src/jpeg/jdcoefct.c

   1 /*
   2  * jdcoefct.c
   3  *
   4  * Copyright (C) 1994-1997, 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 the coefficient buffer controller for decompression.
   9  * This controller is the top level of the JPEG decompressor proper.
  10  * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
  11  *
  12  * In buffered-image mode, this controller is the interface between
  13  * input-oriented processing and output-oriented processing.
  14  * Also, the input side (only) is used when reading a file for transcoding.
  15  */
  16
  17 #define JPEG_INTERNALS
  18 #include "jinclude.h"
  19 #include "jpeglib.h"
  20
  21 /* Block smoothing is only applicable for progressive JPEG, so: */
  22 #ifndef D_PROGRESSIVE_SUPPORTED
  23 #undef BLOCK_SMOOTHING_SUPPORTED
  24 #endif
  25
  26 /* Private buffer controller object */
  27
  28 typedef struct {
  29   struct jpeg_d_coef_controller pub; /* public fields */
  30
  31   /* These variables keep track of the current location of the input side. */
  32   /* cinfo->input_iMCU_row is also used for this. */
  33   JDIMENSION MCU_ctr;           /* counts MCUs processed in current row */
  34   int MCU_vert_offset;          /* counts MCU rows within iMCU row */
  35   int MCU_rows_per_iMCU_row;    /* number of such rows needed */
  36
  37   /* The output side's location is represented by cinfo->output_iMCU_row. */
  38
  39   /* In single-pass modes, it's sufficient to buffer just one MCU.
  40    * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
  41    * and let the entropy decoder write into that workspace each time.
  42    * (On 80x86, the workspace is FAR even though it's not really very big;
  43    * this is to keep the module interfaces unchanged when a large coefficient
  44    * buffer is necessary.)
  45    * In multi-pass modes, this array points to the current MCU's blocks
  46    * within the virtual arrays; it is used only by the input side.
  47    */
  48   JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
  49
  50 #ifdef D_MULTISCAN_FILES_SUPPORTED
  51   /* In multi-pass modes, we need a virtual block array for each component. */
  52   jvirt_barray_ptr whole_image[MAX_COMPONENTS];
  53 #endif
  54
  55 #ifdef BLOCK_SMOOTHING_SUPPORTED
  56   /* When doing block smoothing, we latch coefficient Al values here */
  57   int * coef_bits_latch;
  58 #define SAVED_COEFS  6          /* we save coef_bits[0..5] */
  59 #endif
  60 } my_coef_controller;
  61
  62 typedef my_coef_controller * my_coef_ptr;
  63
  64 /* Forward declarations */
  65 METHODDEF(int) decompress_onepass
  66         JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
  67 #ifdef D_MULTISCAN_FILES_SUPPORTED
  68 METHODDEF(int) decompress_data
  69         JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
  70 #endif
  71 #ifdef BLOCK_SMOOTHING_SUPPORTED
  72 LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
  73 METHODDEF(int) decompress_smooth_data
  74         JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
  75 #endif
  76
  77
  78 LOCAL(void)
  79 start_iMCU_row (j_decompress_ptr cinfo)
  80 /* Reset within-iMCU-row counters for a new row (input side) */
  81 {
  82   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  83
  84   /* In an interleaved scan, an MCU row is the same as an iMCU row.
  85    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
  86    * But at the bottom of the image, process only what's left.
  87    */
  88   if (cinfo->comps_in_scan > 1) {
  89     coef->MCU_rows_per_iMCU_row = 1;
  90   } else {
  91     if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
  92       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
  93     else
  94       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
  95   }
  96
  97   coef->MCU_ctr = 0;
  98   coef->MCU_vert_offset = 0;
  99 }
 100
 101
 102 /*
 103  * Initialize for an input processing pass.
 104  */
 105
 106 METHODDEF(void)
 107 #if defined(__VISAGECPP__)
 108 start_input_pass2 (j_decompress_ptr cinfo)
 109 #else
 110 start_input_pass (j_decompress_ptr cinfo)
 111 #endif
 112 {
 113   cinfo->input_iMCU_row = 0;
 114   start_iMCU_row(cinfo);
 115 }
 116
 117 /*
 118  * Initialize for an output processing pass.
