1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /* pngread.c - read a PNG file
26 *
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file and, per its terms, should not be removed:
31 *
32 * Last changed in libpng 1.6.35 [July 15, 2018]
33 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
34 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
35 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
36 *
37 * This code is released under the libpng license.
38 * For conditions of distribution and use, see the disclaimer
39 * and license in png.h
40 *
41 * This file contains routines that an application calls directly to
42 * read a PNG file or stream.
43 */
44
45 #include "pngpriv.h"
46 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
47 # include <errno.h>
48 #endif
49
50 #ifdef PNG_READ_SUPPORTED
51
52 /* Create a PNG structure for reading, and allocate any memory needed. */
53 PNG_FUNCTION(png_structp,PNGAPI
54 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
55 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
56 {
57 #ifndef PNG_USER_MEM_SUPPORTED
58 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
59 error_fn, warn_fn, NULL, NULL, NULL);
60 #else
61 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
62 warn_fn, NULL, NULL, NULL);
63 }
64
65 /* Alternate create PNG structure for reading, and allocate any memory
66 * needed.
67 */
68 PNG_FUNCTION(png_structp,PNGAPI
69 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
70 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
71 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
72 {
73 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
74 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
75 #endif /* USER_MEM */
76
77 if (png_ptr != NULL)
78 {
79 png_ptr->mode = PNG_IS_READ_STRUCT;
80
81 /* Added in libpng-1.6.0; this can be used to detect a read structure if
82 * required (it will be zero in a write structure.)
83 */
84 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
85 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
86 # endif
87
88 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
89 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
90
91 /* In stable builds only warn if an application error can be completely
92 * handled.
93 */
94 # if PNG_RELEASE_BUILD
95 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
96 # endif
97 # endif
98
99 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
100 * do it itself) avoiding setting the default function if it is not
101 * required.
102 */
103 png_set_read_fn(png_ptr, NULL, NULL);
104 }
105
106 return png_ptr;
107 }
108
109
110 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
111 /* Read the information before the actual image data. This has been
112 * changed in v0.90 to allow reading a file that already has the magic
113 * bytes read from the stream. You can tell libpng how many bytes have
114 * been read from the beginning of the stream (up to the maximum of 8)
115 * via png_set_sig_bytes(), and we will only check the remaining bytes
116 * here. The application can then have access to the signature bytes we
117 * read if it is determined that this isn't a valid PNG file.
118 */
119 void PNGAPI
120 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
121 {
122 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
123 int keep;
124 #endif
125
126 png_debug(1, "in png_read_info");
127
128 if (png_ptr == NULL || info_ptr == NULL)
129 return;
130
131 /* Read and check the PNG file signature. */
132 png_read_sig(png_ptr, info_ptr);
133
134 for (;;)
135 {
136 png_uint_32 length = png_read_chunk_header(png_ptr);
137 png_uint_32 chunk_name = png_ptr->chunk_name;
138
139 /* IDAT logic needs to happen here to simplify getting the two flags
140 * right.
141 */
142 if (chunk_name == png_IDAT)
143 {
144 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
145 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
146
147 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
148 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
149 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
150
151 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
152 png_chunk_benign_error(png_ptr, "Too many IDATs found");
153
154 png_ptr->mode |= PNG_HAVE_IDAT;
155 }
156
157 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
158 {
159 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
160 png_ptr->mode |= PNG_AFTER_IDAT;
161 }
162
163 /* This should be a binary subdivision search or a hash for
164 * matching the chunk name rather than a linear search.
165 */
166 if (chunk_name == png_IHDR)
167 png_handle_IHDR(png_ptr, info_ptr, length);
168
169 else if (chunk_name == png_IEND)
170 png_handle_IEND(png_ptr, info_ptr, length);
171
172 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
173 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
174 {
175 png_handle_unknown(png_ptr, info_ptr, length, keep);
176
177 if (chunk_name == png_PLTE)
178 png_ptr->mode |= PNG_HAVE_PLTE;
179
180 else if (chunk_name == png_IDAT)
181 {
182 png_ptr->idat_size = 0; /* It has been consumed */
183 break;
184 }
185 }
186 #endif
187 else if (chunk_name == png_PLTE)
188 png_handle_PLTE(png_ptr, info_ptr, length);
189
190 else if (chunk_name == png_IDAT)
191 {
192 png_ptr->idat_size = length;
193 break;
194 }
195
196 #ifdef PNG_READ_bKGD_SUPPORTED
197 else if (chunk_name == png_bKGD)
198 png_handle_bKGD(png_ptr, info_ptr, length);
199 #endif
200
201 #ifdef PNG_READ_cHRM_SUPPORTED
202 else if (chunk_name == png_cHRM)
203 png_handle_cHRM(png_ptr, info_ptr, length);
204 #endif
205
206 #ifdef PNG_READ_eXIf_SUPPORTED
207 else if (chunk_name == png_eXIf)
208 png_handle_eXIf(png_ptr, info_ptr, length);
209 #endif
210
211 #ifdef PNG_READ_gAMA_SUPPORTED
212 else if (chunk_name == png_gAMA)
213 png_handle_gAMA(png_ptr, info_ptr, length);
214 #endif
215
216 #ifdef PNG_READ_hIST_SUPPORTED
217 else if (chunk_name == png_hIST)
218 png_handle_hIST(png_ptr, info_ptr, length);
219 #endif
220
221 #ifdef PNG_READ_oFFs_SUPPORTED
222 else if (chunk_name == png_oFFs)
223 png_handle_oFFs(png_ptr, info_ptr, length);
224 #endif
225
226 #ifdef PNG_READ_pCAL_SUPPORTED
227 else if (chunk_name == png_pCAL)
228 png_handle_pCAL(png_ptr, info_ptr, length);
229 #endif
230
231 #ifdef PNG_READ_sCAL_SUPPORTED
232 else if (chunk_name == png_sCAL)
233 png_handle_sCAL(png_ptr, info_ptr, length);
234 #endif
235
236 #ifdef PNG_READ_pHYs_SUPPORTED
237 else if (chunk_name == png_pHYs)
238 png_handle_pHYs(png_ptr, info_ptr, length);
239 #endif
240
241 #ifdef PNG_READ_sBIT_SUPPORTED
242 else if (chunk_name == png_sBIT)
243 png_handle_sBIT(png_ptr, info_ptr, length);
244 #endif
245
246 #ifdef PNG_READ_sRGB_SUPPORTED
247 else if (chunk_name == png_sRGB)
248 png_handle_sRGB(png_ptr, info_ptr, length);
249 #endif
250
251 #ifdef PNG_READ_iCCP_SUPPORTED
252 else if (chunk_name == png_iCCP)
253 png_handle_iCCP(png_ptr, info_ptr, length);
254 #endif
255
256 #ifdef PNG_READ_sPLT_SUPPORTED
257 else if (chunk_name == png_sPLT)
258 png_handle_sPLT(png_ptr, info_ptr, length);
259 #endif
260
261 #ifdef PNG_READ_tEXt_SUPPORTED
262 else if (chunk_name == png_tEXt)
263 png_handle_tEXt(png_ptr, info_ptr, length);
264 #endif
265
266 #ifdef PNG_READ_tIME_SUPPORTED
267 else if (chunk_name == png_tIME)
268 png_handle_tIME(png_ptr, info_ptr, length);
269 #endif
270
271 #ifdef PNG_READ_tRNS_SUPPORTED
272 else if (chunk_name == png_tRNS)
273 png_handle_tRNS(png_ptr, info_ptr, length);
274 #endif
275
276 #ifdef PNG_READ_zTXt_SUPPORTED
277 else if (chunk_name == png_zTXt)
278 png_handle_zTXt(png_ptr, info_ptr, length);
279 #endif
280
281 #ifdef PNG_READ_iTXt_SUPPORTED
282 else if (chunk_name == png_iTXt)
283 png_handle_iTXt(png_ptr, info_ptr, length);
284 #endif
285
286 else
287 png_handle_unknown(png_ptr, info_ptr, length,
288 PNG_HANDLE_CHUNK_AS_DEFAULT);
289 }
290 }
291 #endif /* SEQUENTIAL_READ */
292
293 /* Optional call to update the users info_ptr structure */
294 void PNGAPI
295 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
296 {
297 png_debug(1, "in png_read_update_info");
298
299 if (png_ptr != NULL)
300 {
301 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
302 {
303 png_read_start_row(png_ptr);
304
305 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
306 png_read_transform_info(png_ptr, info_ptr);
307 # else
308 PNG_UNUSED(info_ptr)
309 # endif
310 }
311
312 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
313 else
314 png_app_error(png_ptr,
315 "png_read_update_info/png_start_read_image: duplicate call");
316 }
317 }
318
319 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
320 /* Initialize palette, background, etc, after transformations
321 * are set, but before any reading takes place. This allows
322 * the user to obtain a gamma-corrected palette, for example.
323 * If the user doesn't call this, we will do it ourselves.
324 */
325 void PNGAPI
326 png_start_read_image(png_structrp png_ptr)
327 {
328 png_debug(1, "in png_start_read_image");
329
330 if (png_ptr != NULL)
331 {
332 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
333 png_read_start_row(png_ptr);
334
335 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
336 else
337 png_app_error(png_ptr,
338 "png_start_read_image/png_read_update_info: duplicate call");
339 }
340 }
341 #endif /* SEQUENTIAL_READ */
342
343 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
344 #ifdef PNG_MNG_FEATURES_SUPPORTED
345 /* Undoes intrapixel differencing,
346 * NOTE: this is apparently only supported in the 'sequential' reader.
