1 /*
   2  * jdmerge.c
   3  *
   4  * Copyright (C) 1994-1996, Thomas G. Lane.
   5  * Modified 2013-2017 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 *)
  99     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 100                                 (MAXJSAMPLE+1) * SIZEOF(int));
 101   upsample->Cb_b_tab = (int *)
 102     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 103                                 (MAXJSAMPLE+1) * SIZEOF(int));
 104   upsample->Cr_g_tab = (INT32 *)
 105     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 106                                 (MAXJSAMPLE+1) * SIZEOF(INT32));
 107   upsample->Cb_g_tab = (INT32 *)
 108     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 109                                 (MAXJSAMPLE+1) * SIZEOF(INT32));
 110 
 111   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
 112     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
 113     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
 114     /* Cr=>R value is nearest int to 1.402 * x */
 115     upsample->Cr_r_tab[i] = (int)
 116                     RIGHT_SHIFT(FIX(1.402) * x + ONE_HALF, SCALEBITS);
 117     /* Cb=>B value is nearest int to 1.772 * x */
 118     upsample->Cb_b_tab[i] = (int)
 119                     RIGHT_SHIFT(FIX(1.772) * x + ONE_HALF, SCALEBITS);
 120     /* Cr=>G value is scaled-up -0.714136286 * x */
 121     upsample->Cr_g_tab[i] = (- FIX(0.714136286)) * x;
 122     /* Cb=>G value is scaled-up -0.344136286 * x */
 123     /* We also add in ONE_HALF so that need not do it in inner loop */
 124     upsample->Cb_g_tab[i] = (- FIX(0.344136286)) * x + ONE_HALF;
 125   }
 126 }
 127 
 128 
 129 LOCAL(void)
 130 build_bg_ycc_rgb_table (j_decompress_ptr cinfo)
 131 /* Wide gamut case, bg-sYCC */
 132 {
 133   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 134   int i;
 135   INT32 x;
 136   SHIFT_TEMPS
 137 
 138   upsample->Cr_r_tab = (int *)
 139     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 140                                 (MAXJSAMPLE+1) * SIZEOF(int));
 141   upsample->Cb_b_tab = (int *)
 142     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 143                                 (MAXJSAMPLE+1) * SIZEOF(int));
 144   upsample->Cr_g_tab = (INT32 *)
 145     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 146                                 (MAXJSAMPLE+1) * SIZEOF(INT32));
 147   upsample->Cb_g_tab = (INT32 *)
 148     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 149                                 (MAXJSAMPLE+1) * SIZEOF(INT32));
 150 
 151   for (i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++) {
 152     /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
 153     /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
 154     /* Cr=>R value is nearest int to 2.804 * x */
 155     upsample->Cr_r_tab[i] = (int)
 156                     RIGHT_SHIFT(FIX(2.804) * x + ONE_HALF, SCALEBITS);
 157     /* Cb=>B value is nearest int to 3.544 * x */
 158     upsample->Cb_b_tab[i] = (int)
 159                     RIGHT_SHIFT(FIX(3.544) * x + ONE_HALF, SCALEBITS);
 160     /* Cr=>G value is scaled-up -1.428272572 * x */
 161     upsample->Cr_g_tab[i] = (- FIX(1.428272572)) * x;
 162     /* Cb=>G value is scaled-up -0.688272572 * x */
 163     /* We also add in ONE_HALF so that need not do it in inner loop */
 164     upsample->Cb_g_tab[i] = (- FIX(0.688272572)) * x + ONE_HALF;
 165   }
 166 }
 167 
 168 
 169 /*
 170  * Initialize for an upsampling pass.
 171  */
 172 
 173 METHODDEF(void)
 174 start_pass_merged_upsample (j_decompress_ptr cinfo)
 175 {
 176   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 177 
 178   /* Mark the spare buffer empty */
 179   upsample->spare_full = FALSE;
 180   /* Initialize total-height counter for detecting bottom of image */
 181   upsample->rows_to_go = cinfo->output_height;
 182 }
 183 
 184 
 185 /*
 186  * Control routine to do upsampling (and color conversion).
