jdcolor.c (12091B)
1 /* 2 * jdcolor.c 3 * 4 * Copyright (C) 1991-1995, 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 * Adobe-style YCCK->CMYK conversion. 212 * We convert YCbCr to R=1-C, G=1-M, and B=1-Y using the same 213 * conversion as above, while passing K (black) unchanged. 214 * We assume build_ycc_rgb_table has been called. 215 */ 216 217 METHODDEF void 218 ycck_cmyk_convert (j_decompress_ptr cinfo, 219 JSAMPIMAGE input_buf, JDIMENSION input_row, 220 JSAMPARRAY output_buf, int num_rows) 221 { 222 my_cconvert_ptr cconvert = (my_cconvert_ptr) cinfo->cconvert; 223 register int y, cb, cr; 224 register JSAMPROW outptr; 225 register JSAMPROW inptr0, inptr1, inptr2, inptr3; 226 register JDIMENSION col; 227 JDIMENSION num_cols = cinfo->output_width; 228 /* copy these pointers into registers if possible */ 229 register JSAMPLE * range_limit = cinfo->sample_range_limit; 230 register int * Crrtab = cconvert->Cr_r_tab; 231 register int * Cbbtab = cconvert->Cb_b_tab; 232 register INT32 * Crgtab = cconvert->Cr_g_tab; 233 register INT32 * Cbgtab = cconvert->Cb_g_tab; 234 SHIFT_TEMPS 235 236 while (--num_rows >= 0) { 237 inptr0 = input_buf[0][input_row]; 238 inptr1 = input_buf[1][input_row]; 239 inptr2 = input_buf[2][input_row]; 240 inptr3 = input_buf[3][input_row]; 241 input_row++; 242 outptr = *output_buf++; 243 for (col = 0; col < num_cols; col++) { 244 y = GETJSAMPLE(inptr0[col]); 245 cb = GETJSAMPLE(inptr1[col]); 246 cr = GETJSAMPLE(inptr2[col]); 247 /* Range-limiting is essential due to noise introduced by DCT losses. */ 248 outptr[0] = range_limit[MAXJSAMPLE - (y + Crrtab[cr])]; /* red */ 249 outptr[1] = range_limit[MAXJSAMPLE - (y + /* green */ 250 ((int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], 251 SCALEBITS)))]; 252 outptr[2] = range_limit[MAXJSAMPLE - (y + Cbbtab[cb])]; /* blue */ 253 /* K passes through unchanged */ 254 outptr[3] = inptr3[col]; /* don't need GETJSAMPLE here */ 255 outptr += 4; 256 } 257 } 258 } 259 260 261 /* 262 * Empty method for start_pass. 263 */ 264 265 METHODDEF void 266 start_pass_dcolor (j_decompress_ptr cinfo) 267 { 268 /* no work needed */ 269 } 270 271 272 /* 273 * Module initialization routine for output colorspace conversion. 274 */ 275 276 GLOBAL void 277 jinit_color_deconverter (j_decompress_ptr cinfo) 278 { 279 my_cconvert_ptr cconvert; 280 int ci; 281 282 cconvert = (my_cconvert_ptr) 283 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 284 SIZEOF(my_color_deconverter)); 285 cinfo->cconvert = (struct jpeg_color_deconverter *) cconvert; 286 cconvert->pub.start_pass = start_pass_dcolor; 287 288 /* Make sure num_components agrees with jpeg_color_space */ 289 switch (cinfo->jpeg_color_space) { 290 case JCS_GRAYSCALE: 291 if (cinfo->num_components != 1) 292 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 293 break; 294 295 case JCS_RGB: 296 case JCS_YCbCr: 297 if (cinfo->num_components != 3) 298 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 299 break; 300 301 case JCS_CMYK: 302 case JCS_YCCK: 303 if (cinfo->num_components != 4) 304 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 305 break; 306 307 default: /* JCS_UNKNOWN can be anything */ 308 if (cinfo->num_components < 1) 309 ERREXIT(cinfo, JERR_BAD_J_COLORSPACE); 310 break; 311 } 312 313 /* Set out_color_components and conversion method based on requested space. 314 * Also clear the component_needed flags for any unused components, 315 * so that earlier pipeline stages can avoid useless computation. 316 */ 317 318 switch (cinfo->out_color_space) { 319 case JCS_GRAYSCALE: 320 cinfo->out_color_components = 1; 321 if (cinfo->jpeg_color_space == JCS_GRAYSCALE || 322 cinfo->jpeg_color_space == JCS_YCbCr) { 323 cconvert->pub.color_convert = grayscale_convert; 324 /* For color->grayscale conversion, only the Y (0) component is needed */ 325 for (ci = 1; ci < cinfo->num_components; ci++) 326 cinfo->comp_info[ci].component_needed = FALSE; 327 } else 328 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 329 break; 330 331 case JCS_RGB: 332 cinfo->out_color_components = RGB_PIXELSIZE; 333 if (cinfo->jpeg_color_space == JCS_YCbCr) { 334 cconvert->pub.color_convert = ycc_rgb_convert; 335 build_ycc_rgb_table(cinfo); 336 } else if (cinfo->jpeg_color_space == JCS_RGB && RGB_PIXELSIZE == 3) { 337 cconvert->pub.color_convert = null_convert; 338 } else 339 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 340 break; 341 342 case JCS_CMYK: 343 cinfo->out_color_components = 4; 344 if (cinfo->jpeg_color_space == JCS_YCCK) { 345 cconvert->pub.color_convert = ycck_cmyk_convert; 346 build_ycc_rgb_table(cinfo); 347 } else if (cinfo->jpeg_color_space == JCS_CMYK) { 348 cconvert->pub.color_convert = null_convert; 349 } else 350 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 351 break; 352 353 default: 354 /* Permit null conversion to same output space */ 355 if (cinfo->out_color_space == cinfo->jpeg_color_space) { 356 cinfo->out_color_components = cinfo->num_components; 357 cconvert->pub.color_convert = null_convert; 358 } else /* unsupported non-null conversion */ 359 ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL); 360 break; 361 } 362 363 if (cinfo->quantize_colors) 364 cinfo->output_components = 1; /* single colormapped output component */ 365 else 366 cinfo->output_components = cinfo->out_color_components; 367 }