compiler/libjpeg/main/jdmerge.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jdmerge.c
   7  *
   8  * Copyright (C) 1994-1996, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains code for merged upsampling/color conversion.
  13  *
  14  * This file combines functions from jdsample.c and jdcolor.c;
  15  * read those files first to understand what's going on.
  16  *
  17  * When the chroma components are to be upsampled by simple replication
  18  * (ie, box filtering), we can save some work in color conversion by
  19  * calculating all the output pixels corresponding to a pair of chroma
  20  * samples at one time.  In the conversion equations
  21  *      R = Y           + K1 * Cr
  22  *      G = Y + K2 * Cb + K3 * Cr
  23  *      B = Y + K4 * Cb
  24  * only the Y term varies among the group of pixels corresponding to a pair
  25  * of chroma samples, so the rest of the terms can be calculated just once.
  26  * At typical sampling ratios, this eliminates half or three-quarters of the
  27  * multiplications needed for color conversion.
  28  *
  29  * This file currently provides implementations for the following cases:
  30  *      YCbCr => RGB color conversion only.
  31  *      Sampling ratios of 2h1v or 2h2v.
  32  *      No scaling needed at upsample time.
  33  *      Corner-aligned (non-CCIR601) sampling alignment.
  34  * Other special cases could be added, but in most applications these are
  35  * the only common cases.  (For uncommon cases we fall back on the more
  36  * general code in jdsample.c and jdcolor.c.)
  37  */
  38
  39 #define JPEG_INTERNALS
  40 #include "jinclude.h"
  41 #include "jpeglib.h"
  42
  43 #ifdef UPSAMPLE_MERGING_SUPPORTED
  44
  45
  46 /* Private subobject */
  47
  48 typedef struct {
  49   struct jpeg_upsampler pub;    /* public fields */
  50
  51   /* Pointer to routine to do actual upsampling/conversion of one row group */
  52   JMETHOD(void, upmethod, (j_decompress_ptr cinfo,
  53                            JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
  54                            JSAMPARRAY output_buf));
  55
  56   /* Private state for YCC->RGB conversion */
  57   int * Cr_r_tab;               /* => table for Cr to R conversion */
  58   int * Cb_b_tab;               /* => table for Cb to B conversion */
  59   INT32 * Cr_g_tab;             /* => table for Cr to G conversion */
  60   INT32 * Cb_g_tab;             /* => table for Cb to G conversion */
  61
  62   /* For 2:1 vertical sampling, we produce two output rows at a time.
  63    * We need a "spare" row buffer to hold the second output row if the
  64    * application provides just a one-row buffer; we also use the spare
  65    * to discard the dummy last row if the image height is odd.
  66    */
  67   JSAMPROW spare_row;
  68   boolean spare_full;           /* T if spare buffer is occupied */
  69
  70   JDIMENSION out_row_width;     /* samples per output row */
  71   JDIMENSION rows_to_go;        /* counts rows remaining in image */
  72 } my_upsampler;
  73
  74 typedef my_upsampler * my_upsample_ptr;
  75
  76 #define SCALEBITS       16      /* speediest right-shift on some machines */
  77 #define ONE_HALF        ((INT32) 1 << (SCALEBITS-1))
  78 #define FIX(x)          ((INT32) ((x) * (1L<<SCALEBITS) + 0.5))
  79
  80
  81 /*
  82  * Initialize tables for YCC->RGB colorspace conversion.
  83  * This is taken directly from jdcolor.c; see that file for more info.
