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1
2/* pngread.c - read a PNG file
3 *
4 * Copyright (c) 2018-2019 Cosmin Truta
5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6 * Copyright (c) 1996-1997 Andreas Dilger
7 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
8 *
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
12 *
13 * This file contains routines that an application calls directly to
14 * read a PNG file or stream.
15 */
16
17#include "pngpriv.h"
18#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
19# include <errno.h>
20#endif
21
22#ifdef PNG_READ_SUPPORTED
23
24/* Create a PNG structure for reading, and allocate any memory needed. */
25PNG_FUNCTION(png_structp,PNGAPI
26png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
28{
29#ifndef PNG_USER_MEM_SUPPORTED
30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
31 error_fn, warn_fn, NULL, NULL, NULL);
32#else
33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
34 warn_fn, NULL, NULL, NULL);
35}
36
37/* Alternate create PNG structure for reading, and allocate any memory
38 * needed.
39 */
40PNG_FUNCTION(png_structp,PNGAPI
41png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
44{
45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
47#endif /* USER_MEM */
48
49 if (png_ptr != NULL)
50 {
51 png_ptr->mode = PNG_IS_READ_STRUCT;
52
53 /* Added in libpng-1.6.0; this can be used to detect a read structure if
54 * required (it will be zero in a write structure.)
55 */
56# ifdef PNG_SEQUENTIAL_READ_SUPPORTED
57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
58# endif
59
60# ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
62
63 /* In stable builds only warn if an application error can be completely
64 * handled.
65 */
66# if PNG_RELEASE_BUILD
67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
68# endif
69# endif
70
71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
72 * do it itself) avoiding setting the default function if it is not
73 * required.
74 */
75 png_set_read_fn(png_ptr, NULL, NULL);
76 }
77
78 return png_ptr;
79}
80
81
82#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83/* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
90 */
91void PNGAPI
92png_read_info(png_structrp png_ptr, png_inforp info_ptr)
93{
94#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
95 int keep;
96#endif
97
98 png_debug(1, "in png_read_info");
99
100 if (png_ptr == NULL || info_ptr == NULL)
101 return;
102
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr, info_ptr);
105
106 for (;;)
107 {
108 png_uint_32 length = png_read_chunk_header(png_ptr);
109 png_uint_32 chunk_name = png_ptr->chunk_name;
110
111 /* IDAT logic needs to happen here to simplify getting the two flags
112 * right.
113 */
114 if (chunk_name == png_IDAT)
115 {
116 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
117 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
118
119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
120 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
121 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
122
123 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
124 png_chunk_benign_error(png_ptr, "Too many IDATs found");
125
126 png_ptr->mode |= PNG_HAVE_IDAT;
127 }
128
129 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
130 {
131 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
132 png_ptr->mode |= PNG_AFTER_IDAT;
133 }
134
135 /* This should be a binary subdivision search or a hash for
136 * matching the chunk name rather than a linear search.
137 */
138 if (chunk_name == png_IHDR)
139 png_handle_IHDR(png_ptr, info_ptr, length);
140
141 else if (chunk_name == png_IEND)
142 png_handle_IEND(png_ptr, info_ptr, length);
143
144#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
145 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
146 {
147 png_handle_unknown(png_ptr, info_ptr, length, keep);
148
149 if (chunk_name == png_PLTE)
150 png_ptr->mode |= PNG_HAVE_PLTE;
151
152 else if (chunk_name == png_IDAT)
153 {
154 png_ptr->idat_size = 0; /* It has been consumed */
155 break;
156 }
157 }
158#endif
159 else if (chunk_name == png_PLTE)
160 png_handle_PLTE(png_ptr, info_ptr, length);
161
162 else if (chunk_name == png_IDAT)
163 {
164 png_ptr->idat_size = length;
165 break;
166 }
167
168#ifdef PNG_READ_bKGD_SUPPORTED
169 else if (chunk_name == png_bKGD)
170 png_handle_bKGD(png_ptr, info_ptr, length);
171#endif
172
173#ifdef PNG_READ_cHRM_SUPPORTED
174 else if (chunk_name == png_cHRM)
175 png_handle_cHRM(png_ptr, info_ptr, length);
176#endif
177
178#ifdef PNG_READ_eXIf_SUPPORTED
179 else if (chunk_name == png_eXIf)
180 png_handle_eXIf(png_ptr, info_ptr, length);
181#endif
182
183#ifdef PNG_READ_gAMA_SUPPORTED
184 else if (chunk_name == png_gAMA)
185 png_handle_gAMA(png_ptr, info_ptr, length);
186#endif
187
188#ifdef PNG_READ_hIST_SUPPORTED
189 else if (chunk_name == png_hIST)
190 png_handle_hIST(png_ptr, info_ptr, length);
191#endif
192
193#ifdef PNG_READ_oFFs_SUPPORTED
194 else if (chunk_name == png_oFFs)
195 png_handle_oFFs(png_ptr, info_ptr, length);
196#endif
197
198#ifdef PNG_READ_pCAL_SUPPORTED
199 else if (chunk_name == png_pCAL)
200 png_handle_pCAL(png_ptr, info_ptr, length);
201#endif
202
203#ifdef PNG_READ_sCAL_SUPPORTED
204 else if (chunk_name == png_sCAL)
205 png_handle_sCAL(png_ptr, info_ptr, length);
206#endif
207
208#ifdef PNG_READ_pHYs_SUPPORTED
209 else if (chunk_name == png_pHYs)
210 png_handle_pHYs(png_ptr, info_ptr, length);
211#endif
212
213#ifdef PNG_READ_sBIT_SUPPORTED
214 else if (chunk_name == png_sBIT)
215 png_handle_sBIT(png_ptr, info_ptr, length);
216#endif
217
218#ifdef PNG_READ_sRGB_SUPPORTED
219 else if (chunk_name == png_sRGB)
220 png_handle_sRGB(png_ptr, info_ptr, length);
221#endif
222
223#ifdef PNG_READ_iCCP_SUPPORTED
224 else if (chunk_name == png_iCCP)
225 png_handle_iCCP(png_ptr, info_ptr, length);
226#endif
227
228#ifdef PNG_READ_sPLT_SUPPORTED
229 else if (chunk_name == png_sPLT)
230 png_handle_sPLT(png_ptr, info_ptr, length);
231#endif
232
233#ifdef PNG_READ_tEXt_SUPPORTED
234 else if (chunk_name == png_tEXt)
235 png_handle_tEXt(png_ptr, info_ptr, length);
236#endif
237
238#ifdef PNG_READ_tIME_SUPPORTED
239 else if (chunk_name == png_tIME)
240 png_handle_tIME(png_ptr, info_ptr, length);
241#endif
242
243#ifdef PNG_READ_tRNS_SUPPORTED
244 else if (chunk_name == png_tRNS)
245 png_handle_tRNS(png_ptr, info_ptr, length);
246#endif
247
248#ifdef PNG_READ_zTXt_SUPPORTED
249 else if (chunk_name == png_zTXt)
250 png_handle_zTXt(png_ptr, info_ptr, length);
251#endif
252
253#ifdef PNG_READ_iTXt_SUPPORTED
254 else if (chunk_name == png_iTXt)
255 png_handle_iTXt(png_ptr, info_ptr, length);
256#endif
257
258 else
259 png_handle_unknown(png_ptr, info_ptr, length,
260 PNG_HANDLE_CHUNK_AS_DEFAULT);
261 }
262}
263#endif /* SEQUENTIAL_READ */
264
265/* Optional call to update the users info_ptr structure */
266void PNGAPI
267png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
268{
269 png_debug(1, "in png_read_update_info");
270
271 if (png_ptr != NULL)
272 {
273 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
274 {
275 png_read_start_row(png_ptr);
276
277# ifdef PNG_READ_TRANSFORMS_SUPPORTED
278 png_read_transform_info(png_ptr, info_ptr);
279# else
280 PNG_UNUSED(info_ptr)
281# endif
282 }
283
284 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
285 else
286 png_app_error(png_ptr,
287 "png_read_update_info/png_start_read_image: duplicate call");
288 }
289}
290
291#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
292/* Initialize palette, background, etc, after transformations
293 * are set, but before any reading takes place. This allows
294 * the user to obtain a gamma-corrected palette, for example.
295 * If the user doesn't call this, we will do it ourselves.
296 */
297void PNGAPI
298png_start_read_image(png_structrp png_ptr)
299{
300 png_debug(1, "in png_start_read_image");
301
302 if (png_ptr != NULL)
303 {
304 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
305 png_read_start_row(png_ptr);
306
307 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
308 else
309 png_app_error(png_ptr,
310 "png_start_read_image/png_read_update_info: duplicate call");
311 }
312}
313#endif /* SEQUENTIAL_READ */
314
315#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
316#ifdef PNG_MNG_FEATURES_SUPPORTED
317/* Undoes intrapixel differencing,
318 * NOTE: this is apparently only supported in the 'sequential' reader.
319 */
320static void
321png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
322{
323 png_debug(1, "in png_do_read_intrapixel");
324
325 if (
326 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
327 {
328 int bytes_per_pixel;
329 png_uint_32 row_width = row_info->width;
330
331 if (row_info->bit_depth == 8)
332 {
333 png_bytep rp;
334 png_uint_32 i;
335
336 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
337 bytes_per_pixel = 3;
338
339 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
340 bytes_per_pixel = 4;
341
342 else
343 return;
344
345 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
346 {
347 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
348 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
349 }
350 }
351 else if (row_info->bit_depth == 16)
352 {
353 png_bytep rp;
354 png_uint_32 i;
355
356 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
357 bytes_per_pixel = 6;
358
359 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
360 bytes_per_pixel = 8;
361
362 else
363 return;
364
365 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
366 {
367 png_uint_32 s0 = (png_uint_32)(*(rp ) << 8) | *(rp + 1);
368 png_uint_32 s1 = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
369 png_uint_32 s2 = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
370 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
371 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
372 *(rp ) = (png_byte)((red >> 8) & 0xff);
373 *(rp + 1) = (png_byte)(red & 0xff);
374 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
375 *(rp + 5) = (png_byte)(blue & 0xff);
376 }
377 }
378 }
379}
380#endif /* MNG_FEATURES */
381
382void PNGAPI
383png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
384{
385 png_row_info row_info;
386
387 if (png_ptr == NULL)
388 return;
389
390 png_debug2(1, "in png_read_row (row %lu, pass %d)",
391 (unsigned long)png_ptr->row_number, png_ptr->pass);
392
393 /* png_read_start_row sets the information (in particular iwidth) for this
394 * interlace pass.
395 */
396 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
397 png_read_start_row(png_ptr);
398
399 /* 1.5.6: row_info moved out of png_struct to a local here. */
400 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
401 row_info.color_type = png_ptr->color_type;
402 row_info.bit_depth = png_ptr->bit_depth;
403 row_info.channels = png_ptr->channels;
404 row_info.pixel_depth = png_ptr->pixel_depth;
405 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
406
407#ifdef PNG_WARNINGS_SUPPORTED
408 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
409 {
410 /* Check for transforms that have been set but were defined out */
411#if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
412 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
413 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
414#endif
415
416#if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
417 if ((png_ptr->transformations & PNG_FILLER) != 0)
418 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
419#endif
420
421#if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
422 !defined(PNG_READ_PACKSWAP_SUPPORTED)
423 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
424 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
425#endif
426
427#if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
428 if ((png_ptr->transformations & PNG_PACK) != 0)
429 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
430#endif
431
432#if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
433 if ((png_ptr->transformations & PNG_SHIFT) != 0)
434 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
435#endif
436
437#if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
438 if ((png_ptr->transformations & PNG_BGR) != 0)
439 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
440#endif
441
442#if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
443 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
444 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
445#endif
446 }
447#endif /* WARNINGS */
448
449#ifdef PNG_READ_INTERLACING_SUPPORTED
450 /* If interlaced and we do not need a new row, combine row and return.
451 * Notice that the pixels we have from previous rows have been transformed
452 * already; we can only combine like with like (transformed or
453 * untransformed) and, because of the libpng API for interlaced images, this
454 * means we must transform before de-interlacing.
455 */
456 if (png_ptr->interlaced != 0 &&
457 (png_ptr->transformations & PNG_INTERLACE) != 0)
458 {
459 switch (png_ptr->pass)
460 {
461 case 0:
462 if (png_ptr->row_number & 0x07)
463 {
464 if (dsp_row != NULL)
465 png_combine_row(png_ptr, dsp_row, 1/*display*/);
466 png_read_finish_row(png_ptr);
467 return;
468 }
469 break;
470
471 case 1:
472 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
473 {
474 if (dsp_row != NULL)
475 png_combine_row(png_ptr, dsp_row, 1/*display*/);
476
477 png_read_finish_row(png_ptr);
478 return;
479 }
480 break;
481
482 case 2:
483 if ((png_ptr->row_number & 0x07) != 4)
484 {
485 if (dsp_row != NULL && (png_ptr->row_number & 4))
486 png_combine_row(png_ptr, dsp_row, 1/*display*/);
487
488 png_read_finish_row(png_ptr);
489 return;
490 }
491 break;
492
493 case 3:
494 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
495 {
496 if (dsp_row != NULL)
497 png_combine_row(png_ptr, dsp_row, 1/*display*/);
498
499 png_read_finish_row(png_ptr);
500 return;
501 }
502 break;
503
504 case 4:
505 if ((png_ptr->row_number & 3) != 2)
506 {
507 if (dsp_row != NULL && (png_ptr->row_number & 2))
508 png_combine_row(png_ptr, dsp_row, 1/*display*/);
509
510 png_read_finish_row(png_ptr);
511 return;
512 }
513 break;
514
515 case 5:
516 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
517 {
518 if (dsp_row != NULL)
519 png_combine_row(png_ptr, dsp_row, 1/*display*/);
520
521 png_read_finish_row(png_ptr);
522 return;
523 }
524 break;
525
526 default:
527 case 6:
528 if ((png_ptr->row_number & 1) == 0)
529 {
530 png_read_finish_row(png_ptr);
531 return;
532 }
533 break;
534 }
535 }
536#endif
537
538 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
539 png_error(png_ptr, "Invalid attempt to read row data");
540
541 /* Fill the row with IDAT data: */
542 png_ptr->row_buf[0]=255; /* to force error if no data was found */
543 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
544
545 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
546 {
547 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
548 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
549 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
550 else
551 png_error(png_ptr, "bad adaptive filter value");
552 }
553
554 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
555 * 1.5.6, while the buffer really is this big in current versions of libpng
556 * it may not be in the future, so this was changed just to copy the
557 * interlaced count:
558 */
559 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
560
561#ifdef PNG_MNG_FEATURES_SUPPORTED
562 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
563 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
564 {
565 /* Intrapixel differencing */
566 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
567 }
568#endif
569
570#ifdef PNG_READ_TRANSFORMS_SUPPORTED
571 if (png_ptr->transformations)
572 png_do_read_transformations(png_ptr, &row_info);
573#endif
574
575 /* The transformed pixel depth should match the depth now in row_info. */
576 if (png_ptr->transformed_pixel_depth == 0)
577 {
578 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
579 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
580 png_error(png_ptr, "sequential row overflow");
581 }
582
583 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
584 png_error(png_ptr, "internal sequential row size calculation error");
585
586#ifdef PNG_READ_INTERLACING_SUPPORTED
587 /* Expand interlaced rows to full size */
588 if (png_ptr->interlaced != 0 &&
589 (png_ptr->transformations & PNG_INTERLACE) != 0)
590 {
591 if (png_ptr->pass < 6)
592 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
593 png_ptr->transformations);
594
595 if (dsp_row != NULL)
596 png_combine_row(png_ptr, dsp_row, 1/*display*/);
597
598 if (row != NULL)
599 png_combine_row(png_ptr, row, 0/*row*/);
600 }
601
602 else
603#endif
604 {
605 if (row != NULL)
606 png_combine_row(png_ptr, row, -1/*ignored*/);
607
608 if (dsp_row != NULL)
609 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
610 }
611 png_read_finish_row(png_ptr);
612
613 if (png_ptr->read_row_fn != NULL)
614 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
615
616}
617#endif /* SEQUENTIAL_READ */
618
619#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
620/* Read one or more rows of image data. If the image is interlaced,
621 * and png_set_interlace_handling() has been called, the rows need to
622 * contain the contents of the rows from the previous pass. If the
623 * image has alpha or transparency, and png_handle_alpha()[*] has been
624 * called, the rows contents must be initialized to the contents of the
625 * screen.
