src/jpeg/jdcolor.c

   1 /*
   2  * jdcolor.c
   3  *
   4  * Copyright (C) 1991-1997, Thomas G. Lane.
   5  * This file is part of the Independent JPEG Group's software.
   6  * For conditions of distribution and use, see the accompanying README file.
   7  *
   8  * This file contains output colorspace conversion routines.
   9  */
  10
  11 #define JPEG_INTERNALS
  12 #include "jinclude.h"
  13 #include "jpeglib.h"
  14
  15 #if defined(__VISAGECPP__)
  16 /* Visual Age fixups for multiple declarations */
  17 #  define null_convert   null_convert2 /* already in jcmaint.c */
  18 #  define grayscale_convert   grayscale_convert2 /* already in jcmaint.c */
  19 #endif
  20
  21 /* Private subobject */
  22
  23 typedef struct {
  24   struct jpeg_color_deconverter pub; /* public fields */
  25
  26   /* Private state for YCC->RGB conversion */
  27   int * Cr_r_tab;               /* => table for Cr to R conversion */
  28   int * Cb_b_tab;               /* => table for Cb to B conversion */
  29   JPEG_INT32 * Cr_g_tab;                /* => table for Cr to G conversion */
  30   JPEG_INT32 * Cb_g_tab;                /* => table for Cb to G conversion */
  31 } my_color_deconverter;
  32
  33 typedef my_color_deconverter * my_cconvert_ptr;
  34
  35
  36 /**************** YCbCr -> RGB conversion: most common case **************/
  37
  38 /*
  39  * YCbCr is defined per CCIR 601-1, except that Cb and Cr are
  40  * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5.
  41  * The conversion equations to be implemented are therefore
  42  *      R = Y                + 1.40200 * Cr
  43  *      G = Y - 0.34414 * Cb - 0.71414 * Cr
  44  *      B = Y + 1.77200 * Cb
  45  * where Cb and Cr represent the incoming values less CENTERJSAMPLE.
  46  * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.)
  47  *
  48  * To avoid floating-point arithmetic, we represent the fractional constants
  49  * as integers scaled up by 2^16 (about 4 digits precision); we have to divide
  50  * the products by 2^16, with appropriate rounding, to get the correct answer.
  51  * Notice that Y, being an integral input, does not contribute any fraction
  52  * so it need not participate in the rounding.
  53  *
  54  * For even more speed, we avoid doing any multiplications in the inner loop
  55  * by precalculating the constants times Cb and Cr 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 Cr=>R and Cb=>B values can be rounded to integers in advance; the
  61  * values for the G calculation are left scaled up, since we must add them
  62  * together before rounding.
  63  */
  64
  65 #define SCALEBITS       16      /* speediest right-shift on some machines */
  66 #define ONE_HALF        ((JPEG_INT32) 1 << (SCALEBITS-1))
  67 #define FIX(x)          ((JPEG_INT32) ((x) * (1L<<SCALEBITS) + 0.5))
  68
  69
  70 /*
  71  * Initialize tables for YCC->RGB colorspace conversion.
  72  */
  73
  74 LOCAL(void)
  75 build_ycc_rgb_table (j_decompress_ptr cinfo)
  76 {
  77   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
  78   int i;
  79   JPEG_INT32 x;
  80   SHIFT_TEMPS
  81
  82   cconvert->Cr_r_tab = (int *)
  83     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  84                                 (MAXJSAMPLE+1) * SIZEOF(int));
  85   cconvert->Cb_b_tab = (int *)
  86     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  87                                 (MAXJSAMPLE+1) * SIZEOF(int));
  88   cconvert->Cr_g_tab = (JPEG_INT32 *)
  89     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  90                                 (MAXJSAMPLE+1) * SIZEOF(JPEG_INT32));
  91   cconvert->Cb_g_tab = (JPEG_INT32 *)
  92     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  93                                 (MAXJSAMPLE+1) * SIZEOF(JPEG_INT32));
  94
  95   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
  96     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
  97     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
  98     /* Cr=>R value is nearest int to 1.40200 * x */
  99     cconvert->Cr_r_tab[i] = (int)
 100                     RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
 101     /* Cb=>B value is nearest int to 1.77200 * x */
 102     cconvert->Cb_b_tab[i] = (int)
 103                     RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
 104     /* Cr=>G value is scaled-up -0.71414 * x */
 105     cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x;
 106     /* Cb=>G value is scaled-up -0.34414 * x */
 107     /* We also add in ONE_HALF so that need not do it in inner loop */
 108     cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
 109   }
 110 }
 111
 112
 113 /*
 114  * Convert some rows of samples to the output colorspace.