347 */
348 static void
349 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
350 {
351 png_debug(1, "in png_do_read_intrapixel");
352
353 if (
354 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
355 {
356 int bytes_per_pixel;
357 png_uint_32 row_width = row_info->width;
358
359 if (row_info->bit_depth == 8)
360 {
361 png_bytep rp;
362 png_uint_32 i;
363
364 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
365 bytes_per_pixel = 3;
366
367 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
368 bytes_per_pixel = 4;
369
370 else
371 return;
372
373 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
374 {
375 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
376 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
377 }
378 }
379 else if (row_info->bit_depth == 16)
380 {
381 png_bytep rp;
382 png_uint_32 i;
383
384 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
385 bytes_per_pixel = 6;
386
387 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
388 bytes_per_pixel = 8;
389
390 else
391 return;
392
393 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
394 {
395 png_uint_32 s0 = (png_uint_32)(*(rp ) << 8) | *(rp + 1);
396 png_uint_32 s1 = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
397 png_uint_32 s2 = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
398 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
399 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
400 *(rp ) = (png_byte)((red >> 8) & 0xff);
401 *(rp + 1) = (png_byte)(red & 0xff);
402 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
403 *(rp + 5) = (png_byte)(blue & 0xff);
404 }
405 }
406 }
407 }
408 #endif /* MNG_FEATURES */
409
410 void PNGAPI
411 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
412 {
413 png_row_info row_info;
414
415 if (png_ptr == NULL)
416 return;
417
418 png_debug2(1, "in png_read_row (row %lu, pass %d)",
419 (unsigned long)png_ptr->row_number, png_ptr->pass);
420
421 /* png_read_start_row sets the information (in particular iwidth) for this
422 * interlace pass.
423 */
424 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
425 png_read_start_row(png_ptr);
426
427 /* 1.5.6: row_info moved out of png_struct to a local here. */
428 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
429 row_info.color_type = png_ptr->color_type;
430 row_info.bit_depth = png_ptr->bit_depth;
431 row_info.channels = png_ptr->channels;
432 row_info.pixel_depth = png_ptr->pixel_depth;
433 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
434
435 #ifdef PNG_WARNINGS_SUPPORTED
436 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
437 {
438 /* Check for transforms that have been set but were defined out */
439 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
440 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
441 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
442 #endif
443
444 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
445 if ((png_ptr->transformations & PNG_FILLER) != 0)
446 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
447 #endif
448
449 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
450 !defined(PNG_READ_PACKSWAP_SUPPORTED)
451 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
452 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
453 #endif
454
455 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
456 if ((png_ptr->transformations & PNG_PACK) != 0)
457 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
458 #endif
459
460 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
461 if ((png_ptr->transformations & PNG_SHIFT) != 0)
462 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
463 #endif
464
465 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
466 if ((png_ptr->transformations & PNG_BGR) != 0)
467 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
468 #endif
469
470 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
471 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
472 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
473 #endif
474 }
475 #endif /* WARNINGS */
476
477 #ifdef PNG_READ_INTERLACING_SUPPORTED
478 /* If interlaced and we do not need a new row, combine row and return.
479 * Notice that the pixels we have from previous rows have been transformed
480 * already; we can only combine like with like (transformed or
481 * untransformed) and, because of the libpng API for interlaced images, this
482 * means we must transform before de-interlacing.
483 */
484 if (png_ptr->interlaced != 0 &&
485 (png_ptr->transformations & PNG_INTERLACE) != 0)
486 {
487 switch (png_ptr->pass)
488 {
489 case 0:
490 if (png_ptr->row_number & 0x07)
491 {
492 if (dsp_row != NULL)
493 png_combine_row(png_ptr, dsp_row, 1/*display*/);
494 png_read_finish_row(png_ptr);
495 return;
496 }
497 break;
498
499 case 1:
500 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
501 {
502 if (dsp_row != NULL)
503 png_combine_row(png_ptr, dsp_row, 1/*display*/);
504
505 png_read_finish_row(png_ptr);
506 return;
507 }
508 break;
509
510 case 2:
511 if ((png_ptr->row_number & 0x07) != 4)
512 {
513 if (dsp_row != NULL && (png_ptr->row_number & 4))
514 png_combine_row(png_ptr, dsp_row, 1/*display*/);
515
516 png_read_finish_row(png_ptr);
517 return;
518 }
519 break;
520
521 case 3:
522 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
523 {
524 if (dsp_row != NULL)
525 png_combine_row(png_ptr, dsp_row, 1/*display*/);
526
527 png_read_finish_row(png_ptr);
528 return;
529 }
530 break;
531
532 case 4:
533 if ((png_ptr->row_number & 3) != 2)
534 {
535 if (dsp_row != NULL && (png_ptr->row_number & 2))
536 png_combine_row(png_ptr, dsp_row, 1/*display*/);
537
538 png_read_finish_row(png_ptr);
539 return;
540 }
541 break;
542
543 case 5:
544 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
545 {
546 if (dsp_row != NULL)
547 png_combine_row(png_ptr, dsp_row, 1/*display*/);
548
549 png_read_finish_row(png_ptr);
550 return;
551 }
552 break;
553
554 default:
555 case 6:
556 if ((png_ptr->row_number & 1) == 0)
557 {
558 png_read_finish_row(png_ptr);
559 return;
560 }
561 break;
562 }
563 }
564 #endif
565
566 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
567 png_error(png_ptr, "Invalid attempt to read row data");
568
569 /* Fill the row with IDAT data: */
570 png_ptr->row_buf[0]=255; /* to force error if no data was found */
571 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
572
573 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
574 {
575 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
576 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
577 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
578 else
579 png_error(png_ptr, "bad adaptive filter value");
580 }
581
582 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
583 * 1.5.6, while the buffer really is this big in current versions of libpng
584 * it may not be in the future, so this was changed just to copy the
585 * interlaced count:
586 */
587 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
588
589 #ifdef PNG_MNG_FEATURES_SUPPORTED
590 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
591 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
592 {
593 /* Intrapixel differencing */
594 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
595 }
596 #endif
597
598 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
599 if (png_ptr->transformations)
600 png_do_read_transformations(png_ptr, &row_info);
601 #endif
602
603 /* The transformed pixel depth should match the depth now in row_info. */
604 if (png_ptr->transformed_pixel_depth == 0)
605 {
606 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
607 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
608 png_error(png_ptr, "sequential row overflow");
609 }
610
611 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
612 png_error(png_ptr, "internal sequential row size calculation error");
613
614 #ifdef PNG_READ_INTERLACING_SUPPORTED
615 /* Expand interlaced rows to full size */
616 if (png_ptr->interlaced != 0 &&
617 (png_ptr->transformations & PNG_INTERLACE) != 0)
618 {
619 if (png_ptr->pass < 6)
620 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
621 png_ptr->transformations);
622
623 if (dsp_row != NULL)
624 png_combine_row(png_ptr, dsp_row, 1/*display*/);
625
626 if (row != NULL)
627 png_combine_row(png_ptr, row, 0/*row*/);
628 }
629
630 else
631 #endif
632 {
633 if (row != NULL)
634 png_combine_row(png_ptr, row, -1/*ignored*/);
635
636 if (dsp_row != NULL)
637 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
638 }
639 png_read_finish_row(png_ptr);
640
641 if (png_ptr->read_row_fn != NULL)
642 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
643
644 }
645 #endif /* SEQUENTIAL_READ */
646
647 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
648 /* Read one or more rows of image data. If the image is interlaced,
649 * and png_set_interlace_handling() has been called, the rows need to
650 * contain the contents of the rows from the previous pass. If the
651 * image has alpha or transparency, and png_handle_alpha()[*] has been
652 * called, the rows contents must be initialized to the contents of the
653 * screen.
654 *
655 * "row" holds the actual image, and pixels are placed in it
656 * as they arrive. If the image is displayed after each pass, it will
657 * appear to "sparkle" in. "display_row" can be used to display a
658 * "chunky" progressive image, with finer detail added as it becomes
659 * available. If you do not want this "chunky" display, you may pass
660 * NULL for display_row. If you do not want the sparkle display, and
661 * you have not called png_handle_alpha(), you may pass NULL for rows.
662 * If you have called png_handle_alpha(), and the image has either an
663 * alpha channel or a transparency chunk, you must provide a buffer for
664 * rows. In this case, you do not have to provide a display_row buffer
665 * also, but you may. If the image is not interlaced, or if you have
666 * not called png_set_interlace_handling(), the display_row buffer will
667 * be ignored, so pass NULL to it.
668 *
669 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
670 */
671
672 void PNGAPI
673 png_read_rows(png_structrp png_ptr, png_bytepp row,
674 png_bytepp display_row, png_uint_32 num_rows)
675 {
676 png_uint_32 i;
677 png_bytepp rp;
678 png_bytepp dp;
679
680 png_debug(1, "in png_read_rows");
681
682 if (png_ptr == NULL)
683 return;
684
685 rp = row;
686 dp = display_row;
687 if (rp != NULL && dp != NULL)
688 for (i = 0; i < num_rows; i++)
689 {
690 png_bytep rptr = *rp++;
691 png_bytep dptr = *dp++;
692
693 png_read_row(png_ptr, rptr, dptr);
694 }
695
696 else if (rp != NULL)
697 for (i = 0; i < num_rows; i++)
698 {
699 png_bytep rptr = *rp;
700 png_read_row(png_ptr, rptr, NULL);
701 rp++;
702 }
703
704 else if (dp != NULL)
705 for (i = 0; i < num_rows; i++)
706 {
707 png_bytep dptr = *dp;
708 png_read_row(png_ptr, NULL, dptr);
709 dp++;
710 }
711 }
712 #endif /* SEQUENTIAL_READ */
713
714 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
715 /* Read the entire image. If the image has an alpha channel or a tRNS
716 * chunk, and you have called png_handle_alpha()[*], you will need to
717 * initialize the image to the current image that PNG will be overlaying.
