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1 /*
2 * jdcolor.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains output colorspace conversion routines.
9 */
10
11 #define JPEG_INTERNALS
12 #include "jinclude.h"
13 #include "jpeglib.h"
14
15 #if defined(__VISAGECPP__)
16 /* Visual Age fixups for multiple declarations */
17 # define null_convert null_convert2 /* already in jcmaint.c */
18 # define grayscale_convert grayscale_convert2 /* already in jcmaint.c */
19 #endif
20
21 /* Private subobject */
22
23 typedef struct {
24 struct jpeg_color_deconverter pub; /* public fields */
25
26 /* Private state for YCC->RGB conversion */
27 int * Cr_r_tab; /* => table for Cr to R conversion */
28 int * Cb_b_tab; /* => table for Cb to B conversion */
29 JPEG_INT32 * Cr_g_tab; /* => table for Cr to G conversion */
30 JPEG_INT32 * Cb_g_tab; /* => table for Cb to G conversion */
31 } my_color_deconverter;
32
33 typedef my_color_deconverter * my_cconvert_ptr;
34
35
36 /**************** YCbCr -> RGB conversion: most 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 * R = Y + 1.40200 * Cr
43 * G = Y - 0.34414 * Cb - 0.71414 * Cr
44 * B = Y + 1.77200 * Cb
45 * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
46 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
47 *
48 * To avoid floating-point arithmetic, we represent the fractional constants
49 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
50 * the products by 2^16, with appropriate rounding, to get the correct answer.
51 * Notice that Y, being an integral input, does not contribute any fraction
52 * so it need not participate in the rounding.
53 *
54 * For even more speed, we avoid doing any multiplications in the inner loop
55 * by precalculating the constants times Cb and Cr for all possible values.
56 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
57 * for 12-bit samples it is still acceptable. It's not very reasonable for
58 * 16-bit samples, but if you want lossless storage you shouldn't be changing
59 * colorspace anyway.
60 * The Cr=>R and Cb=>B values can be rounded to integers in advance; the
61 * values for the G calculation are left scaled up, since we must add them
62 * together before rounding.
63 */
64
65 #define SCALEBITS 16 /* speediest right-shift on some machines */
66 #define ONE_HALF ((JPEG_INT32) 1 << (SCALEBITS-1))
67 #define FIX(x) ((JPEG_INT32) ((x) * (1L<<SCALEBITS) + 0.5))
68
69
70 /*
71 * Initialize tables for YCC->RGB colorspace conversion.
72 */
73
74 LOCAL(void)
75 build_ycc_rgb_table (j_decompress_ptr cinfo)
76 {
77 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
78 int i;
79 JPEG_INT32 x;
80 SHIFT_TEMPS
81
82 cconvert->Cr_r_tab = (int *)
83 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
84 (MAXJSAMPLE+1) * SIZEOF(int));
85 cconvert->Cb_b_tab = (int *)
86 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
87 (MAXJSAMPLE+1) * SIZEOF(int));
88 cconvert->Cr_g_tab = (JPEG_INT32 *)
89 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
90 (MAXJSAMPLE+1) * SIZEOF(JPEG_INT32));
91 cconvert->Cb_g_tab = (JPEG_INT32 *)
92 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
93 (MAXJSAMPLE+1) * SIZEOF(JPEG_INT32));
94
95 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
96 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
97 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
98 /* Cr=>R value is nearest int to 1.40200 * x */
99 cconvert->Cr_r_tab[i] = (int)
100 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
101 /* Cb=>B value is nearest int to 1.77200 * x */
102 cconvert->Cb_b_tab[i] = (int)
103 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
104 /* Cr=>G value is scaled-up -0.71414 * x */
105 cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
106 /* Cb=>G value is scaled-up -0.34414 * x */
107 /* We also add in ONE_HALF so that need not do it in inner loop */
108 cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
109 }
110 }
111
112
113 /*
114 * Convert some rows of samples to the output colorspace.
115 *
116 * Note that we change from noninterleaved, one-plane-per-component format
117 * to interleaved-pixel format. The output buffer is therefore three times
118 * as wide as the input buffer.
119 * A starting row offset is provided only for the input buffer. The caller
120 * can easily adjust the passed output_buf value to accommodate any row
121 * offset required on that side.
