jccolor.cpp (17408B)
1 /* 2 * jccolor.c 3 * 4 * Copyright (C) 1991-1994, 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 input 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_converter pub;/* public fields */ 20 21 /* Private state for RGB->YCC conversion */ 22 INT32 * rgb_ycc_tab; /* => table for RGB to YCbCr conversion */ 23 } my_color_converter; 24 25 typedef my_color_converter * my_cconvert_ptr; 26 27 28 /**************** RGB -> YCbCr conversion: most common case **************/ 29 30 /* 31 * YCbCr is defined per CCIR 601-1, except that Cb and Cr are 32 * normalized to the range 0..MAXJSAMPLE rather than -0.5 .. 0.5. 33 * The conversion equations to be implemented are therefore 34 * Y = 0.29900 * R + 0.58700 * G + 0.11400 * B 35 * Cb = -0.16874 * R - 0.33126 * G + 0.50000 * B + CENTERJSAMPLE 36 * Cr = 0.50000 * R - 0.41869 * G - 0.08131 * B + CENTERJSAMPLE 37 * (These numbers are derived from TIFF 6.0 section 21, dated 3-June-92.) 38 * Note: older versions of the IJG code used a zero offset of MAXJSAMPLE/2, 39 * rather than CENTERJSAMPLE, for Cb and Cr. This gave equal positive and 40 * negative swings for Cb/Cr, but meant that grayscale values (Cb=Cr=0) 41 * were not represented exactly. Now we sacrifice exact representation of 42 * maximum red and maximum blue in order to get exact grayscales. 43 * 44 * To avoid floating-point arithmetic, we represent the fractional constants 45 * as integers scaled up by 2^16 (about 4 digits precision); we have to divide 46 * the products by 2^16, with appropriate rounding, to get the correct answer. 47 * 48 * For even more speed, we avoid doing any multiplications in the inner loop 49 * by precalculating the constants times R,G,B for all possible values. 50 * For 8-bit JSAMPLEs this is very reasonable (only 256 entries per table); 51 * for 12-bit samples it is still acceptable. It's not very reasonable for 52 * 16-bit samples, but if you want lossless storage you shouldn't be changing 53 * colorspace anyway. 54 * The CENTERJSAMPLE offsets and the rounding fudge-factor of 0.5 are included 55 * in the tables to save adding them separately in the inner loop. 56 */ 57 58 #define SCALEBITS 16 /* speediest right-shift on some machines */ 59 #define CBCR_OFFSET ( (INT32) CENTERJSAMPLE << SCALEBITS ) 60 #define ONE_HALF ( (INT32) 1 << ( SCALEBITS - 1 ) ) 61 #define FIX( x ) ( (INT32) ( ( x ) * ( 1L << SCALEBITS ) + 0.5 ) ) 62 63 /* We allocate one big table and divide it up into eight parts, instead of 64 * doing eight alloc_small requests. This lets us use a single table base 65 * address, which can be held in a register in the inner loops on many 66 * machines (more than can hold all eight addresses, anyway). 67 */ 68 69 #define R_Y_OFF 0 /* offset to R => Y section */ 70 #define G_Y_OFF ( 1 * ( MAXJSAMPLE + 1 ) ) /* offset to G => Y section */ 71 #define B_Y_OFF ( 2 * ( MAXJSAMPLE + 1 ) ) /* etc. */ 72 #define R_CB_OFF ( 3 * ( MAXJSAMPLE + 1 ) ) 73 #define G_CB_OFF ( 4 * ( MAXJSAMPLE + 1 ) ) 74 #define B_CB_OFF ( 5 * ( MAXJSAMPLE + 1 ) ) 75 #define R_CR_OFF B_CB_OFF /* B=>Cb, R=>Cr are the same */ 76 #define G_CR_OFF ( 6 * ( MAXJSAMPLE + 1 ) ) 77 #define B_CR_OFF ( 7 * ( MAXJSAMPLE + 1 ) ) 78 #define TABLE_SIZE ( 8 * ( MAXJSAMPLE + 1 ) ) 79 80 81 /* 82 * Initialize for RGB->YCC colorspace conversion. 