libs/jpeg/jdmerge.c

   1 /*
   2  * jdmerge.c
   3  *
   4  * Copyright (C) 1994-1996, Thomas G. Lane.
   5  * Modified 2013-2020 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains code for merged upsampling/color conversion.
  10  *
  11  * This file combines functions from jdsample.c and jdcolor.c;
  12  * read those files first to understand what's going on.
  13  *
  14  * When the chroma components are to be upsampled by simple replication
  15  * (ie, box filtering), we can save some work in color conversion by
  16  * calculating all the output pixels corresponding to a pair of chroma
  17  * samples at one time.  In the conversion equations
  18  *      R = Y           + K1 * Cr
  19  *      G = Y + K2 * Cb + K3 * Cr
  20  *      B = Y + K4 * Cb
  21  * only the Y term varies among the group of pixels corresponding to a pair
  22  * of chroma samples, so the rest of the terms can be calculated just once.
  23  * At typical sampling ratios, this eliminates half or three-quarters of the
  24  * multiplications needed for color conversion.
  25  *
  26  * This file currently provides implementations for the following cases:
  27  *      YCC => RGB color conversion only (YCbCr or BG_YCC).
  28  *      Sampling ratios of 2h1v or 2h2v.
  29  *      No scaling needed at upsample time.
  30  *      Corner-aligned (non-CCIR601) sampling alignment.
  31  * Other special cases could be added, but in most applications these are
  32  * the only common cases.  (For uncommon cases we fall back on the more
  33  * general code in jdsample.c and jdcolor.c.)
  34  */
  35
  36 #define JPEG_INTERNALS
  37 #include "jinclude.h"
  38 #include "jpeglib.h"
  39
  40 #ifdef UPSAMPLE_MERGING_SUPPORTED
  41
  42
  43 #if RANGE_BITS < 2
  44   /* Deliberate syntax err */
  45   Sorry, this code requires 2 or more range extension bits.
  46 #endif
  47
  48
  49 /* Private subobject */
  50
  51 typedef struct {
  52   struct jpeg_upsampler pub;    /* public fields */
  53
  54   /* Pointer to routine to do actual upsampling/conversion of one row group */
  55   JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
  56                            JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
  57                            JSAMPARRAY output_buf));
  58
  59   /* Private state for YCC->RGB conversion */
  60   int * Cr_r_tab;               /* => table for Cr to R conversion */
  61   int * Cb_b_tab;               /* => table for Cb to B conversion */
  62   INT32 * Cr_g_tab;             /* => table for Cr to G conversion */
  63   INT32 * Cb_g_tab;             /* => table for Cb to G conversion */
  64
  65   /* For 2:1 vertical sampling, we produce two output rows at a time.
  66    * We need a "spare" row buffer to hold the second output row if the
  67    * application provides just a one-row buffer; we also use the spare
  68    * to discard the dummy last row if the image height is odd.
  69    */
  70   JSAMPROW spare_row;
  71   boolean spare_full;           /* T if spare buffer is occupied */
  72
  73   JDIMENSION out_row_width;     /* samples per output row */
  74   JDIMENSION rows_to_go;        /* counts rows remaining in image */
  75 } my_upsampler;
  76
  77 typedef my_upsampler * my_upsample_ptr;
  78
  79 #define SCALEBITS       16      /* speediest right-shift on some machines */
  80 #define ONE_HALF        ((INT32) 1 << (SCALEBITS-1))
  81 #define FIX(x)          ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
  82
  83
  84 /*
  85  * Initialize tables for YCbCr->RGB and BG_YCC->RGB colorspace conversion.
  86  * This is taken directly from jdcolor.c; see that file for more info.