 119  */
 120
 121 METHODDEF(void)
 122 start_output_pass (j_decompress_ptr cinfo)
 123 {
 124 #ifdef BLOCK_SMOOTHING_SUPPORTED
 125   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 126
 127   /* If multipass, check to see whether to use block smoothing on this pass */
 128   if (coef->pub.coef_arrays != NULL) {
 129     if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
 130       coef->pub.decompress_data = decompress_smooth_data;
 131     else
 132       coef->pub.decompress_data = decompress_data;
 133   }
 134 #endif
 135   cinfo->output_iMCU_row = 0;
 136 }
 137
 138
 139 /*
 140  * Decompress and return some data in the single-pass case.
 141  * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 142  * Input and output must run in lockstep since we have only a one-MCU buffer.
 143  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 144  *
 145  * NB: output_buf contains a plane for each component in image,
 146  * which we index according to the component's SOF position.
 147  */
 148
 149 METHODDEF(int)
 150 decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
 151 {
 152   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 153   JDIMENSION MCU_col_num;       /* index of current MCU within row */
 154   JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
 155   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 156   int blkn, ci, xindex, yindex, yoffset, useful_width;
 157   JSAMPARRAY output_ptr;
 158   JDIMENSION start_col, output_col;
 159   jpeg_component_info *compptr;
 160   inverse_DCT_method_ptr inverse_DCT;
 161
 162   /* Loop to process as much as one whole iMCU row */
 163   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
 164        yoffset++) {
 165     for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
 166          MCU_col_num++) {
 167       /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
 168       jzero_far((void FAR *) coef->MCU_buffer[0],
 169                 (size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
 170       if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
 171         /* Suspension forced; update state counters and exit */
 172         coef->MCU_vert_offset = yoffset;
 173         coef->MCU_ctr = MCU_col_num;
 174         return JPEG_SUSPENDED;
 175       }
 176       /* Determine where data should go in output_buf and do the IDCT thing.
 177        * We skip dummy blocks at the right and bottom edges (but blkn gets
 178        * incremented past them!).  Note the inner loop relies on having
 179        * allocated the MCU_buffer[] blocks sequentially.
 180        */
 181       blkn = 0;                 /* index of current DCT block within MCU */
 182       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 183         compptr = cinfo->cur_comp_info[ci];
 184         /* Don't bother to IDCT an uninteresting component. */
 185         if (! compptr->component_needed) {
 186           blkn += compptr->MCU_blocks;
 187           continue;
 188         }
 189         inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
 190         useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
 191                                                     : compptr->last_col_width;
 192         output_ptr = output_buf[compptr->component_index] +
 193           yoffset * compptr->DCT_scaled_size;
 194         start_col = MCU_col_num * compptr->MCU_sample_width;
 195         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
 196           if (cinfo->input_iMCU_row < last_iMCU_row ||
 197               yoffset+yindex < compptr->last_row_height) {
 198             output_col = start_col;
 199             for (xindex = 0; xindex < useful_width; xindex++) {
 200               (*inverse_DCT) (cinfo, compptr,
 201                               (JCOEFPTR) coef->MCU_buffer[blkn+xindex],
 202                               output_ptr, output_col);
 203               output_col += compptr->DCT_scaled_size;
 204             }
 205           }
 206           blkn += compptr->MCU_width;
 207           output_ptr += compptr->DCT_scaled_size;
 208         }
 209       }
 210     }
 211     /* Completed an MCU row, but perhaps not an iMCU row */
 212     coef->MCU_ctr = 0;
 213   }
 214   /* Completed the iMCU row, advance counters for next one */
 215   cinfo->output_iMCU_row++;
 216   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
 217     start_iMCU_row(cinfo);
 218     return JPEG_ROW_COMPLETED;
 219   }
 220   /* Completed the scan */
 221   (*cinfo->inputctl->finish_input_pass) (cinfo);
 222   return JPEG_SCAN_COMPLETED;
 223 }
 224
 225
 226 /*
 227  * Dummy consume-input routine for single-pass operation.
