workbench/libs/jpeg/jccolor.c

   1 /*
   2  * jccolor.c
   3  *
   4  * Copyright (C) 1991-1996, Thomas G. Lane.
   5  * Modified 2011-2012 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains input colorspace conversion routines.
  10  */
  11
  12 #define JPEG_INTERNALS
  13 #include "jinclude.h"
  14 #include "jpeglib.h"
  15
  16
  17 /* Private subobject */
  18
  19 typedef struct {
  20   struct jpeg_color_converter pub; /* public fields */
  21
  22   /* Private state for RGB->YCC conversion */
  23   INT32 * rgb_ycc_tab;          /* => table for RGB to YCbCr conversion */
  24 } my_color_converter;
  25
  26 typedef my_color_converter * my_cconvert_ptr;
  27
  28
  29 /**************** RGB -> YCbCr conversion: most common case **************/
  30
  31 /*
  32  * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
  33  * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
  34  * The conversion equations to be implemented are therefore
  35  *      Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
  36  *      Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE
  37  *      Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
  38  * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
  39  * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
  40  * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
  41  * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
  42  * were not represented exactly.  Now we sacrifice exact representation of
  43  * maximum red and maximum blue in order to get exact grayscales.
  44  *
  45  * To avoid floating-point arithmetic, we represent the fractional constants
  46  * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
  47  * the products by 2^16, with appropriate rounding, to get the correct answer.
  48  *
  49  * For even more speed, we avoid doing any multiplications in the inner loop
  50  * by precalculating the constants times R,G,B 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 CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
  56  * in the tables to save adding them separately in the inner loop.
  57  */
  58
  59 #define SCALEBITS       16      /* speediest right-shift on some machines */
  60 #define CBCR_OFFSET     ((INT32) CENTERJSAMPLE << SCALEBITS)
  61 #define ONE_HALF        ((INT32) 1 << (SCALEBITS-1))
  62 #define FIX(x)          ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
  63
  64 /* We allocate one big table and divide it up into eight parts, instead of
  65  * doing eight alloc_small requests.  This lets us use a single table base
  66  * address, which can be held in a register in the inner loops on many
  67  * machines (more than can hold all eight addresses, anyway).
  68  */
  69
  70 #define R_Y_OFF         0                       /* offset to R => Y section */
  71 #define G_Y_OFF         (1*(MAXJSAMPLE+1))      /* offset to G => Y section */
  72 #define B_Y_OFF         (2*(MAXJSAMPLE+1))      /* etc. */
  73 #define R_CB_OFF        (3*(MAXJSAMPLE+1))
  74 #define G_CB_OFF        (4*(MAXJSAMPLE+1))
  75 #define B_CB_OFF        (5*(MAXJSAMPLE+1))
  76 #define R_CR_OFF        B_CB_OFF                /* B=>Cb, R=>Cr are the same */
  77 #define G_CR_OFF        (6*(MAXJSAMPLE+1))
  78 #define B_CR_OFF        (7*(MAXJSAMPLE+1))
  79 #define TABLE_SIZE      (8*(MAXJSAMPLE+1))
  80
  81
  82 /*
  83  * Initialize for RGB->YCC colorspace conversion.
  84  */
  85
  86 METHODDEF(void)
  87 rgb_ycc_start (j_compress_ptr cinfo)
  88 {
  89   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
  90   INT32 * rgb_ycc_tab;
  91   INT32 i;
  92
  93   /* Allocate and fill in the conversion tables. */
  94   cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)
  95     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  96                                 (TABLE_SIZE * SIZEOF(INT32)));
  97
  98   for (i = 0; i <= MAXJSAMPLE; i++) {
  99     rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
 100     rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
 101     rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i     + ONE_HALF;
 102     rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
 103     rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
 104     /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
 105      * This ensures that the maximum output will round to MAXJSAMPLE
 106      * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
 107      */
 108     rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
 109 /*  B=>Cb and R=>Cr tables are the same
 110     rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
 111 */
 112     rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
 113     rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
 114   }
 115 }
 116
 117
 118 /*
 119  * Convert some rows of samples to the JPEG colorspace.
 120  *
 121  * Note that we change from the application's interleaved-pixel format
 122  * to our internal noninterleaved, one-plane-per-component format.
 123  * The input buffer is therefore three times as wide as the output buffer.
