4
* Copyright (C) 1991-1997, Thomas G. Lane.
5
* Modified 2002-2011 by Guido Vollbeding.
6
* This file is part of the Independent JPEG Group's software.
7
* For conditions of distribution and use, see the accompanying README file.
9
* This file contains master control logic for the JPEG decompressor.
10
* These routines are concerned with selecting the modules to be executed
11
* and with determining the number of passes and the work to be done in each
15
#define JPEG_INTERNALS
23
struct jpeg_decomp_master pub; /* public fields */
25
int pass_number; /* # of passes completed */
27
boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */
29
/* Saved references to initialized quantizer modules,
30
* in case we need to switch modes.
32
struct jpeg_color_quantizer * quantizer_1pass;
33
struct jpeg_color_quantizer * quantizer_2pass;
36
typedef my_decomp_master * my_master_ptr;
40
* Determine whether merged upsample/color conversion should be used.
41
* CRUCIAL: this must match the actual capabilities of jdmerge.c!
45
use_merged_upsample (j_decompress_ptr cinfo)
47
#ifdef UPSAMPLE_MERGING_SUPPORTED
48
/* Merging is the equivalent of plain box-filter upsampling */
49
if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
51
/* jdmerge.c only supports YCC=>RGB color conversion */
52
if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 ||
53
cinfo->out_color_space != JCS_RGB ||
54
cinfo->out_color_components != RGB_PIXELSIZE)
56
/* and it only handles 2h1v or 2h2v sampling ratios */
57
if (cinfo->comp_info[0].h_samp_factor != 2 ||
58
cinfo->comp_info[1].h_samp_factor != 1 ||
59
cinfo->comp_info[2].h_samp_factor != 1 ||
60
cinfo->comp_info[0].v_samp_factor > 2 ||
61
cinfo->comp_info[1].v_samp_factor != 1 ||
62
cinfo->comp_info[2].v_samp_factor != 1)
64
/* furthermore, it doesn't work if we've scaled the IDCTs differently */
65
if (cinfo->comp_info[0].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
66
cinfo->comp_info[1].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
67
cinfo->comp_info[2].DCT_h_scaled_size != cinfo->min_DCT_h_scaled_size ||
68
cinfo->comp_info[0].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
69
cinfo->comp_info[1].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size ||
70
cinfo->comp_info[2].DCT_v_scaled_size != cinfo->min_DCT_v_scaled_size)
72
/* ??? also need to test for upsample-time rescaling, when & if supported */
73
return TRUE; /* by golly, it'll work... */
81
* Compute output image dimensions and related values.
82
* NOTE: this is exported for possible use by application.
83
* Hence it mustn't do anything that can't be done twice.
84
* Also note that it may be called before the master module is initialized!
88
jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
89
/* Do computations that are needed before master selection phase.
90
* This function is used for full decompression.
93
#ifdef IDCT_SCALING_SUPPORTED
95
jpeg_component_info *compptr;
98
/* Prevent application from calling me at wrong times */
99
if (cinfo->global_state != DSTATE_READY)
100
ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
102
/* Compute core output image dimensions and DCT scaling choices. */
103
jpeg_core_output_dimensions(cinfo);
105
#ifdef IDCT_SCALING_SUPPORTED
107
/* In selecting the actual DCT scaling for each component, we try to
108
* scale up the chroma components via IDCT scaling rather than upsampling.
109
* This saves time if the upsampler gets to use 1:1 scaling.
110
* Note this code adapts subsampling ratios which are powers of 2.
112
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
115
while (cinfo->min_DCT_h_scaled_size * ssize <=
116
(cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
117
(cinfo->max_h_samp_factor % (compptr->h_samp_factor * ssize * 2)) == 0) {
120
compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size * ssize;
122
while (cinfo->min_DCT_v_scaled_size * ssize <=
123
(cinfo->do_fancy_upsampling ? DCTSIZE : DCTSIZE / 2) &&
124
(cinfo->max_v_samp_factor % (compptr->v_samp_factor * ssize * 2)) == 0) {
127
compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size * ssize;
129
/* We don't support IDCT ratios larger than 2. */
130
if (compptr->DCT_h_scaled_size > compptr->DCT_v_scaled_size * 2)
131
compptr->DCT_h_scaled_size = compptr->DCT_v_scaled_size * 2;
132
else if (compptr->DCT_v_scaled_size > compptr->DCT_h_scaled_size * 2)
133
compptr->DCT_v_scaled_size = compptr->DCT_h_scaled_size * 2;
136
/* Recompute downsampled dimensions of components;
137
* application needs to know these if using raw downsampled data.