718 * We set the num_rows again here, in case it was incorrectly set in
719 * png_read_start_row() by a call to png_read_update_info() or
720 * png_start_read_image() if png_set_interlace_handling() wasn't called
721 * prior to either of these functions like it should have been. You can
722 * only call this function once. If you desire to have an image for
723 * each pass of a interlaced image, use png_read_rows() instead.
724 *
725 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
726 */
727 void PNGAPI
728 png_read_image(png_structrp png_ptr, png_bytepp image)
729 {
730 png_uint_32 i, image_height;
731 int pass, j;
732 png_bytepp rp;
733
734 png_debug(1, "in png_read_image");
735
736 if (png_ptr == NULL)
737 return;
738
739 #ifdef PNG_READ_INTERLACING_SUPPORTED
740 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
741 {
742 pass = png_set_interlace_handling(png_ptr);
743 /* And make sure transforms are initialized. */
744 png_start_read_image(png_ptr);
745 }
746 else
747 {
748 if (png_ptr->interlaced != 0 &&
749 (png_ptr->transformations & PNG_INTERLACE) == 0)
750 {
751 /* Caller called png_start_read_image or png_read_update_info without
752 * first turning on the PNG_INTERLACE transform. We can fix this here,
753 * but the caller should do it!
754 */
755 png_warning(png_ptr, "Interlace handling should be turned on when "
756 "using png_read_image");
757 /* Make sure this is set correctly */
758 png_ptr->num_rows = png_ptr->height;
759 }
760
761 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
762 * the above error case.
763 */
764 pass = png_set_interlace_handling(png_ptr);
765 }
766 #else
767 if (png_ptr->interlaced)
768 png_error(png_ptr,
769 "Cannot read interlaced image -- interlace handler disabled");
770
771 pass = 1;
772 #endif
773
774 image_height=png_ptr->height;
775
776 for (j = 0; j < pass; j++)
777 {
778 rp = image;
779 for (i = 0; i < image_height; i++)
780 {
781 png_read_row(png_ptr, *rp, NULL);
782 rp++;
783 }
784 }
785 }
786 #endif /* SEQUENTIAL_READ */
787
788 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
789 /* Read the end of the PNG file. Will not read past the end of the
790 * file, will verify the end is accurate, and will read any comments
791 * or time information at the end of the file, if info is not NULL.
792 */
793 void PNGAPI
794 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
795 {
796 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
797 int keep;
798 #endif
799
800 png_debug(1, "in png_read_end");
801
802 if (png_ptr == NULL)
803 return;
804
805 /* If png_read_end is called in the middle of reading the rows there may
806 * still be pending IDAT data and an owned zstream. Deal with this here.
807 */
808 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
809 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
810 #endif
811 png_read_finish_IDAT(png_ptr);
812
813 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
814 /* Report invalid palette index; added at libng-1.5.10 */
815 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
816 png_ptr->num_palette_max > png_ptr->num_palette)
817 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
818 #endif
819
820 do
821 {
822 png_uint_32 length = png_read_chunk_header(png_ptr);
823 png_uint_32 chunk_name = png_ptr->chunk_name;
824
825 if (chunk_name != png_IDAT)
826 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
827
828 if (chunk_name == png_IEND)
829 png_handle_IEND(png_ptr, info_ptr, length);
830
831 else if (chunk_name == png_IHDR)
832 png_handle_IHDR(png_ptr, info_ptr, length);
833
834 else if (info_ptr == NULL)
835 png_crc_finish(png_ptr, length);
836
837 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
838 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
839 {
840 if (chunk_name == png_IDAT)
841 {
842 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
843 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
844 png_benign_error(png_ptr, ".Too many IDATs found");
845 }
846 png_handle_unknown(png_ptr, info_ptr, length, keep);
847 if (chunk_name == png_PLTE)
848 png_ptr->mode |= PNG_HAVE_PLTE;
849 }
850 #endif
851
852 else if (chunk_name == png_IDAT)
853 {
854 /* Zero length IDATs are legal after the last IDAT has been
855 * read, but not after other chunks have been read. 1.6 does not
856 * always read all the deflate data; specifically it cannot be relied
857 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
858 * chunks which are longer than zero as well:
859 */
860 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
861 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
862 png_benign_error(png_ptr, "..Too many IDATs found");
863
864 png_crc_finish(png_ptr, length);
865 }
866 else if (chunk_name == png_PLTE)
867 png_handle_PLTE(png_ptr, info_ptr, length);
868
869 #ifdef PNG_READ_bKGD_SUPPORTED
870 else if (chunk_name == png_bKGD)
871 png_handle_bKGD(png_ptr, info_ptr, length);
872 #endif
873
874 #ifdef PNG_READ_cHRM_SUPPORTED
875 else if (chunk_name == png_cHRM)
876 png_handle_cHRM(png_ptr, info_ptr, length);
877 #endif
878
879 #ifdef PNG_READ_eXIf_SUPPORTED
880 else if (chunk_name == png_eXIf)
881 png_handle_eXIf(png_ptr, info_ptr, length);
882 #endif
883
884 #ifdef PNG_READ_gAMA_SUPPORTED
885 else if (chunk_name == png_gAMA)
886 png_handle_gAMA(png_ptr, info_ptr, length);
887 #endif
888
889 #ifdef PNG_READ_hIST_SUPPORTED
890 else if (chunk_name == png_hIST)
891 png_handle_hIST(png_ptr, info_ptr, length);
892 #endif
893
894 #ifdef PNG_READ_oFFs_SUPPORTED
895 else if (chunk_name == png_oFFs)
896 png_handle_oFFs(png_ptr, info_ptr, length);
897 #endif
898
899 #ifdef PNG_READ_pCAL_SUPPORTED
900 else if (chunk_name == png_pCAL)
901 png_handle_pCAL(png_ptr, info_ptr, length);
902 #endif
903
904 #ifdef PNG_READ_sCAL_SUPPORTED
905 else if (chunk_name == png_sCAL)
906 png_handle_sCAL(png_ptr, info_ptr, length);
907 #endif
908
909 #ifdef PNG_READ_pHYs_SUPPORTED
910 else if (chunk_name == png_pHYs)
911 png_handle_pHYs(png_ptr, info_ptr, length);
912 #endif
913
914 #ifdef PNG_READ_sBIT_SUPPORTED
915 else if (chunk_name == png_sBIT)
916 png_handle_sBIT(png_ptr, info_ptr, length);
917 #endif
918
919 #ifdef PNG_READ_sRGB_SUPPORTED
920 else if (chunk_name == png_sRGB)
921 png_handle_sRGB(png_ptr, info_ptr, length);
922 #endif
923
924 #ifdef PNG_READ_iCCP_SUPPORTED
925 else if (chunk_name == png_iCCP)
926 png_handle_iCCP(png_ptr, info_ptr, length);
927 #endif
928
929 #ifdef PNG_READ_sPLT_SUPPORTED
930 else if (chunk_name == png_sPLT)
931 png_handle_sPLT(png_ptr, info_ptr, length);
932 #endif
933
934 #ifdef PNG_READ_tEXt_SUPPORTED
935 else if (chunk_name == png_tEXt)
936 png_handle_tEXt(png_ptr, info_ptr, length);
937 #endif
938
939 #ifdef PNG_READ_tIME_SUPPORTED
940 else if (chunk_name == png_tIME)
941 png_handle_tIME(png_ptr, info_ptr, length);
942 #endif
943
944 #ifdef PNG_READ_tRNS_SUPPORTED
945 else if (chunk_name == png_tRNS)
946 png_handle_tRNS(png_ptr, info_ptr, length);
947 #endif
948
949 #ifdef PNG_READ_zTXt_SUPPORTED
950 else if (chunk_name == png_zTXt)
951 png_handle_zTXt(png_ptr, info_ptr, length);
952 #endif
953
954 #ifdef PNG_READ_iTXt_SUPPORTED
955 else if (chunk_name == png_iTXt)
956 png_handle_iTXt(png_ptr, info_ptr, length);
957 #endif
958
959 else
960 png_handle_unknown(png_ptr, info_ptr, length,
961 PNG_HANDLE_CHUNK_AS_DEFAULT);
962 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
963 }
964 #endif /* SEQUENTIAL_READ */
965
966 /* Free all memory used in the read struct */
967 static void
968 png_read_destroy(png_structrp png_ptr)
969 {
970 png_debug(1, "in png_read_destroy");
971
972 #ifdef PNG_READ_GAMMA_SUPPORTED
973 png_destroy_gamma_table(png_ptr);
974 #endif
975
976 png_free(png_ptr, png_ptr->big_row_buf);
977 png_ptr->big_row_buf = NULL;
978 png_free(png_ptr, png_ptr->big_prev_row);
979 png_ptr->big_prev_row = NULL;
980 png_free(png_ptr, png_ptr->read_buffer);
981 png_ptr->read_buffer = NULL;
982
983 #ifdef PNG_READ_QUANTIZE_SUPPORTED
984 png_free(png_ptr, png_ptr->palette_lookup);
985 png_ptr->palette_lookup = NULL;
986 png_free(png_ptr, png_ptr->quantize_index);
987 png_ptr->quantize_index = NULL;
988 #endif
989
990 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
991 {
992 png_zfree(png_ptr, png_ptr->palette);
993 png_ptr->palette = NULL;
994 }
995 png_ptr->free_me &= ~PNG_FREE_PLTE;
996
997 #if defined(PNG_tRNS_SUPPORTED) || \
998 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
999 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
1000 {
1001 png_free(png_ptr, png_ptr->trans_alpha);
1002 png_ptr->trans_alpha = NULL;
1003 }
1004 png_ptr->free_me &= ~PNG_FREE_TRNS;
1005 #endif
1006
1007 inflateEnd(&png_ptr->zstream);
1008
1009 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
1010 png_free(png_ptr, png_ptr->save_buffer);
1011 png_ptr->save_buffer = NULL;
1012 #endif
1013
1014 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
1015 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
1016 png_free(png_ptr, png_ptr->unknown_chunk.data);
1017 png_ptr->unknown_chunk.data = NULL;
1018 #endif
1019
1020 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
1021 png_free(png_ptr, png_ptr->chunk_list);
1022 png_ptr->chunk_list = NULL;
1023 #endif
1024
1025 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1026 * callbacks are still set at this point. They are required to complete the
1027 * destruction of the png_struct itself.
