1/*
2 * jdcolor.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * Modified 2011-2012 by Guido Vollbeding.
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 output colorspace conversion routines.
10 */
11
12#define JPEG_INTERNALS
13#include "jinclude.h"
14#include "jpeglib.h"
15
16
17/* Private subobject */
18
19typedef struct {
20 struct jpeg_color_deconverter pub; /* public fields */
21
22 /* Private state for YCC->RGB conversion */
23 int * Cr_r_tab; /* => table for Cr to R conversion */
24 int * Cb_b_tab; /* => table for Cb to B conversion */
25 INT32 * Cr_g_tab; /* => table for Cr to G conversion */
26 INT32 * Cb_g_tab; /* => table for Cb to G conversion */
27
28 /* Private state for RGB->Y conversion */
29 INT32 * rgb_y_tab; /* => table for RGB to Y conversion */
30} my_color_deconverter;
31
32typedef my_color_deconverter * my_cconvert_ptr;
33
34
35/**************** YCbCr -> RGB conversion: most common case **************/
36/**************** RGB -> Y conversion: less common case **************/
37
38/*
39 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
40 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
41 * The conversion equations to be implemented are therefore
42 *
43 * R = Y + 1.40200 * Cr
44 * G = Y - 0.34414 * Cb - 0.71414 * Cr
45 * B = Y + 1.77200 * Cb
46 *
47 * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
48 *
49 * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
50 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
51 *
52 * To avoid floating-point arithmetic, we represent the fractional constants
53 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
54 * the products by 2^16, with appropriate rounding, to get the correct answer.
55 * Notice that Y, being an integral input, does not contribute any fraction
56 * so it need not participate in the rounding.
57 *
58 * For even more speed, we avoid doing any multiplications in the inner loop
59 * by precalculating the constants times Cb and Cr for all possible values.
60 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
61 * for 12-bit samples it is still acceptable. It's not very reasonable for
62 * 16-bit samples, but if you want lossless storage you shouldn't be changing
63 * colorspace anyway.
64 * The Cr=>R and Cb=>B values can be rounded to integers in advance; the
65 * values for the G calculation are left scaled up, since we must add them
66 * together before rounding.
67 */
68
69#define SCALEBITS 16 /* speediest right-shift on some machines */
70#define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
71#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
72
73/* We allocate one big table for RGB->Y conversion and divide it up into
74 * three parts, instead of doing three alloc_small requests. This lets us
75 * use a single table base address, which can be held in a register in the
76 * inner loops on many machines (more than can hold all three addresses,
77 * anyway).
78 */
79
80#define R_Y_OFF 0 /* offset to R => Y section */
81#define G_Y_OFF (1*(MAXJSAMPLE+1)) /* offset to G => Y section */
82#define B_Y_OFF (2*(MAXJSAMPLE+1)) /* etc. */
83#define TABLE_SIZE (3*(MAXJSAMPLE+1))
84
85
86/*
87 * Initialize tables for YCC->RGB colorspace conversion.
88 */
89
90LOCAL(void)
91build_ycc_rgb_table (j_decompress_ptr cinfo)
92{
93 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
94 int i;
95 INT32 x;
96 SHIFT_TEMPS
97
98 cconvert->Cr_r_tab = (int *)
99 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
100 (MAXJSAMPLE+1) * SIZEOF(int));
101 cconvert->Cb_b_tab = (int *)
102 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
103 (MAXJSAMPLE+1) * SIZEOF(int));
104 cconvert->Cr_g_tab = (INT32 *)
105 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
106 (MAXJSAMPLE+1) * SIZEOF(INT32));
107 cconvert->Cb_g_tab = (INT32 *)
108 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
109 (MAXJSAMPLE+1) * SIZEOF(INT32));
110
111 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
112 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
113 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
114 /* Cr=>R value is nearest int to 1.40200 * x */
115 cconvert->Cr_r_tab[i] = (int)
116 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
117 /* Cb=>B value is nearest int to 1.77200 * x */
118 cconvert->Cb_b_tab[i] = (int)
119 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
120 /* Cr=>G value is scaled-up -0.71414 * x */
121 cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
122 /* Cb=>G value is scaled-up -0.34414 * x */
123 /* We also add in ONE_HALF so that need not do it in inner loop */
124 cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
125 }
126}
127
128
129/*
130 * Convert some rows of samples to the output colorspace.
