media/libjpeg/jdcoefct.c

   1 /*
   2  * jdcoefct.c
   3  *
   4  * This file was part of the Independent JPEG Group's software:
   5  * Copyright (C) 1994-1997, Thomas G. Lane.
   6  * libjpeg-turbo Modifications:
   7  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
   8  * Copyright (C) 2010, 2015-2016, D. R. Commander.
   9  * Copyright (C) 2015, 2020, Google, Inc.
  10  * For conditions of distribution and use, see the accompanying README.ijg
  11  * file.
  12  *
  13  * This file contains the coefficient buffer controller for decompression.
  14  * This controller is the top level of the JPEG decompressor proper.
  15  * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
  16  *
  17  * In buffered-image mode, this controller is the interface between
  18  * input-oriented processing and output-oriented processing.
  19  * Also, the input side (only) is used when reading a file for transcoding.
  20  */
  21
  22 #include "jinclude.h"
  23 #include "jdcoefct.h"
  24 #include "jpegcomp.h"
  25
  26
  27 /* Forward declarations */
  28 METHODDEF(int) decompress_onepass(j_decompress_ptr cinfo,
  29                                   JSAMPIMAGE output_buf);
  30 #ifdef D_MULTISCAN_FILES_SUPPORTED
  31 METHODDEF(int) decompress_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);
  32 #endif
  33 #ifdef BLOCK_SMOOTHING_SUPPORTED
  34 LOCAL(boolean) smoothing_ok(j_decompress_ptr cinfo);
  35 METHODDEF(int) decompress_smooth_data(j_decompress_ptr cinfo,
  36                                       JSAMPIMAGE output_buf);
  37 #endif
  38
  39
  40 /*
  41  * Initialize for an input processing pass.
  42  */
  43
  44 METHODDEF(void)
  45 start_input_pass(j_decompress_ptr cinfo)
  46 {
  47   cinfo->input_iMCU_row = 0;
  48   start_iMCU_row(cinfo);
  49 }
  50
  51
  52 /*
  53  * Initialize for an output processing pass.
  54  */
  55
  56 METHODDEF(void)
  57 start_output_pass(j_decompress_ptr cinfo)
  58 {
  59 #ifdef BLOCK_SMOOTHING_SUPPORTED
  60   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
  61
  62   /* If multipass, check to see whether to use block smoothing on this pass */
  63   if (coef->pub.coef_arrays != NULL) {
  64     if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
  65       coef->pub.decompress_data = decompress_smooth_data;
  66     else
  67       coef->pub.decompress_data = decompress_data;
  68   }
  69 #endif
  70   cinfo->output_iMCU_row = 0;
  71 }
  72
  73
  74 /*
  75  * Decompress and return some data in the single-pass case.
  76  * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
  77  * Input and output must run in lockstep since we have only a one-MCU buffer.
  78  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
  79  *
  80  * NB: output_buf contains a plane for each component in image,
  81  * which we index according to the component's SOF position.
  82  */
  83
  84 METHODDEF(int)
  85 decompress_onepass(j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
  86 {
  87   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
  88   JDIMENSION MCU_col_num;       /* index of current MCU within row */
  89   JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
  90   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
  91   int blkn, ci, xindex, yindex, yoffset, useful_width;
  92   JSAMPARRAY output_ptr;
  93   JDIMENSION start_col, output_col;
  94   jpeg_component_info *compptr;
  95   inverse_DCT_method_ptr inverse_DCT;
  96
  97   /* Loop to process as much as one whole iMCU row */
  98   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
  99        yoffset++) {
 100     for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
 101          MCU_col_num++) {
 102       /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
 103       jzero_far((void *)coef->MCU_buffer[0],
 104                 (size_t)(cinfo->blocks_in_MCU * sizeof(JBLOCK)));
 105       if (!(*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
 106         /* Suspension forced; update state counters and exit */
 107         coef->MCU_vert_offset = yoffset;
 108         coef->MCU_ctr = MCU_col_num;
 109         return JPEG_SUSPENDED;
 110       }
 111
 112       /* Only perform the IDCT on blocks that are contained within the desired
 113        * cropping region.
