summaryrefslogtreecommitdiffstats
path: root/src/3rdparty/libjpeg/jdcoefct.c
blob: e3ba6bfaa5b20b9edce51dd5cb8e8d35cace724f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
/*
 * jdcoefct.c
 *
 * Copyright (C) 1994-1997, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the coefficient buffer controller for decompression.
 * This controller is the top level of the JPEG decompressor proper.
 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
 *
 * In buffered-image mode, this controller is the interface between
 * input-oriented processing and output-oriented processing.
 * Also, the input side (only) is used when reading a file for transcoding.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"

/* Block smoothing is only applicable for progressive JPEG, so: */
#ifndef D_PROGRESSIVE_SUPPORTED
#undef BLOCK_SMOOTHING_SUPPORTED
#endif

/* Private buffer controller object */

typedef struct {
  struct jpeg_d_coef_controller pub; /* public fields */

  /* These variables keep track of the current location of the input side. */
  /* cinfo->input_iMCU_row is also used for this. */
  JDIMENSION MCU_ctr;		/* counts MCUs processed in current row */
  int MCU_vert_offset;		/* counts MCU rows within iMCU row */
  int MCU_rows_per_iMCU_row;	/* number of such rows needed */

  /* The output side's location is represented by cinfo->output_iMCU_row. */

  /* In single-pass modes, it's sufficient to buffer just one MCU.
   * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
   * and let the entropy decoder write into that workspace each time.
   * (On 80x86, the workspace is FAR even though it's not really very big;
   * this is to keep the module interfaces unchanged when a large coefficient
   * buffer is necessary.)
   * In multi-pass modes, this array points to the current MCU's blocks
   * within the virtual arrays; it is used only by the input side.
   */
  JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];

#ifdef D_MULTISCAN_FILES_SUPPORTED
  /* In multi-pass modes, we need a virtual block array for each component. */
  jvirt_barray_ptr whole_image[MAX_COMPONENTS];
#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED
  /* When doing block smoothing, we latch coefficient Al values here */
  int * coef_bits_latch;
#define SAVED_COEFS  6		/* we save coef_bits[0..5] */
#endif
} my_coef_controller;

typedef my_coef_controller * my_coef_ptr;

/* Forward declarations */
METHODDEF(int) decompress_onepass
	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#ifdef D_MULTISCAN_FILES_SUPPORTED
METHODDEF(int) decompress_data
	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#endif
#ifdef BLOCK_SMOOTHING_SUPPORTED
LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
METHODDEF(int) decompress_smooth_data
	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
#endif


LOCAL(void)
start_iMCU_row (j_decompress_ptr cinfo)
/* Reset within-iMCU-row counters for a new row (input side) */
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  /* In an interleaved scan, an MCU row is the same as an iMCU row.
   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
   * But at the bottom of the image, process only what's left.
   */
  if (cinfo->comps_in_scan > 1) {
    coef->MCU_rows_per_iMCU_row = 1;
  } else {
    if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
    else
      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
  }

  coef->MCU_ctr = 0;
  coef->MCU_vert_offset = 0;
}


/*
 * Initialize for an input processing pass.
 */

METHODDEF(void)
start_input_pass (j_decompress_ptr cinfo)
{
  cinfo->input_iMCU_row = 0;
  start_iMCU_row(cinfo);
}


/*
 * Initialize for an output processing pass.
 */

METHODDEF(void)
start_output_pass (j_decompress_ptr cinfo)
{
#ifdef BLOCK_SMOOTHING_SUPPORTED
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  /* If multipass, check to see whether to use block smoothing on this pass */
  if (coef->pub.coef_arrays != NULL) {
    if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
      coef->pub.decompress_data = decompress_smooth_data;
    else
      coef->pub.decompress_data = decompress_data;
  }
#endif
  cinfo->output_iMCU_row = 0;
}


/*
 * Decompress and return some data in the single-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Input and output must run in lockstep since we have only a one-MCU buffer.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image,
 * which we index according to the component's SOF position.
 */

METHODDEF(int)
decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION MCU_col_num;	/* index of current MCU within row */
  JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
  int blkn, ci, xindex, yindex, yoffset, useful_width;
  JSAMPARRAY output_ptr;
  JDIMENSION start_col, output_col;
  jpeg_component_info *compptr;
  inverse_DCT_method_ptr inverse_DCT;

