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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*
2 * jdcoefct.c
3 *
4 * Copyright (C) 1994-1997, Thomas G. Lane.
5 * Modified 2002-2020 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.
8 *
9 * This file contains the coefficient buffer controller for decompression.
10 * This controller is the top level of the JPEG decompressor proper.
11 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
12 *
13 * In buffered-image mode, this controller is the interface between
14 * input-oriented processing and output-oriented processing.
15 * Also, the input side (only) is used when reading a file for transcoding.
16 */
17
18 #define JPEG_INTERNALS
19 #include "jinclude.h"
20 #include "jpeglib.h"
21
22
23 /* Block smoothing is only applicable for progressive JPEG, so: */
24 #ifndef D_PROGRESSIVE_SUPPORTED
25 #undef BLOCK_SMOOTHING_SUPPORTED
26 #endif
27
28
29 /* Private buffer controller object */
30
31 typedef struct {
32 struct jpeg_d_coef_controller pub; /* public fields */
33
34 /* These variables keep track of the current location of the input side. */
35 /* cinfo->input_iMCU_row is also used for this. */
36 JDIMENSION MCU_ctr; /* counts MCUs processed in current row */
37 int MCU_vert_offset; /* counts MCU rows within iMCU row */
38 int MCU_rows_per_iMCU_row; /* number of such rows needed */
39
40 /* The output side's location is represented by cinfo->output_iMCU_row. */
41
42 /* In single-pass modes, it's sufficient to buffer just one MCU.
43 * We append a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
44 * and let the entropy decoder write into that workspace each time.
45 * In multi-pass modes, this array points to the current MCU's blocks
46 * within the virtual arrays; it is used only by the input side.
47 */
48 JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
49
50 #ifdef D_MULTISCAN_FILES_SUPPORTED
51 /* In multi-pass modes, we need a virtual block array for each component. */
52 jvirt_barray_ptr whole_image[MAX_COMPONENTS];
53 #endif
54
55 #ifdef BLOCK_SMOOTHING_SUPPORTED
56 /* When doing block smoothing, we latch coefficient Al values here */
57 int * coef_bits_latch;
58 #define SAVED_COEFS 6 /* we save coef_bits[0..5] */
59 #endif
60
61 /* Workspace for single-pass modes (omitted otherwise). */
62 JBLOCK blk_buffer[D_MAX_BLOCKS_IN_MCU];
63 } my_coef_controller;
64
65 typedef my_coef_controller * my_coef_ptr;
66
67
68 /* Forward declarations */
69 METHODDEF(int) decompress_onepass
70 JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
71 #ifdef D_MULTISCAN_FILES_SUPPORTED
72 METHODDEF(int) decompress_data
73 JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
74 #endif
75 #ifdef BLOCK_SMOOTHING_SUPPORTED
76 LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
77 METHODDEF(int) decompress_smooth_data
78 JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
79 #endif
80
81
82 LOCAL(void)
83 start_iMCU_row (j_decompress_ptr cinfo)
84 /* Reset within-iMCU-row counters for a new row (input side) */
85 {
86 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
87
88 /* In an interleaved scan, an MCU row is the same as an iMCU row.
89 * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
90 * But at the bottom of the image, process only what's left.
91 */
92 if (cinfo->comps_in_scan > 1) {
93 coef->MCU_rows_per_iMCU_row = 1;
94 } else {
95 if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
96 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
97 else
98 coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
99 }
100
101 coef->MCU_ctr = 0;
102 coef->MCU_vert_offset = 0;
103 }
104
105
106 /*
107 * Initialize for an input processing pass.
108 */
109
110 METHODDEF(void)
111 start_input_pass (j_decompress_ptr cinfo)
112 {
113 cinfo->input_iMCU_row = 0;
114 start_iMCU_row(cinfo);
115 }
116
117
118 /*
119 * Initialize for an output processing pass.