83 */ 84 85 METHODDEF void 86 rgb_ycc_start( j_compress_ptr cinfo ) { 87 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 88 INT32 * rgb_ycc_tab; 89 INT32 i; 90 91 /* Allocate and fill in the conversion tables. */ 92 cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *) 93 ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE, 94 ( TABLE_SIZE * SIZEOF( INT32 ) ) ); 95 96 for ( i = 0; i <= MAXJSAMPLE; i++ ) { 97 rgb_ycc_tab[i + R_Y_OFF] = FIX( 0.29900 ) * i; 98 rgb_ycc_tab[i + G_Y_OFF] = FIX( 0.58700 ) * i; 99 rgb_ycc_tab[i + B_Y_OFF] = FIX( 0.11400 ) * i + ONE_HALF; 100 rgb_ycc_tab[i + R_CB_OFF] = ( -FIX( 0.16874 ) ) * i; 101 rgb_ycc_tab[i + G_CB_OFF] = ( -FIX( 0.33126 ) ) * i; 102 /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr. 103 * This ensures that the maximum output will round to MAXJSAMPLE 104 * not MAXJSAMPLE+1, and thus that we don't have to range-limit. 105 */ 106 rgb_ycc_tab[i + B_CB_OFF] = FIX( 0.50000 ) * i + CBCR_OFFSET + ONE_HALF - 1; 107 /* B=>Cb and R=>Cr tables are the same 108 rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; 109 */ 110 rgb_ycc_tab[i + G_CR_OFF] = ( -FIX( 0.41869 ) ) * i; 111 rgb_ycc_tab[i + B_CR_OFF] = ( -FIX( 0.08131 ) ) * i; 112 } 113 } 114 115 116 /* 117 * Convert some rows of samples to the JPEG colorspace. 118 * 119 * Note that we change from the application's interleaved-pixel format 120 * to our internal noninterleaved, one-plane-per-component format. 121 * The input buffer is therefore three times as wide as the output buffer. 122 * 123 * A starting row offset is provided only for the output buffer. The caller 124 * can easily adjust the passed input_buf value to accommodate any row 125 * offset required on that side. 126 */ 127 128 METHODDEF void 129 rgb_ycc_convert( j_compress_ptr cinfo, 130 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 131 JDIMENSION output_row, int num_rows ) { 132 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 133 register int r, g, b; 134 register INT32 * ctab = cconvert->rgb_ycc_tab; 135 register JSAMPROW inptr; 136 register JSAMPROW outptr0, outptr1, outptr2; 137 register JDIMENSION col; 138 JDIMENSION num_cols = cinfo->image_width; 139 140 while ( --num_rows >= 0 ) { 141 inptr = *input_buf++; 142 outptr0 = output_buf[0][output_row]; 143 outptr1 = output_buf[1][output_row]; 144 outptr2 = output_buf[2][output_row]; 145 output_row++; 146 for ( col = 0; col < num_cols; col++ ) { 147 r = GETJSAMPLE( inptr[RGB_RED] ); 148 g = GETJSAMPLE( inptr[RGB_GREEN] ); 149 b = GETJSAMPLE( inptr[RGB_BLUE] ); 150 inptr += RGB_PIXELSIZE; 151 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations 152 * must be too; we do not need an explicit range-limiting operation. 153 * Hence the value being shifted is never negative, and we don't 154 * need the general RIGHT_SHIFT macro. 