1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * jdcolor.c
7 *
8 * Copyright (C) 1991-1997, Thomas G. Lane.
9 * This file is part of the Independent JPEG Group's software.
10 * For conditions of distribution and use, see the accompanying README file.
11 *
12 * This file contains output colorspace conversion routines.
13 */
14
15#define JPEG_INTERNALS
16#include "jinclude.h"
17#include "jpeglib.h"
18
19
20/* Private subobject */
21
22typedef struct {
23 struct jpeg_color_deconverter pub; /* public fields */
24
25 /* Private state for YCC->RGB conversion */
26 int * Cr_r_tab; /* => table for Cr to R conversion */
27 int * Cb_b_tab; /* => table for Cb to B conversion */
28 INT32 * Cr_g_tab; /* => table for Cr to G conversion */
29 INT32 * Cb_g_tab; /* => table for Cb to G conversion */
30} my_color_deconverter;
31
32typedef my_color_deconverter * my_cconvert_ptr;
33
34
35/**************** YCbCr -> RGB conversion: most common case **************/
36
37/*
38 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
39 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
40 * The conversion equations to be implemented are therefore
41 * R = Y + 1.40200 * Cr
42 * G = Y - 0.34414 * Cb - 0.71414 * Cr
43 * B = Y + 1.77200 * Cb
44 * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
45 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
46 *
47 * To avoid floating-point arithmetic, we represent the fractional constants
48 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
49 * the products by 2^16, with appropriate rounding, to get the correct answer.
50 * Notice that Y, being an integral input, does not contribute any fraction
51 * so it need not participate in the rounding.
52 *
53 * For even more speed, we avoid doing any multiplications in the inner loop
54 * by precalculating the constants times Cb and Cr for all possible values.
55 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
56 * for 12-bit samples it is still acceptable. It's not very reasonable for
57 * 16-bit samples, but if you want lossless storage you shouldn't be changing
58 * colorspace anyway.
59 * The Cr=>R and Cb=>B values can be rounded to integers in advance; the
60 * values for the G calculation are left scaled up, since we must add them
61 * together before rounding.
62 */
63
64#define SCALEBITS 16 /* speediest right-shift on some machines */
65#define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
66#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
67
68
69/*
70 * Initialize tables for YCC->RGB colorspace conversion.
71 */
72
73LOCAL(void)
74build_ycc_rgb_table (j_decompress_ptr cinfo)
75{
76 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
77 int i;
78 INT32 x;
79 SHIFT_TEMPS
80
81 cconvert->Cr_r_tab = (int *)
82 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
83 (MAXJSAMPLE+1) * SIZEOF(int));
84 cconvert->Cb_b_tab = (int *)
85 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
86 (MAXJSAMPLE+1) * SIZEOF(int));
87 cconvert->Cr_g_tab = (INT32 *)
88 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
89 (MAXJSAMPLE+1) * SIZEOF(INT32));
90 cconvert->Cb_g_tab = (INT32 *)
91 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
92 (MAXJSAMPLE+1) * SIZEOF(INT32));
93
94 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
95 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
96 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
97 /* Cr=>R value is nearest int to 1.40200 * x */
98 cconvert->Cr_r_tab[i] = (int)
99 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
100 /* Cb=>B value is nearest int to 1.77200 * x */
101 cconvert->Cb_b_tab[i] = (int)
102 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
103 /* Cr=>G value is scaled-up -0.71414 * x */
104 cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
105 /* Cb=>G value is scaled-up -0.34414 * x */
106 /* We also add in ONE_HALF so that need not do it in inner loop */
107 cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
108 }
109}
110
111
112/*
113 * Convert some rows of samples to the output colorspace.
114 *
115 * Note that we change from noninterleaved, one-plane-per-component format
116 * to interleaved-pixel format. The output buffer is therefore three times
117 * as wide as the input buffer.
118 * A starting row offset is provided only for the input buffer. The caller
119 * can easily adjust the passed output_buf value to accommodate any row
120 * offset required on that side.
