1 | /* |
2 | * jdapistd.c |
3 | * |
4 | * This file was part of the Independent JPEG Group's software: |
5 | * Copyright (C) 1994-1996, Thomas G. Lane. |
6 | * libjpeg-turbo Modifications: |
7 | * Copyright (C) 2010, 2015-2020, D. R. Commander. |
8 | * Copyright (C) 2015, Google, Inc. |
9 | * For conditions of distribution and use, see the accompanying README.ijg |
10 | * file. |
11 | * |
12 | * This file contains application interface code for the decompression half |
13 | * of the JPEG library. These are the "standard" API routines that are |
14 | * used in the normal full-decompression case. They are not used by a |
15 | * transcoding-only application. Note that if an application links in |
16 | * jpeg_start_decompress, it will end up linking in the entire decompressor. |
17 | * We thus must separate this file from jdapimin.c to avoid linking the |
18 | * whole decompression library into a transcoder. |
19 | */ |
20 | |
21 | #include "jinclude.h" |
22 | #include "jdmainct.h" |
23 | #include "jdcoefct.h" |
24 | #include "jdmaster.h" |
25 | #include "jdmerge.h" |
26 | #include "jdsample.h" |
27 | #include "jmemsys.h" |
28 | |
29 | /* Forward declarations */ |
30 | LOCAL(boolean) output_pass_setup(j_decompress_ptr cinfo); |
31 | |
32 | |
33 | /* |
34 | * Decompression initialization. |
35 | * jpeg_read_header must be completed before calling this. |
36 | * |
37 | * If a multipass operating mode was selected, this will do all but the |
38 | * last pass, and thus may take a great deal of time. |
39 | * |
40 | * Returns FALSE if suspended. The return value need be inspected only if |
41 | * a suspending data source is used. |
42 | */ |
43 | |
44 | GLOBAL(boolean) |
45 | jpeg_start_decompress(j_decompress_ptr cinfo) |
46 | { |
47 | if (cinfo->global_state == DSTATE_READY) { |
48 | /* First call: initialize master control, select active modules */ |
49 | jinit_master_decompress(cinfo); |
50 | if (cinfo->buffered_image) { |
51 | /* No more work here; expecting jpeg_start_output next */ |
52 | cinfo->global_state = DSTATE_BUFIMAGE; |
53 | return TRUE; |
54 | } |
55 | cinfo->global_state = DSTATE_PRELOAD; |
56 | } |
57 | if (cinfo->global_state == DSTATE_PRELOAD) { |
58 | /* If file has multiple scans, absorb them all into the coef buffer */ |
59 | if (cinfo->inputctl->has_multiple_scans) { |
60 | #ifdef D_MULTISCAN_FILES_SUPPORTED |
61 | for (;;) { |
62 | int retcode; |
63 | /* Call progress monitor hook if present */ |
64 | if (cinfo->progress != NULL) |
65 | (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
66 | /* Absorb some more input */ |
67 | retcode = (*cinfo->inputctl->consume_input) (cinfo); |
68 | if (retcode == JPEG_SUSPENDED) |
69 | return FALSE; |
70 | if (retcode == JPEG_REACHED_EOI) |
71 | break; |
72 | /* Advance progress counter if appropriate */ |
73 | if (cinfo->progress != NULL && |
74 | (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) { |
75 | if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) { |
76 | /* jdmaster underestimated number of scans; ratchet up one scan */ |
77 | cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows; |
78 | } |
79 | } |
80 | } |
81 | #else |
82 | ERREXIT(cinfo, JERR_NOT_COMPILED); |
83 | #endif /* D_MULTISCAN_FILES_SUPPORTED */ |
84 | } |
85 | cinfo->output_scan_number = cinfo->input_scan_number; |
86 | } else if (cinfo->global_state != DSTATE_PRESCAN) |
87 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
88 | /* Perform any dummy output passes, and set up for the final pass */ |
89 | return output_pass_setup(cinfo); |
90 | } |
91 | |
92 | |
93 | /* |
94 | * Set up for an output pass, and perform any dummy pass(es) needed. |
95 | * Common subroutine for jpeg_start_decompress and jpeg_start_output. |
96 | * Entry: global_state = DSTATE_PRESCAN only if previously suspended. |
97 | * Exit: If done, returns TRUE and sets global_state for proper output mode. |
98 | * If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN. |