 228  */
 229
 230 METHODDEF(int)
 231 dummy_consume_data (j_decompress_ptr cinfo)
 232 {
 233   return JPEG_SUSPENDED;        /* Always indicate nothing was done */
 234 }
 235
 236
 237 #ifdef D_MULTISCAN_FILES_SUPPORTED
 238
 239 /*
 240  * Consume input data and store it in the full-image coefficient buffer.
 241  * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
 242  * ie, v_samp_factor block rows for each component in the scan.
 243  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 244  */
 245
 246 METHODDEF(int)
 247 consume_data (j_decompress_ptr cinfo)
 248 {
 249   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 250   JDIMENSION MCU_col_num;       /* index of current MCU within row */
 251   int blkn, ci, xindex, yindex, yoffset;
 252   JDIMENSION start_col;
 253   JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
 254   JBLOCKROW buffer_ptr;
 255   jpeg_component_info *compptr;
 256
 257   /* Align the virtual buffers for the components used in this scan. */
 258   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 259     compptr = cinfo->cur_comp_info[ci];
 260     buffer[ci] = (*cinfo->mem->access_virt_barray)
 261       ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
 262        cinfo->input_iMCU_row * compptr->v_samp_factor,
 263        (JDIMENSION) compptr->v_samp_factor, TRUE);
 264     /* Note: entropy decoder expects buffer to be zeroed,
 265      * but this is handled automatically by the memory manager
 266      * because we requested a pre-zeroed array.
 267      */
 268   }
 269
 270   /* Loop to process one whole iMCU row */
 271   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
 272        yoffset++) {
 273     for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
 274          MCU_col_num++) {
 275       /* Construct list of pointers to DCT blocks belonging to this MCU */
 276       blkn = 0;                 /* index of current DCT block within MCU */
 277       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 278         compptr = cinfo->cur_comp_info[ci];
 279         start_col = MCU_col_num * compptr->MCU_width;
 280         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
 281           buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
 282           for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
 283             coef->MCU_buffer[blkn++] = buffer_ptr++;
 284           }
 285         }
 286       }
 287       /* Try to fetch the MCU. */
 288       if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
 289         /* Suspension forced; update state counters and exit */
 290         coef->MCU_vert_offset = yoffset;
 291         coef->MCU_ctr = MCU_col_num;
 292         return JPEG_SUSPENDED;
 293       }
 294     }
 295     /* Completed an MCU row, but perhaps not an iMCU row */
 296     coef->MCU_ctr = 0;
 297   }
 298   /* Completed the iMCU row, advance counters for next one */
 299   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
 300     start_iMCU_row(cinfo);
 301     return JPEG_ROW_COMPLETED;
 302   }
 303   /* Completed the scan */
 304   (*cinfo->inputctl->finish_input_pass) (cinfo);
 305   return JPEG_SCAN_COMPLETED;
 306 }
 307
 308
 309 /*
 310  * Decompress and return some data in the multi-pass case.
 311  * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 312  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 313  *
 314  * NB: output_buf contains a plane for each component in image.
