jdmerge.cpp (15532B)
1 /* 2 * jdmerge.c 3 * 4 * Copyright (C) 1994-1995, 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 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 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 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 127 128 /* Mark the spare buffer empty */ 129 upsample->spare_full = FALSE; 130 /* Initialize total-height counter for detecting bottom of image */ 131 upsample->rows_to_go = cinfo->output_height; 132 } 133 134 135 /* 136 * Control routine to do upsampling (and color conversion). 137 * 138 * The control routine just handles the row buffering considerations. 139 */ 140 141 METHODDEF void 142 merged_2v_upsample( j_decompress_ptr cinfo, 143 JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr, 144 JDIMENSION in_row_groups_avail, 145 JSAMPARRAY output_buf, JDIMENSION * out_row_ctr, 146 JDIMENSION out_rows_avail ) { 147 /* 2:1 vertical sampling case: may need a spare row. */ 148 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 149 JSAMPROW work_ptrs[2]; 150 JDIMENSION num_rows; /* number of rows returned to caller */ 151 152 if ( upsample->spare_full ) { 153 /* If we have a spare row saved from a previous cycle, just return it. */ 154 jcopy_sample_rows( &upsample->spare_row, 0, output_buf + *out_row_ctr, 0, 155 1, upsample->out_row_width ); 156 num_rows = 1; 157 upsample->spare_full = FALSE; 158 } else { 159 /* Figure number of rows to return to caller. */ 160 num_rows = 2; 161 /* Not more than the distance to the end of the image. */ 162 if ( num_rows > upsample->rows_to_go ) { 163 num_rows = upsample->rows_to_go; 164 } 165 /* And not more than what the client can accept: */ 166 out_rows_avail -= *out_row_ctr; 167 if ( num_rows > out_rows_avail ) { 168 num_rows = out_rows_avail; 169 } 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 } 190 191 192 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 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 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 229 register int y, cred, cgreen, cblue; 230 int cb, cr; 231 register JSAMPROW outptr; 232 JSAMPROW inptr0, inptr1, inptr2; 233 JDIMENSION col; 234 /* copy these pointers into registers if possible */ 235 register JSAMPLE * range_limit = cinfo->sample_range_limit; 236 int * Crrtab = upsample->Cr_r_tab; 237 int * Cbbtab = upsample->Cb_b_tab; 238 INT32 * Crgtab = upsample->Cr_g_tab; 239 INT32 * Cbgtab = upsample->Cb_g_tab; 240 SHIFT_TEMPS 241 242 inptr0 = input_buf[0][in_row_group_ctr]; 243 inptr1 = input_buf[1][in_row_group_ctr]; 244 inptr2 = input_buf[2][in_row_group_ctr]; 245 outptr = output_buf[0]; 246 /* Loop for each pair of output pixels */ 247 for ( col = cinfo->output_width >> 1; col > 0; col-- ) { 248 /* Do the chroma part of the calculation */ 249 cb = GETJSAMPLE( *inptr1++ ); 250 cr = GETJSAMPLE( *inptr2++ ); 251 cred = Crrtab[cr]; 252 cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS ); 253 cblue = Cbbtab[cb]; 254 /* Fetch 2 Y values and emit 2 pixels */ 255 y = GETJSAMPLE( *inptr0++ ); 256 outptr[RGB_RED] = range_limit[y + cred]; 257 outptr[RGB_GREEN] = range_limit[y + cgreen]; 258 outptr[RGB_BLUE] = range_limit[y + cblue]; 259 outptr += RGB_PIXELSIZE; 260 y = GETJSAMPLE( *inptr0++ ); 261 outptr[RGB_RED] = range_limit[y + cred]; 262 outptr[RGB_GREEN] = range_limit[y + cgreen]; 263 outptr[RGB_BLUE] = range_limit[y + cblue]; 264 outptr += RGB_PIXELSIZE; 265 } 266 /* If image width is odd, do the last output column separately */ 267 if ( cinfo->output_width & 1 ) { 268 cb = GETJSAMPLE( *inptr1 ); 269 cr = GETJSAMPLE( *inptr2 ); 270 cred = Crrtab[cr]; 271 cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS ); 272 cblue = Cbbtab[cb]; 273 y = GETJSAMPLE( *inptr0 ); 274 outptr[RGB_RED] = range_limit[y + cred]; 275 outptr[RGB_GREEN] = range_limit[y + cgreen]; 276 outptr[RGB_BLUE] = range_limit[y + cblue]; 277 } 278 } 279 280 281 /* 282 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical. 283 */ 284 285 METHODDEF void 286 h2v2_merged_upsample( j_decompress_ptr cinfo, 287 JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr, 