1/* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5/* 6 * jccolor.c 7 * 8 * Copyright (C) 1991-1996, 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 input 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_converter pub; /* public fields */ 24 25 /* Private state for RGB->YCC conversion */ 26 INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */ 27} my_color_converter; 28 29typedef my_color_converter * my_cconvert_ptr; 30 31 32/**************** RGB -> YCbCr conversion: most common case **************/ 33 34/* 35 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are 36 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. 37 * The conversion equations to be implemented are therefore 38 * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B 39 * Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE 40 * Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE 41 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) 42 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2, 43 * rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and 44 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0) 45 * were not represented exactly. Now we sacrifice exact representation of 46 * maximum red and maximum blue in order to get exact grayscales. 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 * 52 * For even more speed, we avoid doing any multiplications in the inner loop 53 * by precalculating the constants times R,G,B for all possible values. 54 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table); 55 * for 12-bit samples it is still acceptable. It's not very reasonable for 56 * 16-bit samples, but if you want lossless storage you shouldn't be changing 57 * colorspace anyway. 58 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included 59 * in the tables to save adding them separately in the inner loop. 60 */ 61 62#define SCALEBITS 16 /* speediest right-shift on some machines */ 63#define CBCR_OFFSET ((INT32) CENTERJSAMPLE << SCALEBITS) 64#define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) 65#define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) 66 67/* We allocate one big table and divide it up into eight parts, instead of 68 * doing eight alloc_small requests. This lets us use a single table base 69 * address, which can be held in a register in the inner loops on many 70 * machines (more than can hold all eight addresses, anyway). 71 */ 72 73#define R_Y_OFF 0 /* offset to R => Y section */ 74#define G_Y_OFF (1*(MAXJSAMPLE+1)) /* offset to G => Y section */ 75#define B_Y_OFF (2*(MAXJSAMPLE+1)) /* etc. */ 76#define R_CB_OFF (3*(MAXJSAMPLE+1)) 77#define G_CB_OFF (4*(MAXJSAMPLE+1)) 78#define B_CB_OFF (5*(MAXJSAMPLE+1)) 79#define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */ 80#define G_CR_OFF (6*(MAXJSAMPLE+1)) 81#define B_CR_OFF (7*(MAXJSAMPLE+1)) 82#define TABLE_SIZE (8*(MAXJSAMPLE+1)) 83 84 85/* 86 * Initialize for RGB->YCC colorspace conversion. 87 */ 88 89METHODDEF(void) 90rgb_ycc_start (j_compress_ptr cinfo) 91{ 92 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 93 INT32 * rgb_ycc_tab; 94 INT32 i; 95 96 /* Allocate and fill in the conversion tables. */ 97 cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *) 98 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 99 (TABLE_SIZE * SIZEOF(INT32))); 100 101 for (i = 0; i <= MAXJSAMPLE; i++) { 102 rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i; 103 rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i; 104 rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF; 105 rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i; 106 rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i; 107 /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr. 108 * This ensures that the maximum output will round to MAXJSAMPLE 109 * not MAXJSAMPLE+1, and thus that we don't have to range-limit. 110 */ 111 rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; 112/* B=>Cb and R=>Cr tables are the same 113 rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; 114*/ 115 rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i; 116 rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i; 117 } 118} 119 120 121/* 122 * Convert some rows of samples to the JPEG colorspace. 123 * 124 * Note that we change from the application's interleaved-pixel format 125 * to our internal noninterleaved, one-plane-per-component format. 126 * The input buffer is therefore three times as wide as the output buffer. 