Line data Source code
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 counters */
78 :
79 : typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
80 : typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
81 :
82 : static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
83 : /* Bayer's order-4 dither array. Generated by the code given in
84 : * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
85 : * The values in this array must range from 0 to ODITHER_CELLS-1.
86 : */
87 : { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 },
88 : { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
89 : { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
90 : { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
91 : { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 },
92 : { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
93 : { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
94 : { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
95 : { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 },
96 : { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
97 : { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
98 : { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
99 : { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 },
100 : { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
101 : { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
102 : { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
103 : };
104 :
105 :
106 : /* Declarations for Floyd-Steinberg dithering.
107 : *
108 : * Errors are accumulated into the array fserrors[], at a resolution of
109 : * 1/16th of a pixel count. The error at a given pixel is propagated
110 : * to its not-yet-processed neighbors using the standard F-S fractions,
111 : * ... (here) 7/16
112 : * 3/16 5/16 1/16
113 : * We work left-to-right on even rows, right-to-left on odd rows.
114 : *
115 : * We can get away with a single array (holding one row's worth of errors)
116 : * by using it to store the current row's errors at pixel columns not yet
117 : * processed, but the next row's errors at columns already processed. We
118 : * need only a few extra variables to hold the errors immediately around the
119 : * current column. (If we are lucky, those variables are in registers, but
120 : * even if not, they're probably cheaper to access than array elements are.)
121 : *
122 : * The fserrors[] array is indexed [component#][position].
123 : * We provide (#columns + 2) entries per component; the extra entry at each
124 : * end saves us from special-casing the first and last pixels.
125 : */
126 :
127 : #if BITS_IN_JSAMPLE == 8
128 : typedef INT16 FSERROR; /* 16 bits should be enough */
129 : typedef int LOCFSERROR; /* use 'int' for calculation temps */
130 : #else
131 : typedef JLONG FSERROR; /* may need more than 16 bits */
132 : typedef JLONG LOCFSERROR; /* be sure calculation temps are big enough */
133 : #endif
134 :
135 : typedef FSERROR *FSERRPTR; /* pointer to error array */
136 :
137 :
138 : /* Private subobject */
139 :
140 : #define MAX_Q_COMPS 4 /* max components I can handle */
141 :
142 : typedef struct {
143 : struct jpeg_color_quantizer pub; /* public fields */
144 :
145 : /* Initially allocated colormap is saved here */
146 : JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */
147 : int sv_actual; /* number of entries in use */
148 :
149 : JSAMPARRAY colorindex; /* Precomputed mapping for speed */
150 : /* colorindex[i][j] = index of color closest to pixel value j in component i,
151 : * premultiplied as described above. Since colormap indexes must fit into
152 : * JSAMPLEs, the entries of this array will too.
153 : */
154 : boolean is_padded; /* is the colorindex padded for odither? */
155 :
156 : int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */
157 :
158 : /* Variables for ordered dithering */
159 : int row_index; /* cur row's vertical index in dither matrix */
160 : ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */
161 :
162 : /* Variables for Floyd-Steinberg dithering */
163 : FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */
164 : boolean on_odd_row; /* flag to remember which row we are on */
165 : } my_cquantizer;
166 :
167 : typedef my_cquantizer *my_cquantize_ptr;
168 :
169 :
170 : /*
171 : * Policy-making subroutines for create_colormap and create_colorindex.
172 : * These routines determine the colormap to be used. The rest of the module
173 : * only assumes that the colormap is orthogonal.
174 : *
175 : * * select_ncolors decides how to divvy up the available colors
176 : * among the components.
177 : * * output_value defines the set of representative values for a component.
178 : * * largest_input_value defines the mapping from input values to
179 : * representative values for a component.
180 : * Note that the latter two routines may impose different policies for
181 : * different components, though this is not currently done.
