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  * Modifications:
   7  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
   8  * Copyright (C) 2009-2012, D. R. Commander.
   9  * For conditions of distribution and use, see the accompanying README file.
  10  *
  11  * This file contains input colorspace conversion routines.
  12  */
  13
  14 #define JPEG_INTERNALS
  15 #include "jinclude.h"
  16 #include "jpeglib.h"
  17 #include "jsimd.h"
  18 #include "config.h"
  19
  20
  21 /* Private subobject */
  22
  23 typedef struct {
  24   struct jpeg_color_converter pub; /* public fields */
  25
  26   /* Private state for RGB->YCC conversion */
  27   INT32 * rgb_ycc_tab;          /* => table for RGB to YCbCr conversion */
  28 } my_color_converter;
  29
  30 typedef my_color_converter * my_cconvert_ptr;
  31
  32
  33 /**************** RGB -> YCbCr conversion: most common case **************/
  34
  35 /*
  36  * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
  37  * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
  38  * The conversion equations to be implemented are therefore
  39  *      Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B
  40  *      Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B  + CENTERJSAMPLE
  41  *      Cr =  0.50000 * R - 0.41869 * G - 0.08131 * B  + CENTERJSAMPLE
  42  * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
  43  * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2,
  44  * rather than CENTERJSAMPLE, for Cb and Cr.  This gave equal positive and
  45  * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0)
  46  * were not represented exactly.  Now we sacrifice exact representation of
  47  * maximum red and maximum blue in order to get exact grayscales.
  48  *
  49  * To avoid floating-point arithmetic, we represent the fractional constants
  50  * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
  51  * the products by 2^16, with appropriate rounding, to get the correct answer.
  52  *
  53  * For even more speed, we avoid doing any multiplications in the inner loop
  54  * by precalculating the constants times R,G,B for all possible values.
  55  * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table);
  56  * for 12-bit samples it is still acceptable.  It's not very reasonable for
  57  * 16-bit samples, but if you want lossless storage you shouldn't be changing
  58  * colorspace anyway.
  59  * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included
  60  * in the tables to save adding them separately in the inner loop.
  61  */
  62
  63 #define SCALEBITS       16      /* speediest right-shift on some machines */
  64 #define CBCR_OFFSET     ((INT32) CENTERJSAMPLE << SCALEBITS)
  65 #define ONE_HALF        ((INT32) 1 << (SCALEBITS-1))
  66 #define FIX(x)          ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
  67
  68 /* We allocate one big table and divide it up into eight parts, instead of
  69  * doing eight alloc_small requests.  This lets us use a single table base
  70  * address, which can be held in a register in the inner loops on many
  71  * machines (more than can hold all eight addresses, anyway).
  72  */
  73
  74 #define R_Y_OFF         0                       /* offset to R => Y section */
  75 #define G_Y_OFF         (1*(MAXJSAMPLE+1))      /* offset to G => Y section */
  76 #define B_Y_OFF         (2*(MAXJSAMPLE+1))      /* etc. */
  77 #define R_CB_OFF        (3*(MAXJSAMPLE+1))
  78 #define G_CB_OFF        (4*(MAXJSAMPLE+1))
  79 #define B_CB_OFF        (5*(MAXJSAMPLE+1))
  80 #define R_CR_OFF        B_CB_OFF                /* B=>Cb, R=>Cr are the same */
  81 #define G_CR_OFF        (6*(MAXJSAMPLE+1))
  82 #define B_CR_OFF        (7*(MAXJSAMPLE+1))
  83 #define TABLE_SIZE      (8*(MAXJSAMPLE+1))