 187  *
 188  * The control routine just handles the row buffering considerations.
 189  */
 190 
 191 METHODDEF(void)
 192 merged_2v_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 /* 2:1 vertical sampling case: may need a spare row. */
 198 {
 199   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 200   JSAMPROW work_ptrs[2];
 201   JDIMENSION num_rows;          /* number of rows returned to caller */
 202 
 203   if (upsample->spare_full) {
 204     /* If we have a spare row saved from a previous cycle, just return it. */
 205     jcopy_sample_rows(& upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
 206                       1, upsample->out_row_width);
 207     num_rows = 1;
 208     upsample->spare_full = FALSE;
 209   } else {
 210     /* Figure number of rows to return to caller. */
 211     num_rows = 2;
 212     /* Not more than the distance to the end of the image. */
 213     if (num_rows > upsample->rows_to_go)
 214       num_rows = upsample->rows_to_go;
 215     /* And not more than what the client can accept: */
 216     out_rows_avail -= *out_row_ctr;
 217     if (num_rows > out_rows_avail)
 218       num_rows = out_rows_avail;
 219     /* Create output pointer array for upsampler. */
 220     work_ptrs[0] = output_buf[*out_row_ctr];
 221     if (num_rows > 1) {
 222       work_ptrs[1] = output_buf[*out_row_ctr + 1];
 223     } else {
 224       work_ptrs[1] = upsample->spare_row;
 225       upsample->spare_full = TRUE;
 226     }
 227     /* Now do the upsampling. */
 228     (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr, work_ptrs);
 229   }
 230 
 231   /* Adjust counts */
 232   *out_row_ctr += num_rows;
 233   upsample->rows_to_go -= num_rows;
 234   /* When the buffer is emptied, declare this input row group consumed */
 235   if (! upsample->spare_full)
 236     (*in_row_group_ctr)++;
 237 }
 238 
 239 
 240 METHODDEF(void)
 241 merged_1v_upsample (j_decompress_ptr cinfo,
 242                     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
 243                     JDIMENSION in_row_groups_avail,
 244                     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
 245                     JDIMENSION out_rows_avail)
 246 /* 1:1 vertical sampling case: much easier, never need a spare row. */
 247 {
 248   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 249 
 250   /* Just do the upsampling. */
 251   (*upsample->upmethod) (cinfo, input_buf, *in_row_group_ctr,
 252                          output_buf + *out_row_ctr);
 253   /* Adjust counts */
 254   (*out_row_ctr)++;
 255   (*in_row_group_ctr)++;
 256 }
 257 
 258 
 259 /*
 260  * These are the routines invoked by the control routines to do
 261  * the actual upsampling/conversion.  One row group is processed per call.
 262  *
 263  * Note: since we may be writing directly into application-supplied buffers,
 264  * we have to be honest about the output width; we can't assume the buffer
 265  * has been rounded up to an even width.
