summaryrefslogtreecommitdiffstatshomepage
path: root/src/lib/libjpeg/jdinput.c
blob: 2c5c717b9c31ef0161a64c9004593cf88a5d4c36 (plain) (blame)
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
/*
 * jdinput.c
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * Modified 2002-2009 by Guido Vollbeding.
 * 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 input control logic for the JPEG decompressor.
 * These routines are concerned with controlling the decompressor's input
 * processing (marker reading and coefficient decoding).  The actual input
 * reading is done in jdmarker.c, jdhuff.c, and jdarith.c.
 */

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


/* Private state */

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

  int inheaders;		/* Nonzero until first SOS is reached */
} my_input_controller;

typedef my_input_controller * my_inputctl_ptr;


/* Forward declarations */
METHODDEF(int) consume_markers JPP((j_decompress_ptr cinfo));


/*
 * Routines to calculate various quantities related to the size of the image.
 */


/*
 * Compute output image dimensions and related values.
 * NOTE: this is exported for possible use by application.
 * Hence it mustn't do anything that can't be done twice.
 */

GLOBAL(void)
jpeg_core_output_dimensions (j_decompress_ptr cinfo)
/* Do computations that are needed before master selection phase.
 * This function is used for transcoding and full decompression.
 */
{
#ifdef IDCT_SCALING_SUPPORTED
  int ci;
  jpeg_component_info *compptr;

  /* Compute actual output image dimensions and DCT scaling choices. */
  if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom) {
    /* Provide 1/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 1;
    cinfo->min_DCT_v_scaled_size = 1;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 2) {
    /* Provide 2/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 2L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 2L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 2;
    cinfo->min_DCT_v_scaled_size = 2;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 3) {
    /* Provide 3/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 3L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 3L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 3;
    cinfo->min_DCT_v_scaled_size = 3;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 4) {
    /* Provide 4/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 4L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 4L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 4;
    cinfo->min_DCT_v_scaled_size = 4;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 5) {
    /* Provide 5/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 5L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 5L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 5;
    cinfo->min_DCT_v_scaled_size = 5;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 6) {
    /* Provide 6/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 6L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 6L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 6;
    cinfo->min_DCT_v_scaled_size = 6;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 7) {
    /* Provide 7/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 7L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 7L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 7;
    cinfo->min_DCT_v_scaled_size = 7;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 8) {
    /* Provide 8/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 8L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 8L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 8;
    cinfo->min_DCT_v_scaled_size = 8;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 9) {
    /* Provide 9/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 9L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 9L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 9;
    cinfo->min_DCT_v_scaled_size = 9;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 10) {
    /* Provide 10/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 10L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 10L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 10;
    cinfo->min_DCT_v_scaled_size = 10;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 11) {
    /* Provide 11/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 11L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 11L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 11;
    cinfo->min_DCT_v_scaled_size = 11;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 12) {
    /* Provide 12/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 12L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 12L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 12;
    cinfo->min_DCT_v_scaled_size = 12;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 13) {
    /* Provide 13/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 13L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 13L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 13;
    cinfo->min_DCT_v_scaled_size = 13;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 14) {
    /* Provide 14/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 14L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 14L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 14;
    cinfo->min_DCT_v_scaled_size = 14;
  } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 15) {
    /* Provide 15/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 15L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 15L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 15;
    cinfo->min_DCT_v_scaled_size = 15;
  } else {
    /* Provide 16/block_size scaling */
    cinfo->output_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * 16L, (long) cinfo->block_size);
    cinfo->output_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * 16L, (long) cinfo->block_size);
    cinfo->min_DCT_h_scaled_size = 16;
    cinfo->min_DCT_v_scaled_size = 16;
  }

  /* Recompute dimensions of components */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size;
    compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size;
  }

#else /* !IDCT_SCALING_SUPPORTED */

  /* Hardwire it to "no scaling" */
  cinfo->output_width = cinfo->image_width;
  cinfo->output_height = cinfo->image_height;
  /* jdinput.c has already initialized DCT_scaled_size,
   * and has computed unscaled downsampled_width and downsampled_height.
   */

#endif /* IDCT_SCALING_SUPPORTED */
}


LOCAL(void)
initial_setup (j_decompress_ptr cinfo)
/* Called once, when first SOS marker is reached */
{
  int ci;
  jpeg_component_info *compptr;

  /* Make sure image isn't bigger than I can handle */
  if ((long) cinfo->image_height > (long) JPEG_MAX_DIMENSION ||
      (long) cinfo->image_width > (long) JPEG_MAX_DIMENSION)
    ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) JPEG_MAX_DIMENSION);

  /* For now, precision must match compiled-in value... */
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);

  /* Check that number of components won't exceed internal array sizes */
  if (cinfo->num_components > MAX_COMPONENTS)
    ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
	     MAX_COMPONENTS);

