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