src/jpeg/jdmerge.c

   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  * 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 */