1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * jccolor.c
7 *
8 * Copyright (C) 1991-1996, Thomas G. Lane.
9 * This file is part of the Independent JPEG Group's software.
10 * For conditions of distribution and use, see the accompanying README file.
11 *
12 * This file contains input colorspace conversion routines.
13 */
14
15#define JPEG_INTERNALS
16#include "jinclude.h"
17#include "jpeglib.h"
18
19
20/* Private subobject */
21
22typedef struct {
23  struct jpeg_color_converter pub; /* public fields */
24
25  /* Private state for RGB->YCC conversion */
26  INT32 * rgb_ycc_tab;          /* => table for RGB to YCbCr conversion */
27} my_color_converter;
28
29typedef my_color_converter * my_cconvert_ptr;
30
31
32/**************** RGB -> YCbCr conversion: most common case **************/
33
34/*
35 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
36 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
37 * The conversion equations to be implemented are therefore
38 *      Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
39 *      Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE
40 *      Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
41 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
42 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
43 * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
44 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
45 * were not represented exactly.  Now we sacrifice exact representation of
46 * maximum red and maximum blue in order to get exact grayscales.
47 *
48 * To avoid floating-point arithmetic, we represent the fractional constants
49 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
50 * the products by 2^16, with appropriate rounding, to get the correct answer.
51 *
52 * For even more speed, we avoid doing any multiplications in the inner loop
53 * by precalculating the constants times R,G,B for all possible values.
54 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
55 * for 12-bit samples it is still acceptable.  It's not very reasonable for
56 * 16-bit samples, but if you want lossless storage you shouldn't be changing
57 * colorspace anyway.
58 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
59 * in the tables to save adding them separately in the inner loop.
60 */
61
62#define SCALEBITS       16      /* speediest right-shift on some machines */
63#define CBCR_OFFSET     ((INT32) CENTERJSAMPLE << SCALEBITS)
64#define ONE_HALF        ((INT32) 1 << (SCALEBITS-1))
65#define FIX(x)          ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
66
67/* We allocate one big table and divide it up into eight parts, instead of
68 * doing eight alloc_small requests.  This lets us use a single table base
69 * address, which can be held in a register in the inner loops on many
70 * machines (more than can hold all eight addresses, anyway).
71 */
72
73#define R_Y_OFF         0                       /* offset to R => Y section */
74#define G_Y_OFF         (1*(MAXJSAMPLE+1))      /* offset to G => Y section */
75#define B_Y_OFF         (2*(MAXJSAMPLE+1))      /* etc. */
76#define R_CB_OFF        (3*(MAXJSAMPLE+1))
77#define G_CB_OFF        (4*(MAXJSAMPLE+1))
78#define B_CB_OFF        (5*(MAXJSAMPLE+1))
79#define R_CR_OFF        B_CB_OFF                /* B=>Cb, R=>Cr are the same */
80#define G_CR_OFF        (6*(MAXJSAMPLE+1))
81#define B_CR_OFF        (7*(MAXJSAMPLE+1))
82#define TABLE_SIZE      (8*(MAXJSAMPLE+1))
83
84
85/*
86 * Initialize for RGB->YCC colorspace conversion.
87 */
88
89METHODDEF(void)
90rgb_ycc_start (j_compress_ptr cinfo)
91{
92  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
93  INT32 * rgb_ycc_tab;
94  INT32 i;
95
96  /* Allocate and fill in the conversion tables. */
97  cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)
98    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
99                                (TABLE_SIZE * SIZEOF(INT32)));
100
101  for (i = 0; i <= MAXJSAMPLE; i++) {
102    rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
103    rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
104    rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i     + ONE_HALF;
105    rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
106    rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
107    /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
108     * This ensures that the maximum output will round to MAXJSAMPLE
109     * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
110     */
111    rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
112/*  B=>Cb and R=>Cr tables are the same
113    rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
114*/
115    rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
116    rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
117  }
118}
119
120
121/*
122 * Convert some rows of samples to the JPEG colorspace.
123 *
124 * Note that we change from the application's interleaved-pixel format
125 * to our internal noninterleaved, one-plane-per-component format.
126 * The input buffer is therefore three times as wide as the output buffer.
127 *
128 * A starting row offset is provided only for the output buffer.  The caller
129 * can easily adjust the passed input_buf value to accommodate any row
130 * offset required on that side.
131 */
132
133METHODDEF(void)
134rgb_ycc_convert (j_compress_ptr cinfo,
135                 JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
136                 JDIMENSION output_row, int num_rows)
137{
138  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
139  register int r, g, b;
140  register INT32 * ctab = cconvert->rgb_ycc_tab;
141  register JSAMPROW inptr;
142  register JSAMPROW outptr0, outptr1, outptr2;
143  register JDIMENSION col;
144  JDIMENSION num_cols = cinfo->image_width;
145
146  while (--num_rows >= 0) {
147    inptr = *input_buf++;
148    outptr0 = output_buf[0][output_row];
149    outptr1 = output_buf[1][output_row];
150    outptr2 = output_buf[2][output_row];
151    output_row++;
152    for (col = 0; col < num_cols; col++) {
153      r = GETJSAMPLE(inptr[RGB_RED]);
154      g = GETJSAMPLE(inptr[RGB_GREEN]);
155      b = GETJSAMPLE(inptr[RGB_BLUE]);
156      inptr += RGB_PIXELSIZE;
157      /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
158       * must be too; we do not need an explicit range-limiting operation.