127 * 128 * A starting row offset is provided only for the output buffer. The caller 129 * can easily adjust the passed input_buf value to accommodate any row 130 * offset required on that side. 131 */ 132 133METHODDEF(void) 134rgb_ycc_convert (j_compress_ptr cinfo, 135 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 136 JDIMENSION output_row, int num_rows) 137{ 138 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 139 register int r, g, b; 140 register INT32 * ctab = cconvert->rgb_ycc_tab; 141 register JSAMPROW inptr; 142 register JSAMPROW outptr0, outptr1, outptr2; 143 register JDIMENSION col; 144 JDIMENSION num_cols = cinfo->image_width; 145 146 while (--num_rows >= 0) { 147 inptr = *input_buf++; 148 outptr0 = output_buf[0][output_row]; 149 outptr1 = output_buf[1][output_row]; 150 outptr2 = output_buf[2][output_row]; 151 output_row++; 152 for (col = 0; col < num_cols; col++) { 153 r = GETJSAMPLE(inptr[RGB_RED]); 154 g = GETJSAMPLE(inptr[RGB_GREEN]); 155 b = GETJSAMPLE(inptr[RGB_BLUE]); 156 inptr += RGB_PIXELSIZE; 157 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations 158 * must be too; we do not need an explicit range-limiting operation. 159 * Hence the value being shifted is never negative, and we don't 160 * need the general RIGHT_SHIFT macro. 161 */ 162 /* Y */ 163 outptr0[col] = (JSAMPLE) 164 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) 165 >> SCALEBITS); 166 /* Cb */ 167 outptr1[col] = (JSAMPLE) 168 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) 169 >> SCALEBITS); 170 /* Cr */ 171 outptr2[col] = (JSAMPLE) 172 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) 173 >> SCALEBITS); 174 } 175 } 176} 177 178 179/**************** Cases other than RGB -> YCbCr **************/ 180 181 182/* 183 * Convert some rows of samples to the JPEG colorspace. 184 * This version handles RGB->grayscale conversion, which is the same 185 * as the RGB->Y portion of RGB->YCbCr. 186 * We assume rgb_ycc_start has been called (we only use the Y tables). 187 */ 188 189METHODDEF(void) 190rgb_gray_convert (j_compress_ptr cinfo, 191 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 192 JDIMENSION output_row, int num_rows) 193{ 194 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 195 register int r, g, b; 196 register INT32 * ctab = cconvert->rgb_ycc_tab; 197 register JSAMPROW inptr; 198 register JSAMPROW outptr; 199 register JDIMENSION col; 200 JDIMENSION num_cols = cinfo->image_width; 201 202 while (--num_rows >= 0) { 203 inptr = *input_buf++; 204 outptr = output_buf[0][output_row]; 205 output_row++; 206 for (col = 0; col < num_cols; col++) { 207 r = GETJSAMPLE(inptr[RGB_RED]); 208 g = GETJSAMPLE(inptr[RGB_GREEN]); 209 b = GETJSAMPLE(inptr[RGB_BLUE]); 210 inptr += RGB_PIXELSIZE; 211 /* Y */ 212 outptr[col] = (JSAMPLE) 213 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) 214 >> SCALEBITS); 215 } 216 } 217} 218 219/* 220 * Convert some rows of samples to the JPEG colorspace. 221 * This version handles Adobe-style CMYK->YCCK conversion, 222 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same 223 * conversion as above, while passing K (black) unchanged. 224 * We assume rgb_ycc_start has been called. 225 */ 226 227METHODDEF(void) 228cmyk_ycck_convert (j_compress_ptr cinfo, 229 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 230 JDIMENSION output_row, int num_rows) 231{ 232 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 233 register int r, g, b; 234 register INT32 * ctab = cconvert->rgb_ycc_tab; 235 register JSAMPROW inptr; 236 register JSAMPROW outptr0, outptr1, outptr2, outptr3; 237 register JDIMENSION col; 238 JDIMENSION num_cols = cinfo->image_width; 239 240 while (--num_rows >= 0) { 241 inptr = *input_buf++; 242 outptr0 = output_buf[0][output_row]; 243 outptr1 = output_buf[1][output_row]; 244 outptr2 = output_buf[2][output_row]; 245 outptr3 = output_buf[3][output_row]; 246 output_row++; 247 for (col = 0; col < num_cols; col++) { 248 r = MAXJSAMPLE - GETJSAMPLE(inptr[0]); 249 g = MAXJSAMPLE - GETJSAMPLE(inptr[1]); 250 b = MAXJSAMPLE - GETJSAMPLE(inptr[2]); 251 /* K passes through as-is */ 252 outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */ 253 inptr += 4; 254 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations 255 * must be too; we do not need an explicit range-limiting operation. 256 * Hence the value being shifted is never negative, and we don't 257 * need the general RIGHT_SHIFT macro. 258 */ 259 /* Y */ 260 outptr0[col] = (JSAMPLE) 261 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) 262 >> SCALEBITS); 263 /* Cb */ 264 outptr1[col] = (JSAMPLE) 265 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) 266 >> SCALEBITS); 267 /* Cr */ 268 outptr2[col] = (JSAMPLE) 269 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) 270 >> SCALEBITS); 271 } 272 } 273} 274 275 276/* 277 * Convert some rows of samples to the JPEG colorspace. 278 * This version handles grayscale output with no conversion. 279 * The source can be either plain grayscale or YCbCr (since Y == gray). 280 */ 281 282METHODDEF(void) 283grayscale_convert (j_compress_ptr cinfo, 284 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 285 JDIMENSION output_row, int num_rows) 286{ 287 register JSAMPROW inptr; 288 register JSAMPROW outptr; 289 register JDIMENSION col; 290 JDIMENSION num_cols = cinfo->image_width; 291 int instride = cinfo->input_components; 292 293 while (--num_rows >= 0) { 294 inptr = *input_buf++; 295 outptr = output_buf[0][output_row]; 296 output_row++; 297 for (col = 0; col < num_cols; col++) { 298 outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */ 299 inptr += instride; 300 } 301 } 302} 303 304 305/* 306 * Convert some rows of samples to the JPEG colorspace. 