source: trunk/libjpeg/jdcolor.c @ 15

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

needed libs update

File size: 13.0 KB
Line 
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
18typedef 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
28typedef 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
69LOCAL(void)
70build_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
119METHODDEF(void)
120ycc_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
168METHODDEF(void)
169null_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
200METHODDEF(void)
201grayscale_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
216METHODDEF(void)
217gray_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
244METHODDEF(void)
245ycck_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
292METHODDEF(void)
293start_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
303GLOBAL(void)
304jinit_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}
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