159       * Hence the value being shifted is never negative, and we don't
160       * need the general RIGHT_SHIFT macro.
161       */
162      /* Y */
163      outptr0[col] = (JSAMPLE)
164                ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
165                 >> SCALEBITS);
166      /* Cb */
167      outptr1[col] = (JSAMPLE)
168                ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
169                 >> SCALEBITS);
170      /* Cr */
171      outptr2[col] = (JSAMPLE)
172                ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
173                 >> SCALEBITS);
174    }
175  }
176}
177
178
179/**************** Cases other than RGB -> YCbCr **************/
180
181
182/*
183 * Convert some rows of samples to the JPEG colorspace.
184 * This version handles RGB->grayscale conversion, which is the same
185 * as the RGB->Y portion of RGB->YCbCr.
186 * We assume rgb_ycc_start has been called (we only use the Y tables).
187 */
188
189METHODDEF(void)
190rgb_gray_convert (j_compress_ptr cinfo,
191                  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
192                  JDIMENSION output_row, int num_rows)
193{
194  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
195  register int r, g, b;
196  register INT32 * ctab = cconvert->rgb_ycc_tab;
197  register JSAMPROW inptr;
198  register JSAMPROW outptr;
199  register JDIMENSION col;
200  JDIMENSION num_cols = cinfo->image_width;
201
202  while (--num_rows >= 0) {
203    inptr = *input_buf++;
204    outptr = output_buf[0][output_row];
205    output_row++;
206    for (col = 0; col < num_cols; col++) {
207      r = GETJSAMPLE(inptr[RGB_RED]);
208      g = GETJSAMPLE(inptr[RGB_GREEN]);
209      b = GETJSAMPLE(inptr[RGB_BLUE]);
210      inptr += RGB_PIXELSIZE;
211      /* Y */
212      outptr[col] = (JSAMPLE)
213                ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
214                 >> SCALEBITS);
215    }
216  }
217}
218
219/*
220 * Convert some rows of samples to the JPEG colorspace.
221 * This version handles Adobe-style CMYK->YCCK conversion,
222 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
223 * conversion as above, while passing K (black) unchanged.
224 * We assume rgb_ycc_start has been called.
225 */
226
227METHODDEF(void)
228cmyk_ycck_convert (j_compress_ptr cinfo,
229                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
230                   JDIMENSION output_row, int num_rows)
231{
232  my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
233  register int r, g, b;
234  register INT32 * ctab = cconvert->rgb_ycc_tab;
235  register JSAMPROW inptr;
236  register JSAMPROW outptr0, outptr1, outptr2, outptr3;
237  register JDIMENSION col;
238  JDIMENSION num_cols = cinfo->image_width;
239
240  while (--num_rows >= 0) {
241    inptr = *input_buf++;
242    outptr0 = output_buf[0][output_row];
243    outptr1 = output_buf[1][output_row];
244    outptr2 = output_buf[2][output_row];
245    outptr3 = output_buf[3][output_row];
246    output_row++;
247    for (col = 0; col < num_cols; col++) {
248      r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
249      g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
250      b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
251      /* K passes through as-is */
252      outptr3[col] = inptr[3];  /* don't need GETJSAMPLE here */
253      inptr += 4;
254      /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
255       * must be too; we do not need an explicit range-limiting operation.
256       * Hence the value being shifted is never negative, and we don't
257       * need the general RIGHT_SHIFT macro.
258       */
259      /* Y */
260      outptr0[col] = (JSAMPLE)
261                ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
262                 >> SCALEBITS);
263      /* Cb */
264      outptr1[col] = (JSAMPLE)
265                ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
266                 >> SCALEBITS);
267      /* Cr */
268      outptr2[col] = (JSAMPLE)
269                ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
270                 >> SCALEBITS);
271    }
272  }
273}
274
275
276/*
277 * Convert some rows of samples to the JPEG colorspace.
278 * This version handles grayscale output with no conversion.
279 * The source can be either plain grayscale or YCbCr (since Y == gray).
280 */
281
282METHODDEF(void)
283grayscale_convert (j_compress_ptr cinfo,
284                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
285                   JDIMENSION output_row, int num_rows)
286{
287  register JSAMPROW inptr;
288  register JSAMPROW outptr;
289  register JDIMENSION col;
290  JDIMENSION num_cols = cinfo->image_width;
291  int instride = cinfo->input_components;
292
293  while (--num_rows >= 0) {
294    inptr = *input_buf++;
295    outptr = output_buf[0][output_row];
296    output_row++;
297    for (col = 0; col < num_cols; col++) {
298      outptr[col] = inptr[0];   /* don't need GETJSAMPLE() here */
299      inptr += instride;
300    }
301  }
302}
303
304
305/*
306 * Convert some rows of samples to the JPEG colorspace.
