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jccolor.c
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1 /*
2  * jccolor.c
3  *
4  * Copyright (C) 1991-1994, 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 */
24 
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
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
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 
185 METHODDEF void
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 
224 METHODDEF void
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 
279 METHODDEF void
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 
308 METHODDEF void
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 
340 METHODDEF void
342 {
343  /* no work needed */
344 }
345 
346 
347 /*
348  * Module initialization routine for input colorspace conversion.
349  */
350 
351 GLOBAL void
353 {
354  my_cconvert_ptr cconvert;
355 
356  cconvert = (my_cconvert_ptr)
357  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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 }
GLubyte g
Definition: glext.h:4662
#define R_Y_OFF
Definition: jccolor.c:69
char JSAMPLE
Definition: jmorecfg.h:64
JSAMPLE FAR * JSAMPROW
Definition: jpeglib.h:79
J_COLOR_SPACE jpeg_color_space
Definition: jpeglib.h:296
METHODDEF void rgb_ycc_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
Definition: jccolor.c:130
#define SCALEBITS
Definition: jccolor.c:58
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:260
INT32 * rgb_ycc_tab
Definition: jccolor.c:22
my_color_converter * my_cconvert_ptr
Definition: jccolor.c:25
METHODDEF void rgb_ycc_start(j_compress_ptr cinfo)
Definition: jccolor.c:86
#define GETJSAMPLE(value)
Definition: jmorecfg.h:68
struct jpeg_color_converter * cconvert
Definition: jpeglib.h:397
METHODDEF void cmyk_ycck_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
Definition: jccolor.c:225
#define ERREXIT(cinfo, code)
Definition: jerror.h:193
#define G_CB_OFF
Definition: jccolor.c:73
#define SIZEOF(object)
Definition: jinclude.h:80
METHODDEF void rgb_gray_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
Definition: jccolor.c:186
#define MAXJSAMPLE
Definition: jmorecfg.h:73
#define B_CB_OFF
Definition: jccolor.c:74
long INT32
Definition: jmorecfg.h:154
METHODDEF void null_method(j_compress_ptr cinfo)
Definition: jccolor.c:341
#define R_CR_OFF
Definition: jccolor.c:75
int i
Definition: process.py:33
J_COLOR_SPACE in_color_space
Definition: jpeglib.h:281
#define CBCR_OFFSET
Definition: jccolor.c:59
#define JPOOL_IMAGE
Definition: jpeglib.h:736
#define G_CR_OFF
Definition: jccolor.c:76
#define ONE_HALF
Definition: jccolor.c:60
#define G_Y_OFF
Definition: jccolor.c:70
#define R_CB_OFF
Definition: jccolor.c:72
struct jpeg_color_converter pub
Definition: jccolor.c:19
#define GLOBAL
Definition: jmorecfg.h:190
JSAMPARRAY * JSAMPIMAGE
Definition: jpeglib.h:81
#define METHODDEF
Definition: jmorecfg.h:188
GLOBAL void jinit_color_converter(j_compress_ptr cinfo)
Definition: jccolor.c:352
GLubyte GLubyte b
Definition: glext.h:4662
#define B_Y_OFF
Definition: jccolor.c:71
JSAMPROW * JSAMPARRAY
Definition: jpeglib.h:80
GLdouble GLdouble GLdouble r
Definition: glext.h:2951
#define FIX(x)
Definition: jccolor.c:61
#define B_CR_OFF
Definition: jccolor.c:77
#define TABLE_SIZE
Definition: jccolor.c:78
unsigned int JDIMENSION
Definition: jmorecfg.h:177
METHODDEF void grayscale_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
Definition: jccolor.c:280
METHODDEF void null_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
Definition: jccolor.c:309
JDIMENSION image_width
Definition: jpeglib.h:278