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
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
128#if BITS_IN_JSAMPLE == 8
129typedef INT16 FSERROR; /* 16 bits should be enough */
130typedef int LOCFSERROR; /* use 'int' for calculation temps */
131#else
132typedef JLONG FSERROR; /* may need more than 16 bits */
133typedef JLONG LOCFSERROR; /* be sure calculation temps are big enough */
134#endif
135
136typedef FSERROR *FSERRPTR; /* pointer to error array */
137
138
139/* Private subobject */
140
141#define MAX_Q_COMPS 4 /* max components I can handle */
142
143typedef 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
168typedef 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
186LOCAL(int)
187select_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
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)(((JLONG)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)(((JLONG)(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, 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
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 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
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 += colorindex[ci][*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 = colorindex0[*ptrin++];
510 pixcode += colorindex1[*ptrin++];
511 pixcode += colorindex2[*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 *)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[*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 = colorindex0[(*input_ptr++) + dither0[col_index]];
599 pixcode += colorindex1[(*input_ptr++) + dither1[col_index]];
600 pixcode += colorindex2[(*input_ptr++) + dither2[col_index]];
601 *output_ptr++ = (JSAMPLE)pixcode;
602 col_index = (col_index + 1) & ODITHER_MASK;
603 }
604 row_index = (row_index + 1) & ODITHER_MASK;
605 cquantize->row_index = row_index;
606 }
607}
608
609
610METHODDEF(void)
611quantize_fs_dither(j_decompress_ptr cinfo, JSAMPARRAY input_buf,
612 JSAMPARRAY output_buf, int num_rows)
613/* General case, with Floyd-Steinberg dithering */
614{
615 my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
616 register LOCFSERROR cur; /* current error or pixel value */
617 LOCFSERROR belowerr; /* error for pixel below cur */
618 LOCFSERROR bpreverr; /* error for below/prev col */
619 LOCFSERROR bnexterr; /* error for below/next col */
620 LOCFSERROR delta;
621 register FSERRPTR errorptr; /* => fserrors[] at column before current */
622 register JSAMPROW input_ptr;
623 register JSAMPROW output_ptr;
624 JSAMPROW colorindex_ci;
625 JSAMPROW colormap_ci;
626 int pixcode;
627 int nc = cinfo->out_color_components;
628 int dir; /* 1 for left-to-right, -1 for right-to-left */
629 int dirnc; /* dir * nc */
630 int ci;
631 int row;
632 JDIMENSION col;
633 JDIMENSION width = cinfo->output_width;
634 JSAMPLE *range_limit = cinfo->sample_range_limit;
635 SHIFT_TEMPS
636
637 for (row = 0; row < num_rows; row++) {
638 /* Initialize output values to 0 so can process components separately */
639 jzero_far((void *)output_buf[row], (size_t)(width * sizeof(JSAMPLE)));
640 for (ci = 0; ci < nc; ci++) {
641 input_ptr = input_buf[row] + ci;
642 output_ptr = output_buf[row];
643 if (cquantize->on_odd_row) {
644 /* work right to left in this row */
645 input_ptr += (width - 1) * nc; /* so point to rightmost pixel */
646 output_ptr += width - 1;
647 dir = -1;
648 dirnc = -nc;
649 errorptr = cquantize->fserrors[ci] + (width + 1); /* => entry after last column */
650 } else {
651 /* work left to right in this row */
652 dir = 1;
653 dirnc = nc;
654 errorptr = cquantize->fserrors[ci]; /* => entry before first column */
655 }
656 colorindex_ci = cquantize->colorindex[ci];
657 colormap_ci = cquantize->sv_colormap[ci];
658 /* Preset error values: no error propagated to first pixel from left */
659 cur = 0;
660 /* and no error propagated to row below yet */
661 belowerr = bpreverr = 0;
662
663 for (col = width; col > 0; col--) {
664 /* cur holds the error propagated from the previous pixel on the
665 * current line. Add the error propagated from the previous line
666 * to form the complete error correction term for this pixel, and
667 * round the error term (which is expressed * 16) to an integer.
668 * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
669 * for either sign of the error value.
670 * Note: errorptr points to *previous* column's array entry.
671 */
672 cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
673 /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
674 * The maximum error is +- MAXJSAMPLE; this sets the required size
675 * of the range_limit array.
676 */
677 cur += *input_ptr;
678 cur = range_limit[cur];
679 /* Select output value, accumulate into output code for this pixel */
680 pixcode = colorindex_ci[cur];
681 *output_ptr += (JSAMPLE)pixcode;
682 /* Compute actual representation error at this pixel */
683 /* Note: we can do this even though we don't have the final */
684 /* pixel code, because the colormap is orthogonal. */
685 cur -= colormap_ci[pixcode];
686 /* Compute error fractions to be propagated to adjacent pixels.
687 * Add these into the running sums, and simultaneously shift the
688 * next-line error sums left by 1 column.
689 */
690 bnexterr = cur;
691 delta = cur * 2;
692 cur += delta; /* form error * 3 */
693 errorptr[0] = (FSERROR)(bpreverr + cur);
694 cur += delta; /* form error * 5 */
695 bpreverr = belowerr + cur;
696 belowerr = bnexterr;
697 cur += delta; /* form error * 7 */
698 /* At this point cur contains the 7/16 error value to be propagated
699 * to the next pixel on the current line, and all the errors for the
700 * next line have been shifted over. We are therefore ready to move on.
