1 : /*
2 : * jquant1.c
3 : *
4 : * Copyright (C) 1991-1996, Thomas G. Lane.
5 : * Copyright (C) 2009, D. R. Commander
6 : * This file is part of the Independent JPEG Group's software.
7 : * For conditions of distribution and use, see the accompanying README file.
8 : *
9 : * This file contains 1-pass color quantization (color mapping) routines.
10 : * These routines provide mapping to a fixed color map using equally spaced
11 : * color values. Optional Floyd-Steinberg or ordered dithering is available.
12 : */
13 :
14 : #define JPEG_INTERNALS
15 : #include "jinclude.h"
16 : #include "jpeglib.h"
17 :
18 : #ifdef QUANT_1PASS_SUPPORTED
19 :
20 :
21 : /*
22 : * The main purpose of 1-pass quantization is to provide a fast, if not very
23 : * high quality, colormapped output capability. A 2-pass quantizer usually
24 : * gives better visual quality; however, for quantized grayscale output this
25 : * quantizer is perfectly adequate. Dithering is highly recommended with this
26 : * quantizer, though you can turn it off if you really want to.
27 : *
28 : * In 1-pass quantization the colormap must be chosen in advance of seeing the
29 : * image. We use a map consisting of all combinations of Ncolors[i] color
30 : * values for the i'th component. The Ncolors[] values are chosen so that
31 : * their product, the total number of colors, is no more than that requested.
32 : * (In most cases, the product will be somewhat less.)
33 : *
34 : * Since the colormap is orthogonal, the representative value for each color
35 : * component can be determined without considering the other components;
36 : * then these indexes can be combined into a colormap index by a standard
37 : * N-dimensional-array-subscript calculation. Most of the arithmetic involved
38 : * can be precalculated and stored in the lookup table colorindex[].
39 : * colorindex[i][j] maps pixel value j in component i to the nearest
40 : * representative value (grid plane) for that component; this index is
41 : * multiplied by the array stride for component i, so that the
42 : * index of the colormap entry closest to a given pixel value is just
43 : * sum( colorindex[component-number][pixel-component-value] )
44 : * Aside from being fast, this scheme allows for variable spacing between
45 : * representative values with no additional lookup cost.
46 : *
47 : * If gamma correction has been applied in color conversion, it might be wise
48 : * to adjust the color grid spacing so that the representative colors are
49 : * equidistant in linear space. At this writing, gamma correction is not
50 : * implemented by jdcolor, so nothing is done here.
51 : */
52 :
53 :
54 : /* Declarations for ordered dithering.
55 : *
56 : * We use a standard 16x16 ordered dither array. The basic concept of ordered
57 : * dithering is described in many references, for instance Dale Schumacher's
58 : * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
59 : * In place of Schumacher's comparisons against a "threshold" value, we add a
60 : * "dither" value to the input pixel and then round the result to the nearest
61 : * output value. The dither value is equivalent to (0.5 - threshold) times
62 : * the distance between output values. For ordered dithering, we assume that
63 : * the output colors are equally spaced; if not, results will probably be
64 : * worse, since the dither may be too much or too little at a given point.
65 : *
66 : * The normal calculation would be to form pixel value + dither, range-limit
67 : * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.
68 : * We can skip the separate range-limiting step by extending the colorindex
69 : * table in both directions.
70 : */
71 :
72 : #define ODITHER_SIZE 16 /* dimension of dither matrix */
73 : /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */
74 : #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */
75 : #define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */
76 :
77 : typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
78 : typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
79 :
80 : static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
81 : /* Bayer's order-4 dither array. Generated by the code given in
82 : * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
83 : * The values in this array must range from 0 to ODITHER_CELLS-1.
84 : */
85 : { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 },
86 : { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
87 : { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
88 : { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
89 : { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 },
90 : { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
91 : { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
92 : { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
93 : { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 },
94 : { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
95 : { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
96 : { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
97 : { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 },
98 : { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
99 : { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
100 : { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
101 : };
102 :
103 :
104 : /* Declarations for Floyd-Steinberg dithering.
105 : *
106 : * Errors are accumulated into the array fserrors[], at a resolution of
107 : * 1/16th of a pixel count. The error at a given pixel is propagated
108 : * to its not-yet-processed neighbors using the standard F-S fractions,
109 : * ... (here) 7/16
110 : * 3/16 5/16 1/16
111 : * We work left-to-right on even rows, right-to-left on odd rows.