 315  */
 316
 317 METHODDEF(int)
 318 decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
 319 {
 320   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 321   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 322   JDIMENSION block_num;
 323   int ci, block_row, block_rows;
 324   JBLOCKARRAY buffer;
 325   JBLOCKROW buffer_ptr;
 326   JSAMPARRAY output_ptr;
 327   JDIMENSION output_col;
 328   jpeg_component_info *compptr;
 329   inverse_DCT_method_ptr inverse_DCT;
 330
 331   /* Force some input to be done if we are getting ahead of the input. */
 332   while (cinfo->input_scan_number < cinfo->output_scan_number ||
 333          (cinfo->input_scan_number == cinfo->output_scan_number &&
 334           cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
 335     if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
 336       return JPEG_SUSPENDED;
 337   }
 338
 339   /* OK, output from the virtual arrays. */
 340   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 341        ci++, compptr++) {
 342     /* Don't bother to IDCT an uninteresting component. */
 343     if (! compptr->component_needed)
 344       continue;
 345     /* Align the virtual buffer for this component. */
 346     buffer = (*cinfo->mem->access_virt_barray)
 347       ((j_common_ptr) cinfo, coef->whole_image[ci],
 348        cinfo->output_iMCU_row * compptr->v_samp_factor,
 349        (JDIMENSION) compptr->v_samp_factor, FALSE);
 350     /* Count non-dummy DCT block rows in this iMCU row. */
 351     if (cinfo->output_iMCU_row < last_iMCU_row)
 352       block_rows = compptr->v_samp_factor;
 353     else {
 354       /* NB: can't use last_row_height here; it is input-side-dependent! */
 355       block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
 356       if (block_rows == 0) block_rows = compptr->v_samp_factor;
 357     }
 358     inverse_DCT = cinfo->idct->inverse_DCT[ci];
 359     output_ptr = output_buf[ci];
 360     /* Loop over all DCT blocks to be processed. */
 361     for (block_row = 0; block_row < block_rows; block_row++) {
 362       buffer_ptr = buffer[block_row];
 363       output_col = 0;
 364       for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {
 365         (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
 366                         output_ptr, output_col);
 367         buffer_ptr++;
 368         output_col += compptr->DCT_scaled_size;
 369       }
 370       output_ptr += compptr->DCT_scaled_size;
 371     }
 372   }
 373
 374   if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
 375     return JPEG_ROW_COMPLETED;
 376   return JPEG_SCAN_COMPLETED;
 377 }
 378
 379 #endif /* D_MULTISCAN_FILES_SUPPORTED */
 380
 381
 382 #ifdef BLOCK_SMOOTHING_SUPPORTED
 383
 384 /*
 385  * This code applies interblock smoothing as described by section K.8
 386  * of the JPEG standard: the first 5 AC coefficients are estimated from
 387  * the DC values of a DCT block and its 8 neighboring blocks.
 388  * We apply smoothing only for progressive JPEG decoding, and only if
 389  * the coefficients it can estimate are not yet known to full precision.
 390  */
 391
 392 /* Natural-order array positions of the first 5 zigzag-order coefficients */
 393 #define Q01_POS  1
 394 #define Q10_POS  8
 395 #define Q20_POS  16
 396 #define Q11_POS  9
 397 #define Q02_POS  2
 398
 399 /*
 400  * Determine whether block smoothing is applicable and safe.
 401  * We also latch the current states of the coef_bits[] entries for the
 402  * AC coefficients; otherwise, if the input side of the decompressor
 403  * advances into a new scan, we might think the coefficients are known
 404  * more accurately than they really are.
 405  */
 406
 407 LOCAL(boolean)
 408 smoothing_ok (j_decompress_ptr cinfo)
 409 {
 410   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 411   boolean smoothing_useful = FALSE;
 412   int ci, coefi;
 413   jpeg_component_info *compptr;
 414   JQUANT_TBL * qtable;
 415   int * coef_bits;
 416   int * coef_bits_latch;
 417
 418   if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
 419     return FALSE;
 420
 421   /* Allocate latch area if not already done */
 422   if (coef->coef_bits_latch == NULL)
 423     coef->coef_bits_latch = (int *)
 424       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 425                                   cinfo->num_components *
 426                                   (SAVED_COEFS * SIZEOF(int)));
 427   coef_bits_latch = coef->coef_bits_latch;
 428
 429   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 430        ci++, compptr++) {
 431     /* All components' quantization values must already be latched. */
 432     if ((qtable = compptr->quant_table) == NULL)
 433       return FALSE;
 434     /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
 435     if (qtable->quantval[0] == 0 ||
 436         qtable->quantval[Q01_POS] == 0 ||
 437         qtable->quantval[Q10_POS] == 0 ||
 438         qtable->quantval[Q20_POS] == 0 ||
 439         qtable->quantval[Q11_POS] == 0 ||
 440         qtable->quantval[Q02_POS] == 0)
 441       return FALSE;
 442     /* DC values must be at least partly known for all components. */
 443     coef_bits = cinfo->coef_bits[ci];
 444     if (coef_bits[0] < 0)
 445       return FALSE;
 446     /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
 447     for (coefi = 1; coefi <= 5; coefi++) {
 448       coef_bits_latch[coefi] = coef_bits[coefi];
 449       if (coef_bits[coefi] != 0)
 450         smoothing_useful = TRUE;
 451     }
 452     coef_bits_latch += SAVED_COEFS;
 453   }
 454
 455   return smoothing_useful;
 456 }
 457
 458
 459 /*
 460  * Variant of decompress_data for use when doing block smoothing.