182 : */
183 :
184 :
185 : LOCAL(int)
186 0 : select_ncolors (j_decompress_ptr cinfo, int Ncolors[])
187 : /* Determine allocation of desired colors to components, */
188 : /* and fill in Ncolors[] array to indicate choice. */
189 : /* Return value is total number of colors (product of Ncolors[] values). */
190 : {
191 0 : int nc = cinfo->out_color_components; /* number of color components */
192 0 : int max_colors = cinfo->desired_number_of_colors;
193 : int total_colors, iroot, i, j;
194 : boolean changed;
195 : long temp;
196 0 : int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
197 0 : RGB_order[0] = rgb_green[cinfo->out_color_space];
198 0 : RGB_order[1] = rgb_red[cinfo->out_color_space];
199 0 : RGB_order[2] = rgb_blue[cinfo->out_color_space];
200 :
201 : /* We can allocate at least the nc'th root of max_colors per component. */
202 : /* Compute floor(nc'th root of max_colors). */
203 0 : iroot = 1;
204 : do {
205 0 : iroot++;
206 0 : temp = iroot; /* set temp = iroot ** nc */
207 0 : for (i = 1; i < nc; i++)
208 0 : temp *= iroot;
209 0 : } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */
210 0 : iroot--; /* now iroot = floor(root) */
211 :
212 : /* Must have at least 2 color values per component */
213 0 : if (iroot < 2)
214 0 : ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);
215 :
216 : /* Initialize to iroot color values for each component */
217 0 : total_colors = 1;
218 0 : for (i = 0; i < nc; i++) {
219 0 : Ncolors[i] = iroot;
220 0 : total_colors *= iroot;
221 : }
222 : /* We may be able to increment the count for one or more components without
223 : * exceeding max_colors, though we know not all can be incremented.
224 : * Sometimes, the first component can be incremented more than once!
225 : * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
226 : * In RGB colorspace, try to increment G first, then R, then B.
227 : */
228 : do {
229 0 : changed = FALSE;
230 0 : for (i = 0; i < nc; i++) {
231 0 : j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
232 : /* calculate new total_colors if Ncolors[j] is incremented */
233 0 : temp = total_colors / Ncolors[j];
234 0 : temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */
235 0 : if (temp > (long) max_colors)
236 0 : break; /* won't fit, done with this pass */
237 0 : Ncolors[j]++; /* OK, apply the increment */
238 0 : total_colors = (int) temp;
239 0 : changed = TRUE;
240 : }
241 0 : } while (changed);
242 :
243 0 : return total_colors;
244 : }
245 :
246 :
247 : LOCAL(int)
248 0 : output_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
249 : /* Return j'th output value, where j will range from 0 to maxj */
250 : /* The output values must fall in 0..MAXJSAMPLE in increasing order */
251 : {
252 : /* We always provide values 0 and MAXJSAMPLE for each component;
253 : * any additional values are equally spaced between these limits.
254 : * (Forcing the upper and lower values to the limits ensures that
255 : * dithering can't produce a color outside the selected gamut.)
256 : */
257 0 : return (int) (((JLONG) j * MAXJSAMPLE + maxj/2) / maxj);
258 : }
259 :
260 :
261 : LOCAL(int)
262 0 : largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
263 : /* Return largest input value that should map to j'th output value */
264 : /* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */
265 : {
266 : /* Breakpoints are halfway between values returned by output_value */
267 0 : return (int) (((JLONG) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));
268 : }
269 :
270 :
271 : /*
272 : * Create the colormap.
273 : */
274 :
275 : LOCAL(void)
276 0 : create_colormap (j_decompress_ptr cinfo)
277 : {
278 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
279 : JSAMPARRAY colormap; /* Created colormap */
280 : int total_colors; /* Number of distinct output colors */
281 : int i,j,k, nci, blksize, blkdist, ptr, val;
282 :
283 : /* Select number of colors for each component */
284 0 : total_colors = select_ncolors(cinfo, cquantize->Ncolors);
285 :
286 : /* Report selected color counts */
287 0 : if (cinfo->out_color_components == 3)
288 0 : TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,
289 : total_colors, cquantize->Ncolors[0],
290 : cquantize->Ncolors[1], cquantize->Ncolors[2]);
291 : else
292 0 : TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);
293 :
294 : /* Allocate and fill in the colormap. */
295 : /* The colors are ordered in the map in standard row-major order, */
296 : /* i.e. rightmost (highest-indexed) color changes most rapidly. */
297 :
298 0 : colormap = (*cinfo->mem->alloc_sarray)
299 : ((j_common_ptr) cinfo, JPOOL_IMAGE,
300 0 : (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components);
301 :
302 : /* blksize is number of adjacent repeated entries for a component */
303 : /* blkdist is distance between groups of identical entries for a component */
304 0 : blkdist = total_colors;
305 :
306 0 : for (i = 0; i < cinfo->out_color_components; i++) {
307 : /* fill in colormap entries for i'th color component */
308 0 : nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
309 0 : blksize = blkdist / nci;
310 0 : for (j = 0; j < nci; j++) {
311 : /* Compute j'th output value (out of nci) for component */
312 0 : val = output_value(cinfo, i, j, nci-1);
313 : /* Fill in all colormap entries that have this value of this component */
314 0 : for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
315 : /* fill in blksize entries beginning at ptr */
316 0 : for (k = 0; k < blksize; k++)
317 0 : colormap[i][ptr+k] = (JSAMPLE) val;
318 : }
319 : }
320 0 : blkdist = blksize; /* blksize of this color is blkdist of next */
321 : }
322 :
323 : /* Save the colormap in private storage,
324 : * where it will survive color quantization mode changes.