112 : *
113 : * We can get away with a single array (holding one row's worth of errors)
114 : * by using it to store the current row's errors at pixel columns not yet
115 : * processed, but the next row's errors at columns already processed. We
116 : * need only a few extra variables to hold the errors immediately around the
117 : * current column. (If we are lucky, those variables are in registers, but
118 : * even if not, they're probably cheaper to access than array elements are.)
119 : *
120 : * The fserrors[] array is indexed [component#][position].
121 : * We provide (#columns + 2) entries per component; the extra entry at each
122 : * end saves us from special-casing the first and last pixels.
123 : *
124 : * Note: on a wide image, we might not have enough room in a PC's near data
125 : * segment to hold the error array; so it is allocated with alloc_large.
126 : */
127 :
128 : #if BITS_IN_JSAMPLE == 8
129 : typedef INT16 FSERROR; /* 16 bits should be enough */
130 : typedef int LOCFSERROR; /* use 'int' for calculation temps */
131 : #else
132 : typedef INT32 FSERROR; /* may need more than 16 bits */
133 : typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */
134 : #endif
135 :
136 : typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */
137 :
138 :
139 : /* Private subobject */
140 :
141 : #define MAX_Q_COMPS 4 /* max components I can handle */
142 :
143 : typedef struct {
144 : struct jpeg_color_quantizer pub; /* public fields */
145 :
146 : /* Initially allocated colormap is saved here */
147 : JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */
148 : int sv_actual; /* number of entries in use */
149 :
150 : JSAMPARRAY colorindex; /* Precomputed mapping for speed */
151 : /* colorindex[i][j] = index of color closest to pixel value j in component i,
152 : * premultiplied as described above. Since colormap indexes must fit into
153 : * JSAMPLEs, the entries of this array will too.
154 : */
155 : boolean is_padded; /* is the colorindex padded for odither? */
156 :
157 : int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */
158 :
159 : /* Variables for ordered dithering */
160 : int row_index; /* cur row's vertical index in dither matrix */
161 : ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */
162 :
163 : /* Variables for Floyd-Steinberg dithering */
164 : FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */
165 : boolean on_odd_row; /* flag to remember which row we are on */
166 : } my_cquantizer;
167 :
168 : typedef my_cquantizer * my_cquantize_ptr;
169 :
170 :
171 : /*
172 : * Policy-making subroutines for create_colormap and create_colorindex.
173 : * These routines determine the colormap to be used. The rest of the module
174 : * only assumes that the colormap is orthogonal.
175 : *
176 : * * select_ncolors decides how to divvy up the available colors
177 : * among the components.
178 : * * output_value defines the set of representative values for a component.
179 : * * largest_input_value defines the mapping from input values to
180 : * representative values for a component.
181 : * Note that the latter two routines may impose different policies for
182 : * different components, though this is not currently done.
183 : */
184 :
185 :
186 : LOCAL(int)
187 0 : select_ncolors (j_decompress_ptr cinfo, int Ncolors[])
188 : /* Determine allocation of desired colors to components, */
189 : /* and fill in Ncolors[] array to indicate choice. */
190 : /* Return value is total number of colors (product of Ncolors[] values). */
191 : {
192 0 : int nc = cinfo->out_color_components; /* number of color components */
193 0 : int max_colors = cinfo->desired_number_of_colors;
194 : int total_colors, iroot, i, j;
195 : boolean changed;
196 : long temp;
197 0 : int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
198 0 : RGB_order[0] = rgb_green[cinfo->out_color_space];
199 0 : RGB_order[1] = rgb_red[cinfo->out_color_space];
200 0 : 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 0 : iroot = 1;
205 : do {
206 0 : iroot++;
207 0 : temp = iroot; /* set temp = iroot ** nc */
208 0 : for (i = 1; i < nc; i++)
209 0 : temp *= iroot;
210 0 : } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */
211 0 : iroot--; /* now iroot = floor(root) */
212 :
213 : /* Must have at least 2 color values per component */
214 0 : if (iroot < 2)
215 0 : ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);
216 :
217 : /* Initialize to iroot color values for each component */
218 0 : total_colors = 1;
219 0 : for (i = 0; i < nc; i++) {
220 0 : Ncolors[i] = iroot;
221 0 : 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 0 : changed = FALSE;
231 0 : for (i = 0; i < nc; i++) {
232 0 : j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
233 : /* calculate new total_colors if Ncolors[j] is incremented */
234 0 : temp = total_colors / Ncolors[j];
235 0 : temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */
236 0 : if (temp > (long) max_colors)
237 0 : break; /* won't fit, done with this pass */
238 0 : Ncolors[j]++; /* OK, apply the increment */
239 0 : total_colors = (int) temp;
240 0 : changed = TRUE;
241 : }
242 0 : } while (changed);
243 :
244 0 : return total_colors;
245 : }
246 :
247 :
248 : LOCAL(int)
249 0 : 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 0 : return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj);
259 : }
260 :
261 :
262 : LOCAL(int)
263 0 : 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 0 : return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));
269 : }
270 :
271 :
272 : /*
273 : * Create the colormap.