 461  */
 462
 463 METHODDEF(int)
 464 decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
 465 {
 466   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
 467   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 468   JDIMENSION block_num, last_block_column;
 469   int ci, block_row, block_rows, access_rows;
 470   JBLOCKARRAY buffer;
 471   JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
 472   JSAMPARRAY output_ptr;
 473   JDIMENSION output_col;
 474   jpeg_component_info *compptr;
 475   inverse_DCT_method_ptr inverse_DCT;
 476   boolean first_row, last_row;
 477   JBLOCK workspace;
 478   int *coef_bits;
 479   JQUANT_TBL *quanttbl;
 480   JPEG_INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
 481   int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
 482   int Al, pred;
 483
 484   /* Force some input to be done if we are getting ahead of the input. */
 485   while (cinfo->input_scan_number <= cinfo->output_scan_number &&
 486          ! cinfo->inputctl->eoi_reached) {
 487     if (cinfo->input_scan_number == cinfo->output_scan_number) {
 488       /* If input is working on current scan, we ordinarily want it to
 489        * have completed the current row.  But if input scan is DC,
 490        * we want it to keep one row ahead so that next block row's DC
 491        * values are up to date.
 492        */
 493       JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
 494       if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
 495         break;
 496     }
 497     if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
 498       return JPEG_SUSPENDED;
 499   }
 500
 501   /* OK, output from the virtual arrays. */
 502   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 503        ci++, compptr++) {
 504     /* Don't bother to IDCT an uninteresting component. */
 505     if (! compptr->component_needed)
 506       continue;
 507     /* Count non-dummy DCT block rows in this iMCU row. */
 508     if (cinfo->output_iMCU_row < last_iMCU_row) {
 509       block_rows = compptr->v_samp_factor;
 510       access_rows = block_rows * 2; /* this and next iMCU row */
 511       last_row = FALSE;
 512     } else {
 513       /* NB: can't use last_row_height here; it is input-side-dependent! */
 514       block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
 515       if (block_rows == 0) block_rows = compptr->v_samp_factor;
 516       access_rows = block_rows; /* this iMCU row only */
 517       last_row = TRUE;
 518     }
 519     /* Align the virtual buffer for this component. */
 520     if (cinfo->output_iMCU_row > 0) {
 521       access_rows += compptr->v_samp_factor; /* prior iMCU row too */
 522       buffer = (*cinfo->mem->access_virt_barray)
 523         ((j_common_ptr) cinfo, coef->whole_image[ci],
 524          (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
 525          (JDIMENSION) access_rows, FALSE);
 526       buffer += compptr->v_samp_factor; /* point to current iMCU row */
 527       first_row = FALSE;
 528     } else {
 529       buffer = (*cinfo->mem->access_virt_barray)
 530         ((j_common_ptr) cinfo, coef->whole_image[ci],
 531          (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
 532       first_row = TRUE;
 533     }
 534     /* Fetch component-dependent info */
 535     coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
 536     quanttbl = compptr->quant_table;
 537     Q00 = quanttbl->quantval[0];
 538     Q01 = quanttbl->quantval[Q01_POS];
 539     Q10 = quanttbl->quantval[Q10_POS];
 540     Q20 = quanttbl->quantval[Q20_POS];
 541     Q11 = quanttbl->quantval[Q11_POS];
 542     Q02 = quanttbl->quantval[Q02_POS];
 543     inverse_DCT = cinfo->idct->inverse_DCT[ci];
 544     output_ptr = output_buf[ci];
 545     /* Loop over all DCT blocks to be processed. */
 546     for (block_row = 0; block_row < block_rows; block_row++) {
 547       buffer_ptr = buffer[block_row];
 548       if (first_row && block_row == 0)
 549         prev_block_row = buffer_ptr;
 550       else
 551         prev_block_row = buffer[block_row-1];
 552       if (last_row && block_row == block_rows-1)
 553         next_block_row = buffer_ptr;
 554       else
 555         next_block_row = buffer[block_row+1];
 556       /* We fetch the surrounding DC values using a sliding-register approach.
