1/*
2 * jdmaster.c
3 *
4 * Copyright (C) 1991-1997, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains master control logic for the JPEG decompressor.
9 * These routines are concerned with selecting the modules to be executed
10 * and with determining the number of passes and the work to be done in each
11 * pass.
12 */
13
14#define JPEG_INTERNALS
15#include "jinclude.h"
16#include "jpeglib.h"
17
18
19/* Private state */
20
21typedef struct {
22 struct jpeg_decomp_master pub; /* public fields */
23
24 int pass_number; /* # of passes completed */
25
26 boolean using_merged_upsample; /* TRUE if using merged upsample/cconvert */
27
28 /* Saved references to initialized quantizer modules,
29 * in case we need to switch modes.
30 */
31 struct jpeg_color_quantizer * quantizer_1pass;
32 struct jpeg_color_quantizer * quantizer_2pass;
33} my_decomp_master;
34
35typedef my_decomp_master * my_master_ptr;
36
37
38/*
39 * Determine whether merged upsample/color conversion should be used.
40 * CRUCIAL: this must match the actual capabilities of jdmerge.c!
41 */
42
43LOCAL(boolean)
44use_merged_upsample (j_decompress_ptr cinfo)
45{
46#ifdef UPSAMPLE_MERGING_SUPPORTED
47 /* Merging is the equivalent of plain box-filter upsampling */
48 if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
49 return FALSE;
50 /* jdmerge.c only supports YCC=>RGB color conversion */
51 if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 ||
52 cinfo->out_color_space != JCS_RGB ||
53 cinfo->out_color_components != RGB_PIXELSIZE)
54 return FALSE;
55 /* and it only handles 2h1v or 2h2v sampling ratios */
56 if (cinfo->comp_info[0].h_samp_factor != 2 ||
57 cinfo->comp_info[1].h_samp_factor != 1 ||
58 cinfo->comp_info[2].h_samp_factor != 1 ||
59 cinfo->comp_info[0].v_samp_factor > 2 ||
60 cinfo->comp_info[1].v_samp_factor != 1 ||
61 cinfo->comp_info[2].v_samp_factor != 1)
62 return FALSE;
63 /* furthermore, it doesn't work if we've scaled the IDCTs differently */
64 if (cinfo->comp_info[0].DCT_scaled_size != cinfo->min_DCT_scaled_size ||
65 cinfo->comp_info[1].DCT_scaled_size != cinfo->min_DCT_scaled_size ||
66 cinfo->comp_info[2].DCT_scaled_size != cinfo->min_DCT_scaled_size)
67 return FALSE;
68 /* ??? also need to test for upsample-time rescaling, when & if supported */
69 return TRUE; /* by golly, it'll work... */
70#else
71 return FALSE;
72#endif
73}
74
75
76/*
77 * Compute output image dimensions and related values.
78 * NOTE: this is exported for possible use by application.
79 * Hence it mustn't do anything that can't be done twice.
80 * Also note that it may be called before the master module is initialized!
81 */
82
83GLOBAL(void)
84jpeg_calc_output_dimensions (j_decompress_ptr cinfo)
85/* Do computations that are needed before master selection phase */
86{
87#ifdef IDCT_SCALING_SUPPORTED
88 int ci;
89 jpeg_component_info *compptr;
90#endif
91
92 /* Prevent application from calling me at wrong times */
93 if (cinfo->global_state != DSTATE_READY)
94 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
95
96#ifdef IDCT_SCALING_SUPPORTED
97
98 /* Compute actual output image dimensions and DCT scaling choices. */
99 if (cinfo->scale_num * 8 <= cinfo->scale_denom) {
100 /* Provide 1/8 scaling */
101 cinfo->output_width = (JDIMENSION)
102 jdiv_round_up((long) cinfo->image_width, 8L);
103 cinfo->output_height = (JDIMENSION)
104 jdiv_round_up((long) cinfo->image_height, 8L);
105 cinfo->min_DCT_scaled_size = 1;
106 } else if (cinfo->scale_num * 4 <= cinfo->scale_denom) {
107 /* Provide 1/4 scaling */
108 cinfo->output_width = (JDIMENSION)
109 jdiv_round_up((long) cinfo->image_width, 4L);
110 cinfo->output_height = (JDIMENSION)
111 jdiv_round_up((long) cinfo->image_height, 4L);
112 cinfo->min_DCT_scaled_size = 2;
113 } else if (cinfo->scale_num * 2 <= cinfo->scale_denom) {
114 /* Provide 1/2 scaling */
115 cinfo->output_width = (JDIMENSION)
116 jdiv_round_up((long) cinfo->image_width, 2L);
117 cinfo->output_height = (JDIMENSION)
118 jdiv_round_up((long) cinfo->image_height, 2L);
119 cinfo->min_DCT_scaled_size = 4;
120 } else {
121 /* Provide 1/1 scaling */
122 cinfo->output_width = cinfo->image_width;
123 cinfo->output_height = cinfo->image_height;
124 cinfo->min_DCT_scaled_size = DCTSIZE;
125 }
126 /* In selecting the actual DCT scaling for each component, we try to
127 * scale up the chroma components via IDCT scaling rather than upsampling.