  /* Loop to process as much as one whole iMCU row */
  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
       yoffset++) {
    for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
	 MCU_col_num++) {
      /* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
      jzero_far((void FAR *) coef->MCU_buffer[0],
		(size_t) (cinfo->blocks_in_MCU * SIZEOF(JBLOCK)));
      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
	/* Suspension forced; update state counters and exit */
	coef->MCU_vert_offset = yoffset;
	coef->MCU_ctr = MCU_col_num;
	return JPEG_SUSPENDED;
      }
      /* Determine where data should go in output_buf and do the IDCT thing.
       * We skip dummy blocks at the right and bottom edges (but blkn gets
       * incremented past them!).  Note the inner loop relies on having
       * allocated the MCU_buffer[] blocks sequentially.
       */
      blkn = 0;			/* index of current DCT block within MCU */
      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
	compptr = cinfo->cur_comp_info[ci];
	/* Don't bother to IDCT an uninteresting component. */
	if (! compptr->component_needed) {
	  blkn += compptr->MCU_blocks;
	  continue;
	}
	inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
	useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
						    : compptr->last_col_width;
	output_ptr = output_buf[compptr->component_index] +
	  yoffset * compptr->DCT_scaled_size;
	start_col = MCU_col_num * compptr->MCU_sample_width;
	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
	  if (cinfo->input_iMCU_row < last_iMCU_row ||
	      yoffset+yindex < compptr->last_row_height) {
	    output_col = start_col;
	    for (xindex = 0; xindex < useful_width; xindex++) {
	      (*inverse_DCT) (cinfo, compptr,
			      (JCOEFPTR) coef->MCU_buffer[blkn+xindex],
			      output_ptr, output_col);
	      output_col += compptr->DCT_scaled_size;
	    }
	  }
	  blkn += compptr->MCU_width;
	  output_ptr += compptr->DCT_scaled_size;
	}
      }
    }
    /* Completed an MCU row, but perhaps not an iMCU row */
    coef->MCU_ctr = 0;
  }
  /* Completed the iMCU row, advance counters for next one */
  cinfo->output_iMCU_row++;
  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
    start_iMCU_row(cinfo);
    return JPEG_ROW_COMPLETED;
  }
  /* Completed the scan */
  (*cinfo->inputctl->finish_input_pass) (cinfo);
  return JPEG_SCAN_COMPLETED;
}


/*
 * Dummy consume-input routine for single-pass operation.
 */

METHODDEF(int)
dummy_consume_data (j_decompress_ptr cinfo)
{
  return JPEG_SUSPENDED;	/* Always indicate nothing was done */
}


#ifdef D_MULTISCAN_FILES_SUPPORTED

/*
 * Consume input data and store it in the full-image coefficient buffer.
 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
 * ie, v_samp_factor block rows for each component in the scan.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 */

METHODDEF(int)
consume_data (j_decompress_ptr cinfo)
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION MCU_col_num;	/* index of current MCU within row */
  int blkn, ci, xindex, yindex, yoffset;
  JDIMENSION start_col;
  JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
  JBLOCKROW buffer_ptr;
  jpeg_component_info *compptr;

  /* Align the virtual buffers for the components used in this scan. */
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    buffer[ci] = (*cinfo->mem->access_virt_barray)
      ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
       cinfo->input_iMCU_row * compptr->v_samp_factor,
       (JDIMENSION) compptr->v_samp_factor, TRUE);
    /* Note: entropy decoder expects buffer to be zeroed,
     * but this is handled automatically by the memory manager
     * because we requested a pre-zeroed array.
     */
  }

  /* Loop to process one whole iMCU row */
  for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
       yoffset++) {
    for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
	 MCU_col_num++) {
      /* Construct list of pointers to DCT blocks belonging to this MCU */
      blkn = 0;			/* index of current DCT block within MCU */
      for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
	compptr = cinfo->cur_comp_info[ci];
	start_col = MCU_col_num * compptr->MCU_width;
	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
	  buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
	  for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
	    coef->MCU_buffer[blkn++] = buffer_ptr++;
	  }
	}
      }
      /* Try to fetch the MCU. */
      if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
	/* Suspension forced; update state counters and exit */
	coef->MCU_vert_offset = yoffset;
	coef->MCU_ctr = MCU_col_num;
	return JPEG_SUSPENDED;
      }
    }
    /* Completed an MCU row, but perhaps not an iMCU row */
    coef->MCU_ctr = 0;
  }
  /* Completed the iMCU row, advance counters for next one */
  if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
    start_iMCU_row(cinfo);
    return JPEG_ROW_COMPLETED;
  }
  /* Completed the scan */
  (*cinfo->inputctl->finish_input_pass) (cinfo);
  return JPEG_SCAN_COMPLETED;
}