131 *
132 * Note that we change from noninterleaved, one-plane-per-component format
133 * to interleaved-pixel format. The output buffer is therefore three times
134 * as wide as the input buffer.
135 * A starting row offset is provided only for the input buffer. The caller
136 * can easily adjust the passed output_buf value to accommodate any row
137 * offset required on that side.
138 */
139
140METHODDEF(void)
141ycc_rgb_convert (j_decompress_ptr cinfo,
142 JSAMPIMAGE input_buf, JDIMENSION input_row,
143 JSAMPARRAY output_buf, int num_rows)
144{
145 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
146 register int y, cb, cr;
147 register JSAMPROW outptr;
148 register JSAMPROW inptr0, inptr1, inptr2;
149 register JDIMENSION col;
150 JDIMENSION num_cols = cinfo->output_width;
151 /* copy these pointers into registers if possible */
152 register JSAMPLE * range_limit = cinfo->sample_range_limit;
153 register int * Crrtab = cconvert->Cr_r_tab;
154 register int * Cbbtab = cconvert->Cb_b_tab;
155 register INT32 * Crgtab = cconvert->Cr_g_tab;
156 register INT32 * Cbgtab = cconvert->Cb_g_tab;
157 SHIFT_TEMPS
158
159 while (--num_rows >= 0) {
160 inptr0 = input_buf[0][input_row];
161 inptr1 = input_buf[1][input_row];
162 inptr2 = input_buf[2][input_row];
163 input_row++;
164 outptr = *output_buf++;
165 for (col = 0; col < num_cols; col++) {
166 y = GETJSAMPLE(inptr0[col]);
167 cb = GETJSAMPLE(inptr1[col]);
168 cr = GETJSAMPLE(inptr2[col]);
169 /* Range-limiting is essential due to noise introduced by DCT losses. */
170 outptr[RGB_RED] = range_limit[y + Crrtab[cr]];
171 outptr[RGB_GREEN] = range_limit[y +
172 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
173 SCALEBITS))];
174 outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]];
175 outptr += RGB_PIXELSIZE;
176 }
177 }
178}
179
180
181/**************** Cases other than YCbCr -> RGB **************/
182
183
184/*
185 * Initialize for RGB->grayscale colorspace conversion.
186 */
187
188LOCAL(void)
189build_rgb_y_table (j_decompress_ptr cinfo)
190{
191 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
192 INT32 * rgb_y_tab;
193 INT32 i;
194
195 /* Allocate and fill in the conversion tables. */
196 cconvert->rgb_y_tab = rgb_y_tab = (INT32 *)
197 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
198 (TABLE_SIZE * SIZEOF(INT32)));
199
200 for (i = 0; i <= MAXJSAMPLE; i++) {
201 rgb_y_tab[i+R_Y_OFF] = FIX(0.29900) * i;
202 rgb_y_tab[i+G_Y_OFF] = FIX(0.58700) * i;
203 rgb_y_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF;
204 }
205}
206
207
208/*
209 * Convert RGB to grayscale.
210 */
211
212METHODDEF(void)
213rgb_gray_convert (j_decompress_ptr cinfo,
214 JSAMPIMAGE input_buf, JDIMENSION input_row,
215 JSAMPARRAY output_buf, int num_rows)
216{
217 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
218 register INT32 * ctab = cconvert->rgb_y_tab;
219 register int r, g, b;
220 register JSAMPROW outptr;
221 register JSAMPROW inptr0, inptr1, inptr2;
222 register JDIMENSION col;
223 JDIMENSION num_cols = cinfo->output_width;
224
225 while (--num_rows >= 0) {
226 inptr0 = input_buf[0][input_row];
227 inptr1 = input_buf[1][input_row];
228 inptr2 = input_buf[2][input_row];
229 input_row++;
230 outptr = *output_buf++;
231 for (col = 0; col < num_cols; col++) {
232 r = GETJSAMPLE(inptr0[col]);
233 g = GETJSAMPLE(inptr1[col]);
234 b = GETJSAMPLE(inptr2[col]);
235 /* Y */
236 outptr[col] = (JSAMPLE)
237 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
238 >> SCALEBITS);
239 }
240 }
241}
242
243
244/*
245 * [R-G,G,B-G] to [R,G,B] conversion with modulo calculation
246 * (inverse color transform).