325 : */
326 0 : cquantize->sv_colormap = colormap;
327 0 : cquantize->sv_actual = total_colors;
328 0 : }
329 :
330 :
331 : /*
332 : * Create the color index table.
333 : */
334 :
335 : LOCAL(void)
336 0 : create_colorindex (j_decompress_ptr cinfo)
337 : {
338 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
339 : JSAMPROW indexptr;
340 : int i,j,k, nci, blksize, val, pad;
341 :
342 : /* For ordered dither, we pad the color index tables by MAXJSAMPLE in
343 : * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).
344 : * This is not necessary in the other dithering modes. However, we
345 : * flag whether it was done in case user changes dithering mode.
346 : */
347 0 : if (cinfo->dither_mode == JDITHER_ORDERED) {
348 0 : pad = MAXJSAMPLE*2;
349 0 : cquantize->is_padded = TRUE;
350 : } else {
351 0 : pad = 0;
352 0 : cquantize->is_padded = FALSE;
353 : }
354 :
355 0 : cquantize->colorindex = (*cinfo->mem->alloc_sarray)
356 : ((j_common_ptr) cinfo, JPOOL_IMAGE,
357 0 : (JDIMENSION) (MAXJSAMPLE+1 + pad),
358 0 : (JDIMENSION) cinfo->out_color_components);
359 :
360 : /* blksize is number of adjacent repeated entries for a component */
361 0 : blksize = cquantize->sv_actual;
362 :
363 0 : for (i = 0; i < cinfo->out_color_components; i++) {
364 : /* fill in colorindex entries for i'th color component */
365 0 : nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
366 0 : blksize = blksize / nci;
367 :
368 : /* adjust colorindex pointers to provide padding at negative indexes. */
369 0 : if (pad)
370 0 : cquantize->colorindex[i] += MAXJSAMPLE;
371 :
372 : /* in loop, val = index of current output value, */
373 : /* and k = largest j that maps to current val */
374 0 : indexptr = cquantize->colorindex[i];
375 0 : val = 0;
376 0 : k = largest_input_value(cinfo, i, 0, nci-1);
377 0 : for (j = 0; j <= MAXJSAMPLE; j++) {
378 0 : while (j > k) /* advance val if past boundary */
379 0 : k = largest_input_value(cinfo, i, ++val, nci-1);
380 : /* premultiply so that no multiplication needed in main processing */
381 0 : indexptr[j] = (JSAMPLE) (val * blksize);
382 : }
383 : /* Pad at both ends if necessary */
384 0 : if (pad)
385 0 : for (j = 1; j <= MAXJSAMPLE; j++) {
386 0 : indexptr[-j] = indexptr[0];
387 0 : indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];
388 : }
389 : }
390 0 : }
391 :
392 :
393 : /*
394 : * Create an ordered-dither array for a component having ncolors
395 : * distinct output values.
396 : */
397 :
398 : LOCAL(ODITHER_MATRIX_PTR)
399 0 : make_odither_array (j_decompress_ptr cinfo, int ncolors)
400 : {
401 : ODITHER_MATRIX_PTR odither;
402 : int j,k;
403 : JLONG num,den;
404 :
405 0 : odither = (ODITHER_MATRIX_PTR)
406 0 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
407 : sizeof(ODITHER_MATRIX));
408 : /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).
409 : * Hence the dither value for the matrix cell with fill order f
410 : * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).
411 : * On 16-bit-int machine, be careful to avoid overflow.
412 : */
413 0 : den = 2 * ODITHER_CELLS * ((JLONG) (ncolors - 1));
414 0 : for (j = 0; j < ODITHER_SIZE; j++) {
415 0 : for (k = 0; k < ODITHER_SIZE; k++) {
416 0 : num = ((JLONG) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))
417 0 : * MAXJSAMPLE;
418 : /* Ensure round towards zero despite C's lack of consistency
419 : * about rounding negative values in integer division...