 266  */
 267 
 268 
 269 /*
 270  * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
 271  */
 272 
 273 METHODDEF(void)
 274 h2v1_merged_upsample (j_decompress_ptr cinfo,
 275                       JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 276                       JSAMPARRAY output_buf)
 277 {
 278   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 279   register int y, cred, cgreen, cblue;
 280   int cb, cr;
 281   register JSAMPROW outptr;
 282   JSAMPROW inptr0, inptr1, inptr2;
 283   JDIMENSION col;
 284   /* copy these pointers into registers if possible */
 285   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 286   int * Crrtab = upsample->Cr_r_tab;
 287   int * Cbbtab = upsample->Cb_b_tab;
 288   INT32 * Crgtab = upsample->Cr_g_tab;
 289   INT32 * Cbgtab = upsample->Cb_g_tab;
 290   SHIFT_TEMPS
 291 
 292   inptr0 = input_buf[0][in_row_group_ctr];
 293   inptr1 = input_buf[1][in_row_group_ctr];
 294   inptr2 = input_buf[2][in_row_group_ctr];
 295   outptr = output_buf[0];
 296   /* Loop for each pair of output pixels */
 297   for (col = cinfo->output_width >> 1; col > 0; col--) {
 298     /* Do the chroma part of the calculation */
 299     cb = GETJSAMPLE(*inptr1++);
 300     cr = GETJSAMPLE(*inptr2++);
 301     cred   = Crrtab[cr];
 302     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 303     cblue  = Cbbtab[cb];
 304     /* Fetch 2 Y values and emit 2 pixels */
 305     y  = GETJSAMPLE(*inptr0++);
 306     outptr[RGB_RED]   = range_limit[y + cred];
 307     outptr[RGB_GREEN] = range_limit[y + cgreen];
 308     outptr[RGB_BLUE]  = range_limit[y + cblue];
 309     outptr += RGB_PIXELSIZE;
 310     y  = GETJSAMPLE(*inptr0++);
 311     outptr[RGB_RED]   = range_limit[y + cred];
 312     outptr[RGB_GREEN] = range_limit[y + cgreen];
 313     outptr[RGB_BLUE]  = range_limit[y + cblue];
 314     outptr += RGB_PIXELSIZE;
 315   }
 316   /* If image width is odd, do the last output column separately */
 317   if (cinfo->output_width & 1) {
 318     cb = GETJSAMPLE(*inptr1);
 319     cr = GETJSAMPLE(*inptr2);
 320     cred   = Crrtab[cr];
 321     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 322     cblue  = Cbbtab[cb];
 323     y  = GETJSAMPLE(*inptr0);
 324     outptr[RGB_RED]   = range_limit[y + cred];
 325     outptr[RGB_GREEN] = range_limit[y + cgreen];
 326     outptr[RGB_BLUE]  = range_limit[y + cblue];
 327   }
 328 }
 329 
 330 
 331 /*
 332  * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
 333  */
 334 
 335 METHODDEF(void)
 336 h2v2_merged_upsample (j_decompress_ptr cinfo,
 337                       JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
 338                       JSAMPARRAY output_buf)
 339 {
 340   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 341   register int y, cred, cgreen, cblue;
 342   int cb, cr;
 343   register JSAMPROW outptr0, outptr1;
 344   JSAMPROW inptr00, inptr01, inptr1, inptr2;
 345   JDIMENSION col;
 346   /* copy these pointers into registers if possible */
 347   register JSAMPLE * range_limit = cinfo->sample_range_limit;
 348   int * Crrtab = upsample->Cr_r_tab;
 349   int * Cbbtab = upsample->Cb_b_tab;
 350   INT32 * Crgtab = upsample->Cr_g_tab;
 351   INT32 * Cbgtab = upsample->Cb_g_tab;
 352   SHIFT_TEMPS
 353 
 354   inptr00 = input_buf[0][in_row_group_ctr*2];
 355   inptr01 = input_buf[0][in_row_group_ctr*2 + 1];
 356   inptr1 = input_buf[1][in_row_group_ctr];
 357   inptr2 = input_buf[2][in_row_group_ctr];
 358   outptr0 = output_buf[0];
 359   outptr1 = output_buf[1];
 360   /* Loop for each group of output pixels */
 361   for (col = cinfo->output_width >> 1; col > 0; col--) {