 114        */
 115       if (MCU_col_num >= cinfo->master->first_iMCU_col &&
 116           MCU_col_num <= cinfo->master->last_iMCU_col) {
 117         /* Determine where data should go in output_buf and do the IDCT thing.
 118          * We skip dummy blocks at the right and bottom edges (but blkn gets
 119          * incremented past them!).  Note the inner loop relies on having
 120          * allocated the MCU_buffer[] blocks sequentially.
 121          */
 122         blkn = 0;               /* index of current DCT block within MCU */
 123         for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 124           compptr = cinfo->cur_comp_info[ci];
 125           /* Don't bother to IDCT an uninteresting component. */
 126           if (!compptr->component_needed) {
 127             blkn += compptr->MCU_blocks;
 128             continue;
 129           }
 130           inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
 131           useful_width = (MCU_col_num < last_MCU_col) ?
 132                          compptr->MCU_width : compptr->last_col_width;
 133           output_ptr = output_buf[compptr->component_index] +
 134                        yoffset * compptr->_DCT_scaled_size;
 135           start_col = (MCU_col_num - cinfo->master->first_iMCU_col) *
 136                       compptr->MCU_sample_width;
 137           for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
 138             if (cinfo->input_iMCU_row < last_iMCU_row ||
 139                 yoffset + yindex < compptr->last_row_height) {
 140               output_col = start_col;
 141               for (xindex = 0; xindex < useful_width; xindex++) {
 142                 (*inverse_DCT) (cinfo, compptr,
 143                                 (JCOEFPTR)coef->MCU_buffer[blkn + xindex],
 144                                 output_ptr, output_col);
 145                 output_col += compptr->_DCT_scaled_size;
 146               }
 147             }
 148             blkn += compptr->MCU_width;
 149             output_ptr += compptr->_DCT_scaled_size;
 150           }
 151         }
 152       }
 153     }
 154     /* Completed an MCU row, but perhaps not an iMCU row */
 155     coef->MCU_ctr = 0;
 156   }
 157   /* Completed the iMCU row, advance counters for next one */
 158   cinfo->output_iMCU_row++;
 159   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
 160     start_iMCU_row(cinfo);
 161     return JPEG_ROW_COMPLETED;
 162   }
 163   /* Completed the scan */
 164   (*cinfo->inputctl->finish_input_pass) (cinfo);
 165   return JPEG_SCAN_COMPLETED;
 166 }
 167
 168
 169 /*
 170  * Dummy consume-input routine for single-pass operation.
 171  */
 172
 173 METHODDEF(int)
 174 dummy_consume_data(j_decompress_ptr cinfo)
 175 {
 176   return JPEG_SUSPENDED;        /* Always indicate nothing was done */
 177 }
 178
 179
 180 #ifdef D_MULTISCAN_FILES_SUPPORTED
 181
 182 /*
 183  * Consume input data and store it in the full-image coefficient buffer.
 184  * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
 185  * ie, v_samp_factor block rows for each component in the scan.
 186  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 187  */
 188
 189 METHODDEF(int)
 190 consume_data(j_decompress_ptr cinfo)
 191 {
 192   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
 193   JDIMENSION MCU_col_num;       /* index of current MCU within row */
 194   int blkn, ci, xindex, yindex, yoffset;
 195   JDIMENSION start_col;
 196   JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
 197   JBLOCKROW buffer_ptr;
 198   jpeg_component_info *compptr;
 199
 200   /* Align the virtual buffers for the components used in this scan. */
 201   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 202     compptr = cinfo->cur_comp_info[ci];
 203     buffer[ci] = (*cinfo->mem->access_virt_barray)
 204       ((j_common_ptr)cinfo, coef->whole_image[compptr->component_index],
 205        cinfo->input_iMCU_row * compptr->v_samp_factor,
 206        (JDIMENSION)compptr->v_samp_factor, TRUE);
 207     /* Note: entropy decoder expects buffer to be zeroed,
 208      * but this is handled automatically by the memory manager
 209      * because we requested a pre-zeroed array.