99 | */ |
100 | |
101 | LOCAL(boolean) |
102 | output_pass_setup(j_decompress_ptr cinfo) |
103 | { |
104 | if (cinfo->global_state != DSTATE_PRESCAN) { |
105 | /* First call: do pass setup */ |
106 | (*cinfo->master->prepare_for_output_pass) (cinfo); |
107 | cinfo->output_scanline = 0; |
108 | cinfo->global_state = DSTATE_PRESCAN; |
109 | } |
110 | /* Loop over any required dummy passes */ |
111 | while (cinfo->master->is_dummy_pass) { |
112 | #ifdef QUANT_2PASS_SUPPORTED |
113 | /* Crank through the dummy pass */ |
114 | while (cinfo->output_scanline < cinfo->output_height) { |
115 | JDIMENSION last_scanline; |
116 | /* Call progress monitor hook if present */ |
117 | if (cinfo->progress != NULL) { |
118 | cinfo->progress->pass_counter = (long)cinfo->output_scanline; |
119 | cinfo->progress->pass_limit = (long)cinfo->output_height; |
120 | (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
121 | } |
122 | /* Process some data */ |
123 | last_scanline = cinfo->output_scanline; |
124 | (*cinfo->main->process_data) (cinfo, (JSAMPARRAY)NULL, |
125 | &cinfo->output_scanline, (JDIMENSION)0); |
126 | if (cinfo->output_scanline == last_scanline) |
127 | return FALSE; /* No progress made, must suspend */ |
128 | } |
129 | /* Finish up dummy pass, and set up for another one */ |
130 | (*cinfo->master->finish_output_pass) (cinfo); |
131 | (*cinfo->master->prepare_for_output_pass) (cinfo); |
132 | cinfo->output_scanline = 0; |
133 | #else |
134 | ERREXIT(cinfo, JERR_NOT_COMPILED); |
135 | #endif /* QUANT_2PASS_SUPPORTED */ |
136 | } |
137 | /* Ready for application to drive output pass through |
138 | * jpeg_read_scanlines or jpeg_read_raw_data. |
139 | */ |
140 | cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING; |
141 | return TRUE; |
142 | } |
143 | |
144 | |
145 | /* |
146 | * Enable partial scanline decompression |
147 | * |
148 | * Must be called after jpeg_start_decompress() and before any calls to |
149 | * jpeg_read_scanlines() or jpeg_skip_scanlines(). |
150 | * |
151 | * Refer to libjpeg.txt for more information. |
152 | */ |
153 | |
154 | GLOBAL(void) |
155 | jpeg_crop_scanline(j_decompress_ptr cinfo, JDIMENSION *xoffset, |
156 | JDIMENSION *width) |
157 | { |
158 | int ci, align, orig_downsampled_width; |
159 | JDIMENSION input_xoffset; |
160 | boolean reinit_upsampler = FALSE; |
161 | jpeg_component_info *compptr; |
162 | |
163 | if (cinfo->global_state != DSTATE_SCANNING || cinfo->output_scanline != 0) |
164 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
165 | |
166 | if (!xoffset || !width) |
167 | ERREXIT(cinfo, JERR_BAD_CROP_SPEC); |
168 | |
169 | /* xoffset and width must fall within the output image dimensions. */ |
170 | if (*width == 0 || *xoffset + *width > cinfo->output_width) |
171 | ERREXIT(cinfo, JERR_WIDTH_OVERFLOW); |
172 | |
173 | /* No need to do anything if the caller wants the entire width. */ |
174 | if (*width == cinfo->output_width) |
175 | return; |
176 | |
177 | /* Ensuring the proper alignment of xoffset is tricky. At minimum, it |
178 | * must align with an MCU boundary, because: |
179 | * |
180 | * (1) The IDCT is performed in blocks, and it is not feasible to modify |
181 | * the algorithm so that it can transform partial blocks. |
182 | * (2) Because of the SIMD extensions, any input buffer passed to the |
183 | * upsampling and color conversion routines must be aligned to the |
184 | * SIMD word size (for instance, 128-bit in the case of SSE2.) The |
185 | * easiest way to accomplish this without copying data is to ensure |
186 | * that upsampling and color conversion begin at the start of the |
187 | * first MCU column that will be inverse transformed. |
188 | * |
189 | * In practice, we actually impose a stricter alignment requirement. We |
190 | * require that xoffset be a multiple of the maximum MCU column width of all |
191 | * of the components (the "iMCU column width.") This is to simplify the |
