4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1991-1997, Thomas G. Lane.
6 * Modified 2002-2009 by Guido Vollbeding.
7 * Lossless JPEG Modifications:
8 * Copyright (C) 1999, Ken Murchison.
9 * libjpeg-turbo Modifications:
10 * Copyright (C) 2009-2011, 2016, 2019, 2022-2023, D. R. Commander.
11 * Copyright (C) 2013, Linaro Limited.
12 * Copyright (C) 2015, Google, Inc.
13 * For conditions of distribution and use, see the accompanying README.ijg
16 * This file contains master control logic for the JPEG decompressor.
17 * These routines are concerned with selecting the modules to be executed
18 * and with determining the number of passes and the work to be done in each
22 #define JPEG_INTERNALS
25 #include "jpegapicomp.h"
30 * Determine whether merged upsample/color conversion should be used.
31 * CRUCIAL: this must match the actual capabilities of jdmerge.c!
35 use_merged_upsample(j_decompress_ptr cinfo)
37 #ifdef UPSAMPLE_MERGING_SUPPORTED
38 /* Colorspace conversion is not supported with lossless JPEG images */
39 if (cinfo->master->lossless)
41 /* Merging is the equivalent of plain box-filter upsampling */
42 if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
44 /* jdmerge.c only supports YCC=>RGB and YCC=>RGB565 color conversion */
45 if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 ||
46 (cinfo->out_color_space != JCS_RGB &&
47 cinfo->out_color_space != JCS_RGB565 &&
48 cinfo->out_color_space != JCS_EXT_RGB &&
49 cinfo->out_color_space != JCS_EXT_RGBX &&
50 cinfo->out_color_space != JCS_EXT_BGR &&
51 cinfo->out_color_space != JCS_EXT_BGRX &&
52 cinfo->out_color_space != JCS_EXT_XBGR &&
53 cinfo->out_color_space != JCS_EXT_XRGB &&
54 cinfo->out_color_space != JCS_EXT_RGBA &&
55 cinfo->out_color_space != JCS_EXT_BGRA &&
56 cinfo->out_color_space != JCS_EXT_ABGR &&
57 cinfo->out_color_space != JCS_EXT_ARGB))
59 if ((cinfo->out_color_space == JCS_RGB565 &&
60 cinfo->out_color_components != 3) ||
61 (cinfo->out_color_space != JCS_RGB565 &&
62 cinfo->out_color_components != rgb_pixelsize[cinfo->out_color_space]))
64 /* and it only handles 2h1v or 2h2v sampling ratios */
65 if (cinfo->comp_info[0].h_samp_factor != 2 ||
66 cinfo->comp_info[1].h_samp_factor != 1 ||
67 cinfo->comp_info[2].h_samp_factor != 1 ||
68 cinfo->comp_info[0].v_samp_factor > 2 ||
69 cinfo->comp_info[1].v_samp_factor != 1 ||
70 cinfo->comp_info[2].v_samp_factor != 1)
72 /* furthermore, it doesn't work if we've scaled the IDCTs differently */
73 if (cinfo->comp_info[0]._DCT_scaled_size != cinfo->_min_DCT_scaled_size ||
74 cinfo->comp_info[1]._DCT_scaled_size != cinfo->_min_DCT_scaled_size ||
75 cinfo->comp_info[2]._DCT_scaled_size != cinfo->_min_DCT_scaled_size)
77 /* ??? also need to test for upsample-time rescaling, when & if supported */
78 return TRUE; /* by golly, it'll work... */
86 * Compute output image dimensions and related values.
87 * NOTE: this is exported for possible use by application.
88 * Hence it mustn't do anything that can't be done twice.
91 #if JPEG_LIB_VERSION >= 80
96 jpeg_core_output_dimensions(j_decompress_ptr cinfo)
97 /* Do computations that are needed before master selection phase.
98 * This function is used for transcoding and full decompression.