 210      */
 211   }
 212
 213   /* Loop to process one whole iMCU row */
 214   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
 215        yoffset++) {
 216     for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
 217          MCU_col_num++) {
 218       /* Construct list of pointers to DCT blocks belonging to this MCU */
 219       blkn = 0;                 /* index of current DCT block within MCU */
 220       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 221         compptr = cinfo->cur_comp_info[ci];
 222         start_col = MCU_col_num * compptr->MCU_width;
 223         for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
 224           buffer_ptr = buffer[ci][yindex + yoffset] + start_col;
 225           for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
 226             coef->MCU_buffer[blkn++] = buffer_ptr++;
 227           }
 228         }
 229       }
 230       /* Try to fetch the MCU. */
 231       if (!(*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
 232         /* Suspension forced; update state counters and exit */
 233         coef->MCU_vert_offset = yoffset;
 234         coef->MCU_ctr = MCU_col_num;
 235         return JPEG_SUSPENDED;
 236       }
 237     }
 238     /* Completed an MCU row, but perhaps not an iMCU row */
 239     coef->MCU_ctr = 0;
 240   }
 241   /* Completed the iMCU row, advance counters for next one */
 242   if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
 243     start_iMCU_row(cinfo);
 244     return JPEG_ROW_COMPLETED;
 245   }
 246   /* Completed the scan */
 247   (*cinfo->inputctl->finish_input_pass) (cinfo);
 248   return JPEG_SCAN_COMPLETED;
 249 }
 250
 251
 252 /*
 253  * Decompress and return some data in the multi-pass case.
 254  * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 255  * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 256  *
 257  * NB: output_buf contains a plane for each component in image.
 258  */
 259
 260 METHODDEF(int)
 261 decompress_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
 262 {
 263   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
 264   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 265   JDIMENSION block_num;
 266   int ci, block_row, block_rows;
 267   JBLOCKARRAY buffer;
 268   JBLOCKROW buffer_ptr;
 269   JSAMPARRAY output_ptr;
 270   JDIMENSION output_col;
 271   jpeg_component_info *compptr;
 272   inverse_DCT_method_ptr inverse_DCT;
 273
 274   /* Force some input to be done if we are getting ahead of the input. */
 275   while (cinfo->input_scan_number < cinfo->output_scan_number ||
 276          (cinfo->input_scan_number == cinfo->output_scan_number &&
 277           cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
 278     if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
 279       return JPEG_SUSPENDED;
 280   }
 281
 282   /* OK, output from the virtual arrays. */
 283   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 284        ci++, compptr++) {
 285     /* Don't bother to IDCT an uninteresting component. */
 286     if (!compptr->component_needed)
 287       continue;
 288     /* Align the virtual buffer for this component. */
 289     buffer = (*cinfo->mem->access_virt_barray)
 290       ((j_common_ptr)cinfo, coef->whole_image[ci],
 291        cinfo->output_iMCU_row * compptr->v_samp_factor,
 292        (JDIMENSION)compptr->v_samp_factor, FALSE);
 293     /* Count non-dummy DCT block rows in this iMCU row. */
 294     if (cinfo->output_iMCU_row < last_iMCU_row)
 295       block_rows = compptr->v_samp_factor;
 296     else {
 297       /* NB: can't use last_row_height here; it is input-side-dependent! */
 298       block_rows = (int)(compptr->height_in_blocks % compptr->v_samp_factor);
 299       if (block_rows == 0) block_rows = compptr->v_samp_factor;
 300     }
 301     inverse_DCT = cinfo->idct->inverse_DCT[ci];
 302     output_ptr = output_buf[ci];
 303     /* Loop over all DCT blocks to be processed. */
 304     for (block_row = 0; block_row < block_rows; block_row++) {
 305       buffer_ptr = buffer[block_row] + cinfo->master->first_MCU_col[ci];
 306       output_col = 0;
 307       for (block_num = cinfo->master->first_MCU_col[ci];
 308            block_num <= cinfo->master->last_MCU_col[ci]; block_num++) {
 309         (*inverse_DCT) (cinfo, compptr, (JCOEFPTR)buffer_ptr, output_ptr,
 310                         output_col);
 311         buffer_ptr++;
 312         output_col += compptr->_DCT_scaled_size;
 313       }
 314       output_ptr += compptr->_DCT_scaled_size;
 315     }
 316   }
 317
 318   if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
 319     return JPEG_ROW_COMPLETED;
 320   return JPEG_SCAN_COMPLETED;
 321 }
 322
 323 #endif /* D_MULTISCAN_FILES_SUPPORTED */
 324
 325
 326 #ifdef BLOCK_SMOOTHING_SUPPORTED
 327
 328 /*
 329  * This code applies interblock smoothing as described by section K.8
 330  * of the JPEG standard: the first 5 AC coefficients are estimated from
 331  * the DC values of a DCT block and its 8 neighboring blocks.