1028 */
1029 }
1030
1031 /* Free all memory used by the read */
1032 void PNGAPI
1033 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1034 png_infopp end_info_ptr_ptr)
1035 {
1036 png_structrp png_ptr = NULL;
1037
1038 png_debug(1, "in png_destroy_read_struct");
1039
1040 if (png_ptr_ptr != NULL)
1041 png_ptr = *png_ptr_ptr;
1042
1043 if (png_ptr == NULL)
1044 return;
1045
1046 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1047 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1048 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1049 */
1050 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1051 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1052
1053 *png_ptr_ptr = NULL;
1054 png_read_destroy(png_ptr);
1055 png_destroy_png_struct(png_ptr);
1056 }
1057
1058 void PNGAPI
1059 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1060 {
1061 if (png_ptr == NULL)
1062 return;
1063
1064 png_ptr->read_row_fn = read_row_fn;
1065 }
1066
1067
1068 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1069 #ifdef PNG_INFO_IMAGE_SUPPORTED
1070 void PNGAPI
1071 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1072 int transforms, voidp params)
1073 {
1074 if (png_ptr == NULL || info_ptr == NULL)
1075 return;
1076
1077 /* png_read_info() gives us all of the information from the
1078 * PNG file before the first IDAT (image data chunk).
1079 */
1080 png_read_info(png_ptr, info_ptr);
1081 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1082 png_error(png_ptr, "Image is too high to process with png_read_png()");
1083
1084 /* -------------- image transformations start here ------------------- */
1085 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1086 * is not implemented. This will only happen in de-configured (non-default)
1087 * libpng builds. The results can be unexpected - png_read_png may return
1088 * short or mal-formed rows because the transform is skipped.
1089 */
1090
1091 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1092 */
1093 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1094 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1095 * did in earlier versions, while "scale_16" is now more accurate.
1096 */
1097 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1098 png_set_scale_16(png_ptr);
1099 #else
1100 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1101 #endif
1102
1103 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1104 * latter by doing SCALE first. This is ok and allows apps not to check for
1105 * which is supported to get the right answer.
1106 */
1107 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1108 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1109 png_set_strip_16(png_ptr);
1110 #else
1111 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1112 #endif
1113
1114 /* Strip alpha bytes from the input data without combining with
1115 * the background (not recommended).
1116 */
1117 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1118 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1119 png_set_strip_alpha(png_ptr);
1120 #else
1121 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1122 #endif
1123
1124 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1125 * byte into separate bytes (useful for paletted and grayscale images).
1126 */
1127 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1128 #ifdef PNG_READ_PACK_SUPPORTED
1129 png_set_packing(png_ptr);
1130 #else
1131 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1132 #endif
1133
1134 /* Change the order of packed pixels to least significant bit first
1135 * (not useful if you are using png_set_packing).
1136 */
1137 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1138 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1139 png_set_packswap(png_ptr);
1140 #else
1141 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1142 #endif
1143
1144 /* Expand paletted colors into true RGB triplets
1145 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1146 * Expand paletted or RGB images with transparency to full alpha
1147 * channels so the data will be available as RGBA quartets.
1148 */
1149 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1150 #ifdef PNG_READ_EXPAND_SUPPORTED
1151 png_set_expand(png_ptr);
1152 #else
1153 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1154 #endif
1155
1156 /* We don't handle background color or gamma transformation or quantizing.
1157 */
1158
1159 /* Invert monochrome files to have 0 as white and 1 as black
1160 */
1161 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1162 #ifdef PNG_READ_INVERT_SUPPORTED
1163 png_set_invert_mono(png_ptr);
1164 #else
1165 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1166 #endif
1167
1168 /* If you want to shift the pixel values from the range [0,255] or
1169 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1170 * colors were originally in:
1171 */
1172 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1173 #ifdef PNG_READ_SHIFT_SUPPORTED
1174 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1175 png_set_shift(png_ptr, &info_ptr->sig_bit);
1176 #else
1177 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1178 #endif
1179
1180 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1181 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1182 #ifdef PNG_READ_BGR_SUPPORTED
1183 png_set_bgr(png_ptr);
1184 #else
1185 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1186 #endif
1187
1188 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1189 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1190 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1191 png_set_swap_alpha(png_ptr);
1192 #else
1193 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1194 #endif
1195
1196 /* Swap bytes of 16-bit files to least significant byte first */
1197 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1198 #ifdef PNG_READ_SWAP_SUPPORTED
1199 png_set_swap(png_ptr);
1200 #else
1201 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1202 #endif
1203
1204 /* Added at libpng-1.2.41 */
1205 /* Invert the alpha channel from opacity to transparency */
1206 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1207 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1208 png_set_invert_alpha(png_ptr);
1209 #else
1210 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1211 #endif
1212
1213 /* Added at libpng-1.2.41 */
1214 /* Expand grayscale image to RGB */
1215 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1216 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1217 png_set_gray_to_rgb(png_ptr);
1218 #else
1219 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1220 #endif
1221
1222 /* Added at libpng-1.5.4 */
1223 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1224 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1225 png_set_expand_16(png_ptr);
1226 #else
1227 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1228 #endif
1229
1230 /* We don't handle adding filler bytes */
1231
1232 /* We use png_read_image and rely on that for interlace handling, but we also
1233 * call png_read_update_info therefore must turn on interlace handling now:
1234 */
1235 (void)png_set_interlace_handling(png_ptr);
1236
1237 /* Optional call to gamma correct and add the background to the palette
1238 * and update info structure. REQUIRED if you are expecting libpng to
1239 * update the palette for you (i.e., you selected such a transform above).
1240 */
1241 png_read_update_info(png_ptr, info_ptr);
1242
1243 /* -------------- image transformations end here ------------------- */
1244
1245 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1246 if (info_ptr->row_pointers == NULL)
1247 {
1248 png_uint_32 iptr;
1249
1250 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1251 info_ptr->height * (sizeof (png_bytep))));
1252
1253 for (iptr=0; iptr<info_ptr->height; iptr++)
1254 info_ptr->row_pointers[iptr] = NULL;
1255
1256 info_ptr->free_me |= PNG_FREE_ROWS;
1257
1258 for (iptr = 0; iptr < info_ptr->height; iptr++)
1259 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1260 png_malloc(png_ptr, info_ptr->rowbytes));
1261 }
1262
1263 png_read_image(png_ptr, info_ptr->row_pointers);
1264 info_ptr->valid |= PNG_INFO_IDAT;
1265
1266 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1267 png_read_end(png_ptr, info_ptr);
1268
1269 PNG_UNUSED(params)
1270 }
1271 #endif /* INFO_IMAGE */
1272 #endif /* SEQUENTIAL_READ */
1273
1274 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1275 /* SIMPLIFIED READ
1276 *
1277 * This code currently relies on the sequential reader, though it could easily
1278 * be made to work with the progressive one.
1279 */
1280 /* Arguments to png_image_finish_read: */
1281
1282 /* Encoding of PNG data (used by the color-map code) */
1283 # define P_NOTSET 0 /* File encoding not yet known */
1284 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1285 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1286 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1287 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1288
1289 /* Color-map processing: after libpng has run on the PNG image further
1290 * processing may be needed to convert the data to color-map indices.