274 : */
275 :
276 : LOCAL(void)
277 0 : create_colormap (j_decompress_ptr cinfo)
278 : {
279 0 : 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 0 : total_colors = select_ncolors(cinfo, cquantize->Ncolors);
286 :
287 : /* Report selected color counts */
288 0 : if (cinfo->out_color_components == 3)
289 0 : TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,
290 : total_colors, cquantize->Ncolors[0],
291 : cquantize->Ncolors[1], cquantize->Ncolors[2]);
292 : else
293 0 : 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 0 : colormap = (*cinfo->mem->alloc_sarray)
300 0 : ((j_common_ptr) cinfo, JPOOL_IMAGE,
301 0 : (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 0 : blkdist = total_colors;
306 :
307 0 : for (i = 0; i < cinfo->out_color_components; i++) {
308 : /* fill in colormap entries for i'th color component */
309 0 : nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
310 0 : blksize = blkdist / nci;
311 0 : for (j = 0; j < nci; j++) {
312 : /* Compute j'th output value (out of nci) for component */
313 0 : val = output_value(cinfo, i, j, nci-1);
314 : /* Fill in all colormap entries that have this value of this component */
315 0 : for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
316 : /* fill in blksize entries beginning at ptr */
317 0 : for (k = 0; k < blksize; k++)
318 0 : colormap[i][ptr+k] = (JSAMPLE) val;
319 : }
320 : }
321 0 : 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 0 : cquantize->sv_colormap = colormap;
328 0 : cquantize->sv_actual = total_colors;
329 0 : }
330 :
331 :
332 : /*
333 : * Create the color index table.
334 : */
335 :
336 : LOCAL(void)
337 0 : create_colorindex (j_decompress_ptr cinfo)
338 : {
339 0 : 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 0 : if (cinfo->dither_mode == JDITHER_ORDERED) {
349 0 : pad = MAXJSAMPLE*2;
350 0 : cquantize->is_padded = TRUE;
351 : } else {
352 0 : pad = 0;
353 0 : cquantize->is_padded = FALSE;
354 : }
355 :
356 0 : cquantize->colorindex = (*cinfo->mem->alloc_sarray)
357 0 : ((j_common_ptr) cinfo, JPOOL_IMAGE,
358 0 : (JDIMENSION) (MAXJSAMPLE+1 + pad),
359 0 : (JDIMENSION) cinfo->out_color_components);
360 :
361 : /* blksize is number of adjacent repeated entries for a component */
362 0 : blksize = cquantize->sv_actual;
363 :
364 0 : for (i = 0; i < cinfo->out_color_components; i++) {
365 : /* fill in colorindex entries for i'th color component */
366 0 : nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
367 0 : blksize = blksize / nci;
368 :
369 : /* adjust colorindex pointers to provide padding at negative indexes. */
370 0 : if (pad)
371 0 : 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 0 : indexptr = cquantize->colorindex[i];
376 0 : val = 0;
377 0 : k = largest_input_value(cinfo, i, 0, nci-1);
378 0 : for (j = 0; j <= MAXJSAMPLE; j++) {
379 0 : while (j > k) /* advance val if past boundary */
380 0 : k = largest_input_value(cinfo, i, ++val, nci-1);
381 : /* premultiply so that no multiplication needed in main processing */
382 0 : indexptr[j] = (JSAMPLE) (val * blksize);
383 : }
384 : /* Pad at both ends if necessary */
385 0 : if (pad)
386 0 : for (j = 1; j <= MAXJSAMPLE; j++) {
387 0 : indexptr[-j] = indexptr[0];
388 0 : indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];
389 : }
390 : }
391 0 : }
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 0 : 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 0 : odither = (ODITHER_MATRIX_PTR)
407 0 : (*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 0 : den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1));
415 0 : for (j = 0; j < ODITHER_SIZE; j++) {
416 0 : for (k = 0; k < ODITHER_SIZE; k++) {
417 0 : num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))
418 0 : * MAXJSAMPLE;
419 : /* Ensure round towards zero despite C's lack of consistency
420 : * about rounding negative values in integer division...