  /* Compute maximum sampling factors; check factor validity */
  cinfo->max_h_samp_factor = 1;
  cinfo->max_v_samp_factor = 1;
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR ||
	compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR)
      ERREXIT(cinfo, JERR_BAD_SAMPLING);
    cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor,
				   compptr->h_samp_factor);
    cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor,
				   compptr->v_samp_factor);
  }

  /* Derive block_size, natural_order, and lim_Se */
  if (cinfo->is_baseline || (cinfo->progressive_mode &&
      cinfo->comps_in_scan)) { /* no pseudo SOS marker */
    cinfo->block_size = DCTSIZE;
    cinfo->natural_order = jpeg_natural_order;
    cinfo->lim_Se = DCTSIZE2-1;
  } else
    switch (cinfo->Se) {
    case (1*1-1):
      cinfo->block_size = 1;
      cinfo->natural_order = jpeg_natural_order; /* not needed */
      cinfo->lim_Se = cinfo->Se;
      break;
    case (2*2-1):
      cinfo->block_size = 2;
      cinfo->natural_order = jpeg_natural_order2;
      cinfo->lim_Se = cinfo->Se;
      break;
    case (3*3-1):
      cinfo->block_size = 3;
      cinfo->natural_order = jpeg_natural_order3;
      cinfo->lim_Se = cinfo->Se;
      break;
    case (4*4-1):
      cinfo->block_size = 4;
      cinfo->natural_order = jpeg_natural_order4;
      cinfo->lim_Se = cinfo->Se;
      break;
    case (5*5-1):
      cinfo->block_size = 5;
      cinfo->natural_order = jpeg_natural_order5;
      cinfo->lim_Se = cinfo->Se;
      break;
    case (6*6-1):
      cinfo->block_size = 6;
      cinfo->natural_order = jpeg_natural_order6;
      cinfo->lim_Se = cinfo->Se;
      break;
    case (7*7-1):
      cinfo->block_size = 7;
      cinfo->natural_order = jpeg_natural_order7;
      cinfo->lim_Se = cinfo->Se;
      break;
    case (8*8-1):
      cinfo->block_size = 8;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (9*9-1):
      cinfo->block_size = 9;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (10*10-1):
      cinfo->block_size = 10;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (11*11-1):
      cinfo->block_size = 11;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (12*12-1):
      cinfo->block_size = 12;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (13*13-1):
      cinfo->block_size = 13;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (14*14-1):
      cinfo->block_size = 14;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (15*15-1):
      cinfo->block_size = 15;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    case (16*16-1):
      cinfo->block_size = 16;
      cinfo->natural_order = jpeg_natural_order;
      cinfo->lim_Se = DCTSIZE2-1;
      break;
    default:
      ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
	       cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
      break;
    }

  /* We initialize DCT_scaled_size and min_DCT_scaled_size to block_size.
   * In the full decompressor,
   * this will be overridden by jpeg_calc_output_dimensions in jdmaster.c;
   * but in the transcoder,
   * jpeg_calc_output_dimensions is not used, so we must do it here.
   */
  cinfo->min_DCT_h_scaled_size = cinfo->block_size;
  cinfo->min_DCT_v_scaled_size = cinfo->block_size;

  /* Compute dimensions of components */
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    compptr->DCT_h_scaled_size = cinfo->block_size;
    compptr->DCT_v_scaled_size = cinfo->block_size;
    /* Size in DCT blocks */
    compptr->width_in_blocks = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
		    (long) (cinfo->max_h_samp_factor * cinfo->block_size));
    compptr->height_in_blocks = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
		    (long) (cinfo->max_v_samp_factor * cinfo->block_size));
    /* downsampled_width and downsampled_height will also be overridden by
     * jdmaster.c if we are doing full decompression.  The transcoder library
     * doesn't use these values, but the calling application might.
     */
    /* Size in samples */
    compptr->downsampled_width = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
		    (long) cinfo->max_h_samp_factor);
    compptr->downsampled_height = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
		    (long) cinfo->max_v_samp_factor);
    /* Mark component needed, until color conversion says otherwise */
    compptr->component_needed = TRUE;
    /* Mark no quantization table yet saved for component */
    compptr->quant_table = NULL;
  }

  /* Compute number of fully interleaved MCU rows. */
  cinfo->total_iMCU_rows = (JDIMENSION)
    jdiv_round_up((long) cinfo->image_height,
	          (long) (cinfo->max_v_samp_factor * cinfo->block_size));

  /* Decide whether file contains multiple scans */
  if (cinfo->comps_in_scan < cinfo->num_components || cinfo->progressive_mode)
    cinfo->inputctl->has_multiple_scans = TRUE;
  else
    cinfo->inputctl->has_multiple_scans = FALSE;
}