/*
 * Decompress and return some data in the multi-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image.
 */

METHODDEF(int)
decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
  JDIMENSION block_num;
  int ci, block_row, block_rows;
  JBLOCKARRAY buffer;
  JBLOCKROW buffer_ptr;
  JSAMPARRAY output_ptr;
  JDIMENSION output_col;
  jpeg_component_info *compptr;
  inverse_DCT_method_ptr inverse_DCT;

  /* Force some input to be done if we are getting ahead of the input. */
  while (cinfo->input_scan_number < cinfo->output_scan_number ||
	 (cinfo->input_scan_number == cinfo->output_scan_number &&
	  cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
      return JPEG_SUSPENDED;
  }

  /* OK, output from the virtual arrays. */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Don't bother to IDCT an uninteresting component. */
    if (! compptr->component_needed)
      continue;
    /* Align the virtual buffer for this component. */
    buffer = (*cinfo->mem->access_virt_barray)
      ((j_common_ptr) cinfo, coef->whole_image[ci],
       cinfo->output_iMCU_row * compptr->v_samp_factor,
       (JDIMENSION) compptr->v_samp_factor, FALSE);
    /* Count non-dummy DCT block rows in this iMCU row. */
    if (cinfo->output_iMCU_row < last_iMCU_row)
      block_rows = compptr->v_samp_factor;
    else {
      /* NB: can't use last_row_height here; it is input-side-dependent! */
      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
      if (block_rows == 0) block_rows = compptr->v_samp_factor;
    }
    inverse_DCT = cinfo->idct->inverse_DCT[ci];
    output_ptr = output_buf[ci];
    /* Loop over all DCT blocks to be processed. */
    for (block_row = 0; block_row < block_rows; block_row++) {
      buffer_ptr = buffer[block_row];
      output_col = 0;
      for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {
	(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
			output_ptr, output_col);
	buffer_ptr++;
	output_col += compptr->DCT_scaled_size;
      }
      output_ptr += compptr->DCT_scaled_size;
    }
  }

  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
    return JPEG_ROW_COMPLETED;
  return JPEG_SCAN_COMPLETED;
}

#endif /* D_MULTISCAN_FILES_SUPPORTED */


#ifdef BLOCK_SMOOTHING_SUPPORTED

/*
 * This code applies interblock smoothing as described by section K.8
 * of the JPEG standard: the first 5 AC coefficients are estimated from
 * the DC values of a DCT block and its 8 neighboring blocks.
 * We apply smoothing only for progressive JPEG decoding, and only if
 * the coefficients it can estimate are not yet known to full precision.
 */

/* Natural-order array positions of the first 5 zigzag-order coefficients */
#define Q01_POS  1
#define Q10_POS  8
#define Q20_POS  16
#define Q11_POS  9
#define Q02_POS  2

/*
 * Determine whether block smoothing is applicable and safe.
 * We also latch the current states of the coef_bits[] entries for the
 * AC coefficients; otherwise, if the input side of the decompressor
 * advances into a new scan, we might think the coefficients are known
 * more accurately than they really are.
 */

LOCAL(boolean)
smoothing_ok (j_decompress_ptr cinfo)
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  boolean smoothing_useful = FALSE;
  int ci, coefi;
  jpeg_component_info *compptr;
  JTQUANT_TBL * qtable;
  int * coef_bits;
  int * coef_bits_latch;

  if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
    return FALSE;

  /* Allocate latch area if not already done */
  if (coef->coef_bits_latch == NULL)
    coef->coef_bits_latch = (int *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				  cinfo->num_components *
				  (SAVED_COEFS * SIZEOF(int)));
  coef_bits_latch = coef->coef_bits_latch;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* All components' quantization values must already be latched. */
    if ((qtable = compptr->quant_table) == NULL)
      return FALSE;
    /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
    if (qtable->quantval[0] == 0 ||
	qtable->quantval[Q01_POS] == 0 ||
	qtable->quantval[Q10_POS] == 0 ||
	qtable->quantval[Q20_POS] == 0 ||
	qtable->quantval[Q11_POS] == 0 ||
	qtable->quantval[Q02_POS] == 0)
      return FALSE;
    /* DC values must be at least partly known for all components. */
    coef_bits = cinfo->coef_bits[ci];
    if (coef_bits[0] < 0)
      return FALSE;
    /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
    for (coefi = 1; coefi <= 5; coefi++) {
      coef_bits_latch[coefi] = coef_bits[coefi];
      if (coef_bits[coefi] != 0)
	smoothing_useful = TRUE;
    }
    coef_bits_latch += SAVED_COEFS;
  }