120 */
121
122 METHODDEF(void)
123 start_output_pass (j_decompress_ptr cinfo)
124 {
125 #ifdef BLOCK_SMOOTHING_SUPPORTED
126 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
127
128 /* If multipass, check to see whether to use block smoothing on this pass */
129 if (coef->pub.coef_arrays != NULL) {
130 if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
131 coef->pub.decompress_data = decompress_smooth_data;
132 else
133 coef->pub.decompress_data = decompress_data;
134 }
135 #endif
136 cinfo->output_iMCU_row = 0;
137 }
138
139
140 /*
141 * Decompress and return some data in the single-pass case.
142 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
143 * Input and output must run in lockstep since we have only a one-MCU buffer.
144 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
145 *
146 * NB: output_buf contains a plane for each component in image,
147 * which we index according to the component's SOF position.
148 */
149
150 METHODDEF(int)
151 decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
152 {
153 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
154 JDIMENSION MCU_col_num; /* index of current MCU within row */
155 JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
156 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
157 int ci, xindex, yindex, yoffset, useful_width;
158 JBLOCKROW blkp;
159 JSAMPARRAY output_ptr;
160 JDIMENSION start_col, output_col;
161 jpeg_component_info *compptr;
162 inverse_DCT_method_ptr inverse_DCT;
163
164 /* Loop to process as much as one whole iMCU row */
165 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
166 yoffset++) {
167 for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col;
168 MCU_col_num++) {
169 blkp = coef->blk_buffer; /* pointer to current DCT block within MCU */
170 /* Try to fetch an MCU. Entropy decoder expects buffer to be zeroed. */
171 if (cinfo->lim_Se) /* can bypass in DC only case */
172 MEMZERO(blkp, cinfo->blocks_in_MCU * SIZEOF(JBLOCK));
173 if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
174 /* Suspension forced; update state counters and exit */
175 coef->MCU_vert_offset = yoffset;
176 coef->MCU_ctr = MCU_col_num;
177 return JPEG_SUSPENDED;
178 }
179 /* Determine where data should go in output_buf and do the IDCT thing.
180 * We skip dummy blocks at the right and bottom edges (but blkp gets
181 * incremented past them!).
182 */
183 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
184 compptr = cinfo->cur_comp_info[ci];
185 /* Don't bother to IDCT an uninteresting component. */
186 if (! compptr->component_needed) {
187 blkp += compptr->MCU_blocks;
188 continue;
189 }
190 inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
191 output_ptr = output_buf[compptr->component_index] +
192 yoffset * compptr->DCT_v_scaled_size;
193 useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
194 : compptr->last_col_width;
195 start_col = MCU_col_num * compptr->MCU_sample_width;
196 for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
197 if (cinfo->input_iMCU_row < last_iMCU_row ||
198 yoffset + yindex < compptr->last_row_height) {
199 output_col = start_col;
200 for (xindex = 0; xindex < useful_width; xindex++) {
201 (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) (blkp + xindex),
202 output_ptr, output_col);
203 output_col += compptr->DCT_h_scaled_size;
204 }
205 output_ptr += compptr->DCT_v_scaled_size;
206 }
207 blkp += compptr->MCU_width;
208 }
209 }
210 }
211 /* Completed an MCU row, but perhaps not an iMCU row */
212 coef->MCU_ctr = 0;
213 }
214 /* Completed the iMCU row, advance counters for next one */
215 cinfo->output_iMCU_row++;
216 if (++(cinfo->input_iMCU_row) <= last_iMCU_row) {
217 start_iMCU_row(cinfo);
218 return JPEG_ROW_COMPLETED;
219 }
220 /* Completed the scan */
221 (*cinfo->inputctl->finish_input_pass) (cinfo);
222 return JPEG_SCAN_COMPLETED;
223 }
224
225
226 /*
227 * Dummy consume-input routine for single-pass operation.