421 : */
422 0 : odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);
423 : }
424 : }
425 0 : 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 0 : create_odither_tables (j_decompress_ptr cinfo)
437 : {
438 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
439 : ODITHER_MATRIX_PTR odither;
440 : int i, j, nci;
441 :
442 0 : for (i = 0; i < cinfo->out_color_components; i++) {
443 0 : nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
444 0 : odither = NULL; /* search for matching prior component */
445 0 : for (j = 0; j < i; j++) {
446 0 : if (nci == cquantize->Ncolors[j]) {
447 0 : odither = cquantize->odither[j];
448 0 : break;
449 : }
450 : }
451 0 : if (odither == NULL) /* need a new table? */
452 0 : odither = make_odither_array(cinfo, nci);
453 0 : cquantize->odither[i] = odither;
454 : }
455 0 : }
456 :
457 :
458 : /*
459 : * Map some rows of pixels to the output colormapped representation.
460 : */
461 :
462 : METHODDEF(void)
463 0 : color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
464 : JSAMPARRAY output_buf, int num_rows)
465 : /* General case, no dithering */
466 : {
467 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
468 0 : JSAMPARRAY colorindex = cquantize->colorindex;
469 : register int pixcode, ci;
470 : register JSAMPROW ptrin, ptrout;
471 : int row;
472 : JDIMENSION col;
473 0 : JDIMENSION width = cinfo->output_width;
474 0 : register int nc = cinfo->out_color_components;
475 :
476 0 : for (row = 0; row < num_rows; row++) {
477 0 : ptrin = input_buf[row];
478 0 : ptrout = output_buf[row];
479 0 : for (col = width; col > 0; col--) {
480 0 : pixcode = 0;
481 0 : for (ci = 0; ci < nc; ci++) {
482 0 : pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);
483 : }
484 0 : *ptrout++ = (JSAMPLE) pixcode;
485 : }
486 : }
487 0 : }
488 :
489 :
490 : METHODDEF(void)
491 0 : color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
492 : JSAMPARRAY output_buf, int num_rows)
493 : /* Fast path for out_color_components==3, no dithering */
494 : {
495 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
496 : register int pixcode;
497 : register JSAMPROW ptrin, ptrout;
498 0 : JSAMPROW colorindex0 = cquantize->colorindex[0];
499 0 : JSAMPROW colorindex1 = cquantize->colorindex[1];
500 0 : JSAMPROW colorindex2 = cquantize->colorindex[2];
501 : int row;
502 : JDIMENSION col;
503 0 : JDIMENSION width = cinfo->output_width;
504 :
505 0 : for (row = 0; row < num_rows; row++) {
506 0 : ptrin = input_buf[row];
507 0 : ptrout = output_buf[row];
508 0 : for (col = width; col > 0; col--) {
509 0 : pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);
510 0 : pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);
511 0 : pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);
512 0 : *ptrout++ = (JSAMPLE) pixcode;
513 : }
514 : }
515 0 : }
516 :
517 :
518 : METHODDEF(void)
519 0 : quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
520 : JSAMPARRAY output_buf, int num_rows)
521 : /* General case, with ordered dithering */
522 : {
523 0 : 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 0 : int nc = cinfo->out_color_components;
530 : int ci;
531 : int row;
532 : JDIMENSION col;
533 0 : JDIMENSION width = cinfo->output_width;
534 :
535 0 : for (row = 0; row < num_rows; row++) {
536 : /* Initialize output values to 0 so can process components separately */
537 0 : jzero_far((void FAR *) output_buf[row],
538 : (size_t) (width * SIZEOF(JSAMPLE)));
539 0 : row_index = cquantize->row_index;
540 0 : for (ci = 0; ci < nc; ci++) {
541 0 : input_ptr = input_buf[row] + ci;
542 0 : output_ptr = output_buf[row];
543 0 : colorindex_ci = cquantize->colorindex[ci];
544 0 : dither = cquantize->odither[ci][row_index];
545 0 : col_index = 0;
546 :
547 0 : 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 0 : *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];
556 0 : input_ptr += nc;
557 0 : output_ptr++;
558 0 : col_index = (col_index + 1) & ODITHER_MASK;
559 : }
560 : }
561 : /* Advance row index for next row */
562 0 : row_index = (row_index + 1) & ODITHER_MASK;
563 0 : cquantize->row_index = row_index;
564 : }
565 0 : }
566 :
567 :
568 : METHODDEF(void)
