1 /*
2 * jccolor.c
3 *
4 * Copyright (C) 1991-1996, 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 input colorspace conversion routines.
9 */
10
11 #define JPEG_INTERNALS
12 #include "jinclude.h"
13 #include "jpeglib.h"
14
15
16 /* Private subobject */
17
18 typedef struct {
19 struct jpeg_color_converter pub; /* public fields */
20
21 /* Private state for RGB->YCC conversion */
22 INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */
23 } my_color_converter;
24
25 typedef my_color_converter * my_cconvert_ptr;
26
27
28 /**************** RGB -> YCbCr conversion: most common case **************/
29
30 /*
31 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
32 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
33 * The conversion equations to be implemented are therefore
34 * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B
35 * Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE
36 * Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE
37 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
38 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
39 * rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and
40 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
41 * were not represented exactly. Now we sacrifice exact representation of
42 * maximum red and maximum blue in order to get exact grayscales.
43 *
44 * To avoid floating-point arithmetic, we represent the fractional constants
45 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
46 * the products by 2^16, with appropriate rounding, to get the correct answer.
47 *
48 * For even more speed, we avoid doing any multiplications in the inner loop
49 * by precalculating the constants times R,G,B for all possible values.
50 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
51 * for 12-bit samples it is still acceptable. It's not very reasonable for
52 * 16-bit samples, but if you want lossless storage you shouldn't be changing
53 * colorspace anyway.
54 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
55 * in the tables to save adding them separately in the inner loop.
56 */
57
58 #define SCALEBITS 16 /* speediest right-shift on some machines */
59 #define CBCR_OFFSET ((INT32) CENTERJSAMPLE << SCALEBITS)
60 #define ONE_HALF ((INT32) 1 << (SCALEBITS-1))
61 #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
62
63 /* We allocate one big table and divide it up into eight parts, instead of
64 * doing eight alloc_small requests. This lets us use a single table base
65 * address, which can be held in a register in the inner loops on many
66 * machines (more than can hold all eight addresses, anyway).
67 */
68
69 #define R_Y_OFF 0 /* offset to R => Y section */
70 #define G_Y_OFF (1*(MAXJSAMPLE+1)) /* offset to G => Y section */
71 #define B_Y_OFF (2*(MAXJSAMPLE+1)) /* etc. */
72 #define R_CB_OFF (3*(MAXJSAMPLE+1))
73 #define G_CB_OFF (4*(MAXJSAMPLE+1))
74 #define B_CB_OFF (5*(MAXJSAMPLE+1))
75 #define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */
76 #define G_CR_OFF (6*(MAXJSAMPLE+1))
77 #define B_CR_OFF (7*(MAXJSAMPLE+1))
78 #define TABLE_SIZE (8*(MAXJSAMPLE+1))
79
80
81 /*
82 * Initialize for RGB->YCC colorspace conversion.
83 */
84
85 METHODDEF(void)
rgb_ycc_start(j_compress_ptr cinfo)86 rgb_ycc_start (j_compress_ptr cinfo)
87 {
88 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
89 INT32 * rgb_ycc_tab;
90 INT32 i;
91
92 /* Allocate and fill in the conversion tables. */
93 cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)
94 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
95 (TABLE_SIZE * SIZEOF(INT32)));
96
97 for (i = 0; i <= MAXJSAMPLE; i++) {
98 rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
99 rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
100 rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF;
101 rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
102 rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
103 /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
104 * This ensures that the maximum output will round to MAXJSAMPLE
105 * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
106 */
107 rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1;
108 /* B=>Cb and R=>Cr tables are the same
109 rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1;
110 */
111 rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
112 rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
113 }
114 }
115
116
117 /*
118 * Convert some rows of samples to the JPEG colorspace.
119 *
120 * Note that we change from the application's interleaved-pixel format
121 * to our internal noninterleaved, one-plane-per-component format.
122 * The input buffer is therefore three times as wide as the output buffer.