228 */
229
230 METHODDEF(int)
231 dummy_consume_data (j_decompress_ptr cinfo)
232 {
233 return JPEG_SUSPENDED; /* Always indicate nothing was done */
234 }
235
236
237 #ifdef D_MULTISCAN_FILES_SUPPORTED
238
239 /*
240 * Consume input data and store it in the full-image coefficient buffer.
241 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
242 * ie, v_samp_factor block rows for each component in the scan.
243 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
244 */
245
246 METHODDEF(int)
247 consume_data (j_decompress_ptr cinfo)
248 {
249 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
250 JDIMENSION MCU_col_num; /* index of current MCU within row */
251 int ci, xindex, yindex, yoffset;
252 JDIMENSION start_col;
253 JBLOCKARRAY blkp;
254 JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
255 JBLOCKROW buffer_ptr;
256 jpeg_component_info *compptr;
257
258 /* Align the virtual buffers for the components used in this scan. */
259 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
260 compptr = cinfo->cur_comp_info[ci];
261 buffer[ci] = (*cinfo->mem->access_virt_barray)
262 ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
263 cinfo->input_iMCU_row * compptr->v_samp_factor,
264 (JDIMENSION) compptr->v_samp_factor, TRUE);
265 /* Note: entropy decoder expects buffer to be zeroed,
266 * but this is handled automatically by the memory manager
267 * because we requested a pre-zeroed array.
268 */
269 }
270
271 /* Loop to process one whole iMCU row */
272 for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
273 yoffset++) {
274 for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row;
275 MCU_col_num++) {
276 /* Construct list of pointers to DCT blocks belonging to this MCU */
277 blkp = coef->MCU_buffer; /* pointer to current DCT block within MCU */
278 for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
279 compptr = cinfo->cur_comp_info[ci];
280 start_col = MCU_col_num * compptr->MCU_width;
281 for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
282 buffer_ptr = buffer[ci][yoffset + yindex] + start_col;
283 xindex = compptr->MCU_width;
284 do {
285 *blkp++ = buffer_ptr++;
286 } while (--xindex);
287 }
288 }
289 /* Try to fetch the MCU. */
290 if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) {
291 /* Suspension forced; update state counters and exit */
292 coef->MCU_vert_offset = yoffset;
293 coef->MCU_ctr = MCU_col_num;
294 return JPEG_SUSPENDED;
295 }
296 }
297 /* Completed an MCU row, but perhaps not an iMCU row */
298 coef->MCU_ctr = 0;
299 }
300 /* Completed the iMCU row, advance counters for next one */
301 if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) {
302 start_iMCU_row(cinfo);
303 return JPEG_ROW_COMPLETED;
304 }
305 /* Completed the scan */
306 (*cinfo->inputctl->finish_input_pass) (cinfo);
307 return JPEG_SCAN_COMPLETED;
308 }
309
310
311 /*
312 * Decompress and return some data in the multi-pass case.
313 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
314 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
315 *
316 * NB: output_buf contains a plane for each component in image.