626 *
627 * "row" holds the actual image, and pixels are placed in it
628 * as they arrive. If the image is displayed after each pass, it will
629 * appear to "sparkle" in. "display_row" can be used to display a
630 * "chunky" progressive image, with finer detail added as it becomes
631 * available. If you do not want this "chunky" display, you may pass
632 * NULL for display_row. If you do not want the sparkle display, and
633 * you have not called png_handle_alpha(), you may pass NULL for rows.
634 * If you have called png_handle_alpha(), and the image has either an
635 * alpha channel or a transparency chunk, you must provide a buffer for
636 * rows. In this case, you do not have to provide a display_row buffer
637 * also, but you may. If the image is not interlaced, or if you have
638 * not called png_set_interlace_handling(), the display_row buffer will
639 * be ignored, so pass NULL to it.
640 *
641 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
642 */
643
644void PNGAPI
645png_read_rows(png_structrp png_ptr, png_bytepp row,
646 png_bytepp display_row, png_uint_32 num_rows)
647{
648 png_uint_32 i;
649 png_bytepp rp;
650 png_bytepp dp;
651
652 png_debug(1, "in png_read_rows");
653
654 if (png_ptr == NULL)
655 return;
656
657 rp = row;
658 dp = display_row;
659 if (rp != NULL && dp != NULL)
660 for (i = 0; i < num_rows; i++)
661 {
662 png_bytep rptr = *rp++;
663 png_bytep dptr = *dp++;
664
665 png_read_row(png_ptr, rptr, dptr);
666 }
667
668 else if (rp != NULL)
669 for (i = 0; i < num_rows; i++)
670 {
671 png_bytep rptr = *rp;
672 png_read_row(png_ptr, rptr, NULL);
673 rp++;
674 }
675
676 else if (dp != NULL)
677 for (i = 0; i < num_rows; i++)
678 {
679 png_bytep dptr = *dp;
680 png_read_row(png_ptr, NULL, dptr);
681 dp++;
682 }
683}
684#endif /* SEQUENTIAL_READ */
685
686#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
687/* Read the entire image. If the image has an alpha channel or a tRNS
688 * chunk, and you have called png_handle_alpha()[*], you will need to
689 * initialize the image to the current image that PNG will be overlaying.
690 * We set the num_rows again here, in case it was incorrectly set in
691 * png_read_start_row() by a call to png_read_update_info() or
692 * png_start_read_image() if png_set_interlace_handling() wasn't called
693 * prior to either of these functions like it should have been. You can
694 * only call this function once. If you desire to have an image for
695 * each pass of a interlaced image, use png_read_rows() instead.
696 *
697 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
698 */
699void PNGAPI
700png_read_image(png_structrp png_ptr, png_bytepp image)
701{
702 png_uint_32 i, image_height;
703 int pass, j;
704 png_bytepp rp;
705
706 png_debug(1, "in png_read_image");
707
708 if (png_ptr == NULL)
709 return;
710
711#ifdef PNG_READ_INTERLACING_SUPPORTED
712 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
713 {
714 pass = png_set_interlace_handling(png_ptr);
715 /* And make sure transforms are initialized. */
716 png_start_read_image(png_ptr);
717 }
718 else
719 {
720 if (png_ptr->interlaced != 0 &&
721 (png_ptr->transformations & PNG_INTERLACE) == 0)
722 {
723 /* Caller called png_start_read_image or png_read_update_info without
724 * first turning on the PNG_INTERLACE transform. We can fix this here,
725 * but the caller should do it!
726 */
727 png_warning(png_ptr, "Interlace handling should be turned on when "
728 "using png_read_image");
729 /* Make sure this is set correctly */
730 png_ptr->num_rows = png_ptr->height;
731 }
732
733 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
734 * the above error case.
735 */
736 pass = png_set_interlace_handling(png_ptr);
737 }
738#else
739 if (png_ptr->interlaced)
740 png_error(png_ptr,
741 "Cannot read interlaced image -- interlace handler disabled");
742
743 pass = 1;
744#endif
745
746 image_height=png_ptr->height;
747
748 for (j = 0; j < pass; j++)
749 {
750 rp = image;
751 for (i = 0; i < image_height; i++)
752 {
753 png_read_row(png_ptr, *rp, NULL);
754 rp++;
755 }
756 }
757}
758#endif /* SEQUENTIAL_READ */
759
760#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
761/* Read the end of the PNG file. Will not read past the end of the
762 * file, will verify the end is accurate, and will read any comments
763 * or time information at the end of the file, if info is not NULL.
764 */
765void PNGAPI
766png_read_end(png_structrp png_ptr, png_inforp info_ptr)
767{
768#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
769 int keep;
770#endif
771
772 png_debug(1, "in png_read_end");
773
774 if (png_ptr == NULL)
775 return;
776
777 /* If png_read_end is called in the middle of reading the rows there may
778 * still be pending IDAT data and an owned zstream. Deal with this here.
779 */
780#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
781 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
782#endif
783 png_read_finish_IDAT(png_ptr);
784
785#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
786 /* Report invalid palette index; added at libng-1.5.10 */
787 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
788 png_ptr->num_palette_max > png_ptr->num_palette)
789 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
790#endif
791
792 do
793 {
794 png_uint_32 length = png_read_chunk_header(png_ptr);
795 png_uint_32 chunk_name = png_ptr->chunk_name;
796
797 if (chunk_name != png_IDAT)
798 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
799
800 if (chunk_name == png_IEND)
801 png_handle_IEND(png_ptr, info_ptr, length);
802
803 else if (chunk_name == png_IHDR)
804 png_handle_IHDR(png_ptr, info_ptr, length);
805
806 else if (info_ptr == NULL)
807 png_crc_finish(png_ptr, length);
808
809#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
810 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
811 {
812 if (chunk_name == png_IDAT)
813 {
814 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
815 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
816 png_benign_error(png_ptr, ".Too many IDATs found");
817 }
818 png_handle_unknown(png_ptr, info_ptr, length, keep);
819 if (chunk_name == png_PLTE)
820 png_ptr->mode |= PNG_HAVE_PLTE;
821 }
822#endif
823
824 else if (chunk_name == png_IDAT)
825 {
826 /* Zero length IDATs are legal after the last IDAT has been
827 * read, but not after other chunks have been read. 1.6 does not
828 * always read all the deflate data; specifically it cannot be relied
829 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
830 * chunks which are longer than zero as well:
831 */
832 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
833 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
834 png_benign_error(png_ptr, "..Too many IDATs found");
835
836 png_crc_finish(png_ptr, length);
837 }
838 else if (chunk_name == png_PLTE)
839 png_handle_PLTE(png_ptr, info_ptr, length);
840
841#ifdef PNG_READ_bKGD_SUPPORTED
842 else if (chunk_name == png_bKGD)
843 png_handle_bKGD(png_ptr, info_ptr, length);
844#endif
845
846#ifdef PNG_READ_cHRM_SUPPORTED
847 else if (chunk_name == png_cHRM)
848 png_handle_cHRM(png_ptr, info_ptr, length);
849#endif
850
851#ifdef PNG_READ_eXIf_SUPPORTED
852 else if (chunk_name == png_eXIf)
853 png_handle_eXIf(png_ptr, info_ptr, length);
854#endif
855
856#ifdef PNG_READ_gAMA_SUPPORTED
857 else if (chunk_name == png_gAMA)
858 png_handle_gAMA(png_ptr, info_ptr, length);
859#endif
860
861#ifdef PNG_READ_hIST_SUPPORTED
862 else if (chunk_name == png_hIST)
863 png_handle_hIST(png_ptr, info_ptr, length);
864#endif
865
866#ifdef PNG_READ_oFFs_SUPPORTED
867 else if (chunk_name == png_oFFs)
868 png_handle_oFFs(png_ptr, info_ptr, length);
869#endif
870
871#ifdef PNG_READ_pCAL_SUPPORTED
872 else if (chunk_name == png_pCAL)
873 png_handle_pCAL(png_ptr, info_ptr, length);
874#endif
875
876#ifdef PNG_READ_sCAL_SUPPORTED
877 else if (chunk_name == png_sCAL)
878 png_handle_sCAL(png_ptr, info_ptr, length);
879#endif
880
881#ifdef PNG_READ_pHYs_SUPPORTED
882 else if (chunk_name == png_pHYs)
883 png_handle_pHYs(png_ptr, info_ptr, length);
884#endif
885
886#ifdef PNG_READ_sBIT_SUPPORTED
887 else if (chunk_name == png_sBIT)
888 png_handle_sBIT(png_ptr, info_ptr, length);
889#endif
890
891#ifdef PNG_READ_sRGB_SUPPORTED
892 else if (chunk_name == png_sRGB)
893 png_handle_sRGB(png_ptr, info_ptr, length);
894#endif
895
896#ifdef PNG_READ_iCCP_SUPPORTED
897 else if (chunk_name == png_iCCP)
898 png_handle_iCCP(png_ptr, info_ptr, length);
899#endif
900
901#ifdef PNG_READ_sPLT_SUPPORTED
902 else if (chunk_name == png_sPLT)
903 png_handle_sPLT(png_ptr, info_ptr, length);
904#endif
905
906#ifdef PNG_READ_tEXt_SUPPORTED
907 else if (chunk_name == png_tEXt)
908 png_handle_tEXt(png_ptr, info_ptr, length);
909#endif
910
911#ifdef PNG_READ_tIME_SUPPORTED
912 else if (chunk_name == png_tIME)
913 png_handle_tIME(png_ptr, info_ptr, length);
914#endif
915
916#ifdef PNG_READ_tRNS_SUPPORTED
917 else if (chunk_name == png_tRNS)
918 png_handle_tRNS(png_ptr, info_ptr, length);
919#endif
920
921#ifdef PNG_READ_zTXt_SUPPORTED
922 else if (chunk_name == png_zTXt)
923 png_handle_zTXt(png_ptr, info_ptr, length);
924#endif
925
926#ifdef PNG_READ_iTXt_SUPPORTED
927 else if (chunk_name == png_iTXt)
928 png_handle_iTXt(png_ptr, info_ptr, length);
929#endif
930
931 else
932 png_handle_unknown(png_ptr, info_ptr, length,
933 PNG_HANDLE_CHUNK_AS_DEFAULT);
934 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
935}
936#endif /* SEQUENTIAL_READ */
937
938/* Free all memory used in the read struct */
939static void
940png_read_destroy(png_structrp png_ptr)
941{
942 png_debug(1, "in png_read_destroy");
943
944#ifdef PNG_READ_GAMMA_SUPPORTED
945 png_destroy_gamma_table(png_ptr);
946#endif
947
948 png_free(png_ptr, png_ptr->big_row_buf);
949 png_ptr->big_row_buf = NULL;
950 png_free(png_ptr, png_ptr->big_prev_row);
951 png_ptr->big_prev_row = NULL;
952 png_free(png_ptr, png_ptr->read_buffer);
953 png_ptr->read_buffer = NULL;
954
955#ifdef PNG_READ_QUANTIZE_SUPPORTED
956 png_free(png_ptr, png_ptr->palette_lookup);
957 png_ptr->palette_lookup = NULL;
958 png_free(png_ptr, png_ptr->quantize_index);
959 png_ptr->quantize_index = NULL;
960#endif
961
962 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
963 {
964 png_zfree(png_ptr, png_ptr->palette);
965 png_ptr->palette = NULL;
966 }
967 png_ptr->free_me &= ~PNG_FREE_PLTE;
968
969#if defined(PNG_tRNS_SUPPORTED) || \
970 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
971 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
972 {
973 png_free(png_ptr, png_ptr->trans_alpha);
974 png_ptr->trans_alpha = NULL;
975 }
976 png_ptr->free_me &= ~PNG_FREE_TRNS;
977#endif
978
979 inflateEnd(&png_ptr->zstream);
980
981#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
982 png_free(png_ptr, png_ptr->save_buffer);
983 png_ptr->save_buffer = NULL;
984#endif
985
986#if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
987 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
988 png_free(png_ptr, png_ptr->unknown_chunk.data);
989 png_ptr->unknown_chunk.data = NULL;
990#endif
991
992#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
993 png_free(png_ptr, png_ptr->chunk_list);
994 png_ptr->chunk_list = NULL;
995#endif
996
997#if defined(PNG_READ_EXPAND_SUPPORTED) && \
998 defined(PNG_ARM_NEON_IMPLEMENTATION)
999 png_free(png_ptr, png_ptr->riffled_palette);
1000 png_ptr->riffled_palette = NULL;
1001#endif
1002
1003 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1004 * callbacks are still set at this point. They are required to complete the
1005 * destruction of the png_struct itself.
1006 */
1007}
1008
1009/* Free all memory used by the read */
1010void PNGAPI
1011png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1012 png_infopp end_info_ptr_ptr)
1013{
1014 png_structrp png_ptr = NULL;
1015
1016 png_debug(1, "in png_destroy_read_struct");
1017
1018 if (png_ptr_ptr != NULL)
1019 png_ptr = *png_ptr_ptr;
1020
1021 if (png_ptr == NULL)
1022 return;
1023
1024 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1025 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1026 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1027 */
1028 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1029 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1030
1031 *png_ptr_ptr = NULL;
1032 png_read_destroy(png_ptr);
1033 png_destroy_png_struct(png_ptr);
1034}
1035
1036void PNGAPI
1037png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1038{
1039 if (png_ptr == NULL)
1040 return;
1041
1042 png_ptr->read_row_fn = read_row_fn;
1043}
1044
1045
1046#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1047#ifdef PNG_INFO_IMAGE_SUPPORTED
1048void PNGAPI
1049png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1050 int transforms, voidp params)
1051{
1052 if (png_ptr == NULL || info_ptr == NULL)
1053 return;
1054
1055 /* png_read_info() gives us all of the information from the
1056 * PNG file before the first IDAT (image data chunk).
1057 */
1058 png_read_info(png_ptr, info_ptr);
1059 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1060 png_error(png_ptr, "Image is too high to process with png_read_png()");
1061
1062 /* -------------- image transformations start here ------------------- */
1063 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1064 * is not implemented. This will only happen in de-configured (non-default)
1065 * libpng builds. The results can be unexpected - png_read_png may return
1066 * short or mal-formed rows because the transform is skipped.
1067 */
1068
1069 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1070 */
1071 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1072 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1073 * did in earlier versions, while "scale_16" is now more accurate.