420 : */
421 0 : odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);
422 : }
423 : }
424 0 : return odither;
425 : }
426 :
427 :
428 : /*
429 : * Create the ordered-dither tables.
430 : * Components having the same number of representative colors may
431 : * share a dither table.
432 : */
433 :
434 : LOCAL(void)
435 0 : create_odither_tables (j_decompress_ptr cinfo)
436 : {
437 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
438 : ODITHER_MATRIX_PTR odither;
439 : int i, j, nci;
440 :
441 0 : for (i = 0; i < cinfo->out_color_components; i++) {
442 0 : nci = cquantize->Ncolors[i]; /* # of distinct values for this color */
443 0 : odither = NULL; /* search for matching prior component */
444 0 : for (j = 0; j < i; j++) {
445 0 : if (nci == cquantize->Ncolors[j]) {
446 0 : odither = cquantize->odither[j];
447 0 : break;
448 : }
449 : }
450 0 : if (odither == NULL) /* need a new table? */
451 0 : odither = make_odither_array(cinfo, nci);
452 0 : cquantize->odither[i] = odither;
453 : }
454 0 : }
455 :
456 :
457 : /*
458 : * Map some rows of pixels to the output colormapped representation.
459 : */
460 :
461 : METHODDEF(void)
462 0 : color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
463 : JSAMPARRAY output_buf, int num_rows)
464 : /* General case, no dithering */
465 : {
466 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
467 0 : JSAMPARRAY colorindex = cquantize->colorindex;
468 : register int pixcode, ci;
469 : register JSAMPROW ptrin, ptrout;
470 : int row;
471 : JDIMENSION col;
472 0 : JDIMENSION width = cinfo->output_width;
473 0 : register int nc = cinfo->out_color_components;
474 :
475 0 : for (row = 0; row < num_rows; row++) {
476 0 : ptrin = input_buf[row];
477 0 : ptrout = output_buf[row];
478 0 : for (col = width; col > 0; col--) {
479 0 : pixcode = 0;
480 0 : for (ci = 0; ci < nc; ci++) {
481 0 : pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);
482 : }
483 0 : *ptrout++ = (JSAMPLE) pixcode;
484 : }
485 : }
486 0 : }
487 :
488 :
489 : METHODDEF(void)
490 0 : color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
491 : JSAMPARRAY output_buf, int num_rows)
492 : /* Fast path for out_color_components==3, no dithering */
493 : {
494 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
495 : register int pixcode;
496 : register JSAMPROW ptrin, ptrout;
497 0 : JSAMPROW colorindex0 = cquantize->colorindex[0];
498 0 : JSAMPROW colorindex1 = cquantize->colorindex[1];
499 0 : JSAMPROW colorindex2 = cquantize->colorindex[2];
500 : int row;
501 : JDIMENSION col;
502 0 : JDIMENSION width = cinfo->output_width;
503 :
504 0 : for (row = 0; row < num_rows; row++) {
505 0 : ptrin = input_buf[row];
506 0 : ptrout = output_buf[row];
507 0 : for (col = width; col > 0; col--) {
508 0 : pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);
509 0 : pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);
510 0 : pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);
511 0 : *ptrout++ = (JSAMPLE) pixcode;
512 : }
513 : }
514 0 : }
515 :
516 :
517 : METHODDEF(void)
518 0 : quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
519 : JSAMPARRAY output_buf, int num_rows)
520 : /* General case, with ordered dithering */
521 : {
522 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
523 : register JSAMPROW input_ptr;
524 : register JSAMPROW output_ptr;
525 : JSAMPROW colorindex_ci;
526 : int *dither; /* points to active row of dither matrix */
527 : int row_index, col_index; /* current indexes into dither matrix */
528 0 : int nc = cinfo->out_color_components;
529 : int ci;
530 : int row;
531 : JDIMENSION col;
532 0 : JDIMENSION width = cinfo->output_width;
533 :
534 0 : for (row = 0; row < num_rows; row++) {
535 : /* Initialize output values to 0 so can process components separately */
536 0 : jzero_far((void *) output_buf[row], (size_t) (width * sizeof(JSAMPLE)));
537 0 : row_index = cquantize->row_index;
538 0 : for (ci = 0; ci < nc; ci++) {
539 0 : input_ptr = input_buf[row] + ci;
540 0 : output_ptr = output_buf[row];
541 0 : colorindex_ci = cquantize->colorindex[ci];
542 0 : dither = cquantize->odither[ci][row_index];
543 0 : col_index = 0;
544 :
545 0 : for (col = width; col > 0; col--) {
546 : /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
547 : * select output value, accumulate into output code for this pixel.