288 JSAMPARRAY output_buf ) { 289 my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample; 290 register int y, cred, cgreen, cblue; 291 int cb, cr; 292 register JSAMPROW outptr0, outptr1; 293 JSAMPROW inptr00, inptr01, inptr1, inptr2; 294 JDIMENSION col; 295 /* copy these pointers into registers if possible */ 296 register JSAMPLE * range_limit = cinfo->sample_range_limit; 297 int * Crrtab = upsample->Cr_r_tab; 298 int * Cbbtab = upsample->Cb_b_tab; 299 INT32 * Crgtab = upsample->Cr_g_tab; 300 INT32 * Cbgtab = upsample->Cb_g_tab; 301 SHIFT_TEMPS 302 303 inptr00 = input_buf[0][in_row_group_ctr * 2]; 304 inptr01 = input_buf[0][in_row_group_ctr * 2 + 1]; 305 inptr1 = input_buf[1][in_row_group_ctr]; 306 inptr2 = input_buf[2][in_row_group_ctr]; 307 outptr0 = output_buf[0]; 308 outptr1 = output_buf[1]; 309 /* Loop for each group of output pixels */ 310 for ( col = cinfo->output_width >> 1; col > 0; col-- ) { 311 /* Do the chroma part of the calculation */ 312 cb = GETJSAMPLE( *inptr1++ ); 313 cr = GETJSAMPLE( *inptr2++ ); 314 cred = Crrtab[cr]; 315 cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS ); 316 cblue = Cbbtab[cb]; 317 /* Fetch 4 Y values and emit 4 pixels */ 318 y = GETJSAMPLE( *inptr00++ ); 319 outptr0[RGB_RED] = range_limit[y + cred]; 320 outptr0[RGB_GREEN] = range_limit[y + cgreen]; 321 outptr0[RGB_BLUE] = range_limit[y + cblue]; 322 outptr0 += RGB_PIXELSIZE; 323 y = GETJSAMPLE( *inptr00++ ); 324 outptr0[RGB_RED] = range_limit[y + cred]; 325 outptr0[RGB_GREEN] = range_limit[y + cgreen]; 326 outptr0[RGB_BLUE] = range_limit[y + cblue]; 327 outptr0 += RGB_PIXELSIZE; 328 y = GETJSAMPLE( *inptr01++ ); 329 outptr1[RGB_RED] = range_limit[y + cred]; 330 outptr1[RGB_GREEN] = range_limit[y + cgreen]; 331 outptr1[RGB_BLUE] = range_limit[y + cblue]; 332 outptr1 += RGB_PIXELSIZE; 333 y = GETJSAMPLE( *inptr01++ ); 334 outptr1[RGB_RED] = range_limit[y + cred]; 335 outptr1[RGB_GREEN] = range_limit[y + cgreen]; 336 outptr1[RGB_BLUE] = range_limit[y + cblue]; 337 outptr1 += RGB_PIXELSIZE; 338 } 339 /* If image width is odd, do the last output column separately */ 340 if ( cinfo->output_width & 1 ) { 341 cb = GETJSAMPLE( *inptr1 ); 342 cr = GETJSAMPLE( *inptr2 ); 343 cred = Crrtab[cr]; 344 cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS ); 345 cblue = Cbbtab[cb]; 346 y = GETJSAMPLE( *inptr00 ); 347 outptr0[RGB_RED] = range_limit[y + cred]; 348 outptr0[RGB_GREEN] = range_limit[y + cgreen]; 349 outptr0[RGB_BLUE] = range_limit[y + cblue]; 350 y = GETJSAMPLE( *inptr01 ); 351 outptr1[RGB_RED] = range_limit[y + cred]; 352 outptr1[RGB_GREEN] = range_limit[y + cgreen]; 353 outptr1[RGB_BLUE] = range_limit[y + cblue]; 354 } 355 } 356 357 358 /* 359 * Module initialization routine for merged upsampling/color conversion. 360 * 361 * NB: this is called under the conditions determined by use_merged_upsample() 362 * in jdmaster.c. That routine MUST correspond to the actual capabilities 363 * of this module; no safety checks are made here. 364 */ 365 366 GLOBAL void 367 jinit_merged_upsampler( j_decompress_ptr cinfo ) { 368 my_upsample_ptr upsample; 369 370 upsample = (my_upsample_ptr) 371 ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE, 372 SIZEOF( my_upsampler ) ); 373 cinfo->upsample = (struct jpeg_upsampler *) upsample; 374 upsample->pub.start_pass = start_pass_merged_upsample; 375 upsample->pub.need_context_rows = FALSE; 376 377 upsample->out_row_width = cinfo->output_width * cinfo->out_color_components; 378 379 if ( cinfo->max_v_samp_factor == 2 ) { 380 upsample->pub.upsample = merged_2v_upsample; 381 upsample->upmethod = h2v2_merged_upsample; 382 /* Allocate a spare row buffer */ 383 upsample->spare_row = (JSAMPROW) 384 ( *cinfo->mem->alloc_large )( (j_common_ptr) cinfo, JPOOL_IMAGE, 385 (size_t) ( upsample->out_row_width * SIZEOF( JSAMPLE ) ) ); 386 } else { 387 upsample->pub.upsample = merged_1v_upsample; 388 upsample->upmethod = h2v1_merged_upsample; 389 /* No spare row needed */ 390 upsample->spare_row = NULL; 391 } 392 393 build_ycc_rgb_table( cinfo ); 394 } 395 396 #endif /* UPSAMPLE_MERGING_SUPPORTED */