1074 */
1075#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1076 png_set_scale_16(png_ptr);
1077#else
1078 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1079#endif
1080
1081 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1082 * latter by doing SCALE first. This is ok and allows apps not to check for
1083 * which is supported to get the right answer.
1084 */
1085 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1086#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1087 png_set_strip_16(png_ptr);
1088#else
1089 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1090#endif
1091
1092 /* Strip alpha bytes from the input data without combining with
1093 * the background (not recommended).
1094 */
1095 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1096#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1097 png_set_strip_alpha(png_ptr);
1098#else
1099 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1100#endif
1101
1102 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1103 * byte into separate bytes (useful for paletted and grayscale images).
1104 */
1105 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1106#ifdef PNG_READ_PACK_SUPPORTED
1107 png_set_packing(png_ptr);
1108#else
1109 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1110#endif
1111
1112 /* Change the order of packed pixels to least significant bit first
1113 * (not useful if you are using png_set_packing).
1114 */
1115 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1116#ifdef PNG_READ_PACKSWAP_SUPPORTED
1117 png_set_packswap(png_ptr);
1118#else
1119 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1120#endif
1121
1122 /* Expand paletted colors into true RGB triplets
1123 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1124 * Expand paletted or RGB images with transparency to full alpha
1125 * channels so the data will be available as RGBA quartets.
1126 */
1127 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1128#ifdef PNG_READ_EXPAND_SUPPORTED
1129 png_set_expand(png_ptr);
1130#else
1131 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1132#endif
1133
1134 /* We don't handle background color or gamma transformation or quantizing.
1135 */
1136
1137 /* Invert monochrome files to have 0 as white and 1 as black
1138 */
1139 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1140#ifdef PNG_READ_INVERT_SUPPORTED
1141 png_set_invert_mono(png_ptr);
1142#else
1143 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1144#endif
1145
1146 /* If you want to shift the pixel values from the range [0,255] or
1147 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1148 * colors were originally in:
1149 */
1150 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1151#ifdef PNG_READ_SHIFT_SUPPORTED
1152 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1153 png_set_shift(png_ptr, &info_ptr->sig_bit);
1154#else
1155 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1156#endif
1157
1158 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1159 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1160#ifdef PNG_READ_BGR_SUPPORTED
1161 png_set_bgr(png_ptr);
1162#else
1163 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1164#endif
1165
1166 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1167 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1168#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1169 png_set_swap_alpha(png_ptr);
1170#else
1171 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1172#endif
1173
1174 /* Swap bytes of 16-bit files to least significant byte first */
1175 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1176#ifdef PNG_READ_SWAP_SUPPORTED
1177 png_set_swap(png_ptr);
1178#else
1179 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1180#endif
1181
1182/* Added at libpng-1.2.41 */
1183 /* Invert the alpha channel from opacity to transparency */
1184 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1185#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1186 png_set_invert_alpha(png_ptr);
1187#else
1188 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1189#endif
1190
1191/* Added at libpng-1.2.41 */
1192 /* Expand grayscale image to RGB */
1193 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1194#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1195 png_set_gray_to_rgb(png_ptr);
1196#else
1197 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1198#endif
1199
1200/* Added at libpng-1.5.4 */
1201 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1202#ifdef PNG_READ_EXPAND_16_SUPPORTED
1203 png_set_expand_16(png_ptr);
1204#else
1205 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1206#endif
1207
1208 /* We don't handle adding filler bytes */
1209
1210 /* We use png_read_image and rely on that for interlace handling, but we also
1211 * call png_read_update_info therefore must turn on interlace handling now:
1212 */
1213 (void)png_set_interlace_handling(png_ptr);
1214
1215 /* Optional call to gamma correct and add the background to the palette
1216 * and update info structure. REQUIRED if you are expecting libpng to
1217 * update the palette for you (i.e., you selected such a transform above).
1218 */
1219 png_read_update_info(png_ptr, info_ptr);
1220
1221 /* -------------- image transformations end here ------------------- */
1222
1223 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1224 if (info_ptr->row_pointers == NULL)
1225 {
1226 png_uint_32 iptr;
1227
1228 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1229 info_ptr->height * (sizeof (png_bytep))));
1230
1231 for (iptr=0; iptr<info_ptr->height; iptr++)
1232 info_ptr->row_pointers[iptr] = NULL;
1233
1234 info_ptr->free_me |= PNG_FREE_ROWS;
1235
1236 for (iptr = 0; iptr < info_ptr->height; iptr++)
1237 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1238 png_malloc(png_ptr, info_ptr->rowbytes));
1239 }
1240
1241 png_read_image(png_ptr, info_ptr->row_pointers);
1242 info_ptr->valid |= PNG_INFO_IDAT;
1243
1244 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1245 png_read_end(png_ptr, info_ptr);
1246
1247 PNG_UNUSED(params)
1248}
1249#endif /* INFO_IMAGE */
1250#endif /* SEQUENTIAL_READ */
1251
1252#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1253/* SIMPLIFIED READ
1254 *
1255 * This code currently relies on the sequential reader, though it could easily
1256 * be made to work with the progressive one.
1257 */
1258/* Arguments to png_image_finish_read: */
1259
1260/* Encoding of PNG data (used by the color-map code) */
1261# define P_NOTSET 0 /* File encoding not yet known */
1262# define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1263# define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1264# define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1265# define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1266
1267/* Color-map processing: after libpng has run on the PNG image further
1268 * processing may be needed to convert the data to color-map indices.
1269 */
1270#define PNG_CMAP_NONE 0
1271#define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1272#define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1273#define PNG_CMAP_RGB 3 /* Process RGB data */
1274#define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1275
1276/* The following document where the background is for each processing case. */
1277#define PNG_CMAP_NONE_BACKGROUND 256
1278#define PNG_CMAP_GA_BACKGROUND 231
1279#define PNG_CMAP_TRANS_BACKGROUND 254
1280#define PNG_CMAP_RGB_BACKGROUND 256
1281#define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1282
1283typedef struct
1284{
1285 /* Arguments: */
1286 png_imagep image;
1287 png_voidp buffer;
1288 png_int_32 row_stride;
1289 png_voidp colormap;
1290 png_const_colorp background;
1291 /* Local variables: */
1292 png_voidp local_row;
1293 png_voidp first_row;
1294 ptrdiff_t row_bytes; /* step between rows */
1295 int file_encoding; /* E_ values above */
1296 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1297 int colormap_processing; /* PNG_CMAP_ values above */
1298} png_image_read_control;
1299
1300/* Do all the *safe* initialization - 'safe' means that png_error won't be
1301 * called, so setting up the jmp_buf is not required. This means that anything
1302 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1303 * instead so that control is returned safely back to this routine.
1304 */
1305static int
1306png_image_read_init(png_imagep image)
1307{
1308 if (image->opaque == NULL)
1309 {
1310 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1311 png_safe_error, png_safe_warning);
1312
1313 /* And set the rest of the structure to NULL to ensure that the various
1314 * fields are consistent.
1315 */
1316 memset(image, 0, (sizeof *image));
1317 image->version = PNG_IMAGE_VERSION;
1318
1319 if (png_ptr != NULL)
1320 {
1321 png_infop info_ptr = png_create_info_struct(png_ptr);
1322
1323 if (info_ptr != NULL)
1324 {
1325 png_controlp control = png_voidcast(png_controlp,
1326 png_malloc_warn(png_ptr, (sizeof *control)));
1327
1328 if (control != NULL)
1329 {
1330 memset(control, 0, (sizeof *control));
1331
1332 control->png_ptr = png_ptr;
1333 control->info_ptr = info_ptr;
1334 control->for_write = 0;
1335
1336 image->opaque = control;
1337 return 1;
1338 }
1339
1340 /* Error clean up */
1341 png_destroy_info_struct(png_ptr, &info_ptr);
1342 }
1343
1344 png_destroy_read_struct(&png_ptr, NULL, NULL);
1345 }
1346
1347 return png_image_error(image, "png_image_read: out of memory");
1348 }
1349
1350 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1351}
1352
1353/* Utility to find the base format of a PNG file from a png_struct. */
1354static png_uint_32
1355png_image_format(png_structrp png_ptr)
1356{
1357 png_uint_32 format = 0;
1358
1359 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1360 format |= PNG_FORMAT_FLAG_COLOR;
1361
1362 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1363 format |= PNG_FORMAT_FLAG_ALPHA;
1364
1365 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1366 * sets the png_struct fields; that's all we are interested in here. The
1367 * precise interaction with an app call to png_set_tRNS and PNG file reading
1368 * is unclear.
1369 */
1370 else if (png_ptr->num_trans > 0)
1371 format |= PNG_FORMAT_FLAG_ALPHA;
1372
1373 if (png_ptr->bit_depth == 16)
1374 format |= PNG_FORMAT_FLAG_LINEAR;
1375
1376 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1377 format |= PNG_FORMAT_FLAG_COLORMAP;
1378
1379 return format;
1380}
1381
1382/* Is the given gamma significantly different from sRGB? The test is the same
1383 * one used in pngrtran.c when deciding whether to do gamma correction. The
1384 * arithmetic optimizes the division by using the fact that the inverse of the
1385 * file sRGB gamma is 2.2
1386 */
1387static int
1388png_gamma_not_sRGB(png_fixed_point g)
1389{
1390 if (g < PNG_FP_1)
1391 {
1392 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1393 if (g == 0)
1394 return 0;
1395
1396 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1397 }
1398
1399 return 1;
1400}
1401
1402/* Do the main body of a 'png_image_begin_read' function; read the PNG file
1403 * header and fill in all the information. This is executed in a safe context,
1404 * unlike the init routine above.
1405 */
1406static int
1407png_image_read_header(png_voidp argument)
1408{
1409 png_imagep image = png_voidcast(png_imagep, argument);
1410 png_structrp png_ptr = image->opaque->png_ptr;
1411 png_inforp info_ptr = image->opaque->info_ptr;
1412
1413#ifdef PNG_BENIGN_ERRORS_SUPPORTED
1414 png_set_benign_errors(png_ptr, 1/*warn*/);
1415#endif
1416 png_read_info(png_ptr, info_ptr);
1417
1418 /* Do this the fast way; just read directly out of png_struct. */
1419 image->width = png_ptr->width;
1420 image->height = png_ptr->height;
1421
1422 {
1423 png_uint_32 format = png_image_format(png_ptr);
1424
1425 image->format = format;
1426
1427#ifdef PNG_COLORSPACE_SUPPORTED
1428 /* Does the colorspace match sRGB? If there is no color endpoint
1429 * (colorant) information assume yes, otherwise require the
1430 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1431 * colorspace has been determined to be invalid ignore it.
1432 */
1433 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1434 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1435 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1436 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1437#endif
1438 }
1439
1440 /* We need the maximum number of entries regardless of the format the
1441 * application sets here.
1442 */
1443 {
1444 png_uint_32 cmap_entries;
1445
1446 switch (png_ptr->color_type)
1447 {
1448 case PNG_COLOR_TYPE_GRAY:
1449 cmap_entries = 1U << png_ptr->bit_depth;
1450 break;
1451
1452 case PNG_COLOR_TYPE_PALETTE:
1453 cmap_entries = (png_uint_32)png_ptr->num_palette;
1454 break;
1455
1456 default:
1457 cmap_entries = 256;
1458 break;
1459 }
1460
1461 if (cmap_entries > 256)
1462 cmap_entries = 256;
1463
1464 image->colormap_entries = cmap_entries;
1465 }
1466
1467 return 1;
1468}
1469
1470#ifdef PNG_STDIO_SUPPORTED
1471int PNGAPI
1472png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1473{
1474 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1475 {
1476 if (file != NULL)
1477 {
1478 if (png_image_read_init(image) != 0)
1479 {
1480 /* This is slightly evil, but png_init_io doesn't do anything other
1481 * than this and we haven't changed the standard IO functions so
1482 * this saves a 'safe' function.
1483 */
1484 image->opaque->png_ptr->io_ptr = file;
1485 return png_safe_execute(image, png_image_read_header, image);
1486 }
1487 }
1488
1489 else
1490 return png_image_error(image,
1491 "png_image_begin_read_from_stdio: invalid argument");
1492 }
1493
1494 else if (image != NULL)
1495 return png_image_error(image,
1496 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1497
1498 return 0;
1499}
1500
1501int PNGAPI
1502png_image_begin_read_from_file(png_imagep image, const char *file_name)
1503{
1504 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1505 {
1506 if (file_name != NULL)
1507 {
1508 FILE *fp = fopen(file_name, "rb");
1509
1510 if (fp != NULL)
1511 {
1512 if (png_image_read_init(image) != 0)
1513 {
1514 image->opaque->png_ptr->io_ptr = fp;
1515 image->opaque->owned_file = 1;
1516 return png_safe_execute(image, png_image_read_header, image);
1517 }
1518
1519 /* Clean up: just the opened file. */
1520 (void)fclose(fp);
1521 }
1522
1523 else
1524 return png_image_error(image, strerror(errno));
1525 }
1526
1527 else
1528 return png_image_error(image,
1529 "png_image_begin_read_from_file: invalid argument");
1530 }
1531
1532 else if (image != NULL)
1533 return png_image_error(image,
1534 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1535
1536 return 0;
1537}
1538#endif /* STDIO */
1539
1540static void PNGCBAPI
1541png_image_memory_read(png_structp png_ptr, png_bytep out, size_t need)
1542{
1543 if (png_ptr != NULL)
1544 {
1545 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1546 if (image != NULL)
1547 {
1548 png_controlp cp = image->opaque;
1549 if (cp != NULL)
1550 {
1551 png_const_bytep memory = cp->memory;
1552 size_t size = cp->size;
1553
1554 if (memory != NULL && size >= need)
1555 {
1556 memcpy(out, memory, need);
1557 cp->memory = memory + need;
1558 cp->size = size - need;
1559 return;
1560 }
1561
1562 png_error(png_ptr, "read beyond end of data");
1563 }
1564 }
1565
1566 png_error(png_ptr, "invalid memory read");
1567 }
1568}
1569
1570int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1571 png_const_voidp memory, size_t size)
1572{
1573 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1574 {
1575 if (memory != NULL && size > 0)
1576 {
1577 if (png_image_read_init(image) != 0)
1578 {
1579 /* Now set the IO functions to read from the memory buffer and
1580 * store it into io_ptr. Again do this in-place to avoid calling a
1581 * libpng function that requires error handling.
1582 */
1583 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1584 image->opaque->size = size;
1585 image->opaque->png_ptr->io_ptr = image;
1586 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1587
1588 return png_safe_execute(image, png_image_read_header, image);
1589 }
1590 }
1591
1592 else
1593 return png_image_error(image,
1594 "png_image_begin_read_from_memory: invalid argument");
1595 }
1596
1597 else if (image != NULL)
1598 return png_image_error(image,
1599 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1600
1601 return 0;
1602}
1603
1604/* Utility function to skip chunks that are not used by the simplified image
1605 * read functions and an appropriate macro to call it.
1606 */
1607#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1608static void
1609png_image_skip_unused_chunks(png_structrp png_ptr)
1610{
1611 /* Prepare the reader to ignore all recognized chunks whose data will not
1612 * be used, i.e., all chunks recognized by libpng except for those
1613 * involved in basic image reading:
1614 *
1615 * IHDR, PLTE, IDAT, IEND
1616 *
1617 * Or image data handling:
1618 *
1619 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1620 *
1621 * This provides a small performance improvement and eliminates any
1622 * potential vulnerability to security problems in the unused chunks.
