1 /* 2 * jccolor.c 3 * 4 * Copyright (C) 1991-1996, 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 { 88 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 89 INT32 * rgb_ycc_tab; 90 INT32 i; 91 92 /* Allocate and fill in the conversion tables. */ 93 cconvert->rgb_ycc_tab = rgb_ycc_tab = (INT32 *) 94 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 95 (TABLE_SIZE * SIZEOF(INT32))); 96 97 for (i = 0; i <= MAXJSAMPLE; i++) { 98 rgb_ycc_tab[i+R_Y_OFF] = FIX(0.29900) * i; 99 rgb_ycc_tab[i+G_Y_OFF] = FIX(0.58700) * i; 100 rgb_ycc_tab[i+B_Y_OFF] = FIX(0.11400) * i + ONE_HALF; 101 rgb_ycc_tab[i+R_CB_OFF] = (-FIX(0.16874)) * i; 102 rgb_ycc_tab[i+G_CB_OFF] = (-FIX(0.33126)) * i; 103 /* We use a rounding fudge-factor of 0.5-epsilon for Cb and Cr. 104 * This ensures that the maximum output will round to MAXJSAMPLE 105 * not MAXJSAMPLE+1, and thus that we don't have to range-limit. 106 */ 107 rgb_ycc_tab[i+B_CB_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; 108 /* B=>Cb and R=>Cr tables are the same 109 rgb_ycc_tab[i+R_CR_OFF] = FIX(0.50000) * i + CBCR_OFFSET + ONE_HALF-1; 110 */ 111 rgb_ycc_tab[i+G_CR_OFF] = (-FIX(0.41869)) * i; 112 rgb_ycc_tab[i+B_CR_OFF] = (-FIX(0.08131)) * i; 113 } 114 } 115 116 117 /* 118 * Convert some rows of samples to the JPEG colorspace. 119 * 120 * Note that we change from the application's interleaved-pixel format 121 * to our internal noninterleaved, one-plane-per-component format. 122 * The input buffer is therefore three times as wide as the output buffer. 123 * 124 * A starting row offset is provided only for the output buffer. The caller 125 * can easily adjust the passed input_buf value to accommodate any row 126 * offset required on that side. 127 */ 128 129 METHODDEF(void) 130 rgb_ycc_convert (j_compress_ptr cinfo, 131 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 132 JDIMENSION output_row, int num_rows) 133 { 134 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 135 register int r, g, b; 136 register INT32 * ctab = cconvert->rgb_ycc_tab; 137 register JSAMPROW inptr; 138 register JSAMPROW outptr0, outptr1, outptr2; 139 register JDIMENSION col; 140 JDIMENSION num_cols = cinfo->image_width; 141 142 while (--num_rows >= 0) { 143 inptr = *input_buf++; 144 outptr0 = output_buf[0][output_row]; 145 outptr1 = output_buf[1][output_row]; 146 outptr2 = output_buf[2][output_row]; 147 output_row++; 148 for (col = 0; col < num_cols; col++) { 149 r = GETJSAMPLE(inptr[RGB_RED]); 150 g = GETJSAMPLE(inptr[RGB_GREEN]); 151 b = GETJSAMPLE(inptr[RGB_BLUE]); 152 inptr += RGB_PIXELSIZE; 153 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations 154 * must be too; we do not need an explicit range-limiting operation. 155 * Hence the value being shifted is never negative, and we don't 156 * need the general RIGHT_SHIFT macro. 157 */ 158 /* Y */ 159 outptr0[col] = (JSAMPLE) 160 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) 161 >> SCALEBITS); 162 /* Cb */ 163 outptr1[col] = (JSAMPLE) 164 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) 165 >> SCALEBITS); 166 /* Cr */ 167 outptr2[col] = (JSAMPLE) 168 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) 169 >> SCALEBITS); 170 } 171 } 172 } 173 174 175 /**************** Cases other than RGB -> YCbCr **************/ 176 177 178 /* 179 * Convert some rows of samples to the JPEG colorspace. 180 * This version handles RGB->grayscale conversion, which is the same 181 * as the RGB->Y portion of RGB->YCbCr. 182 * We assume rgb_ycc_start has been called (we only use the Y tables). 