317 */
318
319 METHODDEF(int)
320 decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
321 {
322 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
323 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
324 JDIMENSION block_num;
325 int ci, block_row, block_rows;
326 JBLOCKARRAY buffer;
327 JBLOCKROW buffer_ptr;
328 JSAMPARRAY output_ptr;
329 JDIMENSION output_col;
330 jpeg_component_info *compptr;
331 inverse_DCT_method_ptr inverse_DCT;
332
333 /* Force some input to be done if we are getting ahead of the input. */
334 while (cinfo->input_scan_number < cinfo->output_scan_number ||
335 (cinfo->input_scan_number == cinfo->output_scan_number &&
336 cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) {
337 if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
338 return JPEG_SUSPENDED;
339 }
340
341 /* OK, output from the virtual arrays. */
342 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
343 ci++, compptr++) {
344 /* Don't bother to IDCT an uninteresting component. */
345 if (! compptr->component_needed)
346 continue;
347 /* Align the virtual buffer for this component. */
348 buffer = (*cinfo->mem->access_virt_barray)
349 ((j_common_ptr) cinfo, coef->whole_image[ci],
350 cinfo->output_iMCU_row * compptr->v_samp_factor,
351 (JDIMENSION) compptr->v_samp_factor, FALSE);
352 /* Count non-dummy DCT block rows in this iMCU row. */
353 if (cinfo->output_iMCU_row < last_iMCU_row)
354 block_rows = compptr->v_samp_factor;
355 else {
356 /* NB: can't use last_row_height here; it is input-side-dependent! */
357 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
358 if (block_rows == 0) block_rows = compptr->v_samp_factor;
359 }
360 inverse_DCT = cinfo->idct->inverse_DCT[ci];
361 output_ptr = output_buf[ci];
362 /* Loop over all DCT blocks to be processed. */
363 for (block_row = 0; block_row < block_rows; block_row++) {
364 buffer_ptr = buffer[block_row];
365 output_col = 0;
366 for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) {
367 (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr,
368 output_ptr, output_col);
369 buffer_ptr++;
370 output_col += compptr->DCT_h_scaled_size;
371 }
372 output_ptr += compptr->DCT_v_scaled_size;
373 }
374 }
375
376 if (++(cinfo->output_iMCU_row) <= last_iMCU_row)
377 return JPEG_ROW_COMPLETED;
378 return JPEG_SCAN_COMPLETED;
379 }
380
381 #endif /* D_MULTISCAN_FILES_SUPPORTED */
382
383
384 #ifdef BLOCK_SMOOTHING_SUPPORTED
385
386 /*
387 * This code applies interblock smoothing as described by section K.8
388 * of the JPEG standard: the first 5 AC coefficients are estimated from
389 * the DC values of a DCT block and its 8 neighboring blocks.
390 * We apply smoothing only for progressive JPEG decoding, and only if
391 * the coefficients it can estimate are not yet known to full precision.
392 */
393
394 /* Natural-order array positions of the first 5 zigzag-order coefficients */
395 #define Q01_POS 1
396 #define Q10_POS 8
397 #define Q20_POS 16
398 #define Q11_POS 9
399 #define Q02_POS 2
400
401 /*
402 * Determine whether block smoothing is applicable and safe.
403 * We also latch the current states of the coef_bits[] entries for the
404 * AC coefficients; otherwise, if the input side of the decompressor
405 * advances into a new scan, we might think the coefficients are known
406 * more accurately than they really are.
407 */
408
409 LOCAL(boolean)
410 smoothing_ok (j_decompress_ptr cinfo)
411 {
412 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
413 boolean smoothing_useful = FALSE;
414 int ci, coefi;
415 jpeg_component_info *compptr;
416 JQUANT_TBL * qtable;
417 int * coef_bits;
418 int * coef_bits_latch;
419
420 if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
421 return FALSE;
422
423 /* Allocate latch area if not already done */
424 if (coef->coef_bits_latch == NULL)
425 coef->coef_bits_latch = (int *) (*cinfo->mem->alloc_small)
426 ((j_common_ptr) cinfo, JPOOL_IMAGE,
427 cinfo->num_components * (SAVED_COEFS * SIZEOF(int)));
428 coef_bits_latch = coef->coef_bits_latch;
429
430 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
431 ci++, compptr++) {
432 /* All components' quantization values must already be latched. */
433 if ((qtable = compptr->quant_table) == NULL)
434 return FALSE;
435 /* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
436 if (qtable->quantval[0] == 0 ||
437 qtable->quantval[Q01_POS] == 0 ||
438 qtable->quantval[Q10_POS] == 0 ||
439 qtable->quantval[Q20_POS] == 0 ||
440 qtable->quantval[Q11_POS] == 0 ||
441 qtable->quantval[Q02_POS] == 0)
442 return FALSE;
443 /* DC values must be at least partly known for all components. */
444 coef_bits = cinfo->coef_bits[ci];
445 if (coef_bits[0] < 0)
446 return FALSE;
447 /* Block smoothing is helpful if some AC coefficients remain inaccurate. */
448 for (coefi = 1; coefi <= 5; coefi++) {
449 coef_bits_latch[coefi] = coef_bits[coefi];
450 if (coef_bits[coefi] != 0)
451 smoothing_useful = TRUE;
452 }
453 coef_bits_latch += SAVED_COEFS;
454 }
455
456 return smoothing_useful;
457 }
458
459
460 /*
461 * Variant of decompress_data for use when doing block smoothing.
