compiler/libjpeg/main/jccolor.c

   1 /*
   2     $Id$
   3 */
   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
  22 typedef 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
  29 typedef 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
  89 METHODDEF(void)
  90 rgb_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
 133 METHODDEF(void)
 134 rgb_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
 189 METHODDEF(void)
 190 rgb_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 /*
 221  * Convert some rows of samples to the JPEG colorspace.
 222  * This version handles Adobe-style CMYK->YCCK conversion,
 223  * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 224  * conversion as above, while passing K (black) unchanged.
 225  * We assume rgb_ycc_start has been called.
 226  */
 227
 228 METHODDEF(void)
 229 cmyk_ycck_convert (j_compress_ptr cinfo,
 230                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 231                    JDIMENSION output_row, int num_rows)
 232 {
 233   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 234   register int r, g, b;
 235   register INT32 * ctab = cconvert->rgb_ycc_tab;
 236   register JSAMPROW inptr;
 237   register JSAMPROW outptr0, outptr1, outptr2, outptr3;
 238   register JDIMENSION col;
 239   JDIMENSION num_cols = cinfo->image_width;
 240
 241   while (--num_rows >= 0) {
 242     inptr = *input_buf++;
 243     outptr0 = output_buf[0][output_row];
 244     outptr1 = output_buf[1][output_row];
 245     outptr2 = output_buf[2][output_row];
 246     outptr3 = output_buf[3][output_row];
 247     output_row++;
 248     for (col = 0; col < num_cols; col++) {
 249       r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
 250       g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
 251       b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
 252       /* K passes through as-is */
 253       outptr3[col] = inptr[3];  /* don't need GETJSAMPLE here */
 254       inptr += 4;
 255       /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
 256        * must be too; we do not need an explicit range-limiting operation.
 257        * Hence the value being shifted is never negative, and we don't
 258        * need the general RIGHT_SHIFT macro.
 259        */
 260       /* Y */
 261       outptr0[col] = (JSAMPLE)
 262                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 263                  >> SCALEBITS);
 264       /* Cb */
 265       outptr1[col] = (JSAMPLE)
 266                 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
 267                  >> SCALEBITS);
 268       /* Cr */
 269       outptr2[col] = (JSAMPLE)
 270                 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
 271                  >> SCALEBITS);
 272     }
 273   }
 274 }
 275
 276
 277 /*
 278  * Convert some rows of samples to the JPEG colorspace.
 279  * This version handles grayscale output with no conversion.
 280  * The source can be either plain grayscale or YCbCr (since Y == gray).
 281  */
 282
 283 METHODDEF(void)
 284 grayscale_convert (j_compress_ptr cinfo,
 285                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 286                    JDIMENSION output_row, int num_rows)
 287 {
 288   register JSAMPROW inptr;
 289   register JSAMPROW outptr;
 290   register JDIMENSION col;
 291   JDIMENSION num_cols = cinfo->image_width;
 292   int instride = cinfo->input_components;
 293
 294   while (--num_rows >= 0) {
 295     inptr = *input_buf++;
 296     outptr = output_buf[0][output_row];
 297     output_row++;
 298     for (col = 0; col < num_cols; col++) {
 299       outptr[col] = inptr[0];   /* don't need GETJSAMPLE() here */
 300       inptr += instride;
 301     }
 302   }
 303 }
 304
 305
 306 /*
 307  * Convert some rows of samples to the JPEG colorspace.
 308  * This version handles multi-component colorspaces without conversion.
 309  * We assume input_components == num_components.
 310  */
 311
 312 METHODDEF(void)
 313 null_convert (j_compress_ptr cinfo,
 314               JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 315               JDIMENSION output_row, int num_rows)
 316 {
 317   register JSAMPROW inptr;
 318   register JSAMPROW outptr;
 319   register JDIMENSION col;
 320   register int ci;
 321   int nc = cinfo->num_components;
 322   JDIMENSION num_cols = cinfo->image_width;
 323
 324   while (--num_rows >= 0) {
 325     /* It seems fastest to make a separate pass for each component. */
 326     for (ci = 0; ci < nc; ci++) {
 327       inptr = *input_buf;
 328       outptr = output_buf[ci][output_row];
 329       for (col = 0; col < num_cols; col++) {
 330         outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
 331         inptr += nc;
 332       }
 333     }
 334     input_buf++;
 335     output_row++;
 336   }
 337 }
 338
 339
 340 /*
 341  * Empty method for start_pass.
