jdmerge.c (13916B)
1 /* 2 * jdmerge.c 3 * 4 * Copyright (C) 1994-1996, 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 code for merged upsampling/color conversion. 9 * 10 * This file combines functions from jdsample.c and jdcolor.c; 11 * read those files first to understand what's going on. 12 * 13 * When the chroma components are to be upsampled by simple replication 14 * (ie, box filtering), we can save some work in color conversion by 15 * calculating all the output pixels corresponding to a pair of chroma 16 * samples at one time. In the conversion equations 17 * R = Y + K1 * Cr 18 * G = Y + K2 * Cb + K3 * Cr 19 * B = Y + K4 * Cb 20 * only the Y term varies among the group of pixels corresponding to a pair 21 * of chroma samples, so the rest of the terms can be calculated just once. 22 * At typical sampling ratios, this eliminates half or three-quarters of the 23 * multiplications needed for color conversion. 24 * 25 * This file currently provides implementations for the following cases: 26 * YCbCr => RGB color conversion only. 27 * Sampling ratios of 2h1v or 2h2v. 28 * No scaling needed at upsample time. 29 * Corner-aligned (non-CCIR601) sampling alignment. 30 * Other special cases could be added, but in most applications these are 31 * the only common cases. (For uncommon cases we fall back on the more 32 * general code in jdsample.c and jdcolor.c.) 33 */ 34 35 #define JPEG_INTERNALS 36 #include "jinclude.h" 37 #include "jpeglib.h" 38 39 #ifdef UPSAMPLE_MERGING_SUPPORTED 40 41 42 /* Private subobject */ 43 44 typedef struct { 45 struct jpeg_upsampler pub; /* public fields */ 46 47 /* Pointer to routine to do actual upsampling/conversion of one row group */ 48 JMETHOD(void, upmethod, (j_decompress_ptr cinfo, 49 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 50 JSAMPARRAY output_buf)); 51 52 /* Private state for YCC->RGB conversion */ 53 int * Cr_r_tab; /* => table for Cr to R conversion */ 54 int * Cb_b_tab; /* => table for Cb to B conversion */ 55 INT32 * Cr_g_tab; /* => table for Cr to G conversion */ 56 INT32 * Cb_g_tab; /* => table for Cb to G conversion */ 57 58 /* For 2:1 vertical sampling, we produce two output rows at a time. 59 * We need a "spare" row buffer to hold the second output row if the 60 * application provides just a one-row buffer; we also use the spare 61 * to discard the dummy last row if the image height is odd. 62 */ 63 JSAMPROW spare_row; 64 boolean spare_full; /* T if spare buffer is occupied */ 65 66 JDIMENSION out_row_width; /* samples per output row */ 67 JDIMENSION rows_to_go; /* counts rows remaining in image */ 68 } my_upsampler; 69 70 typedef my_upsampler * my_upsample_ptr; 71 72 #define SCALEBITS 16 /* speediest right-shift on some machines */ 73 #define ONE_HALF ((INT32) 1 << (SCALEBITS-1)) 74 #define FIX(x) ((INT32) ((x) * (1L<<SCALEBITS) + 0.5)) 75 76 77 /* 78 * Initialize tables for YCC->RGB colorspace conversion. 79 * This is taken directly from jdcolor.c; see that file for more info. 80 */ 81 82 LOCAL(void) 83 build_ycc_rgb_table (j_decompress_ptr cinfo) 84 { 85 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 86 int i; 87 INT32 x; 88 SHIFT_TEMPS 89 90 upsample->Cr_r_tab = (int *) 91 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 92 (MAXJSAMPLE+1) * SIZEOF(int)); 93 upsample->Cb_b_tab = (int *) 94 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 95 (MAXJSAMPLE+1) * SIZEOF(int)); 96 upsample->Cr_g_tab = (INT32 *) 97 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 98 (MAXJSAMPLE+1) * SIZEOF(INT32)); 