  84
  85
  86 /* Include inline routines for colorspace extensions */
  87
  88 #include "jccolext.c"
  89 #undef RGB_RED
  90 #undef RGB_GREEN
  91 #undef RGB_BLUE
  92 #undef RGB_PIXELSIZE
  93
  94 #define RGB_RED EXT_RGB_RED
  95 #define RGB_GREEN EXT_RGB_GREEN
  96 #define RGB_BLUE EXT_RGB_BLUE
  97 #define RGB_PIXELSIZE EXT_RGB_PIXELSIZE
  98 #define rgb_ycc_convert_internal extrgb_ycc_convert_internal
  99 #define rgb_gray_convert_internal extrgb_gray_convert_internal
 100 #define rgb_rgb_convert_internal extrgb_rgb_convert_internal
 101 #include "jccolext.c"
 102 #undef RGB_RED
 103 #undef RGB_GREEN
 104 #undef RGB_BLUE
 105 #undef RGB_PIXELSIZE
 106 #undef rgb_ycc_convert_internal
 107 #undef rgb_gray_convert_internal
 108 #undef rgb_rgb_convert_internal
 109
 110 #define RGB_RED EXT_RGBX_RED
 111 #define RGB_GREEN EXT_RGBX_GREEN
 112 #define RGB_BLUE EXT_RGBX_BLUE
 113 #define RGB_PIXELSIZE EXT_RGBX_PIXELSIZE
 114 #define rgb_ycc_convert_internal extrgbx_ycc_convert_internal
 115 #define rgb_gray_convert_internal extrgbx_gray_convert_internal
 116 #define rgb_rgb_convert_internal extrgbx_rgb_convert_internal
 117 #include "jccolext.c"
 118 #undef RGB_RED
 119 #undef RGB_GREEN
 120 #undef RGB_BLUE
 121 #undef RGB_PIXELSIZE
 122 #undef rgb_ycc_convert_internal
 123 #undef rgb_gray_convert_internal
 124 #undef rgb_rgb_convert_internal
 125
 126 #define RGB_RED EXT_BGR_RED
 127 #define RGB_GREEN EXT_BGR_GREEN
 128 #define RGB_BLUE EXT_BGR_BLUE
 129 #define RGB_PIXELSIZE EXT_BGR_PIXELSIZE
 130 #define rgb_ycc_convert_internal extbgr_ycc_convert_internal
 131 #define rgb_gray_convert_internal extbgr_gray_convert_internal
 132 #define rgb_rgb_convert_internal extbgr_rgb_convert_internal
 133 #include "jccolext.c"
 134 #undef RGB_RED
 135 #undef RGB_GREEN
 136 #undef RGB_BLUE
 137 #undef RGB_PIXELSIZE
 138 #undef rgb_ycc_convert_internal
 139 #undef rgb_gray_convert_internal
 140 #undef rgb_rgb_convert_internal
 141
 142 #define RGB_RED EXT_BGRX_RED
 143 #define RGB_GREEN EXT_BGRX_GREEN
 144 #define RGB_BLUE EXT_BGRX_BLUE
 145 #define RGB_PIXELSIZE EXT_BGRX_PIXELSIZE
 146 #define rgb_ycc_convert_internal extbgrx_ycc_convert_internal
 147 #define rgb_gray_convert_internal extbgrx_gray_convert_internal
 148 #define rgb_rgb_convert_internal extbgrx_rgb_convert_internal
 149 #include "jccolext.c"
 150 #undef RGB_RED
 151 #undef RGB_GREEN
 152 #undef RGB_BLUE
 153 #undef RGB_PIXELSIZE
 154 #undef rgb_ycc_convert_internal
 155 #undef rgb_gray_convert_internal
 156 #undef rgb_rgb_convert_internal
 157
 158 #define RGB_RED EXT_XBGR_RED
 159 #define RGB_GREEN EXT_XBGR_GREEN
 160 #define RGB_BLUE EXT_XBGR_BLUE
 161 #define RGB_PIXELSIZE EXT_XBGR_PIXELSIZE
 162 #define rgb_ycc_convert_internal extxbgr_ycc_convert_internal
 163 #define rgb_gray_convert_internal extxbgr_gray_convert_internal
 164 #define rgb_rgb_convert_internal extxbgr_rgb_convert_internal
 165 #include "jccolext.c"
 166 #undef RGB_RED
 167 #undef RGB_GREEN
 168 #undef RGB_BLUE
 169 #undef RGB_PIXELSIZE
 170 #undef rgb_ycc_convert_internal
 171 #undef rgb_gray_convert_internal
 172 #undef rgb_rgb_convert_internal
 173
 174 #define RGB_RED EXT_XRGB_RED
 175 #define RGB_GREEN EXT_XRGB_GREEN
 176 #define RGB_BLUE EXT_XRGB_BLUE
 177 #define RGB_PIXELSIZE EXT_XRGB_PIXELSIZE
 178 #define rgb_ycc_convert_internal extxrgb_ycc_convert_internal
 179 #define rgb_gray_convert_internal extxrgb_gray_convert_internal
 180 #define rgb_rgb_convert_internal extxrgb_rgb_convert_internal
 181 #include "jccolext.c"
 182 #undef RGB_RED
 183 #undef RGB_GREEN
 184 #undef RGB_BLUE
 185 #undef RGB_PIXELSIZE
 186 #undef rgb_ycc_convert_internal
 187 #undef rgb_gray_convert_internal
 188 #undef rgb_rgb_convert_internal
 189
 190
 191 /*
 192  * Initialize for RGB->YCC colorspace conversion.