128 * This saves time if the upsampler gets to use 1:1 scaling.
129 * Note this code assumes that the supported DCT scalings are powers of 2.
130 */
131 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
132 ci++, compptr++) {
133 int ssize = cinfo->min_DCT_scaled_size;
134 while (ssize < DCTSIZE &&
135 (compptr->h_samp_factor * ssize * 2 <=
136 cinfo->max_h_samp_factor * cinfo->min_DCT_scaled_size) &&
137 (compptr->v_samp_factor * ssize * 2 <=
138 cinfo->max_v_samp_factor * cinfo->min_DCT_scaled_size)) {
139 ssize = ssize * 2;
140 }
141 compptr->DCT_scaled_size = ssize;
142 }
143
144 /* Recompute downsampled dimensions of components;
145 * application needs to know these if using raw downsampled data.
146 */
147 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
148 ci++, compptr++) {
149 /* Size in samples, after IDCT scaling */
150 compptr->downsampled_width = (JDIMENSION)
151 jdiv_round_up((long) cinfo->image_width *
152 (long) (compptr->h_samp_factor * compptr->DCT_scaled_size),
153 (long) (cinfo->max_h_samp_factor * DCTSIZE));
154 compptr->downsampled_height = (JDIMENSION)
155 jdiv_round_up((long) cinfo->image_height *
156 (long) (compptr->v_samp_factor * compptr->DCT_scaled_size),
157 (long) (cinfo->max_v_samp_factor * DCTSIZE));
158 }
159
160#else /* !IDCT_SCALING_SUPPORTED */
161
162 /* Hardwire it to "no scaling" */
163 cinfo->output_width = cinfo->image_width;
164 cinfo->output_height = cinfo->image_height;
165 /* jdinput.c has already initialized DCT_scaled_size to DCTSIZE,
166 * and has computed unscaled downsampled_width and downsampled_height.
167 */
168
169#endif /* IDCT_SCALING_SUPPORTED */
170
171 /* Report number of components in selected colorspace. */
172 /* Probably this should be in the color conversion module... */
173 switch (cinfo->out_color_space) {
174 case JCS_GRAYSCALE:
175 cinfo->out_color_components = 1;
176 break;
177 case JCS_RGB:
178#if RGB_PIXELSIZE != 3
179 cinfo->out_color_components = RGB_PIXELSIZE;
180 break;
181#endif /* else share code with YCbCr */
182 case JCS_YCbCr:
183 cinfo->out_color_components = 3;
184 break;
185 case JCS_CMYK:
186 case JCS_YCCK:
187 cinfo->out_color_components = 4;
188 break;
189 default: /* else must be same colorspace as in file */
190 cinfo->out_color_components = cinfo->num_components;
191 break;
192 }
193 cinfo->output_components = (cinfo->quantize_colors ? 1 :
194 cinfo->out_color_components);
195
196 /* See if upsampler will want to emit more than one row at a time */
197 if (use_merged_upsample(cinfo))
198 cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
199 else
200 cinfo->rec_outbuf_height = 1;
201}
202
203
204/*
205 * Several decompression processes need to range-limit values to the range
206 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
207 * due to noise introduced by quantization, roundoff error, etc. These
208 * processes are inner loops and need to be as fast as possible. On most
209 * machines, particularly CPUs with pipelines or instruction prefetch,
210 * a (subscript-check-less) C table lookup
211 * x = sample_range_limit[x];
212 * is faster than explicit tests
213 * if (x < 0) x = 0;
214 * else if (x > MAXJSAMPLE) x = MAXJSAMPLE;
215 * These processes all use a common table prepared by the routine below.