462 */
463
464 METHODDEF(int)
465 decompress_smooth_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
466 {
467 my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
468 JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
469 JDIMENSION block_num, last_block_column;
470 int ci, block_row, block_rows, access_rows;
471 JBLOCKARRAY buffer;
472 JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
473 JSAMPARRAY output_ptr;
474 JDIMENSION output_col;
475 jpeg_component_info *compptr;
476 inverse_DCT_method_ptr inverse_DCT;
477 boolean first_row, last_row;
478 JBLOCK workspace;
479 int *coef_bits;
480 JQUANT_TBL *quanttbl;
481 INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
482 int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
483 int Al, pred;
484
485 /* Force some input to be done if we are getting ahead of the input. */
486 while (cinfo->input_scan_number <= cinfo->output_scan_number &&
487 ! cinfo->inputctl->eoi_reached) {
488 if (cinfo->input_scan_number == cinfo->output_scan_number) {
489 /* If input is working on current scan, we ordinarily want it to
490 * have completed the current row. But if input scan is DC,
491 * we want it to keep one row ahead so that next block row's DC
492 * values are up to date.
493 */
494 JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
495 if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
496 break;
497 }
498 if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
499 return JPEG_SUSPENDED;
500 }
501
502 /* OK, output from the virtual arrays. */
503 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
504 ci++, compptr++) {
505 /* Don't bother to IDCT an uninteresting component. */
506 if (! compptr->component_needed)
507 continue;
508 /* Count non-dummy DCT block rows in this iMCU row. */
509 if (cinfo->output_iMCU_row < last_iMCU_row) {
510 block_rows = compptr->v_samp_factor;
511 access_rows = block_rows * 2; /* this and next iMCU row */
512 last_row = FALSE;
513 } else {
514 /* NB: can't use last_row_height here; it is input-side-dependent! */
515 block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
516 if (block_rows == 0) block_rows = compptr->v_samp_factor;
517 access_rows = block_rows; /* this iMCU row only */
518 last_row = TRUE;
519 }
520 /* Align the virtual buffer for this component. */
521 if (cinfo->output_iMCU_row > 0) {
522 access_rows += compptr->v_samp_factor; /* prior iMCU row too */
523 buffer = (*cinfo->mem->access_virt_barray)
524 ((j_common_ptr) cinfo, coef->whole_image[ci],
525 (cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
526 (JDIMENSION) access_rows, FALSE);
527 buffer += compptr->v_samp_factor; /* point to current iMCU row */
528 first_row = FALSE;
529 } else {
530 buffer = (*cinfo->mem->access_virt_barray)
531 ((j_common_ptr) cinfo, coef->whole_image[ci],
532 (JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
533 first_row = TRUE;
534 }
535 /* Fetch component-dependent info */
536 coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
537 quanttbl = compptr->quant_table;
538 Q00 = quanttbl->quantval[0];
539 Q01 = quanttbl->quantval[Q01_POS];
540 Q10 = quanttbl->quantval[Q10_POS];
541 Q20 = quanttbl->quantval[Q20_POS];
542 Q11 = quanttbl->quantval[Q11_POS];
543 Q02 = quanttbl->quantval[Q02_POS];
544 inverse_DCT = cinfo->idct->inverse_DCT[ci];
545 output_ptr = output_buf[ci];
546 /* Loop over all DCT blocks to be processed. */
547 for (block_row = 0; block_row < block_rows; block_row++) {
548 buffer_ptr = buffer[block_row];
549 if (first_row && block_row == 0)
550 prev_block_row = buffer_ptr;
551 else
552 prev_block_row = buffer[block_row-1];
553 if (last_row && block_row == block_rows-1)
554 next_block_row = buffer_ptr;
555 else
556 next_block_row = buffer[block_row+1];
557 /* We fetch the surrounding DC values using a sliding-register approach.