LOCAL(void)
per_scan_setup (j_decompress_ptr cinfo)
/* Do computations that are needed before processing a JPEG scan */
/* cinfo->comps_in_scan and cinfo->cur_comp_info[] were set from SOS marker */
{
  int ci, mcublks, tmp;
  jpeg_component_info *compptr;
  
  if (cinfo->comps_in_scan == 1) {
    
    /* Noninterleaved (single-component) scan */
    compptr = cinfo->cur_comp_info[0];
    
    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = compptr->width_in_blocks;
    cinfo->MCU_rows_in_scan = compptr->height_in_blocks;
    
    /* For noninterleaved scan, always one block per MCU */
    compptr->MCU_width = 1;
    compptr->MCU_height = 1;
    compptr->MCU_blocks = 1;
    compptr->MCU_sample_width = compptr->DCT_h_scaled_size;
    compptr->last_col_width = 1;
    /* For noninterleaved scans, it is convenient to define last_row_height
     * as the number of block rows present in the last iMCU row.
     */
    tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
    if (tmp == 0) tmp = compptr->v_samp_factor;
    compptr->last_row_height = tmp;
    
    /* Prepare array describing MCU composition */
    cinfo->blocks_in_MCU = 1;
    cinfo->MCU_membership[0] = 0;
    
  } else {
    
    /* Interleaved (multi-component) scan */
    if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
	       MAX_COMPS_IN_SCAN);
    
    /* Overall image size in MCUs */
    cinfo->MCUs_per_row = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_width,
		    (long) (cinfo->max_h_samp_factor * cinfo->block_size));
    cinfo->MCU_rows_in_scan = (JDIMENSION)
      jdiv_round_up((long) cinfo->image_height,
		    (long) (cinfo->max_v_samp_factor * cinfo->block_size));
    
    cinfo->blocks_in_MCU = 0;
    
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
      compptr = cinfo->cur_comp_info[ci];
      /* Sampling factors give # of blocks of component in each MCU */
      compptr->MCU_width = compptr->h_samp_factor;
      compptr->MCU_height = compptr->v_samp_factor;
      compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
      compptr->MCU_sample_width = compptr->MCU_width * compptr->DCT_h_scaled_size;
      /* Figure number of non-dummy blocks in last MCU column & row */
      tmp = (int) (compptr->width_in_blocks % compptr->MCU_width);
      if (tmp == 0) tmp = compptr->MCU_width;
      compptr->last_col_width = tmp;
      tmp = (int) (compptr->height_in_blocks % compptr->MCU_height);
      if (tmp == 0) tmp = compptr->MCU_height;
      compptr->last_row_height = tmp;
      /* Prepare array describing MCU composition */
      mcublks = compptr->MCU_blocks;
      if (cinfo->blocks_in_MCU + mcublks > D_MAX_BLOCKS_IN_MCU)
	ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
      while (mcublks-- > 0) {
	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
      }
    }
    
  }
}


/*
 * Save away a copy of the Q-table referenced by each component present
 * in the current scan, unless already saved during a prior scan.
 *
 * In a multiple-scan JPEG file, the encoder could assign different components
 * the same Q-table slot number, but change table definitions between scans
 * so that each component uses a different Q-table.  (The IJG encoder is not
 * currently capable of doing this, but other encoders might.)  Since we want
 * to be able to dequantize all the components at the end of the file, this
 * means that we have to save away the table actually used for each component.
 * We do this by copying the table at the start of the first scan containing
 * the component.
 * The JPEG spec prohibits the encoder from changing the contents of a Q-table
 * slot between scans of a component using that slot.  If the encoder does so
 * anyway, this decoder will simply use the Q-table values that were current
 * at the start of the first scan for the component.
 *
 * The decompressor output side looks only at the saved quant tables,
 * not at the current Q-table slots.
 */

LOCAL(void)
latch_quant_tables (j_decompress_ptr cinfo)
{
  int ci, qtblno;
  jpeg_component_info *compptr;
  JQUANT_TBL * qtbl;

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    /* No work if we already saved Q-table for this component */
    if (compptr->quant_table != NULL)
      continue;
    /* Make sure specified quantization table is present */
    qtblno = compptr->quant_tbl_no;
    if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
	cinfo->quant_tbl_ptrs[qtblno] == NULL)
      ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
    /* OK, save away the quantization table */
    qtbl = (JQUANT_TBL *)
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				  SIZEOF(JQUANT_TBL));
    MEMCOPY(qtbl, cinfo->quant_tbl_ptrs[qtblno], SIZEOF(JQUANT_TBL));
    compptr->quant_table = qtbl;
  }
}