701 */
702 input_ptr += dirnc; /* advance input ptr to next column */
703 output_ptr += dir; /* advance output ptr to next column */
704 errorptr += dir; /* advance errorptr to current column */
705 }
706 /* Post-loop cleanup: we must unload the final error value into the
707 * final fserrors[] entry. Note we need not unload belowerr because
708 * it is for the dummy column before or after the actual array.
709 */
710 errorptr[0] = (FSERROR)bpreverr; /* unload prev err into array */
711 }
712 cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
713 }
714}
715
716
717/*
718 * Allocate workspace for Floyd-Steinberg errors.
719 */
720
721LOCAL(void)
722alloc_fs_workspace(j_decompress_ptr cinfo)
723{
724 my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
725 size_t arraysize;
726 int i;
727
728 arraysize = (size_t)((cinfo->output_width + 2) * sizeof(FSERROR));
729 for (i = 0; i < cinfo->out_color_components; i++) {
730 cquantize->fserrors[i] = (FSERRPTR)
731 (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE, arraysize);
732 }
733}
734
735
736/*
737 * Initialize for one-pass color quantization.
738 */
739
740METHODDEF(void)
741start_pass_1_quant(j_decompress_ptr cinfo, boolean is_pre_scan)
742{
743 my_cquantize_ptr cquantize = (my_cquantize_ptr)cinfo->cquantize;
744 size_t arraysize;
745 int i;
746
747 /* Install my colormap. */
748 cinfo->colormap = cquantize->sv_colormap;
749 cinfo->actual_number_of_colors = cquantize->sv_actual;
750
751 /* Initialize for desired dithering mode. */
752 switch (cinfo->dither_mode) {
753 case JDITHER_NONE:
754 if (cinfo->out_color_components == 3)
755 cquantize->pub.color_quantize = color_quantize3;
756 else
757 cquantize->pub.color_quantize = color_quantize;
758 break;
759 case JDITHER_ORDERED:
760 if (cinfo->out_color_components == 3)
761 cquantize->pub.color_quantize = quantize3_ord_dither;
762 else
763 cquantize->pub.color_quantize = quantize_ord_dither;
764 cquantize->row_index = 0; /* initialize state for ordered dither */
765 /* If user changed to ordered dither from another mode,
766 * we must recreate the color index table with padding.
767 * This will cost extra space, but probably isn't very likely.
768 */
769 if (!cquantize->is_padded)
770 create_colorindex(cinfo);
771 /* Create ordered-dither tables if we didn't already. */
772 if (cquantize->odither[0] == NULL)
773 create_odither_tables(cinfo);
774 break;
775 case JDITHER_FS:
776 cquantize->pub.color_quantize = quantize_fs_dither;
777 cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
778 /* Allocate Floyd-Steinberg workspace if didn't already. */
779 if (cquantize->fserrors[0] == NULL)
780 alloc_fs_workspace(cinfo);
781 /* Initialize the propagated errors to zero. */
782 arraysize = (size_t)((cinfo->output_width + 2) * sizeof(FSERROR));
783 for (i = 0; i < cinfo->out_color_components; i++)
784 jzero_far((void *)cquantize->fserrors[i], arraysize);
785 break;
786 default:
787 ERREXIT(cinfo, JERR_NOT_COMPILED);
788 break;
789 }
790}
791
792
793/*
794 * Finish up at the end of the pass.
795 */
796
797METHODDEF(void)
798finish_pass_1_quant(j_decompress_ptr cinfo)
799{
800 /* no work in 1-pass case */
801}
802
803
804/*
805 * Switch to a new external colormap between output passes.
806 * Shouldn't get to this module!
807 */
808
809METHODDEF(void)
810new_color_map_1_quant(j_decompress_ptr cinfo)
811{
812 ERREXIT(cinfo, JERR_MODE_CHANGE);
813}
814
815
816/*
817 * Module initialization routine for 1-pass color quantization.
818 */
819
820GLOBAL(void)
821jinit_1pass_quantizer(j_decompress_ptr cinfo)
822{
823 my_cquantize_ptr cquantize;
824
825 cquantize = (my_cquantize_ptr)
826 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
827 sizeof(my_cquantizer));
828 cinfo->cquantize = (struct jpeg_color_quantizer *)cquantize;
829 cquantize->pub.start_pass = start_pass_1_quant;
830 cquantize->pub.finish_pass = finish_pass_1_quant;
831 cquantize->pub.new_color_map = new_color_map_1_quant;
832 cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
833 cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
834
835 /* Make sure my internal arrays won't overflow */
836 if (cinfo->out_color_components > MAX_Q_COMPS)
837 ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
838 /* Make sure colormap indexes can be represented by JSAMPLEs */
839 if (cinfo->desired_number_of_colors > (MAXJSAMPLE + 1))
840 ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE + 1);
841
842 /* Create the colormap and color index table. */
843 create_colormap(cinfo);
844 create_colorindex(cinfo);
845
846 /* Allocate Floyd-Steinberg workspace now if requested.
847 * We do this now since it may affect the memory manager's space
848 * calculations. If the user changes to FS dither mode in a later pass, we
849 * will allocate the space then, and will possibly overrun the
850 * max_memory_to_use setting.
851 */
852 if (cinfo->dither_mode == JDITHER_FS)
853 alloc_fs_workspace(cinfo);
854}
855
856#endif /* QUANT_1PASS_SUPPORTED */
857