569 0 : quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
570 : JSAMPARRAY output_buf, int num_rows)
571 : /* Fast path for out_color_components==3, with ordered dithering */
572 : {
573 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
574 : register int pixcode;
575 : register JSAMPROW input_ptr;
576 : register JSAMPROW output_ptr;
577 0 : JSAMPROW colorindex0 = cquantize->colorindex[0];
578 0 : JSAMPROW colorindex1 = cquantize->colorindex[1];
579 0 : 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 0 : JDIMENSION width = cinfo->output_width;
587 :
588 0 : for (row = 0; row < num_rows; row++) {
589 0 : row_index = cquantize->row_index;
590 0 : input_ptr = input_buf[row];
591 0 : output_ptr = output_buf[row];
592 0 : dither0 = cquantize->odither[0][row_index];
593 0 : dither1 = cquantize->odither[1][row_index];
594 0 : dither2 = cquantize->odither[2][row_index];
595 0 : col_index = 0;
596 :
597 0 : for (col = width; col > 0; col--) {
598 0 : pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
599 : dither0[col_index]]);
600 0 : pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
601 : dither1[col_index]]);
602 0 : pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
603 : dither2[col_index]]);
604 0 : *output_ptr++ = (JSAMPLE) pixcode;
605 0 : col_index = (col_index + 1) & ODITHER_MASK;
606 : }
607 0 : row_index = (row_index + 1) & ODITHER_MASK;
608 0 : cquantize->row_index = row_index;
609 : }
610 0 : }
611 :
612 :
613 : METHODDEF(void)
614 0 : quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
615 : JSAMPARRAY output_buf, int num_rows)
616 : /* General case, with Floyd-Steinberg dithering */
617 : {
618 0 : 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 0 : 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 0 : JDIMENSION width = cinfo->output_width;
637 0 : JSAMPLE *range_limit = cinfo->sample_range_limit;
638 : SHIFT_TEMPS
639 :
640 0 : for (row = 0; row < num_rows; row++) {
641 : /* Initialize output values to 0 so can process components separately */
642 0 : jzero_far((void FAR *) output_buf[row],
643 : (size_t) (width * SIZEOF(JSAMPLE)));
644 0 : for (ci = 0; ci < nc; ci++) {
645 0 : input_ptr = input_buf[row] + ci;
646 0 : output_ptr = output_buf[row];
647 0 : if (cquantize->on_odd_row) {
648 : /* work right to left in this row */
649 0 : input_ptr += (width-1) * nc; /* so point to rightmost pixel */
650 0 : output_ptr += width-1;
651 0 : dir = -1;
652 0 : dirnc = -nc;
653 0 : errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */
654 : } else {
655 : /* work left to right in this row */
656 0 : dir = 1;
657 0 : dirnc = nc;
658 0 : errorptr = cquantize->fserrors[ci]; /* => entry before first column */
659 : }
660 0 : colorindex_ci = cquantize->colorindex[ci];
661 0 : colormap_ci = cquantize->sv_colormap[ci];
662 : /* Preset error values: no error propagated to first pixel from left */
663 0 : cur = 0;
664 : /* and no error propagated to row below yet */
665 0 : belowerr = bpreverr = 0;
666 :
667 0 : 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 0 : 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 0 : cur += GETJSAMPLE(*input_ptr);
682 0 : cur = GETJSAMPLE(range_limit[cur]);
683 : /* Select output value, accumulate into output code for this pixel */
684 0 : pixcode = GETJSAMPLE(colorindex_ci[cur]);
685 0 : *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 0 : 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 0 : bnexterr = cur;
695 0 : delta = cur * 2;
696 0 : cur += delta; /* form error * 3 */
697 0 : errorptr[0] = (FSERROR) (bpreverr + cur);
698 0 : cur += delta; /* form error * 5 */
699 0 : bpreverr = belowerr + cur;
700 0 : belowerr = bnexterr;
701 0 : 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 0 : input_ptr += dirnc; /* advance input ptr to next column */
707 0 : output_ptr += dir; /* advance output ptr to next column */
708 0 : 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 0 : errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
715 : }
716 0 : cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
717 : }
718 0 : }
719 :
720 :
721 : /*
722 : * Allocate workspace for Floyd-Steinberg errors.