/*
 * Initialize the input modules to read a scan of compressed data.
 * The first call to this is done by jdmaster.c after initializing
 * the entire decompressor (during jpeg_start_decompress).
 * Subsequent calls come from consume_markers, below.
 */

METHODDEF(void)
start_input_pass (j_decompress_ptr cinfo)
{
  per_scan_setup(cinfo);
  latch_quant_tables(cinfo);
  (*cinfo->entropy->start_pass) (cinfo);
  (*cinfo->coef->start_input_pass) (cinfo);
  cinfo->inputctl->consume_input = cinfo->coef->consume_data;
}


/*
 * Finish up after inputting a compressed-data scan.
 * This is called by the coefficient controller after it's read all
 * the expected data of the scan.
 */

METHODDEF(void)
finish_input_pass (j_decompress_ptr cinfo)
{
  cinfo->inputctl->consume_input = consume_markers;
}


/*
 * Read JPEG markers before, between, or after compressed-data scans.
 * Change state as necessary when a new scan is reached.
 * Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 *
 * The consume_input method pointer points either here or to the
 * coefficient controller's consume_data routine, depending on whether
 * we are reading a compressed data segment or inter-segment markers.
 *
 * Note: This function should NOT return a pseudo SOS marker (with zero
 * component number) to the caller.  A pseudo marker received by
 * read_markers is processed and then skipped for other markers.
 */

METHODDEF(int)
consume_markers (j_decompress_ptr cinfo)
{
  my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl;
  int val;

  if (inputctl->pub.eoi_reached) /* After hitting EOI, read no further */
    return JPEG_REACHED_EOI;

  for (;;) {			/* Loop to pass pseudo SOS marker */
    val = (*cinfo->marker->read_markers) (cinfo);

    switch (val) {
    case JPEG_REACHED_SOS:	/* Found SOS */
      if (inputctl->inheaders) { /* 1st SOS */
	if (inputctl->inheaders == 1)
	  initial_setup(cinfo);
	if (cinfo->comps_in_scan == 0) { /* pseudo SOS marker */
	  inputctl->inheaders = 2;
	  break;
	}
	inputctl->inheaders = 0;
	/* Note: start_input_pass must be called by jdmaster.c
	 * before any more input can be consumed.  jdapimin.c is
	 * responsible for enforcing this sequencing.
	 */
      } else {			/* 2nd or later SOS marker */
	if (! inputctl->pub.has_multiple_scans)
	  ERREXIT(cinfo, JERR_EOI_EXPECTED); /* Oops, I wasn't expecting this! */
	if (cinfo->comps_in_scan == 0) /* unexpected pseudo SOS marker */
	  break;
	start_input_pass(cinfo);
      }
      return val;
    case JPEG_REACHED_EOI:	/* Found EOI */
      inputctl->pub.eoi_reached = TRUE;
      if (inputctl->inheaders) { /* Tables-only datastream, apparently */
	if (cinfo->marker->saw_SOF)
	  ERREXIT(cinfo, JERR_SOF_NO_SOS);
      } else {
	/* Prevent infinite loop in coef ctlr's decompress_data routine
	 * if user set output_scan_number larger than number of scans.
	 */
	if (cinfo->output_scan_number > cinfo->input_scan_number)
	  cinfo->output_scan_number = cinfo->input_scan_number;
      }
      return val;
    case JPEG_SUSPENDED:
      return val;
    default:
      return val;
    }
  }
}


/*
 * Reset state to begin a fresh datastream.
 */

METHODDEF(void)
reset_input_controller (j_decompress_ptr cinfo)
{
  my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl;

  inputctl->pub.consume_input = consume_markers;
  inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */
  inputctl->pub.eoi_reached = FALSE;
  inputctl->inheaders = 1;
  /* Reset other modules */
  (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
  (*cinfo->marker->reset_marker_reader) (cinfo);
  /* Reset progression state -- would be cleaner if entropy decoder did this */
  cinfo->coef_bits = NULL;
}


/*
 * Initialize the input controller module.
 * This is called only once, when the decompression object is created.
 */

GLOBAL(void)
jinit_input_controller (j_decompress_ptr cinfo)
{
  my_inputctl_ptr inputctl;

  /* Create subobject in permanent pool */
  inputctl = (my_inputctl_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				SIZEOF(my_input_controller));
  cinfo->inputctl = (struct jpeg_input_controller *) inputctl;
  /* Initialize method pointers */
  inputctl->pub.consume_input = consume_markers;
  inputctl->pub.reset_input_controller = reset_input_controller;
  inputctl->pub.start_input_pass = start_input_pass;
  inputctl->pub.finish_input_pass = finish_input_pass;
  /* Initialize state: can't use reset_input_controller since we don't
   * want to try to reset other modules yet.
   */
  inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */
  inputctl->pub.eoi_reached = FALSE;
  inputctl->inheaders = 1;
}