source: trunk/libjpeg/jccolor.c @ 89

Last change on this file since 89 was 15, checked in by Eugene Romanenko, 16 years ago

needed libs update

File size: 14.9 KB
Line 
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
18typedef 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
25typedef 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
85METHODDEF(void)
86rgb_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
129METHODDEF(void)
130rgb_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      inptr += RGB_PIXELSIZE;
153      /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
154       * must be too; we do not need an explicit range-limiting operation.
155       * Hence the value being shifted is never negative, and we don't
156       * need the general RIGHT_SHIFT macro.
157       */
158      /* Y */
159      outptr0[col] = (JSAMPLE)
160                ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
161                 >> SCALEBITS);
162      /* Cb */
163      outptr1[col] = (JSAMPLE)
164                ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
165                 >> SCALEBITS);
166      /* Cr */
167      outptr2[col] = (JSAMPLE)
168                ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
169                 >> SCALEBITS);
170    }
171  }
172}
173
174
175/**************** Cases other than RGB -> YCbCr **************/
176
177
178/*
179 * Convert some rows of samples to the JPEG colorspace.
180 * This version handles RGB->grayscale conversion, which is the same
181 * as the RGB->Y portion of RGB->YCbCr.
182 * We assume rgb_ycc_start has been called (we only use the Y tables).
183 */
184
185METHODDEF(void)
186rgb_gray_convert (j_compress_ptr cinfo,
187                  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
188                  JDIMENSION output_row, int num_rows)
189{
190  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
191  register int r, g, b;
192  register INT32 * ctab = cconvert->rgb_ycc_tab;
193  register JSAMPROW inptr;
194  register JSAMPROW outptr;
195  register JDIMENSION col;
196  JDIMENSION num_cols = cinfo->image_width;
197
198  while (--num_rows >= 0) {
199    inptr = *input_buf++;
200    outptr = output_buf[0][output_row];
201    output_row++;
202    for (col = 0; col < num_cols; col++) {
203      r = GETJSAMPLE(inptr[RGB_RED]);
204      g = GETJSAMPLE(inptr[RGB_GREEN]);
205      b = GETJSAMPLE(inptr[RGB_BLUE]);
206      inptr += RGB_PIXELSIZE;
207      /* Y */
208      outptr[col] = (JSAMPLE)
209                ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
210                 >> SCALEBITS);
211    }
212  }
213}
214
215
216/*
217 * Convert some rows of samples to the JPEG colorspace.
218 * This version handles Adobe-style CMYK->YCCK conversion,
219 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
220 * conversion as above, while passing K (black) unchanged.
221 * We assume rgb_ycc_start has been called.
222 */
223
224METHODDEF(void)
225cmyk_ycck_convert (j_compress_ptr cinfo,
226                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
227                   JDIMENSION output_row, int num_rows)
228{
229  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
230  register int r, g, b;
231  register INT32 * ctab = cconvert->rgb_ycc_tab;
232  register JSAMPROW inptr;
233  register JSAMPROW outptr0, outptr1, outptr2, outptr3;
234  register JDIMENSION col;
235  JDIMENSION num_cols = cinfo->image_width;
236
237  while (--num_rows >= 0) {
238    inptr = *input_buf++;
239    outptr0 = output_buf[0][output_row];
240    outptr1 = output_buf[1][output_row];
241    outptr2 = output_buf[2][output_row];
242    outptr3 = output_buf[3][output_row];
243    output_row++;
244    for (col = 0; col < num_cols; col++) {
245      r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
246      g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
247      b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
248      /* K passes through as-is */
249      outptr3[col] = inptr[3];  /* don't need GETJSAMPLE here */
250      inptr += 4;
251      /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
252       * must be too; we do not need an explicit range-limiting operation.
253       * Hence the value being shifted is never negative, and we don't
254       * need the general RIGHT_SHIFT macro.
255       */
256      /* Y */
257      outptr0[col] = (JSAMPLE)
258                ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
259                 >> SCALEBITS);
260      /* Cb */
261      outptr1[col] = (JSAMPLE)
262                ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
263                 >> SCALEBITS);
264      /* Cr */
265      outptr2[col] = (JSAMPLE)
266                ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
267                 >> SCALEBITS);
268    }
269  }
270}
271
272
273/*
274 * Convert some rows of samples to the JPEG colorspace.
275 * This version handles grayscale output with no conversion.
276 * The source can be either plain grayscale or YCbCr (since Y == gray).
277 */
278
279METHODDEF(void)
280grayscale_convert (j_compress_ptr cinfo,
281                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
282                   JDIMENSION output_row, int num_rows)
283{
284  register JSAMPROW inptr;
285  register JSAMPROW outptr;
286  register JDIMENSION col;
287  JDIMENSION num_cols = cinfo->image_width;
288  int instride = cinfo->input_components;
289
290  while (--num_rows >= 0) {
291    inptr = *input_buf++;
292    outptr = output_buf[0][output_row];