 342  */
 343
 344 METHODDEF(void)
 345 null_method (j_compress_ptr cinfo)
 346 {
 347   /* no work needed */
 348 }
 349
 350
 351 /*
 352  * Module initialization routine for input colorspace conversion.
 353  */
 354
 355 JGLOBAL(void)
 356 jinit_color_converter (j_compress_ptr cinfo)
 357 {
 358   my_cconvert_ptr cconvert;
 359
 360   cconvert = (my_cconvert_ptr)
 361     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 362                                 SIZEOF(my_color_converter));
 363   cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
 364   /* set start_pass to null method until we find out differently */
 365   cconvert->pub.start_pass = null_method;
 366
 367   /* Make sure input_components agrees with in_color_space */
 368   switch (cinfo->in_color_space) {
 369   case JCS_GRAYSCALE:
 370     if (cinfo->input_components != 1)
 371       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 372     break;
 373
 374   case JCS_RGB:
 375 #if RGB_PIXELSIZE != 3
 376     if (cinfo->input_components != RGB_PIXELSIZE)
 377       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 378     break;
 379 #endif /* else share code with YCbCr */
 380
 381   case JCS_YCbCr:
 382     if (cinfo->input_components != 3)
 383       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 384     break;
 385
 386   case JCS_CMYK:
 387   case JCS_YCCK:
 388     if (cinfo->input_components != 4)
 389       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 390     break;
 391
 392   default:                      /* JCS_UNKNOWN can be anything */
 393     if (cinfo->input_components < 1)
 394       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 395     break;
 396   }
 397
 398   /* Check num_components, set conversion method based on requested space */
 399   switch (cinfo->jpeg_color_space) {
 400   case JCS_GRAYSCALE:
 401     if (cinfo->num_components != 1)
 402       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 403     if (cinfo->in_color_space == JCS_GRAYSCALE)
 404       cconvert->pub.color_convert = grayscale_convert;
 405     else if (cinfo->in_color_space == JCS_RGB) {
 406       cconvert->pub.start_pass = rgb_ycc_start;
 407       cconvert->pub.color_convert = rgb_gray_convert;
 408     } else if (cinfo->in_color_space == JCS_YCbCr)
 409       cconvert->pub.color_convert = grayscale_convert;
 410     else
 411       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 412     break;
 413
 414   case JCS_RGB:
 415     if (cinfo->num_components != 3)
 416       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 417     if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3)
 418       cconvert->pub.color_convert = null_convert;
 419     else
 420       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 421     break;
 422
 423   case JCS_YCbCr:
 424     if (cinfo->num_components != 3)
 425       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 426     if (cinfo->in_color_space == JCS_RGB) {
 427       cconvert->pub.start_pass = rgb_ycc_start;
 428       cconvert->pub.color_convert = rgb_ycc_convert;
 429     } else if (cinfo->in_color_space == JCS_YCbCr)
 430       cconvert->pub.color_convert = null_convert;
 431     else
 432       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 433     break;
 434
 435   case JCS_CMYK:
 436     if (cinfo->num_components != 4)
 437       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 438     if (cinfo->in_color_space == JCS_CMYK)
 439       cconvert->pub.color_convert = null_convert;
 440     else
 441       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 442     break;
 443
 444   case JCS_YCCK:
 445     if (cinfo->num_components != 4)
 446       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 447     if (cinfo->in_color_space == JCS_CMYK) {
 448       cconvert->pub.start_pass = rgb_ycc_start;
 449       cconvert->pub.color_convert = cmyk_ycck_convert;
 450     } else if (cinfo->in_color_space == JCS_YCCK)
 451       cconvert->pub.color_convert = null_convert;
 452     else
 453       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 454     break;
 455
 456   default:                      /* allow null conversion of JCS_UNKNOWN */
 457     if (cinfo->jpeg_color_space != cinfo->in_color_space ||
 458         cinfo->num_components != cinfo->input_components)
 459       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 460     cconvert->pub.color_convert = null_convert;
 461     break;
 462   }
 463 }