548 : * Range-limiting need not be done explicitly, as we have extended
549 : * the colorindex table to produce the right answers for out-of-range
550 : * inputs. The maximum dither is +- MAXJSAMPLE; this sets the
551 : * required amount of padding.
552 : */
553 0 : *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];
554 0 : input_ptr += nc;
555 0 : output_ptr++;
556 0 : col_index = (col_index + 1) & ODITHER_MASK;
557 : }
558 : }
559 : /* Advance row index for next row */
560 0 : row_index = (row_index + 1) & ODITHER_MASK;
561 0 : cquantize->row_index = row_index;
562 : }
563 0 : }
564 :
565 :
566 : METHODDEF(void)
567 0 : quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
568 : JSAMPARRAY output_buf, int num_rows)
569 : /* Fast path for out_color_components==3, with ordered dithering */
570 : {
571 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
572 : register int pixcode;
573 : register JSAMPROW input_ptr;
574 : register JSAMPROW output_ptr;
575 0 : JSAMPROW colorindex0 = cquantize->colorindex[0];
576 0 : JSAMPROW colorindex1 = cquantize->colorindex[1];
577 0 : JSAMPROW colorindex2 = cquantize->colorindex[2];
578 : int *dither0; /* points to active row of dither matrix */
579 : int *dither1;
580 : int *dither2;
581 : int row_index, col_index; /* current indexes into dither matrix */
582 : int row;
583 : JDIMENSION col;
584 0 : JDIMENSION width = cinfo->output_width;
585 :
586 0 : for (row = 0; row < num_rows; row++) {
587 0 : row_index = cquantize->row_index;
588 0 : input_ptr = input_buf[row];
589 0 : output_ptr = output_buf[row];
590 0 : dither0 = cquantize->odither[0][row_index];
591 0 : dither1 = cquantize->odither[1][row_index];
592 0 : dither2 = cquantize->odither[2][row_index];
593 0 : col_index = 0;
594 :
595 0 : for (col = width; col > 0; col--) {
596 0 : pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
597 : dither0[col_index]]);
598 0 : pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
599 : dither1[col_index]]);
600 0 : pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
601 : dither2[col_index]]);
602 0 : *output_ptr++ = (JSAMPLE) pixcode;
603 0 : col_index = (col_index + 1) & ODITHER_MASK;
604 : }
605 0 : row_index = (row_index + 1) & ODITHER_MASK;
606 0 : cquantize->row_index = row_index;
607 : }
608 0 : }
609 :
610 :
611 : METHODDEF(void)
612 0 : quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
613 : JSAMPARRAY output_buf, int num_rows)
614 : /* General case, with Floyd-Steinberg dithering */
615 : {
616 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
617 : register LOCFSERROR cur; /* current error or pixel value */
618 : LOCFSERROR belowerr; /* error for pixel below cur */
619 : LOCFSERROR bpreverr; /* error for below/prev col */
620 : LOCFSERROR bnexterr; /* error for below/next col */
621 : LOCFSERROR delta;
622 : register FSERRPTR errorptr; /* => fserrors[] at column before current */
623 : register JSAMPROW input_ptr;
624 : register JSAMPROW output_ptr;
625 : JSAMPROW colorindex_ci;
626 : JSAMPROW colormap_ci;
627 : int pixcode;
628 0 : int nc = cinfo->out_color_components;
629 : int dir; /* 1 for left-to-right, -1 for right-to-left */
630 : int dirnc; /* dir * nc */
631 : int ci;
632 : int row;
633 : JDIMENSION col;
634 0 : JDIMENSION width = cinfo->output_width;
635 0 : JSAMPLE *range_limit = cinfo->sample_range_limit;
636 : SHIFT_TEMPS
637 :
638 0 : for (row = 0; row < num_rows; row++) {
639 : /* Initialize output values to 0 so can process components separately */
640 0 : jzero_far((void *) output_buf[row], (size_t) (width * sizeof(JSAMPLE)));
641 0 : for (ci = 0; ci < nc; ci++) {
642 0 : input_ptr = input_buf[row] + ci;
643 0 : output_ptr = output_buf[row];
644 0 : if (cquantize->on_odd_row) {
645 : /* work right to left in this row */
646 0 : input_ptr += (width-1) * nc; /* so point to rightmost pixel */
647 0 : output_ptr += width-1;
648 0 : dir = -1;
649 0 : dirnc = -nc;
650 0 : errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */
651 : } else {
652 : /* work left to right in this row */
653 0 : dir = 1;
654 0 : dirnc = nc;
655 0 : errorptr = cquantize->fserrors[ci]; /* => entry before first column */
656 : }
657 0 : colorindex_ci = cquantize->colorindex[ci];
658 0 : colormap_ci = cquantize->sv_colormap[ci];
659 : /* Preset error values: no error propagated to first pixel from left */
660 0 : cur = 0;
661 : /* and no error propagated to row below yet */
662 0 : belowerr = bpreverr = 0;
663 :
664 0 : for (col = width; col > 0; col--) {
665 : /* cur holds the error propagated from the previous pixel on the
666 : * current line. Add the error propagated from the previous line
667 : * to form the complete error correction term for this pixel, and
668 : * round the error term (which is expressed * 16) to an integer.