 557        * Initialize all nine here so as to do the right thing on narrow pics.
 558        */
 559       DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
 560       DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
 561       DC7 = DC8 = DC9 = (int) next_block_row[0][0];
 562       output_col = 0;
 563       last_block_column = compptr->width_in_blocks - 1;
 564       for (block_num = 0; block_num <= last_block_column; block_num++) {
 565         /* Fetch current DCT block into workspace so we can modify it. */
 566         jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
 567         /* Update DC values */
 568         if (block_num < last_block_column) {
 569           DC3 = (int) prev_block_row[1][0];
 570           DC6 = (int) buffer_ptr[1][0];
 571           DC9 = (int) next_block_row[1][0];
 572         }
 573         /* Compute coefficient estimates per K.8.
 574          * An estimate is applied only if coefficient is still zero,
 575          * and is not known to be fully accurate.
 576          */
 577         /* AC01 */
 578         if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {
 579           num = 36 * Q00 * (DC4 - DC6);
 580           if (num >= 0) {
 581             pred = (int) (((Q01<<7) + num) / (Q01<<8));
 582             if (Al > 0 && pred >= (1<<Al))
 583               pred = (1<<Al)-1;
 584           } else {
 585             pred = (int) (((Q01<<7) - num) / (Q01<<8));
 586             if (Al > 0 && pred >= (1<<Al))
 587               pred = (1<<Al)-1;
 588             pred = -pred;
 589           }
 590           workspace[1] = (JCOEF) pred;
 591         }
 592         /* AC10 */
 593         if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {
 594           num = 36 * Q00 * (DC2 - DC8);
 595           if (num >= 0) {
 596             pred = (int) (((Q10<<7) + num) / (Q10<<8));
 597             if (Al > 0 && pred >= (1<<Al))
 598               pred = (1<<Al)-1;
 599           } else {
 600             pred = (int) (((Q10<<7) - num) / (Q10<<8));
 601             if (Al > 0 && pred >= (1<<Al))
 602               pred = (1<<Al)-1;
 603             pred = -pred;
 604           }
 605           workspace[8] = (JCOEF) pred;
 606         }
 607         /* AC20 */
 608         if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {
 609           num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
 610           if (num >= 0) {
 611             pred = (int) (((Q20<<7) + num) / (Q20<<8));
 612             if (Al > 0 && pred >= (1<<Al))
 613               pred = (1<<Al)-1;
 614           } else {
 615             pred = (int) (((Q20<<7) - num) / (Q20<<8));
 616             if (Al > 0 && pred >= (1<<Al))
 617               pred = (1<<Al)-1;
 618             pred = -pred;
 619           }
 620           workspace[16] = (JCOEF) pred;
 621         }
 622         /* AC11 */
 623         if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {
 624           num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
 625           if (num >= 0) {
 626             pred = (int) (((Q11<<7) + num) / (Q11<<8));
 627             if (Al > 0 && pred >= (1<<Al))
 628               pred = (1<<Al)-1;
 629           } else {
 630             pred = (int) (((Q11<<7) - num) / (Q11<<8));
 631             if (Al > 0 && pred >= (1<<Al))
 632               pred = (1<<Al)-1;
 633             pred = -pred;
 634           }
 635           workspace[9] = (JCOEF) pred;
 636         }
 637         /* AC02 */
 638         if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {
 639           num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
 640           if (num >= 0) {
 641             pred = (int) (((Q02<<7) + num) / (Q02<<8));
 642             if (Al > 0 && pred >= (1<<Al))