192 | * single-pass decompression case, allowing us to use the same MCU column |
193 | * width for all of the components. |
194 | */ |
195 | if (cinfo->comps_in_scan == 1 && cinfo->num_components == 1) |
196 | align = cinfo->_min_DCT_scaled_size; |
197 | else |
198 | align = cinfo->_min_DCT_scaled_size * cinfo->max_h_samp_factor; |
199 | |
200 | /* Adjust xoffset to the nearest iMCU boundary <= the requested value */ |
201 | input_xoffset = *xoffset; |
202 | *xoffset = (input_xoffset / align) * align; |
203 | |
204 | /* Adjust the width so that the right edge of the output image is as |
205 | * requested (only the left edge is altered.) It is important that calling |
206 | * programs check this value after this function returns, so that they can |
207 | * allocate an output buffer with the appropriate size. |
208 | */ |
209 | *width = *width + input_xoffset - *xoffset; |
210 | cinfo->output_width = *width; |
211 | |
212 | /* Set the first and last iMCU columns that we must decompress. These values |
213 | * will be used in single-scan decompressions. |
214 | */ |
215 | cinfo->master->first_iMCU_col = (JDIMENSION)(long)(*xoffset) / (long)align; |
216 | cinfo->master->last_iMCU_col = |
217 | (JDIMENSION)jdiv_round_up((long)(*xoffset + cinfo->output_width), |
218 | (long)align) - 1; |
219 | |
220 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |
221 | ci++, compptr++) { |
222 | int hsf = (cinfo->comps_in_scan == 1 && cinfo->num_components == 1) ? |
223 | 1 : compptr->h_samp_factor; |
224 | |
225 | /* Set downsampled_width to the new output width. */ |
226 | orig_downsampled_width = compptr->downsampled_width; |
227 | compptr->downsampled_width = |
228 | (JDIMENSION)jdiv_round_up((long)(cinfo->output_width * |
229 | compptr->h_samp_factor), |
230 | (long)cinfo->max_h_samp_factor); |
231 | if (compptr->downsampled_width < 2 && orig_downsampled_width >= 2) |
232 | reinit_upsampler = TRUE; |
233 | |
234 | /* Set the first and last iMCU columns that we must decompress. These |
235 | * values will be used in multi-scan decompressions. |
236 | */ |
237 | cinfo->master->first_MCU_col[ci] = |
238 | (JDIMENSION)(long)(*xoffset * hsf) / (long)align; |
239 | cinfo->master->last_MCU_col[ci] = |
240 | (JDIMENSION)jdiv_round_up((long)((*xoffset + cinfo->output_width) * hsf), |
241 | (long)align) - 1; |
242 | } |
243 | |
244 | if (reinit_upsampler) { |
245 | cinfo->master->jinit_upsampler_no_alloc = TRUE; |
246 | jinit_upsampler(cinfo); |
247 | cinfo->master->jinit_upsampler_no_alloc = FALSE; |
248 | } |
249 | } |
250 | |
251 | |
252 | /* |
253 | * Read some scanlines of data from the JPEG decompressor. |
254 | * |
255 | * The return value will be the number of lines actually read. |
256 | * This may be less than the number requested in several cases, |
257 | * including bottom of image, data source suspension, and operating |
258 | * modes that emit multiple scanlines at a time. |
259 | * |
260 | * Note: we warn about excess calls to jpeg_read_scanlines() since |
261 | * this likely signals an application programmer error. However, |
262 | * an oversize buffer (max_lines > scanlines remaining) is not an error. |
263 | */ |
264 | |
265 | GLOBAL(JDIMENSION) |
266 | jpeg_read_scanlines(j_decompress_ptr cinfo, JSAMPARRAY scanlines, |
267 | JDIMENSION max_lines) |
268 | { |
269 | JDIMENSION row_ctr; |
270 | |
271 | if (cinfo->global_state != DSTATE_SCANNING) |
272 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
273 | if (cinfo->output_scanline >= cinfo->output_height) { |
274 | WARNMS(cinfo, JWRN_TOO_MUCH_DATA); |
275 | return 0; |
276 | } |
277 | |
278 | /* Call progress monitor hook if present */ |
279 | if (cinfo->progress != NULL) { |
280 | cinfo->progress->pass_counter = (long)cinfo->output_scanline; |
281 | cinfo->progress->pass_limit = (long)cinfo->output_height; |
282 | (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
283 | } |
284 | |
285 | /* Process some data */ |
286 | row_ctr = 0; |
287 | (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines); |