 124  *
 125  * A starting row offset is provided only for the output buffer.  The caller
 126  * can easily adjust the passed input_buf value to accommodate any row
 127  * offset required on that side.
 128  */
 129
 130 METHODDEF(void)
 131 rgb_ycc_convert (j_compress_ptr cinfo,
 132                  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 133                  JDIMENSION output_row, int num_rows)
 134 {
 135   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 136   register INT32 * ctab = cconvert->rgb_ycc_tab;
 137   register int r, g, b;
 138   register JSAMPROW inptr;
 139   register JSAMPROW outptr0, outptr1, outptr2;
 140   register JDIMENSION col;
 141   JDIMENSION num_cols = cinfo->image_width;
 142
 143   while (--num_rows >= 0) {
 144     inptr = *input_buf++;
 145     outptr0 = output_buf[0][output_row];
 146     outptr1 = output_buf[1][output_row];
 147     outptr2 = output_buf[2][output_row];
 148     output_row++;
 149     for (col = 0; col < num_cols; col++) {
 150       r = GETJSAMPLE(inptr[RGB_RED]);
 151       g = GETJSAMPLE(inptr[RGB_GREEN]);
 152       b = GETJSAMPLE(inptr[RGB_BLUE]);
 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       inptr += RGB_PIXELSIZE;
 171     }
 172   }
 173 }
 174
 175
 176 /**************** Cases other than RGB -> YCbCr **************/
 177
 178
 179 /*
 180  * Convert some rows of samples to the JPEG colorspace.
 181  * This version handles RGB->grayscale conversion, which is the same
 182  * as the RGB->Y portion of RGB->YCbCr.
 183  * We assume rgb_ycc_start has been called (we only use the Y tables).
 184  */
 185
 186 METHODDEF(void)
 187 rgb_gray_convert (j_compress_ptr cinfo,
 188                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 189                   JDIMENSION output_row, int num_rows)
 190 {
 191   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 192   register INT32 * ctab = cconvert->rgb_ycc_tab;
 193   register int r, g, b;
 194   register JSAMPROW inptr;
 195   register JSAMPROW outptr;
 196   register JDIMENSION col;
 197   JDIMENSION num_cols = cinfo->image_width;
 198
 199   while (--num_rows >= 0) {
 200     inptr = *input_buf++;
 201     outptr = output_buf[0][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       /* Y */
 207       outptr[col] = (JSAMPLE)
 208                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 209                  >> SCALEBITS);
 210       inptr += RGB_PIXELSIZE;
 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)
 225 cmyk_ycck_convert (j_compress_ptr cinfo,
 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 INT32 * ctab = cconvert->rgb_ycc_tab;
 231   register int r, g, b;
 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       /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
 251        * must be too; we do not need an explicit range-limiting operation.
 252        * Hence the value being shifted is never negative, and we don't
 253        * need the general RIGHT_SHIFT macro.
 254        */
 255       /* Y */
 256       outptr0[col] = (JSAMPLE)
 257                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 258                  >> SCALEBITS);
 259       /* Cb */
 260       outptr1[col] = (JSAMPLE)
 261                 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
 262                  >> SCALEBITS);
 263       /* Cr */
 264       outptr2[col] = (JSAMPLE)
 265                 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
 266                  >> SCALEBITS);
 267       inptr += 4;
 268     }
 269   }
 270 }
 271
 272
 273 /*
 274  * Convert some rows of samples to the JPEG colorspace.
 275  * [R,G,B] to [R-G,G,B-G] conversion with modulo calculation
 276  * (forward reversible color transform).
 277  */
 278
 279 METHODDEF(void)
 280 rgb_rgb1_convert (j_compress_ptr cinfo,
 281                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 282                   JDIMENSION output_row, int num_rows)
 283 {
 284   register int r, g, b;
 285   register JSAMPROW inptr;
 286   register JSAMPROW outptr0, outptr1, outptr2;
 287   register JDIMENSION col;
 288   JDIMENSION num_cols = cinfo->image_width;
 289
 290   while (--num_rows >= 0) {
 291     inptr = *input_buf++;
 292     outptr0 = output_buf[0][output_row];
 293     outptr1 = output_buf[1][output_row];
 294     outptr2 = output_buf[2][output_row];
 295     output_row++;
 296     for (col = 0; col < num_cols; col++) {
 297       r = GETJSAMPLE(inptr[RGB_RED]);
 298       g = GETJSAMPLE(inptr[RGB_GREEN]);
 299       b = GETJSAMPLE(inptr[RGB_BLUE]);
 300       /* Assume that MAXJSAMPLE+1 is a power of 2, so that the MOD
 301        * (modulo) operator is equivalent to the bitmask operator AND.
