media/libjpeg/jccolor.c

   1 /*
   2  * jccolor.c
   3  *
   4  * This file was part of the Independent JPEG Group's software:
   5  * Copyright (C) 1991-1996, Thomas G. Lane.
   6  * libjpeg-turbo Modifications:
   7  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
   8  * Copyright (C) 2009-2012, 2015, 2022, D. R. Commander.
   9  * Copyright (C) 2014, MIPS Technologies, Inc., California.
  10  * For conditions of distribution and use, see the accompanying README.ijg
  11  * file.
  12  *
  13  * This file contains input colorspace conversion routines.
  14  */
  15
  16 #define JPEG_INTERNALS
  17 #include "jinclude.h"
  18 #include "jpeglib.h"
  19 #include "jsimd.h"
  20
  21
  22 /* Private subobject */
  23
  24 typedef struct {
  25   struct jpeg_color_converter pub; /* public fields */
  26
  27   /* Private state for RGB->YCC conversion */
  28   JLONG *rgb_ycc_tab;           /* => table for RGB to YCbCr conversion */
  29 } my_color_converter;
  30
  31 typedef my_color_converter *my_cconvert_ptr;
  32
  33
  34 /**************** RGB -> YCbCr conversion: most common case **************/
  35
  36 /*
  37  * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
  38  * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
  39  * The conversion equations to be implemented are therefore
  40  *      Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
  41  *      Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE
  42  *      Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
  43  * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
  44  * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
  45  * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
  46  * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
  47  * were not represented exactly.  Now we sacrifice exact representation of
  48  * maximum red and maximum blue in order to get exact grayscales.
  49  *
  50  * To avoid floating-point arithmetic, we represent the fractional constants
  51  * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
  52  * the products by 2^16, with appropriate rounding, to get the correct answer.
  53  *
  54  * For even more speed, we avoid doing any multiplications in the inner loop
  55  * by precalculating the constants times R,G,B for all possible values.
  56  * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
  57  * for 12-bit samples it is still acceptable.  It's not very reasonable for
  58  * 16-bit samples, but if you want lossless storage you shouldn't be changing
  59  * colorspace anyway.
  60  * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
  61  * in the tables to save adding them separately in the inner loop.
  62  */
  63
  64 #define SCALEBITS       16      /* speediest right-shift on some machines */
  65 #define CBCR_OFFSET     ((JLONG)CENTERJSAMPLE << SCALEBITS)
  66 #define ONE_HALF        ((JLONG)1 << (SCALEBITS - 1))
  67 #define FIX(x)          ((JLONG)((x) * (1L << SCALEBITS) + 0.5))
  68
  69 /* We allocate one big table and divide it up into eight parts, instead of
  70  * doing eight alloc_small requests.  This lets us use a single table base
  71  * address, which can be held in a register in the inner loops on many
  72  * machines (more than can hold all eight addresses, anyway).
  73  */
  74
  75 #define R_Y_OFF         0                       /* offset to R => Y section */
  76 #define G_Y_OFF         (1 * (MAXJSAMPLE + 1))  /* offset to G => Y section */
  77 #define B_Y_OFF         (2 * (MAXJSAMPLE + 1))  /* etc. */
  78 #define R_CB_OFF        (3 * (MAXJSAMPLE + 1))
  79 #define G_CB_OFF        (4 * (MAXJSAMPLE + 1))
  80 #define B_CB_OFF        (5 * (MAXJSAMPLE + 1))
  81 #define R_CR_OFF        B_CB_OFF                /* B=>Cb, R=>Cr are the same */
  82 #define G_CR_OFF        (6 * (MAXJSAMPLE + 1))
  83 #define B_CR_OFF        (7 * (MAXJSAMPLE + 1))
  84 #define TABLE_SIZE      (8 * (MAXJSAMPLE + 1))
  85
  86 /* 12-bit samples use a 16-bit data type, so it is possible to pass
  87  * out-of-range sample values (< 0 or > 4095) to jpeg_write_scanlines().
  88  * Thus, we mask the incoming 12-bit samples to guard against overrunning
  89  * or underrunning the conversion tables.