  84  */
  85
  86 LOCAL(void)
  87 build_ycc_rgb_table (j_decompress_ptr cinfo)
  88 {
  89   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
  90   int i;
  91   INT32 x;
  92   SHIFT_TEMPS
  93
  94   upsample->Cr_r_tab = (int *)
  95     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  96                                 (MAXJSAMPLE+1) * SIZEOF(int));
  97   upsample->Cb_b_tab = (int *)
  98     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  99                                 (MAXJSAMPLE+1) * SIZEOF(int));
 100   upsample->Cr_g_tab = (INT32 *)
 101     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 102                                 (MAXJSAMPLE+1) * SIZEOF(INT32));
 103   upsample->Cb_g_tab = (INT32 *)
 104     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 105                                 (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 1.40200 * x */
 111     upsample->Cr_r_tab[i] = (int)
 112                     RIGHT_SHIFT(FIX(1.40200) * x + ONE_HALF, SCALEBITS);
 113     /* Cb=>B value is nearest int to 1.77200 * x */
 114     upsample->Cb_b_tab[i] = (int)
 115                     RIGHT_SHIFT(FIX(1.77200) * x + ONE_HALF, SCALEBITS);
 116     /* Cr=>G value is scaled-up -0.71414 * x */
 117     upsample->Cr_g_tab[i] = (- FIX(0.71414)) * x;
 118     /* Cb=>G value is scaled-up -0.34414 * x */
 119     /* We also add in ONE_HALF so that need not do it in inner loop */
 120     upsample->Cb_g_tab[i] = (- FIX(0.34414)) * x + ONE_HALF;
 121   }
 122 }
 123
 124
 125 /*
 126  * Initialize for an upsampling pass.
 127  */
 128
 129 METHODDEF(void)
 130 start_pass_merged_upsample (j_decompress_ptr cinfo)
 131 {
 132   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 133
 134   /* Mark the spare buffer empty */
 135   upsample->spare_full = FALSE;
 136   /* Initialize total-height counter for detecting bottom of image */
 137   upsample->rows_to_go = cinfo->output_height;
 138 }
 139
 140
 141 /*
 142  * Control routine to do upsampling (and color conversion).
 143  *
 144  * The control routine just handles the row buffering considerations.
 145  */
 146
 147 METHODDEF(void)
 148 merged_2v_upsample (j_decompress_ptr cinfo,
 149                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 150                     JDIMENSION in_row_groups_avail,
 151                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 152                     JDIMENSION out_rows_avail)
 153 /* 2:1 vertical sampling case: may need a spare row. */
 154 {
 155   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 156   JSAMPROW work_ptrs[2];
 157   JDIMENSION num_rows;          /* number of rows returned to caller */
 158
 159   if (upsample->spare_full) {
 160     /* If we have a spare row saved from a previous cycle, just return it. */
 161     jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
 162                       1, upsample->out_row_width);
 163     num_rows = 1;
 164     upsample->spare_full = FALSE;
 165   } else {
 166     /* Figure number of rows to return to caller. */
 167     num_rows = 2;
 168     /* Not more than the distance to the end of the image. */
 169     if (num_rows > upsample->rows_to_go)
 170       num_rows = upsample->rows_to_go;
 171     /* And not more than what the client can accept: */
 172     out_rows_avail -= *out_row_ctr;
 173     if (num_rows > out_rows_avail)
 174       num_rows = out_rows_avail;
 175     /* Create output pointer array for upsampler. */
 176     work_ptrs[0] = output_buf[*out_row_ctr];
 177     if (num_rows > 1) {
 178       work_ptrs[1] = output_buf[*out_row_ctr + 1];
 179     } else {
 180       work_ptrs[1] = upsample->spare_row;
 181       upsample->spare_full = TRUE;
 182     }
 183     /* Now do the upsampling. */
 184     (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
 185   }
 186
 187   /* Adjust counts */
 188   *out_row_ctr += num_rows;
 189   upsample->rows_to_go -= num_rows;
 190   /* When the buffer is emptied, declare this input row group consumed */
 191   if (! upsample->spare_full)
 192     (*in_row_group_ctr)++;
 193 }
 194
 195
 196 METHODDEF(void)
 197 merged_1v_upsample (j_decompress_ptr cinfo,
 198                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 199                     JDIMENSION in_row_groups_avail,
 200                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 201                     JDIMENSION out_rows_avail)
 202 /* 1:1 vertical sampling case: much easier, never need a spare row. */
 203 {
 204   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 205
 206   /* Just do the upsampling. */
 207   (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
 208                          output_buf + *out_row_ctr);
 209   /* Adjust counts */
 210   (*out_row_ctr)++;
 211   (*in_row_group_ctr)++;
 212 }
 213
 214
 215 /*
 216  * These are the routines invoked by the control routines to do
 217  * the actual upsampling/conversion.  One row group is processed per call.
