1/* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5/* 6 * jdcolor.c 7 * 8 * Copyright (C) 1991-1997, Thomas G. Lane. 9 * This file is part of the Independent JPEG Group's software. 10 * For conditions of distribution and use, see the accompanying README file. 11 * 12 * This file contains output colorspace conversion routines. 13 */ 14 15#define JPEG_INTERNALS 16#include "jinclude.h" 17#include "jpeglib.h" 18 19 20/* Private subobject */ 21 22typedef struct { 23 struct jpeg_color_deconverter pub; /* public fields */ 24 25 /* Private state for YCC->RGB conversion */ 26 int * Cr_r_tab; /* => table for Cr to R conversion */ 27 int * Cb_b_tab; /* => table for Cb to B conversion */ 28 INT32 * Cr_g_tab; /* => table for Cr to G conversion */ 29 INT32 * Cb_g_tab; /* => table for Cb to G conversion */ 30} my_color_deconverter; 31 32typedef my_color_deconverter * my_cconvert_ptr; 33 34 35/**************** YCbCr -> RGB conversion: most common case **************/ 36 37/* 38 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are 39 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. 40 * The conversion equations to be implemented are therefore 41 * R = Y + 1.40200 * Cr 42 * G = Y - 0.34414 * Cb - 0.71414 * Cr 43 * B = Y + 1.77200 * Cb 44 * where Cb and Cr represent the incoming values less CENTERJSAMPLE. 45 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) 46 * 47 * To avoid floating-point arithmetic, we represent the fractional constants 48 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide 49 * the products by 2^16, with appropriate rounding, to get the correct answer. 50 * Notice that Y, being an integral input, does not contribute any fraction 51 * so it need not participate in the rounding. 52 * 53 * For even more speed, we avoid doing any multiplications in the inner loop 54 * by precalculating the constants times Cb and Cr 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 Cr=>R and Cb=>B values can be rounded to integers in advance; the 60 * values for the G calculation are left scaled up, since we must add them 61 * together before rounding. 62 */ 63 64#define SCALEBITS 16 /* speediest right-shift on some machines */ 65#define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) 66#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) 67 68 69/* 70 * Initialize tables for YCC->RGB colorspace conversion. 71 */ 72 73LOCAL(void) 74build_ycc_rgb_table (j_decompress_ptr cinfo) 75{ 76 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 77 int i; 78 INT32 x; 79 SHIFT_TEMPS 80 81 cconvert->Cr_r_tab = (int *) 82 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 83 (MAXJSAMPLE+1) * SIZEOF(int)); 84 cconvert->Cb_b_tab = (int *) 85 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 86 (MAXJSAMPLE+1) * SIZEOF(int)); 87 cconvert->Cr_g_tab = (INT32 *) 88 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 89 (MAXJSAMPLE+1) * SIZEOF(INT32)); 90 cconvert->Cb_g_tab = (INT32 *) 91 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 92 (MAXJSAMPLE+1) * SIZEOF(INT32)); 93 94 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) { 95 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */ 96 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */ 97 /* Cr=>R value is nearest int to 1.40200 * x */ 98 cconvert->Cr_r_tab[i] = (int) 99 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS); 100 /* Cb=>B value is nearest int to 1.77200 * x */ 101 cconvert->Cb_b_tab[i] = (int) 102 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS); 103 /* Cr=>G value is scaled-up -0.71414 * x */ 104 cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x; 105 /* Cb=>G value is scaled-up -0.34414 * x */ 106 /* We also add in ONE_HALF so that need not do it in inner loop */ 107 cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF; 108 } 109} 110 111 112/* 113 * Convert some rows of samples to the output colorspace. 114 * 115 * Note that we change from noninterleaved, one-plane-per-component format 116 * to interleaved-pixel format. The output buffer is therefore three times 117 * as wide as the input buffer. 