  90  */
  91
  92 #if BITS_IN_JSAMPLE == 12
  93 #define RANGE_LIMIT(value)  ((value) & 0xFFF)
  94 #else
  95 #define RANGE_LIMIT(value)  (value)
  96 #endif
  97
  98
  99 /* Include inline routines for colorspace extensions */
 100
 101 #include "jccolext.c"
 102 #undef RGB_RED
 103 #undef RGB_GREEN
 104 #undef RGB_BLUE
 105 #undef RGB_PIXELSIZE
 106
 107 #define RGB_RED  EXT_RGB_RED
 108 #define RGB_GREEN  EXT_RGB_GREEN
 109 #define RGB_BLUE  EXT_RGB_BLUE
 110 #define RGB_PIXELSIZE  EXT_RGB_PIXELSIZE
 111 #define rgb_ycc_convert_internal  extrgb_ycc_convert_internal
 112 #define rgb_gray_convert_internal  extrgb_gray_convert_internal
 113 #define rgb_rgb_convert_internal  extrgb_rgb_convert_internal
 114 #include "jccolext.c"
 115 #undef RGB_RED
 116 #undef RGB_GREEN
 117 #undef RGB_BLUE
 118 #undef RGB_PIXELSIZE
 119 #undef rgb_ycc_convert_internal
 120 #undef rgb_gray_convert_internal
 121 #undef rgb_rgb_convert_internal
 122
 123 #define RGB_RED  EXT_RGBX_RED
 124 #define RGB_GREEN  EXT_RGBX_GREEN
 125 #define RGB_BLUE  EXT_RGBX_BLUE
 126 #define RGB_PIXELSIZE  EXT_RGBX_PIXELSIZE
 127 #define rgb_ycc_convert_internal  extrgbx_ycc_convert_internal
 128 #define rgb_gray_convert_internal  extrgbx_gray_convert_internal
 129 #define rgb_rgb_convert_internal  extrgbx_rgb_convert_internal
 130 #include "jccolext.c"
 131 #undef RGB_RED
 132 #undef RGB_GREEN
 133 #undef RGB_BLUE
 134 #undef RGB_PIXELSIZE
 135 #undef rgb_ycc_convert_internal
 136 #undef rgb_gray_convert_internal
 137 #undef rgb_rgb_convert_internal
 138
 139 #define RGB_RED  EXT_BGR_RED
 140 #define RGB_GREEN  EXT_BGR_GREEN
 141 #define RGB_BLUE  EXT_BGR_BLUE
 142 #define RGB_PIXELSIZE  EXT_BGR_PIXELSIZE
 143 #define rgb_ycc_convert_internal  extbgr_ycc_convert_internal
 144 #define rgb_gray_convert_internal  extbgr_gray_convert_internal
 145 #define rgb_rgb_convert_internal  extbgr_rgb_convert_internal
 146 #include "jccolext.c"
 147 #undef RGB_RED
 148 #undef RGB_GREEN
 149 #undef RGB_BLUE
 150 #undef RGB_PIXELSIZE
 151 #undef rgb_ycc_convert_internal
 152 #undef rgb_gray_convert_internal
 153 #undef rgb_rgb_convert_internal
 154
 155 #define RGB_RED  EXT_BGRX_RED
 156 #define RGB_GREEN  EXT_BGRX_GREEN
 157 #define RGB_BLUE  EXT_BGRX_BLUE
 158 #define RGB_PIXELSIZE  EXT_BGRX_PIXELSIZE
 159 #define rgb_ycc_convert_internal  extbgrx_ycc_convert_internal
 160 #define rgb_gray_convert_internal  extbgrx_gray_convert_internal
 161 #define rgb_rgb_convert_internal  extbgrx_rgb_convert_internal
 162 #include "jccolext.c"
 163 #undef RGB_RED
 164 #undef RGB_GREEN
 165 #undef RGB_BLUE
 166 #undef RGB_PIXELSIZE
 167 #undef rgb_ycc_convert_internal
 168 #undef rgb_gray_convert_internal
 169 #undef rgb_rgb_convert_internal
 170
 171 #define RGB_RED  EXT_XBGR_RED
 172 #define RGB_GREEN  EXT_XBGR_GREEN
 173 #define RGB_BLUE  EXT_XBGR_BLUE
 174 #define RGB_PIXELSIZE  EXT_XBGR_PIXELSIZE
 175 #define rgb_ycc_convert_internal  extxbgr_ycc_convert_internal
 176 #define rgb_gray_convert_internal  extxbgr_gray_convert_internal
 177 #define rgb_rgb_convert_internal  extxbgr_rgb_convert_internal
 178 #include "jccolext.c"
 179 #undef RGB_RED
 180 #undef RGB_GREEN
 181 #undef RGB_BLUE
 182 #undef RGB_PIXELSIZE
 183 #undef rgb_ycc_convert_internal
 184 #undef rgb_gray_convert_internal
 185 #undef rgb_rgb_convert_internal
 186
 187 #define RGB_RED  EXT_XRGB_RED
 188 #define RGB_GREEN  EXT_XRGB_GREEN
 189 #define RGB_BLUE  EXT_XRGB_BLUE
 190 #define RGB_PIXELSIZE  EXT_XRGB_PIXELSIZE