139
for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
141
/* Size in samples, after IDCT scaling */
142
compptr->downsampled_width = (JDIMENSION)
143
jdiv_round_up((long) cinfo->image_width *
144
(long) (compptr->h_samp_factor * compptr->DCT_h_scaled_size),
145
(long) (cinfo->max_h_samp_factor * cinfo->block_size));
146
compptr->downsampled_height = (JDIMENSION)
147
jdiv_round_up((long) cinfo->image_height *
148
(long) (compptr->v_samp_factor * compptr->DCT_v_scaled_size),
149
(long) (cinfo->max_v_samp_factor * cinfo->block_size));
152
#endif /* IDCT_SCALING_SUPPORTED */
154
/* Report number of components in selected colorspace. */
155
/* Probably this should be in the color conversion module... */
156
switch (cinfo->out_color_space) {
158
cinfo->out_color_components = 1;
161
cinfo->out_color_components = RGB_PIXELSIZE;
164
cinfo->out_color_components = 3;
168
cinfo->out_color_components = 4;
170
default: /* else must be same colorspace as in file */
171
cinfo->out_color_components = cinfo->num_components;
174
cinfo->output_components = (cinfo->quantize_colors ? 1 :
175
cinfo->out_color_components);
177
/* See if upsampler will want to emit more than one row at a time */
178
if (use_merged_upsample(cinfo))
179
cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
181
cinfo->rec_outbuf_height = 1;
186
* Several decompression processes need to range-limit values to the range
187
* 0..MAXJSAMPLE; the input value may fall somewhat outside this range
188
* due to noise introduced by quantization, roundoff error, etc. These
189
* processes are inner loops and need to be as fast as possible. On most
190
* machines, particularly CPUs with pipelines or instruction prefetch,
191
* a (subscript-check-less) C table lookup
192
* x = sample_range_limit[x];
193
* is faster than explicit tests
195
* else if (x > MAXJSAMPLE) x = MAXJSAMPLE;
196
* These processes all use a common table prepared by the routine below.
198
* For most steps we can mathematically guarantee that the initial value
199
* of x is within MAXJSAMPLE+1 of the legal range, so a table running from
200
* -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial
201
* limiting step (just after the IDCT), a wildly out-of-range value is
202
* possible if the input data is corrupt. To avoid any chance of indexing
203
* off the end of memory and getting a bad-pointer trap, we perform the
204
* post-IDCT limiting thus:
205
* x = range_limit[x & MASK];
206
* where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
207
* samples. Under normal circumstances this is more than enough range and
208
* a correct output will be generated; with bogus input data the mask will
209
* cause wraparound, and we will safely generate a bogus-but-in-range output.
210
* For the post-IDCT step, we want to convert the data from signed to unsigned
211
* representation by adding CENTERJSAMPLE at the same time that we limit it.
212
* So the post-IDCT limiting table ends up looking like this:
213
* CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
214
* MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
215
* 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
216
* 0,1,...,CENTERJSAMPLE-1
217
* Negative inputs select values from the upper half of the table after
220
* We can save some space by overlapping the start of the post-IDCT table
221
* with the simpler range limiting table. The post-IDCT table begins at
222
* sample_range_limit + CENTERJSAMPLE.
224
* Note that the table is allocated in near data space on PCs; it's small
225
* enough and used often enough to justify this.
229
prepare_range_limit_table (j_decompress_ptr cinfo)
230
/* Allocate and fill in the sample_range_limit table */
236
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
237
(5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE));
238
table += (MAXJSAMPLE+1); /* allow negative subscripts of simple table */
239
cinfo->sample_range_limit = table;
240
/* First segment of "simple" table: limit[x] = 0 for x < 0 */
241
MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE));
242
/* Main part of "simple" table: limit[x] = x */
243
for (i = 0; i <= MAXJSAMPLE; i++)
244
table[i] = (JSAMPLE) i;
245
table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */
246
/* End of simple table, rest of first half of post-IDCT table */
247
for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++)
248
table[i] = MAXJSAMPLE;
249
/* Second half of post-IDCT table */
250
MEMZERO(table + (2 * (MAXJSAMPLE+1)),
251
(2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE));
252
MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE),
253
cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE));
258
* Master selection of decompression modules.
259
* This is done once at jpeg_start_decompress time. We determine
260
* which modules will be used and give them appropriate initialization calls.