247 */
248
249METHODDEF(void)
250rgb1_rgb_convert (j_decompress_ptr cinfo,
251 JSAMPIMAGE input_buf, JDIMENSION input_row,
252 JSAMPARRAY output_buf, int num_rows)
253{
254 register int r, g, b;
255 register JSAMPROW outptr;
256 register JSAMPROW inptr0, inptr1, inptr2;
257 register JDIMENSION col;
258 JDIMENSION num_cols = cinfo->output_width;
259
260 while (--num_rows >= 0) {
261 inptr0 = input_buf[0][input_row];
262 inptr1 = input_buf[1][input_row];
263 inptr2 = input_buf[2][input_row];
264 input_row++;
265 outptr = *output_buf++;
266 for (col = 0; col < num_cols; col++) {
267 r = GETJSAMPLE(inptr0[col]);
268 g = GETJSAMPLE(inptr1[col]);
269 b = GETJSAMPLE(inptr2[col]);
270 /* Assume that MAXJSAMPLE+1 is a power of 2, so that the MOD
271 * (modulo) operator is equivalent to the bitmask operator AND.
272 */
273 outptr[RGB_RED] = (JSAMPLE) ((r + g - CENTERJSAMPLE) & MAXJSAMPLE);
274 outptr[RGB_GREEN] = (JSAMPLE) g;
275 outptr[RGB_BLUE] = (JSAMPLE) ((b + g - CENTERJSAMPLE) & MAXJSAMPLE);
276 outptr += RGB_PIXELSIZE;
277 }
278 }
279}
280
281
282/*
283 * [R-G,G,B-G] to grayscale conversion with modulo calculation
284 * (inverse color transform).
285 */
286
287METHODDEF(void)
288rgb1_gray_convert (j_decompress_ptr cinfo,
289 JSAMPIMAGE input_buf, JDIMENSION input_row,
290 JSAMPARRAY output_buf, int num_rows)
291{
292 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
293 register INT32 * ctab = cconvert->rgb_y_tab;
294 register int r, g, b;
295 register JSAMPROW outptr;
296 register JSAMPROW inptr0, inptr1, inptr2;
297 register JDIMENSION col;
298 JDIMENSION num_cols = cinfo->output_width;
299
300 while (--num_rows >= 0) {
301 inptr0 = input_buf[0][input_row];
302 inptr1 = input_buf[1][input_row];
303 inptr2 = input_buf[2][input_row];
304 input_row++;
305 outptr = *output_buf++;
306 for (col = 0; col < num_cols; col++) {
307 r = GETJSAMPLE(inptr0[col]);
308 g = GETJSAMPLE(inptr1[col]);
309 b = GETJSAMPLE(inptr2[col]);
310 /* Assume that MAXJSAMPLE+1 is a power of 2, so that the MOD
311 * (modulo) operator is equivalent to the bitmask operator AND.
312 */
313 r = (r + g - CENTERJSAMPLE) & MAXJSAMPLE;
314 b = (b + g - CENTERJSAMPLE) & MAXJSAMPLE;
315 /* Y */
316 outptr[col] = (JSAMPLE)
317 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
318 >> SCALEBITS);
319 }
320 }
321}
322
323
324/*
325 * No colorspace change, but conversion from separate-planes
326 * to interleaved representation.
327 */
328
329METHODDEF(void)
330rgb_convert (j_decompress_ptr cinfo,
331 JSAMPIMAGE input_buf, JDIMENSION input_row,
332 JSAMPARRAY output_buf, int num_rows)
333{
334 register JSAMPROW outptr;
335 register JSAMPROW inptr0, inptr1, inptr2;
336 register JDIMENSION col;
337 JDIMENSION num_cols = cinfo->output_width;
338
339 while (--num_rows >= 0) {
340 inptr0 = input_buf[0][input_row];
341 inptr1 = input_buf[1][input_row];
342 inptr2 = input_buf[2][input_row];
343 input_row++;
344 outptr = *output_buf++;
345 for (col = 0; col < num_cols; col++) {
346 /* We can dispense with GETJSAMPLE() here */
347 outptr[RGB_RED] = inptr0[col];
348 outptr[RGB_GREEN] = inptr1[col];
349 outptr[RGB_BLUE] = inptr2[col];
350 outptr += RGB_PIXELSIZE;
351 }
352 }
353}
354
355
356/*
357 * Color conversion for no colorspace change: just copy the data,
358 * converting from separate-planes to interleaved representation.