1623 *
1624 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1625 * too. This allows the simplified API to be compiled without iCCP support,
1626 * however if the support is there the chunk is still checked to detect
1627 * errors (which are unfortunately quite common.)
1628 */
1629 {
1630 static const png_byte chunks_to_process[] = {
1631 98, 75, 71, 68, '\0', /* bKGD */
1632 99, 72, 82, 77, '\0', /* cHRM */
1633 103, 65, 77, 65, '\0', /* gAMA */
1634# ifdef PNG_READ_iCCP_SUPPORTED
1635 105, 67, 67, 80, '\0', /* iCCP */
1636# endif
1637 115, 66, 73, 84, '\0', /* sBIT */
1638 115, 82, 71, 66, '\0', /* sRGB */
1639 };
1640
1641 /* Ignore unknown chunks and all other chunks except for the
1642 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1643 */
1644 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1645 NULL, -1);
1646
1647 /* But do not ignore image data handling chunks */
1648 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1649 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1650 }
1651}
1652
1653# define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1654#else
1655# define PNG_SKIP_CHUNKS(p) ((void)0)
1656#endif /* HANDLE_AS_UNKNOWN */
1657
1658/* The following macro gives the exact rounded answer for all values in the
1659 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1660 * the correct numbers 0..5
1661 */
1662#define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1663
1664/* Utility functions to make particular color-maps */
1665static void
1666set_file_encoding(png_image_read_control *display)
1667{
1668 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1669 if (png_gamma_significant(g) != 0)
1670 {
1671 if (png_gamma_not_sRGB(g) != 0)
1672 {
1673 display->file_encoding = P_FILE;
1674 display->gamma_to_linear = png_reciprocal(g);
1675 }
1676
1677 else
1678 display->file_encoding = P_sRGB;
1679 }
1680
1681 else
1682 display->file_encoding = P_LINEAR8;
1683}
1684
1685static unsigned int
1686decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1687{
1688 if (encoding == P_FILE) /* double check */
1689 encoding = display->file_encoding;
1690
1691 if (encoding == P_NOTSET) /* must be the file encoding */
1692 {
1693 set_file_encoding(display);
1694 encoding = display->file_encoding;
1695 }
1696
1697 switch (encoding)
1698 {
1699 case P_FILE:
1700 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1701 break;
1702
1703 case P_sRGB:
1704 value = png_sRGB_table[value];
1705 break;
1706
1707 case P_LINEAR:
1708 break;
1709
1710 case P_LINEAR8:
1711 value *= 257;
1712 break;
1713
1714#ifdef __GNUC__
1715 default:
1716 png_error(display->image->opaque->png_ptr,
1717 "unexpected encoding (internal error)");
1718#endif
1719 }
1720
1721 return value;
1722}
1723
1724static png_uint_32
1725png_colormap_compose(png_image_read_control *display,
1726 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1727 png_uint_32 background, int encoding)
1728{
1729 /* The file value is composed on the background, the background has the given
1730 * encoding and so does the result, the file is encoded with P_FILE and the
1731 * file and alpha are 8-bit values. The (output) encoding will always be
1732 * P_LINEAR or P_sRGB.
1733 */
1734 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1735 png_uint_32 b = decode_gamma(display, background, encoding);
1736
1737 /* The alpha is always an 8-bit value (it comes from the palette), the value
1738 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1739 */
1740 f = f * alpha + b * (255-alpha);
1741
1742 if (encoding == P_LINEAR)
1743 {
1744 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1745 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1746 */
1747 f *= 257; /* Now scaled by 65535 */
1748 f += f >> 16;
1749 f = (f+32768) >> 16;
1750 }
1751
1752 else /* P_sRGB */
1753 f = PNG_sRGB_FROM_LINEAR(f);
1754
1755 return f;
1756}
1757
1758/* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1759 * be 8-bit.
1760 */
1761static void
1762png_create_colormap_entry(png_image_read_control *display,
1763 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1764 png_uint_32 alpha, int encoding)
1765{
1766 png_imagep image = display->image;
1767 int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1768 P_LINEAR : P_sRGB;
1769 int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1770 (red != green || green != blue);
1771
1772 if (ip > 255)
1773 png_error(image->opaque->png_ptr, "color-map index out of range");
1774
1775 /* Update the cache with whether the file gamma is significantly different
1776 * from sRGB.
1777 */
1778 if (encoding == P_FILE)
1779 {
1780 if (display->file_encoding == P_NOTSET)
1781 set_file_encoding(display);
1782
1783 /* Note that the cached value may be P_FILE too, but if it is then the
1784 * gamma_to_linear member has been set.
1785 */
1786 encoding = display->file_encoding;
1787 }
1788
1789 if (encoding == P_FILE)
1790 {
1791 png_fixed_point g = display->gamma_to_linear;
1792
1793 red = png_gamma_16bit_correct(red*257, g);
1794 green = png_gamma_16bit_correct(green*257, g);
1795 blue = png_gamma_16bit_correct(blue*257, g);
1796
1797 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1798 {
1799 alpha *= 257;
1800 encoding = P_LINEAR;
1801 }
1802
1803 else
1804 {
1805 red = PNG_sRGB_FROM_LINEAR(red * 255);
1806 green = PNG_sRGB_FROM_LINEAR(green * 255);
1807 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1808 encoding = P_sRGB;
1809 }
1810 }
1811
1812 else if (encoding == P_LINEAR8)
1813 {
1814 /* This encoding occurs quite frequently in test cases because PngSuite
1815 * includes a gAMA 1.0 chunk with most images.
1816 */
1817 red *= 257;
1818 green *= 257;
1819 blue *= 257;
1820 alpha *= 257;
1821 encoding = P_LINEAR;
1822 }
1823
1824 else if (encoding == P_sRGB &&
1825 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1826 {
1827 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1828 * linear.
1829 */
1830 red = png_sRGB_table[red];
1831 green = png_sRGB_table[green];
1832 blue = png_sRGB_table[blue];
1833 alpha *= 257;
1834 encoding = P_LINEAR;
1835 }
1836
1837 /* This is set if the color isn't gray but the output is. */
1838 if (encoding == P_LINEAR)
1839 {
1840 if (convert_to_Y != 0)
1841 {
1842 /* NOTE: these values are copied from png_do_rgb_to_gray */
1843 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1844 (png_uint_32)2366 * blue;
1845
1846 if (output_encoding == P_LINEAR)
1847 y = (y + 16384) >> 15;
1848
1849 else
1850 {
1851 /* y is scaled by 32768, we need it scaled by 255: */
1852 y = (y + 128) >> 8;
1853 y *= 255;
1854 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1855 alpha = PNG_DIV257(alpha);
1856 encoding = P_sRGB;
1857 }
1858
1859 blue = red = green = y;
1860 }
1861
1862 else if (output_encoding == P_sRGB)
1863 {
1864 red = PNG_sRGB_FROM_LINEAR(red * 255);
1865 green = PNG_sRGB_FROM_LINEAR(green * 255);
1866 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1867 alpha = PNG_DIV257(alpha);
1868 encoding = P_sRGB;
1869 }
1870 }
1871
1872 if (encoding != output_encoding)
1873 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1874
1875 /* Store the value. */
1876 {
1877# ifdef PNG_FORMAT_AFIRST_SUPPORTED
1878 int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1879 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1880# else
1881# define afirst 0
1882# endif
1883# ifdef PNG_FORMAT_BGR_SUPPORTED
1884 int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1885# else
1886# define bgr 0
1887# endif
1888
1889 if (output_encoding == P_LINEAR)
1890 {
1891 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1892
1893 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1894
1895 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1896 * value, if less than 65535 (this is, effectively, composite on black
1897 * if the alpha channel is removed.)
1898 */
1899 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1900 {
1901 case 4:
1902 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1903 /* FALLTHROUGH */
1904
1905 case 3:
1906 if (alpha < 65535)
1907 {
1908 if (alpha > 0)
1909 {
1910 blue = (blue * alpha + 32767U)/65535U;
1911 green = (green * alpha + 32767U)/65535U;
1912 red = (red * alpha + 32767U)/65535U;
1913 }
1914
1915 else
1916 red = green = blue = 0;
1917 }
1918 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1919 entry[afirst + 1] = (png_uint_16)green;
1920 entry[afirst + bgr] = (png_uint_16)red;
1921 break;
1922
1923 case 2:
1924 entry[1 ^ afirst] = (png_uint_16)alpha;
1925 /* FALLTHROUGH */
1926
1927 case 1:
1928 if (alpha < 65535)
1929 {
1930 if (alpha > 0)
1931 green = (green * alpha + 32767U)/65535U;
1932
1933 else
1934 green = 0;
1935 }
1936 entry[afirst] = (png_uint_16)green;
1937 break;
1938
1939 default:
1940 break;
1941 }
1942 }
1943
1944 else /* output encoding is P_sRGB */
1945 {
1946 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1947
1948 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1949
1950 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1951 {
1952 case 4:
1953 entry[afirst ? 0 : 3] = (png_byte)alpha;
1954 /* FALLTHROUGH */
1955 case 3:
1956 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1957 entry[afirst + 1] = (png_byte)green;
1958 entry[afirst + bgr] = (png_byte)red;
1959 break;
1960
1961 case 2:
1962 entry[1 ^ afirst] = (png_byte)alpha;
1963 /* FALLTHROUGH */
1964 case 1:
1965 entry[afirst] = (png_byte)green;
1966 break;
1967
1968 default:
1969 break;
1970 }
1971 }
1972
1973# ifdef afirst
1974# undef afirst
1975# endif
1976# ifdef bgr
1977# undef bgr
1978# endif
1979 }
1980}
1981
1982static int
1983make_gray_file_colormap(png_image_read_control *display)
1984{
1985 unsigned int i;
1986
1987 for (i=0; i<256; ++i)
1988 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1989
1990 return (int)i;
1991}
1992
1993static int
1994make_gray_colormap(png_image_read_control *display)
1995{
1996 unsigned int i;
1997
1998 for (i=0; i<256; ++i)
1999 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
2000
2001 return (int)i;
2002}
2003#define PNG_GRAY_COLORMAP_ENTRIES 256
2004
2005static int
2006make_ga_colormap(png_image_read_control *display)
2007{
2008 unsigned int i, a;
2009
2010 /* Alpha is retained, the output will be a color-map with entries
2011 * selected by six levels of alpha. One transparent entry, 6 gray
2012 * levels for all the intermediate alpha values, leaving 230 entries
2013 * for the opaque grays. The color-map entries are the six values
2014 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2015 * relevant entry.
2016 *
2017 * if (alpha > 229) // opaque
2018 * {
2019 * // The 231 entries are selected to make the math below work:
2020 * base = 0;
2021 * entry = (231 * gray + 128) >> 8;
2022 * }
2023 * else if (alpha < 26) // transparent
2024 * {
2025 * base = 231;
2026 * entry = 0;
2027 * }
2028 * else // partially opaque
2029 * {
2030 * base = 226 + 6 * PNG_DIV51(alpha);
2031 * entry = PNG_DIV51(gray);
2032 * }
2033 */
2034 i = 0;
2035 while (i < 231)
2036 {
2037 unsigned int gray = (i * 256 + 115) / 231;
2038 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2039 }
2040
2041 /* 255 is used here for the component values for consistency with the code
2042 * that undoes premultiplication in pngwrite.c.
2043 */
2044 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2045
2046 for (a=1; a<5; ++a)
2047 {
2048 unsigned int g;
2049
2050 for (g=0; g<6; ++g)
2051 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2052 P_sRGB);
2053 }
2054
2055 return (int)i;
2056}
2057
2058#define PNG_GA_COLORMAP_ENTRIES 256
2059
2060static int
2061make_rgb_colormap(png_image_read_control *display)
2062{
2063 unsigned int i, r;
2064
2065 /* Build a 6x6x6 opaque RGB cube */
2066 for (i=r=0; r<6; ++r)
2067 {
2068 unsigned int g;
2069
2070 for (g=0; g<6; ++g)
2071 {
2072 unsigned int b;
2073
2074 for (b=0; b<6; ++b)
2075 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2076 P_sRGB);
2077 }
2078 }
2079
2080 return (int)i;
2081}
2082
2083#define PNG_RGB_COLORMAP_ENTRIES 216
2084
2085/* Return a palette index to the above palette given three 8-bit sRGB values. */
2086#define PNG_RGB_INDEX(r,g,b) \
2087 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2088
2089static int
2090png_image_read_colormap(png_voidp argument)
2091{
2092 png_image_read_control *display =
2093 png_voidcast(png_image_read_control*, argument);
2094 png_imagep image = display->image;
2095
2096 png_structrp png_ptr = image->opaque->png_ptr;
2097 png_uint_32 output_format = image->format;
2098 int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2099 P_LINEAR : P_sRGB;
2100
2101 unsigned int cmap_entries;
2102 unsigned int output_processing; /* Output processing option */
2103 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2104
2105 /* Background information; the background color and the index of this color
2106 * in the color-map if it exists (else 256).
2107 */
2108 unsigned int background_index = 256;
2109 png_uint_32 back_r, back_g, back_b;
2110
2111 /* Flags to accumulate things that need to be done to the input. */
2112 int expand_tRNS = 0;
2113
2114 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2115 * very difficult to do, the results look awful, and it is difficult to see
2116 * what possible use it is because the application can't control the
2117 * color-map.
2118 */
2119 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2120 png_ptr->num_trans > 0) /* alpha in input */ &&
2121 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2122 {
2123 if (output_encoding == P_LINEAR) /* compose on black */
2124 back_b = back_g = back_r = 0;
2125
2126 else if (display->background == NULL /* no way to remove it */)
2127 png_error(png_ptr,
2128 "background color must be supplied to remove alpha/transparency");
2129
2130 /* Get a copy of the background color (this avoids repeating the checks
2131 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2132 * output format.
2133 */
2134 else
2135 {
2136 back_g = display->background->green;
2137 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2138 {
2139 back_r = display->background->red;
2140 back_b = display->background->blue;
2141 }
2142 else
2143 back_b = back_r = back_g;
2144 }
2145 }
2146
2147 else if (output_encoding == P_LINEAR)
2148 back_b = back_r = back_g = 65535;
2149
2150 else
2151 back_b = back_r = back_g = 255;
2152
2153 /* Default the input file gamma if required - this is necessary because
2154 * libpng assumes that if no gamma information is present the data is in the
2155 * output format, but the simplified API deduces the gamma from the input
2156 * format.
2157 */
2158 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2159 {
2160 /* Do this directly, not using the png_colorspace functions, to ensure
2161 * that it happens even if the colorspace is invalid (though probably if
2162 * it is the setting will be ignored) Note that the same thing can be
2163 * achieved at the application interface with png_set_gAMA.
2164 */
2165 if (png_ptr->bit_depth == 16 &&
2166 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2167 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2168
2169 else
2170 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2171
2172 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2173 }
2174
2175 /* Decide what to do based on the PNG color type of the input data. The
2176 * utility function png_create_colormap_entry deals with most aspects of the
2177 * output transformations; this code works out how to produce bytes of
2178 * color-map entries from the original format.
2179 */
2180 switch (png_ptr->color_type)
2181 {
2182 case PNG_COLOR_TYPE_GRAY:
2183 if (png_ptr->bit_depth <= 8)
2184 {
2185 /* There at most 256 colors in the output, regardless of
2186 * transparency.