1291 */
1292 #define PNG_CMAP_NONE 0
1293 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1294 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1295 #define PNG_CMAP_RGB 3 /* Process RGB data */
1296 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1297
1298 /* The following document where the background is for each processing case. */
1299 #define PNG_CMAP_NONE_BACKGROUND 256
1300 #define PNG_CMAP_GA_BACKGROUND 231
1301 #define PNG_CMAP_TRANS_BACKGROUND 254
1302 #define PNG_CMAP_RGB_BACKGROUND 256
1303 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1304
1305 typedef struct
1306 {
1307 /* Arguments: */
1308 png_imagep image;
1309 png_voidp buffer;
1310 png_int_32 row_stride;
1311 png_voidp colormap;
1312 png_const_colorp background;
1313 /* Local variables: */
1314 png_voidp local_row;
1315 png_voidp first_row;
1316 ptrdiff_t row_bytes; /* step between rows */
1317 int file_encoding; /* E_ values above */
1318 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1319 int colormap_processing; /* PNG_CMAP_ values above */
1320 } png_image_read_control;
1321
1322 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1323 * called, so setting up the jmp_buf is not required. This means that anything
1324 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1325 * instead so that control is returned safely back to this routine.
1326 */
1327 static int
1328 png_image_read_init(png_imagep image)
1329 {
1330 if (image->opaque == NULL)
1331 {
1332 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1333 png_safe_error, png_safe_warning);
1334
1335 /* And set the rest of the structure to NULL to ensure that the various
1336 * fields are consistent.
1337 */
1338 memset(image, 0, (sizeof *image));
1339 image->version = PNG_IMAGE_VERSION;
1340
1341 if (png_ptr != NULL)
1342 {
1343 png_infop info_ptr = png_create_info_struct(png_ptr);
1344
1345 if (info_ptr != NULL)
1346 {
1347 png_controlp control = png_voidcast(png_controlp,
1348 png_malloc_warn(png_ptr, (sizeof *control)));
1349
1350 if (control != NULL)
1351 {
1352 memset(control, 0, (sizeof *control));
1353
1354 control->png_ptr = png_ptr;
1355 control->info_ptr = info_ptr;
1356 control->for_write = 0;
1357
1358 image->opaque = control;
1359 return 1;
1360 }
1361
1362 /* Error clean up */
1363 png_destroy_info_struct(png_ptr, &info_ptr);
1364 }
1365
1366 png_destroy_read_struct(&png_ptr, NULL, NULL);
1367 }
1368
1369 return png_image_error(image, "png_image_read: out of memory");
1370 }
1371
1372 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1373 }
1374
1375 /* Utility to find the base format of a PNG file from a png_struct. */
1376 static png_uint_32
1377 png_image_format(png_structrp png_ptr)
1378 {
1379 png_uint_32 format = 0;
1380
1381 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1382 format |= PNG_FORMAT_FLAG_COLOR;
1383
1384 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1385 format |= PNG_FORMAT_FLAG_ALPHA;
1386
1387 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1388 * sets the png_struct fields; that's all we are interested in here. The
1389 * precise interaction with an app call to png_set_tRNS and PNG file reading
1390 * is unclear.
1391 */
1392 else if (png_ptr->num_trans > 0)
1393 format |= PNG_FORMAT_FLAG_ALPHA;
1394
1395 if (png_ptr->bit_depth == 16)
1396 format |= PNG_FORMAT_FLAG_LINEAR;
1397
1398 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1399 format |= PNG_FORMAT_FLAG_COLORMAP;
1400
1401 return format;
1402 }
1403
1404 /* Is the given gamma significantly different from sRGB? The test is the same
1405 * one used in pngrtran.c when deciding whether to do gamma correction. The
1406 * arithmetic optimizes the division by using the fact that the inverse of the
1407 * file sRGB gamma is 2.2
1408 */
1409 static int
1410 png_gamma_not_sRGB(png_fixed_point g)
1411 {
1412 if (g < PNG_FP_1)
1413 {
1414 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1415 if (g == 0)
1416 return 0;
1417
1418 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1419 }
1420
1421 return 1;
1422 }
1423
1424 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1425 * header and fill in all the information. This is executed in a safe context,
1426 * unlike the init routine above.
1427 */
1428 static int
1429 png_image_read_header(png_voidp argument)
1430 {
1431 png_imagep image = png_voidcast(png_imagep, argument);
1432 png_structrp png_ptr = image->opaque->png_ptr;
1433 png_inforp info_ptr = image->opaque->info_ptr;
1434
1435 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
1436 png_set_benign_errors(png_ptr, 1/*warn*/);
1437 #endif
1438 png_read_info(png_ptr, info_ptr);
1439
1440 /* Do this the fast way; just read directly out of png_struct. */
1441 image->width = png_ptr->width;
1442 image->height = png_ptr->height;
1443
1444 {
1445 png_uint_32 format = png_image_format(png_ptr);
1446
1447 image->format = format;
1448
1449 #ifdef PNG_COLORSPACE_SUPPORTED
1450 /* Does the colorspace match sRGB? If there is no color endpoint
1451 * (colorant) information assume yes, otherwise require the
1452 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1453 * colorspace has been determined to be invalid ignore it.
1454 */
1455 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1456 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1457 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1458 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1459 #endif
1460 }
1461
1462 /* We need the maximum number of entries regardless of the format the
1463 * application sets here.
1464 */
1465 {
1466 png_uint_32 cmap_entries;
1467
1468 switch (png_ptr->color_type)
1469 {
1470 case PNG_COLOR_TYPE_GRAY:
1471 cmap_entries = 1U << png_ptr->bit_depth;
1472 break;
1473
1474 case PNG_COLOR_TYPE_PALETTE:
1475 cmap_entries = (png_uint_32)png_ptr->num_palette;
1476 break;
1477
1478 default:
1479 cmap_entries = 256;
1480 break;
1481 }
1482
1483 if (cmap_entries > 256)
1484 cmap_entries = 256;
1485
1486 image->colormap_entries = cmap_entries;
1487 }
1488
1489 return 1;
1490 }
1491
1492 #ifdef PNG_STDIO_SUPPORTED
1493 int PNGAPI
1494 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1495 {
1496 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1497 {
1498 if (file != NULL)
1499 {
1500 if (png_image_read_init(image) != 0)
1501 {
1502 /* This is slightly evil, but png_init_io doesn't do anything other
1503 * than this and we haven't changed the standard IO functions so
1504 * this saves a 'safe' function.
1505 */
1506 image->opaque->png_ptr->io_ptr = file;
1507 return png_safe_execute(image, png_image_read_header, image);
1508 }
1509 }
1510
1511 else
1512 return png_image_error(image,
1513 "png_image_begin_read_from_stdio: invalid argument");
1514 }
1515
1516 else if (image != NULL)
1517 return png_image_error(image,
1518 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1519
1520 return 0;
1521 }
1522
1523 int PNGAPI
1524 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1525 {
1526 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1527 {
1528 if (file_name != NULL)
1529 {
1530 FILE *fp = fopen(file_name, "rb");
1531
1532 if (fp != NULL)
1533 {
1534 if (png_image_read_init(image) != 0)
1535 {
1536 image->opaque->png_ptr->io_ptr = fp;
1537 image->opaque->owned_file = 1;
1538 return png_safe_execute(image, png_image_read_header, image);
1539 }
1540
1541 /* Clean up: just the opened file. */
1542 (void)fclose(fp);
1543 }
1544
1545 else
1546 return png_image_error(image, strerror(errno));
1547 }
1548
1549 else
1550 return png_image_error(image,
1551 "png_image_begin_read_from_file: invalid argument");
1552 }
1553
1554 else if (image != NULL)
1555 return png_image_error(image,
1556 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1557
1558 return 0;
1559 }
1560 #endif /* STDIO */
1561
1562 static void PNGCBAPI
1563 png_image_memory_read(png_structp png_ptr, png_bytep out, size_t need)
1564 {
1565 if (png_ptr != NULL)
1566 {
1567 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1568 if (image != NULL)
1569 {
1570 png_controlp cp = image->opaque;
1571 if (cp != NULL)
1572 {
1573 png_const_bytep memory = cp->memory;
1574 size_t size = cp->size;
1575
1576 if (memory != NULL && size >= need)
1577 {
1578 memcpy(out, memory, need);
1579 cp->memory = memory + need;
1580 cp->size = size - need;
1581 return;
1582 }
1583
1584 png_error(png_ptr, "read beyond end of data");
1585 }
1586 }
1587
1588 png_error(png_ptr, "invalid memory read");
1589 }
1590 }
1591
1592 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1593 png_const_voidp memory, size_t size)
1594 {
1595 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1596 {
1597 if (memory != NULL && size > 0)
1598 {
1599 if (png_image_read_init(image) != 0)
1600 {
1601 /* Now set the IO functions to read from the memory buffer and
1602 * store it into io_ptr. Again do this in-place to avoid calling a
1603 * libpng function that requires error handling.
1604 */
1605 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1606 image->opaque->size = size;
1607 image->opaque->png_ptr->io_ptr = image;
1608 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1609
1610 return png_safe_execute(image, png_image_read_header, image);
1611 }
1612 }
1613
1614 else
1615 return png_image_error(image,
1616 "png_image_begin_read_from_memory: invalid argument");
1617 }
1618
1619 else if (image != NULL)
1620 return png_image_error(image,
1621 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1622
1623 return 0;
1624 }
1625
1626 /* Utility function to skip chunks that are not used by the simplified image
1627 * read functions and an appropriate macro to call it.
1628 */
1629 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1630 static void
1631 png_image_skip_unused_chunks(png_structrp png_ptr)
1632 {
1633 /* Prepare the reader to ignore all recognized chunks whose data will not
1634 * be used, i.e., all chunks recognized by libpng except for those
1635 * involved in basic image reading:
1636 *
1637 * IHDR, PLTE, IDAT, IEND
1638 *
1639 * Or image data handling:
1640 *
1641 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1642 *
1643 * This provides a small performance improvement and eliminates any
1644 * potential vulnerability to security problems in the unused chunks.