101 #ifdef IDCT_SCALING_SUPPORTED
103 jpeg_component_info *compptr;
105 if (!cinfo->master->lossless) {
106 /* Compute actual output image dimensions and DCT scaling choices. */
107 if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom) {
108 /* Provide 1/block_size scaling */
109 cinfo->output_width = (JDIMENSION)
110 jdiv_round_up((long)cinfo->image_width, (long)DCTSIZE);
111 cinfo->output_height = (JDIMENSION)
112 jdiv_round_up((long)cinfo->image_height, (long)DCTSIZE);
113 cinfo->_min_DCT_h_scaled_size = 1;
114 cinfo->_min_DCT_v_scaled_size = 1;
115 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 2) {
116 /* Provide 2/block_size scaling */
117 cinfo->output_width = (JDIMENSION)
118 jdiv_round_up((long)cinfo->image_width * 2L, (long)DCTSIZE);
119 cinfo->output_height = (JDIMENSION)
120 jdiv_round_up((long)cinfo->image_height * 2L, (long)DCTSIZE);
121 cinfo->_min_DCT_h_scaled_size = 2;
122 cinfo->_min_DCT_v_scaled_size = 2;
123 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 3) {
124 /* Provide 3/block_size scaling */
125 cinfo->output_width = (JDIMENSION)
126 jdiv_round_up((long)cinfo->image_width * 3L, (long)DCTSIZE);
127 cinfo->output_height = (JDIMENSION)
128 jdiv_round_up((long)cinfo->image_height * 3L, (long)DCTSIZE);
129 cinfo->_min_DCT_h_scaled_size = 3;
130 cinfo->_min_DCT_v_scaled_size = 3;
131 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 4) {
132 /* Provide 4/block_size scaling */
133 cinfo->output_width = (JDIMENSION)
134 jdiv_round_up((long)cinfo->image_width * 4L, (long)DCTSIZE);
135 cinfo->output_height = (JDIMENSION)
136 jdiv_round_up((long)cinfo->image_height * 4L, (long)DCTSIZE);
137 cinfo->_min_DCT_h_scaled_size = 4;
138 cinfo->_min_DCT_v_scaled_size = 4;
139 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 5) {
140 /* Provide 5/block_size scaling */
141 cinfo->output_width = (JDIMENSION)
142 jdiv_round_up((long)cinfo->image_width * 5L, (long)DCTSIZE);
143 cinfo->output_height = (JDIMENSION)
144 jdiv_round_up((long)cinfo->image_height * 5L, (long)DCTSIZE);
145 cinfo->_min_DCT_h_scaled_size = 5;
146 cinfo->_min_DCT_v_scaled_size = 5;
147 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 6) {
148 /* Provide 6/block_size scaling */
149 cinfo->output_width = (JDIMENSION)
150 jdiv_round_up((long)cinfo->image_width * 6L, (long)DCTSIZE);
151 cinfo->output_height = (JDIMENSION)
152 jdiv_round_up((long)cinfo->image_height * 6L, (long)DCTSIZE);
153 cinfo->_min_DCT_h_scaled_size = 6;
154 cinfo->_min_DCT_v_scaled_size = 6;
155 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 7) {
156 /* Provide 7/block_size scaling */
157 cinfo->output_width = (JDIMENSION)
158 jdiv_round_up((long)cinfo->image_width * 7L, (long)DCTSIZE);
159 cinfo->output_height = (JDIMENSION)
160 jdiv_round_up((long)cinfo->image_height * 7L, (long)DCTSIZE);
161 cinfo->_min_DCT_h_scaled_size = 7;
162 cinfo->_min_DCT_v_scaled_size = 7;
163 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 8) {
164 /* Provide 8/block_size scaling */
165 cinfo->output_width = (JDIMENSION)
166 jdiv_round_up((long)cinfo->image_width * 8L, (long)DCTSIZE);
167 cinfo->output_height = (JDIMENSION)
168 jdiv_round_up((long)cinfo->image_height * 8L, (long)DCTSIZE);
169 cinfo->_min_DCT_h_scaled_size = 8;
170 cinfo->_min_DCT_v_scaled_size = 8;
171 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 9) {
172 /* Provide 9/block_size scaling */
173 cinfo->output_width = (JDIMENSION)
174 jdiv_round_up((long)cinfo->image_width * 9L, (long)DCTSIZE);
175 cinfo->output_height = (JDIMENSION)
176 jdiv_round_up((long)cinfo->image_height * 9L, (long)DCTSIZE);
177 cinfo->_min_DCT_h_scaled_size = 9;
178 cinfo->_min_DCT_v_scaled_size = 9;
179 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 10) {
180 /* Provide 10/block_size scaling */
181 cinfo->output_width = (JDIMENSION)
182 jdiv_round_up((long)cinfo->image_width * 10L, (long)DCTSIZE);
183 cinfo->output_height = (JDIMENSION)
184 jdiv_round_up((long)cinfo->image_height * 10L, (long)DCTSIZE);