293    output_row++;
294    for (col = 0; col < num_cols; col++) {
295      outptr[col] = inptr[0];   /* don't need GETJSAMPLE() here */
296      inptr += instride;
297    }
298  }
299}
300
301
302/*
303 * Convert some rows of samples to the JPEG colorspace.
304 * This version handles multi-component colorspaces without conversion.
305 * We assume input_components == num_components.
306 */
307
308METHODDEF(void)
309null_convert (j_compress_ptr cinfo,
310              JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
311              JDIMENSION output_row, int num_rows)
312{
313  register JSAMPROW inptr;
314  register JSAMPROW outptr;
315  register JDIMENSION col;
316  register int ci;
317  int nc = cinfo->num_components;
318  JDIMENSION num_cols = cinfo->image_width;
319
320  while (--num_rows >= 0) {
321    /* It seems fastest to make a separate pass for each component. */
322    for (ci = 0; ci < nc; ci++) {
323      inptr = *input_buf;
324      outptr = output_buf[ci][output_row];
325      for (col = 0; col < num_cols; col++) {
326        outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
327        inptr += nc;
328      }
329    }
330    input_buf++;
331    output_row++;
332  }
333}
334
335
336/*
337 * Empty method for start_pass.
338 */
339
340METHODDEF(void)
341null_method (j_compress_ptr cinfo)
342{
343  /* no work needed */
344}
345
346
347/*
348 * Module initialization routine for input colorspace conversion.
349 */
350
351GLOBAL(void)
352jinit_color_converter (j_compress_ptr cinfo)
353{
354  my_cconvert_ptr cconvert;
355
356  cconvert = (my_cconvert_ptr)
357    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
358                                SIZEOF(my_color_converter));
359  cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
360  /* set start_pass to null method until we find out differently */
361  cconvert->pub.start_pass = null_method;
362
363  /* Make sure input_components agrees with in_color_space */
364  switch (cinfo->in_color_space) {
365  case JCS_GRAYSCALE:
366    if (cinfo->input_components != 1)
367      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
368    break;
369
370  case JCS_RGB:
371#if RGB_PIXELSIZE != 3
372    if (cinfo->input_components != RGB_PIXELSIZE)
373      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
374    break;
375#endif /* else share code with YCbCr */
376
377  case JCS_YCbCr:
378    if (cinfo->input_components != 3)
379      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
380    break;
381
382  case JCS_CMYK:
383  case JCS_YCCK:
384    if (cinfo->input_components != 4)
385      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
386    break;
387
388  default:                      /* JCS_UNKNOWN can be anything */
389    if (cinfo->input_components < 1)
390      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
391    break;
392  }
393
394  /* Check num_components, set conversion method based on requested space */
395  switch (cinfo->jpeg_color_space) {
396  case JCS_GRAYSCALE:
397    if (cinfo->num_components != 1)
398      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
399    if (cinfo->in_color_space == JCS_GRAYSCALE)
400      cconvert->pub.color_convert = grayscale_convert;
401    else if (cinfo->in_color_space == JCS_RGB) {
402      cconvert->pub.start_pass = rgb_ycc_start;
403      cconvert->pub.color_convert = rgb_gray_convert;
404    } else if (cinfo->in_color_space == JCS_YCbCr)
405      cconvert->pub.color_convert = grayscale_convert;
406    else
407      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
408    break;
409
410  case JCS_RGB:
411    if (cinfo->num_components != 3)
412      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
413    if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
414      cconvert->pub.color_convert = null_convert;
415    else
416      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
417    break;
418
419  case JCS_YCbCr:
420    if (cinfo->num_components != 3)
421      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
422    if (cinfo->in_color_space == JCS_RGB) {
423      cconvert->pub.start_pass = rgb_ycc_start;
424      cconvert->pub.color_convert = rgb_ycc_convert;
425    } else if (cinfo->in_color_space == JCS_YCbCr)
426      cconvert->pub.color_convert = null_convert;
427    else
428      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
429    break;
430
431  case JCS_CMYK:
432    if (cinfo->num_components != 4)
433      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
434    if (cinfo->in_color_space == JCS_CMYK)
435      cconvert->pub.color_convert = null_convert;
436    else
437      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
438    break;
439
440  case JCS_YCCK:
441    if (cinfo->num_components != 4)
442      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
443    if (cinfo->in_color_space == JCS_CMYK) {
444      cconvert->pub.start_pass = rgb_ycc_start;
445      cconvert->pub.color_convert = cmyk_ycck_convert;
446    } else if (cinfo->in_color_space == JCS_YCCK)
447      cconvert->pub.color_convert = null_convert;
448    else
449      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
450    break;
451
452  default:                      /* allow null conversion of JCS_UNKNOWN */
453    if (cinfo->jpeg_color_space != cinfo->in_color_space ||
454        cinfo->num_components != cinfo->input_components)
455      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
456    cconvert->pub.color_convert = null_convert;
457    break;
458  }
459}
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