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