 218  *
 219  * Note: since we may be writing directly into application-supplied buffers,
 220  * we have to be honest about the output width; we can't assume the buffer
 221  * has been rounded up to an even width.
 222  */
 223
 224
 225 /*
 226  * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
 227  */
 228
 229 METHODDEF(void)
 230 h2v1_merged_upsample (j_decompress_ptr cinfo,
 231                       JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 232                       JSAMPARRAY output_buf)
 233 {
 234   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 235   register int y, cred, cgreen, cblue;
 236   int cb, cr;
 237   register JSAMPROW outptr;
 238   JSAMPROW inptr0, inptr1, inptr2;
 239   JDIMENSION col;
 240   /* copy these pointers into registers if possible */
 241   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 242   int * Crrtab = upsample->Cr_r_tab;
 243   int * Cbbtab = upsample->Cb_b_tab;
 244   INT32 * Crgtab = upsample->Cr_g_tab;
 245   INT32 * Cbgtab = upsample->Cb_g_tab;
 246   SHIFT_TEMPS
 247
 248   inptr0 = input_buf[0][in_row_group_ctr];
 249   inptr1 = input_buf[1][in_row_group_ctr];
 250   inptr2 = input_buf[2][in_row_group_ctr];
 251   outptr = output_buf[0];
 252   /* Loop for each pair of output pixels */
 253   for (col = cinfo->output_width >> 1; col > 0; col--) {
 254     /* Do the chroma part of the calculation */
 255     cb = GETJSAMPLE(*inptr1++);
 256     cr = GETJSAMPLE(*inptr2++);
 257     cred = Crrtab[cr];
 258     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 259     cblue = Cbbtab[cb];
 260     /* Fetch 2 Y values and emit 2 pixels */
 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     y  = GETJSAMPLE(*inptr0++);
 267     outptr[RGB_RED] =   range_limit[y + cred];
 268     outptr[RGB_GREEN] = range_limit[y + cgreen];
 269     outptr[RGB_BLUE] =  range_limit[y + cblue];
 270     outptr += RGB_PIXELSIZE;
 271   }
 272   /* If image width is odd, do the last output column separately */
 273   if (cinfo->output_width & 1) {
 274     cb = GETJSAMPLE(*inptr1);
 275     cr = GETJSAMPLE(*inptr2);
 276     cred = Crrtab[cr];
 277     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 278     cblue = Cbbtab[cb];
 279     y  = GETJSAMPLE(*inptr0);
 280     outptr[RGB_RED] =   range_limit[y + cred];
 281     outptr[RGB_GREEN] = range_limit[y + cgreen];
 282     outptr[RGB_BLUE] =  range_limit[y + cblue];
 283   }
 284 }
 285
 286
 287 /*
 288  * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
 289  */
 290
 291 METHODDEF(void)
 292 h2v2_merged_upsample (j_decompress_ptr cinfo,
 293                       JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 294                       JSAMPARRAY output_buf)
 295 {
 296   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 297   register int y, cred, cgreen, cblue;
 298   int cb, cr;
 299   register JSAMPROW outptr0, outptr1;
 300   JSAMPROW inptr00, inptr01, inptr1, inptr2;
 301   JDIMENSION col;
 302   /* copy these pointers into registers if possible */
 303   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 304   int * Crrtab = upsample->Cr_r_tab;
 305   int * Cbbtab = upsample->Cb_b_tab;
 306   INT32 * Crgtab = upsample->Cr_g_tab;
 307   INT32 * Cbgtab = upsample->Cb_g_tab;
 308   SHIFT_TEMPS
 309
 310   inptr00 = input_buf[0][in_row_group_ctr*2];
 311   inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
