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 23typedef 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 33typedef 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 74LOCAL(void) 75build_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 124METHODDEF(void) 125ycc_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 173METHODDEF(void) 174null_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 205METHODDEF(void) 206grayscale_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 221METHODDEF(void) 222gray_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 249METHODDEF(void) 250ycck_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 297METHODDEF(void) 298start_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 308GLOBAL(void) 309jinit_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 411