 302        */
 303       outptr0[col] = (JSAMPLE) ((r - g + CENTERJSAMPLE) & MAXJSAMPLE);
 304       outptr1[col] = (JSAMPLE) g;
 305       outptr2[col] = (JSAMPLE) ((b - g + CENTERJSAMPLE) & MAXJSAMPLE);
 306       inptr += RGB_PIXELSIZE;
 307     }
 308   }
 309 }
 310
 311
 312 /*
 313  * Convert some rows of samples to the JPEG colorspace.
 314  * This version handles grayscale output with no conversion.
 315  * The source can be either plain grayscale or YCbCr (since Y == gray).
 316  */
 317
 318 METHODDEF(void)
 319 grayscale_convert (j_compress_ptr cinfo,
 320                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 321                    JDIMENSION output_row, int num_rows)
 322 {
 323   int instride = cinfo->input_components;
 324   register JSAMPROW inptr;
 325   register JSAMPROW outptr;
 326   register JDIMENSION col;
 327   JDIMENSION num_cols = cinfo->image_width;
 328
 329   while (--num_rows >= 0) {
 330     inptr = *input_buf++;
 331     outptr = output_buf[0][output_row++];
 332     for (col = 0; col < num_cols; col++) {
 333       outptr[col] = inptr[0];   /* don't need GETJSAMPLE() here */
 334       inptr += instride;
 335     }
 336   }
 337 }
 338
 339
 340 /*
 341  * Convert some rows of samples to the JPEG colorspace.
 342  * No colorspace conversion, but change from interleaved
 343  * to separate-planes representation.
 344  */
 345
 346 METHODDEF(void)
 347 rgb_convert (j_compress_ptr cinfo,
 348              JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 349              JDIMENSION output_row, int num_rows)
 350 {
 351   register JSAMPROW inptr;
 352   register JSAMPROW outptr0, outptr1, outptr2;
 353   register JDIMENSION col;
 354   JDIMENSION num_cols = cinfo->image_width;
 355
 356   while (--num_rows >= 0) {
 357     inptr = *input_buf++;
 358     outptr0 = output_buf[0][output_row];
 359     outptr1 = output_buf[1][output_row];
 360     outptr2 = output_buf[2][output_row];
 361     output_row++;
 362     for (col = 0; col < num_cols; col++) {
 363       /* We can dispense with GETJSAMPLE() here */
 364       outptr0[col] = inptr[RGB_RED];
 365       outptr1[col] = inptr[RGB_GREEN];
 366       outptr2[col] = inptr[RGB_BLUE];
 367       inptr += RGB_PIXELSIZE;
 368     }
 369   }
 370 }
 371
 372
 373 /*
 374  * Convert some rows of samples to the JPEG colorspace.
 375  * This version handles multi-component colorspaces without conversion.
 376  * We assume input_components == num_components.
 377  */
 378
 379 METHODDEF(void)
 380 null_convert (j_compress_ptr cinfo,
 381               JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 382               JDIMENSION output_row, int num_rows)
 383 {
 384   int ci;
 385   register int nc = cinfo->num_components;
 386   register JSAMPROW inptr;
 387   register JSAMPROW outptr;
 388   register JDIMENSION col;
 389   JDIMENSION num_cols = cinfo->image_width;
 390
 391   while (--num_rows >= 0) {
 392     /* It seems fastest to make a separate pass for each component. */
 393     for (ci = 0; ci < nc; ci++) {
 394       inptr = input_buf[0] + ci;
 395       outptr = output_buf[ci][output_row];
 396       for (col = 0; col < num_cols; col++) {
 397         *outptr++ = *inptr;     /* don't need GETJSAMPLE() here */
 398         inptr += nc;
 399       }
 400     }
 401     input_buf++;
 402     output_row++;
 403   }
 404 }
 405
 406
 407 /*
 408  * Empty method for start_pass.