 191 #define rgb_ycc_convert_internal  extxrgb_ycc_convert_internal
 192 #define rgb_gray_convert_internal  extxrgb_gray_convert_internal
 193 #define rgb_rgb_convert_internal  extxrgb_rgb_convert_internal
 194 #include "jccolext.c"
 195 #undef RGB_RED
 196 #undef RGB_GREEN
 197 #undef RGB_BLUE
 198 #undef RGB_PIXELSIZE
 199 #undef rgb_ycc_convert_internal
 200 #undef rgb_gray_convert_internal
 201 #undef rgb_rgb_convert_internal
 202
 203
 204 /*
 205  * Initialize for RGB->YCC colorspace conversion.
 206  */
 207
 208 METHODDEF(void)
 209 rgb_ycc_start(j_compress_ptr cinfo)
 210 {
 211   my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;
 212   JLONG *rgb_ycc_tab;
 213   JLONG i;
 214
 215   /* Allocate and fill in the conversion tables. */
 216   cconvert->rgb_ycc_tab = rgb_ycc_tab = (JLONG *)
 217     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 218                                 (TABLE_SIZE * sizeof(JLONG)));
 219
 220   for (i = 0; i <= MAXJSAMPLE; i++) {
 221     rgb_ycc_tab[i + R_Y_OFF] = FIX(0.29900) * i;
 222     rgb_ycc_tab[i + G_Y_OFF] = FIX(0.58700) * i;
 223     rgb_ycc_tab[i + B_Y_OFF] = FIX(0.11400) * i   + ONE_HALF;
 224     rgb_ycc_tab[i + R_CB_OFF] = (-FIX(0.16874)) * i;
 225     rgb_ycc_tab[i + G_CB_OFF] = (-FIX(0.33126)) * i;
 226     /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
 227      * This ensures that the maximum output will round to MAXJSAMPLE
 228      * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
 229      */
 230     rgb_ycc_tab[i + B_CB_OFF] = FIX(0.50000) * i  + CBCR_OFFSET + ONE_HALF - 1;
 231 /*  B=>Cb and R=>Cr tables are the same
 232     rgb_ycc_tab[i + R_CR_OFF] = FIX(0.50000) * i  + CBCR_OFFSET + ONE_HALF - 1;
 233 */
 234     rgb_ycc_tab[i + G_CR_OFF] = (-FIX(0.41869)) * i;
 235     rgb_ycc_tab[i + B_CR_OFF] = (-FIX(0.08131)) * i;
 236   }
 237 }
 238
 239
 240 /*
 241  * Convert some rows of samples to the JPEG colorspace.
 242  */
 243
 244 METHODDEF(void)
 245 rgb_ycc_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,
 246                 JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
 247 {
 248   switch (cinfo->in_color_space) {
 249   case JCS_EXT_RGB:
 250     extrgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 251                                 num_rows);
 252     break;
 253   case JCS_EXT_RGBX:
 254   case JCS_EXT_RGBA:
 255     extrgbx_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 256                                  num_rows);
 257     break;
 258   case JCS_EXT_BGR:
 259     extbgr_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 260                                 num_rows);
 261     break;
 262   case JCS_EXT_BGRX:
 263   case JCS_EXT_BGRA:
 264     extbgrx_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 265                                  num_rows);
 266     break;
 267   case JCS_EXT_XBGR:
 268   case JCS_EXT_ABGR:
 269     extxbgr_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 270                                  num_rows);
 271     break;
 272   case JCS_EXT_XRGB:
 273   case JCS_EXT_ARGB:
 274     extxrgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 275                                  num_rows);
 276     break;
 277   default:
 278     rgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 279                              num_rows);
 280     break;
 281   }
 282 }
 283
 284
 285 /**************** Cases other than RGB -> YCbCr **************/
 286
 287
 288 /*
 289  * Convert some rows of samples to the JPEG colorspace.