  return smoothing_useful;
}


/*
 * Variant of decompress_data for use when doing block smoothing.
 */

METHODDEF(int)
decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
  JDIMENSION block_num, last_block_column;
  int ci, block_row, block_rows, access_rows;
  JBLOCKARRAY buffer;
  JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
  JSAMPARRAY output_ptr;
  JDIMENSION output_col;
  jpeg_component_info *compptr;
  inverse_DCT_method_ptr inverse_DCT;
  boolean first_row, last_row;
  JBLOCK workspace;
  int *coef_bits;
  JTQUANT_TBL *quanttbl;
  INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
  int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
  int Al, pred;

  /* Force some input to be done if we are getting ahead of the input. */
  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
	 ! cinfo->inputctl->eoi_reached) {
    if (cinfo->input_scan_number == cinfo->output_scan_number) {
      /* If input is working on current scan, we ordinarily want it to
       * have completed the current row.  But if input scan is DC,
       * we want it to keep one row ahead so that next block row's DC
       * values are up to date.
       */
      JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
      if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
	break;
    }
    if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
      return JPEG_SUSPENDED;
  }

  /* OK, output from the virtual arrays. */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Don't bother to IDCT an uninteresting component. */
    if (! compptr->component_needed)
      continue;
    /* Count non-dummy DCT block rows in this iMCU row. */
    if (cinfo->output_iMCU_row < last_iMCU_row) {
      block_rows = compptr->v_samp_factor;
      access_rows = block_rows * 2; /* this and next iMCU row */
      last_row = FALSE;
    } else {
      /* NB: can't use last_row_height here; it is input-side-dependent! */
      block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
      if (block_rows == 0) block_rows = compptr->v_samp_factor;
      access_rows = block_rows; /* this iMCU row only */
      last_row = TRUE;
    }
    /* Align the virtual buffer for this component. */
    if (cinfo->output_iMCU_row > 0) {
      access_rows += compptr->v_samp_factor; /* prior iMCU row too */
      buffer = (*cinfo->mem->access_virt_barray)
	((j_common_ptr) cinfo, coef->whole_image[ci],
	 (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
	 (JDIMENSION) access_rows, FALSE);
      buffer += compptr->v_samp_factor;	/* point to current iMCU row */
      first_row = FALSE;
    } else {
      buffer = (*cinfo->mem->access_virt_barray)
	((j_common_ptr) cinfo, coef->whole_image[ci],
	 (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
      first_row = TRUE;
    }
    /* Fetch component-dependent info */
    coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
    quanttbl = compptr->quant_table;
    Q00 = quanttbl->quantval[0];
    Q01 = quanttbl->quantval[Q01_POS];
    Q10 = quanttbl->quantval[Q10_POS];
    Q20 = quanttbl->quantval[Q20_POS];
    Q11 = quanttbl->quantval[Q11_POS];
    Q02 = quanttbl->quantval[Q02_POS];
    inverse_DCT = cinfo->idct->inverse_DCT[ci];
    output_ptr = output_buf[ci];
    /* Loop over all DCT blocks to be processed. */
    for (block_row = 0; block_row < block_rows; block_row++) {
      buffer_ptr = buffer[block_row];
      if (first_row && block_row == 0)
	prev_block_row = buffer_ptr;
      else
	prev_block_row = buffer[block_row-1];
      if (last_row && block_row == block_rows-1)
	next_block_row = buffer_ptr;
      else
	next_block_row = buffer[block_row+1];
      /* We fetch the surrounding DC values using a sliding-register approach.
       * Initialize all nine here so as to do the right thing on narrow pics.
       */
      DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
      DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
      DC7 = DC8 = DC9 = (int) next_block_row[0][0];
      output_col = 0;
      last_block_column = compptr->width_in_blocks - 1;
      for (block_num = 0; block_num <= last_block_column; block_num++) {
	/* Fetch current DCT block into workspace so we can modify it. */
	jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
	/* Update DC values */
	if (block_num < last_block_column) {
	  DC3 = (int) prev_block_row[1][0];
	  DC6 = (int) buffer_ptr[1][0];
	  DC9 = (int) next_block_row[1][0];
	}
	/* Compute coefficient estimates per K.8.
	 * An estimate is applied only if coefficient is still zero,
	 * and is not known to be fully accurate.
	 */
	/* AC01 */
	if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {
	  num = 36 * Q00 * (DC4 - DC6);
	  if (num >= 0) {
	    pred = (int) (((Q01<<7) + num) / (Q01<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	  } else {
	    pred = (int) (((Q01<<7) - num) / (Q01<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	    pred = -pred;
	  }
	  workspace[1] = (JCOEF) pred;
	}
	/* AC10 */
	if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {
	  num = 36 * Q00 * (DC2 - DC8);
	  if (num >= 0) {
	    pred = (int) (((Q10<<7) + num) / (Q10<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	  } else {
	    pred = (int) (((Q10<<7) - num) / (Q10<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	    pred = -pred;
	  }
	  workspace[8] = (JCOEF) pred;
	}
	/* AC20 */
	if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {
	  num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
	  if (num >= 0) {
	    pred = (int) (((Q20<<7) + num) / (Q20<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	  } else {
	    pred = (int) (((Q20<<7) - num) / (Q20<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	    pred = -pred;
	  }
	  workspace[16] = (JCOEF) pred;
	}
	/* AC11 */
	if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {
	  num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
	  if (num >= 0) {
	    pred = (int) (((Q11<<7) + num) / (Q11<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	  } else {
	    pred = (int) (((Q11<<7) - num) / (Q11<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	    pred = -pred;
	  }
	  workspace[9] = (JCOEF) pred;
	}
	/* AC02 */
	if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {
	  num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
	  if (num >= 0) {
	    pred = (int) (((Q02<<7) + num) / (Q02<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	  } else {
	    pred = (int) (((Q02<<7) - num) / (Q02<<8));
	    if (Al > 0 && pred >= (1<<Al))
	      pred = (1<<Al)-1;
	    pred = -pred;
	  }
	  workspace[2] = (JCOEF) pred;
	}
	/* OK, do the IDCT */
	(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace,
			output_ptr, output_col);
	/* Advance for next column */
	DC1 = DC2; DC2 = DC3;
	DC4 = DC5; DC5 = DC6;
	DC7 = DC8; DC8 = DC9;
	buffer_ptr++, prev_block_row++, next_block_row++;
	output_col += compptr->DCT_scaled_size;
      }
      output_ptr += compptr->DCT_scaled_size;
    }
  }