99 upsample->Cb_g_tab = (INT32 *) 100 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 101 (MAXJSAMPLE+1) * SIZEOF(INT32)); 102 103 for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) { 104 /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */ 105 /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */ 106 /* Cr=>R value is nearest int to 1.40200 * x */ 107 upsample->Cr_r_tab[i] = (int) 108 RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS); 109 /* Cb=>B value is nearest int to 1.77200 * x */ 110 upsample->Cb_b_tab[i] = (int) 111 RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS); 112 /* Cr=>G value is scaled-up -0.71414 * x */ 113 upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x; 114 /* Cb=>G value is scaled-up -0.34414 * x */ 115 /* We also add in ONE_HALF so that need not do it in inner loop */ 116 upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF; 117 } 118 } 119 120 121 /* 122 * Initialize for an upsampling pass. 123 */ 124 125 METHODDEF(void) 126 start_pass_merged_upsample (j_decompress_ptr cinfo) 127 { 128 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 129 130 /* Mark the spare buffer empty */ 131 upsample->spare_full = FALSE; 132 /* Initialize total-height counter for detecting bottom of image */ 133 upsample->rows_to_go = cinfo->output_height; 134 } 135 136 137 /* 138 * Control routine to do upsampling (and color conversion). 139 * 140 * The control routine just handles the row buffering considerations. 141 */ 142 143 METHODDEF(void) 144 merged_2v_upsample (j_decompress_ptr cinfo, 145 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 146 JDIMENSION in_row_groups_avail, 147 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 148 JDIMENSION out_rows_avail) 149 /* 2:1 vertical sampling case: may need a spare row. */ 150 { 151 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 152 JSAMPROW work_ptrs[2]; 153 JDIMENSION num_rows; /* number of rows returned to caller */ 154 155 if (upsample->spare_full) { 156 /* If we have a spare row saved from a previous cycle, just return it. */ 157 jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0, 158 1, upsample->out_row_width); 159 num_rows = 1; 160 upsample->spare_full = FALSE; 161 } else { 162 /* Figure number of rows to return to caller. */ 163 num_rows = 2; 164 /* Not more than the distance to the end of the image. */ 165 if (num_rows > upsample->rows_to_go) 166 num_rows = upsample->rows_to_go; 167 /* And not more than what the client can accept: */ 168 out_rows_avail -= *out_row_ctr; 169 if (num_rows > out_rows_avail) 170 num_rows = out_rows_avail; 171 /* Create output pointer array for upsampler. */ 172 work_ptrs[0] = output_buf[*out_row_ctr]; 173 if (num_rows > 1) { 174 work_ptrs[1] = output_buf[*out_row_ctr + 1]; 175 } else { 176 work_ptrs[1] = upsample->spare_row; 177 upsample->spare_full = TRUE; 178 } 179 /* Now do the upsampling. */ 180 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs); 181 } 182 183 /* Adjust counts */ 184 *out_row_ctr += num_rows; 185 upsample->rows_to_go -= num_rows; 186 /* When the buffer is emptied, declare this input row group consumed */ 187 if (! upsample->spare_full) 188 (*in_row_group_ctr)++; 189 } 190 191 192 METHODDEF(void) 193 merged_1v_upsample (j_decompress_ptr cinfo, 194 JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr, 195 JDIMENSION in_row_groups_avail, 196 JSAMPARRAY output_buf, JDIMENSION *out_row_ctr, 197 JDIMENSION out_rows_avail) 198 /* 1:1 vertical sampling case: much easier, never need