 332  * We apply smoothing only for progressive JPEG decoding, and only if
 333  * the coefficients it can estimate are not yet known to full precision.
 334  */
 335
 336 /* Natural-order array positions of the first 5 zigzag-order coefficients */
 337 #define Q01_POS  1
 338 #define Q10_POS  8
 339 #define Q20_POS  16
 340 #define Q11_POS  9
 341 #define Q02_POS  2
 342
 343 /*
 344  * Determine whether block smoothing is applicable and safe.
 345  * We also latch the current states of the coef_bits[] entries for the
 346  * AC coefficients; otherwise, if the input side of the decompressor
 347  * advances into a new scan, we might think the coefficients are known
 348  * more accurately than they really are.
 349  */
 350
 351 LOCAL(boolean)
 352 smoothing_ok(j_decompress_ptr cinfo)
 353 {
 354   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
 355   boolean smoothing_useful = FALSE;
 356   int ci, coefi;
 357   jpeg_component_info *compptr;
 358   JQUANT_TBL *qtable;
 359   int *coef_bits;
 360   int *coef_bits_latch;
 361
 362   if (!cinfo->progressive_mode || cinfo->coef_bits == NULL)
 363     return FALSE;
 364
 365   /* Allocate latch area if not already done */
 366   if (coef->coef_bits_latch == NULL)
 367     coef->coef_bits_latch = (int *)
 368       (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 369                                   cinfo->num_components *
 370                                   (SAVED_COEFS * sizeof(int)));
 371   coef_bits_latch = coef->coef_bits_latch;
 372
 373   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 374        ci++, compptr++) {
 375     /* All components' quantization values must already be latched. */
 376     if ((qtable = compptr->quant_table) == NULL)
 377       return FALSE;
 378     /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
 379     if (qtable->quantval[0] == 0 ||
 380         qtable->quantval[Q01_POS] == 0 ||
 381         qtable->quantval[Q10_POS] == 0 ||
 382         qtable->quantval[Q20_POS] == 0 ||
 383         qtable->quantval[Q11_POS] == 0 ||
 384         qtable->quantval[Q02_POS] == 0)
 385       return FALSE;
 386     /* DC values must be at least partly known for all components. */
 387     coef_bits = cinfo->coef_bits[ci];
 388     if (coef_bits[0] < 0)
 389       return FALSE;
 390     /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
 391     for (coefi = 1; coefi <= 5; coefi++) {
 392       coef_bits_latch[coefi] = coef_bits[coefi];
 393       if (coef_bits[coefi] != 0)
 394         smoothing_useful = TRUE;
 395     }
 396     coef_bits_latch += SAVED_COEFS;
 397   }
 398
 399   return smoothing_useful;
 400 }
 401
 402
 403 /*
 404  * Variant of decompress_data for use when doing block smoothing.