122 */
123
124 METHODDEF(void)
125 ycc_rgb_convert (j_decompress_ptr cinfo,
126 JSAMPIMAGE input_buf, JDIMENSION input_row,
127 JSAMPARRAY output_buf, int num_rows)
128 {
129 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
130 register int y, cb, cr;
131 register JSAMPROW outptr;
132 register JSAMPROW inptr0, inptr1, inptr2;
133 register JDIMENSION col;
134 JDIMENSION num_cols = cinfo->output_width;
135 /* copy these pointers into registers if possible */
136 register JSAMPLE * range_limit = cinfo->sample_range_limit;
137 register int * Crrtab = cconvert->Cr_r_tab;
138 register int * Cbbtab = cconvert->Cb_b_tab;
139 register JPEG_INT32 * Crgtab = cconvert->Cr_g_tab;
140 register JPEG_INT32 * Cbgtab = cconvert->Cb_g_tab;
141 SHIFT_TEMPS
142
143 while (--num_rows >= 0) {
144 inptr0 = input_buf[0][input_row];
145 inptr1 = input_buf[1][input_row];
146 inptr2 = input_buf[2][input_row];
147 input_row++;
148 outptr = *output_buf++;
149 for (col = 0; col < num_cols; col++) {
150 y = GETJSAMPLE(inptr0[col]);
151 cb = GETJSAMPLE(inptr1[col]);
152 cr = GETJSAMPLE(inptr2[col]);
153 /* Range-limiting is essential due to noise introduced by DCT losses. */
154 outptr[RGB_RED] = range_limit[y + Crrtab[cr]];
155 outptr[RGB_GREEN] = range_limit[y +
156 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
157 SCALEBITS))];
158 outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]];
159 outptr += RGB_PIXELSIZE;
160 }
161 }
162 }
163
164
165 /**************** Cases other than YCbCr -> RGB **************/
166
167
168 /*
169 * Color conversion for no colorspace change: just copy the data,
170 * converting from separate-planes to interleaved representation.
171 */
172
173 METHODDEF(void)
174 null_convert (j_decompress_ptr cinfo,
175 JSAMPIMAGE input_buf, JDIMENSION input_row,
176 JSAMPARRAY output_buf, int num_rows)
177 {
178 register JSAMPROW inptr, outptr;
179 register JDIMENSION count;
180 register int num_components = cinfo->num_components;
181 JDIMENSION num_cols = cinfo->output_width;
182 int ci;
183
184 while (--num_rows >= 0) {
185 for (ci = 0; ci < num_components; ci++) {
186 inptr = input_buf[ci][input_row];
187 outptr = output_buf[0] + ci;
188 for (count = num_cols; count > 0; count--) {
189 *outptr = *inptr++; /* needn't bother with GETJSAMPLE() here */
190 outptr += num_components;
191 }
192 }
193 input_row++;
194 output_buf++;
195 }
196 }
197
198
199 /*
200 * Color conversion for grayscale: just copy the data.
201 * This also works for YCbCr -> grayscale conversion, in which
202 * we just copy the Y (luminance) component and ignore chrominance.
203 */
204
205 METHODDEF(void)
206 grayscale_convert (j_decompress_ptr cinfo,
207 JSAMPIMAGE input_buf, JDIMENSION input_row,
208 JSAMPARRAY output_buf, int num_rows)
209 {
210 jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
211 num_rows, cinfo->output_width);
212 }
213
214
215 /*
216 * Convert grayscale to RGB: just duplicate the graylevel three times.
217 * This is provided to support applications that don't want to cope
218 * with grayscale as a separate case.
219 */
220
221 METHODDEF(void)
222 gray_rgb_convert (j_decompress_ptr cinfo,
223 JSAMPIMAGE input_buf, JDIMENSION input_row,
224 JSAMPARRAY output_buf, int num_rows)
225 {
226 register JSAMPROW inptr, outptr;
227 register JDIMENSION col;
228 JDIMENSION num_cols = cinfo->output_width;
229
230 while (--num_rows >= 0) {
231 inptr = input_buf[0][input_row++];
232 outptr = *output_buf++;
233 for (col = 0; col < num_cols; col++) {
234 /* We can dispense with GETJSAMPLE() here */
235 outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];
236 outptr += RGB_PIXELSIZE;
237 }
238 }
239 }
240
241
242 /*
243 * Adobe-style YCCK->CMYK conversion.
244 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
245 * conversion as above, while passing K (black) unchanged.
246 * We assume build_ycc_rgb_table has been called.