216 *
217 * For most steps we can mathematically guarantee that the initial value
218 * of x is within MAXJSAMPLE+1 of the legal range, so a table running from
219 * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial
220 * limiting step (just after the IDCT), a wildly out-of-range value is
221 * possible if the input data is corrupt. To avoid any chance of indexing
222 * off the end of memory and getting a bad-pointer trap, we perform the
223 * post-IDCT limiting thus:
224 * x = range_limit[x & MASK];
225 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
226 * samples. Under normal circumstances this is more than enough range and
227 * a correct output will be generated; with bogus input data the mask will
228 * cause wraparound, and we will safely generate a bogus-but-in-range output.
229 * For the post-IDCT step, we want to convert the data from signed to unsigned
230 * representation by adding CENTERJSAMPLE at the same time that we limit it.
231 * So the post-IDCT limiting table ends up looking like this:
232 * CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
233 * MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
234 * 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
235 * 0,1,...,CENTERJSAMPLE-1
236 * Negative inputs select values from the upper half of the table after
237 * masking.
238 *
239 * We can save some space by overlapping the start of the post-IDCT table
240 * with the simpler range limiting table. The post-IDCT table begins at
241 * sample_range_limit + CENTERJSAMPLE.
242 *
243 * Note that the table is allocated in near data space on PCs; it's small
244 * enough and used often enough to justify this.
245 */
246
247LOCAL(void)
248prepare_range_limit_table (j_decompress_ptr cinfo)
249/* Allocate and fill in the sample_range_limit table */
250{
251 JSAMPLE * table;
252 int i;
253
254 table = (JSAMPLE *)
255 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
256 (5 * (MAXJSAMPLE+1) + CENTERJSAMPLE) * SIZEOF(JSAMPLE));
257 table += (MAXJSAMPLE+1); /* allow negative subscripts of simple table */
258 cinfo->sample_range_limit = table;
259 /* First segment of "simple" table: limit[x] = 0 for x < 0 */
260 MEMZERO(table - (MAXJSAMPLE+1), (MAXJSAMPLE+1) * SIZEOF(JSAMPLE));
261 /* Main part of "simple" table: limit[x] = x */
262 for (i = 0; i <= MAXJSAMPLE; i++)
263 table[i] = (JSAMPLE) i;
264 table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */
265 /* End of simple table, rest of first half of post-IDCT table */
266 for (i = CENTERJSAMPLE; i < 2*(MAXJSAMPLE+1); i++)
267 table[i] = MAXJSAMPLE;
268 /* Second half of post-IDCT table */
269 MEMZERO(table + (2 * (MAXJSAMPLE+1)),
270 (2 * (MAXJSAMPLE+1) - CENTERJSAMPLE) * SIZEOF(JSAMPLE));
271 MEMCOPY(table + (4 * (MAXJSAMPLE+1) - CENTERJSAMPLE),
272 cinfo->sample_range_limit, CENTERJSAMPLE * SIZEOF(JSAMPLE));
273}
274
275
276/*
277 * Master selection of decompression modules.
278 * This is done once at jpeg_start_decompress time. We determine
279 * which modules will be used and give them appropriate initialization calls.
280 * We also initialize the decompressor input side to begin consuming data.
281 *
282 * Since jpeg_read_header has finished, we know what is in the SOF
283 * and (first) SOS markers. We also have all the application parameter
284 * settings.