123 *
124 * A starting row offset is provided only for the output buffer. The caller
125 * can easily adjust the passed input_buf value to accommodate any row
126 * offset required on that side.
127 */
128
129 METHODDEF(void)
rgb_ycc_convert(j_compress_ptr cinfo,JSAMPARRAY input_buf,JSAMPIMAGE output_buf,JDIMENSION output_row,int num_rows)130 rgb_ycc_convert (j_compress_ptr cinfo,
131 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
132 JDIMENSION output_row, int num_rows)
133 {
134 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
135 register int r, g, b;
136 register INT32 * ctab = cconvert->rgb_ycc_tab;
137 register JSAMPROW inptr;
138 register JSAMPROW outptr0, outptr1, outptr2;
139 register JDIMENSION col;
140 JDIMENSION num_cols = cinfo->image_width;
141
142 while (--num_rows >= 0) {
143 inptr = *input_buf++;
144 outptr0 = output_buf[0][output_row];
145 outptr1 = output_buf[1][output_row];
146 outptr2 = output_buf[2][output_row];
147 output_row++;
148 for (col = 0; col < num_cols; col++) {
149 r = GETJSAMPLE(inptr[RGB_RED]);
150 g = GETJSAMPLE(inptr[RGB_GREEN]);
151 b = GETJSAMPLE(inptr[RGB_BLUE]);
152
153 /* KEVINJ: HACK!!!!!!!!! You are supposed to change RGB_PIXELSIZE, but I don't want to change this globally in case it breaks other stuff */
154 if (cinfo->hack_use_input_components_as_RGB_PIXELSIZE)
155 inptr +=cinfo->input_components;
156 else
157 inptr += RGB_PIXELSIZE;
158
159 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
160 * must be too; we do not need an explicit range-limiting operation.
161 * Hence the value being shifted is never negative, and we don't
162 * need the general RIGHT_SHIFT macro.
163 */
164 /* Y */
165 outptr0[col] = (JSAMPLE)
166 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
167 >> SCALEBITS);
168 /* Cb */
169 outptr1[col] = (JSAMPLE)
170 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
171 >> SCALEBITS);
172 /* Cr */
173 outptr2[col] = (JSAMPLE)
174 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
175 >> SCALEBITS);
176 }
177 }
178 }
179
180
181 /**************** Cases other than RGB -> YCbCr **************/
182
183
184 /*
185 * Convert some rows of samples to the JPEG colorspace.
186 * This version handles RGB->grayscale conversion, which is the same
187 * as the RGB->Y portion of RGB->YCbCr.
188 * We assume rgb_ycc_start has been called (we only use the Y tables).
189 */
190
191 METHODDEF(void)
rgb_gray_convert(j_compress_ptr cinfo,JSAMPARRAY input_buf,JSAMPIMAGE output_buf,JDIMENSION output_row,int num_rows)192 rgb_gray_convert (j_compress_ptr cinfo,
193 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
194 JDIMENSION output_row, int num_rows)
195 {
196 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
197 register int r, g, b;
198 register INT32 * ctab = cconvert->rgb_ycc_tab;
199 register JSAMPROW inptr;
200 register JSAMPROW outptr;
201 register JDIMENSION col;
202 JDIMENSION num_cols = cinfo->image_width;
203
204 while (--num_rows >= 0) {
205 inptr = *input_buf++;
206 outptr = output_buf[0][output_row];
207 output_row++;
208 for (col = 0; col < num_cols; col++) {
209 r = GETJSAMPLE(inptr[RGB_RED]);
210 g = GETJSAMPLE(inptr[RGB_GREEN]);
211 b = GETJSAMPLE(inptr[RGB_BLUE]);
212 inptr += RGB_PIXELSIZE;
213 /* Y */
214 outptr[col] = (JSAMPLE)
215 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
216 >> SCALEBITS);
217 }
218 }
219 }
220
221
222 /*
223 * Convert some rows of samples to the JPEG colorspace.