183 */ 184 185 METHODDEF(void) 186 rgb_gray_convert (j_compress_ptr cinfo, 187 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 188 JDIMENSION output_row, int num_rows) 189 { 190 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 191 register int r, g, b; 192 register INT32 * ctab = cconvert->rgb_ycc_tab; 193 register JSAMPROW inptr; 194 register JSAMPROW outptr; 195 register JDIMENSION col; 196 JDIMENSION num_cols = cinfo->image_width; 197 198 while (--num_rows >= 0) { 199 inptr = *input_buf++; 200 outptr = output_buf[0][output_row]; 201 output_row++; 202 for (col = 0; col < num_cols; col++) { 203 r = GETJSAMPLE(inptr[RGB_RED]); 204 g = GETJSAMPLE(inptr[RGB_GREEN]); 205 b = GETJSAMPLE(inptr[RGB_BLUE]); 206 inptr += RGB_PIXELSIZE; 207 /* Y */ 208 outptr[col] = (JSAMPLE) 209 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) 210 >> SCALEBITS); 211 } 212 } 213 } 214 215 216 /* 217 * Convert some rows of samples to the JPEG colorspace. 218 * This version handles Adobe-style CMYK->YCCK conversion, 219 * where we convert R=1-C, G=1-M, and B=1-Y to YCbCr using the same 220 * conversion as above, while passing K (black) unchanged. 221 * We assume rgb_ycc_start has been called. 222 */ 223 224 METHODDEF(void) 225 cmyk_ycck_convert (j_compress_ptr cinfo, 226 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 227 JDIMENSION output_row, int num_rows) 228 { 229 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 230 register int r, g, b; 231 register INT32 * ctab = cconvert->rgb_ycc_tab; 232 register JSAMPROW inptr; 233 register JSAMPROW outptr0, outptr1, outptr2, outptr3; 234 register JDIMENSION col; 235 JDIMENSION num_cols = cinfo->image_width; 236 237 while (--num_rows >= 0) { 238 inptr = *input_buf++; 239 outptr0 = output_buf[0][output_row]; 240 outptr1 = output_buf[1][output_row]; 241 outptr2 = output_buf[2][output_row]; 242 outptr3 = output_buf[3][output_row]; 243 output_row++; 244 for (col = 0; col < num_cols; col++) { 245 r = MAXJSAMPLE - GETJSAMPLE(inptr[0]); 246 g = MAXJSAMPLE - GETJSAMPLE(inptr[1]); 247 b = MAXJSAMPLE - GETJSAMPLE(inptr[2]); 248 /* K passes through as-is */ 249 outptr3[col] = inptr[3]; /* don't need GETJSAMPLE here */ 250 inptr += 4; 251 /* If the inputs are 0..MAXJSAMPLE, the outputs of these equations 252 * must be too; we do not need an explicit range-limiting operation. 253 * Hence the value being shifted is never negative, and we don't 254 * need the general RIGHT_SHIFT macro. 255 */ 256 /* Y */ 257 outptr0[col] = (JSAMPLE) 258 ((ctab[r+R_Y_OFF] + ctab[g+G_Y_OFF] + ctab[b+B_Y_OFF]) 259 >> SCALEBITS); 260 /* Cb */ 261 outptr1[col] = (JSAMPLE) 262 ((ctab[r+R_CB_OFF] + ctab[g+G_CB_OFF] + ctab[b+B_CB_OFF]) 263 >> SCALEBITS); 264 /* Cr */ 265 outptr2[col] = (JSAMPLE) 266 ((ctab[r+R_CR_OFF] + ctab[g+G_CR_OFF] + ctab[b+B_CR_OFF]) 267 >> SCALEBITS); 268 } 269 } 270 } 271 272 273 /* 274 * Convert some rows of samples to the JPEG colorspace. 275 * This version handles grayscale output with no conversion. 276 * The source can be either plain grayscale or YCbCr (since Y == gray). 277 */ 278 279 METHODDEF(void) 280 grayscale_convert (j_compress_ptr cinfo, 281 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 282 JDIMENSION output_row, int num_rows) 283 { 284 register JSAMPROW inptr; 285 register JSAMPROW outptr; 286 register JDIMENSION col; 287 JDIMENSION num_cols = cinfo->image_width; 288 int instride = cinfo->input_components; 289 290 while (--num_rows >= 0) { 291 inptr = *input_buf++; 292 outptr = output_buf[0][output_row]; 293 output_row++; 294 for (col = 0; col < num_cols; col++) { 295 outptr[col] = inptr[0]; /* don't need GETJSAMPLE() here */ 296 inptr += instride; 297 } 298 } 299 } 300 301 302 /* 303 * Convert some rows of samples to the JPEG colorspace. 304 * This version handles multi-component colorspaces without conversion. 305 * We assume input_components == num_components. 306 */ 307 308 METHODDEF(void) 309 null_convert (j_compress_ptr cinfo, 310 JSAMPARRAY input_buf, JSAMPIMAGE output_buf, 311 JDIMENSION output_row, int num_rows) 312 { 313 register JSAMPROW inptr; 314 register JSAMPROW outptr; 315 register JDIMENSION col; 316 register int ci; 317 int nc = cinfo->num_components; 318 JDIMENSION num_cols = cinfo->image_width; 319 320 while (--num_rows >= 0) { 321 /* It seems fastest to make a separate pass for each component. */ 322 for (ci = 0; ci < nc; ci++) { 323 inptr = *input_buf; 324 outptr = output_buf[ci][output_row]; 325 for (col = 0; col < num_cols; col++) { 326 outptr[col] = inptr[ci]; /* don't need GETJSAMPLE() here */ 327 inptr += nc; 328 } 329 } 330 input_buf++; 331 output_row++; 332 } 333 } 334 335 336 /* 337 * Empty method for start_pass. 338 */ 339 340 METHODDEF(void) 341 null_method (j_compress_ptr cinfo) 342 { 343 /* no work needed */ 344 } 345 346 347 /* 348 * Module initialization routine for input colorspace conversion. 