261
* We also initialize the decompressor input side to begin consuming data.
263
* Since jpeg_read_header has finished, we know what is in the SOF
264
* and (first) SOS markers. We also have all the application parameter
269
master_selection (j_decompress_ptr cinfo)
271
my_master_ptr master = (my_master_ptr) cinfo->master;
272
boolean use_c_buffer;
274
JDIMENSION jd_samplesperrow;
276
/* Initialize dimensions and other stuff */
277
jpeg_calc_output_dimensions(cinfo);
278
prepare_range_limit_table(cinfo);
280
/* Width of an output scanline must be representable as JDIMENSION. */
281
samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
282
jd_samplesperrow = (JDIMENSION) samplesperrow;
283
if ((long) jd_samplesperrow != samplesperrow)
284
ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
286
/* Initialize my private state */
287
master->pass_number = 0;
288
master->using_merged_upsample = use_merged_upsample(cinfo);
290
/* Color quantizer selection */
291
master->quantizer_1pass = NULL;
292
master->quantizer_2pass = NULL;
293
/* No mode changes if not using buffered-image mode. */
294
if (! cinfo->quantize_colors || ! cinfo->buffered_image) {
295
cinfo->enable_1pass_quant = FALSE;
296
cinfo->enable_external_quant = FALSE;
297
cinfo->enable_2pass_quant = FALSE;
299
if (cinfo->quantize_colors) {
300
if (cinfo->raw_data_out)
301
ERREXIT(cinfo, JERR_NOTIMPL);
302
/* 2-pass quantizer only works in 3-component color space. */
303
if (cinfo->out_color_components != 3) {
304
cinfo->enable_1pass_quant = TRUE;
305
cinfo->enable_external_quant = FALSE;
306
cinfo->enable_2pass_quant = FALSE;
307
cinfo->colormap = NULL;
308
} else if (cinfo->colormap != NULL) {
309
cinfo->enable_external_quant = TRUE;
310
} else if (cinfo->two_pass_quantize) {
311
cinfo->enable_2pass_quant = TRUE;
313
cinfo->enable_1pass_quant = TRUE;
316
if (cinfo->enable_1pass_quant) {
317
#ifdef QUANT_1PASS_SUPPORTED
318
jinit_1pass_quantizer(cinfo);
319
master->quantizer_1pass = cinfo->cquantize;
321
ERREXIT(cinfo, JERR_NOT_COMPILED);
325
/* We use the 2-pass code to map to external colormaps. */
326
if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
327
#ifdef QUANT_2PASS_SUPPORTED
328
jinit_2pass_quantizer(cinfo);
329
master->quantizer_2pass = cinfo->cquantize;
331
ERREXIT(cinfo, JERR_NOT_COMPILED);
334
/* If both quantizers are initialized, the 2-pass one is left active;
335
* this is necessary for starting with quantization to an external map.
339
/* Post-processing: in particular, color conversion first */
340
if (! cinfo->raw_data_out) {
341
if (master->using_merged_upsample) {
342
#ifdef UPSAMPLE_MERGING_SUPPORTED
343
jinit_merged_upsampler(cinfo); /* does color conversion too */
345
ERREXIT(cinfo, JERR_NOT_COMPILED);
348
jinit_color_deconverter(cinfo);
349
jinit_upsampler(cinfo);
351
jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
354
jinit_inverse_dct(cinfo);
355
/* Entropy decoding: either Huffman or arithmetic coding. */
356
if (cinfo->arith_code)
357
jinit_arith_decoder(cinfo);
359
jinit_huff_decoder(cinfo);
362
/* Initialize principal buffer controllers. */
363
use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image;
364
jinit_d_coef_controller(cinfo, use_c_buffer);
366
if (! cinfo->raw_data_out)
367
jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
369
/* We can now tell the memory manager to allocate virtual arrays. */
370
(*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
372
/* Initialize input side of decompressor to consume first scan. */
373
(*cinfo->inputctl->start_input_pass) (cinfo);
375
#ifdef D_MULTISCAN_FILES_SUPPORTED
376
/* If jpeg_start_decompress will read the whole file, initialize
377
* progress monitoring appropriately. The input step is counted
380
if (cinfo->progress != NULL && ! cinfo->buffered_image &&
381
cinfo->inputctl->has_multiple_scans) {
383
/* Estimate number of scans to set pass_limit. */
384
if (cinfo->progressive_mode) {
385
/* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
386
nscans = 2 + 3 * cinfo->num_components;
388
/* For a nonprogressive multiscan file, estimate 1 scan per component. */
389
nscans = cinfo->num_components;
391
cinfo->progress->pass_counter = 0L;
392
cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
393
cinfo->progress->completed_passes = 0;
394
cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
395
/* Count the input pass as done */
396
master->pass_number++;
398
#endif /* D_MULTISCAN_FILES_SUPPORTED */
404
* This is called at the beginning of each output pass. We determine which
405
* modules will be active during this pass and give them appropriate
406
* start_pass calls. We also set is_dummy_pass to indicate whether this
407
* is a "real" output pass or a dummy pass for color quantization.