558 * Initialize all nine here so as to do the right thing on narrow pics.
559 */
560 DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
561 DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
562 DC7 = DC8 = DC9 = (int) next_block_row[0][0];
563 output_col = 0;
564 last_block_column = compptr->width_in_blocks - 1;
565 for (block_num = 0; block_num <= last_block_column; block_num++) {
566 /* Fetch current DCT block into workspace so we can modify it. */
567 jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
568 /* Update DC values */
569 if (block_num < last_block_column) {
570 DC3 = (int) prev_block_row[1][0];
571 DC6 = (int) buffer_ptr[1][0];
572 DC9 = (int) next_block_row[1][0];
573 }
574 /* Compute coefficient estimates per K.8.
575 * An estimate is applied only if coefficient is still zero,
576 * and is not known to be fully accurate.
577 */
578 /* AC01 */
579 if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) {
580 num = 36 * Q00 * (DC4 - DC6);
581 if (num >= 0) {
582 pred = (int) (((Q01<<7) + num) / (Q01<<8));
583 if (Al > 0 && pred >= (1<<Al))
584 pred = (1<<Al)-1;
585 } else {
586 pred = (int) (((Q01<<7) - num) / (Q01<<8));
587 if (Al > 0 && pred >= (1<<Al))
588 pred = (1<<Al)-1;
589 pred = -pred;
590 }
591 workspace[1] = (JCOEF) pred;
592 }
593 /* AC10 */
594 if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) {
595 num = 36 * Q00 * (DC2 - DC8);
596 if (num >= 0) {
597 pred = (int) (((Q10<<7) + num) / (Q10<<8));
598 if (Al > 0 && pred >= (1<<Al))
599 pred = (1<<Al)-1;
600 } else {
601 pred = (int) (((Q10<<7) - num) / (Q10<<8));
602 if (Al > 0 && pred >= (1<<Al))
603 pred = (1<<Al)-1;
604 pred = -pred;
605 }
606 workspace[8] = (JCOEF) pred;
607 }
608 /* AC20 */
609 if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) {
610 num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
611 if (num >= 0) {
612 pred = (int) (((Q20<<7) + num) / (Q20<<8));
613 if (Al > 0 && pred >= (1<<Al))
614 pred = (1<<Al)-1;
615 } else {
616 pred = (int) (((Q20<<7) - num) / (Q20<<8));
617 if (Al > 0 && pred >= (1<<Al))
618 pred = (1<<Al)-1;
619 pred = -pred;
620 }
621 workspace[16] = (JCOEF) pred;
622 }
623 /* AC11 */
624 if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) {
625 num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
626 if (num >= 0) {
627 pred = (int) (((Q11<<7) + num) / (Q11<<8));
628 if (Al > 0 && pred >= (1<<Al))
629 pred = (1<<Al)-1;
630 } else {
631 pred = (int) (((Q11<<7) - num) / (Q11<<8));
632 if (Al > 0 && pred >= (1<<Al))
633 pred = (1<<Al)-1;
634 pred = -pred;
635 }
636 workspace[9] = (JCOEF) pred;
637 }
638 /* AC02 */
639 if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) {
640 num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
641 if (num >= 0) {
642 pred = (int) (((Q02<<7) + num) / (Q02<<8));
643 if (Al > 0 && pred >= (1<<Al))
644 pred = (1<<Al)-1;
645 } else {
646 pred = (int) (((Q02<<7) - num) / (Q02<<8));
647 if (Al > 0 && pred >= (1<<Al))
648 pred = (1<<Al)-1;
649 pred = -pred;
650 }