723 : */
724 :
725 : LOCAL(void)
726 0 : alloc_fs_workspace (j_decompress_ptr cinfo)
727 : {
728 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
729 : size_t arraysize;
730 : int i;
731 :
732 0 : arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
733 0 : for (i = 0; i < cinfo->out_color_components; i++) {
734 0 : cquantize->fserrors[i] = (FSERRPTR)
735 0 : (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
736 : }
737 0 : }
738 :
739 :
740 : /*
741 : * Initialize for one-pass color quantization.
742 : */
743 :
744 : METHODDEF(void)
745 0 : start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
746 : {
747 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
748 : size_t arraysize;
749 : int i;
750 :
751 : /* Install my colormap. */
752 0 : cinfo->colormap = cquantize->sv_colormap;
753 0 : cinfo->actual_number_of_colors = cquantize->sv_actual;
754 :
755 : /* Initialize for desired dithering mode. */
756 0 : switch (cinfo->dither_mode) {
757 : case JDITHER_NONE:
758 0 : if (cinfo->out_color_components == 3)
759 0 : cquantize->pub.color_quantize = color_quantize3;
760 : else
761 0 : cquantize->pub.color_quantize = color_quantize;
762 0 : break;
763 : case JDITHER_ORDERED:
764 0 : if (cinfo->out_color_components == 3)
765 0 : cquantize->pub.color_quantize = quantize3_ord_dither;
766 : else
767 0 : cquantize->pub.color_quantize = quantize_ord_dither;
768 0 : 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 0 : if (! cquantize->is_padded)
774 0 : create_colorindex(cinfo);
775 : /* Create ordered-dither tables if we didn't already. */
776 0 : if (cquantize->odither[0] == NULL)
777 0 : create_odither_tables(cinfo);
778 0 : break;
779 : case JDITHER_FS:
780 0 : cquantize->pub.color_quantize = quantize_fs_dither;
781 0 : cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
782 : /* Allocate Floyd-Steinberg workspace if didn't already. */
783 0 : if (cquantize->fserrors[0] == NULL)
784 0 : alloc_fs_workspace(cinfo);
785 : /* Initialize the propagated errors to zero. */
786 0 : arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
787 0 : for (i = 0; i < cinfo->out_color_components; i++)
788 0 : jzero_far((void FAR *) cquantize->fserrors[i], arraysize);
789 0 : break;
790 : default:
791 0 : ERREXIT(cinfo, JERR_NOT_COMPILED);
792 0 : break;
793 : }
794 0 : }
795 :
796 :
797 : /*
798 : * Finish up at the end of the pass.
799 : */
800 :
801 : METHODDEF(void)
802 0 : finish_pass_1_quant (j_decompress_ptr cinfo)
803 : {
804 : /* no work in 1-pass case */
805 0 : }
806 :
807 :
808 : /*
809 : * Switch to a new external colormap between output passes.
810 : * Shouldn't get to this module!
811 : */
812 :
813 : METHODDEF(void)
814 0 : new_color_map_1_quant (j_decompress_ptr cinfo)
815 : {
816 0 : ERREXIT(cinfo, JERR_MODE_CHANGE);
817 0 : }
818 :
819 :
820 : /*
821 : * Module initialization routine for 1-pass color quantization.
822 : */
823 :
824 : GLOBAL(void)
825 0 : jinit_1pass_quantizer (j_decompress_ptr cinfo)
826 : {
827 : my_cquantize_ptr cquantize;
828 :
829 0 : cquantize = (my_cquantize_ptr)
830 0 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
831 : SIZEOF(my_cquantizer));
832 0 : cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
833 0 : cquantize->pub.start_pass = start_pass_1_quant;
834 0 : cquantize->pub.finish_pass = finish_pass_1_quant;
835 0 : cquantize->pub.new_color_map = new_color_map_1_quant;
836 0 : cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
837 0 : cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
838 :
839 : /* Make sure my internal arrays won't overflow */
840 0 : if (cinfo->out_color_components > MAX_Q_COMPS)
841 0 : ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
842 : /* Make sure colormap indexes can be represented by JSAMPLEs */
843 0 : if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
844 0 : ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
845 :
846 : /* Create the colormap and color index table. */
847 0 : create_colormap(cinfo);
848 0 : 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 0 : if (cinfo->dither_mode == JDITHER_FS)
857 0 : alloc_fs_workspace(cinfo);
858 0 : }
859 :
860 : #endif /* QUANT_1PASS_SUPPORTED */
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