 115  *
 116  * Note that we change from noninterleaved, one-plane-per-component format
 117  * to interleaved-pixel format.  The output buffer is therefore three times
 118  * as wide as the input buffer.
 119  * A starting row offset is provided only for the input buffer.  The caller
 120  * can easily adjust the passed output_buf value to accommodate any row
 121  * offset required on that side.
 122  */
 123
 124 METHODDEF(void)
 125 ycc_rgb_convert (j_decompress_ptr cinfo,
 126                  JSAMPIMAGE input_buf, JDIMENSION input_row,
 127                  JSAMPARRAY output_buf, int num_rows)
 128 {
 129   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 130   register int y, cb, cr;
 131   register JSAMPROW outptr;
 132   register JSAMPROW inptr0, inptr1, inptr2;
 133   register JDIMENSION col;
 134   JDIMENSION num_cols = cinfo->output_width;
 135   /* copy these pointers into registers if possible */
 136   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 137   register int * Crrtab = cconvert->Cr_r_tab;
 138   register int * Cbbtab = cconvert->Cb_b_tab;
 139   register JPEG_INT32 * Crgtab = cconvert->Cr_g_tab;
 140   register JPEG_INT32 * Cbgtab = cconvert->Cb_g_tab;
 141   SHIFT_TEMPS
 142
 143   while (--num_rows >= 0) {
 144     inptr0 = input_buf[0][input_row];
 145     inptr1 = input_buf[1][input_row];
 146     inptr2 = input_buf[2][input_row];
 147     input_row++;
 148     outptr = *output_buf++;
 149     for (col = 0; col < num_cols; col++) {
 150       y  = GETJSAMPLE(inptr0[col]);
 151       cb = GETJSAMPLE(inptr1[col]);
 152       cr = GETJSAMPLE(inptr2[col]);
 153       /* Range-limiting is essential due to noise introduced by DCT losses. */
 154       outptr[RGB_RED] =   range_limit[y + Crrtab[cr]];
 155       outptr[RGB_GREEN] = range_limit[y +
 156                               ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
 157                                                  SCALEBITS))];
 158       outptr[RGB_BLUE] =  range_limit[y + Cbbtab[cb]];
 159       outptr += RGB_PIXELSIZE;
 160     }
 161   }
 162 }
 163
 164
 165 /**************** Cases other than YCbCr -> RGB **************/
 166
 167
 168 /*
 169  * Color conversion for no colorspace change: just copy the data,
 170  * converting from separate-planes to interleaved representation.
 171  */
 172
 173 METHODDEF(void)
 174 null_convert (j_decompress_ptr cinfo,
 175               JSAMPIMAGE input_buf, JDIMENSION input_row,
 176               JSAMPARRAY output_buf, int num_rows)
 177 {
 178   register JSAMPROW inptr, outptr;
 179   register JDIMENSION count;
 180   register int num_components = cinfo->num_components;
 181   JDIMENSION num_cols = cinfo->output_width;
 182   int ci;
 183
 184   while (--num_rows >= 0) {
 185     for (ci = 0; ci < num_components; ci++) {
 186       inptr = input_buf[ci][input_row];
 187       outptr = output_buf[0] + ci;
 188       for (count = num_cols; count > 0; count--) {
 189         *outptr = *inptr++;     /* needn't bother with GETJSAMPLE() here */
 190         outptr += num_components;
 191       }
 192     }
 193     input_row++;
 194     output_buf++;
 195   }
 196 }
 197
 198
 199 /*
 200  * Color conversion for grayscale: just copy the data.