 193  */
 194
 195 METHODDEF(void)
 196 rgb_ycc_start (j_compress_ptr cinfo)
 197 {
 198   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 199   INT32 * rgb_ycc_tab;
 200   INT32 i;
 201
 202   /* Allocate and fill in the conversion tables. */
 203   cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *)
 204     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 205                                 (TABLE_SIZE * SIZEOF(INT32)));
 206
 207   for (i = 0; i <= MAXJSAMPLE; i++) {
 208     rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i;
 209     rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i;
 210     rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i     + ONE_HALF;
 211     rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i;
 212     rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i;
 213     /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr.
 214      * This ensures that the maximum output will round to MAXJSAMPLE
 215      * not MAXJSAMPLE+1, and thus that we don't have to range-limit.
 216      */
 217     rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
 218 /*  B=>Cb and R=>Cr tables are the same
 219     rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i    + CBCR_OFFSET + ONE_HALF-1;
 220 */
 221     rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i;
 222     rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i;
 223   }
 224 }
 225
 226
 227 /*
 228  * Convert some rows of samples to the JPEG colorspace.
 229  */
 230
 231 METHODDEF(void)
 232 rgb_ycc_convert (j_compress_ptr cinfo,
 233                  JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 234                  JDIMENSION output_row, int num_rows)
 235 {
 236   switch (cinfo->in_color_space) {
 237     case JCS_EXT_RGB:
 238       extrgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 239                                   num_rows);
 240       break;
 241     case JCS_EXT_RGBX:
 242     case JCS_EXT_RGBA:
 243       extrgbx_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 244                                    num_rows);
 245       break;
 246     case JCS_EXT_BGR:
 247       extbgr_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 248                                   num_rows);
 249       break;
 250     case JCS_EXT_BGRX:
 251     case JCS_EXT_BGRA:
 252       extbgrx_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 253                                    num_rows);
 254       break;
 255     case JCS_EXT_XBGR:
 256     case JCS_EXT_ABGR:
 257       extxbgr_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 258                                    num_rows);
 259       break;
 260     case JCS_EXT_XRGB:
 261     case JCS_EXT_ARGB:
 262       extxrgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 263                                    num_rows);
 264       break;
 265     default:
 266       rgb_ycc_convert_internal(cinfo, input_buf, output_buf, output_row,
 267                                num_rows);
 268       break;
 269   }
 270 }
 271
 272
 273 /**************** Cases other than RGB -> YCbCr **************/
 274
 275
 276 /*
 277  * Convert some rows of samples to the JPEG colorspace.
 278  */
 279
 280 METHODDEF(void)
 281 rgb_gray_convert (j_compress_ptr cinfo,
 282                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 283                   JDIMENSION output_row, int num_rows)
 284 {
 285   switch (cinfo->in_color_space) {
 286     case JCS_EXT_RGB:
 287       extrgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 288                                    num_rows);
 289       break;
 290     case JCS_EXT_RGBX:
 291     case JCS_EXT_RGBA:
 292       extrgbx_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 293                                     num_rows);
 294       break;
 295     case JCS_EXT_BGR:
 296       extbgr_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 297                                    num_rows);
 298       break;
 299     case JCS_EXT_BGRX:
 300     case JCS_EXT_BGRA:
 301       extbgrx_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 302                                     num_rows);
 303       break;
 304     case JCS_EXT_XBGR:
 305     case JCS_EXT_ABGR:
 306       extxbgr_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 307                                     num_rows);
 308       break;
 309     case JCS_EXT_XRGB:
 310     case JCS_EXT_ARGB:
 311       extxrgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 312                                     num_rows);
 313       break;
 314     default:
 315       rgb_gray_convert_internal(cinfo, input_buf, output_buf, output_row,
 316                                 num_rows);
 317       break;
 318   }
 319 }
 320
 321
 322 /*
 323  * Extended RGB to plain RGB conversion
 324  */
 325
 326 METHODDEF(void)