408
* (In the latter case, jdapistd.c will crank the pass to completion.)
412
prepare_for_output_pass (j_decompress_ptr cinfo)
414
my_master_ptr master = (my_master_ptr) cinfo->master;
416
if (master->pub.is_dummy_pass) {
417
#ifdef QUANT_2PASS_SUPPORTED
418
/* Final pass of 2-pass quantization */
419
master->pub.is_dummy_pass = FALSE;
420
(*cinfo->cquantize->start_pass) (cinfo, FALSE);
421
(*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
422
(*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
424
ERREXIT(cinfo, JERR_NOT_COMPILED);
425
#endif /* QUANT_2PASS_SUPPORTED */
427
if (cinfo->quantize_colors && cinfo->colormap == NULL) {
428
/* Select new quantization method */
429
if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
430
cinfo->cquantize = master->quantizer_2pass;
431
master->pub.is_dummy_pass = TRUE;
432
} else if (cinfo->enable_1pass_quant) {
433
cinfo->cquantize = master->quantizer_1pass;
435
ERREXIT(cinfo, JERR_MODE_CHANGE);
438
(*cinfo->idct->start_pass) (cinfo);
439
(*cinfo->coef->start_output_pass) (cinfo);
440
if (! cinfo->raw_data_out) {
441
if (! master->using_merged_upsample)
442
(*cinfo->cconvert->start_pass) (cinfo);
443
(*cinfo->upsample->start_pass) (cinfo);
444
if (cinfo->quantize_colors)
445
(*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
446
(*cinfo->post->start_pass) (cinfo,
447
(master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
448
(*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
452
/* Set up progress monitor's pass info if present */
453
if (cinfo->progress != NULL) {
454
cinfo->progress->completed_passes = master->pass_number;
455
cinfo->progress->total_passes = master->pass_number +
456
(master->pub.is_dummy_pass ? 2 : 1);
457
/* In buffered-image mode, we assume one more output pass if EOI not
458
* yet reached, but no more passes if EOI has been reached.
460
if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) {
461
cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
468
* Finish up at end of an output pass.
472
finish_output_pass (j_decompress_ptr cinfo)
474
my_master_ptr master = (my_master_ptr) cinfo->master;
476
if (cinfo->quantize_colors)
477
(*cinfo->cquantize->finish_pass) (cinfo);
478
master->pass_number++;
482
#ifdef D_MULTISCAN_FILES_SUPPORTED
485
* Switch to a new external colormap between output passes.
489
jpeg_new_colormap (j_decompress_ptr cinfo)
491
my_master_ptr master = (my_master_ptr) cinfo->master;
493
/* Prevent application from calling me at wrong times */
494
if (cinfo->global_state != DSTATE_BUFIMAGE)
495
ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
497
if (cinfo->quantize_colors && cinfo->enable_external_quant &&
498
cinfo->colormap != NULL) {
499
/* Select 2-pass quantizer for external colormap use */
500
cinfo->cquantize = master->quantizer_2pass;
501
/* Notify quantizer of colormap change */
502
(*cinfo->cquantize->new_color_map) (cinfo);
503
master->pub.is_dummy_pass = FALSE; /* just in case */
505
ERREXIT(cinfo, JERR_MODE_CHANGE);
508
#endif /* D_MULTISCAN_FILES_SUPPORTED */
512
* Initialize master decompression control and select active modules.
513
* This is performed at the start of jpeg_start_decompress.
517
jinit_master_decompress (j_decompress_ptr cinfo)
519
my_master_ptr master;
521
master = (my_master_ptr)
522
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
523
SIZEOF(my_decomp_master));
524
cinfo->master = (struct jpeg_decomp_master *) master;
525
master->pub.prepare_for_output_pass = prepare_for_output_pass;
526
master->pub.finish_output_pass = finish_output_pass;
528
master->pub.is_dummy_pass = FALSE;
530
master_selection(cinfo);