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