1645 *
1646 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1647 * too. This allows the simplified API to be compiled without iCCP support,
1648 * however if the support is there the chunk is still checked to detect
1649 * errors (which are unfortunately quite common.)
1650 */
1651 {
1652 static PNG_CONST png_byte chunks_to_process[] = {
1653 98, 75, 71, 68, '\0', /* bKGD */
1654 99, 72, 82, 77, '\0', /* cHRM */
1655 103, 65, 77, 65, '\0', /* gAMA */
1656 # ifdef PNG_READ_iCCP_SUPPORTED
1657 105, 67, 67, 80, '\0', /* iCCP */
1658 # endif
1659 115, 66, 73, 84, '\0', /* sBIT */
1660 115, 82, 71, 66, '\0', /* sRGB */
1661 };
1662
1663 /* Ignore unknown chunks and all other chunks except for the
1664 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1665 */
1666 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1667 NULL, -1);
1668
1669 /* But do not ignore image data handling chunks */
1670 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1671 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1672 }
1673 }
1674
1675 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1676 #else
1677 # define PNG_SKIP_CHUNKS(p) ((void)0)
1678 #endif /* HANDLE_AS_UNKNOWN */
1679
1680 /* The following macro gives the exact rounded answer for all values in the
1681 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1682 * the correct numbers 0..5
1683 */
1684 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1685
1686 /* Utility functions to make particular color-maps */
1687 static void
1688 set_file_encoding(png_image_read_control *display)
1689 {
1690 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1691 if (png_gamma_significant(g) != 0)
1692 {
1693 if (png_gamma_not_sRGB(g) != 0)
1694 {
1695 display->file_encoding = P_FILE;
1696 display->gamma_to_linear = png_reciprocal(g);
1697 }
1698
1699 else
1700 display->file_encoding = P_sRGB;
1701 }
1702
1703 else
1704 display->file_encoding = P_LINEAR8;
1705 }
1706
1707 static unsigned int
1708 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1709 {
1710 if (encoding == P_FILE) /* double check */
1711 encoding = display->file_encoding;
1712
1713 if (encoding == P_NOTSET) /* must be the file encoding */
1714 {
1715 set_file_encoding(display);
1716 encoding = display->file_encoding;
1717 }
1718
1719 switch (encoding)
1720 {
1721 case P_FILE:
1722 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1723 break;
1724
1725 case P_sRGB:
1726 value = png_sRGB_table[value];
1727 break;
1728
1729 case P_LINEAR:
1730 break;
1731
1732 case P_LINEAR8:
1733 value *= 257;
1734 break;
1735
1736 #ifdef __GNUC__
1737 default:
1738 png_error(display->image->opaque->png_ptr,
1739 "unexpected encoding (internal error)");
1740 #endif
1741 }
1742
1743 return value;
1744 }
1745
1746 static png_uint_32
1747 png_colormap_compose(png_image_read_control *display,
1748 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1749 png_uint_32 background, int encoding)
1750 {
1751 /* The file value is composed on the background, the background has the given
1752 * encoding and so does the result, the file is encoded with P_FILE and the
1753 * file and alpha are 8-bit values. The (output) encoding will always be
1754 * P_LINEAR or P_sRGB.
1755 */
1756 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1757 png_uint_32 b = decode_gamma(display, background, encoding);
1758
1759 /* The alpha is always an 8-bit value (it comes from the palette), the value
1760 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1761 */
1762 f = f * alpha + b * (255-alpha);
1763
1764 if (encoding == P_LINEAR)
1765 {
1766 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1767 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1768 */
1769 f *= 257; /* Now scaled by 65535 */
1770 f += f >> 16;
1771 f = (f+32768) >> 16;
1772 }
1773
1774 else /* P_sRGB */
1775 f = PNG_sRGB_FROM_LINEAR(f);
1776
1777 return f;
1778 }
1779
1780 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1781 * be 8-bit.
1782 */
1783 static void
1784 png_create_colormap_entry(png_image_read_control *display,
1785 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1786 png_uint_32 alpha, int encoding)
1787 {
1788 png_imagep image = display->image;
1789 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1790 P_LINEAR : P_sRGB;
1791 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1792 (red != green || green != blue);
1793
1794 if (ip > 255)
1795 png_error(image->opaque->png_ptr, "color-map index out of range");
1796
1797 /* Update the cache with whether the file gamma is significantly different
1798 * from sRGB.
1799 */
1800 if (encoding == P_FILE)
1801 {
1802 if (display->file_encoding == P_NOTSET)
1803 set_file_encoding(display);
1804
1805 /* Note that the cached value may be P_FILE too, but if it is then the
1806 * gamma_to_linear member has been set.
1807 */
1808 encoding = display->file_encoding;
1809 }
1810
1811 if (encoding == P_FILE)
1812 {
1813 png_fixed_point g = display->gamma_to_linear;
1814
1815 red = png_gamma_16bit_correct(red*257, g);
1816 green = png_gamma_16bit_correct(green*257, g);
1817 blue = png_gamma_16bit_correct(blue*257, g);
1818
1819 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1820 {
1821 alpha *= 257;
1822 encoding = P_LINEAR;
1823 }
1824
1825 else
1826 {
1827 red = PNG_sRGB_FROM_LINEAR(red * 255);
1828 green = PNG_sRGB_FROM_LINEAR(green * 255);
1829 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1830 encoding = P_sRGB;
1831 }
1832 }
1833
1834 else if (encoding == P_LINEAR8)
1835 {
1836 /* This encoding occurs quite frequently in test cases because PngSuite
1837 * includes a gAMA 1.0 chunk with most images.
1838 */
1839 red *= 257;
1840 green *= 257;
1841 blue *= 257;
1842 alpha *= 257;
1843 encoding = P_LINEAR;
1844 }
1845
1846 else if (encoding == P_sRGB &&
1847 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1848 {
1849 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1850 * linear.
1851 */
1852 red = png_sRGB_table[red];
1853 green = png_sRGB_table[green];
1854 blue = png_sRGB_table[blue];
1855 alpha *= 257;
1856 encoding = P_LINEAR;
1857 }
1858
1859 /* This is set if the color isn't gray but the output is. */
1860 if (encoding == P_LINEAR)
1861 {
1862 if (convert_to_Y != 0)
1863 {
1864 /* NOTE: these values are copied from png_do_rgb_to_gray */
1865 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1866 (png_uint_32)2366 * blue;
1867
1868 if (output_encoding == P_LINEAR)
1869 y = (y + 16384) >> 15;
1870
1871 else
1872 {
1873 /* y is scaled by 32768, we need it scaled by 255: */
1874 y = (y + 128) >> 8;
1875 y *= 255;
1876 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1877 alpha = PNG_DIV257(alpha);
1878 encoding = P_sRGB;
1879 }
1880
1881 blue = red = green = y;
1882 }
1883
1884 else if (output_encoding == P_sRGB)
1885 {
1886 red = PNG_sRGB_FROM_LINEAR(red * 255);
1887 green = PNG_sRGB_FROM_LINEAR(green * 255);
1888 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1889 alpha = PNG_DIV257(alpha);
1890 encoding = P_sRGB;
1891 }
1892 }
1893
1894 if (encoding != output_encoding)
1895 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1896
1897 /* Store the value. */
1898 {
1899 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1900 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1901 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1902 # else
1903 # define afirst 0
1904 # endif
1905 # ifdef PNG_FORMAT_BGR_SUPPORTED
1906 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1907 # else
1908 # define bgr 0
1909 # endif
1910
1911 if (output_encoding == P_LINEAR)
1912 {
1913 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1914
1915 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1916
1917 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1918 * value, if less than 65535 (this is, effectively, composite on black
1919 * if the alpha channel is removed.)
1920 */
1921 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1922 {
1923 case 4:
1924 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1925 /* FALLTHROUGH */
1926
1927 case 3:
1928 if (alpha < 65535)
1929 {
1930 if (alpha > 0)
1931 {
1932 blue = (blue * alpha + 32767U)/65535U;
1933 green = (green * alpha + 32767U)/65535U;
1934 red = (red * alpha + 32767U)/65535U;
1935 }
1936
1937 else
1938 red = green = blue = 0;
1939 }
1940 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1941 entry[afirst + 1] = (png_uint_16)green;
1942 entry[afirst + bgr] = (png_uint_16)red;
1943 break;
1944
1945 case 2:
1946 entry[1 ^ afirst] = (png_uint_16)alpha;
1947 /* FALLTHROUGH */
1948
1949 case 1:
1950 if (alpha < 65535)
1951 {
1952 if (alpha > 0)
1953 green = (green * alpha + 32767U)/65535U;
1954
1955 else
1956 green = 0;
1957 }
1958 entry[afirst] = (png_uint_16)green;
1959 break;
1960
1961 default:
1962 break;
1963 }
1964 }
1965
1966 else /* output encoding is P_sRGB */
1967 {
1968 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1969
1970 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1971
1972 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1973 {
1974 case 4:
1975 entry[afirst ? 0 : 3] = (png_byte)alpha;
1976 /* FALLTHROUGH */
1977 case 3:
1978 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1979 entry[afirst + 1] = (png_byte)green;
1980 entry[afirst + bgr] = (png_byte)red;
1981 break;
1982
1983 case 2:
1984 entry[1 ^ afirst] = (png_byte)alpha;
1985 /* FALLTHROUGH */
1986 case 1:
1987 entry[afirst] = (png_byte)green;
1988 break;
1989
1990 default:
1991 break;
1992 }
1993 }
1994
1995 # ifdef afirst
1996 # undef afirst
1997 # endif
1998 # ifdef bgr
1999 # undef bgr
2000 # endif
2001 }
2002 }
2003
2004 static int
2005 make_gray_file_colormap(png_image_read_control *display)
2006 {
2007 unsigned int i;
2008
2009 for (i=0; i<256; ++i)
2010 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
2011
2012 return (int)i;
2013 }
2014
2015 static int
2016 make_gray_colormap(png_image_read_control *display)
2017 {
2018 unsigned int i;
2019
2020 for (i=0; i<256; ++i)
2021 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
2022
2023 return (int)i;
2024 }
2025 #define PNG_GRAY_COLORMAP_ENTRIES 256
2026
2027 static int
2028 make_ga_colormap(png_image_read_control *display)
2029 {
2030 unsigned int i, a;
2031
2032 /* Alpha is retained, the output will be a color-map with entries
2033 * selected by six levels of alpha. One transparent entry, 6 gray
2034 * levels for all the intermediate alpha values, leaving 230 entries
2035 * for the opaque grays. The color-map entries are the six values
2036 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2037 * relevant entry.