 201  * This also works for YCbCr -> grayscale conversion, in which
 202  * we just copy the Y (luminance) component and ignore chrominance.
 203  */
 204
 205 METHODDEF(void)
 206 grayscale_convert (j_decompress_ptr cinfo,
 207                    JSAMPIMAGE input_buf, JDIMENSION input_row,
 208                    JSAMPARRAY output_buf, int num_rows)
 209 {
 210   jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0,
 211                     num_rows, cinfo->output_width);
 212 }
 213
 214
 215 /*
 216  * Convert grayscale to RGB: just duplicate the graylevel three times.
 217  * This is provided to support applications that don't want to cope
 218  * with grayscale as a separate case.
 219  */
 220
 221 METHODDEF(void)
 222 gray_rgb_convert (j_decompress_ptr cinfo,
 223                   JSAMPIMAGE input_buf, JDIMENSION input_row,
 224                   JSAMPARRAY output_buf, int num_rows)
 225 {
 226   register JSAMPROW inptr, outptr;
 227   register JDIMENSION col;
 228   JDIMENSION num_cols = cinfo->output_width;
 229
 230   while (--num_rows >= 0) {
 231     inptr = input_buf[0][input_row++];
 232     outptr = *output_buf++;
 233     for (col = 0; col < num_cols; col++) {
 234       /* We can dispense with GETJSAMPLE() here */
 235       outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col];
 236       outptr += RGB_PIXELSIZE;
 237     }
 238   }
 239 }
 240
 241
 242 /*
 243  * Adobe-style YCCK->CMYK conversion.
 244  * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same
 245  * conversion as above, while passing K (black) unchanged.
 246  * We assume build_ycc_rgb_table has been called.
 247  */
 248
 249 METHODDEF(void)
 250 ycck_cmyk_convert (j_decompress_ptr cinfo,
 251                    JSAMPIMAGE input_buf, JDIMENSION input_row,
 252                    JSAMPARRAY output_buf, int num_rows)
 253 {
 254   my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert;
 255   register int y, cb, cr;
 256   register JSAMPROW outptr;
 257   register JSAMPROW inptr0, inptr1, inptr2, inptr3;
 258   register JDIMENSION col;
 259   JDIMENSION num_cols = cinfo->output_width;
 260   /* copy these pointers into registers if possible */
 261   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 262   register int * Crrtab = cconvert->Cr_r_tab;
 263   register int * Cbbtab = cconvert->Cb_b_tab;
 264   register JPEG_INT32 * Crgtab = cconvert->Cr_g_tab;
 265   register JPEG_INT32 * Cbgtab = cconvert->Cb_g_tab;
 266   SHIFT_TEMPS
 267
 268   while (--num_rows >= 0) {
 269     inptr0 = input_buf[0][input_row];
 270     inptr1 = input_buf[1][input_row];
 271     inptr2 = input_buf[2][input_row];
 272     inptr3 = input_buf[3][input_row];
 273     input_row++;
 274     outptr = *output_buf++;
 275     for (col = 0; col < num_cols; col++) {
 276       y  = GETJSAMPLE(inptr0[col]);
 277       cb = GETJSAMPLE(inptr1[col]);
 278       cr = GETJSAMPLE(inptr2[col]);
 279       /* Range-limiting is essential due to noise introduced by DCT losses. */
 280       outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])];   /* red */
 281       outptr[1] = range_limit[MAXJSAMPLE - (y +                 /* green */
 282                               ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr],
 283                                                  SCALEBITS)))];
 284       outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])];   /* blue */
 285       /* K passes through unchanged */
 286       outptr[3] = inptr3[col];  /* don't need GETJSAMPLE here */
 287       outptr += 4;
 288     }
 289   }
 290 }
 291
 292
 293 /*
 294  * Empty method for start_pass.