288 | cinfo->output_scanline += row_ctr; |
289 | return row_ctr; |
290 | } |
291 | |
292 | |
293 | /* Dummy color convert function used by jpeg_skip_scanlines() */ |
294 | LOCAL(void) |
295 | noop_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf, |
296 | JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows) |
297 | { |
298 | } |
299 | |
300 | |
301 | /* Dummy quantize function used by jpeg_skip_scanlines() */ |
302 | LOCAL(void) |
303 | noop_quantize(j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
304 | JSAMPARRAY output_buf, int num_rows) |
305 | { |
306 | } |
307 | |
308 | |
309 | /* |
310 | * In some cases, it is best to call jpeg_read_scanlines() and discard the |
311 | * output, rather than skipping the scanlines, because this allows us to |
312 | * maintain the internal state of the context-based upsampler. In these cases, |
313 | * we set up and tear down a dummy color converter in order to avoid valgrind |
314 | * errors and to achieve the best possible performance. |
315 | */ |
316 | |
317 | LOCAL(void) |
318 | read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines) |
319 | { |
320 | JDIMENSION n; |
321 | my_master_ptr master = (my_master_ptr)cinfo->master; |
322 | JSAMPLE dummy_sample[1] = { 0 }; |
323 | JSAMPROW dummy_row = dummy_sample; |
324 | JSAMPARRAY scanlines = NULL; |
325 | void (*color_convert) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf, |
326 | JDIMENSION input_row, JSAMPARRAY output_buf, |
327 | int num_rows) = NULL; |
328 | void (*color_quantize) (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |
329 | JSAMPARRAY output_buf, int num_rows) = NULL; |
330 | |
331 | if (cinfo->cconvert && cinfo->cconvert->color_convert) { |
332 | color_convert = cinfo->cconvert->color_convert; |
333 | cinfo->cconvert->color_convert = noop_convert; |
334 | /* This just prevents UBSan from complaining about adding 0 to a NULL |
335 | * pointer. The pointer isn't actually used. |
336 | */ |
337 | scanlines = &dummy_row; |
338 | } |
339 | |
340 | if (cinfo->cquantize && cinfo->cquantize->color_quantize) { |
341 | color_quantize = cinfo->cquantize->color_quantize; |
342 | cinfo->cquantize->color_quantize = noop_quantize; |
343 | } |
344 | |
345 | if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) { |
346 | my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample; |
347 | scanlines = &upsample->spare_row; |
348 | } |
349 | |
350 | for (n = 0; n < num_lines; n++) |
351 | jpeg_read_scanlines(cinfo, scanlines, 1); |
352 | |
353 | if (color_convert) |
354 | cinfo->cconvert->color_convert = color_convert; |
355 | |
356 | if (color_quantize) |
357 | cinfo->cquantize->color_quantize = color_quantize; |
358 | } |
359 | |
360 | |
361 | /* |
362 | * Called by jpeg_skip_scanlines(). This partially skips a decompress block by |
363 | * incrementing the rowgroup counter. |
364 | */ |
365 | |
366 | LOCAL(void) |
367 | increment_simple_rowgroup_ctr(j_decompress_ptr cinfo, JDIMENSION rows) |
368 | { |
369 | JDIMENSION rows_left; |
370 | my_main_ptr main_ptr = (my_main_ptr)cinfo->main; |
371 | my_master_ptr master = (my_master_ptr)cinfo->master; |
372 | |
373 | if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) { |
374 | read_and_discard_scanlines(cinfo, rows); |
375 | return; |
376 | } |
377 | |
378 | /* Increment the counter to the next row group after the skipped rows. */ |
379 | main_ptr->rowgroup_ctr += rows / cinfo->max_v_samp_factor; |
380 | |
381 | /* Partially skipping a row group would involve modifying the internal state |
382 | * of the upsampler, so read the remaining rows into a dummy buffer instead. |
383 | */ |
384 | rows_left = rows % cinfo->max_v_samp_factor; |
385 | cinfo->output_scanline += rows - rows_left; |
386 | |
387 | read_and_discard_scanlines(cinfo, rows_left); |
388 | } |
389 | |
390 | /* |
391 | * Skips some scanlines of data from the JPEG decompressor. |
392 | * |