185 cinfo->_min_DCT_h_scaled_size = 10;
186 cinfo->_min_DCT_v_scaled_size = 10;
187 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 11) {
188 /* Provide 11/block_size scaling */
189 cinfo->output_width = (JDIMENSION)
190 jdiv_round_up((long)cinfo->image_width * 11L, (long)DCTSIZE);
191 cinfo->output_height = (JDIMENSION)
192 jdiv_round_up((long)cinfo->image_height * 11L, (long)DCTSIZE);
193 cinfo->_min_DCT_h_scaled_size = 11;
194 cinfo->_min_DCT_v_scaled_size = 11;
195 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 12) {
196 /* Provide 12/block_size scaling */
197 cinfo->output_width = (JDIMENSION)
198 jdiv_round_up((long)cinfo->image_width * 12L, (long)DCTSIZE);
199 cinfo->output_height = (JDIMENSION)
200 jdiv_round_up((long)cinfo->image_height * 12L, (long)DCTSIZE);
201 cinfo->_min_DCT_h_scaled_size = 12;
202 cinfo->_min_DCT_v_scaled_size = 12;
203 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 13) {
204 /* Provide 13/block_size scaling */
205 cinfo->output_width = (JDIMENSION)
206 jdiv_round_up((long)cinfo->image_width * 13L, (long)DCTSIZE);
207 cinfo->output_height = (JDIMENSION)
208 jdiv_round_up((long)cinfo->image_height * 13L, (long)DCTSIZE);
209 cinfo->_min_DCT_h_scaled_size = 13;
210 cinfo->_min_DCT_v_scaled_size = 13;
211 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 14) {
212 /* Provide 14/block_size scaling */
213 cinfo->output_width = (JDIMENSION)
214 jdiv_round_up((long)cinfo->image_width * 14L, (long)DCTSIZE);
215 cinfo->output_height = (JDIMENSION)
216 jdiv_round_up((long)cinfo->image_height * 14L, (long)DCTSIZE);
217 cinfo->_min_DCT_h_scaled_size = 14;
218 cinfo->_min_DCT_v_scaled_size = 14;
219 } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 15) {
220 /* Provide 15/block_size scaling */
221 cinfo->output_width = (JDIMENSION)
222 jdiv_round_up((long)cinfo->image_width * 15L, (long)DCTSIZE);
223 cinfo->output_height = (JDIMENSION)
224 jdiv_round_up((long)cinfo->image_height * 15L, (long)DCTSIZE);
225 cinfo->_min_DCT_h_scaled_size = 15;
226 cinfo->_min_DCT_v_scaled_size = 15;
228 /* Provide 16/block_size scaling */
229 cinfo->output_width = (JDIMENSION)
230 jdiv_round_up((long)cinfo->image_width * 16L, (long)DCTSIZE);
231 cinfo->output_height = (JDIMENSION)
232 jdiv_round_up((long)cinfo->image_height * 16L, (long)DCTSIZE);
233 cinfo->_min_DCT_h_scaled_size = 16;
234 cinfo->_min_DCT_v_scaled_size = 16;
237 /* Recompute dimensions of components */
238 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
240 compptr->_DCT_h_scaled_size = cinfo->_min_DCT_h_scaled_size;
241 compptr->_DCT_v_scaled_size = cinfo->_min_DCT_v_scaled_size;
244 #endif /* !IDCT_SCALING_SUPPORTED */
246 /* Hardwire it to "no scaling" */
247 cinfo->output_width = cinfo->image_width;
248 cinfo->output_height = cinfo->image_height;
249 /* jdinput.c has already initialized DCT_scaled_size,
250 * and has computed unscaled downsampled_width and downsampled_height.
257 * Compute output image dimensions and related values.
258 * NOTE: this is exported for possible use by application.
259 * Hence it mustn't do anything that can't be done twice.
260 * Also note that it may be called before the master module is initialized!
264 jpeg_calc_output_dimensions(j_decompress_ptr cinfo)
265 /* Do computations that are needed before master selection phase */
267 #ifdef IDCT_SCALING_SUPPORTED
269 jpeg_component_info *compptr;
272 /* Prevent application from calling me at wrong times */
273 if (cinfo->global_state != DSTATE_READY)
274 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
276 /* Compute core output image dimensions and DCT scaling choices. */
277 jpeg_core_output_dimensions(cinfo);
279 #ifdef IDCT_SCALING_SUPPORTED
281 if (!cinfo->master->lossless) {
282 /* In selecting the actual DCT scaling for each component, we try to
283 * scale up the chroma components via IDCT scaling rather than upsampling.
284 * This saves time if the upsampler gets to use 1:1 scaling.