359 */
360
361METHODDEF(void)
362null_convert (j_decompress_ptr cinfo,
363 JSAMPIMAGE input_buf, JDIMENSION input_row,
364 JSAMPARRAY output_buf, int num_rows)
365{
366 int ci;
367 register int nc = cinfo->num_components;
368 register JSAMPROW outptr;
369 register JSAMPROW inptr;
370 register JDIMENSION col;
371 JDIMENSION num_cols = cinfo->output_width;
372
373 while (--num_rows >= 0) {
374 for (ci = 0; ci < nc; ci++) {
375 inptr = input_buf[ci][input_row];
376 outptr = output_buf[0] + ci;
377 for (col = 0; col < num_cols; col++) {
378 *outptr = *inptr++; /* needn't bother with GETJSAMPLE() here */
379 outptr += nc;
380 }
381 }
382 input_row++;
383 output_buf++;
384 }
385}
386
387
388/*
389 * Color conversion for grayscale: just copy the data.
390 * This also works for YCbCr -> grayscale conversion, in which
391 * we just copy the Y (luminance) component and ignore chrominance.
392 */
393
394METHODDEF(void)
395grayscale_convert (j_decompress_ptr cinfo,
396 JSAMPIMAGE input_buf, JDIMENSION input_row,
397 JSAMPARRAY output_buf, int num_rows)
398{
399 jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
400 num_rows, cinfo->output_width);
401}
402
403
404/*
405 * Convert grayscale to RGB: just duplicate the graylevel three times.
406 * This is provided to support applications that don't want to cope
407 * with grayscale as a separate case.
408 */
409
410METHODDEF(void)
411gray_rgb_convert (j_decompress_ptr cinfo,
412 JSAMPIMAGE input_buf, JDIMENSION input_row,
413 JSAMPARRAY output_buf, int num_rows)
414{
415 register JSAMPROW outptr;
416 register JSAMPROW inptr;
417 register JDIMENSION col;
418 JDIMENSION num_cols = cinfo->output_width;
419
420 while (--num_rows >= 0) {
421 inptr = input_buf[0][input_row++];
422 outptr = *output_buf++;
423 for (col = 0; col < num_cols; col++) {
424 /* We can dispense with GETJSAMPLE() here */
425 outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];
426 outptr += RGB_PIXELSIZE;
427 }
428 }
429}
430
431
432/*
433 * Adobe-style YCCK->CMYK conversion.
434 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
435 * conversion as above, while passing K (black) unchanged.
436 * We assume build_ycc_rgb_table has been called.
437 */
438
439METHODDEF(void)
440ycck_cmyk_convert (j_decompress_ptr cinfo,
441 JSAMPIMAGE input_buf, JDIMENSION input_row,
442 JSAMPARRAY output_buf, int num_rows)
443{
444 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
445 register int y, cb, cr;
446 register JSAMPROW outptr;
447 register JSAMPROW inptr0, inptr1, inptr2, inptr3;
448 register JDIMENSION col;
449 JDIMENSION num_cols = cinfo->output_width;
450 /* copy these pointers into registers if possible */
451 register JSAMPLE * range_limit = cinfo->sample_range_limit;
452 register int * Crrtab = cconvert->Cr_r_tab;
453 register int * Cbbtab = cconvert->Cb_b_tab;
454 register INT32 * Crgtab = cconvert->Cr_g_tab;
455 register INT32 * Cbgtab = cconvert->Cb_g_tab;
456 SHIFT_TEMPS
457
458 while (--num_rows >= 0) {
459 inptr0 = input_buf[0][input_row];
460 inptr1 = input_buf[1][input_row];
461 inptr2 = input_buf[2][input_row];
462 inptr3 = input_buf[3][input_row];
463 input_row++;
464 outptr = *output_buf++;
465 for (col = 0; col < num_cols; col++) {
466 y = GETJSAMPLE(inptr0[col]);
467 cb = GETJSAMPLE(inptr1[col]);
468 cr = GETJSAMPLE(inptr2[col]);
469 /* Range-limiting is essential due to noise introduced by DCT losses. */
470 outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */
471 outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */
472 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
473 SCALEBITS)))];
474 outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */
475 /* K passes through unchanged */
476 outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */
477 outptr += 4;
478 }
479 }
480}
481
482
483/*
484 * Empty method for start_pass.