 290  */
 291
 292 METHODDEF(void)
 293 rgb_gray_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,
 294                  JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
 295 {
 296   switch (cinfo->in_color_space) {
 297   case JCS_EXT_RGB:
 298     extrgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 299                                  num_rows);
 300     break;
 301   case JCS_EXT_RGBX:
 302   case JCS_EXT_RGBA:
 303     extrgbx_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 304                                   num_rows);
 305     break;
 306   case JCS_EXT_BGR:
 307     extbgr_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 308                                  num_rows);
 309     break;
 310   case JCS_EXT_BGRX:
 311   case JCS_EXT_BGRA:
 312     extbgrx_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 313                                   num_rows);
 314     break;
 315   case JCS_EXT_XBGR:
 316   case JCS_EXT_ABGR:
 317     extxbgr_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 318                                   num_rows);
 319     break;
 320   case JCS_EXT_XRGB:
 321   case JCS_EXT_ARGB:
 322     extxrgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 323                                   num_rows);
 324     break;
 325   default:
 326     rgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 327                               num_rows);
 328     break;
 329   }
 330 }
 331
 332
 333 /*
 334  * Extended RGB to plain RGB conversion
 335  */
 336
 337 METHODDEF(void)
 338 rgb_rgb_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,
 339                 JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
 340 {
 341   switch (cinfo->in_color_space) {
 342   case JCS_EXT_RGB:
 343     extrgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 344                                 num_rows);
 345     break;
 346   case JCS_EXT_RGBX:
 347   case JCS_EXT_RGBA:
 348     extrgbx_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 349                                  num_rows);
 350     break;
 351   case JCS_EXT_BGR:
 352     extbgr_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 353                                 num_rows);
 354     break;
 355   case JCS_EXT_BGRX:
 356   case JCS_EXT_BGRA:
 357     extbgrx_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 358                                  num_rows);
 359     break;
 360   case JCS_EXT_XBGR:
 361   case JCS_EXT_ABGR:
 362     extxbgr_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 363                                  num_rows);
 364     break;
 365   case JCS_EXT_XRGB:
 366   case JCS_EXT_ARGB:
 367     extxrgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 368                                  num_rows);
 369     break;
 370   default:
 371     rgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 372                              num_rows);
 373     break;
 374   }
 375 }
 376
 377
 378 /*
 379  * Convert some rows of samples to the JPEG colorspace.
 380  * This version handles Adobe-style CMYK->YCCK conversion,
 381  * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 382  * conversion as above, while passing K (black) unchanged.
 383  * We assume rgb_ycc_start has been called.
 384  */
 385
 386 METHODDEF(void)
 387 cmyk_ycck_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,
 388                   JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
 389 {
 390   my_cconvert_ptr cconvert = (my_cconvert_ptr)cinfo->cconvert;
 391   register int r, g, b;
 392   register JLONG *ctab = cconvert->rgb_ycc_tab;
 393   register JSAMPROW inptr;
 394   register JSAMPROW outptr0, outptr1, outptr2, outptr3;
 395   register JDIMENSION col;
 396   JDIMENSION num_cols = cinfo->image_width;
 397
 398   while (--num_rows >= 0) {
 399     inptr = *input_buf++;
 400     outptr0 = output_buf[0][output_row];
 401     outptr1 = output_buf[1][output_row];
 402     outptr2 = output_buf[2][output_row];
 403     outptr3 = output_buf[3][output_row];
 404     output_row++;
 405     for (col = 0; col < num_cols; col++) {
 406       r = MAXJSAMPLE - RANGE_LIMIT(inptr[0]);
 407       g = MAXJSAMPLE - RANGE_LIMIT(inptr[1]);
 408       b = MAXJSAMPLE - RANGE_LIMIT(inptr[2]);
 409       /* K passes through as-is */
 410       outptr3[col] = inptr[3];
 411       inptr += 4;
 412       /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
 413        * must be too; we do not need an explicit range-limiting operation.