247 */
248
249 METHODDEF(void)
250 ycck_cmyk_convert (j_decompress_ptr cinfo,
251 JSAMPIMAGE input_buf, JDIMENSION input_row,
252 JSAMPARRAY output_buf, int num_rows)
253 {
254 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
255 register int y, cb, cr;
256 register JSAMPROW outptr;
257 register JSAMPROW inptr0, inptr1, inptr2, inptr3;
258 register JDIMENSION col;
259 JDIMENSION num_cols = cinfo->output_width;
260 /* copy these pointers into registers if possible */
261 register JSAMPLE * range_limit = cinfo->sample_range_limit;
262 register int * Crrtab = cconvert->Cr_r_tab;
263 register int * Cbbtab = cconvert->Cb_b_tab;
264 register JPEG_INT32 * Crgtab = cconvert->Cr_g_tab;
265 register JPEG_INT32 * Cbgtab = cconvert->Cb_g_tab;
266 SHIFT_TEMPS
267
268 while (--num_rows >= 0) {
269 inptr0 = input_buf[0][input_row];
270 inptr1 = input_buf[1][input_row];
271 inptr2 = input_buf[2][input_row];
272 inptr3 = input_buf[3][input_row];
273 input_row++;
274 outptr = *output_buf++;
275 for (col = 0; col < num_cols; col++) {
276 y = GETJSAMPLE(inptr0[col]);
277 cb = GETJSAMPLE(inptr1[col]);
278 cr = GETJSAMPLE(inptr2[col]);
279 /* Range-limiting is essential due to noise introduced by DCT losses. */
280 outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */
281 outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */
282 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
283 SCALEBITS)))];
284 outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */
285 /* K passes through unchanged */
286 outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */
287 outptr += 4;
288 }
289 }
290 }
291
292
293 /*
294 * Empty method for start_pass.
295 */
296
297 METHODDEF(void)
298 start_pass_dcolor (j_decompress_ptr cinfo)
299 {
300 /* no work needed */
301 }
302
303
304 /*
305 * Module initialization routine for output colorspace conversion.
306 */
307
308 GLOBAL(void)
309 jinit_color_deconverter (j_decompress_ptr cinfo)
310 {
311 my_cconvert_ptr cconvert;
312 int ci;
313
314 cconvert = (my_cconvert_ptr)
315 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
316 SIZEOF(my_color_deconverter));
317 cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
318 cconvert->pub.start_pass = start_pass_dcolor;
319
320 /* Make sure num_components agrees with jpeg_color_space */
321 switch (cinfo->jpeg_color_space) {
322 case JCS_GRAYSCALE:
323 if (cinfo->num_components != 1)
324 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
325 break;
326
327 case JCS_RGB:
328 case JCS_YCbCr:
329 if (cinfo->num_components != 3)
330 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
331 break;
332
333 case JCS_CMYK:
334 case JCS_YCCK:
335 if (cinfo->num_components != 4)
336 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
337 break;
338
339 default: /* JCS_UNKNOWN can be anything */
340 if (cinfo->num_components < 1)
341 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
342 break;
343 }
344
345 /* Set out_color_components and conversion method based on requested space.
346 * Also clear the component_needed flags for any unused components,
347 * so that earlier pipeline stages can avoid useless computation.
348 */
349
350 switch (cinfo->out_color_space) {
351 case JCS_GRAYSCALE:
352 cinfo->out_color_components = 1;
353 if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
354 cinfo->jpeg_color_space == JCS_YCbCr) {
355 cconvert->pub.color_convert = grayscale_convert;
356 /* For color->grayscale conversion, only the Y (0) component is needed */
357 for (ci = 1; ci < cinfo->num_components; ci++)
358 cinfo->comp_info[ci].component_needed = FALSE;
359 } else
360 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
361 break;
362
363 case JCS_RGB:
364 cinfo->out_color_components = RGB_PIXELSIZE;
365 if (cinfo->jpeg_color_space == JCS_YCbCr) {
366 cconvert->pub.color_convert = ycc_rgb_convert;
367 build_ycc_rgb_table(cinfo);
368 } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
369 cconvert->pub.color_convert = gray_rgb_convert;
370 } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
371 cconvert->pub.color_convert = null_convert;
372 } else
373 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
374 break;
375
376 case JCS_CMYK:
377 cinfo->out_color_components = 4;
378 if (cinfo->jpeg_color_space == JCS_YCCK) {
379 cconvert->pub.color_convert = ycck_cmyk_convert;
380 build_ycc_rgb_table(cinfo);
381 } else if (cinfo->jpeg_color_space == JCS_CMYK) {
382 cconvert->pub.color_convert = null_convert;
383 } else
384 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
385 break;
386
387 default:
388 /* Permit null conversion to same output space */
389 if (cinfo->out_color_space == cinfo->jpeg_color_space) {
390 cinfo->out_color_components = cinfo->num_components;
391 cconvert->pub.color_convert = null_convert;
392 } else /* unsupported non-null conversion */
393 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
394 break;
395 }
396
397 if (cinfo->quantize_colors)
398 cinfo->output_components = 1; /* single colormapped output component */
399 else
400 cinfo->output_components = cinfo->out_color_components;
401 }
402
403 #if defined(__VISAGECPP__)
404 # ifdef null_convert2
405 # undef null_convert2
406 # endif
407 # ifdef grayscale_convert2
408 # undef grayscale_convert2
409 # endif
410 #endif