285 * Note this code adapts subsampling ratios which are powers of 2.
287 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
289 int ssize = cinfo->_min_DCT_scaled_size;
290 while (ssize < DCTSIZE &&
291 ((cinfo->max_h_samp_factor * cinfo->_min_DCT_scaled_size) %
292 (compptr->h_samp_factor * ssize * 2) == 0) &&
293 ((cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size) %
294 (compptr->v_samp_factor * ssize * 2) == 0)) {
297 #if JPEG_LIB_VERSION >= 70
298 compptr->DCT_h_scaled_size = compptr->DCT_v_scaled_size = ssize;
300 compptr->DCT_scaled_size = ssize;
304 /* Recompute downsampled dimensions of components;
305 * application needs to know these if using raw downsampled data.
307 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
309 /* Size in samples, after IDCT scaling */
310 compptr->downsampled_width = (JDIMENSION)
311 jdiv_round_up((long)cinfo->image_width *
312 (long)(compptr->h_samp_factor *
313 compptr->_DCT_scaled_size),
314 (long)(cinfo->max_h_samp_factor * DCTSIZE));
315 compptr->downsampled_height = (JDIMENSION)
316 jdiv_round_up((long)cinfo->image_height *
317 (long)(compptr->v_samp_factor *
318 compptr->_DCT_scaled_size),
319 (long)(cinfo->max_v_samp_factor * DCTSIZE));
322 #endif /* IDCT_SCALING_SUPPORTED */
324 /* Hardwire it to "no scaling" */
325 cinfo->output_width = cinfo->image_width;
326 cinfo->output_height = cinfo->image_height;
327 /* jdinput.c has already initialized DCT_scaled_size to DCTSIZE,
328 * and has computed unscaled downsampled_width and downsampled_height.
332 /* Report number of components in selected colorspace. */
333 /* Probably this should be in the color conversion module... */
334 switch (cinfo->out_color_space) {
336 cinfo->out_color_components = 1;
349 cinfo->out_color_components = rgb_pixelsize[cinfo->out_color_space];
353 cinfo->out_color_components = 3;
357 cinfo->out_color_components = 4;
359 default: /* else must be same colorspace as in file */
360 cinfo->out_color_components = cinfo->num_components;
363 cinfo->output_components = (cinfo->quantize_colors ? 1 :
364 cinfo->out_color_components);
366 /* See if upsampler will want to emit more than one row at a time */
367 if (use_merged_upsample(cinfo))
368 cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
370 cinfo->rec_outbuf_height = 1;
375 * Several decompression processes need to range-limit values to the range
376 * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
377 * due to noise introduced by quantization, roundoff error, etc. These
378 * processes are inner loops and need to be as fast as possible. On most
379 * machines, particularly CPUs with pipelines or instruction prefetch,
380 * a (subscript-check-less) C table lookup
381 * x = sample_range_limit[x];
382 * is faster than explicit tests
384 * else if (x > MAXJSAMPLE) x = MAXJSAMPLE;
385 * These processes all use a common table prepared by the routine below.
387 * For most steps we can mathematically guarantee that the initial value
388 * of x is within MAXJSAMPLE+1 of the legal range, so a table running from
389 * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient. But for the initial
390 * limiting step (just after the IDCT), a wildly out-of-range value is
391 * possible if the input data is corrupt. To avoid any chance of indexing
392 * off the end of memory and getting a bad-pointer trap, we perform the
393 * post-IDCT limiting thus:
394 * x = range_limit[x & MASK];
395 * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
396 * samples. Under normal circumstances this is more than enough range and
397 * a correct output will be generated; with bogus input data the mask will
398 * cause wraparound, and we will safely generate a bogus-but-in-range output.
399 * For the post-IDCT step, we want to convert the data from signed to unsigned
400 * representation by adding CENTERJSAMPLE at the same time that we limit it.
401 * So the post-IDCT limiting table ends up looking like this:
402 * CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
403 * MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
404 * 0 (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
405 * 0,1,...,CENTERJSAMPLE-1
406 * Negative inputs select values from the upper half of the table after
409 * We can save some space by overlapping the start of the post-IDCT table
410 * with the simpler range limiting table. The post-IDCT table begins at
411 * sample_range_limit + CENTERJSAMPLE.