669 : * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
670 : * for either sign of the error value.
671 : * Note: errorptr points to *previous* column's array entry.
672 : */
673 0 : cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
674 : /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
675 : * The maximum error is +- MAXJSAMPLE; this sets the required size
676 : * of the range_limit array.
677 : */
678 0 : cur += GETJSAMPLE(*input_ptr);
679 0 : cur = GETJSAMPLE(range_limit[cur]);
680 : /* Select output value, accumulate into output code for this pixel */
681 0 : pixcode = GETJSAMPLE(colorindex_ci[cur]);
682 0 : *output_ptr += (JSAMPLE) pixcode;
683 : /* Compute actual representation error at this pixel */
684 : /* Note: we can do this even though we don't have the final */
685 : /* pixel code, because the colormap is orthogonal. */
686 0 : cur -= GETJSAMPLE(colormap_ci[pixcode]);
687 : /* Compute error fractions to be propagated to adjacent pixels.
688 : * Add these into the running sums, and simultaneously shift the
689 : * next-line error sums left by 1 column.
690 : */
691 0 : bnexterr = cur;
692 0 : delta = cur * 2;
693 0 : cur += delta; /* form error * 3 */
694 0 : errorptr[0] = (FSERROR) (bpreverr + cur);
695 0 : cur += delta; /* form error * 5 */
696 0 : bpreverr = belowerr + cur;
697 0 : belowerr = bnexterr;
698 0 : cur += delta; /* form error * 7 */
699 : /* At this point cur contains the 7/16 error value to be propagated
700 : * to the next pixel on the current line, and all the errors for the
701 : * next line have been shifted over. We are therefore ready to move on.
702 : */
703 0 : input_ptr += dirnc; /* advance input ptr to next column */
704 0 : output_ptr += dir; /* advance output ptr to next column */
705 0 : errorptr += dir; /* advance errorptr to current column */
706 : }
707 : /* Post-loop cleanup: we must unload the final error value into the
708 : * final fserrors[] entry. Note we need not unload belowerr because
709 : * it is for the dummy column before or after the actual array.
710 : */
711 0 : errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */
712 : }
713 0 : cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
714 : }
715 0 : }
716 :
717 :
718 : /*
719 : * Allocate workspace for Floyd-Steinberg errors.
720 : */
721 :
722 : LOCAL(void)
723 0 : alloc_fs_workspace (j_decompress_ptr cinfo)
724 : {
725 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
726 : size_t arraysize;
727 : int i;
728 :
729 0 : arraysize = (size_t) ((cinfo->output_width + 2) * sizeof(FSERROR));
730 0 : for (i = 0; i < cinfo->out_color_components; i++) {
731 0 : cquantize->fserrors[i] = (FSERRPTR)
732 0 : (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
733 : }
734 0 : }
735 :
736 :
737 : /*
738 : * Initialize for one-pass color quantization.