349 */ 350 351 GLOBAL(void) 352 jinit_color_converter (j_compress_ptr cinfo) 353 { 354 my_cconvert_ptr cconvert; 355 356 cconvert = (my_cconvert_ptr) 357 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 358 SIZEOF(my_color_converter)); 359 cinfo->cconvert = (struct jpeg_color_converter *) cconvert; 360 /* set start_pass to null method until we find out differently */ 361 cconvert->pub.start_pass = null_method; 362 363 /* Make sure input_components agrees with in_color_space */ 364 switch (cinfo->in_color_space) { 365 case JCS_GRAYSCALE: 366 if (cinfo->input_components != 1) 367 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 368 break; 369 370 case JCS_RGB: 371 #if RGB_PIXELSIZE != 3 372 if (cinfo->input_components != RGB_PIXELSIZE) 373 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 374 break; 375 #endif /* else share code with YCbCr */ 376 377 case JCS_YCbCr: 378 if (cinfo->input_components != 3) 379 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 380 break; 381 382 case JCS_CMYK: 383 case JCS_YCCK: 384 if (cinfo->input_components != 4) 385 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 386 break; 387 388 default: /* JCS_UNKNOWN can be anything */ 389 if (cinfo->input_components < 1) 390 ERREXIT(cinfo, JERR_BAD_IN_COLORSPACE); 391 break; 392 } 393 394 /* Check num_components, set conversion method based on requested space */ 395 switch (cinfo->jpeg_color_space) { 396 case JCS_GRAYSCALE: 397 if (cinfo->num_components != 1) 398 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 399 if (cinfo->in_color_space == JCS_GRAYSCALE) 400 cconvert->pub.color_convert = grayscale_convert; 401 else if (cinfo->in_color_space == JCS_RGB) { 402 cconvert->pub.start_pass = rgb_ycc_start; 403 cconvert->pub.color_convert = rgb_gray_convert; 404 } else if (cinfo->in_color_space == JCS_YCbCr) 405 cconvert->pub.color_convert = grayscale_convert; 406 else 407 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 408 break; 409 410 case JCS_RGB: 411 if (cinfo->num_components != 3) 412 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 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 break; 418 419 case JCS_YCbCr: 420 if (cinfo->num_components != 3) 421 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 422 if (cinfo->in_color_space == JCS_RGB) { 423 cconvert->pub.start_pass = rgb_ycc_start; 424 cconvert->pub.color_convert = rgb_ycc_convert; 425 } else if (cinfo->in_color_space == JCS_YCbCr) 426 cconvert->pub.color_convert = null_convert; 427 else 428 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 429 break; 430 431 case JCS_CMYK: 432 if (cinfo->num_components != 4) 433 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 434 if (cinfo->in_color_space == JCS_CMYK) 435 cconvert->pub.color_convert = null_convert; 436 else 437 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 438 break; 439 440 case JCS_YCCK: 441 if (cinfo->num_components != 4) 442 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 443 if (cinfo->in_color_space == JCS_CMYK) { 444 cconvert->pub.start_pass = rgb_ycc_start; 445 cconvert->pub.color_convert = cmyk_ycck_convert; 446 } else if (cinfo->in_color_space == JCS_YCCK) 447 cconvert->pub.color_convert = null_convert; 448 else 449 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 450 break; 451 452 default: /* allow null conversion of JCS_UNKNOWN */ 453 if (cinfo->jpeg_color_space != cinfo->in_color_space || 454 cinfo->num_components != cinfo->input_components) 455 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 456 cconvert->pub.color_convert = null_convert; 457 break; 458 } 459 } 460
