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jdcolor.c
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1 /*
2  * jdcolor.c
3  *
4  * Copyright (C) 1991-1995, 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 */
27 
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
71 {
72  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
73  int i;
74  INT32 x;
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
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;
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
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
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  * Adobe-style YCCK->CMYK conversion.
212  * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
213  * conversion as above, while passing K (black) unchanged.
214  * We assume build_ycc_rgb_table has been called.
215  */
216 
217 METHODDEF void
219  JSAMPIMAGE input_buf, JDIMENSION input_row,
220  JSAMPARRAY output_buf, int num_rows)
221 {
222  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
223  register int y, cb, cr;
224  register JSAMPROW outptr;
225  register JSAMPROW inptr0, inptr1, inptr2, inptr3;
226  register JDIMENSION col;
227  JDIMENSION num_cols = cinfo->output_width;
228  /* copy these pointers into registers if possible */
229  register JSAMPLE * range_limit = cinfo->sample_range_limit;
230  register int * Crrtab = cconvert->Cr_r_tab;
231  register int * Cbbtab = cconvert->Cb_b_tab;
232  register INT32 * Crgtab = cconvert->Cr_g_tab;
233  register INT32 * Cbgtab = cconvert->Cb_g_tab;
235 
236  while (--num_rows >= 0) {
237  inptr0 = input_buf[0][input_row];
238  inptr1 = input_buf[1][input_row];
239  inptr2 = input_buf[2][input_row];
240  inptr3 = input_buf[3][input_row];
241  input_row++;
242  outptr = *output_buf++;
243  for (col = 0; col < num_cols; col++) {
244  y = GETJSAMPLE(inptr0[col]);
245  cb = GETJSAMPLE(inptr1[col]);
246  cr = GETJSAMPLE(inptr2[col]);
247  /* Range-limiting is essential due to noise introduced by DCT losses. */
248  outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */
249  outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */
250  ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
251  SCALEBITS)))];
252  outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */
253  /* K passes through unchanged */
254  outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */
255  outptr += 4;
256  }
257  }
258 }
259 
260 
261 /*
262  * Empty method for start_pass.
263  */
264 
265 METHODDEF void
267 {
268  /* no work needed */
269 }
270 
271 
272 /*
273  * Module initialization routine for output colorspace conversion.
274  */
275 
276 GLOBAL void
278 {
279  my_cconvert_ptr cconvert;
280  int ci;
281 
282  cconvert = (my_cconvert_ptr)
283  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
285  cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
286  cconvert->pub.start_pass = start_pass_dcolor;
287 
288  /* Make sure num_components agrees with jpeg_color_space */
289  switch (cinfo->jpeg_color_space) {
290  case JCS_GRAYSCALE:
291  if (cinfo->num_components != 1)
292  ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
293  break;
294 
295  case JCS_RGB:
296  case JCS_YCbCr:
297  if (cinfo->num_components != 3)
298  ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
299  break;
300 
301  case JCS_CMYK:
302  case JCS_YCCK:
303  if (cinfo->num_components != 4)
304  ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
305  break;
306 
307  default: /* JCS_UNKNOWN can be anything */
308  if (cinfo->num_components < 1)
309  ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
310  break;
311  }
312 
313  /* Set out_color_components and conversion method based on requested space.
314  * Also clear the component_needed flags for any unused components,
315  * so that earlier pipeline stages can avoid useless computation.