307 * This version handles multi-component colorspaces without conversion. 308 * We assume input_components == num_components. 309 */ 310 311METHODDEF(void) 312null_convert (j_compress_ptr cinfo, 313 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 314 JDIMENSION output_row, int num_rows) 315{ 316 register JSAMPROW inptr; 317 register JSAMPROW outptr; 318 register JDIMENSION col; 319 register int ci; 320 int nc = cinfo->num_components; 321 JDIMENSION num_cols = cinfo->image_width; 322 323 while (--num_rows >= 0) { 324 /* It seems fastest to make a separate pass for each component. */ 325 for (ci = 0; ci < nc; ci++) { 326 inptr = *input_buf; 327 outptr = output_buf[ci][output_row]; 328 for (col = 0; col < num_cols; col++) { 329 outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */ 330 inptr += nc; 331 } 332 } 333 input_buf++; 334 output_row++; 335 } 336} 337 338 339/* 340 * Empty method for start_pass. 341 */ 342 343METHODDEF(void) 344null_method (j_compress_ptr cinfo) 345{ 346 /* no work needed */ 347} 348 349 350/* 351 * Module initialization routine for input colorspace conversion. 352 */ 353 354GLOBAL(void) 355jinit_color_converter (j_compress_ptr cinfo) 356{ 357 my_cconvert_ptr cconvert; 358 359 cconvert = (my_cconvert_ptr) 360 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 361 SIZEOF(my_color_converter)); 362 cinfo->cconvert = (struct jpeg_color_converter *) cconvert; 363 /* set start_pass to null method until we find out differently */ 364 cconvert->pub.start_pass = null_method; 365 366 /* Make sure input_components agrees with in_color_space */ 367 switch (cinfo->in_color_space) { 368 case JCS_GRAYSCALE: 369 if (cinfo->input_components != 1) 370 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 371 break; 372 373 case JCS_RGB: 374#if RGB_PIXELSIZE != 3 375 if (cinfo->input_components != RGB_PIXELSIZE) 376 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 377 break; 378#endif /* else share code with YCbCr */ 379 380 case JCS_YCbCr: 381 if (cinfo->input_components != 3) 382 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 383 break; 384 385 case JCS_CMYK: 386 case JCS_YCCK: 387 if (cinfo->input_components != 4) 388 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 389 break; 390 391 default: /* JCS_UNKNOWN can be anything */ 392 if (cinfo->input_components < 1) 393 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 394 break; 395 } 396 397 /* Check num_components, set conversion method based on requested space */ 398 switch (cinfo->jpeg_color_space) { 399 case JCS_GRAYSCALE: 400 if (cinfo->num_components != 1) 401 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 402 if (cinfo->in_color_space == JCS_GRAYSCALE) 403 cconvert->pub.color_convert = grayscale_convert; 404 else if (cinfo->in_color_space == JCS_RGB) { 405 cconvert->pub.start_pass = rgb_ycc_start; 406 cconvert->pub.color_convert = rgb_gray_convert; 407 } else if (cinfo->in_color_space == JCS_YCbCr) 408 cconvert->pub.color_convert = grayscale_convert; 409 else 410 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 411 break; 412 413 case JCS_RGB: 414 if (cinfo->num_components != 3) 415 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 416 if (cinfo->in_color_space == JCS_RGB && RGB_PIXELSIZE == 3) 417 cconvert->pub.color_convert = null_convert; 418 else 419 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 420 break; 421 422 case JCS_YCbCr: 423 if (cinfo->num_components != 3) 424 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 425 if (cinfo->in_color_space == JCS_RGB) { 426 cconvert->pub.start_pass = rgb_ycc_start; 427 cconvert->pub.color_convert = rgb_ycc_convert; 428 } else if (cinfo->in_color_space == JCS_YCbCr) 429 cconvert->pub.color_convert = null_convert; 430 else 431 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 432 break; 433 434 case JCS_CMYK: 435 if (cinfo->num_components != 4) 436 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 437 if (cinfo->in_color_space == JCS_CMYK) 438 cconvert->pub.color_convert = null_convert; 439 else 440 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 441 break; 442 443 case JCS_YCCK: 444 if (cinfo->num_components != 4) 445 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 446 if (cinfo->in_color_space == JCS_CMYK) { 447 cconvert->pub.start_pass = rgb_ycc_start; 448 cconvert->pub.color_convert = cmyk_ycck_convert; 449 } else if (cinfo->in_color_space == JCS_YCCK) 450 cconvert->pub.color_convert = null_convert; 451 else 452 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 453 break; 454 455 default: /* allow null conversion of JCS_UNKNOWN */ 456 if (cinfo->jpeg_color_space != cinfo->in_color_space || 457 cinfo->num_components != cinfo->input_components) 458 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 459 cconvert->pub.color_convert = null_convert; 460 break; 461 } 462} 463