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
80typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
81typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
82
83static 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
132typedef INT16 FSERROR; /* 16 bits should be enough */
133typedef int LOCFSERROR; /* use 'int' for calculation temps */
134#else
135typedef INT32 FSERROR; /* may need more than 16 bits */
136typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */
137#endif
138
139typedef 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
146typedef 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
171typedef 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
189LOCAL(int)
190select_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
248LOCAL(int)
249output_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
262LOCAL(int)
263largest_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
276LOCAL(void)
277create_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
336LOCAL(void)
337create_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
399LOCAL(ODITHER_MATRIX_PTR)
400make_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
435LOCAL(void)
436create_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
462METHODDEF(void)
463color_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
490METHODDEF(void)
491color_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
518METHODDEF(void)
519quantize_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 FAR *) output_buf[row],
538 (size_t) (width * SIZEOF(JSAMPLE)));
539 row_index = cquantize->row_index;
540 for (ci = 0; ci < nc; ci++) {
541 input_ptr = input_buf[row] + ci;
542 output_ptr = output_buf[row];
543 colorindex_ci = cquantize->colorindex[ci];
544 dither = cquantize->odither[ci][row_index];
545 col_index = 0;
546
547 for (col = width; col > 0; col--) {
548 /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
549 * select output value, accumulate into output code for this pixel.
550 * Range-limiting need not be done explicitly, as we have extended
551 * the colorindex table to produce the right answers for out-of-range
552 * inputs. The maximum dither is +- MAXJSAMPLE; this sets the
553 * required amount of padding.
554 */
555 *output_ptr += 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
568METHODDEF(void)
569quantize3_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 = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
599 dither0[col_index]]);
600 pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
601 dither1[col_index]]);
602 pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
603 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
613METHODDEF(void)
614quantize_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 FAR *) output_buf[row],
643 (size_t) (width * SIZEOF(JSAMPLE)));
644 for (ci = 0; ci < nc; ci++) {
645 input_ptr = input_buf[row] + ci;
646 output_ptr = output_buf[row];
647 if (cquantize->on_odd_row) {
648 /* work right to left in this row */
649 input_ptr += (width-1) * nc; /* so point to rightmost pixel */
650 output_ptr += width-1;
651 dir = -1;
652 dirnc = -nc;
653 errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */
654 } else {
655 /* work left to right in this row */
656 dir = 1;
657 dirnc = nc;
658 errorptr = cquantize->fserrors[ci]; /* => entry before first column */
659 }
660 colorindex_ci = cquantize->colorindex[ci];
661 colormap_ci = cquantize->sv_colormap[ci];
662 /* Preset error values: no error propagated to first pixel from left */
663 cur = 0;
664 /* and no error propagated to row below yet */
665 belowerr = bpreverr = 0;
666
667 for (col = width; col > 0; col--) {
668 /* cur holds the error propagated from the previous pixel on the
669 * current line. Add the error propagated from the previous line
670 * to form the complete error correction term for this pixel, and
671 * round the error term (which is expressed * 16) to an integer.
672 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
673 * for either sign of the error value.
674 * Note: errorptr points to *previous* column's array entry.
675 */
676 cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
677 /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
678 * The maximum error is +- MAXJSAMPLE; this sets the required size
679 * of the range_limit array.
680 */
681 cur += GETJSAMPLE(*input_ptr);
682 cur = GETJSAMPLE(range_limit[cur]);
683 /* Select output value, accumulate into output code for this pixel */
684 pixcode = GETJSAMPLE(colorindex_ci[cur]);
685 *output_ptr += (JSAMPLE) pixcode;
686 /* Compute actual representation error at this pixel */
687 /* Note: we can do this even though we don't have the final */
688 /* pixel code, because the colormap is orthogonal. */
689 cur -= GETJSAMPLE(colormap_ci[pixcode]);
690 /* Compute error fractions to be propagated to adjacent pixels.
691 * Add these into the running sums, and simultaneously shift the
692 * next-line error sums left by 1 column.
693 */
694 bnexterr = cur;
695 delta = cur * 2;
696 cur += delta; /* form error * 3 */
697 errorptr[0] = (FSERROR) (bpreverr + cur);
698 cur += delta; /* form error * 5 */
699 bpreverr = belowerr + cur;
700 belowerr = bnexterr;
701 cur += delta; /* form error * 7 */
702 /* At this point cur contains the 7/16 error value to be propagated
703 * to the next pixel on the current line, and all the errors for the
704 * next line have been shifted over. We are therefore ready to move on.