415 prepare_range_limit_table(j_decompress_ptr cinfo)
416 /* Allocate and fill in the sample_range_limit table */
420 #ifdef D_LOSSLESS_SUPPORTED
425 if (cinfo->data_precision == 16) {
426 #ifdef D_LOSSLESS_SUPPORTED
427 table16 = (J16SAMPLE *)
428 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
429 (5 * (MAXJ16SAMPLE + 1) + CENTERJ16SAMPLE) *
431 table16 += (MAXJ16SAMPLE + 1); /* allow negative subscripts of simple
433 cinfo->sample_range_limit = (JSAMPLE *)table16;
434 /* First segment of "simple" table: limit[x] = 0 for x < 0 */
435 memset(table16 - (MAXJ16SAMPLE + 1), 0,
436 (MAXJ16SAMPLE + 1) * sizeof(J16SAMPLE));
437 /* Main part of "simple" table: limit[x] = x */
438 for (i = 0; i <= MAXJ16SAMPLE; i++)
439 table16[i] = (J16SAMPLE)i;
440 table16 += CENTERJ16SAMPLE; /* Point to where post-IDCT table starts */
441 /* End of simple table, rest of first half of post-IDCT table */
442 for (i = CENTERJ16SAMPLE; i < 2 * (MAXJ16SAMPLE + 1); i++)
443 table16[i] = MAXJ16SAMPLE;
444 /* Second half of post-IDCT table */
445 memset(table16 + (2 * (MAXJ16SAMPLE + 1)), 0,
446 (2 * (MAXJ16SAMPLE + 1) - CENTERJ16SAMPLE) * sizeof(J16SAMPLE));
447 memcpy(table16 + (4 * (MAXJ16SAMPLE + 1) - CENTERJ16SAMPLE),
448 cinfo->sample_range_limit, CENTERJ16SAMPLE * sizeof(J16SAMPLE));
450 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
452 } else if (cinfo->data_precision == 12) {
453 table12 = (J12SAMPLE *)
454 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
455 (5 * (MAXJ12SAMPLE + 1) + CENTERJ12SAMPLE) *
457 table12 += (MAXJ12SAMPLE + 1); /* allow negative subscripts of simple
459 cinfo->sample_range_limit = (JSAMPLE *)table12;
460 /* First segment of "simple" table: limit[x] = 0 for x < 0 */
461 memset(table12 - (MAXJ12SAMPLE + 1), 0,
462 (MAXJ12SAMPLE + 1) * sizeof(J12SAMPLE));
463 /* Main part of "simple" table: limit[x] = x */
464 for (i = 0; i <= MAXJ12SAMPLE; i++)
465 table12[i] = (J12SAMPLE)i;
466 table12 += CENTERJ12SAMPLE; /* Point to where post-IDCT table starts */
467 /* End of simple table, rest of first half of post-IDCT table */
468 for (i = CENTERJ12SAMPLE; i < 2 * (MAXJ12SAMPLE + 1); i++)
469 table12[i] = MAXJ12SAMPLE;
470 /* Second half of post-IDCT table */
471 memset(table12 + (2 * (MAXJ12SAMPLE + 1)), 0,
472 (2 * (MAXJ12SAMPLE + 1) - CENTERJ12SAMPLE) * sizeof(J12SAMPLE));
473 memcpy(table12 + (4 * (MAXJ12SAMPLE + 1) - CENTERJ12SAMPLE),
474 cinfo->sample_range_limit, CENTERJ12SAMPLE * sizeof(J12SAMPLE));
477 (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
478 (5 * (MAXJSAMPLE + 1) + CENTERJSAMPLE) * sizeof(JSAMPLE));
479 table += (MAXJSAMPLE + 1); /* allow negative subscripts of simple table */
480 cinfo->sample_range_limit = table;
481 /* First segment of "simple" table: limit[x] = 0 for x < 0 */
482 memset(table - (MAXJSAMPLE + 1), 0, (MAXJSAMPLE + 1) * sizeof(JSAMPLE));
483 /* Main part of "simple" table: limit[x] = x */
484 for (i = 0; i <= MAXJSAMPLE; i++)
485 table[i] = (JSAMPLE)i;
486 table += CENTERJSAMPLE; /* Point to where post-IDCT table starts */
487 /* End of simple table, rest of first half of post-IDCT table */
488 for (i = CENTERJSAMPLE; i < 2 * (MAXJSAMPLE + 1); i++)
489 table[i] = MAXJSAMPLE;
490 /* Second half of post-IDCT table */
491 memset(table + (2 * (MAXJSAMPLE + 1)), 0,
492 (2 * (MAXJSAMPLE + 1) - CENTERJSAMPLE) * sizeof(JSAMPLE));
493 memcpy(table + (4 * (MAXJSAMPLE + 1) - CENTERJSAMPLE),
494 cinfo->sample_range_limit, CENTERJSAMPLE * sizeof(JSAMPLE));
500 * Master selection of decompression modules.