 312   inptr1 = input_buf[1][in_row_group_ctr];
 313   inptr2 = input_buf[2][in_row_group_ctr];
 314   outptr0 = output_buf[0];
 315   outptr1 = output_buf[1];
 316   /* Loop for each group of output pixels */
 317   for (col = cinfo->output_width >> 1; col > 0; col--) {
 318     /* Do the chroma part of the calculation */
 319     cb = GETJSAMPLE(*inptr1++);
 320     cr = GETJSAMPLE(*inptr2++);
 321     cred = Crrtab[cr];
 322     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 323     cblue = Cbbtab[cb];
 324     /* Fetch 4 Y values and emit 4 pixels */
 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(*inptr00++);
 331     outptr0[RGB_RED] =   range_limit[y + cred];
 332     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 333     outptr0[RGB_BLUE] =  range_limit[y + cblue];
 334     outptr0 += 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     y  = GETJSAMPLE(*inptr01++);
 341     outptr1[RGB_RED] =   range_limit[y + cred];
 342     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 343     outptr1[RGB_BLUE] =  range_limit[y + cblue];
 344     outptr1 += RGB_PIXELSIZE;
 345   }
 346   /* If image width is odd, do the last output column separately */
 347   if (cinfo->output_width & 1) {
 348     cb = GETJSAMPLE(*inptr1);
 349     cr = GETJSAMPLE(*inptr2);
 350     cred = Crrtab[cr];
 351     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 352     cblue = Cbbtab[cb];
 353     y  = GETJSAMPLE(*inptr00);
 354     outptr0[RGB_RED] =   range_limit[y + cred];
 355     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 356     outptr0[RGB_BLUE] =  range_limit[y + cblue];
 357     y  = GETJSAMPLE(*inptr01);
 358     outptr1[RGB_RED] =   range_limit[y + cred];
 359     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 360     outptr1[RGB_BLUE] =  range_limit[y + cblue];
 361   }
 362 }
 363
 364
 365 /*
 366  * Module initialization routine for merged upsampling/color conversion.
 367  *
 368  * NB: this is called under the conditions determined by use_merged_upsample()
 369  * in jdmaster.c.  That routine MUST correspond to the actual capabilities
 370  * of this module; no safety checks are made here.
 371  */
 372
 373 JGLOBAL(void)
 374 jinit_merged_upsampler (j_decompress_ptr cinfo)
 375 {
 376   my_upsample_ptr upsample;
 377
 378   upsample = (my_upsample_ptr)
 379     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 380                                 SIZEOF(my_upsampler));
 381   cinfo->upsample = (struct jpeg_upsampler *) upsample;
 382   upsample->pub.start_pass = start_pass_merged_upsample;
 383   upsample->pub.need_context_rows = FALSE;
 384
 385   upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
 386
 387   if (cinfo->max_v_samp_factor == 2) {
 388     upsample->pub.upsample = merged_2v_upsample;
 389     upsample->upmethod = h2v2_merged_upsample;
 390     /* Allocate a spare row buffer */
 391     upsample->spare_row = (JSAMPROW)
 392       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 393                 (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
 394   } else {
 395     upsample->pub.upsample = merged_1v_upsample;
 396     upsample->upmethod = h2v1_merged_upsample;
 397     /* No spare row needed */
 398     upsample->spare_row = NULL;
 399   }
 400
 401   build_ycc_rgb_table(cinfo);
 402 }
 403
 404 #endif /* UPSAMPLE_MERGING_SUPPORTED */