224 * This version handles Adobe-style CMYK->YCCK conversion,
225 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
226 * conversion as above, while passing K (black) unchanged.
227 * We assume rgb_ycc_start has been called.
228 */
229
230 METHODDEF(void)
cmyk_ycck_convert(j_compress_ptr cinfo,JSAMPARRAY input_buf,JSAMPIMAGE output_buf,JDIMENSION output_row,int num_rows)231 cmyk_ycck_convert (j_compress_ptr cinfo,
232 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
233 JDIMENSION output_row, int num_rows)
234 {
235 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
236 register int r, g, b;
237 register INT32 * ctab = cconvert->rgb_ycc_tab;
238 register JSAMPROW inptr;
239 register JSAMPROW outptr0, outptr1, outptr2, outptr3;
240 register JDIMENSION col;
241 JDIMENSION num_cols = cinfo->image_width;
242
243 while (--num_rows >= 0) {
244 inptr = *input_buf++;
245 outptr0 = output_buf[0][output_row];
246 outptr1 = output_buf[1][output_row];
247 outptr2 = output_buf[2][output_row];
248 outptr3 = output_buf[3][output_row];
249 output_row++;
250 for (col = 0; col < num_cols; col++) {
251 r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
252 g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
253 b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
254 /* K passes through as-is */
255 outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */
256 inptr += 4;
257 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
258 * must be too; we do not need an explicit range-limiting operation.
259 * Hence the value being shifted is never negative, and we don't
260 * need the general RIGHT_SHIFT macro.
261 */
262 /* Y */
263 outptr0[col] = (JSAMPLE)
264 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
265 >> SCALEBITS);
266 /* Cb */
267 outptr1[col] = (JSAMPLE)
268 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
269 >> SCALEBITS);
270 /* Cr */
271 outptr2[col] = (JSAMPLE)
272 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
273 >> SCALEBITS);
274 }
275 }
276 }
277
278
279 /*
280 * Convert some rows of samples to the JPEG colorspace.
281 * This version handles grayscale output with no conversion.
282 * The source can be either plain grayscale or YCbCr (since Y == gray).
283 */
284
285 METHODDEF(void)
grayscale_convert(j_compress_ptr cinfo,JSAMPARRAY input_buf,JSAMPIMAGE output_buf,JDIMENSION output_row,int num_rows)286 grayscale_convert (j_compress_ptr cinfo,
287 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
288 JDIMENSION output_row, int num_rows)
289 {
290 register JSAMPROW inptr;
291 register JSAMPROW outptr;
292 register JDIMENSION col;
293 JDIMENSION num_cols = cinfo->image_width;
294 int instride = cinfo->input_components;
295
296 while (--num_rows >= 0) {
297 inptr = *input_buf++;
298 outptr = output_buf[0][output_row];
299 output_row++;
300 for (col = 0; col < num_cols; col++) {
301 outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */
302 inptr += instride;
303 }
304 }
305 }
306
307
308 /*
309 * Convert some rows of samples to the JPEG colorspace.
310 * This version handles multi-component colorspaces without conversion.
311 * We assume input_components == num_components.
312 */
313
314 METHODDEF(void)
null_convert(j_compress_ptr cinfo,JSAMPARRAY input_buf,JSAMPIMAGE output_buf,JDIMENSION output_row,int num_rows)315 null_convert (j_compress_ptr cinfo,
316 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
317 JDIMENSION output_row, int num_rows)
318 {
319 register JSAMPROW inptr;
320 register JSAMPROW outptr;
321 register JDIMENSION col;
322 register int ci;
323 int nc = cinfo->num_components;
324 JDIMENSION num_cols = cinfo->image_width;
325
326 while (--num_rows >= 0) {
327 /* It seems fastest to make a separate pass for each component. */
328 for (ci = 0; ci < nc; ci++) {
329 inptr = *input_buf;
330 outptr = output_buf[ci][output_row];
331 for (col = 0; col < num_cols; col++) {
332 outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
333 inptr += nc;
334 }
335 }
336 input_buf++;
337 output_row++;
338 }
339 }
340
341
342 /*
343 * Empty method for start_pass.