501 * This is done once at jpeg_start_decompress time. We determine
502 * which modules will be used and give them appropriate initialization calls.
503 * We also initialize the decompressor input side to begin consuming data.
505 * Since jpeg_read_header has finished, we know what is in the SOF
506 * and (first) SOS markers. We also have all the application parameter
511 master_selection(j_decompress_ptr cinfo)
513 my_master_ptr master = (my_master_ptr)cinfo->master;
514 boolean use_c_buffer;
516 JDIMENSION jd_samplesperrow;
518 /* Disable IDCT scaling and raw (downsampled) data output in lossless mode.
519 * IDCT scaling is not useful in lossless mode, and it must be disabled in
520 * order to properly calculate the output dimensions. Raw data output isn't
521 * particularly useful without subsampling and has not been tested in
524 if (cinfo->master->lossless) {
525 cinfo->raw_data_out = FALSE;
526 cinfo->scale_num = cinfo->scale_denom = 1;
529 /* Initialize dimensions and other stuff */
530 jpeg_calc_output_dimensions(cinfo);
531 prepare_range_limit_table(cinfo);
533 /* Width of an output scanline must be representable as JDIMENSION. */
534 samplesperrow = (long)cinfo->output_width *
535 (long)cinfo->out_color_components;
536 jd_samplesperrow = (JDIMENSION)samplesperrow;
537 if ((long)jd_samplesperrow != samplesperrow)
538 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
540 /* Initialize my private state */
541 master->pass_number = 0;
542 master->using_merged_upsample = use_merged_upsample(cinfo);
544 /* Color quantizer selection */
545 master->quantizer_1pass = NULL;
546 master->quantizer_2pass = NULL;
547 /* No mode changes if not using buffered-image mode. */
548 if (!cinfo->quantize_colors || !cinfo->buffered_image) {
549 cinfo->enable_1pass_quant = FALSE;
550 cinfo->enable_external_quant = FALSE;
551 cinfo->enable_2pass_quant = FALSE;
553 if (cinfo->quantize_colors) {
554 if (cinfo->raw_data_out)
555 ERREXIT(cinfo, JERR_NOTIMPL);
556 /* 2-pass quantizer only works in 3-component color space. */
557 if (cinfo->out_color_components != 3 ||
558 cinfo->out_color_space == JCS_RGB565) {
559 cinfo->enable_1pass_quant = TRUE;
560 cinfo->enable_external_quant = FALSE;
561 cinfo->enable_2pass_quant = FALSE;
562 cinfo->colormap = NULL;
563 } else if (cinfo->colormap != NULL) {
564 cinfo->enable_external_quant = TRUE;
565 } else if (cinfo->two_pass_quantize) {
566 cinfo->enable_2pass_quant = TRUE;
568 cinfo->enable_1pass_quant = TRUE;
571 if (cinfo->enable_1pass_quant) {
572 #ifdef QUANT_1PASS_SUPPORTED
573 if (cinfo->data_precision == 16)
574 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
575 else if (cinfo->data_precision == 12)
576 j12init_1pass_quantizer(cinfo);
578 jinit_1pass_quantizer(cinfo);
579 master->quantizer_1pass = cinfo->cquantize;
581 ERREXIT(cinfo, JERR_NOT_COMPILED);
585 /* We use the 2-pass code to map to external colormaps. */
586 if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
587 #ifdef QUANT_2PASS_SUPPORTED
588 if (cinfo->data_precision == 16)
589 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
590 else if (cinfo->data_precision == 12)
591 j12init_2pass_quantizer(cinfo);
593 jinit_2pass_quantizer(cinfo);
594 master->quantizer_2pass = cinfo->cquantize;
596 ERREXIT(cinfo, JERR_NOT_COMPILED);
599 /* If both quantizers are initialized, the 2-pass one is left active;
600 * this is necessary for starting with quantization to an external map.