485 */
486
487METHODDEF(void)
488start_pass_dcolor (j_decompress_ptr cinfo)
489{
490 /* no work needed */
491}
492
493
494/*
495 * Module initialization routine for output colorspace conversion.
496 */
497
498GLOBAL(void)
499jinit_color_deconverter (j_decompress_ptr cinfo)
500{
501 my_cconvert_ptr cconvert;
502 int ci;
503
504 cconvert = (my_cconvert_ptr)
505 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
506 SIZEOF(my_color_deconverter));
507 cinfo->cconvert = &cconvert->pub;
508 cconvert->pub.start_pass = start_pass_dcolor;
509
510 /* Make sure num_components agrees with jpeg_color_space */
511 switch (cinfo->jpeg_color_space) {
512 case JCS_GRAYSCALE:
513 if (cinfo->num_components != 1)
514 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
515 break;
516
517 case JCS_RGB:
518 case JCS_YCbCr:
519 if (cinfo->num_components != 3)
520 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
521 break;
522
523 case JCS_CMYK:
524 case JCS_YCCK:
525 if (cinfo->num_components != 4)
526 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
527 break;
528
529 default: /* JCS_UNKNOWN can be anything */
530 if (cinfo->num_components < 1)
531 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
532 break;
533 }
534
535 /* Support color transform only for RGB colorspace */
536 if (cinfo->color_transform && cinfo->jpeg_color_space != JCS_RGB)
537 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
538
539 /* Set out_color_components and conversion method based on requested space.
540 * Also clear the component_needed flags for any unused components,
541 * so that earlier pipeline stages can avoid useless computation.
542 */
543
544 switch (cinfo->out_color_space) {
545 case JCS_GRAYSCALE:
546 cinfo->out_color_components = 1;
547 if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
548 cinfo->jpeg_color_space == JCS_YCbCr) {
549 cconvert->pub.color_convert = grayscale_convert;
550 /* For color->grayscale conversion, only the Y (0) component is needed */
551 for (ci = 1; ci < cinfo->num_components; ci++)
552 cinfo->comp_info[ci].component_needed = FALSE;
553 } else if (cinfo->jpeg_color_space == JCS_RGB) {
554 switch (cinfo->color_transform) {
555 case JCT_NONE:
556 cconvert->pub.color_convert = rgb_gray_convert;
557 break;
558 case JCT_SUBTRACT_GREEN:
559 cconvert->pub.color_convert = rgb1_gray_convert;
560 break;
561 default:
562 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
563 break;
564 }
565 build_rgb_y_table(cinfo);
566 } else
567 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
568 break;
569
570 case JCS_RGB:
571 cinfo->out_color_components = RGB_PIXELSIZE;
572 if (cinfo->jpeg_color_space == JCS_YCbCr) {
573 cconvert->pub.color_convert = ycc_rgb_convert;
574 build_ycc_rgb_table(cinfo);
575 } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
576 cconvert->pub.color_convert = gray_rgb_convert;
577 } else if (cinfo->jpeg_color_space == JCS_RGB) {
578 switch (cinfo->color_transform) {
579 case JCT_NONE:
580 cconvert->pub.color_convert = rgb_convert;
581 break;
582 case JCT_SUBTRACT_GREEN:
583 cconvert->pub.color_convert = rgb1_rgb_convert;
584 break;
585 default:
586 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
587 break;
588 }
589 } else
590 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
591 break;
592
593 case JCS_CMYK:
594 cinfo->out_color_components = 4;
595 if (cinfo->jpeg_color_space == JCS_YCCK) {
596 cconvert->pub.color_convert = ycck_cmyk_convert;
597 build_ycc_rgb_table(cinfo);
598 } else if (cinfo->jpeg_color_space == JCS_CMYK) {
599 cconvert->pub.color_convert = null_convert;
600 } else
601 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
602 break;
603
604 default:
605 /* Permit null conversion to same output space */
606 if (cinfo->out_color_space == cinfo->jpeg_color_space) {
607 cinfo->out_color_components = cinfo->num_components;
608 cconvert->pub.color_convert = null_convert;
609 } else /* unsupported non-null conversion */
610 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
611 break;
612 }
613
614 if (cinfo->quantize_colors)
615 cinfo->output_components = 1; /* single colormapped output component */
616 else
617 cinfo->output_components = cinfo->out_color_components;
618}
619