2038 *
2039 * if (alpha > 229) // opaque
2040 * {
2041 * // The 231 entries are selected to make the math below work:
2042 * base = 0;
2043 * entry = (231 * gray + 128) >> 8;
2044 * }
2045 * else if (alpha < 26) // transparent
2046 * {
2047 * base = 231;
2048 * entry = 0;
2049 * }
2050 * else // partially opaque
2051 * {
2052 * base = 226 + 6 * PNG_DIV51(alpha);
2053 * entry = PNG_DIV51(gray);
2054 * }
2055 */
2056 i = 0;
2057 while (i < 231)
2058 {
2059 unsigned int gray = (i * 256 + 115) / 231;
2060 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2061 }
2062
2063 /* 255 is used here for the component values for consistency with the code
2064 * that undoes premultiplication in pngwrite.c.
2065 */
2066 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2067
2068 for (a=1; a<5; ++a)
2069 {
2070 unsigned int g;
2071
2072 for (g=0; g<6; ++g)
2073 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2074 P_sRGB);
2075 }
2076
2077 return (int)i;
2078 }
2079
2080 #define PNG_GA_COLORMAP_ENTRIES 256
2081
2082 static int
2083 make_rgb_colormap(png_image_read_control *display)
2084 {
2085 unsigned int i, r;
2086
2087 /* Build a 6x6x6 opaque RGB cube */
2088 for (i=r=0; r<6; ++r)
2089 {
2090 unsigned int g;
2091
2092 for (g=0; g<6; ++g)
2093 {
2094 unsigned int b;
2095
2096 for (b=0; b<6; ++b)
2097 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2098 P_sRGB);
2099 }
2100 }
2101
2102 return (int)i;
2103 }
2104
2105 #define PNG_RGB_COLORMAP_ENTRIES 216
2106
2107 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2108 #define PNG_RGB_INDEX(r,g,b) \
2109 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2110
2111 static int
2112 png_image_read_colormap(png_voidp argument)
2113 {
2114 png_image_read_control *display =
2115 png_voidcast(png_image_read_control*, argument);
2116 const png_imagep image = display->image;
2117
2118 const png_structrp png_ptr = image->opaque->png_ptr;
2119 const png_uint_32 output_format = image->format;
2120 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2121 P_LINEAR : P_sRGB;
2122
2123 unsigned int cmap_entries;
2124 unsigned int output_processing; /* Output processing option */
2125 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2126
2127 /* Background information; the background color and the index of this color
2128 * in the color-map if it exists (else 256).
2129 */
2130 unsigned int background_index = 256;
2131 png_uint_32 back_r, back_g, back_b;
2132
2133 /* Flags to accumulate things that need to be done to the input. */
2134 int expand_tRNS = 0;
2135
2136 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2137 * very difficult to do, the results look awful, and it is difficult to see
2138 * what possible use it is because the application can't control the
2139 * color-map.
2140 */
2141 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2142 png_ptr->num_trans > 0) /* alpha in input */ &&
2143 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2144 {
2145 if (output_encoding == P_LINEAR) /* compose on black */
2146 back_b = back_g = back_r = 0;
2147
2148 else if (display->background == NULL /* no way to remove it */)
2149 png_error(png_ptr,
2150 "background color must be supplied to remove alpha/transparency");
2151
2152 /* Get a copy of the background color (this avoids repeating the checks
2153 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2154 * output format.
2155 */
2156 else
2157 {
2158 back_g = display->background->green;
2159 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2160 {
2161 back_r = display->background->red;
2162 back_b = display->background->blue;
2163 }
2164 else
2165 back_b = back_r = back_g;
2166 }
2167 }
2168
2169 else if (output_encoding == P_LINEAR)
2170 back_b = back_r = back_g = 65535;
2171
2172 else
2173 back_b = back_r = back_g = 255;
2174
2175 /* Default the input file gamma if required - this is necessary because
2176 * libpng assumes that if no gamma information is present the data is in the
2177 * output format, but the simplified API deduces the gamma from the input
2178 * format.
2179 */
2180 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2181 {
2182 /* Do this directly, not using the png_colorspace functions, to ensure
2183 * that it happens even if the colorspace is invalid (though probably if
2184 * it is the setting will be ignored) Note that the same thing can be
2185 * achieved at the application interface with png_set_gAMA.
2186 */
2187 if (png_ptr->bit_depth == 16 &&
2188 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2189 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2190
2191 else
2192 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2193
2194 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2195 }
2196
2197 /* Decide what to do based on the PNG color type of the input data. The
2198 * utility function png_create_colormap_entry deals with most aspects of the
2199 * output transformations; this code works out how to produce bytes of
2200 * color-map entries from the original format.
2201 */
2202 switch (png_ptr->color_type)
2203 {
2204 case PNG_COLOR_TYPE_GRAY:
2205 if (png_ptr->bit_depth <= 8)
2206 {
2207 /* There at most 256 colors in the output, regardless of
2208 * transparency.
2209 */
2210 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2211
2212 cmap_entries = 1U << png_ptr->bit_depth;
2213 if (cmap_entries > image->colormap_entries)
2214 png_error(png_ptr, "gray[8] color-map: too few entries");
2215
2216 step = 255 / (cmap_entries - 1);
2217 output_processing = PNG_CMAP_NONE;
2218
2219 /* If there is a tRNS chunk then this either selects a transparent
2220 * value or, if the output has no alpha, the background color.
2221 */
2222 if (png_ptr->num_trans > 0)
2223 {
2224 trans = png_ptr->trans_color.gray;
2225
2226 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2227 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2228 }
2229
2230 /* png_create_colormap_entry just takes an RGBA and writes the
2231 * corresponding color-map entry using the format from 'image',
2232 * including the required conversion to sRGB or linear as
2233 * appropriate. The input values are always either sRGB (if the
2234 * gamma correction flag is 0) or 0..255 scaled file encoded values
2235 * (if the function must gamma correct them).
2236 */
2237 for (i=val=0; i<cmap_entries; ++i, val += step)
2238 {
2239 /* 'i' is a file value. While this will result in duplicated
2240 * entries for 8-bit non-sRGB encoded files it is necessary to
2241 * have non-gamma corrected values to do tRNS handling.
2242 */
2243 if (i != trans)
2244 png_create_colormap_entry(display, i, val, val, val, 255,
2245 P_FILE/*8-bit with file gamma*/);
2246
2247 /* Else this entry is transparent. The colors don't matter if
2248 * there is an alpha channel (back_alpha == 0), but it does no
2249 * harm to pass them in; the values are not set above so this
2250 * passes in white.
2251 *
2252 * NOTE: this preserves the full precision of the application
2253 * supplied background color when it is used.
2254 */
2255 else
2256 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2257 back_alpha, output_encoding);
2258 }
2259
2260 /* We need libpng to preserve the original encoding. */
2261 data_encoding = P_FILE;
2262
2263 /* The rows from libpng, while technically gray values, are now also
2264 * color-map indices; however, they may need to be expanded to 1
2265 * byte per pixel. This is what png_set_packing does (i.e., it
2266 * unpacks the bit values into bytes.)
2267 */
2268 if (png_ptr->bit_depth < 8)
2269 png_set_packing(png_ptr);
2270 }
2271
2272 else /* bit depth is 16 */
2273 {
2274 /* The 16-bit input values can be converted directly to 8-bit gamma
2275 * encoded values; however, if a tRNS chunk is present 257 color-map
2276 * entries are required. This means that the extra entry requires
2277 * special processing; add an alpha channel, sacrifice gray level
2278 * 254 and convert transparent (alpha==0) entries to that.
2279 *
2280 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2281 * same time to minimize quality loss. If a tRNS chunk is present
2282 * this means libpng must handle it too; otherwise it is impossible
2283 * to do the exact match on the 16-bit value.
2284 *
2285 * If the output has no alpha channel *and* the background color is
2286 * gray then it is possible to let libpng handle the substitution by
2287 * ensuring that the corresponding gray level matches the background
2288 * color exactly.