393 | * The return value will be the number of lines actually skipped. If skipping |
394 | * num_lines would move beyond the end of the image, then the actual number of |
395 | * lines remaining in the image is returned. Otherwise, the return value will |
396 | * be equal to num_lines. |
397 | * |
398 | * Refer to libjpeg.txt for more information. |
399 | */ |
400 | |
401 | GLOBAL(JDIMENSION) |
402 | jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines) |
403 | { |
404 | my_main_ptr main_ptr = (my_main_ptr)cinfo->main; |
405 | my_coef_ptr coef = (my_coef_ptr)cinfo->coef; |
406 | my_master_ptr master = (my_master_ptr)cinfo->master; |
407 | my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample; |
408 | JDIMENSION i, x; |
409 | int y; |
410 | JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row; |
411 | JDIMENSION lines_to_skip, lines_to_read; |
412 | |
413 | /* Two-pass color quantization is not supported. */ |
414 | if (cinfo->quantize_colors && cinfo->two_pass_quantize) |
415 | ERREXIT(cinfo, JERR_NOTIMPL); |
416 | |
417 | if (cinfo->global_state != DSTATE_SCANNING) |
418 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
419 | |
420 | /* Do not skip past the bottom of the image. */ |
421 | if (cinfo->output_scanline + num_lines >= cinfo->output_height) { |
422 | num_lines = cinfo->output_height - cinfo->output_scanline; |
423 | cinfo->output_scanline = cinfo->output_height; |
424 | (*cinfo->inputctl->finish_input_pass) (cinfo); |
425 | cinfo->inputctl->eoi_reached = TRUE; |
426 | return num_lines; |
427 | } |
428 | |
429 | if (num_lines == 0) |
430 | return 0; |
431 | |
432 | lines_per_iMCU_row = cinfo->_min_DCT_scaled_size * cinfo->max_v_samp_factor; |
433 | lines_left_in_iMCU_row = |
434 | (lines_per_iMCU_row - (cinfo->output_scanline % lines_per_iMCU_row)) % |
435 | lines_per_iMCU_row; |
436 | lines_after_iMCU_row = num_lines - lines_left_in_iMCU_row; |
437 | |
438 | /* Skip the lines remaining in the current iMCU row. When upsampling |
439 | * requires context rows, we need the previous and next rows in order to read |
440 | * the current row. This adds some complexity. |
441 | */ |
442 | if (cinfo->upsample->need_context_rows) { |
443 | /* If the skipped lines would not move us past the current iMCU row, we |
444 | * read the lines and ignore them. There might be a faster way of doing |
445 | * this, but we are facing increasing complexity for diminishing returns. |
446 | * The increasing complexity would be a by-product of meddling with the |
447 | * state machine used to skip context rows. Near the end of an iMCU row, |
448 | * the next iMCU row may have already been entropy-decoded. In this unique |
449 | * case, we will read the next iMCU row if we cannot skip past it as well. |
450 | */ |
451 | if ((num_lines < lines_left_in_iMCU_row + 1) || |
452 | (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full && |
453 | lines_after_iMCU_row < lines_per_iMCU_row + 1)) { |
454 | read_and_discard_scanlines(cinfo, num_lines); |
455 | return num_lines; |
456 | } |
457 | |
458 | /* If the next iMCU row has already been entropy-decoded, make sure that |
459 | * we do not skip too far. |
460 | */ |
461 | if (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full) { |
462 | cinfo->output_scanline += lines_left_in_iMCU_row + lines_per_iMCU_row; |
463 | lines_after_iMCU_row -= lines_per_iMCU_row; |
464 | } else { |
465 | cinfo->output_scanline += lines_left_in_iMCU_row; |
466 | } |
467 | |
468 | /* If we have just completed the first block, adjust the buffer pointers */ |
469 | if (main_ptr->iMCU_row_ctr == 0 || |
470 | (main_ptr->iMCU_row_ctr == 1 && lines_left_in_iMCU_row > 2)) |
471 | set_wraparound_pointers(cinfo); |
472 | main_ptr->buffer_full = FALSE; |
473 | main_ptr->rowgroup_ctr = 0; |
474 | main_ptr->context_state = CTX_PREPARE_FOR_IMCU; |
475 | if (!master->using_merged_upsample) { |
476 | upsample->next_row_out = cinfo->max_v_samp_factor; |
477 | upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