 405  */
 406
 407 METHODDEF(int)
 408 decompress_smooth_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
 409 {
 410   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
 411   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
 412   JDIMENSION block_num, last_block_column;
 413   int ci, block_row, block_rows, access_rows;
 414   JBLOCKARRAY buffer;
 415   JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
 416   JSAMPARRAY output_ptr;
 417   JDIMENSION output_col;
 418   jpeg_component_info *compptr;
 419   inverse_DCT_method_ptr inverse_DCT;
 420   boolean first_row, last_row;
 421   JCOEF *workspace;
 422   int *coef_bits;
 423   JQUANT_TBL *quanttbl;
 424   JLONG Q00, Q01, Q02, Q10, Q11, Q20, num;
 425   int DC1, DC2, DC3, DC4, DC5, DC6, DC7, DC8, DC9;
 426   int Al, pred;
 427
 428   /* Keep a local variable to avoid looking it up more than once */
 429   workspace = coef->workspace;
 430
 431   /* Force some input to be done if we are getting ahead of the input. */
 432   while (cinfo->input_scan_number <= cinfo->output_scan_number &&
 433          !cinfo->inputctl->eoi_reached) {
 434     if (cinfo->input_scan_number == cinfo->output_scan_number) {
 435       /* If input is working on current scan, we ordinarily want it to
 436        * have completed the current row.  But if input scan is DC,
 437        * we want it to keep one row ahead so that next block row's DC
 438        * values are up to date.
 439        */
 440       JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
 441       if (cinfo->input_iMCU_row > cinfo->output_iMCU_row + delta)
 442         break;
 443     }
 444     if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
 445       return JPEG_SUSPENDED;
 446   }
 447
 448   /* OK, output from the virtual arrays. */
 449   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 450        ci++, compptr++) {
 451     /* Don't bother to IDCT an uninteresting component. */
 452     if (!compptr->component_needed)
 453       continue;
 454     /* Count non-dummy DCT block rows in this iMCU row. */
 455     if (cinfo->output_iMCU_row < last_iMCU_row) {
 456       block_rows = compptr->v_samp_factor;
 457       access_rows = block_rows * 2; /* this and next iMCU row */
 458       last_row = FALSE;
 459     } else {
 460       /* NB: can't use last_row_height here; it is input-side-dependent! */
 461       block_rows = (int)(compptr->height_in_blocks % compptr->v_samp_factor);
 462       if (block_rows == 0) block_rows = compptr->v_samp_factor;
 463       access_rows = block_rows; /* this iMCU row only */
 464       last_row = TRUE;
 465     }
 466     /* Align the virtual buffer for this component. */
 467     if (cinfo->output_iMCU_row > 0) {
 468       access_rows += compptr->v_samp_factor; /* prior iMCU row too */
 469       buffer = (*cinfo->mem->access_virt_barray)
 470         ((j_common_ptr)cinfo, coef->whole_image[ci],
 471          (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
 472          (JDIMENSION)access_rows, FALSE);
 473       buffer += compptr->v_samp_factor; /* point to current iMCU row */
 474       first_row = FALSE;
 475     } else {
 476       buffer = (*cinfo->mem->access_virt_barray)
 477         ((j_common_ptr)cinfo, coef->whole_image[ci],
 478          (JDIMENSION)0, (JDIMENSION)access_rows, FALSE);
 479       first_row = TRUE;
 480     }
 481     /* Fetch component-dependent info */
 482     coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
 483     quanttbl = compptr->quant_table;
 484     Q00 = quanttbl->quantval[0];
 485     Q01 = quanttbl->quantval[Q01_POS];
 486     Q10 = quanttbl->quantval[Q10_POS];
 487     Q20 = quanttbl->quantval[Q20_POS];
 488     Q11 = quanttbl->quantval[Q11_POS];
 489     Q02 = quanttbl->quantval[Q02_POS];
 490     inverse_DCT = cinfo->idct->inverse_DCT[ci];
 491     output_ptr = output_buf[ci];
 492     /* Loop over all DCT blocks to be processed. */
 493     for (block_row = 0; block_row < block_rows; block_row++) {
 494       buffer_ptr = buffer[block_row] + cinfo->master->first_MCU_col[ci];
 495       if (first_row && block_row == 0)
 496         prev_block_row = buffer_ptr;
 497       else
 498         prev_block_row = buffer[block_row - 1] +
 499                          cinfo->master->first_MCU_col[ci];
 500       if (last_row && block_row == block_rows - 1)
 501         next_block_row = buffer_ptr;
 502       else
 503         next_block_row = buffer[block_row + 1] +
 504                          cinfo->master->first_MCU_col[ci];
 505       /* We fetch the surrounding DC values using a sliding-register approach.
 506        * Initialize all nine here so as to do the right thing on narrow pics.