 414        * Hence the value being shifted is never negative, and we don't
 415        * need the general RIGHT_SHIFT macro.
 416        */
 417       /* Y */
 418       outptr0[col] = (JSAMPLE)((ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] +
 419                                 ctab[b + B_Y_OFF]) >> SCALEBITS);
 420       /* Cb */
 421       outptr1[col] = (JSAMPLE)((ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] +
 422                                 ctab[b + B_CB_OFF]) >> SCALEBITS);
 423       /* Cr */
 424       outptr2[col] = (JSAMPLE)((ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] +
 425                                 ctab[b + B_CR_OFF]) >> SCALEBITS);
 426     }
 427   }
 428 }
 429
 430
 431 /*
 432  * Convert some rows of samples to the JPEG colorspace.
 433  * This version handles grayscale output with no conversion.
 434  * The source can be either plain grayscale or YCbCr (since Y == gray).
 435  */
 436
 437 METHODDEF(void)
 438 grayscale_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf,
 439                   JSAMPIMAGE output_buf, JDIMENSION output_row, int num_rows)
 440 {
 441   register JSAMPROW inptr;
 442   register JSAMPROW outptr;
 443   register JDIMENSION col;
 444   JDIMENSION num_cols = cinfo->image_width;
 445   int instride = cinfo->input_components;
 446
 447   while (--num_rows >= 0) {
 448     inptr = *input_buf++;
 449     outptr = output_buf[0][output_row];
 450     output_row++;
 451     for (col = 0; col < num_cols; col++) {
 452       outptr[col] = inptr[0];
 453       inptr += instride;
 454     }
 455   }
 456 }
 457
 458
 459 /*
 460  * Convert some rows of samples to the JPEG colorspace.
 461  * This version handles multi-component colorspaces without conversion.
 462  * We assume input_components == num_components.
 463  */
 464
 465 METHODDEF(void)
 466 null_convert(j_compress_ptr cinfo, JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 467              JDIMENSION output_row, int num_rows)
 468 {
 469   register JSAMPROW inptr;
 470   register JSAMPROW outptr, outptr0, outptr1, outptr2, outptr3;
 471   register JDIMENSION col;
 472   register int ci;
 473   int nc = cinfo->num_components;
 474   JDIMENSION num_cols = cinfo->image_width;
 475
 476   if (nc == 3) {
 477     while (--num_rows >= 0) {
 478       inptr = *input_buf++;
 479       outptr0 = output_buf[0][output_row];
 480       outptr1 = output_buf[1][output_row];
 481       outptr2 = output_buf[2][output_row];
 482       output_row++;
 483       for (col = 0; col < num_cols; col++) {
 484         outptr0[col] = *inptr++;
 485         outptr1[col] = *inptr++;
 486         outptr2[col] = *inptr++;
 487       }
 488     }
 489   } else if (nc == 4) {
 490     while (--num_rows >= 0) {
 491       inptr = *input_buf++;
 492       outptr0 = output_buf[0][output_row];
 493       outptr1 = output_buf[1][output_row];
 494       outptr2 = output_buf[2][output_row];
 495       outptr3 = output_buf[3][output_row];
 496       output_row++;
 497       for (col = 0; col < num_cols; col++) {
 498         outptr0[col] = *inptr++;
 499         outptr1[col] = *inptr++;
 500         outptr2[col] = *inptr++;
 501         outptr3[col] = *inptr++;
 502       }
 503     }
 504   } else {
 505     while (--num_rows >= 0) {
 506       /* It seems fastest to make a separate pass for each component. */
 507       for (ci = 0; ci < nc; ci++) {
 508         inptr = *input_buf;
 509         outptr = output_buf[ci][output_row];
 510         for (col = 0; col < num_cols; col++) {
 511           outptr[col] = inptr[ci];
 512           inptr += nc;
 513         }
 514       }
 515       input_buf++;
 516       output_row++;
 517     }
 518   }
 519 }
 520
 521
 522 /*
 523  * Empty method for start_pass.