  87  */
  88
  89 LOCAL(void)
  90 build_ycc_rgb_table (j_decompress_ptr cinfo)
  91 /* Normal case, sYCC */
  92 {
  93   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
  94   int i;
  95   INT32 x;
  96   SHIFT_TEMPS
  97
  98   upsample->Cr_r_tab = (int *) (*cinfo->mem->alloc_small)
  99     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(int));
 100   upsample->Cb_b_tab = (int *) (*cinfo->mem->alloc_small)
 101     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(int));
 102   upsample->Cr_g_tab = (INT32 *) (*cinfo->mem->alloc_small)
 103     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(INT32));
 104   upsample->Cb_g_tab = (INT32 *) (*cinfo->mem->alloc_small)
 105     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(INT32));
 106
 107   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
 108     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
 109     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
 110     /* Cr=>R value is nearest int to 1.402 * x */
 111     upsample->Cr_r_tab[i] = (int) DESCALE(FIX(1.402) * x, SCALEBITS);
 112     /* Cb=>B value is nearest int to 1.772 * x */
 113     upsample->Cb_b_tab[i] = (int) DESCALE(FIX(1.772) * x, SCALEBITS);
 114     /* Cr=>G value is scaled-up -0.714136286 * x */
 115     upsample->Cr_g_tab[i] = (- FIX(0.714136286)) * x;
 116     /* Cb=>G value is scaled-up -0.344136286 * x */
 117     /* We also add in ONE_HALF so that need not do it in inner loop */
 118     upsample->Cb_g_tab[i] = (- FIX(0.344136286)) * x + ONE_HALF;
 119   }
 120 }
 121
 122
 123 LOCAL(void)
 124 build_bg_ycc_rgb_table (j_decompress_ptr cinfo)
 125 /* Wide gamut case, bg-sYCC */
 126 {
 127   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 128   int i;
 129   INT32 x;
 130   SHIFT_TEMPS
 131
 132   upsample->Cr_r_tab = (int *) (*cinfo->mem->alloc_small)
 133     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(int));
 134   upsample->Cb_b_tab = (int *) (*cinfo->mem->alloc_small)
 135     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(int));
 136   upsample->Cr_g_tab = (INT32 *) (*cinfo->mem->alloc_small)
 137     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(INT32));
 138   upsample->Cb_g_tab = (INT32 *) (*cinfo->mem->alloc_small)
 139     ((j_common_ptr) cinfo, JPOOL_IMAGE, (MAXJSAMPLE+1) * SIZEOF(INT32));
 140
 141   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
 142     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
 143     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
 144     /* Cr=>R value is nearest int to 2.804 * x */
 145     upsample->Cr_r_tab[i] = (int) DESCALE(FIX(2.804) * x, SCALEBITS);
 146     /* Cb=>B value is nearest int to 3.544 * x */
 147     upsample->Cb_b_tab[i] = (int) DESCALE(FIX(3.544) * x, SCALEBITS);
 148     /* Cr=>G value is scaled-up -1.428272572 * x */
 149     upsample->Cr_g_tab[i] = (- FIX(1.428272572)) * x;
 150     /* Cb=>G value is scaled-up -0.688272572 * x */
 151     /* We also add in ONE_HALF so that need not do it in inner loop */
 152     upsample->Cb_g_tab[i] = (- FIX(0.688272572)) * x + ONE_HALF;
 153   }
 154 }
 155
 156
 157 /*
 158  * Initialize for an upsampling pass.
 159  */
 160
 161 METHODDEF(void)
 162 start_pass_merged_upsample (j_decompress_ptr cinfo)
 163 {
 164   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 165
 166   /* Mark the spare buffer empty */
 167   upsample->spare_full = FALSE;
 168   /* Initialize total-height counter for detecting bottom of image */
 169   upsample->rows_to_go = cinfo->output_height;
 170 }
 171
 172
 173 /*
 174  * Control routine to do upsampling (and color conversion).
 175  *
 176  * The control routine just handles the row buffering considerations.
 177  */
 178
 179 METHODDEF(void)
 180 merged_2v_upsample (j_decompress_ptr cinfo,
 181                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 182                     JDIMENSION in_row_groups_avail,
 183                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 184                     JDIMENSION out_rows_avail)
 185 /* 2:1 vertical sampling case: may need a spare row. */
 186 {
 187   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 188   JSAMPROW work_ptrs[2];
 189   JDIMENSION num_rows;          /* number of rows returned to caller */
 190
 191   if (upsample->spare_full) {
 192     /* If we have a spare row saved from a previous cycle, just return it. */
 193     jcopy_sample_rows(& upsample->spare_row, output_buf + *out_row_ctr,
 194                       1, upsample->out_row_width);
 195     num_rows = 1;
 196     upsample->spare_full = FALSE;
 197   } else {
 198     /* Figure number of rows to return to caller. */
 199     num_rows = 2;
 200     /* Not more than the distance to the end of the image. */
 201     if (num_rows > upsample->rows_to_go)
 202       num_rows = upsample->rows_to_go;
 203     /* And not more than what the client can accept: */
 204     out_rows_avail -= *out_row_ctr;
 205     if (num_rows > out_rows_avail)
 206       num_rows = out_rows_avail;
 207     /* Create output pointer array for upsampler. */
 208     work_ptrs[0] = output_buf[*out_row_ctr];
 209     if (num_rows > 1) {
 210       work_ptrs[1] = output_buf[*out_row_ctr + 1];
 211     } else {
 212       work_ptrs[1] = upsample->spare_row;
 213       upsample->spare_full = TRUE;
 214     }
 215     /* Now do the upsampling. */
 216     (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
 217   }
 218
 219   /* Adjust counts */
 220   *out_row_ctr += num_rows;
 221   upsample->rows_to_go -= num_rows;
 222   /* When the buffer is emptied, declare this input row group consumed */
 223   if (! upsample->spare_full)
 224     (*in_row_group_ctr)++;
 225 }
 226
 227
 228 METHODDEF(void)
 229 merged_1v_upsample (j_decompress_ptr cinfo,
 230                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 231                     JDIMENSION in_row_groups_avail,
 232                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 233                     JDIMENSION out_rows_avail)
 234 /* 1:1 vertical sampling case: much easier, never need a spare row. */
 235 {
 236   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 237
 238   /* Just do the upsampling. */
 239   (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
 240                          output_buf + *out_row_ctr);
 241   /* Adjust counts */
 242   (*out_row_ctr)++;
 243   (*in_row_group_ctr)++;
 244 }
 245
 246
 247 /*
 248  * These are the routines invoked by the control routines to do
 249  * the actual upsampling/conversion.  One row group is processed per call.