 643               pred = (1<<Al)-1;
 644           } else {
 645             pred = (int) (((Q02<<7) - num) / (Q02<<8));
 646             if (Al > 0 && pred >= (1<<Al))
 647               pred = (1<<Al)-1;
 648             pred = -pred;
 649           }
 650           workspace[2] = (JCOEF) pred;
 651         }
 652         /* OK, do the IDCT */
 653         (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace,
 654                         output_ptr, output_col);
 655         /* Advance for next column */
 656         DC1 = DC2; DC2 = DC3;
 657         DC4 = DC5; DC5 = DC6;
 658         DC7 = DC8; DC8 = DC9;
 659         buffer_ptr++, prev_block_row++, next_block_row++;
 660         output_col += compptr->DCT_scaled_size;
 661       }
 662       output_ptr += compptr->DCT_scaled_size;
 663     }
 664   }
 665
 666   if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
 667     return JPEG_ROW_COMPLETED;
 668   return JPEG_SCAN_COMPLETED;
 669 }
 670
 671 #endif /* BLOCK_SMOOTHING_SUPPORTED */
 672
 673
 674 /*
 675  * Initialize coefficient buffer controller.
 676  */
 677
 678 GLOBAL(void)
 679 jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
 680 {
 681   my_coef_ptr coef;
 682
 683   coef = (my_coef_ptr)
 684     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 685                                 SIZEOF(my_coef_controller));
 686   cinfo->coef = (struct jpeg_d_coef_controller *) coef;
 687 #if defined(__VISAGECPP__)
 688   coef->pub.start_input_pass2 = start_input_pass2;
 689 #else
 690   coef->pub.start_input_pass = start_input_pass;
 691 #endif
 692
 693   coef->pub.start_output_pass = start_output_pass;
 694 #ifdef BLOCK_SMOOTHING_SUPPORTED
 695   coef->coef_bits_latch = NULL;
 696 #endif
 697
 698   /* Create the coefficient buffer. */
 699   if (need_full_buffer) {
 700 #ifdef D_MULTISCAN_FILES_SUPPORTED
 701     /* Allocate a full-image virtual array for each component, */
 702     /* padded to a multiple of samp_factor DCT blocks in each direction. */
 703     /* Note we ask for a pre-zeroed array. */
 704     int ci, access_rows;
 705     jpeg_component_info *compptr;
 706
 707     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 708          ci++, compptr++) {
 709       access_rows = compptr->v_samp_factor;
 710 #ifdef BLOCK_SMOOTHING_SUPPORTED
 711       /* If block smoothing could be used, need a bigger window */
 712       if (cinfo->progressive_mode)
 713         access_rows *= 3;
 714 #endif
 715       coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
 716         ((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
 717          (JDIMENSION) jround_up((long) compptr->width_in_blocks,
 718                                 (long) compptr->h_samp_factor),
 719          (JDIMENSION) jround_up((long) compptr->height_in_blocks,
 720                                 (long) compptr->v_samp_factor),
 721          (JDIMENSION) access_rows);
 722     }
 723     coef->pub.consume_data = consume_data;
 724     coef->pub.decompress_data = decompress_data;
 725     coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
 726 #else
 727     ERREXIT(cinfo, JERR_NOT_COMPILED);
 728 #endif
 729   } else {
 730     /* We only need a single-MCU buffer. */
 731     JBLOCKROW buffer;
 732     int i;
 733
 734     buffer = (JBLOCKROW)
 735       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 736                                   D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
 737     for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
 738       coef->MCU_buffer[i] = buffer + i;
 739     }
 740     coef->pub.consume_data = dummy_consume_data;
 741     coef->pub.decompress_data = decompress_onepass;
 742     coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
 743   }
 744 }
 745