121 */
122
123METHODDEF(void)
124ycc_rgb_convert (j_decompress_ptr cinfo,
125 JSAMPIMAGE input_buf, JDIMENSION input_row,
126 JSAMPARRAY output_buf, int num_rows)
127{
128 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
129 register int y, cb, cr;
130 register JSAMPROW outptr;
131 register JSAMPROW inptr0, inptr1, inptr2;
132 register JDIMENSION col;
133 JDIMENSION num_cols = cinfo->output_width;
134 /* copy these pointers into registers if possible */
135 register JSAMPLE * range_limit = cinfo->sample_range_limit;
136 register int * Crrtab = cconvert->Cr_r_tab;
137 register int * Cbbtab = cconvert->Cb_b_tab;
138 register INT32 * Crgtab = cconvert->Cr_g_tab;
139 register INT32 * Cbgtab = cconvert->Cb_g_tab;
140 SHIFT_TEMPS
141
142 while (--num_rows >= 0) {
143 inptr0 = input_buf[0][input_row];
144 inptr1 = input_buf[1][input_row];
145 inptr2 = input_buf[2][input_row];
146 input_row++;
147 outptr = *output_buf++;
148 for (col = 0; col < num_cols; col++) {
149 y = GETJSAMPLE(inptr0[col]);
150 cb = GETJSAMPLE(inptr1[col]);
151 cr = GETJSAMPLE(inptr2[col]);
152 /* Range-limiting is essential due to noise introduced by DCT losses. */
153 outptr[RGB_RED] = range_limit[y + Crrtab[cr]];
154 outptr[RGB_GREEN] = range_limit[y +
155 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
156 SCALEBITS))];
157 outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]];
158 outptr += RGB_PIXELSIZE;
159 }
160 }
161}
162
163
164/**************** Cases other than YCbCr -> RGB **************/
165
166
167/*
168 * Color conversion for no colorspace change: just copy the data,
169 * converting from separate-planes to interleaved representation.
170 */
171
172METHODDEF(void)
173null_convert (j_decompress_ptr cinfo,
174 JSAMPIMAGE input_buf, JDIMENSION input_row,
175 JSAMPARRAY output_buf, int num_rows)
176{
177 register JSAMPROW inptr, outptr;
178 register JDIMENSION count;
179 register int num_components = cinfo->num_components;
180 JDIMENSION num_cols = cinfo->output_width;
181 int ci;
182
183 while (--num_rows >= 0) {
184 for (ci = 0; ci < num_components; ci++) {
185 inptr = input_buf[ci][input_row];
186 outptr = output_buf[0] + ci;
187 for (count = num_cols; count > 0; count--) {
188 *outptr = *inptr++; /* needn't bother with GETJSAMPLE() here */
189 outptr += num_components;
190 }
191 }
192 input_row++;
193 output_buf++;
194 }
195}
196
197
198/*
199 * Color conversion for grayscale: just copy the data.
200 * This also works for YCbCr -> grayscale conversion, in which
201 * we just copy the Y (luminance) component and ignore chrominance.
202 */
203
204METHODDEF(void)
205grayscale_convert (j_decompress_ptr cinfo,
206 JSAMPIMAGE input_buf, JDIMENSION input_row,
207 JSAMPARRAY output_buf, int num_rows)
208{
209 jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
210 num_rows, cinfo->output_width);
211}
212
213/*
214 * Convert grayscale to RGB: just duplicate the graylevel three times.
215 * This is provided to support applications that don't want to cope
216 * with grayscale as a separate case.
217 */
218
219METHODDEF(void)
220gray_rgb_convert (j_decompress_ptr cinfo,
221 JSAMPIMAGE input_buf, JDIMENSION input_row,
222 JSAMPARRAY output_buf, int num_rows)
223{
224 register JSAMPROW inptr, outptr;
225 register JDIMENSION col;
226 JDIMENSION num_cols = cinfo->output_width;
227
228 while (--num_rows >= 0) {
229 inptr = input_buf[0][input_row++];
230 outptr = *output_buf++;
231 for (col = 0; col < num_cols; col++) {
232 /* We can dispense with GETJSAMPLE() here */
233 outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];
234 outptr += RGB_PIXELSIZE;
235 }
236 }
237}
238
239
240/*
241 * Adobe-style YCCK->CMYK conversion.
242 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
243 * conversion as above, while passing K (black) unchanged.
244 * We assume build_ycc_rgb_table has been called.