 362     /* Do the chroma part of the calculation */
 363     cb = GETJSAMPLE(*inptr1++);
 364     cr = GETJSAMPLE(*inptr2++);
 365     cred   = Crrtab[cr];
 366     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 367     cblue  = Cbbtab[cb];
 368     /* Fetch 4 Y values and emit 4 pixels */
 369     y  = GETJSAMPLE(*inptr00++);
 370     outptr0[RGB_RED]   = range_limit[y + cred];
 371     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 372     outptr0[RGB_BLUE]  = range_limit[y + cblue];
 373     outptr0 += RGB_PIXELSIZE;
 374     y  = GETJSAMPLE(*inptr00++);
 375     outptr0[RGB_RED]   = range_limit[y + cred];
 376     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 377     outptr0[RGB_BLUE]  = range_limit[y + cblue];
 378     outptr0 += RGB_PIXELSIZE;
 379     y  = GETJSAMPLE(*inptr01++);
 380     outptr1[RGB_RED]   = range_limit[y + cred];
 381     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 382     outptr1[RGB_BLUE]  = range_limit[y + cblue];
 383     outptr1 += RGB_PIXELSIZE;
 384     y  = GETJSAMPLE(*inptr01++);
 385     outptr1[RGB_RED]   = range_limit[y + cred];
 386     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 387     outptr1[RGB_BLUE]  = range_limit[y + cblue];
 388     outptr1 += RGB_PIXELSIZE;
 389   }
 390   /* If image width is odd, do the last output column separately */
 391   if (cinfo->output_width & 1) {
 392     cb = GETJSAMPLE(*inptr1);
 393     cr = GETJSAMPLE(*inptr2);
 394     cred   = Crrtab[cr];
 395     cgreen = (int) RIGHT_SHIFT(Cbgtab[cb] + Crgtab[cr], SCALEBITS);
 396     cblue  = Cbbtab[cb];
 397     y  = GETJSAMPLE(*inptr00);
 398     outptr0[RGB_RED]   = range_limit[y + cred];
 399     outptr0[RGB_GREEN] = range_limit[y + cgreen];
 400     outptr0[RGB_BLUE]  = range_limit[y + cblue];
 401     y  = GETJSAMPLE(*inptr01);
 402     outptr1[RGB_RED]   = range_limit[y + cred];
 403     outptr1[RGB_GREEN] = range_limit[y + cgreen];
 404     outptr1[RGB_BLUE]  = range_limit[y + cblue];
 405   }
 406 }
 407 
 408 
 409 /*
 410  * Module initialization routine for merged upsampling/color conversion.
 411  *
 412  * NB: this is called under the conditions determined by use_merged_upsample()
 413  * in jdmaster.c.  That routine MUST correspond to the actual capabilities
 414  * of this module; no safety checks are made here.
 415  */
 416 
 417 GLOBAL(void)
 418 jinit_merged_upsampler (j_decompress_ptr cinfo)
 419 {
 420   my_upsample_ptr upsample;
 421 
 422   upsample = (my_upsample_ptr)
 423     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 424                                 SIZEOF(my_upsampler));
 425   cinfo->upsample = &upsample->pub;
 426   upsample->pub.start_pass = start_pass_merged_upsample;
 427   upsample->pub.need_context_rows = FALSE;
 428 
 429   upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;
 430 
 431   if (cinfo->max_v_samp_factor == 2) {
 432     upsample->pub.upsample = merged_2v_upsample;
 433     upsample->upmethod = h2v2_merged_upsample;
 434     /* Allocate a spare row buffer */
 435     upsample->spare_row = (JSAMPROW)
 436       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 437                 (size_t) (upsample->out_row_width * SIZEOF(JSAMPLE)));
 438   } else {
 439     upsample->pub.upsample = merged_1v_upsample;
 440     upsample->upmethod = h2v1_merged_upsample;
 441     /* No spare row needed */
 442     upsample->spare_row = NULL;
 443   }
 444 
 445   if (cinfo->jpeg_color_space == JCS_BG_YCC)
 446     build_bg_ycc_rgb_table(cinfo);
 447   else
 448     build_ycc_rgb_table(cinfo);
 449 }
 450 
 451 #endif /* UPSAMPLE_MERGING_SUPPORTED */