 524  */
 525
 526 METHODDEF(void)
 527 null_method(j_compress_ptr cinfo)
 528 {
 529   /* no work needed */
 530 }
 531
 532
 533 /*
 534  * Module initialization routine for input colorspace conversion.
 535  */
 536
 537 GLOBAL(void)
 538 jinit_color_converter(j_compress_ptr cinfo)
 539 {
 540   my_cconvert_ptr cconvert;
 541
 542   cconvert = (my_cconvert_ptr)
 543     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 544                                 sizeof(my_color_converter));
 545   cinfo->cconvert = (struct jpeg_color_converter *)cconvert;
 546   /* set start_pass to null method until we find out differently */
 547   cconvert->pub.start_pass = null_method;
 548
 549   /* Make sure input_components agrees with in_color_space */
 550   switch (cinfo->in_color_space) {
 551   case JCS_GRAYSCALE:
 552     if (cinfo->input_components != 1)
 553       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 554     break;
 555
 556   case JCS_RGB:
 557   case JCS_EXT_RGB:
 558   case JCS_EXT_RGBX:
 559   case JCS_EXT_BGR:
 560   case JCS_EXT_BGRX:
 561   case JCS_EXT_XBGR:
 562   case JCS_EXT_XRGB:
 563   case JCS_EXT_RGBA:
 564   case JCS_EXT_BGRA:
 565   case JCS_EXT_ABGR:
 566   case JCS_EXT_ARGB:
 567     if (cinfo->input_components != rgb_pixelsize[cinfo->in_color_space])
 568       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 569     break;
 570
 571   case JCS_YCbCr:
 572     if (cinfo->input_components != 3)
 573       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 574     break;
 575
 576   case JCS_CMYK:
 577   case JCS_YCCK:
 578     if (cinfo->input_components != 4)
 579       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 580     break;
 581
 582   default:                      /* JCS_UNKNOWN can be anything */
 583     if (cinfo->input_components < 1)
 584       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 585     break;
 586   }
 587
 588   /* Check num_components, set conversion method based on requested space */
 589   switch (cinfo->jpeg_color_space) {
 590   case JCS_GRAYSCALE:
 591     if (cinfo->num_components != 1)
 592       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 593     if (cinfo->in_color_space == JCS_GRAYSCALE)
 594       cconvert->pub.color_convert = grayscale_convert;
 595     else if (cinfo->in_color_space == JCS_RGB ||
 596              cinfo->in_color_space == JCS_EXT_RGB ||
 597              cinfo->in_color_space == JCS_EXT_RGBX ||
 598              cinfo->in_color_space == JCS_EXT_BGR ||
 599              cinfo->in_color_space == JCS_EXT_BGRX ||
 600              cinfo->in_color_space == JCS_EXT_XBGR ||
 601              cinfo->in_color_space == JCS_EXT_XRGB ||
 602              cinfo->in_color_space == JCS_EXT_RGBA ||
 603              cinfo->in_color_space == JCS_EXT_BGRA ||
 604              cinfo->in_color_space == JCS_EXT_ABGR ||
 605              cinfo->in_color_space == JCS_EXT_ARGB) {
 606       if (jsimd_can_rgb_gray())
 607         cconvert->pub.color_convert = jsimd_rgb_gray_convert;
 608       else {
 609         cconvert->pub.start_pass = rgb_ycc_start;
 610         cconvert->pub.color_convert = rgb_gray_convert;
 611       }
 612     } else if (cinfo->in_color_space == JCS_YCbCr)
 613       cconvert->pub.color_convert = grayscale_convert;
 614     else
 615       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 616     break;
 617
 618   case JCS_RGB:
 619     if (cinfo->num_components != 3)
 620       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 621     if (rgb_red[cinfo->in_color_space] == 0 &&
 622         rgb_green[cinfo->in_color_space] == 1 &&
 623         rgb_blue[cinfo->in_color_space] == 2 &&
 624         rgb_pixelsize[cinfo->in_color_space] == 3) {
 625 #if defined(__mips__)
 626       if (jsimd_c_can_null_convert())
 627         cconvert->pub.color_convert = jsimd_c_null_convert;
 628       else
 629 #endif