a spare row. */ 199 { 200 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 201 202 /* Just do the upsampling. */ 203 (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, 204 output_buf + *out_row_ctr); 205 /* Adjust counts */ 206 (*out_row_ctr)++; 207 (*in_row_group_ctr)++; 208 } 209 210 211 /* 212 * These are the routines invoked by the control routines to do 213 * the actual upsampling/conversion. One row group is processed per call. 214 * 215 * Note: since we may be writing directly into application-supplied buffers, 216 * we have to be honest about the output width; we can't assume the buffer 217 * has been rounded up to an even width. 218 */ 219 220 221 /* 222 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical. 223 */ 224 225 METHODDEF(void) 226 h2v1_merged_upsample (j_decompress_ptr cinfo, 227 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 228 JSAMPARRAY output_buf) 229 { 230 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 231 register int y, cred, cgreen, cblue; 232 int cb, cr; 233 register JSAMPROW outptr; 234 JSAMPROW inptr0, inptr1, inptr2; 235 JDIMENSION col; 236 /* copy these pointers into registers if possible */ 237 register JSAMPLE * range_limit = cinfo->sample_range_limit; 238 int * Crrtab = upsample->Cr_r_tab; 239 int * Cbbtab = upsample->Cb_b_tab; 240 INT32 * Crgtab = upsample->Cr_g_tab; 241 INT32 * Cbgtab = upsample->Cb_g_tab; 242 SHIFT_TEMPS 243 244 inptr0 = input_buf[0][in_row_group_ctr]; 245 inptr1 = input_buf[1][in_row_group_ctr]; 246 inptr2 = input_buf[2][in_row_group_ctr]; 247 outptr = output_buf[0]; 248 /* Loop for each pair of output pixels */ 249 for (col = cinfo->output_width >> 1; col > 0; col--) { 250 /* Do the chroma part of the calculation */ 251 cb = GETJSAMPLE(*inptr1++); 252 cr = GETJSAMPLE(*inptr2++); 253 cred = Crrtab[cr]; 254 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 255 cblue = Cbbtab[cb]; 256 /* Fetch 2 Y values and emit 2 pixels */ 257 y = GETJSAMPLE(*inptr0++); 258 outptr[RGB_RED] = range_limit[y + cred]; 259 outptr[RGB_GREEN] = range_limit[y + cgreen]; 260 outptr[RGB_BLUE] = range_limit[y + cblue]; 261 outptr += RGB_PIXELSIZE; 262 y = GETJSAMPLE(*inptr0++); 263 outptr[RGB_RED] = range_limit[y + cred]; 264 outptr[RGB_GREEN] = range_limit[y + cgreen]; 265 outptr[RGB_BLUE] = range_limit[y + cblue]; 266 outptr += RGB_PIXELSIZE; 267 } 268 /* If image width is odd, do the last output column separately */ 269 if (cinfo->output_width & 1) { 270 cb = GETJSAMPLE(*inptr1); 271 cr = GETJSAMPLE(*inptr2); 272 cred = Crrtab[cr]; 273 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 274 cblue = Cbbtab[cb]; 275 y = GETJSAMPLE(*inptr0); 276 outptr[RGB_RED] = range_limit[y + cred]; 277 outptr[RGB_GREEN] = range_limit[y + cgreen]; 278 outptr[RGB_BLUE] = range_limit[y + cblue]; 279 } 280 } 281 282 283 /* 284 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical. 285 */ 286 287 METHODDEF(void) 288 h2v2_merged_upsample (j_decompress_ptr cinfo, 289 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 290 JSAMPARRAY output_buf) 291 { 292 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 293 register int y, cred, cgreen, cblue; 294 int cb, cr; 295 register JSAMPROW outptr0, outptr1; 296 JSAMPROW inptr00, inptr01, inptr1, inptr2; 297 JDIMENSION col; 298 /* copy these pointers into registers if possible */ 299 register JSAMPLE * range_limit = cinfo->sample_range_limit; 300 int * Crrtab = upsample->Cr_r_tab; 301 int * Cbbtab = upsample->Cb_b_tab; 302 INT32 * Crgtab = upsample->Cr_g_tab; 303 INT32 * Cbgtab = upsample->Cb_g_tab; 304 SHIFT_TEMPS 305 306 inptr00 = input_buf[0][in_row_group_ctr*2]; 307 inptr01 = input_buf[0][in_row_group_ctr*2 + 1]; 308 inptr1 = input_buf[1][in_row_group_ctr]; 309 inptr2 = input_buf[2][in_row_group_ctr]; 310 outptr0 = output_buf[0]; 311 outptr1 = output_buf[1]; 312 /* Loop for each group of output pixels */ 313 for (col = cinfo->output_width >> 1; col > 0; col--) { 314 /* Do the chroma part of the calculation */ 315 cb = GETJSAMPLE(*inptr1++); 316 cr = GETJSAMPLE(*inptr2++); 317 cred = Crrtab[cr]; 318 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 319 cblue = Cbbtab[cb]; 320 /* Fetch 4 Y values and emit 4 pixels */ 321 y = GETJSAMPLE(*inptr00++); 322 outptr0[RGB_RED] = range_limit[y + cred]; 323 outptr0[RGB_GREEN] = range_limit[y + cgreen]; 324 outptr0[RGB_BLUE] = range_limit[y + cblue]; 325 outptr0 += RGB_PIXELSIZE; 326 y = GETJSAMPLE(*inptr00++); 327 outptr0[RGB_RED] = range_limit[y + cred]; 328 outptr0[RGB_GREEN] = range_limit[y + cgreen]; 329 outptr0[RGB_BLUE] = range_limit[y + cblue]; 330 outptr0 += RGB_PIXELSIZE; 331 y = GETJSAMPLE(*inptr01++); 332 outptr1[RGB_RED] = range_limit[y + cred]; 333 outptr1[RGB_GREEN] = range_limit[y + cgreen]; 334 outptr1[RGB_BLUE] = range_limit[y + cblue]; 335 outptr1 += RGB_PIXELSIZE; 336 y = GETJSAMPLE(*inptr01++); 337 outptr1[RGB_RED] = range_limit[y + cred]; 338 outptr1[RGB_GREEN] = range_limit[y + cgreen]; 339 outptr1[RGB_BLUE] = range_limit[y + cblue]; 340 outptr1 += RGB_PIXELSIZE; 341 } 342 /* If image width is odd, do the last output column separately */ 343 if (cinfo->output_width & 1) { 344 cb = GETJSAMPLE(*inptr1); 345 cr = GETJSAMPLE(*inptr2); 346 cred = Crrtab[cr]; 347 cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS); 348 cblue = Cbbtab[cb]; 349 y = GETJSAMPLE(*inptr00); 350 outptr0[RGB_RED] = range_limit[y + cred]; 351 outptr0[RGB_GREEN] = range_limit[y + cgreen]; 352 outptr0[RGB_BLUE] = range_limit[y + cblue]; 353 y = GETJSAMPLE(*inptr01); 354 outptr1[RGB_RED] = range_limit[y + cred]; 355 outptr1[RGB_GREEN] = range_limit[y + cgreen]; 356 outptr1[RGB_BLUE] = range_limit[y + cblue]; 357 } 358 } 359 360 361 /* 362 * Module initialization routine for merged upsampling/color conversion. 363 * 364 * NB: this is called under the conditions determined by use_merged_upsample() 365 * in jdmaster.c. That routine MUST correspond to the actual capabilities 366 * of this module; no safety checks are made here. 367 */ 368 369 GLOBAL(void) 370 jinit_merged_upsampler (j_decompress_ptr cinfo) 371 { 372 my_upsample_ptr upsample; 373 374 upsample = (my_upsample_ptr) 375 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 376 SIZEOF(my_upsampler)); 377 cinfo->upsample = (struct jpeg_upsampler *) upsample; 378 upsample->pub.start_pass = start_pass_merged_upsample; 379 upsample->pub.need_context_rows = FALSE; 380 381 upsample->out_row_width = cinfo->output_width * cinfo->out_color_components; 382 383 if (cinfo->max_v_samp_factor == 2) { 384 upsample->pub.upsample = merged_2v_upsample; 385 upsample->upmethod = h2v2_merged_upsample; 386 /* Allocate a spare row buffer */ 387 upsample->spare_row = (JSAMPROW) 388 (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE, 389 (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE))); 390 } else { 391 upsample->pub.upsample = merged_1v_upsample; 392 upsample->upmethod = h2v1_merged_upsample; 393 /* No spare row needed */ 394 upsample->spare_row = NULL; 395 } 396 397 build_ycc_rgb_table(cinfo); 398 } 399 400 #endif /* UPSAMPLE_MERGING_SUPPORTED */