739 : */
740 :
741 : METHODDEF(void)
742 0 : start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
743 : {
744 0 : my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
745 : size_t arraysize;
746 : int i;
747 :
748 : /* Install my colormap. */
749 0 : cinfo->colormap = cquantize->sv_colormap;
750 0 : cinfo->actual_number_of_colors = cquantize->sv_actual;
751 :
752 : /* Initialize for desired dithering mode. */
753 0 : switch (cinfo->dither_mode) {
754 : case JDITHER_NONE:
755 0 : if (cinfo->out_color_components == 3)
756 0 : cquantize->pub.color_quantize = color_quantize3;
757 : else
758 0 : cquantize->pub.color_quantize = color_quantize;
759 0 : break;
760 : case JDITHER_ORDERED:
761 0 : if (cinfo->out_color_components == 3)
762 0 : cquantize->pub.color_quantize = quantize3_ord_dither;
763 : else
764 0 : cquantize->pub.color_quantize = quantize_ord_dither;
765 0 : cquantize->row_index = 0; /* initialize state for ordered dither */
766 : /* If user changed to ordered dither from another mode,
767 : * we must recreate the color index table with padding.
768 : * This will cost extra space, but probably isn't very likely.
769 : */
770 0 : if (! cquantize->is_padded)
771 0 : create_colorindex(cinfo);
772 : /* Create ordered-dither tables if we didn't already. */
773 0 : if (cquantize->odither[0] == NULL)
774 0 : create_odither_tables(cinfo);
775 0 : break;
776 : case JDITHER_FS:
777 0 : cquantize->pub.color_quantize = quantize_fs_dither;
778 0 : cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */
779 : /* Allocate Floyd-Steinberg workspace if didn't already. */
780 0 : if (cquantize->fserrors[0] == NULL)
781 0 : alloc_fs_workspace(cinfo);
782 : /* Initialize the propagated errors to zero. */
783 0 : arraysize = (size_t) ((cinfo->output_width + 2) * sizeof(FSERROR));
784 0 : for (i = 0; i < cinfo->out_color_components; i++)
785 0 : jzero_far((void *) cquantize->fserrors[i], arraysize);
786 0 : break;
787 : default:
788 0 : ERREXIT(cinfo, JERR_NOT_COMPILED);
789 0 : break;
790 : }
791 0 : }
792 :
793 :
794 : /*
795 : * Finish up at the end of the pass.
796 : */
797 :
798 : METHODDEF(void)
799 0 : finish_pass_1_quant (j_decompress_ptr cinfo)
800 : {
801 : /* no work in 1-pass case */
802 0 : }
803 :
804 :
805 : /*
806 : * Switch to a new external colormap between output passes.
807 : * Shouldn't get to this module!
808 : */
809 :
810 : METHODDEF(void)
811 0 : new_color_map_1_quant (j_decompress_ptr cinfo)
812 : {
813 0 : ERREXIT(cinfo, JERR_MODE_CHANGE);
814 0 : }
815 :
816 :
817 : /*
818 : * Module initialization routine for 1-pass color quantization.
819 : */
820 :
821 : GLOBAL(void)
822 0 : jinit_1pass_quantizer (j_decompress_ptr cinfo)
823 : {
824 : my_cquantize_ptr cquantize;
825 :
826 0 : cquantize = (my_cquantize_ptr)
827 0 : (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
828 : sizeof(my_cquantizer));
829 0 : cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
830 0 : cquantize->pub.start_pass = start_pass_1_quant;
831 0 : cquantize->pub.finish_pass = finish_pass_1_quant;
832 0 : cquantize->pub.new_color_map = new_color_map_1_quant;
833 0 : cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */
834 0 : cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */
835 :
836 : /* Make sure my internal arrays won't overflow */
837 0 : if (cinfo->out_color_components > MAX_Q_COMPS)
838 0 : ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
839 : /* Make sure colormap indexes can be represented by JSAMPLEs */
840 0 : if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
841 0 : ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
842 :
843 : /* Create the colormap and color index table. */
844 0 : create_colormap(cinfo);
845 0 : create_colorindex(cinfo);
846 :
847 : /* Allocate Floyd-Steinberg workspace now if requested.
848 : * We do this now since it may affect the memory manager's space
849 : * calculations. If the user changes to FS dither mode in a later pass, we
850 : * will allocate the space then, and will possibly overrun the
851 : * max_memory_to_use setting.
852 : */
853 0 : if (cinfo->dither_mode == JDITHER_FS)
854 0 : alloc_fs_workspace(cinfo);
855 0 : }
856 :
857 : #endif /* QUANT_1PASS_SUPPORTED */
|