344 */
345
346 METHODDEF(void)
null_method(j_compress_ptr cinfo)347 null_method (j_compress_ptr cinfo)
348 {
349 /* no work needed */
350 }
351
352
353 /*
354 * Module initialization routine for input colorspace conversion.
355 */
356
357 GLOBAL(void)
jinit_color_converter(j_compress_ptr cinfo)358 jinit_color_converter (j_compress_ptr cinfo)
359 {
360 my_cconvert_ptr cconvert;
361
362 cconvert = (my_cconvert_ptr)
363 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
364 SIZEOF(my_color_converter));
365 cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
366 /* set start_pass to null method until we find out differently */
367 cconvert->pub.start_pass = null_method;
368
369 /* Make sure input_components agrees with in_color_space */
370 switch (cinfo->in_color_space) {
371 case JCS_GRAYSCALE:
372 if (cinfo->input_components != 1)
373 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
374 break;
375
376 case JCS_RGB:
377 #if RGB_PIXELSIZE != 3
378 if (cinfo->input_components != RGB_PIXELSIZE)
379 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
380 break;
381 #endif /* else share code with YCbCr */
382
383 case JCS_YCbCr:
384 if (cinfo->input_components != 3)
385 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
386 break;
387
388 case JCS_CMYK:
389 case JCS_YCCK:
390 if (cinfo->input_components != 4)
391 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
392 break;
393
394 default: /* JCS_UNKNOWN can be anything */
395 if (cinfo->input_components < 1)
396 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
397 break;
398 }
399
400 /* Check num_components, set conversion method based on requested space */
401 switch (cinfo->jpeg_color_space) {
402 case JCS_GRAYSCALE:
403 if (cinfo->num_components != 1)
404 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
405 if (cinfo->in_color_space == JCS_GRAYSCALE)
406 cconvert->pub.color_convert = grayscale_convert;
407 else if (cinfo->in_color_space == JCS_RGB) {
408 cconvert->pub.start_pass = rgb_ycc_start;
409 cconvert->pub.color_convert = rgb_gray_convert;
410 } else if (cinfo->in_color_space == JCS_YCbCr)
411 cconvert->pub.color_convert = grayscale_convert;
412 else
413 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
414 break;
415
416 case JCS_RGB:
417 if (cinfo->num_components != 3)
418 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
419 if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
420 cconvert->pub.color_convert = null_convert;
421 else
422 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
423 break;
424
425 case JCS_YCbCr:
426 if (cinfo->num_components != 3)
427 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
428 if (cinfo->in_color_space == JCS_RGB) {
429 cconvert->pub.start_pass = rgb_ycc_start;
430 cconvert->pub.color_convert = rgb_ycc_convert;
431 } else if (cinfo->in_color_space == JCS_YCbCr)
432 cconvert->pub.color_convert = null_convert;
433 else
434 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
435 break;
436
437 case JCS_CMYK:
438 if (cinfo->num_components != 4)
439 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
440 if (cinfo->in_color_space == JCS_CMYK)
441 cconvert->pub.color_convert = null_convert;
442 else
443 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
444 break;
445
446 case JCS_YCCK:
447 if (cinfo->num_components != 4)
448 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
449 if (cinfo->in_color_space == JCS_CMYK) {
450 cconvert->pub.start_pass = rgb_ycc_start;
451 cconvert->pub.color_convert = cmyk_ycck_convert;
452 } else if (cinfo->in_color_space == JCS_YCCK)
453 cconvert->pub.color_convert = null_convert;
454 else
455 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
456 break;
457
458 default: /* allow null conversion of JCS_UNKNOWN */
459 if (cinfo->jpeg_color_space != cinfo->in_color_space ||
460 cinfo->num_components != cinfo->input_components)
461 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
462 cconvert->pub.color_convert = null_convert;
463 break;
464 }
465 }
466