604 /* Post-processing: in particular, color conversion first */
605 if (!cinfo->raw_data_out) {
606 if (master->using_merged_upsample) {
607 #ifdef UPSAMPLE_MERGING_SUPPORTED
608 if (cinfo->data_precision == 16)
609 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
610 else if (cinfo->data_precision == 12)
611 j12init_merged_upsampler(cinfo); /* does color conversion too */
613 jinit_merged_upsampler(cinfo); /* does color conversion too */
615 ERREXIT(cinfo, JERR_NOT_COMPILED);
618 if (cinfo->data_precision == 16) {
619 #ifdef D_LOSSLESS_SUPPORTED
620 j16init_color_deconverter(cinfo);
621 j16init_upsampler(cinfo);
623 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
625 } else if (cinfo->data_precision == 12) {
626 j12init_color_deconverter(cinfo);
627 j12init_upsampler(cinfo);
629 jinit_color_deconverter(cinfo);
630 jinit_upsampler(cinfo);
633 if (cinfo->data_precision == 16)
634 #ifdef D_LOSSLESS_SUPPORTED
635 j16init_d_post_controller(cinfo, cinfo->enable_2pass_quant);
637 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
639 else if (cinfo->data_precision == 12)
640 j12init_d_post_controller(cinfo, cinfo->enable_2pass_quant);
642 jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
645 if (cinfo->master->lossless) {
646 #ifdef D_LOSSLESS_SUPPORTED
647 /* Prediction, sample undifferencing, point transform, and sample size
650 if (cinfo->data_precision == 16)
651 j16init_lossless_decompressor(cinfo);
652 else if (cinfo->data_precision == 12)
653 j12init_lossless_decompressor(cinfo);
655 jinit_lossless_decompressor(cinfo);
656 /* Entropy decoding: either Huffman or arithmetic coding. */
657 if (cinfo->arith_code) {
658 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
660 jinit_lhuff_decoder(cinfo);
663 /* Initialize principal buffer controllers. */
664 use_c_buffer = cinfo->inputctl->has_multiple_scans ||
665 cinfo->buffered_image;
666 if (cinfo->data_precision == 16)
667 j16init_d_diff_controller(cinfo, use_c_buffer);
668 else if (cinfo->data_precision == 12)
669 j12init_d_diff_controller(cinfo, use_c_buffer);
671 jinit_d_diff_controller(cinfo, use_c_buffer);
673 ERREXIT(cinfo, JERR_NOT_COMPILED);
676 if (cinfo->data_precision == 16)
677 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
679 if (cinfo->data_precision == 12)
680 j12init_inverse_dct(cinfo);
682 jinit_inverse_dct(cinfo);
683 /* Entropy decoding: either Huffman or arithmetic coding. */
684 if (cinfo->arith_code) {
685 #ifdef D_ARITH_CODING_SUPPORTED
686 jinit_arith_decoder(cinfo);
688 ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
691 if (cinfo->progressive_mode) {
692 #ifdef D_PROGRESSIVE_SUPPORTED
693 jinit_phuff_decoder(cinfo);
695 ERREXIT(cinfo, JERR_NOT_COMPILED);
698 jinit_huff_decoder(cinfo);
701 /* Initialize principal buffer controllers. */
702 use_c_buffer = cinfo->inputctl->has_multiple_scans ||
703 cinfo->buffered_image;
704 if (cinfo->data_precision == 12)
705 j12init_d_coef_controller(cinfo, use_c_buffer);
707 jinit_d_coef_controller(cinfo, use_c_buffer);
710 if (!cinfo->raw_data_out) {
711 if (cinfo->data_precision == 16)
712 #ifdef D_LOSSLESS_SUPPORTED
713 j16init_d_main_controller(cinfo,
714 FALSE /* never need full buffer here */);
716 ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
718 else if (cinfo->data_precision == 12)
719 j12init_d_main_controller(cinfo,
720 FALSE /* never need full buffer here */);
722 jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
725 /* We can now tell the memory manager to allocate virtual arrays. */
726 (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo);
728 /* Initialize input side of decompressor to consume first scan. */
729 (*cinfo->inputctl->start_input_pass) (cinfo);
731 /* Set the first and last iMCU columns to decompress from single-scan images.
732 * By default, decompress all of the iMCU columns.
734 cinfo->master->first_iMCU_col = 0;
735 cinfo->master->last_iMCU_col = cinfo->MCUs_per_row - 1;
736 cinfo->master->last_good_iMCU_row = 0;
738 #ifdef D_MULTISCAN_FILES_SUPPORTED
739 /* If jpeg_start_decompress will read the whole file, initialize
740 * progress monitoring appropriately. The input step is counted
743 if (cinfo->progress != NULL && !cinfo->buffered_image &&
744 cinfo->inputctl->has_multiple_scans) {
746 /* Estimate number of scans to set pass_limit. */
747 if (cinfo->progressive_mode) {
748 /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
749 nscans = 2 + 3 * cinfo->num_components;
751 /* For a nonprogressive multiscan file, estimate 1 scan per component. */
752 nscans = cinfo->num_components;
754 cinfo->progress->pass_counter = 0L;
755 cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans;
756 cinfo->progress->completed_passes = 0;
757 cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
758 /* Count the input pass as done */
759 master->pass_number++;
761 #endif /* D_MULTISCAN_FILES_SUPPORTED */
767 * This is called at the beginning of each output pass. We determine which
768 * modules will be active during this pass and give them appropriate
769 * start_pass calls. We also set is_dummy_pass to indicate whether this
770 * is a "real" output pass or a dummy pass for color quantization.