 327 rgb_rgb_convert (j_compress_ptr cinfo,
 328                   JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 329                   JDIMENSION output_row, int num_rows)
 330 {
 331   switch (cinfo->in_color_space) {
 332     case JCS_EXT_RGB:
 333       extrgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 334                                   num_rows);
 335       break;
 336     case JCS_EXT_RGBX:
 337     case JCS_EXT_RGBA:
 338       extrgbx_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 339                                    num_rows);
 340       break;
 341     case JCS_EXT_BGR:
 342       extbgr_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 343                                   num_rows);
 344       break;
 345     case JCS_EXT_BGRX:
 346     case JCS_EXT_BGRA:
 347       extbgrx_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 348                                    num_rows);
 349       break;
 350     case JCS_EXT_XBGR:
 351     case JCS_EXT_ABGR:
 352       extxbgr_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 353                                    num_rows);
 354       break;
 355     case JCS_EXT_XRGB:
 356     case JCS_EXT_ARGB:
 357       extxrgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 358                                    num_rows);
 359       break;
 360     default:
 361       rgb_rgb_convert_internal(cinfo, input_buf, output_buf, output_row,
 362                                num_rows);
 363       break;
 364   }
 365 }
 366
 367
 368 /*
 369  * Convert some rows of samples to the JPEG colorspace.
 370  * This version handles Adobe-style CMYK->YCCK conversion,
 371  * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same
 372  * conversion as above, while passing K (black) unchanged.
 373  * We assume rgb_ycc_start has been called.
 374  */
 375
 376 METHODDEF(void)
 377 cmyk_ycck_convert (j_compress_ptr cinfo,
 378                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 379                    JDIMENSION output_row, int num_rows)
 380 {
 381   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 382   register int r, g, b;
 383   register INT32 * ctab = cconvert->rgb_ycc_tab;
 384   register JSAMPROW inptr;
 385   register JSAMPROW outptr0, outptr1, outptr2, outptr3;
 386   register JDIMENSION col;
 387   JDIMENSION num_cols = cinfo->image_width;
 388
 389   while (--num_rows >= 0) {
 390     inptr = *input_buf++;
 391     outptr0 = output_buf[0][output_row];
 392     outptr1 = output_buf[1][output_row];
 393     outptr2 = output_buf[2][output_row];
 394     outptr3 = output_buf[3][output_row];
 395     output_row++;
 396     for (col = 0; col < num_cols; col++) {
 397       r = MAXJSAMPLE - GETJSAMPLE(inptr[0]);
 398       g = MAXJSAMPLE - GETJSAMPLE(inptr[1]);
 399       b = MAXJSAMPLE - GETJSAMPLE(inptr[2]);
 400       /* K passes through as-is */
 401       outptr3[col] = inptr[3];  /* don't need GETJSAMPLE here */
 402       inptr += 4;
 403       /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations
 404        * must be too; we do not need an explicit range-limiting operation.
 405        * Hence the value being shifted is never negative, and we don't
 406        * need the general RIGHT_SHIFT macro.
 407        */
 408       /* Y */
 409       outptr0[col] = (JSAMPLE)
 410                 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF])
 411                  >> SCALEBITS);
 412       /* Cb */
 413       outptr1[col] = (JSAMPLE)
 414                 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF])
 415                  >> SCALEBITS);
 416       /* Cr */
 417       outptr2[col] = (JSAMPLE)
 418                 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF])
 419                  >> SCALEBITS);
 420     }
 421   }
 422 }
 423
 424
 425 /*
 426  * Convert some rows of samples to the JPEG colorspace.
 427  * This version handles grayscale output with no conversion.
 428  * The source can be either plain grayscale or YCbCr (since Y == gray).
 429  */
 430
 431 METHODDEF(void)
 432 grayscale_convert (j_compress_ptr cinfo,
 433                    JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 434                    JDIMENSION output_row, int num_rows)
 435 {
 436   register JSAMPROW inptr;
 437   register JSAMPROW outptr;
 438   register JDIMENSION col;
 439   JDIMENSION num_cols = cinfo->image_width;
 440   int instride = cinfo->input_components;
 441
 442   while (--num_rows >= 0) {
 443     inptr = *input_buf++;
 444     outptr = output_buf[0][output_row];
 445     output_row++;
 446     for (col = 0; col < num_cols; col++) {
 447       outptr[col] = inptr[0];   /* don't need GETJSAMPLE() here */
 448       inptr += instride;
 449     }
 450   }
 451 }
 452
 453
 454 /*
 455  * Convert some rows of samples to the JPEG colorspace.
