workbench/libs/jpeg/jccolor.c

   1 /*
   2  * jccolor.c
   3  *
   4  * Copyright (C) 1991-1996, Thomas G. Lane.
   5  * Modified 2011 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 int r, g, b;
 137   register INT32 * ctab = cconvert->rgb_ycc_tab;
 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       inptr += RGB_PIXELSIZE;
 154       /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
 155        * must be too; we do not need an explicit range-limiting operation.
 156        * Hence the value being shifted is never negative, and we don't
 157        * need the general RIGHT_SHIFT macro.
 158        */
 159       /* Y */
 160       outptr0[col] = (JSAMPLE)
 161                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 162                  >> SCALEBITS);
 163       /* Cb */
 164       outptr1[col] = (JSAMPLE)
 165                 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
 166                  >> SCALEBITS);
 167       /* Cr */
 168       outptr2[col] = (JSAMPLE)
 169                 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
 170                  >> SCALEBITS);
 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 int r, g, b;
 193   register INT32 * ctab = cconvert->rgb_ycc_tab;
 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     output_row++;
 203     for (col = 0; col < num_cols; col++) {
 204       r = GETJSAMPLE(inptr[RGB_RED]);
 205       g = GETJSAMPLE(inptr[RGB_GREEN]);
 206       b = GETJSAMPLE(inptr[RGB_BLUE]);
 207       inptr += RGB_PIXELSIZE;
 208       /* Y */
 209       outptr[col] = (JSAMPLE)
 210                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 211                  >> SCALEBITS);
 212     }
 213   }
 214 }
 215
 216
 217 /*
 218  * Convert some rows of samples to the JPEG colorspace.
 219  * This version handles Adobe-style CMYK->YCCK conversion,
 220  * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 221  * conversion as above, while passing K (black) unchanged.
 222  * We assume rgb_ycc_start has been called.
 223  */
 224
 225 METHODDEF(void)
 226 cmyk_ycck_convert (j_compress_ptr cinfo,
 227                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 228                    JDIMENSION output_row, int num_rows)
 229 {
 230   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 231   register int r, g, b;
 232   register INT32 * ctab = cconvert->rgb_ycc_tab;
 233   register JSAMPROW inptr;
 234   register JSAMPROW outptr0, outptr1, outptr2, outptr3;
 235   register JDIMENSION col;
 236   JDIMENSION num_cols = cinfo->image_width;
 237
 238   while (--num_rows >= 0) {
 239     inptr = *input_buf++;
 240     outptr0 = output_buf[0][output_row];
 241     outptr1 = output_buf[1][output_row];
 242     outptr2 = output_buf[2][output_row];
 243     outptr3 = output_buf[3][output_row];
 244     output_row++;
 245     for (col = 0; col < num_cols; col++) {
 246       r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
 247       g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
 248       b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
 249       /* K passes through as-is */
 250       outptr3[col] = inptr[3];  /* don't need GETJSAMPLE here */
 251       inptr += 4;
 252       /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
 253        * must be too; we do not need an explicit range-limiting operation.
 254        * Hence the value being shifted is never negative, and we don't
 255        * need the general RIGHT_SHIFT macro.
 256        */
 257       /* Y */
 258       outptr0[col] = (JSAMPLE)
 259                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 260                  >> SCALEBITS);
 261       /* Cb */
 262       outptr1[col] = (JSAMPLE)
 263                 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
 264                  >> SCALEBITS);
 265       /* Cr */
 266       outptr2[col] = (JSAMPLE)
 267                 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
 268                  >> SCALEBITS);
 269     }
 270   }
 271 }
 272
 273
 274 /*
 275  * Convert some rows of samples to the JPEG colorspace.
 276  * This version handles grayscale output with no conversion.
 277  * The source can be either plain grayscale or YCbCr (since Y == gray).
 278  */
 279
 280 METHODDEF(void)
 281 grayscale_convert (j_compress_ptr cinfo,
 282                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 283                    JDIMENSION output_row, int num_rows)
 284 {
 285   register JSAMPROW inptr;
 286   register JSAMPROW outptr;
 287   register JDIMENSION col;
 288   JDIMENSION num_cols = cinfo->image_width;
 289   int instride = cinfo->input_components;
 290
 291   while (--num_rows >= 0) {
 292     inptr = *input_buf++;
 293     outptr = output_buf[0][output_row];
 294     output_row++;
 295     for (col = 0; col < num_cols; col++) {
 296       outptr[col] = inptr[0];   /* don't need GETJSAMPLE() here */
 297       inptr += instride;
 298     }
 299   }
 300 }
 301
 302
 303 /*
 304  * Convert some rows of samples to the JPEG colorspace.
 305  * No colorspace conversion, but change from interleaved
 306  * to separate-planes representation.
 307  */
 308
 309 METHODDEF(void)
 310 rgb_convert (j_compress_ptr cinfo,
 311              JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 312              JDIMENSION output_row, int num_rows)
 313 {
 314   register JSAMPROW inptr;
 315   register JSAMPROW outptr0, outptr1, outptr2;
 316   register JDIMENSION col;
 317   JDIMENSION num_cols = cinfo->image_width;
 318
 319   while (--num_rows >= 0) {
 320     inptr = *input_buf++;
 321     outptr0 = output_buf[0][output_row];
 322     outptr1 = output_buf[1][output_row];
 323     outptr2 = output_buf[2][output_row];
 324     output_row++;
 325     for (col = 0; col < num_cols; col++) {
 326       /* We can dispense with GETJSAMPLE() here */
 327       outptr0[col] = inptr[RGB_RED];
 328       outptr1[col] = inptr[RGB_GREEN];
 329       outptr2[col] = inptr[RGB_BLUE];
 330       inptr += RGB_PIXELSIZE;
 331     }
 332   }
 333 }
 334
 335
 336 /*
 337  * Convert some rows of samples to the JPEG colorspace.