118 * A starting row offset is provided only for the input buffer. The caller 119 * can easily adjust the passed output_buf value to accommodate any row 120 * offset required on that side. 121 */ 122 123METHODDEF(void) 124ycc_rgb_convert (j_decompress_ptr cinfo, 125 JSAMPIMAGE input_buf, JDIMENSION input_row, 126 JSAMPARRAY output_buf, int num_rows) 127{ 128 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 129 register int y, cb, cr; 130 register JSAMPROW outptr; 131 register JSAMPROW inptr0, inptr1, inptr2; 132 register JDIMENSION col; 133 JDIMENSION num_cols = cinfo->output_width; 134 /* copy these pointers into registers if possible */ 135 register JSAMPLE * range_limit = cinfo->sample_range_limit; 136 register int * Crrtab = cconvert->Cr_r_tab; 137 register int * Cbbtab = cconvert->Cb_b_tab; 138 register INT32 * Crgtab = cconvert->Cr_g_tab; 139 register INT32 * Cbgtab = cconvert->Cb_g_tab; 140 SHIFT_TEMPS 141 142 while (--num_rows >= 0) { 143 inptr0 = input_buf[0][input_row]; 144 inptr1 = input_buf[1][input_row]; 145 inptr2 = input_buf[2][input_row]; 146 input_row++; 147 outptr = *output_buf++; 148 for (col = 0; col < num_cols; col++) { 149 y = GETJSAMPLE(inptr0[col]); 150 cb = GETJSAMPLE(inptr1[col]); 151 cr = GETJSAMPLE(inptr2[col]); 152 /* Range-limiting is essential due to noise introduced by DCT losses. */ 153 outptr[RGB_RED] = range_limit[y + Crrtab[cr]]; 154 outptr[RGB_GREEN] = range_limit[y + 155 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], 156 SCALEBITS))]; 157 outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]]; 158 outptr += RGB_PIXELSIZE; 159 } 160 } 161} 162 163 164/**************** Cases other than YCbCr -> RGB **************/ 165 166 167/* 168 * Color conversion for no colorspace change: just copy the data, 169 * converting from separate-planes to interleaved representation. 170 */ 171 172METHODDEF(void) 173null_convert (j_decompress_ptr cinfo, 174 JSAMPIMAGE input_buf, JDIMENSION input_row, 175 JSAMPARRAY output_buf, int num_rows) 176{ 177 register JSAMPROW inptr, outptr; 178 register JDIMENSION count; 179 register int num_components = cinfo->num_components; 180 JDIMENSION num_cols = cinfo->output_width; 181 int ci; 182 183 while (--num_rows >= 0) { 184 for (ci = 0; ci < num_components; ci++) { 185 inptr = input_buf[ci][input_row]; 186 outptr = output_buf[0] + ci; 187 for (count = num_cols; count > 0; count--) { 188 *outptr = *inptr++; /* needn't bother with GETJSAMPLE() here */ 189 outptr += num_components; 190 } 191 } 192 input_row++; 193 output_buf++; 194 } 195} 196 197 198/* 199 * Color conversion for grayscale: just copy the data. 200 * This also works for YCbCr -> grayscale conversion, in which 201 * we just copy the Y (luminance) component and ignore chrominance. 202 */ 203 204METHODDEF(void) 205grayscale_convert (j_decompress_ptr cinfo, 206 JSAMPIMAGE input_buf, JDIMENSION input_row, 207 JSAMPARRAY output_buf, int num_rows) 208{ 209 jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0, 210 num_rows, cinfo->output_width); 211} 212 213/* 214 * Convert grayscale to RGB: just duplicate the graylevel three times. 215 * This is provided to support applications that don't want to cope 216 * with grayscale as a separate case. 217 */ 218 219METHODDEF(void) 220gray_rgb_convert (j_decompress_ptr cinfo, 221 JSAMPIMAGE input_buf, JDIMENSION input_row, 222 JSAMPARRAY output_buf, int num_rows) 223{ 224 register JSAMPROW inptr, outptr; 225 register JDIMENSION col; 226 JDIMENSION num_cols = cinfo->output_width; 227 228 while (--num_rows >= 0) { 229 inptr = input_buf[0][input_row++]; 230 outptr = *output_buf++; 231 for (col = 0; col < num_cols; col++) { 232 /* We can dispense with GETJSAMPLE() here */ 233 outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col]; 234 outptr += RGB_PIXELSIZE; 235 } 236 } 237} 238 239 240/* 241 * Adobe-style YCCK->CMYK conversion. 242 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same 243 * conversion as above, while passing K (black) unchanged. 244 * We assume build_ycc_rgb_table has been called. 245 */ 246 247METHODDEF(void) 248ycck_cmyk_convert (j_decompress_ptr cinfo, 249 JSAMPIMAGE input_buf, JDIMENSION input_row, 250 JSAMPARRAY output_buf, int num_rows) 251{ 252 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 253 register int y, cb, cr; 254 register JSAMPROW outptr; 255 register JSAMPROW inptr0, inptr1, inptr2, inptr3; 256 register JDIMENSION col; 257 JDIMENSION num_cols = cinfo->output_width; 258 /* copy these pointers into registers if possible */ 259 register JSAMPLE * range_limit = cinfo->sample_range_limit; 260 register int * Crrtab = cconvert->Cr_r_tab; 261 register int * Cbbtab = cconvert->Cb_b_tab; 262 register INT32 * Crgtab = cconvert->Cr_g_tab; 