155 */ 156 /* Y */ 157 outptr0[col] = (JSAMPLE) 158 ( ( ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF] ) 159 >> SCALEBITS ); 160 /* Cb */ 161 outptr1[col] = (JSAMPLE) 162 ( ( ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] + ctab[b + B_CB_OFF] ) 163 >> SCALEBITS ); 164 /* Cr */ 165 outptr2[col] = (JSAMPLE) 166 ( ( ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] + ctab[b + B_CR_OFF] ) 167 >> SCALEBITS ); 168 } 169 } 170 } 171 172 173 /**************** Cases other than RGB -> YCbCr **************/ 174 175 176 /* 177 * Convert some rows of samples to the JPEG colorspace. 178 * This version handles RGB->grayscale conversion, which is the same 179 * as the RGB->Y portion of RGB->YCbCr. 180 * We assume rgb_ycc_start has been called (we only use the Y tables). 181 */ 182 183 METHODDEF void 184 rgb_gray_convert( j_compress_ptr cinfo, 185 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 186 JDIMENSION output_row, int num_rows ) { 187 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 188 register int r, g, b; 189 register INT32 * ctab = cconvert->rgb_ycc_tab; 190 register JSAMPROW inptr; 191 register JSAMPROW outptr; 192 register JDIMENSION col; 193 JDIMENSION num_cols = cinfo->image_width; 194 195 while ( --num_rows >= 0 ) { 196 inptr = *input_buf++; 197 outptr = output_buf[0][output_row]; 198 output_row++; 199 for ( col = 0; col < num_cols; col++ ) { 200 r = GETJSAMPLE( inptr[RGB_RED] ); 201 g = GETJSAMPLE( inptr[RGB_GREEN] ); 202 b = GETJSAMPLE( inptr[RGB_BLUE] ); 203 inptr += RGB_PIXELSIZE; 204 /* Y */ 205 outptr[col] = (JSAMPLE) 206 ( ( ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF] ) 207 >> SCALEBITS ); 208 } 209 } 210 } 211 212 213 /* 214 * Convert some rows of samples to the JPEG colorspace. 215 * This version handles Adobe-style CMYK->YCCK conversion, 216 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same 217 * conversion as above, while passing K (black) unchanged. 218 * We assume rgb_ycc_start has been called. 219 */ 220 221 METHODDEF void 222 cmyk_ycck_convert( j_compress_ptr cinfo, 223 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 224 JDIMENSION output_row, int num_rows ) { 225 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 226 register int r, g, b; 227 register INT32 * ctab = cconvert->rgb_ycc_tab; 228 register JSAMPROW inptr; 229 register JSAMPROW outptr0, outptr1, outptr2, outptr3; 230 register JDIMENSION col; 231 JDIMENSION num_cols = cinfo->image_width; 232 233 while ( --num_rows >= 0 ) { 234 inptr = *input_buf++; 235 outptr0 = output_buf[0][output_row]; 236 outptr1 = output_buf[1][output_row]; 237 outptr2 = output_buf[2][output_row]; 238 outptr3 = output_buf[3][output_row]; 239 output_row++; 240 for ( col = 0; col < num_cols; col++ ) { 241 r = MAXJSAMPLE - GETJSAMPLE( inptr[0] ); 242 g = MAXJSAMPLE - GETJSAMPLE( inptr[1] ); 243 b = MAXJSAMPLE - GETJSAMPLE( inptr[2] ); 244 /* K passes through as-is */ 245 outptr3[col] = inptr[3];/* don't need GETJSAMPLE here */ 246 inptr += 4; 247 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations 248 * must be too; we do not need an explicit range-limiting operation. 249 * Hence the value being shifted is never negative, and we don't 250 * need the general RIGHT_SHIFT macro. 