307 * This version handles multi-component colorspaces without conversion.
308 * We assume input_components == num_components.
309 */
310
311METHODDEF(void)
312null_convert (j_compress_ptr cinfo,
313              JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
314              JDIMENSION output_row, int num_rows)
315{
316  register JSAMPROW inptr;
317  register JSAMPROW outptr;
318  register JDIMENSION col;
319  register int ci;
320  int nc = cinfo->num_components;
321  JDIMENSION num_cols = cinfo->image_width;
322
323  while (--num_rows >= 0) {
324    /* It seems fastest to make a separate pass for each component. */
325    for (ci = 0; ci < nc; ci++) {
326      inptr = *input_buf;
327      outptr = output_buf[ci][output_row];
328      for (col = 0; col < num_cols; col++) {
329        outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
330        inptr += nc;
331      }
332    }
333    input_buf++;
334    output_row++;
335  }
336}
337
338
339/*
340 * Empty method for start_pass.
341 */
342
343METHODDEF(void)
344null_method (j_compress_ptr cinfo)
345{
346  /* no work needed */
347}
348
349
350/*
351 * Module initialization routine for input colorspace conversion.
352 */
353
354GLOBAL(void)
355jinit_color_converter (j_compress_ptr cinfo)
356{
357  my_cconvert_ptr cconvert;
358
359  cconvert = (my_cconvert_ptr)
360    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
361                                SIZEOF(my_color_converter));
362  cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
363  /* set start_pass to null method until we find out differently */
364  cconvert->pub.start_pass = null_method;
365
366  /* Make sure input_components agrees with in_color_space */
367  switch (cinfo->in_color_space) {
368  case JCS_GRAYSCALE:
369    if (cinfo->input_components != 1)
370      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
371    break;
372
373  case JCS_RGB:
374#if RGB_PIXELSIZE != 3
375    if (cinfo->input_components != RGB_PIXELSIZE)
376      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
377    break;
378#endif /* else share code with YCbCr */
379
380  case JCS_YCbCr:
381    if (cinfo->input_components != 3)
382      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
383    break;
384
385  case JCS_CMYK:
386  case JCS_YCCK:
387    if (cinfo->input_components != 4)
388      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
389    break;
390
391  default:                      /* JCS_UNKNOWN can be anything */
392    if (cinfo->input_components < 1)
393      ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
394    break;
395  }
396
397  /* Check num_components, set conversion method based on requested space */
398  switch (cinfo->jpeg_color_space) {
399  case JCS_GRAYSCALE:
400    if (cinfo->num_components != 1)
401      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
402    if (cinfo->in_color_space == JCS_GRAYSCALE)
403      cconvert->pub.color_convert = grayscale_convert;
404    else if (cinfo->in_color_space == JCS_RGB) {
405      cconvert->pub.start_pass = rgb_ycc_start;
406      cconvert->pub.color_convert = rgb_gray_convert;
407    } else if (cinfo->in_color_space == JCS_YCbCr)
408      cconvert->pub.color_convert = grayscale_convert;
409    else
410      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
411    break;
412
413  case JCS_RGB:
414    if (cinfo->num_components != 3)
415      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
416    if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
417      cconvert->pub.color_convert = null_convert;
418    else
419      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
420    break;
421
422  case JCS_YCbCr:
423    if (cinfo->num_components != 3)
424      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
425    if (cinfo->in_color_space == JCS_RGB) {
426      cconvert->pub.start_pass = rgb_ycc_start;
427      cconvert->pub.color_convert = rgb_ycc_convert;
428    } else if (cinfo->in_color_space == JCS_YCbCr)
429      cconvert->pub.color_convert = null_convert;
430    else
431      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
432    break;
433
434  case JCS_CMYK:
435    if (cinfo->num_components != 4)
436      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
437    if (cinfo->in_color_space == JCS_CMYK)
438      cconvert->pub.color_convert = null_convert;
439    else
440      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
441    break;
442
443  case JCS_YCCK:
444    if (cinfo->num_components != 4)
445      ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
446    if (cinfo->in_color_space == JCS_CMYK) {
447      cconvert->pub.start_pass = rgb_ycc_start;
448      cconvert->pub.color_convert = cmyk_ycck_convert;
449    } else if (cinfo->in_color_space == JCS_YCCK)
450      cconvert->pub.color_convert = null_convert;
451    else
452      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
453    break;
454
455  default:                      /* allow null conversion of JCS_UNKNOWN */
456    if (cinfo->jpeg_color_space != cinfo->in_color_space ||
457        cinfo->num_components != cinfo->input_components)
458      ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
459    cconvert->pub.color_convert = null_convert;
460    break;
461  }
462}
463