478 | } |
479 | } |
480 | |
481 | /* Skipping is much simpler when context rows are not required. */ |
482 | else { |
483 | if (num_lines < lines_left_in_iMCU_row) { |
484 | increment_simple_rowgroup_ctr(cinfo, num_lines); |
485 | return num_lines; |
486 | } else { |
487 | cinfo->output_scanline += lines_left_in_iMCU_row; |
488 | main_ptr->buffer_full = FALSE; |
489 | main_ptr->rowgroup_ctr = 0; |
490 | if (!master->using_merged_upsample) { |
491 | upsample->next_row_out = cinfo->max_v_samp_factor; |
492 | upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
493 | } |
494 | } |
495 | } |
496 | |
497 | /* Calculate how many full iMCU rows we can skip. */ |
498 | if (cinfo->upsample->need_context_rows) |
499 | lines_to_skip = ((lines_after_iMCU_row - 1) / lines_per_iMCU_row) * |
500 | lines_per_iMCU_row; |
501 | else |
502 | lines_to_skip = (lines_after_iMCU_row / lines_per_iMCU_row) * |
503 | lines_per_iMCU_row; |
504 | /* Calculate the number of lines that remain to be skipped after skipping all |
505 | * of the full iMCU rows that we can. We will not read these lines unless we |
506 | * have to. |
507 | */ |
508 | lines_to_read = lines_after_iMCU_row - lines_to_skip; |
509 | |
510 | /* For images requiring multiple scans (progressive, non-interleaved, etc.), |
511 | * all of the entropy decoding occurs in jpeg_start_decompress(), assuming |
512 | * that the input data source is non-suspending. This makes skipping easy. |
513 | */ |
514 | if (cinfo->inputctl->has_multiple_scans) { |
515 | if (cinfo->upsample->need_context_rows) { |
516 | cinfo->output_scanline += lines_to_skip; |
517 | cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row; |
518 | main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row; |
519 | /* It is complex to properly move to the middle of a context block, so |
520 | * read the remaining lines instead of skipping them. |
521 | */ |
522 | read_and_discard_scanlines(cinfo, lines_to_read); |
523 | } else { |
524 | cinfo->output_scanline += lines_to_skip; |
525 | cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row; |
526 | increment_simple_rowgroup_ctr(cinfo, lines_to_read); |
527 | } |
528 | if (!master->using_merged_upsample) |
529 | upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
530 | return num_lines; |
531 | } |
532 | |
533 | /* Skip the iMCU rows that we can safely skip. */ |
534 | for (i = 0; i < lines_to_skip; i += lines_per_iMCU_row) { |
535 | for (y = 0; y < coef->MCU_rows_per_iMCU_row; y++) { |
536 | for (x = 0; x < cinfo->MCUs_per_row; x++) { |
537 | /* Calling decode_mcu() with a NULL pointer causes it to discard the |
538 | * decoded coefficients. This is ~5% faster for large subsets, but |
539 | * it's tough to tell a difference for smaller images. |
540 | */ |
541 | if (!cinfo->entropy->insufficient_data) |
542 | cinfo->master->last_good_iMCU_row = cinfo->input_iMCU_row; |
543 | (*cinfo->entropy->decode_mcu) (cinfo, NULL); |
544 | } |
545 | } |
546 | cinfo->input_iMCU_row++; |
547 | cinfo->output_iMCU_row++; |
548 | if (cinfo->input_iMCU_row < cinfo->total_iMCU_rows) |
549 | start_iMCU_row(cinfo); |
550 | else |
551 | (*cinfo->inputctl->finish_input_pass) (cinfo); |
552 | } |
553 | cinfo->output_scanline += lines_to_skip; |
554 | |
555 | if (cinfo->upsample->need_context_rows) { |
556 | /* Context-based upsampling keeps track of iMCU rows. */ |
557 | main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row; |
558 | |
559 | /* It is complex to properly move to the middle of a context block, so |
560 | * read the remaining lines instead of skipping them. |
561 | */ |
562 | read_and_discard_scanlines(cinfo, lines_to_read); |
563 | } else { |
564 | increment_simple_rowgroup_ctr(cinfo, lines_to_read); |
565 | } |
566 | |
567 | /* Since skipping lines involves skipping the upsampling step, the value of |
568 | * "rows_to_go" will become invalid unless we set it here. NOTE: This is a |