 295  */
 296
 297 METHODDEF(void)
 298 start_pass_dcolor (j_decompress_ptr cinfo)
 299 {
 300   /* no work needed */
 301 }
 302
 303
 304 /*
 305  * Module initialization routine for output colorspace conversion.
 306  */
 307
 308 GLOBAL(void)
 309 jinit_color_deconverter (j_decompress_ptr cinfo)
 310 {
 311   my_cconvert_ptr cconvert;
 312   int ci;
 313
 314   cconvert = (my_cconvert_ptr)
 315     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 316                                 SIZEOF(my_color_deconverter));
 317   cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert;
 318   cconvert->pub.start_pass = start_pass_dcolor;
 319
 320   /* Make sure num_components agrees with jpeg_color_space */
 321   switch (cinfo->jpeg_color_space) {
 322   case JCS_GRAYSCALE:
 323     if (cinfo->num_components != 1)
 324       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 325     break;
 326
 327   case JCS_RGB:
 328   case JCS_YCbCr:
 329     if (cinfo->num_components != 3)
 330       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 331     break;
 332
 333   case JCS_CMYK:
 334   case JCS_YCCK:
 335     if (cinfo->num_components != 4)
 336       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 337     break;
 338
 339   default:                      /* JCS_UNKNOWN can be anything */
 340     if (cinfo->num_components < 1)
 341       ERREXIT(cinfo, JERR_BAD_J_COLORSPACE);
 342     break;
 343   }
 344
 345   /* Set out_color_components and conversion method based on requested space.
 346    * Also clear the component_needed flags for any unused components,
 347    * so that earlier pipeline stages can avoid useless computation.
 348    */
 349
 350   switch (cinfo->out_color_space) {
 351   case JCS_GRAYSCALE:
 352     cinfo->out_color_components = 1;
 353     if (cinfo->jpeg_color_space == JCS_GRAYSCALE ||
 354         cinfo->jpeg_color_space == JCS_YCbCr) {
 355       cconvert->pub.color_convert = grayscale_convert;
 356       /* For color->grayscale conversion, only the Y (0) component is needed */
 357       for (ci = 1; ci < cinfo->num_components; ci++)
 358         cinfo->comp_info[ci].component_needed = FALSE;
 359     } else
 360       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 361     break;
 362
 363   case JCS_RGB:
 364     cinfo->out_color_components = RGB_PIXELSIZE;
 365     if (cinfo->jpeg_color_space == JCS_YCbCr) {
 366       cconvert->pub.color_convert = ycc_rgb_convert;
 367       build_ycc_rgb_table(cinfo);
 368     } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) {
 369       cconvert->pub.color_convert = gray_rgb_convert;
 370     } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) {
 371       cconvert->pub.color_convert = null_convert;
 372     } else
 373       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 374     break;
 375
 376   case JCS_CMYK:
 377     cinfo->out_color_components = 4;
 378     if (cinfo->jpeg_color_space == JCS_YCCK) {
 379       cconvert->pub.color_convert = ycck_cmyk_convert;
 380       build_ycc_rgb_table(cinfo);
 381     } else if (cinfo->jpeg_color_space == JCS_CMYK) {
 382       cconvert->pub.color_convert = null_convert;
 383     } else
 384       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 385     break;
 386
 387   default:
 388     /* Permit null conversion to same output space */
 389     if (cinfo->out_color_space == cinfo->jpeg_color_space) {
 390       cinfo->out_color_components = cinfo->num_components;
 391       cconvert->pub.color_convert = null_convert;
 392     } else                      /* unsupported non-null conversion */
 393       ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
 394     break;
 395   }
 396
 397   if (cinfo->quantize_colors)
 398     cinfo->output_components = 1; /* single colormapped output component */
 399   else
 400     cinfo->output_components = cinfo->out_color_components;
 401 }
 402
 403 #if defined(__VISAGECPP__)
 404 #  ifdef null_convert2
 405 #   undef null_convert2
 406 #  endif
 407 #  ifdef grayscale_convert2
 408 #   undef grayscale_convert2
 409 #  endif
 410 #endif