jdcolor.c (12962B)
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 16 /* Private subobject */ 17 18 typedef struct { 19 struct jpeg_color_deconverter pub; /* public fields */ 20 21 /* Private state for YCC->RGB conversion */ 22 int * Cr_r_tab; /* => table for Cr to R conversion */ 23 int * Cb_b_tab; /* => table for Cb to B conversion */ 24 INT32 * Cr_g_tab; /* => table for Cr to G conversion */ 25 INT32 * Cb_g_tab; /* => table for Cb to G conversion */ 26 } my_color_deconverter; 27 28 typedef my_color_deconverter * my_cconvert_ptr; 29 30 31 /**************** YCbCr -> RGB conversion: most common case **************/ 32 33 /* 34 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are 35 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. 36 * The conversion equations to be implemented are therefore 37 * R = Y + 1.40200 * Cr 38 * G = Y - 0.34414 * Cb - 0.71414 * Cr 39 * B = Y + 1.77200 * Cb 40 * where Cb and Cr represent the incoming values less CENTERJSAMPLE. 41 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) 42 * 43 * To avoid floating-point arithmetic, we represent the fractional constants 44 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide 45 * the products by 2^16, with appropriate rounding, to get the correct answer. 46 * Notice that Y, being an integral input, does not contribute any fraction 47 * so it need not participate in the rounding. 48 * 49 * For even more speed, we avoid doing any multiplications in the inner loop 50 * by precalculating the constants times Cb and Cr for all possible values. 51 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table); 52 * for 12-bit samples it is still acceptable. It's not very reasonable for 53 * 16-bit samples, but if you want lossless storage you shouldn't be changing 54 * colorspace anyway. 55 * The Cr=>R and Cb=>B values can be rounded to integers in advance; the 56 * values for the G calculation are left scaled up, since we must add them 57 * together before rounding. 58 */ 59 60 #define SCALEBITS 16 /* speediest right-shift on some machines */ 61 #define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) 62 #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) 63 64 65 /* 66 * Initialize tables for YCC->RGB colorspace conversion. 67 */ 68 69 LOCAL(void) 70 build_ycc_rgb_table (j_decompress_ptr cinfo) 71 { 72 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 73 int i; 74 INT32 x; 75 SHIFT_TEMPS 76 77 cconvert->Cr_r_tab = (int *) 78 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 79 (MAXJSAMPLE+1) * SIZEOF(int)); 80 cconvert->Cb_b_tab = (int *) 81 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 82 (MAXJSAMPLE+1) * SIZEOF(int)); 83 cconvert->Cr_g_tab = (INT32 *) 84 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 85 (MAXJSAMPLE+1) * SIZEOF(INT32)); 86 cconvert->Cb_g_tab = (INT32 *) 87 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 88 (MAXJSAMPLE+1) * SIZEOF(INT32)); 89 90 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) { 91 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */ 92 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */ 93 /* Cr=>R value is nearest int to 1.40200 * x */ 94 cconvert->Cr_r_tab[i] = (int) 95 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS); 96 /* Cb=>B value is nearest int to 1.77200 * x */ 97 cconvert->Cb_b_tab[i] = (int) 98 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS); 99 /* Cr=>G value is scaled-up -0.71414 * x */ 100 cconvert->Cr_g_tab[i] = (- FIX(0.71414)) * x; 101 /* Cb=>G value is scaled-up -0.34414 * x */ 102 /* We also add in ONE_HALF so that need not do it in inner loop */ 103 cconvert->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF; 104 } 105 } 106 107 108 /* 109 * Convert some rows of samples to the output colorspace. 110 * 111 * Note that we change from noninterleaved, one-plane-per-component format 112 * to interleaved-pixel format. The output buffer is therefore three times 113 * as wide as the input buffer. 