 456  * This version handles multi-component colorspaces without conversion.
 457  * We assume input_components == num_components.
 458  */
 459
 460 METHODDEF(void)
 461 null_convert (j_compress_ptr cinfo,
 462               JSAMPARRAY input_buf, JSAMPIMAGE output_buf,
 463               JDIMENSION output_row, int num_rows)
 464 {
 465   register JSAMPROW inptr;
 466   register JSAMPROW outptr;
 467   register JDIMENSION col;
 468   register int ci;
 469   int nc = cinfo->num_components;
 470   JDIMENSION num_cols = cinfo->image_width;
 471
 472   while (--num_rows >= 0) {
 473     /* It seems fastest to make a separate pass for each component. */
 474     for (ci = 0; ci < nc; ci++) {
 475       inptr = *input_buf;
 476       outptr = output_buf[ci][output_row];
 477       for (col = 0; col < num_cols; col++) {
 478         outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */
 479         inptr += nc;
 480       }
 481     }
 482     input_buf++;
 483     output_row++;
 484   }
 485 }
 486
 487
 488 /*
 489  * Empty method for start_pass.
 490  */
 491
 492 METHODDEF(void)
 493 null_method (j_compress_ptr cinfo)
 494 {
 495   /* no work needed */
 496 }
 497
 498
 499 /*
 500  * Module initialization routine for input colorspace conversion.
 501  */
 502
 503 GLOBAL(void)
 504 jinit_color_converter (j_compress_ptr cinfo)
 505 {
 506   my_cconvert_ptr cconvert;
 507
 508   cconvert = (my_cconvert_ptr)
 509     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 510                                 SIZEOF(my_color_converter));
 511   cinfo->cconvert = (struct jpeg_color_converter *) cconvert;
 512   /* set start_pass to null method until we find out differently */
 513   cconvert->pub.start_pass = null_method;
 514
 515   /* Make sure input_components agrees with in_color_space */
 516   switch (cinfo->in_color_space) {
 517   case JCS_GRAYSCALE:
 518     if (cinfo->input_components != 1)
 519       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 520     break;
 521
 522   case JCS_RGB:
 523   case JCS_EXT_RGB:
 524   case JCS_EXT_RGBX:
 525   case JCS_EXT_BGR:
 526   case JCS_EXT_BGRX:
 527   case JCS_EXT_XBGR:
 528   case JCS_EXT_XRGB:
 529   case JCS_EXT_RGBA:
 530   case JCS_EXT_BGRA:
 531   case JCS_EXT_ABGR:
 532   case JCS_EXT_ARGB:
 533     if (cinfo->input_components != rgb_pixelsize[cinfo->in_color_space])
 534       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 535     break;
 536
 537   case JCS_YCbCr:
 538     if (cinfo->input_components != 3)
 539       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 540     break;
 541
 542   case JCS_CMYK:
 543   case JCS_YCCK:
 544     if (cinfo->input_components != 4)
 545       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 546     break;
 547
 548   default:                      /* JCS_UNKNOWN can be anything */
 549     if (cinfo->input_components < 1)
 550       ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE);
 551     break;
 552   }
 553
 554   /* Check num_components, set conversion method based on requested space */
 555   switch (cinfo->jpeg_color_space) {
 556   case JCS_GRAYSCALE:
 557     if (cinfo->num_components != 1)
 558       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 559     if (cinfo->in_color_space == JCS_GRAYSCALE)
 560       cconvert->pub.color_convert = grayscale_convert;
 561     else if (cinfo->in_color_space == JCS_RGB ||
 562              cinfo->in_color_space == JCS_EXT_RGB ||
 563              cinfo->in_color_space == JCS_EXT_RGBX ||
 564              cinfo->in_color_space == JCS_EXT_BGR ||
 565              cinfo->in_color_space == JCS_EXT_BGRX ||
 566              cinfo->in_color_space == JCS_EXT_XBGR ||
 567              cinfo->in_color_space == JCS_EXT_XRGB ||
 568              cinfo->in_color_space == JCS_EXT_RGBA ||
 569              cinfo->in_color_space == JCS_EXT_BGRA ||
 570              cinfo->in_color_space == JCS_EXT_ABGR ||
 571              cinfo->in_color_space == JCS_EXT_ARGB) {