 507        */
 508       DC1 = DC2 = DC3 = (int)prev_block_row[0][0];
 509       DC4 = DC5 = DC6 = (int)buffer_ptr[0][0];
 510       DC7 = DC8 = DC9 = (int)next_block_row[0][0];
 511       output_col = 0;
 512       last_block_column = compptr->width_in_blocks - 1;
 513       for (block_num = cinfo->master->first_MCU_col[ci];
 514            block_num <= cinfo->master->last_MCU_col[ci]; block_num++) {
 515         /* Fetch current DCT block into workspace so we can modify it. */
 516         jcopy_block_row(buffer_ptr, (JBLOCKROW)workspace, (JDIMENSION)1);
 517         /* Update DC values */
 518         if (block_num < last_block_column) {
 519           DC3 = (int)prev_block_row[1][0];
 520           DC6 = (int)buffer_ptr[1][0];
 521           DC9 = (int)next_block_row[1][0];
 522         }
 523         /* Compute coefficient estimates per K.8.
 524          * An estimate is applied only if coefficient is still zero,
 525          * and is not known to be fully accurate.
 526          */
 527         /* AC01 */
 528         if ((Al = coef_bits[1]) != 0 && workspace[1] == 0) {
 529           num = 36 * Q00 * (DC4 - DC6);
 530           if (num >= 0) {
 531             pred = (int)(((Q01 << 7) + num) / (Q01 << 8));
 532             if (Al > 0 && pred >= (1 << Al))
 533               pred = (1 << Al) - 1;
 534           } else {
 535             pred = (int)(((Q01 << 7) - num) / (Q01 << 8));
 536             if (Al > 0 && pred >= (1 << Al))
 537               pred = (1 << Al) - 1;
 538             pred = -pred;
 539           }
 540           workspace[1] = (JCOEF)pred;
 541         }
 542         /* AC10 */
 543         if ((Al = coef_bits[2]) != 0 && workspace[8] == 0) {
 544           num = 36 * Q00 * (DC2 - DC8);
 545           if (num >= 0) {
 546             pred = (int)(((Q10 << 7) + num) / (Q10 << 8));
 547             if (Al > 0 && pred >= (1 << Al))
 548               pred = (1 << Al) - 1;
 549           } else {
 550             pred = (int)(((Q10 << 7) - num) / (Q10 << 8));
 551             if (Al > 0 && pred >= (1 << Al))
 552               pred = (1 << Al) - 1;
 553             pred = -pred;
 554           }
 555           workspace[8] = (JCOEF)pred;
 556         }
 557         /* AC20 */
 558         if ((Al = coef_bits[3]) != 0 && workspace[16] == 0) {
 559           num = 9 * Q00 * (DC2 + DC8 - 2 * DC5);
 560           if (num >= 0) {
 561             pred = (int)(((Q20 << 7) + num) / (Q20 << 8));
 562             if (Al > 0 && pred >= (1 << Al))
 563               pred = (1 << Al) - 1;
 564           } else {
 565             pred = (int)(((Q20 << 7) - num) / (Q20 << 8));
 566             if (Al > 0 && pred >= (1 << Al))
 567               pred = (1 << Al) - 1;
 568             pred = -pred;
 569           }
 570           workspace[16] = (JCOEF)pred;
 571         }
 572         /* AC11 */
 573         if ((Al = coef_bits[4]) != 0 && workspace[9] == 0) {
 574           num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
 575           if (num >= 0) {
 576             pred = (int)(((Q11 << 7) + num) / (Q11 << 8));
 577             if (Al > 0 && pred >= (1 << Al))
 578               pred = (1 << Al) - 1;
 579           } else {
 580             pred = (int)(((Q11 << 7) - num) / (Q11 << 8));
 581             if (Al > 0 && pred >= (1 << Al))
 582               pred = (1 << Al) - 1;
 583             pred = -pred;
 584           }
 585           workspace[9] = (JCOEF)pred;
 586         }
 587         /* AC02 */
 588         if ((Al = coef_bits[5]) != 0 && workspace[2] == 0) {
 589           num = 9 * Q00 * (DC4 + DC6 - 2 * DC5);
 590           if (num >= 0) {
 591             pred = (int)(((Q02 << 7) + num) / (Q02 << 8));
 592             if (Al > 0 && pred >= (1 << Al))
 593               pred = (1 << Al) - 1;
 594           } else {