 250  *
 251  * Note: since we may be writing directly into application-supplied buffers,
 252  * we have to be honest about the output width; we can't assume the buffer
 253  * has been rounded up to an even width.
 254  */
 255
 256
 257 /*
 258  * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
 259  */
 260
 261 METHODDEF(void)
 262 h2v1_merged_upsample (j_decompress_ptr cinfo,
 263                       JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 264                       JSAMPARRAY output_buf)
 265 {
 266   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 267   register int y, cred, cgreen, cblue;
 268   int cb, cr;
 269   register JSAMPROW outptr;
 270   JSAMPROW inptr0, inptr1, inptr2;
 271   JDIMENSION col;
 272   /* copy these pointers into registers if possible */
 273   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 274   int * Crrtab = upsample->Cr_r_tab;
 275   int * Cbbtab = upsample->Cb_b_tab;
 276   INT32 * Crgtab = upsample->Cr_g_tab;
 277   INT32 * Cbgtab = upsample->Cb_g_tab;
 278   SHIFT_TEMPS
 279
 280   inptr0 = input_buf[0][in_row_group_ctr];
 281   inptr1 = input_buf[1][in_row_group_ctr];
 282   inptr2 = input_buf[2][in_row_group_ctr];
 283   outptr = output_buf[0];
 284   /* Loop for each pair of output pixels */
 285   for (col = cinfo->output_width >> 1; col > 0; col--) {
 286     /* Do the chroma part of the calculation */
 287     cb = GETJSAMPLE(*inptr1++);
 288     cr = GETJSAMPLE(*inptr2++);
 289     cred   = Crrtab[cr];
 290     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 291     cblue  = Cbbtab[cb];
 292     /* Fetch 2 Y values and emit 2 pixels */
 293     y  = GETJSAMPLE(*inptr0++);
 294     outptr[RGB_RED]   = range_limit[y + cred];
 295     outptr[RGB_GREEN] = range_limit[y + cgreen];
 296     outptr[RGB_BLUE]  = range_limit[y + cblue];
 297     outptr += RGB_PIXELSIZE;
 298     y  = GETJSAMPLE(*inptr0++);
 299     outptr[RGB_RED]   = range_limit[y + cred];
 300     outptr[RGB_GREEN] = range_limit[y + cgreen];
 301     outptr[RGB_BLUE]  = range_limit[y + cblue];
 302     outptr += RGB_PIXELSIZE;
 303   }
 304   /* If image width is odd, do the last output column separately */
 305   if (cinfo->output_width & 1) {
 306     cb = GETJSAMPLE(*inptr1);
 307     cr = GETJSAMPLE(*inptr2);
 308     cred   = Crrtab[cr];
 309     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 310     cblue  = Cbbtab[cb];
 311     y  = GETJSAMPLE(*inptr0);
 312     outptr[RGB_RED]   = range_limit[y + cred];
 313     outptr[RGB_GREEN] = range_limit[y + cgreen];
 314     outptr[RGB_BLUE]  = range_limit[y + cblue];
 315   }
 316 }
 317
 318
 319 /*
 320  * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
 321  */
 322
 323 METHODDEF(void)
 324 h2v2_merged_upsample (j_decompress_ptr cinfo,
 325                       JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 326                       JSAMPARRAY output_buf)
 327 {
 328   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 329   register int y, cred, cgreen, cblue;
 330   int cb, cr;
 331   register JSAMPROW outptr0, outptr1;
 332   JSAMPROW inptr00, inptr01, inptr1, inptr2;
 333   JDIMENSION col;
 334   /* copy these pointers into registers if possible */
 335   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 336   int * Crrtab = upsample->Cr_r_tab;
 337   int * Cbbtab = upsample->Cb_b_tab;
 338   INT32 * Crgtab = upsample->Cr_g_tab;
 339   INT32 * Cbgtab = upsample->Cb_g_tab;
 340   SHIFT_TEMPS
 341
 342   inptr00 = input_buf[0][in_row_group_ctr*2];
 343   inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
 344   inptr1 = input_buf[1][in_row_group_ctr];
 345   inptr2 = input_buf[2][in_row_group_ctr];
 346   outptr0 = output_buf[0];
