummy column before or after the actual array. 720 */ 721 errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */ 722 } 723 cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE); 724 } 725 } 726 727 728 /* 729 * Allocate workspace for Floyd-Steinberg errors. 730 */ 731 732 LOCAL(void) 733 alloc_fs_workspace (j_decompress_ptr cinfo) 734 { 735 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 736 size_t arraysize; 737 int i; 738 739 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); 740 for (i = 0; i < cinfo->out_color_components; i++) { 741 cquantize->fserrors[i] = (FSERRPTR) 742 (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize); 743 } 744 } 745 746 747 /* 748 * Initialize for one-pass color quantization. 749 */ 750 751 METHODDEF(void) 752 start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan) 753 { 754 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; 755 size_t arraysize; 756 int i; 757 758 /* Install my colormap. */ 759 cinfo->colormap = cquantize->sv_colormap; 760 cinfo->actual_number_of_colors = cquantize->sv_actual; 761 762 /* Initialize for desired dithering mode. */ 763 switch (cinfo->dither_mode) { 764 case JDITHER_NONE: 765 if (cinfo->out_color_components == 3) 766 cquantize->pub.color_quantize = color_quantize3; 767 else 768 cquantize->pub.color_quantize = color_quantize; 769 break; 770 case JDITHER_ORDERED: 771 if (cinfo->out_color_components == 3) 772 cquantize->pub.color_quantize = quantize3_ord_dither; 773 else 774 cquantize->pub.color_quantize = quantize_ord_dither; 775 cquantize->row_index = 0; /* initialize state for ordered dither */ 776 /* If user changed to ordered dither from another mode, 777 * we must recreate the color index table with padding. 778 * This will cost extra space, but probably isn't very likely. 779 */ 780 if (! cquantize->is_padded) 781 create_colorindex(cinfo); 782 /* Create ordered-dither tables if we didn't already. */ 783 if (cquantize->odither[0] == NULL) 784 create_odither_tables(cinfo); 785 break; 786 case JDITHER_FS: 787 cquantize->pub.color_quantize = quantize_fs_dither; 788 cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */ 789 /* Allocate Floyd-Steinberg workspace if didn't already. */ 790 if (cquantize->fserrors[0] == NULL) 791 alloc_fs_workspace(cinfo); 792 /* Initialize the propagated errors to zero. */ 793 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); 794 for (i = 0; i < cinfo->out_color_components; i++) 795 jzero_far((void FAR *) cquantize->fserrors[i], arraysize); 796 break; 797 default: 798 ERREXIT(cinfo, JERR_NOT_COMPILED); 799 break; 800 } 801 } 802 803 804 /* 805 * Finish up at the end of the pass. 806 */ 807 808 METHODDEF(void) 809 finish_pass_1_quant (j_decompress_ptr cinfo) 810 { 811 /* no work in 1-pass case */ 812 } 813 814 815 /* 816 * Switch to a new external colormap between output passes. 817 * Shouldn't get to this module! 818 */ 819 820 METHODDEF(void) 821 new_color_map_1_quant (j_decompress_ptr cinfo) 822 { 823 ERREXIT(cinfo, JERR_MODE_CHANGE); 824 } 825 826 827 /* 828 * Module initialization routine for 1-pass color quantization. 829 */ 830 831 GLOBAL(void) 832 jinit_1pass_quantizer (j_decompress_ptr cinfo) 833 { 834 my_cquantize_ptr cquantize; 835 836 cquantize = (my_cquantize_ptr) 837 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 838 SIZEOF(my_cquantizer)); 839 cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize; 840 cquantize->pub.start_pass = start_pass_1_quant; 841 cquantize->pub.finish_pass = finish_pass_1_quant; 842 cquantize->pub.new_color_map = new_color_map_1_quant; 843 cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */ 844 cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */ 845 846 /* Make sure my internal arrays won't overflow */ 847 if (cinfo->out_color_components > MAX_Q_COMPS) 848 ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS); 849 /* Make sure colormap indexes can be represented by JSAMPLEs */ 850 if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1)) 851 ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1); 852 853 /* Create the colormap and color index table. */ 854 create_colormap(cinfo); 855 create_colorindex(cinfo); 856 857 /* Allocate Floyd-Steinberg workspace now if requested. 858 * We do this now since it is FAR storage and may affect the memory 859 * manager's space calculations. If the user changes to FS dither 860 * mode in a later pass, we will allocate the space then, and will 861 * possibly overrun the max_memory_to_use setting. 862 */ 863 if (cinfo->dither_mode == JDITHER_FS) 864 alloc_fs_workspace(cinfo); 865 } 866 867 #endif /* QUANT_1PASS_SUPPORTED */