 409  */
 410
 411 METHODDEF(void)
 412 null_method (j_compress_ptr cinfo)
 413 {
 414   /* no work needed */
 415 }
 416
 417
 418 /*
 419  * Module initialization routine for input colorspace conversion.
 420  */
 421
 422 GLOBAL(void)
 423 jinit_color_converter (j_compress_ptr cinfo)
 424 {
 425   my_cconvert_ptr cconvert;
 426
 427   cconvert = (my_cconvert_ptr)
 428     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 429                                 SIZEOF(my_color_converter));
 430   cinfo->cconvert = &cconvert->pub;
 431   /* set start_pass to null method until we find out differently */
 432   cconvert->pub.start_pass = null_method;
 433
 434   /* Make sure input_components agrees with in_color_space */
 435   switch (cinfo->in_color_space) {
 436   case JCS_GRAYSCALE:
 437     if (cinfo->input_components != 1)
 438       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 439     break;
 440
 441   case JCS_RGB:
 442     if (cinfo->input_components != RGB_PIXELSIZE)
 443       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 444     break;
 445
 446   case JCS_YCbCr:
 447     if (cinfo->input_components != 3)
 448       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 449     break;
 450
 451   case JCS_CMYK:
 452   case JCS_YCCK:
 453     if (cinfo->input_components != 4)
 454       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 455     break;
 456
 457   default:                      /* JCS_UNKNOWN can be anything */
 458     if (cinfo->input_components < 1)
 459       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 460     break;
 461   }
 462
 463   /* Support color transform only for RGB colorspace */
 464   if (cinfo->color_transform && cinfo->jpeg_color_space != JCS_RGB)
 465     ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 466
 467   /* Check num_components, set conversion method based on requested space */
 468   switch (cinfo->jpeg_color_space) {
 469   case JCS_GRAYSCALE:
 470     if (cinfo->num_components != 1)
 471       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 472     if (cinfo->in_color_space == JCS_GRAYSCALE ||
 473         cinfo->in_color_space == JCS_YCbCr)
 474       cconvert->pub.color_convert = grayscale_convert;
 475     else if (cinfo->in_color_space == JCS_RGB) {
 476       cconvert->pub.start_pass = rgb_ycc_start;
 477       cconvert->pub.color_convert = rgb_gray_convert;
 478     } else
 479       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 480     break;
 481
 482   case JCS_RGB:
 483     if (cinfo->num_components != 3)
 484       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 485     if (cinfo->in_color_space == JCS_RGB) {
 486       switch (cinfo->color_transform) {
 487       case JCT_NONE:
 488         cconvert->pub.color_convert = rgb_convert;
 489         break;
 490       case JCT_SUBTRACT_GREEN:
 491         cconvert->pub.color_convert = rgb_rgb1_convert;
 492         break;
 493       default:
 494         ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 495         break;
 496       }
 497     } else
 498       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 499     break;
 500
 501   case JCS_YCbCr:
 502     if (cinfo->num_components != 3)
 503       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 504     if (cinfo->in_color_space == JCS_RGB) {
 505       cconvert->pub.start_pass = rgb_ycc_start;
 506       cconvert->pub.color_convert = rgb_ycc_convert;
 507     } else if (cinfo->in_color_space == JCS_YCbCr)
 508       cconvert->pub.color_convert = null_convert;
 509     else
 510       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 511     break;
 512
 513   case JCS_CMYK:
 514     if (cinfo->num_components != 4)
 515       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 516     if (cinfo->in_color_space == JCS_CMYK)
 517       cconvert->pub.color_convert = null_convert;
 518     else
 519       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 520     break;
 521
 522   case JCS_YCCK:
 523     if (cinfo->num_components != 4)
 524       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 525     if (cinfo->in_color_space == JCS_CMYK) {
 526       cconvert->pub.start_pass = rgb_ycc_start;
 527       cconvert->pub.color_convert = cmyk_ycck_convert;
 528     } else if (cinfo->in_color_space == JCS_YCCK)
 529       cconvert->pub.color_convert = null_convert;
 530     else
 531       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 532     break;
 533
 534   default:                      /* allow null conversion of JCS_UNKNOWN */
 535     if (cinfo->jpeg_color_space != cinfo->in_color_space ||
 536         cinfo->num_components != cinfo->input_components)
 537       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 538     cconvert->pub.color_convert = null_convert;
 539     break;
 540   }
 541 }