 595             pred = (int)(((Q02 << 7) - num) / (Q02 << 8));
 596             if (Al > 0 && pred >= (1 << Al))
 597               pred = (1 << Al) - 1;
 598             pred = -pred;
 599           }
 600           workspace[2] = (JCOEF)pred;
 601         }
 602         /* OK, do the IDCT */
 603         (*inverse_DCT) (cinfo, compptr, (JCOEFPTR)workspace, output_ptr,
 604                         output_col);
 605         /* Advance for next column */
 606         DC1 = DC2;  DC2 = DC3;
 607         DC4 = DC5;  DC5 = DC6;
 608         DC7 = DC8;  DC8 = DC9;
 609         buffer_ptr++, prev_block_row++, next_block_row++;
 610         output_col += compptr->_DCT_scaled_size;
 611       }
 612       output_ptr += compptr->_DCT_scaled_size;
 613     }
 614   }
 615
 616   if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
 617     return JPEG_ROW_COMPLETED;
 618   return JPEG_SCAN_COMPLETED;
 619 }
 620
 621 #endif /* BLOCK_SMOOTHING_SUPPORTED */
 622
 623
 624 /*
 625  * Initialize coefficient buffer controller.
 626  */
 627
 628 GLOBAL(void)
 629 jinit_d_coef_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
 630 {
 631   my_coef_ptr coef;
 632
 633   coef = (my_coef_ptr)
 634     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 635                                 sizeof(my_coef_controller));
 636   cinfo->coef = (struct jpeg_d_coef_controller *)coef;
 637   coef->pub.start_input_pass = start_input_pass;
 638   coef->pub.start_output_pass = start_output_pass;
 639 #ifdef BLOCK_SMOOTHING_SUPPORTED
 640   coef->coef_bits_latch = NULL;
 641 #endif
 642
 643   /* Create the coefficient buffer. */
 644   if (need_full_buffer) {
 645 #ifdef D_MULTISCAN_FILES_SUPPORTED
 646     /* Allocate a full-image virtual array for each component, */
 647     /* padded to a multiple of samp_factor DCT blocks in each direction. */
 648     /* Note we ask for a pre-zeroed array. */
 649     int ci, access_rows;
 650     jpeg_component_info *compptr;
 651
 652     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 653          ci++, compptr++) {
 654       access_rows = compptr->v_samp_factor;
 655 #ifdef BLOCK_SMOOTHING_SUPPORTED
 656       /* If block smoothing could be used, need a bigger window */
 657       if (cinfo->progressive_mode)
 658         access_rows *= 3;
 659 #endif
 660       coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
 661         ((j_common_ptr)cinfo, JPOOL_IMAGE, TRUE,
 662          (JDIMENSION)jround_up((long)compptr->width_in_blocks,
 663                                (long)compptr->h_samp_factor),
 664          (JDIMENSION)jround_up((long)compptr->height_in_blocks,
 665                                (long)compptr->v_samp_factor),
 666          (JDIMENSION)access_rows);
 667     }
 668     coef->pub.consume_data = consume_data;
 669     coef->pub.decompress_data = decompress_data;
 670     coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
 671 #else
 672     ERREXIT(cinfo, JERR_NOT_COMPILED);
 673 #endif
 674   } else {
 675     /* We only need a single-MCU buffer. */
 676     JBLOCKROW buffer;
 677     int i;
 678
 679     buffer = (JBLOCKROW)
 680       (*cinfo->mem->alloc_large) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 681                                   D_MAX_BLOCKS_IN_MCU * sizeof(JBLOCK));
 682     for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
 683       coef->MCU_buffer[i] = buffer + i;
 684     }
 685     coef->pub.consume_data = dummy_consume_data;
 686     coef->pub.decompress_data = decompress_onepass;
 687     coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
 688   }
 689
 690   /* Allocate the workspace buffer */
 691   coef->workspace = (JCOEF *)
 692     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
 693                                 sizeof(JCOEF) * DCTSIZE2);
 694 }