 338  * This version handles multi-component colorspaces without conversion.
 339  * We assume input_components == num_components.
 340  */
 341
 342 METHODDEF(void)
 343 null_convert (j_compress_ptr cinfo,
 344               JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 345               JDIMENSION output_row, int num_rows)
 346 {
 347   register JSAMPROW inptr;
 348   register JSAMPROW outptr;
 349   register JDIMENSION col;
 350   register int ci;
 351   int nc = cinfo->num_components;
 352   JDIMENSION num_cols = cinfo->image_width;
 353
 354   while (--num_rows >= 0) {
 355     /* It seems fastest to make a separate pass for each component. */
 356     for (ci = 0; ci < nc; ci++) {
 357       inptr = *input_buf;
 358       outptr = output_buf[ci][output_row];
 359       for (col = 0; col < num_cols; col++) {
 360         outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
 361         inptr += nc;
 362       }
 363     }
 364     input_buf++;
 365     output_row++;
 366   }
 367 }
 368
 369
 370 /*
 371  * Empty method for start_pass.
 372  */
 373
 374 METHODDEF(void)
 375 null_method (j_compress_ptr cinfo)
 376 {
 377   /* no work needed */
 378 }
 379
 380
 381 /*
 382  * Module initialization routine for input colorspace conversion.
 383  */
 384
 385 GLOBAL(void)
 386 jinit_color_converter (j_compress_ptr cinfo)
 387 {
 388   my_cconvert_ptr cconvert;
 389
 390   cconvert = (my_cconvert_ptr)
 391     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 392                                 SIZEOF(my_color_converter));
 393   cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
 394   /* set start_pass to null method until we find out differently */
 395   cconvert->pub.start_pass = null_method;
 396
 397   /* Make sure input_components agrees with in_color_space */
 398   switch (cinfo->in_color_space) {
 399   case JCS_GRAYSCALE:
 400     if (cinfo->input_components != 1)
 401       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 402     break;
 403
 404   case JCS_RGB:
 405     if (cinfo->input_components != RGB_PIXELSIZE)
 406       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 407     break;
 408
 409   case JCS_YCbCr:
 410     if (cinfo->input_components != 3)
 411       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 412     break;
 413
 414   case JCS_CMYK:
 415   case JCS_YCCK:
 416     if (cinfo->input_components != 4)
 417       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 418     break;
 419
 420   default:                      /* JCS_UNKNOWN can be anything */
 421     if (cinfo->input_components < 1)
 422       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 423     break;
 424   }
 425
 426   /* Check num_components, set conversion method based on requested space */
 427   switch (cinfo->jpeg_color_space) {
 428   case JCS_GRAYSCALE:
 429     if (cinfo->num_components != 1)
 430       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 431     if (cinfo->in_color_space == JCS_GRAYSCALE ||
 432         cinfo->in_color_space == JCS_YCbCr)
 433       cconvert->pub.color_convert = grayscale_convert;
 434     else if (cinfo->in_color_space == JCS_RGB) {
 435       cconvert->pub.start_pass = rgb_ycc_start;
 436       cconvert->pub.color_convert = rgb_gray_convert;
 437     } else
 438       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 439     break;
 440
 441   case JCS_RGB:
 442     if (cinfo->num_components != 3)
 443       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 444     if (cinfo->in_color_space == JCS_RGB)
 445       cconvert->pub.color_convert = rgb_convert;
 446     else
 447       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 448     break;
 449
 450   case JCS_YCbCr:
 451     if (cinfo->num_components != 3)
 452       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 453     if (cinfo->in_color_space == JCS_RGB) {
 454       cconvert->pub.start_pass = rgb_ycc_start;
 455       cconvert->pub.color_convert = rgb_ycc_convert;
 456     } else if (cinfo->in_color_space == JCS_YCbCr)
 457       cconvert->pub.color_convert = null_convert;
 458     else
 459       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 460     break;
 461
 462   case JCS_CMYK:
 463     if (cinfo->num_components != 4)
 464       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 465     if (cinfo->in_color_space == JCS_CMYK)
 466       cconvert->pub.color_convert = null_convert;
 467     else
 468       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 469     break;
 470
 471   case JCS_YCCK:
 472     if (cinfo->num_components != 4)
 473       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 474     if (cinfo->in_color_space == JCS_CMYK) {
 475       cconvert->pub.start_pass = rgb_ycc_start;
 476       cconvert->pub.color_convert = cmyk_ycck_convert;
 477     } else if (cinfo->in_color_space == JCS_YCCK)
 478       cconvert->pub.color_convert = null_convert;
 479     else
 480       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 481     break;
 482
 483   default:                      /* allow null conversion of JCS_UNKNOWN */
 484     if (cinfo->jpeg_color_space != cinfo->in_color_space ||
 485         cinfo->num_components != cinfo->input_components)
 486       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 487     cconvert->pub.color_convert = null_convert;
 488     break;
 489   }
 490 }