114 * A starting row offset is provided only for the input buffer. The caller 115 * can easily adjust the passed output_buf value to accommodate any row 116 * offset required on that side. 117 */ 118 119 METHODDEF(void) 120 ycc_rgb_convert (j_decompress_ptr cinfo, 121 JSAMPIMAGE input_buf, JDIMENSION input_row, 122 JSAMPARRAY output_buf, int num_rows) 123 { 124 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 125 register int y, cb, cr; 126 register JSAMPROW outptr; 127 register JSAMPROW inptr0, inptr1, inptr2; 128 register JDIMENSION col; 129 JDIMENSION num_cols = cinfo->output_width; 130 /* copy these pointers into registers if possible */ 131 register JSAMPLE * range_limit = cinfo->sample_range_limit; 132 register int * Crrtab = cconvert->Cr_r_tab; 133 register int * Cbbtab = cconvert->Cb_b_tab; 134 register INT32 * Crgtab = cconvert->Cr_g_tab; 135 register INT32 * Cbgtab = cconvert->Cb_g_tab; 136 SHIFT_TEMPS 137 138 while (--num_rows >= 0) { 139 inptr0 = input_buf[0][input_row]; 140 inptr1 = input_buf[1][input_row]; 141 inptr2 = input_buf[2][input_row]; 142 input_row++; 143 outptr = *output_buf++; 144 for (col = 0; col < num_cols; col++) { 145 y = GETJSAMPLE(inptr0[col]); 146 cb = GETJSAMPLE(inptr1[col]); 147 cr = GETJSAMPLE(inptr2[col]); 148 /* Range-limiting is essential due to noise introduced by DCT losses. */ 149 outptr[RGB_RED] = range_limit[y + Crrtab[cr]]; 150 outptr[RGB_GREEN] = range_limit[y + 151 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], 152 SCALEBITS))]; 153 outptr[RGB_BLUE] = range_limit[y + Cbbtab[cb]]; 154 outptr += RGB_PIXELSIZE; 155 } 156 } 157 } 158 159 160 /**************** Cases other than YCbCr -> RGB **************/ 161 162 163 /* 164 * Color conversion for no colorspace change: just copy the data, 165 * converting from separate-planes to interleaved representation. 166 */ 167 168 METHODDEF(void) 169 null_convert (j_decompress_ptr cinfo, 170 JSAMPIMAGE input_buf, JDIMENSION input_row, 171 JSAMPARRAY output_buf, int num_rows) 172 { 173 register JSAMPROW inptr, outptr; 174 register JDIMENSION count; 175 register int num_components = cinfo->num_components; 176 JDIMENSION num_cols = cinfo->output_width; 177 int ci; 178 179 while (--num_rows >= 0) { 180 for (ci = 0; ci < num_components; ci++) { 181 inptr = input_buf[ci][input_row]; 182 outptr = output_buf[0] + ci; 183 for (count = num_cols; count > 0; count--) { 184 *outptr = *inptr++; /* needn't bother with GETJSAMPLE() here */ 185 outptr += num_components; 186 } 187 } 188 input_row++; 189 output_buf++; 190 } 191 } 192 193 194 /* 195 * Color conversion for grayscale: just copy the data. 196 * This also works for YCbCr -> grayscale conversion, in which 197 * we just copy the Y (luminance) component and ignore chrominance. 198 */ 199 200 METHODDEF(void) 201 grayscale_convert (j_decompress_ptr cinfo, 202 JSAMPIMAGE input_buf, JDIMENSION input_row, 203 JSAMPARRAY output_buf, int num_rows) 204 { 205 jcopy_sample_rows(input_buf[0], (int) input_row, output_buf, 0, 206 num_rows, cinfo->output_width); 207 } 208 209 210 /* 211 * Convert grayscale to RGB: just duplicate the graylevel three times. 212 * This is provided to support applications that don't want to cope 213 * with grayscale as a separate case. 214 */ 215 216 METHODDEF(void) 217 gray_rgb_convert (j_decompress_ptr cinfo, 218 JSAMPIMAGE input_buf, JDIMENSION input_row, 219 JSAMPARRAY output_buf, int num_rows) 220 { 221 register JSAMPROW inptr, outptr; 222 register JDIMENSION col; 223 JDIMENSION num_cols = cinfo->output_width; 224 225 while (--num_rows >= 0) { 226 inptr = input_buf[0][input_row++]; 227 outptr = *output_buf++; 228 for (col = 0; col < num_cols; col++) { 229 /* We can dispense with GETJSAMPLE() here */ 230 outptr[RGB_RED] = outptr[RGB_GREEN] = outptr[RGB_BLUE] = inptr[col]; 231 outptr += RGB_PIXELSIZE; 232 } 233 } 234 } 235 236 237 /* 238 * Adobe-style YCCK->CMYK conversion. 239 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same 240 * conversion as above, while passing K (black) unchanged. 241 * We assume build_ycc_rgb_table has been called. 242 */ 243 244 METHODDEF(void) 245 ycck_cmyk_convert (j_decompress_ptr cinfo, 246 JSAMPIMAGE input_buf, JDIMENSION input_row, 247 JSAMPARRAY output_buf, int num_rows) 248 { 249 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 250 register int y, cb, cr; 251 register JSAMPROW outptr; 252 register JSAMPROW inptr0, inptr1, inptr2, inptr3; 253 register JDIMENSION col; 254 JDIMENSION num_cols = cinfo->output_width; 255 /* copy these pointers into registers if possible */ 256 register JSAMPLE * range_limit = cinfo->sample_range_limit; 257 register int * Crrtab = cconvert->Cr_r_tab; 258 register int * Cbbtab = cconvert->Cb_b_tab; 259 register INT32 * Crgtab = cconvert->Cr_g_tab; 260 register INT32 * Cbgtab = cconvert->Cb_g_tab; 261 SHIFT_TEMPS 262 263 while (--num_rows >= 0) { 264 inptr0 = input_buf[0][input_row]; 265 inptr1 = input_buf[1][input_row]; 266 inptr2 = input_buf[2][input_row]; 267 inptr3 = input_buf[3][input_row]; 268 input_row++; 269 outptr = *output_buf++; 270 for (col = 0; col < num_cols; col++) { 271 y = GETJSAMPLE(inptr0[col]); 272 cb = GETJSAMPLE(inptr1[col]); 273 cr = GETJSAMPLE(inptr2[col]); 274 /* Range-limiting is essential due to noise introduced by DCT losses. */ 275 outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */ 276 outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */ 277 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], 278 SCALEBITS)))]; 279 outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */ 280 /* K passes through unchanged */ 281 outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */ 282 outptr += 4; 283 } 284 } 285 } 286 287 288 /* 289 * Empty method for start_pass. 290 */ 291 292 METHODDEF(void) 293 start_pass_dcolor (j_decompress_ptr cinfo) 294 { 295 /* no work needed */ 296 } 297 298 299 /* 300 * Module initialization routine for output colorspace conversion. 301 */ 302 303 GLOBAL(void) 304 jinit_color_deconverter (j_decompress_ptr cinfo) 305 { 306 my_cconvert_ptr cconvert; 307 int ci; 308 309 cconvert = (my_cconvert_ptr) 310 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 311 SIZEOF(my_color_deconverter)); 312 cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert; 313 cconvert->pub.start_pass = start_pass_dcolor; 314 315 /* Make sure num_components agrees with jpeg_color_space */ 316 switch (cinfo->jpeg_color_space) { 317 case JCS_GRAYSCALE: 318 if (cinfo->num_components != 1) 319 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 320 break; 321 322 case JCS_RGB: 323 case JCS_YCbCr: 324 if (cinfo->num_components != 3) 325 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 326 break; 327 328 case JCS_CMYK: 329 case JCS_YCCK: 330 if (cinfo->num_components != 4) 331 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 332 break; 333 334 default: /* JCS_UNKNOWN can be anything */ 335 if (cinfo->num_components < 1) 336 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 337 break; 338 } 339 340 /* Set out_color_components and conversion method based on requested space. 341 * Also clear the component_needed flags for any unused components, 342 * so that earlier pipeline stages can avoid useless computation. 343 */ 344 345 switch (cinfo->out_color_space) { 346 case JCS_GRAYSCALE: 347 cinfo->out_color_components = 1; 348 if (cinfo->jpeg_color_space == JCS_GRAYSCALE || 349 cinfo->jpeg_color_space == JCS_YCbCr) { 350 cconvert->pub.color_convert = grayscale_convert; 351 /* For color->grayscale conversion, only the Y (0) component is needed */ 352 for (ci = 1; ci < cinfo->num_components; ci++) 353 cinfo->comp_info[ci].component_needed = FALSE; 354 } else 355 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 356 break; 357 358 case JCS_RGB: 359 cinfo->out_color_components = RGB_PIXELSIZE; 360 if (cinfo->jpeg_color_space == JCS_YCbCr) { 361 cconvert->pub.color_convert = ycc_rgb_convert; 362 build_ycc_rgb_table(cinfo); 363 } else if (cinfo->jpeg_color_space == JCS_GRAYSCALE) { 364 cconvert->pub.color_convert = gray_rgb_convert; 365 } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) { 366 cconvert->pub.color_convert = null_convert; 367 } else 368 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 369 break; 370 371 case JCS_CMYK: 372 cinfo->out_color_components = 4; 373 if (cinfo->jpeg_color_space == JCS_YCCK) { 374 cconvert->pub.color_convert = ycck_cmyk_convert; 375 build_ycc_rgb_table(cinfo); 376 } else if (cinfo->jpeg_color_space == JCS_CMYK) { 377 cconvert->pub.color_convert = null_convert; 378 } else 379 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 380 break; 381 382 default: 383 /* Permit null conversion to same output space */ 384 if (cinfo->out_color_space == cinfo->jpeg_color_space) { 385 cinfo->out_color_components = cinfo->num_components; 386 cconvert->pub.color_convert = null_convert; 387 } else /* unsupported non-null conversion */ 388 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 389 break; 390 } 391 392 if (cinfo->quantize_colors) 393 cinfo->output_components = 1; /* single colormapped output component */ 394 else 395 cinfo->output_components = cinfo->out_color_components; 396 }