263 register INT32 * Cbgtab = cconvert->Cb_g_tab; 264 SHIFT_TEMPS 265 266 while (--num_rows >= 0) { 267 inptr0 = input_buf[0][input_row]; 268 inptr1 = input_buf[1][input_row]; 269 inptr2 = input_buf[2][input_row]; 270 inptr3 = input_buf[3][input_row]; 271 input_row++; 272 outptr = *output_buf++; 273 for (col = 0; col < num_cols; col++) { 274 y = GETJSAMPLE(inptr0[col]); 275 cb = GETJSAMPLE(inptr1[col]); 276 cr = GETJSAMPLE(inptr2[col]); 277 /* Range-limiting is essential due to noise introduced by DCT losses. */ 278 outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */ 279 outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */ 280 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], 281 SCALEBITS)))]; 282 outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */ 283 /* K passes through unchanged */ 284 outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */ 285 outptr += 4; 286 } 287 } 288} 289 290 291/* 292 * Empty method for start_pass. 293 */ 294 295METHODDEF(void) 296start_pass_dcolor (j_decompress_ptr cinfo) 297{ 298 /* no work needed */ 299} 300 301 302/* 303 * Module initialization routine for output colorspace conversion. 304 */ 305 306GLOBAL(void) 307jinit_color_deconverter (j_decompress_ptr cinfo) 308{ 309 my_cconvert_ptr cconvert; 310 int ci; 311 312 cconvert = (my_cconvert_ptr) 313 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 314 SIZEOF(my_color_deconverter)); 315 cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert; 316 cconvert->pub.start_pass = start_pass_dcolor; 317 318 /* Make sure num_components agrees with jpeg_color_space */ 319 switch (cinfo->jpeg_color_space) { 320 case JCS_GRAYSCALE: 321 if (cinfo->num_components != 1) 322 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 323 break; 324 case JCS_RGB: 325 case JCS_YCbCr: 326 if (cinfo->num_components != 3) 327 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 328 break; 329 330 case JCS_CMYK: 331 case JCS_YCCK: 332 if (cinfo->num_components != 4) 333 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 334 break; 335 336 default: /* JCS_UNKNOWN can be anything */ 337 if (cinfo->num_components < 1) 338 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 339 break; 340 } 341 342 /* Set out_color_components and conversion method based on requested space. 343 * Also clear the component_needed flags for any unused components, 344 * so that earlier pipeline stages can avoid useless computation. 345 */ 346 347 switch (cinfo->out_color_space) { 348 case JCS_GRAYSCALE: 349 cinfo->out_color_components = 1; 350 if (cinfo->jpeg_color_space == JCS_GRAYSCALE || 351 cinfo->jpeg_color_space == JCS_YCbCr) { 352 cconvert->pub.color_convert = grayscale_convert; 353 /* For color->grayscale conversion, only the Y (0) component is needed */ 354 for (ci = 1; ci < cinfo->num_components; ci++) 355 cinfo->comp_info[ci].component_needed = FALSE; 356 } else 357 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 358 break; 359 360 case JCS_RGB: 361 cinfo->out_color_components = RGB_PIXELSIZE; 362 if (cinfo->jpeg_color_space == JCS_YCbCr) { 363 cconvert->pub.color_convert = ycc_rgb_convert; 364 build_ycc_rgb_table(cinfo); 365 } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) { 366 cconvert->pub.color_convert = gray_rgb_convert; 367 } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) { 368 cconvert->pub.color_convert = null_convert; 369 } else 370 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 371 break; 372 373 case JCS_CMYK: 374 cinfo->out_color_components = 4; 375 if (cinfo->jpeg_color_space == JCS_YCCK) { 376 cconvert->pub.color_convert = ycck_cmyk_convert; 377 build_ycc_rgb_table(cinfo); 378 } else if (cinfo->jpeg_color_space == JCS_CMYK) { 379 cconvert->pub.color_convert = null_convert; 380 } else 381 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 382 break; 383 384 default: 385 /* Permit null conversion to same output space */ 386 if (cinfo->out_color_space == cinfo->jpeg_color_space) { 387 cinfo->out_color_components = cinfo->num_components; 388 cconvert->pub.color_convert = null_convert; 389 } else /* unsupported non-null conversion */ 390 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 391 break; 392 } 393 394 if (cinfo->quantize_colors) 395 cinfo->output_components = 1; /* single colormapped output component */ 396 else 397 cinfo->output_components = cinfo->out_color_components; 398} 399