569 | * bit odd, since "rows_to_go" seems to be redundantly keeping track of |
570 | * output_scanline. |
571 | */ |
572 | if (!master->using_merged_upsample) |
573 | upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline; |
574 | |
575 | /* Always skip the requested number of lines. */ |
576 | return num_lines; |
577 | } |
578 | |
579 | /* |
580 | * Alternate entry point to read raw data. |
581 | * Processes exactly one iMCU row per call, unless suspended. |
582 | */ |
583 | |
584 | GLOBAL(JDIMENSION) |
585 | jpeg_read_raw_data(j_decompress_ptr cinfo, JSAMPIMAGE data, |
586 | JDIMENSION max_lines) |
587 | { |
588 | JDIMENSION lines_per_iMCU_row; |
589 | |
590 | if (cinfo->global_state != DSTATE_RAW_OK) |
591 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
592 | if (cinfo->output_scanline >= cinfo->output_height) { |
593 | WARNMS(cinfo, JWRN_TOO_MUCH_DATA); |
594 | return 0; |
595 | } |
596 | |
597 | /* Call progress monitor hook if present */ |
598 | if (cinfo->progress != NULL) { |
599 | cinfo->progress->pass_counter = (long)cinfo->output_scanline; |
600 | cinfo->progress->pass_limit = (long)cinfo->output_height; |
601 | (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo); |
602 | } |
603 | |
604 | /* Verify that at least one iMCU row can be returned. */ |
605 | lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size; |
606 | if (max_lines < lines_per_iMCU_row) |
607 | ERREXIT(cinfo, JERR_BUFFER_SIZE); |
608 | |
609 | /* Decompress directly into user's buffer. */ |
610 | if (!(*cinfo->coef->decompress_data) (cinfo, data)) |
611 | return 0; /* suspension forced, can do nothing more */ |
612 | |
613 | /* OK, we processed one iMCU row. */ |
614 | cinfo->output_scanline += lines_per_iMCU_row; |
615 | return lines_per_iMCU_row; |
616 | } |
617 | |
618 | |
619 | /* Additional entry points for buffered-image mode. */ |
620 | |
621 | #ifdef D_MULTISCAN_FILES_SUPPORTED |
622 | |
623 | /* |
624 | * Initialize for an output pass in buffered-image mode. |
625 | */ |
626 | |
627 | GLOBAL(boolean) |
628 | jpeg_start_output(j_decompress_ptr cinfo, int scan_number) |
629 | { |
630 | if (cinfo->global_state != DSTATE_BUFIMAGE && |
631 | cinfo->global_state != DSTATE_PRESCAN) |
632 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
633 | /* Limit scan number to valid range */ |
634 | if (scan_number <= 0) |
635 | scan_number = 1; |
636 | if (cinfo->inputctl->eoi_reached && scan_number > cinfo->input_scan_number) |
637 | scan_number = cinfo->input_scan_number; |
638 | cinfo->output_scan_number = scan_number; |
639 | /* Perform any dummy output passes, and set up for the real pass */ |
640 | return output_pass_setup(cinfo); |
641 | } |
642 | |
643 | |
644 | /* |
645 | * Finish up after an output pass in buffered-image mode. |
646 | * |
647 | * Returns FALSE if suspended. The return value need be inspected only if |
648 | * a suspending data source is used. |
649 | */ |
650 | |
651 | GLOBAL(boolean) |
652 | jpeg_finish_output(j_decompress_ptr cinfo) |
653 | { |
654 | if ((cinfo->global_state == DSTATE_SCANNING || |
655 | cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) { |
656 | /* Terminate this pass. */ |
657 | /* We do not require the whole pass to have been completed. */ |
658 | (*cinfo->master->finish_output_pass) (cinfo); |
659 | cinfo->global_state = DSTATE_BUFPOST; |
660 | } else if (cinfo->global_state != DSTATE_BUFPOST) { |
661 | /* BUFPOST = repeat call after a suspension, anything else is error */ |
662 | ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); |
663 | } |
664 | /* Read markers looking for SOS or EOI */ |
665 | while (cinfo->input_scan_number <= cinfo->output_scan_number && |
666 | !cinfo->inputctl->eoi_reached) { |
667 | if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED) |
668 | return FALSE; /* Suspend, come back later */ |
669 | } |
670 | cinfo->global_state = DSTATE_BUFIMAGE; |
671 | return TRUE; |
672 | } |
673 | |
674 | #endif /* D_MULTISCAN_FILES_SUPPORTED */ |
675 | |