316  */
317 
318  switch (cinfo->out_color_space) {
319  case JCS_GRAYSCALE:
320  cinfo->out_color_components = 1;
321  if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
322  cinfo->jpeg_color_space == JCS_YCbCr) {
323  cconvert->pub.color_convert = grayscale_convert;
324  /* For color->grayscale conversion, only the Y (0) component is needed */
325  for (ci = 1; ci < cinfo->num_components; ci++)
326  cinfo->comp_info[ci].component_needed = FALSE;
327  } else
328  ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
329  break;
330 
331  case JCS_RGB:
332  cinfo->out_color_components = RGB_PIXELSIZE;
333  if (cinfo->jpeg_color_space == JCS_YCbCr) {
334  cconvert->pub.color_convert = ycc_rgb_convert;
335  build_ycc_rgb_table(cinfo);
336  } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
337  cconvert->pub.color_convert = null_convert;
338  } else
339  ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
340  break;
341 
342  case JCS_CMYK:
343  cinfo->out_color_components = 4;
344  if (cinfo->jpeg_color_space == JCS_YCCK) {
345  cconvert->pub.color_convert = ycck_cmyk_convert;
346  build_ycc_rgb_table(cinfo);
347  } else if (cinfo->jpeg_color_space == JCS_CMYK) {
348  cconvert->pub.color_convert = null_convert;
349  } else
350  ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
351  break;
352 
353  default:
354  /* Permit null conversion to same output space */
355  if (cinfo->out_color_space == cinfo->jpeg_color_space) {
356  cinfo->out_color_components = cinfo->num_components;
357  cconvert->pub.color_convert = null_convert;
358  } else /* unsupported non-null conversion */
359  ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
360  break;
361  }
362 
363  if (cinfo->quantize_colors)
364  cinfo->output_components = 1; /* single colormapped output component */
365  else
366  cinfo->output_components = cinfo->out_color_components;
367 }
#define CENTERJSAMPLE
Definition: jmorecfg.h:74
char JSAMPLE
Definition: jmorecfg.h:64
METHODDEF void null_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
Definition: jdcolor.c:169
JSAMPLE FAR * JSAMPROW
Definition: jpeglib.h:79
GLOBAL void jcopy_sample_rows(JSAMPARRAY input_array, int source_row, JSAMPARRAY output_array, int dest_row, int num_rows, JDIMENSION num_cols)
Definition: jutils.c:107
jpeg_component_info * comp_info
Definition: jpeglib.h:530
METHODDEF void ycc_rgb_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
Definition: jdcolor.c:120
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:260
boolean quantize_colors
Definition: jpeglib.h:438
GLenum GLint GLint y
Definition: glext.h:2849
case const int
Definition: Callbacks.cpp:52
#define GETJSAMPLE(value)
Definition: jmorecfg.h:68
#define LOCAL
Definition: jmorecfg.h:189
#define ERREXIT(cinfo, code)
Definition: jerror.h:193
JDIMENSION output_width
Definition: jpeglib.h:454
#define SIZEOF(object)
Definition: jinclude.h:80
#define MAXJSAMPLE
Definition: jmorecfg.h:73
boolean component_needed
Definition: jpeglib.h:172
METHODDEF void start_pass_dcolor(j_decompress_ptr cinfo)
Definition: jdcolor.c:266
long INT32
Definition: jmorecfg.h:154
#define SHIFT_TEMPS
Definition: jpegint.h:287
GLenum GLint x
Definition: glext.h:2849
int i
Definition: process.py:33
#define JPOOL_IMAGE
Definition: jpeglib.h:736
METHODDEF void ycck_cmyk_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
Definition: jdcolor.c:218
J_COLOR_SPACE out_color_space
Definition: jpeglib.h:425
#define FIX(x)
Definition: jdcolor.c:62
GLuint GLuint GLsizei count
Definition: glext.h:2845
LOCAL void build_ycc_rgb_table(j_decompress_ptr cinfo)
Definition: jdcolor.c:70
JSAMPLE * sample_range_limit
Definition: jpeglib.h:576
#define SCALEBITS
Definition: jdcolor.c:60
my_color_deconverter * my_cconvert_ptr
Definition: jdcolor.c:28
struct jpeg_color_converter pub
Definition: jccolor.c:19
INT32 * Cb_g_tab
Definition: jdcolor.c:25
#define GLOBAL
Definition: jmorecfg.h:190
JSAMPARRAY * JSAMPIMAGE
Definition: jpeglib.h:81
#define METHODDEF
Definition: jmorecfg.h:188
struct jpeg_color_deconverter * cconvert
Definition: jpeglib.h:615
JSAMPROW * JSAMPARRAY
Definition: jpeglib.h:80
#define RIGHT_SHIFT(x, shft)
Definition: jpegint.h:288
#define ONE_HALF
Definition: jdcolor.c:61
#define FALSE
Definition: mprintf.c:70
METHODDEF void grayscale_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
Definition: jdcolor.c:201
unsigned int JDIMENSION
Definition: jmorecfg.h:177
GLOBAL void jinit_color_deconverter(j_decompress_ptr cinfo)
Definition: jdcolor.c:277
INT32 * Cr_g_tab
Definition: jdcolor.c:24
J_COLOR_SPACE jpeg_color_space
Definition: jpeglib.h:418