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