| 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 |
} |
Parent Directory
| 
Revision Log