  if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
    return JPEG_ROW_COMPLETED;
  return JPEG_SCAN_COMPLETED;
}

#endif /* BLOCK_SMOOTHING_SUPPORTED */


/*
 * Initialize coefficient buffer controller.
 */

GLOBAL(void)
jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
{
  my_coef_ptr coef;

  coef = (my_coef_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_coef_controller));
  cinfo->coef = (struct jpeg_d_coef_controller *) coef;
  coef->pub.start_input_pass = start_input_pass;
  coef->pub.start_output_pass = start_output_pass;
#ifdef BLOCK_SMOOTHING_SUPPORTED
  coef->coef_bits_latch = NULL;
#endif

  /* Create the coefficient buffer. */
  if (need_full_buffer) {
#ifdef D_MULTISCAN_FILES_SUPPORTED
    /* Allocate a full-image virtual array for each component, */
    /* padded to a multiple of samp_factor DCT blocks in each direction. */
    /* Note we ask for a pre-zeroed array. */
    int ci, access_rows;
    jpeg_component_info *compptr;

    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
	 ci++, compptr++) {
      access_rows = compptr->v_samp_factor;
#ifdef BLOCK_SMOOTHING_SUPPORTED
      /* If block smoothing could be used, need a bigger window */
      if (cinfo->progressive_mode)
	access_rows *= 3;
#endif
      coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
	((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
	 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
				(long) compptr->h_samp_factor),
	 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
				(long) compptr->v_samp_factor),
	 (JDIMENSION) access_rows);
    }
    coef->pub.consume_data = consume_data;
    coef->pub.decompress_data = decompress_data;
    coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
  } else {
    /* We only need a single-MCU buffer. */
    JBLOCKROW buffer;
    int i;

    buffer = (JBLOCKROW)
      (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				  D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
    for (i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) {
      coef->MCU_buffer[i] = buffer + i;
    }
    coef->pub.consume_data = dummy_consume_data;
    coef->pub.decompress_data = decompress_onepass;
    coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
  }
}