771 * (In the latter case, jdapistd.c will crank the pass to completion.)
775 prepare_for_output_pass(j_decompress_ptr cinfo)
777 my_master_ptr master = (my_master_ptr)cinfo->master;
779 if (master->pub.is_dummy_pass) {
780 #ifdef QUANT_2PASS_SUPPORTED
781 /* Final pass of 2-pass quantization */
782 master->pub.is_dummy_pass = FALSE;
783 (*cinfo->cquantize->start_pass) (cinfo, FALSE);
784 (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
785 (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
787 ERREXIT(cinfo, JERR_NOT_COMPILED);
788 #endif /* QUANT_2PASS_SUPPORTED */
790 if (cinfo->quantize_colors && cinfo->colormap == NULL) {
791 /* Select new quantization method */
792 if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
793 cinfo->cquantize = master->quantizer_2pass;
794 master->pub.is_dummy_pass = TRUE;
795 } else if (cinfo->enable_1pass_quant) {
796 cinfo->cquantize = master->quantizer_1pass;
798 ERREXIT(cinfo, JERR_MODE_CHANGE);
801 (*cinfo->idct->start_pass) (cinfo);
802 (*cinfo->coef->start_output_pass) (cinfo);
803 if (!cinfo->raw_data_out) {
804 if (!master->using_merged_upsample)
805 (*cinfo->cconvert->start_pass) (cinfo);
806 (*cinfo->upsample->start_pass) (cinfo);
807 if (cinfo->quantize_colors)
808 (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
809 (*cinfo->post->start_pass) (cinfo,
810 (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
811 (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
815 /* Set up progress monitor's pass info if present */
816 if (cinfo->progress != NULL) {
817 cinfo->progress->completed_passes = master->pass_number;
818 cinfo->progress->total_passes = master->pass_number +
819 (master->pub.is_dummy_pass ? 2 : 1);
820 /* In buffered-image mode, we assume one more output pass if EOI not
821 * yet reached, but no more passes if EOI has been reached.
823 if (cinfo->buffered_image && !cinfo->inputctl->eoi_reached) {
824 cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
831 * Finish up at end of an output pass.
835 finish_output_pass(j_decompress_ptr cinfo)
837 my_master_ptr master = (my_master_ptr)cinfo->master;
839 if (cinfo->quantize_colors)
840 (*cinfo->cquantize->finish_pass) (cinfo);
841 master->pass_number++;
845 #ifdef D_MULTISCAN_FILES_SUPPORTED
848 * Switch to a new external colormap between output passes.
852 jpeg_new_colormap(j_decompress_ptr cinfo)
854 my_master_ptr master = (my_master_ptr)cinfo->master;
856 /* Prevent application from calling me at wrong times */
857 if (cinfo->global_state != DSTATE_BUFIMAGE)
858 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
860 if (cinfo->quantize_colors && cinfo->enable_external_quant &&
861 cinfo->colormap != NULL) {
862 /* Select 2-pass quantizer for external colormap use */
863 cinfo->cquantize = master->quantizer_2pass;
864 /* Notify quantizer of colormap change */
865 (*cinfo->cquantize->new_color_map) (cinfo);
866 master->pub.is_dummy_pass = FALSE; /* just in case */
868 ERREXIT(cinfo, JERR_MODE_CHANGE);
871 #endif /* D_MULTISCAN_FILES_SUPPORTED */
875 * Initialize master decompression control and select active modules.
876 * This is performed at the start of jpeg_start_decompress.
880 jinit_master_decompress(j_decompress_ptr cinfo)
882 my_master_ptr master = (my_master_ptr)cinfo->master;
884 master->pub.prepare_for_output_pass = prepare_for_output_pass;
885 master->pub.finish_output_pass = finish_output_pass;
887 master->pub.is_dummy_pass = FALSE;
888 master->pub.jinit_upsampler_no_alloc = FALSE;
890 master_selection(cinfo);