285 */
286
287LOCAL(void)
288master_selection (j_decompress_ptr cinfo)
289{
290 my_master_ptr master = (my_master_ptr) cinfo->master;
291 boolean use_c_buffer;
292 long samplesperrow;
293 JDIMENSION jd_samplesperrow;
294
295 /* Initialize dimensions and other stuff */
296 jpeg_calc_output_dimensions(cinfo);
297 prepare_range_limit_table(cinfo);
298
299 /* Width of an output scanline must be representable as JDIMENSION. */
300 samplesperrow = (long) cinfo->output_width * (long) cinfo->out_color_components;
301 jd_samplesperrow = (JDIMENSION) samplesperrow;
302 if ((long) jd_samplesperrow != samplesperrow)
303 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
304
305 /* Initialize my private state */
306 master->pass_number = 0;
307 master->using_merged_upsample = use_merged_upsample(cinfo);
308
309 /* Color quantizer selection */
310 master->quantizer_1pass = NULL;
311 master->quantizer_2pass = NULL;
312 /* No mode changes if not using buffered-image mode. */
313 if (! cinfo->quantize_colors || ! cinfo->buffered_image) {
314 cinfo->enable_1pass_quant = FALSE;
315 cinfo->enable_external_quant = FALSE;
316 cinfo->enable_2pass_quant = FALSE;
317 }
318 if (cinfo->quantize_colors) {
319 if (cinfo->raw_data_out)
320 ERREXIT(cinfo, JERR_NOTIMPL);
321 /* 2-pass quantizer only works in 3-component color space. */
322 if (cinfo->out_color_components != 3) {
323 cinfo->enable_1pass_quant = TRUE;
324 cinfo->enable_external_quant = FALSE;
325 cinfo->enable_2pass_quant = FALSE;
326 cinfo->colormap = NULL;
327 } else if (cinfo->colormap != NULL) {
328 cinfo->enable_external_quant = TRUE;
329 } else if (cinfo->two_pass_quantize) {
330 cinfo->enable_2pass_quant = TRUE;
331 } else {
332 cinfo->enable_1pass_quant = TRUE;
333 }
334
335 if (cinfo->enable_1pass_quant) {
336#ifdef QUANT_1PASS_SUPPORTED
337 jinit_1pass_quantizer(cinfo);
338 master->quantizer_1pass = cinfo->cquantize;
339#else
340 ERREXIT(cinfo, JERR_NOT_COMPILED);
341#endif
342 }
343
344 /* We use the 2-pass code to map to external colormaps. */
345 if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
346#ifdef QUANT_2PASS_SUPPORTED
347 jinit_2pass_quantizer(cinfo);
348 master->quantizer_2pass = cinfo->cquantize;
349#else
350 ERREXIT(cinfo, JERR_NOT_COMPILED);
351#endif
352 }
353 /* If both quantizers are initialized, the 2-pass one is left active;
354 * this is necessary for starting with quantization to an external map.
355 */
356 }
357
358 /* Post-processing: in particular, color conversion first */
359 if (! cinfo->raw_data_out) {
360 if (master->using_merged_upsample) {
361#ifdef UPSAMPLE_MERGING_SUPPORTED
362 jinit_merged_upsampler(cinfo); /* does color conversion too */
363#else
364 ERREXIT(cinfo, JERR_NOT_COMPILED);
365#endif
366 } else {
367 jinit_color_deconverter(cinfo);
368 jinit_upsampler(cinfo);
369 }
370 jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
371 }
372 /* Inverse DCT */
373 jinit_inverse_dct(cinfo);
374 /* Entropy decoding: either Huffman or arithmetic coding. */
375 if (cinfo->arith_code) {
376 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
377 } else {
378 if (cinfo->progressive_mode) {
379#ifdef D_PROGRESSIVE_SUPPORTED
380 jinit_phuff_decoder(cinfo);
381#else
382 ERREXIT(cinfo, JERR_NOT_COMPILED);
383#endif
384 } else
385 jinit_huff_decoder(cinfo);
386 }
387
388 /* Initialize principal buffer controllers. */
389 use_c_buffer = cinfo->inputctl->has_multiple_scans || cinfo->buffered_image;
390 jinit_d_coef_controller(cinfo, use_c_buffer);
391
392 if (! cinfo->raw_data_out)
393 jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
394
395 /* We can now tell the memory manager to allocate virtual arrays. */
396 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
397
398 /* Initialize input side of decompressor to consume first scan. */
399 (*cinfo->inputctl->start_input_pass) (cinfo);
400
401#ifdef D_MULTISCAN_FILES_SUPPORTED
402 /* If jpeg_start_decompress will read the whole file, initialize
403 * progress monitoring appropriately. The input step is counted
404 * as one pass.
405 */
406 if (cinfo->progress != NULL && ! cinfo->buffered_image &&
407 cinfo->inputctl->has_multiple_scans) {
408 int nscans;
409 /* Estimate number of scans to set pass_limit. */
410 if (cinfo->progressive_mode) {
411 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
412 nscans = 2 + 3 * cinfo->num_components;
413 } else {
414 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
415 nscans = cinfo->num_components;
416 }
417 cinfo->progress->pass_counter = 0L;
418 cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
419 cinfo->progress->completed_passes = 0;
420 cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
421 /* Count the input pass as done */
422 master->pass_number++;
423 }
424#endif /* D_MULTISCAN_FILES_SUPPORTED */
425}
426
427
428/*
429 * Per-pass setup.
430 * This is called at the beginning of each output pass. We determine which
431 * modules will be active during this pass and give them appropriate
432 * start_pass calls. We also set is_dummy_pass to indicate whether this
433 * is a "real" output pass or a dummy pass for color quantization.