 572       if (jsimd_can_rgb_gray())
 573         cconvert->pub.color_convert = jsimd_rgb_gray_convert;
 574       else {
 575         cconvert->pub.start_pass = rgb_ycc_start;
 576         cconvert->pub.color_convert = rgb_gray_convert;
 577       }
 578     } else if (cinfo->in_color_space == JCS_YCbCr)
 579       cconvert->pub.color_convert = grayscale_convert;
 580     else
 581       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 582     break;
 583
 584   case JCS_RGB:
 585     if (cinfo->num_components != 3)
 586       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 587     if (rgb_red[cinfo->in_color_space] == 0 &&
 588         rgb_green[cinfo->in_color_space] == 1 &&
 589         rgb_blue[cinfo->in_color_space] == 2 &&
 590         rgb_pixelsize[cinfo->in_color_space] == 3)
 591       cconvert->pub.color_convert = null_convert;
 592     else if (cinfo->in_color_space == JCS_RGB ||
 593              cinfo->in_color_space == JCS_EXT_RGB ||
 594              cinfo->in_color_space == JCS_EXT_RGBX ||
 595              cinfo->in_color_space == JCS_EXT_BGR ||
 596              cinfo->in_color_space == JCS_EXT_BGRX ||
 597              cinfo->in_color_space == JCS_EXT_XBGR ||
 598              cinfo->in_color_space == JCS_EXT_XRGB ||
 599              cinfo->in_color_space == JCS_EXT_RGBA ||
 600              cinfo->in_color_space == JCS_EXT_BGRA ||
 601              cinfo->in_color_space == JCS_EXT_ABGR ||
 602              cinfo->in_color_space == JCS_EXT_ARGB)
 603       cconvert->pub.color_convert = rgb_rgb_convert;
 604     else
 605       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 606     break;
 607
 608   case JCS_YCbCr:
 609     if (cinfo->num_components != 3)
 610       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 611     if (cinfo->in_color_space == JCS_RGB ||
 612         cinfo->in_color_space == JCS_EXT_RGB ||
 613         cinfo->in_color_space == JCS_EXT_RGBX ||
 614         cinfo->in_color_space == JCS_EXT_BGR ||
 615         cinfo->in_color_space == JCS_EXT_BGRX ||
 616         cinfo->in_color_space == JCS_EXT_XBGR ||
 617         cinfo->in_color_space == JCS_EXT_XRGB ||
 618         cinfo->in_color_space == JCS_EXT_RGBA ||
 619         cinfo->in_color_space == JCS_EXT_BGRA ||
 620         cinfo->in_color_space == JCS_EXT_ABGR ||
 621         cinfo->in_color_space == JCS_EXT_ARGB) {
 622       if (jsimd_can_rgb_ycc())
 623         cconvert->pub.color_convert = jsimd_rgb_ycc_convert;
 624       else {
 625         cconvert->pub.start_pass = rgb_ycc_start;
 626         cconvert->pub.color_convert = rgb_ycc_convert;
 627       }
 628     } else if (cinfo->in_color_space == JCS_YCbCr)
 629       cconvert->pub.color_convert = null_convert;
 630     else
 631       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 632     break;
 633
 634   case JCS_CMYK:
 635     if (cinfo->num_components != 4)
 636       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 637     if (cinfo->in_color_space == JCS_CMYK)
 638       cconvert->pub.color_convert = null_convert;
 639     else
 640       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 641     break;
 642
 643   case JCS_YCCK:
 644     if (cinfo->num_components != 4)
 645       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 646     if (cinfo->in_color_space == JCS_CMYK) {
 647       cconvert->pub.start_pass = rgb_ycc_start;
 648       cconvert->pub.color_convert = cmyk_ycck_convert;
 649     } else if (cinfo->in_color_space == JCS_YCCK)
 650       cconvert->pub.color_convert = null_convert;
 651     else
 652       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 653     break;
 654
 655   default:                      /* allow null conversion of JCS_UNKNOWN */
 656     if (cinfo->jpeg_color_space != cinfo->in_color_space ||
 657         cinfo->num_components != cinfo->input_components)
 658       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 659     cconvert->pub.color_convert = null_convert;
 660     break;
 661   }
 662 }