2187 */
2188 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2189
2190 cmap_entries = 1U << png_ptr->bit_depth;
2191 if (cmap_entries > image->colormap_entries)
2192 png_error(png_ptr, "gray[8] color-map: too few entries");
2193
2194 step = 255 / (cmap_entries - 1);
2195 output_processing = PNG_CMAP_NONE;
2196
2197 /* If there is a tRNS chunk then this either selects a transparent
2198 * value or, if the output has no alpha, the background color.
2199 */
2200 if (png_ptr->num_trans > 0)
2201 {
2202 trans = png_ptr->trans_color.gray;
2203
2204 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2205 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2206 }
2207
2208 /* png_create_colormap_entry just takes an RGBA and writes the
2209 * corresponding color-map entry using the format from 'image',
2210 * including the required conversion to sRGB or linear as
2211 * appropriate. The input values are always either sRGB (if the
2212 * gamma correction flag is 0) or 0..255 scaled file encoded values
2213 * (if the function must gamma correct them).
2214 */
2215 for (i=val=0; i<cmap_entries; ++i, val += step)
2216 {
2217 /* 'i' is a file value. While this will result in duplicated
2218 * entries for 8-bit non-sRGB encoded files it is necessary to
2219 * have non-gamma corrected values to do tRNS handling.
2220 */
2221 if (i != trans)
2222 png_create_colormap_entry(display, i, val, val, val, 255,
2223 P_FILE/*8-bit with file gamma*/);
2224
2225 /* Else this entry is transparent. The colors don't matter if
2226 * there is an alpha channel (back_alpha == 0), but it does no
2227 * harm to pass them in; the values are not set above so this
2228 * passes in white.
2229 *
2230 * NOTE: this preserves the full precision of the application
2231 * supplied background color when it is used.
2232 */
2233 else
2234 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2235 back_alpha, output_encoding);
2236 }
2237
2238 /* We need libpng to preserve the original encoding. */
2239 data_encoding = P_FILE;
2240
2241 /* The rows from libpng, while technically gray values, are now also
2242 * color-map indices; however, they may need to be expanded to 1
2243 * byte per pixel. This is what png_set_packing does (i.e., it
2244 * unpacks the bit values into bytes.)
2245 */
2246 if (png_ptr->bit_depth < 8)
2247 png_set_packing(png_ptr);
2248 }
2249
2250 else /* bit depth is 16 */
2251 {
2252 /* The 16-bit input values can be converted directly to 8-bit gamma
2253 * encoded values; however, if a tRNS chunk is present 257 color-map
2254 * entries are required. This means that the extra entry requires
2255 * special processing; add an alpha channel, sacrifice gray level
2256 * 254 and convert transparent (alpha==0) entries to that.
2257 *
2258 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2259 * same time to minimize quality loss. If a tRNS chunk is present
2260 * this means libpng must handle it too; otherwise it is impossible
2261 * to do the exact match on the 16-bit value.
2262 *
2263 * If the output has no alpha channel *and* the background color is
2264 * gray then it is possible to let libpng handle the substitution by
2265 * ensuring that the corresponding gray level matches the background
2266 * color exactly.
2267 */
2268 data_encoding = P_sRGB;
2269
2270 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2271 png_error(png_ptr, "gray[16] color-map: too few entries");
2272
2273 cmap_entries = (unsigned int)make_gray_colormap(display);
2274
2275 if (png_ptr->num_trans > 0)
2276 {
2277 unsigned int back_alpha;
2278
2279 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2280 back_alpha = 0;
2281
2282 else
2283 {
2284 if (back_r == back_g && back_g == back_b)
2285 {
2286 /* Background is gray; no special processing will be
2287 * required.
2288 */
2289 png_color_16 c;
2290 png_uint_32 gray = back_g;
2291
2292 if (output_encoding == P_LINEAR)
2293 {
2294 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2295
2296 /* And make sure the corresponding palette entry
2297 * matches.
2298 */
2299 png_create_colormap_entry(display, gray, back_g, back_g,
2300 back_g, 65535, P_LINEAR);
2301 }
2302
2303 /* The background passed to libpng, however, must be the
2304 * sRGB value.
2305 */
2306 c.index = 0; /*unused*/
2307 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2308
2309 /* NOTE: does this work without expanding tRNS to alpha?
2310 * It should be the color->gray case below apparently
2311 * doesn't.
2312 */
2313 png_set_background_fixed(png_ptr, &c,
2314 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2315 0/*gamma: not used*/);
2316
2317 output_processing = PNG_CMAP_NONE;
2318 break;
2319 }
2320#ifdef __COVERITY__
2321 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2322 * here.
2323 */
2324 back_alpha = 255;
2325#else
2326 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2327#endif
2328 }
2329
2330 /* output_processing means that the libpng-processed row will be
2331 * 8-bit GA and it has to be processing to single byte color-map
2332 * values. Entry 254 is replaced by either a completely
2333 * transparent entry or by the background color at full
2334 * precision (and the background color is not a simple gray
2335 * level in this case.)
2336 */
2337 expand_tRNS = 1;
2338 output_processing = PNG_CMAP_TRANS;
2339 background_index = 254;
2340
2341 /* And set (overwrite) color-map entry 254 to the actual
2342 * background color at full precision.
2343 */
2344 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2345 back_alpha, output_encoding);
2346 }
2347
2348 else
2349 output_processing = PNG_CMAP_NONE;
2350 }
2351 break;
2352
2353 case PNG_COLOR_TYPE_GRAY_ALPHA:
2354 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2355 * of 65536 combinations. If, however, the alpha channel is to be
2356 * removed there are only 256 possibilities if the background is gray.
2357 * (Otherwise there is a subset of the 65536 possibilities defined by
2358 * the triangle between black, white and the background color.)
2359 *
2360 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2361 * worry about tRNS matching - tRNS is ignored if there is an alpha
2362 * channel.
2363 */
2364 data_encoding = P_sRGB;
2365
2366 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2367 {
2368 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2369 png_error(png_ptr, "gray+alpha color-map: too few entries");
2370
2371 cmap_entries = (unsigned int)make_ga_colormap(display);
2372
2373 background_index = PNG_CMAP_GA_BACKGROUND;
2374 output_processing = PNG_CMAP_GA;
2375 }
2376
2377 else /* alpha is removed */
2378 {
2379 /* Alpha must be removed as the PNG data is processed when the
2380 * background is a color because the G and A channels are
2381 * independent and the vector addition (non-parallel vectors) is a
2382 * 2-D problem.
2383 *
2384 * This can be reduced to the same algorithm as above by making a
2385 * colormap containing gray levels (for the opaque grays), a
2386 * background entry (for a transparent pixel) and a set of four six
2387 * level color values, one set for each intermediate alpha value.
2388 * See the comments in make_ga_colormap for how this works in the
2389 * per-pixel processing.
2390 *
2391 * If the background is gray, however, we only need a 256 entry gray
2392 * level color map. It is sufficient to make the entry generated
2393 * for the background color be exactly the color specified.
2394 */
2395 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2396 (back_r == back_g && back_g == back_b))
2397 {
2398 /* Background is gray; no special processing will be required. */
2399 png_color_16 c;
2400 png_uint_32 gray = back_g;
2401
2402 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2403 png_error(png_ptr, "gray-alpha color-map: too few entries");
2404
2405 cmap_entries = (unsigned int)make_gray_colormap(display);
2406
2407 if (output_encoding == P_LINEAR)
2408 {
2409 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2410
2411 /* And make sure the corresponding palette entry matches. */
2412 png_create_colormap_entry(display, gray, back_g, back_g,
2413 back_g, 65535, P_LINEAR);
2414 }
2415
2416 /* The background passed to libpng, however, must be the sRGB
2417 * value.
2418 */
2419 c.index = 0; /*unused*/
2420 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2421
2422 png_set_background_fixed(png_ptr, &c,
2423 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2424 0/*gamma: not used*/);
2425
2426 output_processing = PNG_CMAP_NONE;
2427 }
2428
2429 else
2430 {
2431 png_uint_32 i, a;
2432
2433 /* This is the same as png_make_ga_colormap, above, except that
2434 * the entries are all opaque.
2435 */
2436 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2437 png_error(png_ptr, "ga-alpha color-map: too few entries");
2438
2439 i = 0;
2440 while (i < 231)
2441 {
2442 png_uint_32 gray = (i * 256 + 115) / 231;
2443 png_create_colormap_entry(display, i++, gray, gray, gray,
2444 255, P_sRGB);
2445 }
2446
2447 /* NOTE: this preserves the full precision of the application
2448 * background color.
2449 */
2450 background_index = i;
2451 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2452#ifdef __COVERITY__
2453 /* Coverity claims that output_encoding
2454 * cannot be 2 (P_LINEAR) here.
2455 */ 255U,
2456#else
2457 output_encoding == P_LINEAR ? 65535U : 255U,
2458#endif
2459 output_encoding);
2460
2461 /* For non-opaque input composite on the sRGB background - this
2462 * requires inverting the encoding for each component. The input
2463 * is still converted to the sRGB encoding because this is a
2464 * reasonable approximate to the logarithmic curve of human
2465 * visual sensitivity, at least over the narrow range which PNG
2466 * represents. Consequently 'G' is always sRGB encoded, while
2467 * 'A' is linear. We need the linear background colors.
2468 */
2469 if (output_encoding == P_sRGB) /* else already linear */
2470 {
2471 /* This may produce a value not exactly matching the
2472 * background, but that's ok because these numbers are only
2473 * used when alpha != 0
2474 */
2475 back_r = png_sRGB_table[back_r];
2476 back_g = png_sRGB_table[back_g];
2477 back_b = png_sRGB_table[back_b];
2478 }
2479
2480 for (a=1; a<5; ++a)
2481 {
2482 unsigned int g;
2483
2484 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2485 * by an 8-bit alpha value (0..255).
2486 */
2487 png_uint_32 alpha = 51 * a;
2488 png_uint_32 back_rx = (255-alpha) * back_r;
2489 png_uint_32 back_gx = (255-alpha) * back_g;
2490 png_uint_32 back_bx = (255-alpha) * back_b;
2491
2492 for (g=0; g<6; ++g)
2493 {
2494 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2495
2496 png_create_colormap_entry(display, i++,
2497 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2498 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2499 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2500 }
2501 }
2502
2503 cmap_entries = i;
2504 output_processing = PNG_CMAP_GA;
2505 }
2506 }
2507 break;
2508
2509 case PNG_COLOR_TYPE_RGB:
2510 case PNG_COLOR_TYPE_RGB_ALPHA:
2511 /* Exclude the case where the output is gray; we can always handle this
2512 * with the cases above.
2513 */
2514 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2515 {
2516 /* The color-map will be grayscale, so we may as well convert the
2517 * input RGB values to a simple grayscale and use the grayscale
2518 * code above.
2519 *
2520 * NOTE: calling this apparently damages the recognition of the
2521 * transparent color in background color handling; call
2522 * png_set_tRNS_to_alpha before png_set_background_fixed.
2523 */
2524 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2525 -1);
2526 data_encoding = P_sRGB;
2527
2528 /* The output will now be one or two 8-bit gray or gray+alpha
2529 * channels. The more complex case arises when the input has alpha.
2530 */
2531 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2532 png_ptr->num_trans > 0) &&
2533 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2534 {
2535 /* Both input and output have an alpha channel, so no background
2536 * processing is required; just map the GA bytes to the right
2537 * color-map entry.
2538 */
2539 expand_tRNS = 1;
2540
2541 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2542 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2543
2544 cmap_entries = (unsigned int)make_ga_colormap(display);
2545 background_index = PNG_CMAP_GA_BACKGROUND;
2546 output_processing = PNG_CMAP_GA;
2547 }
2548
2549 else
2550 {
2551 /* Either the input or the output has no alpha channel, so there
2552 * will be no non-opaque pixels in the color-map; it will just be
2553 * grayscale.
2554 */
2555 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2556 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2557
2558 /* Ideally this code would use libpng to do the gamma correction,
2559 * but if an input alpha channel is to be removed we will hit the
2560 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2561 * correction bug). Fix this by dropping the gamma correction in
2562 * this case and doing it in the palette; this will result in
2563 * duplicate palette entries, but that's better than the
2564 * alternative of double gamma correction.
2565 */
2566 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2567 png_ptr->num_trans > 0) &&
2568 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2569 {
2570 cmap_entries = (unsigned int)make_gray_file_colormap(display);
2571 data_encoding = P_FILE;
2572 }
2573
2574 else
2575 cmap_entries = (unsigned int)make_gray_colormap(display);
2576
2577 /* But if the input has alpha or transparency it must be removed
2578 */
2579 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2580 png_ptr->num_trans > 0)
2581 {
2582 png_color_16 c;
2583 png_uint_32 gray = back_g;
2584
2585 /* We need to ensure that the application background exists in
2586 * the colormap and that completely transparent pixels map to
2587 * it. Achieve this simply by ensuring that the entry
2588 * selected for the background really is the background color.
2589 */
2590 if (data_encoding == P_FILE) /* from the fixup above */
2591 {
2592 /* The app supplied a gray which is in output_encoding, we
2593 * need to convert it to a value of the input (P_FILE)
2594 * encoding then set this palette entry to the required
2595 * output encoding.
2596 */
2597 if (output_encoding == P_sRGB)
2598 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2599
2600 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2601 png_ptr->colorspace.gamma)); /* now P_FILE */
2602
2603 /* And make sure the corresponding palette entry contains
2604 * exactly the required sRGB value.
2605 */
2606 png_create_colormap_entry(display, gray, back_g, back_g,
2607 back_g, 0/*unused*/, output_encoding);
2608 }
2609
2610 else if (output_encoding == P_LINEAR)
2611 {
2612 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2613
2614 /* And make sure the corresponding palette entry matches.
2615 */
2616 png_create_colormap_entry(display, gray, back_g, back_g,
2617 back_g, 0/*unused*/, P_LINEAR);
2618 }
2619
2620 /* The background passed to libpng, however, must be the
2621 * output (normally sRGB) value.
2622 */
2623 c.index = 0; /*unused*/
2624 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2625
2626 /* NOTE: the following is apparently a bug in libpng. Without
2627 * it the transparent color recognition in
2628 * png_set_background_fixed seems to go wrong.
2629 */
2630 expand_tRNS = 1;
2631 png_set_background_fixed(png_ptr, &c,
2632 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2633 0/*gamma: not used*/);
2634 }
2635
2636 output_processing = PNG_CMAP_NONE;
2637 }
2638 }
2639
2640 else /* output is color */
2641 {
2642 /* We could use png_quantize here so long as there is no transparent
2643 * color or alpha; png_quantize ignores alpha. Easier overall just
2644 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2645 * Consequently we always want libpng to produce sRGB data.
2646 */
2647 data_encoding = P_sRGB;
2648
2649 /* Is there any transparency or alpha? */
2650 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2651 png_ptr->num_trans > 0)
2652 {
2653 /* Is there alpha in the output too? If so all four channels are
2654 * processed into a special RGB cube with alpha support.
2655 */
2656 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2657 {
2658 png_uint_32 r;
2659
2660 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2661 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2662
2663 cmap_entries = (unsigned int)make_rgb_colormap(display);
2664
2665 /* Add a transparent entry. */
2666 png_create_colormap_entry(display, cmap_entries, 255, 255,
2667 255, 0, P_sRGB);
2668
2669 /* This is stored as the background index for the processing
2670 * algorithm.