245 */
246
247METHODDEF(void)
248ycck_cmyk_convert (j_decompress_ptr cinfo,
249 JSAMPIMAGE input_buf, JDIMENSION input_row,
250 JSAMPARRAY output_buf, int num_rows)
251{
252 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
253 register int y, cb, cr;
254 register JSAMPROW outptr;
255 register JSAMPROW inptr0, inptr1, inptr2, inptr3;
256 register JDIMENSION col;
257 JDIMENSION num_cols = cinfo->output_width;
258 /* copy these pointers into registers if possible */
259 register JSAMPLE * range_limit = cinfo->sample_range_limit;
260 register int * Crrtab = cconvert->Cr_r_tab;
261 register int * Cbbtab = cconvert->Cb_b_tab;
262 register INT32 * Crgtab = cconvert->Cr_g_tab;
263 register INT32 * Cbgtab = cconvert->Cb_g_tab;
264 SHIFT_TEMPS
265
266 while (--num_rows >= 0) {
267 inptr0 = input_buf[0][input_row];
268 inptr1 = input_buf[1][input_row];
269 inptr2 = input_buf[2][input_row];
270 inptr3 = input_buf[3][input_row];
271 input_row++;
272 outptr = *output_buf++;
273 for (col = 0; col < num_cols; col++) {
274 y = GETJSAMPLE(inptr0[col]);
275 cb = GETJSAMPLE(inptr1[col]);
276 cr = GETJSAMPLE(inptr2[col]);
277 /* Range-limiting is essential due to noise introduced by DCT losses. */
278 outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */
279 outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */
280 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
281 SCALEBITS)))];
282 outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */
283 /* K passes through unchanged */
284 outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */
285 outptr += 4;
286 }
287 }
288}
289
290
291/*
292 * Empty method for start_pass.
293 */
294
295METHODDEF(void)
296start_pass_dcolor (j_decompress_ptr cinfo)
297{
298 /* no work needed */
299}
300
301
302/*
303 * Module initialization routine for output colorspace conversion.
304 */
305
306GLOBAL(void)
307jinit_color_deconverter (j_decompress_ptr cinfo)
308{
309 my_cconvert_ptr cconvert;
310 int ci;
311
312 cconvert = (my_cconvert_ptr)
313 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
314 SIZEOF(my_color_deconverter));
315 cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
316 cconvert->pub.start_pass = start_pass_dcolor;
317
318 /* Make sure num_components agrees with jpeg_color_space */
319 switch (cinfo->jpeg_color_space) {
320 case JCS_GRAYSCALE:
321 if (cinfo->num_components != 1)
322 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
323 break;
324 case JCS_RGB:
325 case JCS_YCbCr:
326 if (cinfo->num_components != 3)
327 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
328 break;
329
330 case JCS_CMYK:
331 case JCS_YCCK:
332 if (cinfo->num_components != 4)
333 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
334 break;
335
336 default: /* JCS_UNKNOWN can be anything */
337 if (cinfo->num_components < 1)
338 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
339 break;
340 }
341
342 /* Set out_color_components and conversion method based on requested space.
343 * Also clear the component_needed flags for any unused components,
344 * so that earlier pipeline stages can avoid useless computation.
345 */
346
347 switch (cinfo->out_color_space) {
348 case JCS_GRAYSCALE:
349 cinfo->out_color_components = 1;
350 if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
351 cinfo->jpeg_color_space == JCS_YCbCr) {
352 cconvert->pub.color_convert = grayscale_convert;
353 /* For color->grayscale conversion, only the Y (0) component is needed */
354 for (ci = 1; ci < cinfo->num_components; ci++)
355 cinfo->comp_info[ci].component_needed = FALSE;
356 } else
357 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
358 break;
359
360 case JCS_RGB:
361 cinfo->out_color_components = RGB_PIXELSIZE;
362 if (cinfo->jpeg_color_space == JCS_YCbCr) {
363 cconvert->pub.color_convert = ycc_rgb_convert;
364 build_ycc_rgb_table(cinfo);
365 } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
366 cconvert->pub.color_convert = gray_rgb_convert;
367 } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
368 cconvert->pub.color_convert = null_convert;
369 } else
370 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
371 break;
372
373 case JCS_CMYK:
374 cinfo->out_color_components = 4;
375 if (cinfo->jpeg_color_space == JCS_YCCK) {
376 cconvert->pub.color_convert = ycck_cmyk_convert;
377 build_ycc_rgb_table(cinfo);
378 } else if (cinfo->jpeg_color_space == JCS_CMYK) {
379 cconvert->pub.color_convert = null_convert;
380 } else
381 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
382 break;
383
384 default:
385 /* Permit null conversion to same output space */
386 if (cinfo->out_color_space == cinfo->jpeg_color_space) {
387 cinfo->out_color_components = cinfo->num_components;
388 cconvert->pub.color_convert = null_convert;
389 } else /* unsupported non-null conversion */
390 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
391 break;
392 }
393
394 if (cinfo->quantize_colors)
395 cinfo->output_components = 1; /* single colormapped output component */
396 else
397 cinfo->output_components = cinfo->out_color_components;
398}
399