434 * (In the latter case, jdapistd.c will crank the pass to completion.)
435 */
436
437METHODDEF(void)
438prepare_for_output_pass (j_decompress_ptr cinfo)
439{
440 my_master_ptr master = (my_master_ptr) cinfo->master;
441
442 if (master->pub.is_dummy_pass) {
443#ifdef QUANT_2PASS_SUPPORTED
444 /* Final pass of 2-pass quantization */
445 master->pub.is_dummy_pass = FALSE;
446 (*cinfo->cquantize->start_pass) (cinfo, FALSE);
447 (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
448 (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
449#else
450 ERREXIT(cinfo, JERR_NOT_COMPILED);
451#endif /* QUANT_2PASS_SUPPORTED */
452 } else {
453 if (cinfo->quantize_colors && cinfo->colormap == NULL) {
454 /* Select new quantization method */
455 if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
456 cinfo->cquantize = master->quantizer_2pass;
457 master->pub.is_dummy_pass = TRUE;
458 } else if (cinfo->enable_1pass_quant) {
459 cinfo->cquantize = master->quantizer_1pass;
460 } else {
461 ERREXIT(cinfo, JERR_MODE_CHANGE);
462 }
463 }
464 (*cinfo->idct->start_pass) (cinfo);
465 (*cinfo->coef->start_output_pass) (cinfo);
466 if (! cinfo->raw_data_out) {
467 if (! master->using_merged_upsample)
468 (*cinfo->cconvert->start_pass) (cinfo);
469 (*cinfo->upsample->start_pass) (cinfo);
470 if (cinfo->quantize_colors)
471 (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
472 (*cinfo->post->start_pass) (cinfo,
473 (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
474 (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
475 }
476 }
477
478 /* Set up progress monitor's pass info if present */
479 if (cinfo->progress != NULL) {
480 cinfo->progress->completed_passes = master->pass_number;
481 cinfo->progress->total_passes = master->pass_number +
482 (master->pub.is_dummy_pass ? 2 : 1);
483 /* In buffered-image mode, we assume one more output pass if EOI not
484 * yet reached, but no more passes if EOI has been reached.
485 */
486 if (cinfo->buffered_image && ! cinfo->inputctl->eoi_reached) {
487 cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
488 }
489 }
490}
491
492
493/*
494 * Finish up at end of an output pass.
495 */
496
497METHODDEF(void)
498finish_output_pass (j_decompress_ptr cinfo)
499{
500 my_master_ptr master = (my_master_ptr) cinfo->master;
501
502 if (cinfo->quantize_colors)
503 (*cinfo->cquantize->finish_pass) (cinfo);
504 master->pass_number++;
505}
506
507
508#ifdef D_MULTISCAN_FILES_SUPPORTED
509
510/*
511 * Switch to a new external colormap between output passes.
512 */
513
514GLOBAL(void)
515jpeg_new_colormap (j_decompress_ptr cinfo)
516{
517 my_master_ptr master = (my_master_ptr) cinfo->master;
518
519 /* Prevent application from calling me at wrong times */
520 if (cinfo->global_state != DSTATE_BUFIMAGE)
521 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
522
523 if (cinfo->quantize_colors && cinfo->enable_external_quant &&
524 cinfo->colormap != NULL) {
525 /* Select 2-pass quantizer for external colormap use */
526 cinfo->cquantize = master->quantizer_2pass;
527 /* Notify quantizer of colormap change */
528 (*cinfo->cquantize->new_color_map) (cinfo);
529 master->pub.is_dummy_pass = FALSE; /* just in case */
530 } else
531 ERREXIT(cinfo, JERR_MODE_CHANGE);
532}
533
534#endif /* D_MULTISCAN_FILES_SUPPORTED */
535
536
537/*
538 * Initialize master decompression control and select active modules.
539 * This is performed at the start of jpeg_start_decompress.
540 */
541
542GLOBAL(void)
543jinit_master_decompress (j_decompress_ptr cinfo)
544{
545 my_master_ptr master;
546
547 master = (my_master_ptr)
548 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
549 SIZEOF(my_decomp_master));
550 cinfo->master = (struct jpeg_decomp_master *) master;
551 master->pub.prepare_for_output_pass = prepare_for_output_pass;
552 master->pub.finish_output_pass = finish_output_pass;
553
554 master->pub.is_dummy_pass = FALSE;
555
556 master_selection(cinfo);
557}
558