 630         cconvert->pub.color_convert = null_convert;
 631     } else if (cinfo->in_color_space == JCS_RGB ||
 632                cinfo->in_color_space == JCS_EXT_RGB ||
 633                cinfo->in_color_space == JCS_EXT_RGBX ||
 634                cinfo->in_color_space == JCS_EXT_BGR ||
 635                cinfo->in_color_space == JCS_EXT_BGRX ||
 636                cinfo->in_color_space == JCS_EXT_XBGR ||
 637                cinfo->in_color_space == JCS_EXT_XRGB ||
 638                cinfo->in_color_space == JCS_EXT_RGBA ||
 639                cinfo->in_color_space == JCS_EXT_BGRA ||
 640                cinfo->in_color_space == JCS_EXT_ABGR ||
 641                cinfo->in_color_space == JCS_EXT_ARGB)
 642       cconvert->pub.color_convert = rgb_rgb_convert;
 643     else
 644       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 645     break;
 646
 647   case JCS_YCbCr:
 648     if (cinfo->num_components != 3)
 649       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 650     if (cinfo->in_color_space == JCS_RGB ||
 651         cinfo->in_color_space == JCS_EXT_RGB ||
 652         cinfo->in_color_space == JCS_EXT_RGBX ||
 653         cinfo->in_color_space == JCS_EXT_BGR ||
 654         cinfo->in_color_space == JCS_EXT_BGRX ||
 655         cinfo->in_color_space == JCS_EXT_XBGR ||
 656         cinfo->in_color_space == JCS_EXT_XRGB ||
 657         cinfo->in_color_space == JCS_EXT_RGBA ||
 658         cinfo->in_color_space == JCS_EXT_BGRA ||
 659         cinfo->in_color_space == JCS_EXT_ABGR ||
 660         cinfo->in_color_space == JCS_EXT_ARGB) {
 661       if (jsimd_can_rgb_ycc())
 662         cconvert->pub.color_convert = jsimd_rgb_ycc_convert;
 663       else {
 664         cconvert->pub.start_pass = rgb_ycc_start;
 665         cconvert->pub.color_convert = rgb_ycc_convert;
 666       }
 667     } else if (cinfo->in_color_space == JCS_YCbCr) {
 668 #if defined(__mips__)
 669       if (jsimd_c_can_null_convert())
 670         cconvert->pub.color_convert = jsimd_c_null_convert;
 671       else
 672 #endif
 673         cconvert->pub.color_convert = null_convert;
 674     } else
 675       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 676     break;
 677
 678   case JCS_CMYK:
 679     if (cinfo->num_components != 4)
 680       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 681     if (cinfo->in_color_space == JCS_CMYK) {
 682 #if defined(__mips__)
 683       if (jsimd_c_can_null_convert())
 684         cconvert->pub.color_convert = jsimd_c_null_convert;
 685       else
 686 #endif
 687         cconvert->pub.color_convert = null_convert;
 688     } else
 689       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 690     break;
 691
 692   case JCS_YCCK:
 693     if (cinfo->num_components != 4)
 694       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 695     if (cinfo->in_color_space == JCS_CMYK) {
 696       cconvert->pub.start_pass = rgb_ycc_start;
 697       cconvert->pub.color_convert = cmyk_ycck_convert;
 698     } else if (cinfo->in_color_space == JCS_YCCK) {
 699 #if defined(__mips__)
 700       if (jsimd_c_can_null_convert())
 701         cconvert->pub.color_convert = jsimd_c_null_convert;
 702       else
 703 #endif
 704         cconvert->pub.color_convert = null_convert;
 705     } else
 706       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 707     break;
 708
 709   default:                      /* allow null conversion of JCS_UNKNOWN */
 710     if (cinfo->jpeg_color_space != cinfo->in_color_space ||
 711         cinfo->num_components != cinfo->input_components)
 712       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 713 #if defined(__mips__)
 714     if (jsimd_c_can_null_convert())
 715       cconvert->pub.color_convert = jsimd_c_null_convert;
 716     else
 717 #endif
 718       cconvert->pub.color_convert = null_convert;
 719     break;
 720   }
 721 }