2671 */
2672 background_index = cmap_entries++;
2673
2674 /* Add 27 r,g,b entries each with alpha 0.5. */
2675 for (r=0; r<256; r = (r << 1) | 0x7f)
2676 {
2677 png_uint_32 g;
2678
2679 for (g=0; g<256; g = (g << 1) | 0x7f)
2680 {
2681 png_uint_32 b;
2682
2683 /* This generates components with the values 0, 127 and
2684 * 255
2685 */
2686 for (b=0; b<256; b = (b << 1) | 0x7f)
2687 png_create_colormap_entry(display, cmap_entries++,
2688 r, g, b, 128, P_sRGB);
2689 }
2690 }
2691
2692 expand_tRNS = 1;
2693 output_processing = PNG_CMAP_RGB_ALPHA;
2694 }
2695
2696 else
2697 {
2698 /* Alpha/transparency must be removed. The background must
2699 * exist in the color map (achieved by setting adding it after
2700 * the 666 color-map). If the standard processing code will
2701 * pick up this entry automatically that's all that is
2702 * required; libpng can be called to do the background
2703 * processing.
2704 */
2705 unsigned int sample_size =
2706 PNG_IMAGE_SAMPLE_SIZE(output_format);
2707 png_uint_32 r, g, b; /* sRGB background */
2708
2709 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2710 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2711
2712 cmap_entries = (unsigned int)make_rgb_colormap(display);
2713
2714 png_create_colormap_entry(display, cmap_entries, back_r,
2715 back_g, back_b, 0/*unused*/, output_encoding);
2716
2717 if (output_encoding == P_LINEAR)
2718 {
2719 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2720 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2721 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2722 }
2723
2724 else
2725 {
2726 r = back_r;
2727 g = back_g;
2728 b = back_g;
2729 }
2730
2731 /* Compare the newly-created color-map entry with the one the
2732 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2733 * match, add the new one and set this as the background
2734 * index.
2735 */
2736 if (memcmp((png_const_bytep)display->colormap +
2737 sample_size * cmap_entries,
2738 (png_const_bytep)display->colormap +
2739 sample_size * PNG_RGB_INDEX(r,g,b),
2740 sample_size) != 0)
2741 {
2742 /* The background color must be added. */
2743 background_index = cmap_entries++;
2744
2745 /* Add 27 r,g,b entries each with created by composing with
2746 * the background at alpha 0.5.
2747 */
2748 for (r=0; r<256; r = (r << 1) | 0x7f)
2749 {
2750 for (g=0; g<256; g = (g << 1) | 0x7f)
2751 {
2752 /* This generates components with the values 0, 127
2753 * and 255
2754 */
2755 for (b=0; b<256; b = (b << 1) | 0x7f)
2756 png_create_colormap_entry(display, cmap_entries++,
2757 png_colormap_compose(display, r, P_sRGB, 128,
2758 back_r, output_encoding),
2759 png_colormap_compose(display, g, P_sRGB, 128,
2760 back_g, output_encoding),
2761 png_colormap_compose(display, b, P_sRGB, 128,
2762 back_b, output_encoding),
2763 0/*unused*/, output_encoding);
2764 }
2765 }
2766
2767 expand_tRNS = 1;
2768 output_processing = PNG_CMAP_RGB_ALPHA;
2769 }
2770
2771 else /* background color is in the standard color-map */
2772 {
2773 png_color_16 c;
2774
2775 c.index = 0; /*unused*/
2776 c.red = (png_uint_16)back_r;
2777 c.gray = c.green = (png_uint_16)back_g;
2778 c.blue = (png_uint_16)back_b;
2779
2780 png_set_background_fixed(png_ptr, &c,
2781 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2782 0/*gamma: not used*/);
2783
2784 output_processing = PNG_CMAP_RGB;
2785 }
2786 }
2787 }
2788
2789 else /* no alpha or transparency in the input */
2790 {
2791 /* Alpha in the output is irrelevant, simply map the opaque input
2792 * pixels to the 6x6x6 color-map.
2793 */
2794 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2795 png_error(png_ptr, "rgb color-map: too few entries");
2796
2797 cmap_entries = (unsigned int)make_rgb_colormap(display);
2798 output_processing = PNG_CMAP_RGB;
2799 }
2800 }
2801 break;
2802
2803 case PNG_COLOR_TYPE_PALETTE:
2804 /* It's already got a color-map. It may be necessary to eliminate the
2805 * tRNS entries though.
2806 */
2807 {
2808 unsigned int num_trans = png_ptr->num_trans;
2809 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2810 png_const_colorp colormap = png_ptr->palette;
2811 int do_background = trans != NULL &&
2812 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2813 unsigned int i;
2814
2815 /* Just in case: */
2816 if (trans == NULL)
2817 num_trans = 0;
2818
2819 output_processing = PNG_CMAP_NONE;
2820 data_encoding = P_FILE; /* Don't change from color-map indices */
2821 cmap_entries = (unsigned int)png_ptr->num_palette;
2822 if (cmap_entries > 256)
2823 cmap_entries = 256;
2824
2825 if (cmap_entries > (unsigned int)image->colormap_entries)
2826 png_error(png_ptr, "palette color-map: too few entries");
2827
2828 for (i=0; i < cmap_entries; ++i)
2829 {
2830 if (do_background != 0 && i < num_trans && trans[i] < 255)
2831 {
2832 if (trans[i] == 0)
2833 png_create_colormap_entry(display, i, back_r, back_g,
2834 back_b, 0, output_encoding);
2835
2836 else
2837 {
2838 /* Must compose the PNG file color in the color-map entry
2839 * on the sRGB color in 'back'.
2840 */
2841 png_create_colormap_entry(display, i,
2842 png_colormap_compose(display, colormap[i].red,
2843 P_FILE, trans[i], back_r, output_encoding),
2844 png_colormap_compose(display, colormap[i].green,
2845 P_FILE, trans[i], back_g, output_encoding),
2846 png_colormap_compose(display, colormap[i].blue,
2847 P_FILE, trans[i], back_b, output_encoding),
2848 output_encoding == P_LINEAR ? trans[i] * 257U :
2849 trans[i],
2850 output_encoding);
2851 }
2852 }
2853
2854 else
2855 png_create_colormap_entry(display, i, colormap[i].red,
2856 colormap[i].green, colormap[i].blue,
2857 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2858 }
2859
2860 /* The PNG data may have indices packed in fewer than 8 bits, it
2861 * must be expanded if so.
2862 */
2863 if (png_ptr->bit_depth < 8)
2864 png_set_packing(png_ptr);
2865 }
2866 break;
2867
2868 default:
2869 png_error(png_ptr, "invalid PNG color type");
2870 /*NOT REACHED*/
2871 }
2872
2873 /* Now deal with the output processing */
2874 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2875 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2876 png_set_tRNS_to_alpha(png_ptr);
2877
2878 switch (data_encoding)
2879 {
2880 case P_sRGB:
2881 /* Change to 8-bit sRGB */
2882 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2883 /* FALLTHROUGH */
2884
2885 case P_FILE:
2886 if (png_ptr->bit_depth > 8)
2887 png_set_scale_16(png_ptr);
2888 break;
2889
2890#ifdef __GNUC__
2891 default:
2892 png_error(png_ptr, "bad data option (internal error)");
2893#endif
2894 }
2895
2896 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2897 png_error(png_ptr, "color map overflow (BAD internal error)");
2898
2899 image->colormap_entries = cmap_entries;
2900
2901 /* Double check using the recorded background index */
2902 switch (output_processing)
2903 {
2904 case PNG_CMAP_NONE:
2905 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2906 goto bad_background;
2907 break;
2908
2909 case PNG_CMAP_GA:
2910 if (background_index != PNG_CMAP_GA_BACKGROUND)
2911 goto bad_background;
2912 break;
2913
2914 case PNG_CMAP_TRANS:
2915 if (background_index >= cmap_entries ||
2916 background_index != PNG_CMAP_TRANS_BACKGROUND)
2917 goto bad_background;
2918 break;
2919
2920 case PNG_CMAP_RGB:
2921 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2922 goto bad_background;
2923 break;
2924
2925 case PNG_CMAP_RGB_ALPHA:
2926 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2927 goto bad_background;
2928 break;
2929
2930 default:
2931 png_error(png_ptr, "bad processing option (internal error)");
2932
2933 bad_background:
2934 png_error(png_ptr, "bad background index (internal error)");
2935 }
2936
2937 display->colormap_processing = (int)output_processing;
2938
2939 return 1/*ok*/;
2940}
2941
2942/* The final part of the color-map read called from png_image_finish_read. */
2943static int
2944png_image_read_and_map(png_voidp argument)
2945{
2946 png_image_read_control *display = png_voidcast(png_image_read_control*,
2947 argument);
2948 png_imagep image = display->image;
2949 png_structrp png_ptr = image->opaque->png_ptr;
2950 int passes;
2951
2952 /* Called when the libpng data must be transformed into the color-mapped
2953 * form. There is a local row buffer in display->local and this routine must
2954 * do the interlace handling.
2955 */
2956 switch (png_ptr->interlaced)
2957 {
2958 case PNG_INTERLACE_NONE:
2959 passes = 1;
2960 break;
2961
2962 case PNG_INTERLACE_ADAM7:
2963 passes = PNG_INTERLACE_ADAM7_PASSES;
2964 break;
2965
2966 default:
2967 png_error(png_ptr, "unknown interlace type");
2968 }
2969
2970 {
2971 png_uint_32 height = image->height;
2972 png_uint_32 width = image->width;
2973 int proc = display->colormap_processing;
2974 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2975 ptrdiff_t step_row = display->row_bytes;
2976 int pass;
2977
2978 for (pass = 0; pass < passes; ++pass)
2979 {
2980 unsigned int startx, stepx, stepy;
2981 png_uint_32 y;
2982
2983 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2984 {
2985 /* The row may be empty for a short image: */
2986 if (PNG_PASS_COLS(width, pass) == 0)
2987 continue;
2988
2989 startx = PNG_PASS_START_COL(pass);
2990 stepx = PNG_PASS_COL_OFFSET(pass);
2991 y = PNG_PASS_START_ROW(pass);
2992 stepy = PNG_PASS_ROW_OFFSET(pass);
2993 }
2994
2995 else
2996 {
2997 y = 0;
2998 startx = 0;
2999 stepx = stepy = 1;
3000 }
3001
3002 for (; y<height; y += stepy)
3003 {
3004 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3005 png_bytep outrow = first_row + y * step_row;
3006 png_const_bytep end_row = outrow + width;
3007
3008 /* Read read the libpng data into the temporary buffer. */
3009 png_read_row(png_ptr, inrow, NULL);
3010
3011 /* Now process the row according to the processing option, note
3012 * that the caller verifies that the format of the libpng output
3013 * data is as required.
3014 */
3015 outrow += startx;
3016 switch (proc)
3017 {
3018 case PNG_CMAP_GA:
3019 for (; outrow < end_row; outrow += stepx)
3020 {
3021 /* The data is always in the PNG order */
3022 unsigned int gray = *inrow++;
3023 unsigned int alpha = *inrow++;
3024 unsigned int entry;
3025
3026 /* NOTE: this code is copied as a comment in
3027 * make_ga_colormap above. Please update the
3028 * comment if you change this code!
3029 */
3030 if (alpha > 229) /* opaque */
3031 {
3032 entry = (231 * gray + 128) >> 8;
3033 }
3034 else if (alpha < 26) /* transparent */
3035 {
3036 entry = 231;
3037 }
3038 else /* partially opaque */
3039 {
3040 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3041 }
3042
3043 *outrow = (png_byte)entry;
3044 }
3045 break;
3046
3047 case PNG_CMAP_TRANS:
3048 for (; outrow < end_row; outrow += stepx)
3049 {
3050 png_byte gray = *inrow++;
3051 png_byte alpha = *inrow++;
3052
3053 if (alpha == 0)
3054 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3055
3056 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3057 *outrow = gray;
3058
3059 else
3060 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3061 }
3062 break;
3063
3064 case PNG_CMAP_RGB:
3065 for (; outrow < end_row; outrow += stepx)
3066 {
3067 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3068 inrow += 3;
3069 }
3070 break;
3071
3072 case PNG_CMAP_RGB_ALPHA:
3073 for (; outrow < end_row; outrow += stepx)
3074 {
3075 unsigned int alpha = inrow[3];
3076
3077 /* Because the alpha entries only hold alpha==0.5 values
3078 * split the processing at alpha==0.25 (64) and 0.75
3079 * (196).
3080 */
3081
3082 if (alpha >= 196)
3083 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3084 inrow[2]);
3085
3086 else if (alpha < 64)
3087 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3088
3089 else
3090 {
3091 /* Likewise there are three entries for each of r, g
3092 * and b. We could select the entry by popcount on
3093 * the top two bits on those architectures that
3094 * support it, this is what the code below does,
3095 * crudely.
3096 */
3097 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3098
3099 /* Here are how the values map:
3100 *
3101 * 0x00 .. 0x3f -> 0
3102 * 0x40 .. 0xbf -> 1
3103 * 0xc0 .. 0xff -> 2
3104 *
3105 * So, as above with the explicit alpha checks, the
3106 * breakpoints are at 64 and 196.
3107 */
3108 if (inrow[0] & 0x80) back_i += 9; /* red */
3109 if (inrow[0] & 0x40) back_i += 9;
3110 if (inrow[0] & 0x80) back_i += 3; /* green */
3111 if (inrow[0] & 0x40) back_i += 3;
3112 if (inrow[0] & 0x80) back_i += 1; /* blue */
3113 if (inrow[0] & 0x40) back_i += 1;
3114
3115 *outrow = (png_byte)back_i;
3116 }
3117
3118 inrow += 4;
3119 }
3120 break;
3121
3122 default:
3123 break;
3124 }
3125 }
3126 }
3127 }
3128
3129 return 1;
3130}
3131
3132static int
3133png_image_read_colormapped(png_voidp argument)
3134{
3135 png_image_read_control *display = png_voidcast(png_image_read_control*,
3136 argument);
3137 png_imagep image = display->image;
3138 png_controlp control = image->opaque;
3139 png_structrp png_ptr = control->png_ptr;
3140 png_inforp info_ptr = control->info_ptr;
3141
3142 int passes = 0; /* As a flag */
3143
3144 PNG_SKIP_CHUNKS(png_ptr);
3145
3146 /* Update the 'info' structure and make sure the result is as required; first
3147 * make sure to turn on the interlace handling if it will be required
3148 * (because it can't be turned on *after* the call to png_read_update_info!)
3149 */
3150 if (display->colormap_processing == PNG_CMAP_NONE)
3151 passes = png_set_interlace_handling(png_ptr);
3152
3153 png_read_update_info(png_ptr, info_ptr);
3154
3155 /* The expected output can be deduced from the colormap_processing option. */
3156 switch (display->colormap_processing)
3157 {
3158 case PNG_CMAP_NONE:
3159 /* Output must be one channel and one byte per pixel, the output
3160 * encoding can be anything.
3161 */
3162 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3163 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3164 info_ptr->bit_depth == 8)
3165 break;
3166
3167 goto bad_output;
3168
3169 case PNG_CMAP_TRANS:
3170 case PNG_CMAP_GA:
3171 /* Output must be two channels and the 'G' one must be sRGB, the latter
3172 * can be checked with an exact number because it should have been set
3173 * to this number above!