251 */ 252 /* Y */ 253 outptr0[col] = (JSAMPLE) 254 ( ( ctab[r + R_Y_OFF] + ctab[g + G_Y_OFF] + ctab[b + B_Y_OFF] ) 255 >> SCALEBITS ); 256 /* Cb */ 257 outptr1[col] = (JSAMPLE) 258 ( ( ctab[r + R_CB_OFF] + ctab[g + G_CB_OFF] + ctab[b + B_CB_OFF] ) 259 >> SCALEBITS ); 260 /* Cr */ 261 outptr2[col] = (JSAMPLE) 262 ( ( ctab[r + R_CR_OFF] + ctab[g + G_CR_OFF] + ctab[b + B_CR_OFF] ) 263 >> SCALEBITS ); 264 } 265 } 266 } 267 268 269 /* 270 * Convert some rows of samples to the JPEG colorspace. 271 * This version handles grayscale output with no conversion. 272 * The source can be either plain grayscale or YCbCr (since Y == gray). 273 */ 274 275 METHODDEF void 276 grayscale_convert( j_compress_ptr cinfo, 277 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 278 JDIMENSION output_row, int num_rows ) { 279 register JSAMPROW inptr; 280 register JSAMPROW outptr; 281 register JDIMENSION col; 282 JDIMENSION num_cols = cinfo->image_width; 283 int instride = cinfo->input_components; 284 285 while ( --num_rows >= 0 ) { 286 inptr = *input_buf++; 287 outptr = output_buf[0][output_row]; 288 output_row++; 289 for ( col = 0; col < num_cols; col++ ) { 290 outptr[col] = inptr[0];/* don't need GETJSAMPLE() here */ 291 inptr += instride; 292 } 293 } 294 } 295 296 297 /* 298 * Convert some rows of samples to the JPEG colorspace. 299 * This version handles multi-component colorspaces without conversion. 300 * We assume input_components == num_components. 301 */ 302 303 METHODDEF void 304 null_convert( j_compress_ptr cinfo, 305 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 306 JDIMENSION output_row, int num_rows ) { 307 register JSAMPROW inptr; 308 register JSAMPROW outptr; 309 register JDIMENSION col; 310 register int ci; 311 int nc = cinfo->num_components; 312 JDIMENSION num_cols = cinfo->image_width; 313 314 while ( --num_rows >= 0 ) { 315 /* It seems fastest to make a separate pass for each component. */ 316 for ( ci = 0; ci < nc; ci++ ) { 317 inptr = *input_buf; 318 outptr = output_buf[ci][output_row]; 319 for ( col = 0; col < num_cols; col++ ) { 320 outptr[col] = inptr[ci];/* don't need GETJSAMPLE() here */ 321 inptr += nc; 322 } 323 } 324 input_buf++; 325 output_row++; 326 } 327 } 328 329 330 /* 331 * Empty method for start_pass. 332 */ 333 334 METHODDEF void 335 null_method( j_compress_ptr cinfo ) { 336 /* no work needed */ 337 } 338 339 340 /* 341 * Module initialization routine for input colorspace conversion. 342 */ 343 344 GLOBAL void 345 jinit_color_converter( j_compress_ptr cinfo ) { 346 my_cconvert_ptr cconvert; 347 348 cconvert = (my_cconvert_ptr) 349 ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE, 350 SIZEOF( my_color_converter ) ); 351 cinfo->cconvert = (struct jpeg_color_converter *) cconvert; 352 /* set start_pass to null method until we find out differently */ 353 cconvert->pub.start_pass = null_method; 354 355 /* Make sure input_components agrees with in_color_space */ 356 switch ( cinfo->in_color_space ) { 357 case JCS_GRAYSCALE: 358 if ( cinfo->input_components != 1 ) { 359 ERREXIT( cinfo, JERR_BAD_IN_COLORSPACE ); 360 } 361 break; 362 363 case JCS_RGB: 364 #if RGB_PIXELSIZE != 3 365 if ( cinfo->input_components != RGB_PIXELSIZE ) { 366 ERREXIT( cinfo, JERR_BAD_IN_COLORSPACE ); 367 } 368 break; 369 #endif /* else share code with YCbCr */ 370 371 case JCS_YCbCr: 372 if ( cinfo->input_components != 3 ) { 373 ERREXIT( cinfo, JERR_BAD_IN_COLORSPACE ); 374 } 375 break; 376 377 case JCS_CMYK: 378 case JCS_YCCK: 379 if ( cinfo->input_components != 4 ) { 380 ERREXIT( cinfo, JERR_BAD_IN_COLORSPACE ); 381 } 382 break; 383 384 default: /* JCS_UNKNOWN can be anything */ 385 if ( cinfo->input_components < 1 ) { 386 ERREXIT( cinfo, JERR_BAD_IN_COLORSPACE ); 387 } 388 break; 389 } 390 391 /* Check num_components, set conversion method based on requested space */ 392 switch ( cinfo->jpeg_color_space ) { 393 case JCS_GRAYSCALE: 394 if ( cinfo->num_components != 1 ) { 395 ERREXIT( cinfo, JERR_BAD_J_COLORSPACE ); 396 } 397 if ( cinfo->in_color_space == JCS_GRAYSCALE ) { 398 cconvert->pub.color_convert = grayscale_convert; 399 } else if ( cinfo->in_color_space == JCS_RGB ) { 400 cconvert->pub.start_pass = rgb_ycc_start; 401 cconvert->pub.color_convert = rgb_gray_convert; 402 } else if ( cinfo->in_color_space == JCS_YCbCr ) { 403 cconvert->pub.color_convert = grayscale_convert; 404 } else { 405 ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL ); 406 } 407 break; 408 409 case JCS_RGB: 410 if ( cinfo->num_components != 3 ) { 411 ERREXIT( cinfo, JERR_BAD_J_COLORSPACE ); 412 } 413 if ( ( cinfo->in_color_space == JCS_RGB ) && ( RGB_PIXELSIZE == 3 ) ) { 414 cconvert->pub.color_convert = null_convert; 415 } else { 416 ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL ); 417 } 418 break; 419 420 case JCS_YCbCr: 421 if ( cinfo->num_components != 3 ) { 422 ERREXIT( cinfo, JERR_BAD_J_COLORSPACE ); 423 } 424 if ( cinfo->in_color_space == JCS_RGB ) { 425 cconvert->pub.start_pass = rgb_ycc_start; 426 cconvert->pub.color_convert = rgb_ycc_convert; 427 } else if ( cinfo->in_color_space == JCS_YCbCr ) { 428 cconvert->pub.color_convert = null_convert; 429 } else { 430 ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL ); 431 } 432 break; 433 434 case JCS_CMYK: 435 if ( cinfo->num_components != 4 ) { 436 ERREXIT( cinfo, JERR_BAD_J_COLORSPACE ); 437 } 438 if ( cinfo->in_color_space == JCS_CMYK ) { 439 cconvert->pub.color_convert = null_convert; 440 } else { 441 ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL ); 442 } 443 break; 444 445 case JCS_YCCK: 446 if ( cinfo->num_components != 4 ) { 447 ERREXIT( cinfo, JERR_BAD_J_COLORSPACE ); 448 } 449 if ( cinfo->in_color_space == JCS_CMYK ) { 450 cconvert->pub.start_pass = rgb_ycc_start; 451 cconvert->pub.color_convert = cmyk_ycck_convert; 452 } else if ( cinfo->in_color_space == JCS_YCCK ) { 453 cconvert->pub.color_convert = null_convert; 454 } else { 455 ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL ); 456 } 457 break; 458 459 default: /* allow null conversion of JCS_UNKNOWN */ 460 if ( ( cinfo->jpeg_color_space != cinfo->in_color_space ) || 461 ( cinfo->num_components != cinfo->input_components ) ) { 462 ERREXIT( cinfo, JERR_CONVERSION_NOTIMPL ); 463 } 464 cconvert->pub.color_convert = null_convert; 465 break; 466 } 467 }