651 workspace[2] = (JCOEF) pred;
652 }
653 /* OK, do the IDCT */
654 (*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace,
655 output_ptr, output_col);
656 /* Advance for next column */
657 DC1 = DC2; DC2 = DC3;
658 DC4 = DC5; DC5 = DC6;
659 DC7 = DC8; DC8 = DC9;
660 buffer_ptr++, prev_block_row++, next_block_row++;
661 output_col += compptr->DCT_h_scaled_size;
662 }
663 output_ptr += compptr->DCT_v_scaled_size;
664 }
665 }
666
667 if (++(cinfo->output_iMCU_row) <= last_iMCU_row)
668 return JPEG_ROW_COMPLETED;
669 return JPEG_SCAN_COMPLETED;
670 }
671
672 #endif /* BLOCK_SMOOTHING_SUPPORTED */
673
674
675 /*
676 * Initialize coefficient buffer controller.
677 */
678
679 GLOBAL(void)
680 jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
681 {
682 my_coef_ptr coef;
683
684 if (need_full_buffer) {
685 #ifdef D_MULTISCAN_FILES_SUPPORTED
686 /* Allocate a full-image virtual array for each component, */
687 /* padded to a multiple of samp_factor DCT blocks in each direction. */
688 /* Note we ask for a pre-zeroed array. */
689 int ci, access_rows;
690 jpeg_component_info *compptr;
691
692 coef = (my_coef_ptr) (*cinfo->mem->alloc_small)
693 ((j_common_ptr) cinfo, JPOOL_IMAGE,
694 SIZEOF(my_coef_controller) - SIZEOF(coef->blk_buffer));
695 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
696 ci++, compptr++) {
697 access_rows = compptr->v_samp_factor;
698 #ifdef BLOCK_SMOOTHING_SUPPORTED
699 /* If block smoothing could be used, need a bigger window */
700 if (cinfo->progressive_mode)
701 access_rows *= 3;
702 #endif
703 coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
704 ((j_common_ptr) cinfo, JPOOL_IMAGE, TRUE,
705 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
706 (long) compptr->h_samp_factor),
707 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
708 (long) compptr->v_samp_factor),
709 (JDIMENSION) access_rows);
710 }
711 coef->pub.consume_data = consume_data;
712 coef->pub.decompress_data = decompress_data;
713 coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
714 #else
715 ERREXIT(cinfo, JERR_NOT_COMPILED);
716 #endif
717 } else {
718 /* We only need a single-MCU buffer. */
719 JBLOCKARRAY blkp;
720 JBLOCKROW buffer_ptr;
721 int bi;
722
723 coef = (my_coef_ptr) (*cinfo->mem->alloc_small)
724 ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_coef_controller));
725 buffer_ptr = coef->blk_buffer;
726 if (cinfo->lim_Se == 0) /* DC only case: want to bypass later */
727 MEMZERO(buffer_ptr, SIZEOF(coef->blk_buffer));
728 blkp = coef->MCU_buffer;
729 bi = D_MAX_BLOCKS_IN_MCU;
730 do {
731 *blkp++ = buffer_ptr++;
732 } while (--bi);
733 coef->pub.consume_data = dummy_consume_data;
734 coef->pub.decompress_data = decompress_onepass;
735 coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
736 }
737
738 coef->pub.start_input_pass = start_input_pass;
739 coef->pub.start_output_pass = start_output_pass;
740 #ifdef BLOCK_SMOOTHING_SUPPORTED
741 coef->coef_bits_latch = NULL;
742 #endif
743 cinfo->coef = &coef->pub;
744 }