 347   outptr1 = output_buf[1];
 348   /* Loop for each group of output pixels */
 349   for (col = cinfo->output_width >> 1; col > 0; col--) {
 350     /* Do the chroma part of the calculation */
 351     cb = GETJSAMPLE(*inptr1++);
 352     cr = GETJSAMPLE(*inptr2++);
 353     cred   = Crrtab[cr];
 354     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 355     cblue  = Cbbtab[cb];
 356     /* Fetch 4 Y values and emit 4 pixels */
 357     y  = GETJSAMPLE(*inptr00++);
 358     outptr0[RGB_RED]   = range_limit[y + cred];
 359     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 360     outptr0[RGB_BLUE]  = range_limit[y + cblue];
 361     outptr0 += RGB_PIXELSIZE;
 362     y  = GETJSAMPLE(*inptr00++);
 363     outptr0[RGB_RED]   = range_limit[y + cred];
 364     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 365     outptr0[RGB_BLUE]  = range_limit[y + cblue];
 366     outptr0 += RGB_PIXELSIZE;
 367     y  = GETJSAMPLE(*inptr01++);
 368     outptr1[RGB_RED]   = range_limit[y + cred];
 369     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 370     outptr1[RGB_BLUE]  = range_limit[y + cblue];
 371     outptr1 += RGB_PIXELSIZE;
 372     y  = GETJSAMPLE(*inptr01++);
 373     outptr1[RGB_RED]   = range_limit[y + cred];
 374     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 375     outptr1[RGB_BLUE]  = range_limit[y + cblue];
 376     outptr1 += RGB_PIXELSIZE;
 377   }
 378   /* If image width is odd, do the last output column separately */
 379   if (cinfo->output_width & 1) {
 380     cb = GETJSAMPLE(*inptr1);
 381     cr = GETJSAMPLE(*inptr2);
 382     cred   = Crrtab[cr];
 383     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 384     cblue  = Cbbtab[cb];
 385     y  = GETJSAMPLE(*inptr00);
 386     outptr0[RGB_RED]   = range_limit[y + cred];
 387     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 388     outptr0[RGB_BLUE]  = range_limit[y + cblue];
 389     y  = GETJSAMPLE(*inptr01);
 390     outptr1[RGB_RED]   = range_limit[y + cred];
 391     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 392     outptr1[RGB_BLUE]  = range_limit[y + cblue];
 393   }
 394 }
 395
 396
 397 /*
 398  * Module initialization routine for merged upsampling/color conversion.
 399  *
 400  * NB: this is called under the conditions determined by use_merged_upsample()
 401  * in jdmaster.c.  That routine MUST correspond to the actual capabilities
 402  * of this module; no safety checks are made here.
 403  */
 404
 405 GLOBAL(void)
 406 jinit_merged_upsampler (j_decompress_ptr cinfo)
 407 {
 408   my_upsample_ptr upsample;
 409
 410   upsample = (my_upsample_ptr) (*cinfo->mem->alloc_small)
 411     ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_upsampler));
 412   cinfo->upsample = &upsample->pub;
 413   upsample->pub.start_pass = start_pass_merged_upsample;
 414   upsample->pub.need_context_rows = FALSE;
 415
 416   upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
 417
 418   if (cinfo->max_v_samp_factor == 2) {
 419     upsample->pub.upsample = merged_2v_upsample;
 420     upsample->upmethod = h2v2_merged_upsample;
 421     /* Allocate a spare row buffer */
 422     upsample->spare_row = (JSAMPROW) (*cinfo->mem->alloc_large)
 423       ((j_common_ptr) cinfo, JPOOL_IMAGE,
 424        (size_t) upsample->out_row_width * SIZEOF(JSAMPLE));
 425   } else {
 426     upsample->pub.upsample = merged_1v_upsample;
 427     upsample->upmethod = h2v1_merged_upsample;
 428     /* No spare row needed */
 429     upsample->spare_row = NULL;
 430   }
 431
 432   if (cinfo->jpeg_color_space == JCS_BG_YCC)
 433     build_bg_ycc_rgb_table(cinfo);
 434   else
 435     build_ycc_rgb_table(cinfo);
 436 }
 437
 438 #endif /* UPSAMPLE_MERGING_SUPPORTED */