3174 */
3175 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3176 info_ptr->bit_depth == 8 &&
3177 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3178 image->colormap_entries == 256)
3179 break;
3180
3181 goto bad_output;
3182
3183 case PNG_CMAP_RGB:
3184 /* Output must be 8-bit sRGB encoded RGB */
3185 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3186 info_ptr->bit_depth == 8 &&
3187 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3188 image->colormap_entries == 216)
3189 break;
3190
3191 goto bad_output;
3192
3193 case PNG_CMAP_RGB_ALPHA:
3194 /* Output must be 8-bit sRGB encoded RGBA */
3195 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3196 info_ptr->bit_depth == 8 &&
3197 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3198 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3199 break;
3200
3201 goto bad_output;
3202
3203 default:
3204 bad_output:
3205 png_error(png_ptr, "bad color-map processing (internal error)");
3206 }
3207
3208 /* Now read the rows. Do this here if it is possible to read directly into
3209 * the output buffer, otherwise allocate a local row buffer of the maximum
3210 * size libpng requires and call the relevant processing routine safely.
3211 */
3212 {
3213 png_voidp first_row = display->buffer;
3214 ptrdiff_t row_bytes = display->row_stride;
3215
3216 /* The following expression is designed to work correctly whether it gives
3217 * a signed or an unsigned result.
3218 */
3219 if (row_bytes < 0)
3220 {
3221 char *ptr = png_voidcast(char*, first_row);
3222 ptr += (image->height-1) * (-row_bytes);
3223 first_row = png_voidcast(png_voidp, ptr);
3224 }
3225
3226 display->first_row = first_row;
3227 display->row_bytes = row_bytes;
3228 }
3229
3230 if (passes == 0)
3231 {
3232 int result;
3233 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3234
3235 display->local_row = row;
3236 result = png_safe_execute(image, png_image_read_and_map, display);
3237 display->local_row = NULL;
3238 png_free(png_ptr, row);
3239
3240 return result;
3241 }
3242
3243 else
3244 {
3245 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
3246
3247 while (--passes >= 0)
3248 {
3249 png_uint_32 y = image->height;
3250 png_bytep row = png_voidcast(png_bytep, display->first_row);
3251
3252 for (; y > 0; --y)
3253 {
3254 png_read_row(png_ptr, row, NULL);
3255 row += row_bytes;
3256 }
3257 }
3258
3259 return 1;
3260 }
3261}
3262
3263/* Just the row reading part of png_image_read. */
3264static int
3265png_image_read_composite(png_voidp argument)
3266{
3267 png_image_read_control *display = png_voidcast(png_image_read_control*,
3268 argument);
3269 png_imagep image = display->image;
3270 png_structrp png_ptr = image->opaque->png_ptr;
3271 int passes;
3272
3273 switch (png_ptr->interlaced)
3274 {
3275 case PNG_INTERLACE_NONE:
3276 passes = 1;
3277 break;
3278
3279 case PNG_INTERLACE_ADAM7:
3280 passes = PNG_INTERLACE_ADAM7_PASSES;
3281 break;
3282
3283 default:
3284 png_error(png_ptr, "unknown interlace type");
3285 }
3286
3287 {
3288 png_uint_32 height = image->height;
3289 png_uint_32 width = image->width;
3290 ptrdiff_t step_row = display->row_bytes;
3291 unsigned int channels =
3292 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3293 int pass;
3294
3295 for (pass = 0; pass < passes; ++pass)
3296 {
3297 unsigned int startx, stepx, stepy;
3298 png_uint_32 y;
3299
3300 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3301 {
3302 /* The row may be empty for a short image: */
3303 if (PNG_PASS_COLS(width, pass) == 0)
3304 continue;
3305
3306 startx = PNG_PASS_START_COL(pass) * channels;
3307 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3308 y = PNG_PASS_START_ROW(pass);
3309 stepy = PNG_PASS_ROW_OFFSET(pass);
3310 }
3311
3312 else
3313 {
3314 y = 0;
3315 startx = 0;
3316 stepx = channels;
3317 stepy = 1;
3318 }
3319
3320 for (; y<height; y += stepy)
3321 {
3322 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3323 png_bytep outrow;
3324 png_const_bytep end_row;
3325
3326 /* Read the row, which is packed: */
3327 png_read_row(png_ptr, inrow, NULL);
3328
3329 outrow = png_voidcast(png_bytep, display->first_row);
3330 outrow += y * step_row;
3331 end_row = outrow + width * channels;
3332
3333 /* Now do the composition on each pixel in this row. */
3334 outrow += startx;
3335 for (; outrow < end_row; outrow += stepx)
3336 {
3337 png_byte alpha = inrow[channels];
3338
3339 if (alpha > 0) /* else no change to the output */
3340 {
3341 unsigned int c;
3342
3343 for (c=0; c<channels; ++c)
3344 {
3345 png_uint_32 component = inrow[c];
3346
3347 if (alpha < 255) /* else just use component */
3348 {
3349 /* This is PNG_OPTIMIZED_ALPHA, the component value
3350 * is a linear 8-bit value. Combine this with the
3351 * current outrow[c] value which is sRGB encoded.
3352 * Arithmetic here is 16-bits to preserve the output
3353 * values correctly.
3354 */
3355 component *= 257*255; /* =65535 */
3356 component += (255-alpha)*png_sRGB_table[outrow[c]];
3357
3358 /* So 'component' is scaled by 255*65535 and is
3359 * therefore appropriate for the sRGB to linear
3360 * conversion table.
3361 */
3362 component = PNG_sRGB_FROM_LINEAR(component);
3363 }
3364
3365 outrow[c] = (png_byte)component;
3366 }
3367 }
3368
3369 inrow += channels+1; /* components and alpha channel */
3370 }
3371 }
3372 }
3373 }
3374
3375 return 1;
3376}
3377
3378/* The do_local_background case; called when all the following transforms are to
3379 * be done:
3380 *
3381 * PNG_RGB_TO_GRAY
3382 * PNG_COMPOSITE
3383 * PNG_GAMMA
3384 *
3385 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3386 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3387 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3388 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3389 * row and handles the removal or pre-multiplication of the alpha channel.
3390 */
3391static int
3392png_image_read_background(png_voidp argument)
3393{
3394 png_image_read_control *display = png_voidcast(png_image_read_control*,
3395 argument);
3396 png_imagep image = display->image;
3397 png_structrp png_ptr = image->opaque->png_ptr;
3398 png_inforp info_ptr = image->opaque->info_ptr;
3399 png_uint_32 height = image->height;
3400 png_uint_32 width = image->width;
3401 int pass, passes;
3402
3403 /* Double check the convoluted logic below. We expect to get here with
3404 * libpng doing rgb to gray and gamma correction but background processing
3405 * left to the png_image_read_background function. The rows libpng produce
3406 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3407 */
3408 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3409 png_error(png_ptr, "lost rgb to gray");
3410
3411 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3412 png_error(png_ptr, "unexpected compose");
3413
3414 if (png_get_channels(png_ptr, info_ptr) != 2)
3415 png_error(png_ptr, "lost/gained channels");
3416
3417 /* Expect the 8-bit case to always remove the alpha channel */
3418 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3419 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3420 png_error(png_ptr, "unexpected 8-bit transformation");
3421
3422 switch (png_ptr->interlaced)
3423 {
3424 case PNG_INTERLACE_NONE:
3425 passes = 1;
3426 break;
3427
3428 case PNG_INTERLACE_ADAM7:
3429 passes = PNG_INTERLACE_ADAM7_PASSES;
3430 break;
3431
3432 default:
3433 png_error(png_ptr, "unknown interlace type");
3434 }
3435
3436 /* Use direct access to info_ptr here because otherwise the simplified API
3437 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3438 * checking the value after libpng expansions, not the original value in the
3439 * PNG.
3440 */
3441 switch (info_ptr->bit_depth)
3442 {
3443 case 8:
3444 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3445 * to be removed by composing on a background: either the row if
3446 * display->background is NULL or display->background->green if not.
3447 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3448 */
3449 {
3450 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3451 ptrdiff_t step_row = display->row_bytes;
3452
3453 for (pass = 0; pass < passes; ++pass)
3454 {
3455 png_bytep row = png_voidcast(png_bytep, display->first_row);
3456 unsigned int startx, stepx, stepy;
3457 png_uint_32 y;
3458
3459 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3460 {
3461 /* The row may be empty for a short image: */
3462 if (PNG_PASS_COLS(width, pass) == 0)
3463 continue;
3464
3465 startx = PNG_PASS_START_COL(pass);
3466 stepx = PNG_PASS_COL_OFFSET(pass);
3467 y = PNG_PASS_START_ROW(pass);
3468 stepy = PNG_PASS_ROW_OFFSET(pass);
3469 }
3470
3471 else
3472 {
3473 y = 0;
3474 startx = 0;
3475 stepx = stepy = 1;
3476 }
3477
3478 if (display->background == NULL)
3479 {
3480 for (; y<height; y += stepy)
3481 {
3482 png_bytep inrow = png_voidcast(png_bytep,
3483 display->local_row);
3484 png_bytep outrow = first_row + y * step_row;
3485 png_const_bytep end_row = outrow + width;
3486
3487 /* Read the row, which is packed: */
3488 png_read_row(png_ptr, inrow, NULL);
3489
3490 /* Now do the composition on each pixel in this row. */
3491 outrow += startx;
3492 for (; outrow < end_row; outrow += stepx)
3493 {
3494 png_byte alpha = inrow[1];
3495
3496 if (alpha > 0) /* else no change to the output */
3497 {
3498 png_uint_32 component = inrow[0];
3499
3500 if (alpha < 255) /* else just use component */
3501 {
3502 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3503 * necessary to invert the sRGB transfer
3504 * function and multiply the alpha out.
3505 */
3506 component = png_sRGB_table[component] * alpha;
3507 component += png_sRGB_table[outrow[0]] *
3508 (255-alpha);
3509 component = PNG_sRGB_FROM_LINEAR(component);
3510 }
3511
3512 outrow[0] = (png_byte)component;
3513 }
3514
3515 inrow += 2; /* gray and alpha channel */
3516 }
3517 }
3518 }
3519
3520 else /* constant background value */
3521 {
3522 png_byte background8 = display->background->green;
3523 png_uint_16 background = png_sRGB_table[background8];
3524
3525 for (; y<height; y += stepy)
3526 {
3527 png_bytep inrow = png_voidcast(png_bytep,
3528 display->local_row);
3529 png_bytep outrow = first_row + y * step_row;
3530 png_const_bytep end_row = outrow + width;
3531
3532 /* Read the row, which is packed: */
3533 png_read_row(png_ptr, inrow, NULL);
3534
3535 /* Now do the composition on each pixel in this row. */
3536 outrow += startx;
3537 for (; outrow < end_row; outrow += stepx)
3538 {
3539 png_byte alpha = inrow[1];
3540
3541 if (alpha > 0) /* else use background */
3542 {
3543 png_uint_32 component = inrow[0];
3544
3545 if (alpha < 255) /* else just use component */
3546 {
3547 component = png_sRGB_table[component] * alpha;
3548 component += background * (255-alpha);
3549 component = PNG_sRGB_FROM_LINEAR(component);
3550 }
3551
3552 outrow[0] = (png_byte)component;
3553 }
3554
3555 else
3556 outrow[0] = background8;
3557
3558 inrow += 2; /* gray and alpha channel */
3559 }
3560
3561 row += display->row_bytes;
3562 }
3563 }
3564 }
3565 }
3566 break;
3567
3568 case 16:
3569 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3570 * still be done and, maybe, the alpha channel removed. This code also
3571 * handles the alpha-first option.
3572 */
3573 {
3574 png_uint_16p first_row = png_voidcast(png_uint_16p,
3575 display->first_row);
3576 /* The division by two is safe because the caller passed in a
3577 * stride which was multiplied by 2 (below) to get row_bytes.
3578 */
3579 ptrdiff_t step_row = display->row_bytes / 2;
3580 unsigned int preserve_alpha = (image->format &
3581 PNG_FORMAT_FLAG_ALPHA) != 0;
3582 unsigned int outchannels = 1U+preserve_alpha;
3583 int swap_alpha = 0;
3584
3585# ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3586 if (preserve_alpha != 0 &&
3587 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3588 swap_alpha = 1;
3589# endif
3590
3591 for (pass = 0; pass < passes; ++pass)
3592 {
3593 unsigned int startx, stepx, stepy;
3594 png_uint_32 y;
3595
3596 /* The 'x' start and step are adjusted to output components here.
3597 */
3598 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3599 {
3600 /* The row may be empty for a short image: */
3601 if (PNG_PASS_COLS(width, pass) == 0)
3602 continue;
3603
3604 startx = PNG_PASS_START_COL(pass) * outchannels;
3605 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3606 y = PNG_PASS_START_ROW(pass);
3607 stepy = PNG_PASS_ROW_OFFSET(pass);
3608 }
3609
3610 else
3611 {
3612 y = 0;
3613 startx = 0;
3614 stepx = outchannels;
3615 stepy = 1;
3616 }
3617
3618 for (; y<height; y += stepy)
3619 {
3620 png_const_uint_16p inrow;
3621 png_uint_16p outrow = first_row + y*step_row;
3622 png_uint_16p end_row = outrow + width * outchannels;
3623
3624 /* Read the row, which is packed: */
3625 png_read_row(png_ptr, png_voidcast(png_bytep,
3626 display->local_row), NULL);
3627 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3628
3629 /* Now do the pre-multiplication on each pixel in this row.
3630 */
3631 outrow += startx;
3632 for (; outrow < end_row; outrow += stepx)
3633 {
3634 png_uint_32 component = inrow[0];
3635 png_uint_16 alpha = inrow[1];
3636
3637 if (alpha > 0) /* else 0 */
3638 {
3639 if (alpha < 65535) /* else just use component */
3640 {
3641 component *= alpha;
3642 component += 32767;
3643 component /= 65535;
3644 }
3645 }
3646
3647 else
3648 component = 0;
3649
3650 outrow[swap_alpha] = (png_uint_16)component;
3651 if (preserve_alpha != 0)
3652 outrow[1 ^ swap_alpha] = alpha;
3653
3654 inrow += 2; /* components and alpha channel */
3655 }
3656 }
3657 }
3658 }
3659 break;
3660
3661#ifdef __GNUC__
3662 default:
3663 png_error(png_ptr, "unexpected bit depth");
3664#endif
3665 }
3666
3667 return 1;
3668}
3669
3670/* The guts of png_image_finish_read as a png_safe_execute callback. */
3671static int
3672png_image_read_direct(png_voidp argument)
3673{
3674 png_image_read_control *display = png_voidcast(png_image_read_control*,
3675 argument);
3676 png_imagep image = display->image;
3677 png_structrp png_ptr = image->opaque->png_ptr;
3678 png_inforp info_ptr = image->opaque->info_ptr;
3679
3680 png_uint_32 format = image->format;
3681 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3682 int do_local_compose = 0;
3683 int do_local_background = 0; /* to avoid double gamma correction bug */
3684 int passes = 0;
3685
3686 /* Add transforms to ensure the correct output format is produced then check
3687 * that the required implementation support is there. Always expand; always
3688 * need 8 bits minimum, no palette and expanded tRNS.