705 */
706 input_ptr += dirnc; /* advance input ptr to next column */
707 output_ptr += dir; /* advance output ptr to next column */
708 errorptr += dir; /* advance errorptr to current column */
709 }
710 /* Post-loop cleanup: we must unload the final error value into the
711 * final fserrors[] entry. Note we need not unload belowerr because
712 * it is for the dummy column before or after the actual array.
713 */
714 errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
715 }
716 cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
717 }
718}
719
720
721/*
722 * Allocate workspace for Floyd-Steinberg errors.
723 */
724
725LOCAL(void)
726alloc_fs_workspace (j_decompress_ptr cinfo)
727{
728 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
729 size_t arraysize;
730 int i;
731
732 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
733 for (i = 0; i < cinfo->out_color_components; i++) {
734 cquantize->fserrors[i] = (FSERRPTR)
735 (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
736 }
737}
738
739
740/*
741 * Initialize for one-pass color quantization.
742 */
743
744METHODDEF(void)
745start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
746{
747 my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
748 size_t arraysize;
749 int i;
750
751 /* Install my colormap. */
752 cinfo->colormap = cquantize->sv_colormap;
753 cinfo->actual_number_of_colors = cquantize->sv_actual;
754
755 /* Initialize for desired dithering mode. */
756 switch (cinfo->dither_mode) {
757 case JDITHER_NONE:
758 if (cinfo->out_color_components == 3)
759 cquantize->pub.color_quantize = color_quantize3;
760 else
761 cquantize->pub.color_quantize = color_quantize;
762 break;
763 case JDITHER_ORDERED:
764 if (cinfo->out_color_components == 3)
765 cquantize->pub.color_quantize = quantize3_ord_dither;
766 else
767 cquantize->pub.color_quantize = quantize_ord_dither;
768 cquantize->row_index = 0; /* initialize state for ordered dither */
769 /* If user changed to ordered dither from another mode,
770 * we must recreate the color index table with padding.
771 * This will cost extra space, but probably isn't very likely.
772 */
773 if (! cquantize->is_padded)
774 create_colorindex(cinfo);
775 /* Create ordered-dither tables if we didn't already. */
776 if (cquantize->odither[0] == NULL)
777 create_odither_tables(cinfo);
778 break;
779 case JDITHER_FS:
780 cquantize->pub.color_quantize = quantize_fs_dither;
781 cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
782 /* Allocate Floyd-Steinberg workspace if didn't already. */
783 if (cquantize->fserrors[0] == NULL)
784 alloc_fs_workspace(cinfo);
785 /* Initialize the propagated errors to zero. */
786 arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
787 for (i = 0; i < cinfo->out_color_components; i++)
788 jzero_far((void FAR *) cquantize->fserrors[i], arraysize);
789 break;
790 default:
791 ERREXIT(cinfo, JERR_NOT_COMPILED);
792 break;
793 }
794}
795
796
797/*
798 * Finish up at the end of the pass.
799 */
800
801METHODDEF(void)
802finish_pass_1_quant (j_decompress_ptr cinfo)
803{
804 /* no work in 1-pass case */
805}
806
807
808/*
809 * Switch to a new external colormap between output passes.
810 * Shouldn't get to this module!
811 */
812
813METHODDEF(void)
814new_color_map_1_quant (j_decompress_ptr cinfo)
815{
816 ERREXIT(cinfo, JERR_MODE_CHANGE);
817}
818
819
820/*
821 * Module initialization routine for 1-pass color quantization.
822 */
823
824GLOBAL(void)
825jinit_1pass_quantizer (j_decompress_ptr cinfo)
826{
827 my_cquantize_ptr cquantize;
828
829 cquantize = (my_cquantize_ptr)
830 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
831 SIZEOF(my_cquantizer));
832 cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
833 cquantize->pub.start_pass = start_pass_1_quant;
834 cquantize->pub.finish_pass = finish_pass_1_quant;
835 cquantize->pub.new_color_map = new_color_map_1_quant;
836 cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
837 cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
838
839 /* Make sure my internal arrays won't overflow */
840 if (cinfo->out_color_components > MAX_Q_COMPS)
841 ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
842 /* Make sure colormap indexes can be represented by JSAMPLEs */
843 if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
844 ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
845
846 /* Create the colormap and color index table. */
847 create_colormap(cinfo);
848 create_colorindex(cinfo);
849
850 /* Allocate Floyd-Steinberg workspace now if requested.
851 * We do this now since it is FAR storage and may affect the memory
852 * manager's space calculations. If the user changes to FS dither
853 * mode in a later pass, we will allocate the space then, and will
854 * possibly overrun the max_memory_to_use setting.
855 */
856 if (cinfo->dither_mode == JDITHER_FS)
857 alloc_fs_workspace(cinfo);
858}
859
860#endif /* QUANT_1PASS_SUPPORTED */
861