3689 */
3690 png_set_expand(png_ptr);
3691
3692 /* Now check the format to see if it was modified. */
3693 {
3694 png_uint_32 base_format = png_image_format(png_ptr) &
3695 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3696 png_uint_32 change = format ^ base_format;
3697 png_fixed_point output_gamma;
3698 int mode; /* alpha mode */
3699
3700 /* Do this first so that we have a record if rgb to gray is happening. */
3701 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3702 {
3703 /* gray<->color transformation required. */
3704 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3705 png_set_gray_to_rgb(png_ptr);
3706
3707 else
3708 {
3709 /* libpng can't do both rgb to gray and
3710 * background/pre-multiplication if there is also significant gamma
3711 * correction, because both operations require linear colors and
3712 * the code only supports one transform doing the gamma correction.
3713 * Handle this by doing the pre-multiplication or background
3714 * operation in this code, if necessary.
3715 *
3716 * TODO: fix this by rewriting pngrtran.c (!)
3717 *
3718 * For the moment (given that fixing this in pngrtran.c is an
3719 * enormous change) 'do_local_background' is used to indicate that
3720 * the problem exists.
3721 */
3722 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3723 do_local_background = 1/*maybe*/;
3724
3725 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3726 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3727 }
3728
3729 change &= ~PNG_FORMAT_FLAG_COLOR;
3730 }
3731
3732 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3733 */
3734 {
3735 png_fixed_point input_gamma_default;
3736
3737 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3738 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3739 input_gamma_default = PNG_GAMMA_LINEAR;
3740 else
3741 input_gamma_default = PNG_DEFAULT_sRGB;
3742
3743 /* Call png_set_alpha_mode to set the default for the input gamma; the
3744 * output gamma is set by a second call below.
3745 */
3746 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3747 }
3748
3749 if (linear != 0)
3750 {
3751 /* If there *is* an alpha channel in the input it must be multiplied
3752 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3753 */
3754 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3755 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3756
3757 else
3758 mode = PNG_ALPHA_PNG;
3759
3760 output_gamma = PNG_GAMMA_LINEAR;
3761 }
3762
3763 else
3764 {
3765 mode = PNG_ALPHA_PNG;
3766 output_gamma = PNG_DEFAULT_sRGB;
3767 }
3768
3769 if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0)
3770 {
3771 mode = PNG_ALPHA_OPTIMIZED;
3772 change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
3773 }
3774
3775 /* If 'do_local_background' is set check for the presence of gamma
3776 * correction; this is part of the work-round for the libpng bug
3777 * described above.
3778 *
3779 * TODO: fix libpng and remove this.
3780 */
3781 if (do_local_background != 0)
3782 {
3783 png_fixed_point gtest;
3784
3785 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3786 * gamma correction, the screen gamma hasn't been set on png_struct
3787 * yet; it's set below. png_struct::gamma, however, is set to the
3788 * final value.
3789 */
3790 if (png_muldiv(&gtest, output_gamma, png_ptr->colorspace.gamma,
3791 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3792 do_local_background = 0;
3793
3794 else if (mode == PNG_ALPHA_STANDARD)
3795 {
3796 do_local_background = 2/*required*/;
3797 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3798 }
3799
3800 /* else leave as 1 for the checks below */
3801 }
3802
3803 /* If the bit-depth changes then handle that here. */
3804 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3805 {
3806 if (linear != 0 /*16-bit output*/)
3807 png_set_expand_16(png_ptr);
3808
3809 else /* 8-bit output */
3810 png_set_scale_16(png_ptr);
3811
3812 change &= ~PNG_FORMAT_FLAG_LINEAR;
3813 }
3814
3815 /* Now the background/alpha channel changes. */
3816 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3817 {
3818 /* Removing an alpha channel requires composition for the 8-bit
3819 * formats; for the 16-bit it is already done, above, by the
3820 * pre-multiplication and the channel just needs to be stripped.
3821 */
3822 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3823 {
3824 /* If RGB->gray is happening the alpha channel must be left and the
3825 * operation completed locally.
3826 *
3827 * TODO: fix libpng and remove this.
3828 */
3829 if (do_local_background != 0)
3830 do_local_background = 2/*required*/;
3831
3832 /* 16-bit output: just remove the channel */
3833 else if (linear != 0) /* compose on black (well, pre-multiply) */
3834 png_set_strip_alpha(png_ptr);
3835
3836 /* 8-bit output: do an appropriate compose */
3837 else if (display->background != NULL)
3838 {
3839 png_color_16 c;
3840
3841 c.index = 0; /*unused*/
3842 c.red = display->background->red;
3843 c.green = display->background->green;
3844 c.blue = display->background->blue;
3845 c.gray = display->background->green;
3846
3847 /* This is always an 8-bit sRGB value, using the 'green' channel
3848 * for gray is much better than calculating the luminance here;
3849 * we can get off-by-one errors in that calculation relative to
3850 * the app expectations and that will show up in transparent
3851 * pixels.
3852 */
3853 png_set_background_fixed(png_ptr, &c,
3854 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3855 0/*gamma: not used*/);
3856 }
3857
3858 else /* compose on row: implemented below. */
3859 {
3860 do_local_compose = 1;
3861 /* This leaves the alpha channel in the output, so it has to be
3862 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3863 * one so the code only has to hack on the pixels that require
3864 * composition.
3865 */
3866 mode = PNG_ALPHA_OPTIMIZED;
3867 }
3868 }
3869
3870 else /* output needs an alpha channel */
3871 {
3872 /* This is tricky because it happens before the swap operation has
3873 * been accomplished; however, the swap does *not* swap the added
3874 * alpha channel (weird API), so it must be added in the correct
3875 * place.
3876 */
3877 png_uint_32 filler; /* opaque filler */
3878 int where;
3879
3880 if (linear != 0)
3881 filler = 65535;
3882
3883 else
3884 filler = 255;
3885
3886#ifdef PNG_FORMAT_AFIRST_SUPPORTED
3887 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3888 {
3889 where = PNG_FILLER_BEFORE;
3890 change &= ~PNG_FORMAT_FLAG_AFIRST;
3891 }
3892
3893 else
3894#endif
3895 where = PNG_FILLER_AFTER;
3896
3897 png_set_add_alpha(png_ptr, filler, where);
3898 }
3899
3900 /* This stops the (irrelevant) call to swap_alpha below. */
3901 change &= ~PNG_FORMAT_FLAG_ALPHA;
3902 }
3903
3904 /* Now set the alpha mode correctly; this is always done, even if there is
3905 * no alpha channel in either the input or the output because it correctly
3906 * sets the output gamma.
3907 */
3908 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3909
3910# ifdef PNG_FORMAT_BGR_SUPPORTED
3911 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3912 {
3913 /* Check only the output format; PNG is never BGR; don't do this if
3914 * the output is gray, but fix up the 'format' value in that case.
3915 */
3916 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3917 png_set_bgr(png_ptr);
3918
3919 else
3920 format &= ~PNG_FORMAT_FLAG_BGR;
3921
3922 change &= ~PNG_FORMAT_FLAG_BGR;
3923 }
3924# endif
3925
3926# ifdef PNG_FORMAT_AFIRST_SUPPORTED
3927 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3928 {
3929 /* Only relevant if there is an alpha channel - it's particularly
3930 * important to handle this correctly because do_local_compose may
3931 * be set above and then libpng will keep the alpha channel for this
3932 * code to remove.
3933 */
3934 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3935 {
3936 /* Disable this if doing a local background,
3937 * TODO: remove this when local background is no longer required.
3938 */
3939 if (do_local_background != 2)
3940 png_set_swap_alpha(png_ptr);
3941 }
3942
3943 else
3944 format &= ~PNG_FORMAT_FLAG_AFIRST;
3945
3946 change &= ~PNG_FORMAT_FLAG_AFIRST;
3947 }
3948# endif
3949
3950 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3951 * architecture.
3952 */
3953 if (linear != 0)
3954 {
3955 png_uint_16 le = 0x0001;
3956
3957 if ((*(png_const_bytep) & le) != 0)
3958 png_set_swap(png_ptr);
3959 }
3960
3961 /* If change is not now 0 some transformation is missing - error out. */
3962 if (change != 0)
3963 png_error(png_ptr, "png_read_image: unsupported transformation");
3964 }
3965
3966 PNG_SKIP_CHUNKS(png_ptr);
3967
3968 /* Update the 'info' structure and make sure the result is as required; first
3969 * make sure to turn on the interlace handling if it will be required
3970 * (because it can't be turned on *after* the call to png_read_update_info!)
3971 *
3972 * TODO: remove the do_local_background fixup below.
3973 */
3974 if (do_local_compose == 0 && do_local_background != 2)
3975 passes = png_set_interlace_handling(png_ptr);
3976
3977 png_read_update_info(png_ptr, info_ptr);
3978
3979 {
3980 png_uint_32 info_format = 0;
3981
3982 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
3983 info_format |= PNG_FORMAT_FLAG_COLOR;
3984
3985 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
3986 {
3987 /* do_local_compose removes this channel below. */
3988 if (do_local_compose == 0)
3989 {
3990 /* do_local_background does the same if required. */
3991 if (do_local_background != 2 ||
3992 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
3993 info_format |= PNG_FORMAT_FLAG_ALPHA;
3994 }
3995 }
3996
3997 else if (do_local_compose != 0) /* internal error */
3998 png_error(png_ptr, "png_image_read: alpha channel lost");
3999
4000 if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) {
4001 info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
4002 }
4003
4004 if (info_ptr->bit_depth == 16)
4005 info_format |= PNG_FORMAT_FLAG_LINEAR;
4006
4007#ifdef PNG_FORMAT_BGR_SUPPORTED
4008 if ((png_ptr->transformations & PNG_BGR) != 0)
4009 info_format |= PNG_FORMAT_FLAG_BGR;
4010#endif
4011
4012#ifdef PNG_FORMAT_AFIRST_SUPPORTED
4013 if (do_local_background == 2)
4014 {
4015 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4016 info_format |= PNG_FORMAT_FLAG_AFIRST;
4017 }
4018
4019 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4020 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4021 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4022 {
4023 if (do_local_background == 2)
4024 png_error(png_ptr, "unexpected alpha swap transformation");
4025
4026 info_format |= PNG_FORMAT_FLAG_AFIRST;
4027 }
4028# endif
4029
4030 /* This is actually an internal error. */
4031 if (info_format != format)
4032 png_error(png_ptr, "png_read_image: invalid transformations");
4033 }
4034
4035 /* Now read the rows. If do_local_compose is set then it is necessary to use
4036 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4037 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4038 * display acts as a flag.
4039 */
4040 {
4041 png_voidp first_row = display->buffer;
4042 ptrdiff_t row_bytes = display->row_stride;
4043
4044 if (linear != 0)
4045 row_bytes *= 2;
4046
4047 /* The following expression is designed to work correctly whether it gives
4048 * a signed or an unsigned result.
4049 */
4050 if (row_bytes < 0)
4051 {
4052 char *ptr = png_voidcast(char*, first_row);
4053 ptr += (image->height-1) * (-row_bytes);
4054 first_row = png_voidcast(png_voidp, ptr);
4055 }
4056
4057 display->first_row = first_row;
4058 display->row_bytes = row_bytes;
4059 }
4060
4061 if (do_local_compose != 0)
4062 {
4063 int result;
4064 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4065
4066 display->local_row = row;
4067 result = png_safe_execute(image, png_image_read_composite, display);
4068 display->local_row = NULL;
4069 png_free(png_ptr, row);
4070
4071 return result;
4072 }
4073
4074 else if (do_local_background == 2)
4075 {
4076 int result;
4077 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4078
4079 display->local_row = row;
4080 result = png_safe_execute(image, png_image_read_background, display);
4081 display->local_row = NULL;
4082 png_free(png_ptr, row);
4083
4084 return result;
4085 }
4086
4087 else
4088 {
4089 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
4090
4091 while (--passes >= 0)
4092 {
4093 png_uint_32 y = image->height;
4094 png_bytep row = png_voidcast(png_bytep, display->first_row);
4095
4096 for (; y > 0; --y)
4097 {
4098 png_read_row(png_ptr, row, NULL);
4099 row += row_bytes;
4100 }
4101 }
4102
4103 return 1;
4104 }
4105}
4106
4107int PNGAPI
4108png_image_finish_read(png_imagep image, png_const_colorp background,
4109 void *buffer, png_int_32 row_stride, void *colormap)
4110{
4111 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4112 {
4113 /* Check for row_stride overflow. This check is not performed on the
4114 * original PNG format because it may not occur in the output PNG format
4115 * and libpng deals with the issues of reading the original.
4116 */
4117 unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4118
4119 /* The following checks just the 'row_stride' calculation to ensure it
4120 * fits in a signed 32-bit value. Because channels/components can be
4121 * either 1 or 2 bytes in size the length of a row can still overflow 32
4122 * bits; this is just to verify that the 'row_stride' argument can be
4123 * represented.
4124 */
4125 if (image->width <= 0x7fffffffU/channels) /* no overflow */
4126 {
4127 png_uint_32 check;
4128 png_uint_32 png_row_stride = image->width * channels;
4129
4130 if (row_stride == 0)
4131 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4132
4133 if (row_stride < 0)
4134 check = (png_uint_32)(-row_stride);
4135
4136 else
4137 check = (png_uint_32)row_stride;
4138
4139 /* This verifies 'check', the absolute value of the actual stride
4140 * passed in and detects overflow in the application calculation (i.e.
4141 * if the app did actually pass in a non-zero 'row_stride'.
4142 */
4143 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4144 {
4145 /* Now check for overflow of the image buffer calculation; this
4146 * limits the whole image size to 32 bits for API compatibility with
4147 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4148 *
4149 * The PNG_IMAGE_BUFFER_SIZE macro is:
4150 *
4151 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4152 *
4153 * And the component size is always 1 or 2, so make sure that the
4154 * number of *bytes* that the application is saying are available
4155 * does actually fit into a 32-bit number.
4156 *
4157 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4158 * will be changed to use png_alloc_size_t; bigger images can be
4159 * accommodated on 64-bit systems.
4160 */
4161 if (image->height <=
4162 0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
4163 {
4164 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4165 (image->colormap_entries > 0 && colormap != NULL))
4166 {
4167 int result;
4168 png_image_read_control display;
4169
4170 memset(&display, 0, (sizeof display));
4171 display.image = image;
4172 display.buffer = buffer;
4173 display.row_stride = row_stride;
4174 display.colormap = colormap;
4175 display.background = background;
4176 display.local_row = NULL;
4177
4178 /* Choose the correct 'end' routine; for the color-map case
4179 * all the setup has already been done.
4180 */
4181 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4182 result =
4183 png_safe_execute(image,
4184 png_image_read_colormap, &display) &&
4185 png_safe_execute(image,
4186 png_image_read_colormapped, &display);
4187
4188 else
4189 result =
4190 png_safe_execute(image,
4191 png_image_read_direct, &display);
4192
4193 png_image_free(image);
4194 return result;
4195 }
4196
4197 else
4198 return png_image_error(image,
4199 "png_image_finish_read[color-map]: no color-map");
4200 }
4201
4202 else
4203 return png_image_error(image,
4204 "png_image_finish_read: image too large");
4205 }
4206
4207 else
4208 return png_image_error(image,
4209 "png_image_finish_read: invalid argument");
4210 }
4211
4212 else
4213 return png_image_error(image,
4214 "png_image_finish_read: row_stride too large");
4215 }
4216
4217 else if (image != NULL)
4218 return png_image_error(image,
4219 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4220
4221 return 0;
4222}
4223
4224#endif /* SIMPLIFIED_READ */
4225#endif /* READ */
4226

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