2289 */
2290 data_encoding = P_sRGB;
2291
2292 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2293 png_error(png_ptr, "gray[16] color-map: too few entries");
2294
2295 cmap_entries = (unsigned int)make_gray_colormap(display);
2296
2297 if (png_ptr->num_trans > 0)
2298 {
2299 unsigned int back_alpha;
2300
2301 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2302 back_alpha = 0;
2303
2304 else
2305 {
2306 if (back_r == back_g && back_g == back_b)
2307 {
2308 /* Background is gray; no special processing will be
2309 * required.
2310 */
2311 png_color_16 c;
2312 png_uint_32 gray = back_g;
2313
2314 if (output_encoding == P_LINEAR)
2315 {
2316 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2317
2318 /* And make sure the corresponding palette entry
2319 * matches.
2320 */
2321 png_create_colormap_entry(display, gray, back_g, back_g,
2322 back_g, 65535, P_LINEAR);
2323 }
2324
2325 /* The background passed to libpng, however, must be the
2326 * sRGB value.
2327 */
2328 c.index = 0; /*unused*/
2329 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2330
2331 /* NOTE: does this work without expanding tRNS to alpha?
2332 * It should be the color->gray case below apparently
2333 * doesn't.
2334 */
2335 png_set_background_fixed(png_ptr, &c,
2336 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2337 0/*gamma: not used*/);
2338
2339 output_processing = PNG_CMAP_NONE;
2340 break;
2341 }
2342 #ifdef __COVERITY__
2343 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2344 * here.
2345 */
2346 back_alpha = 255;
2347 #else
2348 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2349 #endif
2350 }
2351
2352 /* output_processing means that the libpng-processed row will be
2353 * 8-bit GA and it has to be processing to single byte color-map
2354 * values. Entry 254 is replaced by either a completely
2355 * transparent entry or by the background color at full
2356 * precision (and the background color is not a simple gray
2357 * level in this case.)
2358 */
2359 expand_tRNS = 1;
2360 output_processing = PNG_CMAP_TRANS;
2361 background_index = 254;
2362
2363 /* And set (overwrite) color-map entry 254 to the actual
2364 * background color at full precision.
2365 */
2366 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2367 back_alpha, output_encoding);
2368 }
2369
2370 else
2371 output_processing = PNG_CMAP_NONE;
2372 }
2373 break;
2374
2375 case PNG_COLOR_TYPE_GRAY_ALPHA:
2376 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2377 * of 65536 combinations. If, however, the alpha channel is to be
2378 * removed there are only 256 possibilities if the background is gray.
2379 * (Otherwise there is a subset of the 65536 possibilities defined by
2380 * the triangle between black, white and the background color.)
2381 *
2382 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2383 * worry about tRNS matching - tRNS is ignored if there is an alpha
2384 * channel.
2385 */
2386 data_encoding = P_sRGB;
2387
2388 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2389 {
2390 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2391 png_error(png_ptr, "gray+alpha color-map: too few entries");
2392
2393 cmap_entries = (unsigned int)make_ga_colormap(display);
2394
2395 background_index = PNG_CMAP_GA_BACKGROUND;
2396 output_processing = PNG_CMAP_GA;
2397 }
2398
2399 else /* alpha is removed */
2400 {
2401 /* Alpha must be removed as the PNG data is processed when the
2402 * background is a color because the G and A channels are
2403 * independent and the vector addition (non-parallel vectors) is a
2404 * 2-D problem.
2405 *
2406 * This can be reduced to the same algorithm as above by making a
2407 * colormap containing gray levels (for the opaque grays), a
2408 * background entry (for a transparent pixel) and a set of four six
2409 * level color values, one set for each intermediate alpha value.
2410 * See the comments in make_ga_colormap for how this works in the
2411 * per-pixel processing.
2412 *
2413 * If the background is gray, however, we only need a 256 entry gray
2414 * level color map. It is sufficient to make the entry generated
2415 * for the background color be exactly the color specified.
2416 */
2417 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2418 (back_r == back_g && back_g == back_b))
2419 {
2420 /* Background is gray; no special processing will be required. */
2421 png_color_16 c;
2422 png_uint_32 gray = back_g;
2423
2424 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2425 png_error(png_ptr, "gray-alpha color-map: too few entries");
2426
2427 cmap_entries = (unsigned int)make_gray_colormap(display);
2428
2429 if (output_encoding == P_LINEAR)
2430 {
2431 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2432
2433 /* And make sure the corresponding palette entry matches. */
2434 png_create_colormap_entry(display, gray, back_g, back_g,
2435 back_g, 65535, P_LINEAR);
2436 }
2437
2438 /* The background passed to libpng, however, must be the sRGB
2439 * value.
2440 */
2441 c.index = 0; /*unused*/
2442 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2443
2444 png_set_background_fixed(png_ptr, &c,
2445 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2446 0/*gamma: not used*/);
2447
2448 output_processing = PNG_CMAP_NONE;
2449 }
2450
2451 else
2452 {
2453 png_uint_32 i, a;
2454
2455 /* This is the same as png_make_ga_colormap, above, except that
2456 * the entries are all opaque.
2457 */
2458 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2459 png_error(png_ptr, "ga-alpha color-map: too few entries");
2460
2461 i = 0;
2462 while (i < 231)
2463 {
2464 png_uint_32 gray = (i * 256 + 115) / 231;
2465 png_create_colormap_entry(display, i++, gray, gray, gray,
2466 255, P_sRGB);
2467 }
2468
2469 /* NOTE: this preserves the full precision of the application
2470 * background color.
2471 */
2472 background_index = i;
2473 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2474 #ifdef __COVERITY__
2475 /* Coverity claims that output_encoding
2476 * cannot be 2 (P_LINEAR) here.
2477 */ 255U,
2478 #else
2479 output_encoding == P_LINEAR ? 65535U : 255U,
2480 #endif
2481 output_encoding);
2482
2483 /* For non-opaque input composite on the sRGB background - this
2484 * requires inverting the encoding for each component. The input
2485 * is still converted to the sRGB encoding because this is a
2486 * reasonable approximate to the logarithmic curve of human
2487 * visual sensitivity, at least over the narrow range which PNG
2488 * represents. Consequently 'G' is always sRGB encoded, while
2489 * 'A' is linear. We need the linear background colors.
2490 */
2491 if (output_encoding == P_sRGB) /* else already linear */
2492 {
2493 /* This may produce a value not exactly matching the
2494 * background, but that's ok because these numbers are only
2495 * used when alpha != 0
2496 */
2497 back_r = png_sRGB_table[back_r];
2498 back_g = png_sRGB_table[back_g];
2499 back_b = png_sRGB_table[back_b];
2500 }
2501
2502 for (a=1; a<5; ++a)
2503 {
2504 unsigned int g;
2505
2506 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2507 * by an 8-bit alpha value (0..255).
2508 */
2509 png_uint_32 alpha = 51 * a;
2510 png_uint_32 back_rx = (255-alpha) * back_r;
2511 png_uint_32 back_gx = (255-alpha) * back_g;
2512 png_uint_32 back_bx = (255-alpha) * back_b;
2513
2514 for (g=0; g<6; ++g)
2515 {
2516 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2517
2518 png_create_colormap_entry(display, i++,
2519 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2520 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2521 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2522 }
2523 }
2524
2525 cmap_entries = i;
2526 output_processing = PNG_CMAP_GA;
2527 }
2528 }
2529 break;
2530
2531 case PNG_COLOR_TYPE_RGB:
2532 case PNG_COLOR_TYPE_RGB_ALPHA:
2533 /* Exclude the case where the output is gray; we can always handle this
2534 * with the cases above.
2535 */
2536 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2537 {
2538 /* The color-map will be grayscale, so we may as well convert the
2539 * input RGB values to a simple grayscale and use the grayscale
2540 * code above.
2541 *
2542 * NOTE: calling this apparently damages the recognition of the
2543 * transparent color in background color handling; call
2544 * png_set_tRNS_to_alpha before png_set_background_fixed.
2545 */
2546 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2547 -1);
2548 data_encoding = P_sRGB;
2549
2550 /* The output will now be one or two 8-bit gray or gray+alpha
2551 * channels. The more complex case arises when the input has alpha.
2552 */
2553 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2554 png_ptr->num_trans > 0) &&
2555 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2556 {
2557 /* Both input and output have an alpha channel, so no background
2558 * processing is required; just map the GA bytes to the right
2559 * color-map entry.
2560 */
2561 expand_tRNS = 1;
2562
2563 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2564 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2565
2566 cmap_entries = (unsigned int)make_ga_colormap(display);
2567 background_index = PNG_CMAP_GA_BACKGROUND;
2568 output_processing = PNG_CMAP_GA;
2569 }
2570
2571 else
2572 {
2573 /* Either the input or the output has no alpha channel, so there
2574 * will be no non-opaque pixels in the color-map; it will just be
2575 * grayscale.
2576 */
2577 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2578 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2579
2580 /* Ideally this code would use libpng to do the gamma correction,
2581 * but if an input alpha channel is to be removed we will hit the
2582 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2583 * correction bug). Fix this by dropping the gamma correction in
2584 * this case and doing it in the palette; this will result in
2585 * duplicate palette entries, but that's better than the
2586 * alternative of double gamma correction.
2587 */
2588 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2589 png_ptr->num_trans > 0) &&
2590 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2591 {
2592 cmap_entries = (unsigned int)make_gray_file_colormap(display);
2593 data_encoding = P_FILE;
2594 }
2595
2596 else
2597 cmap_entries = (unsigned int)make_gray_colormap(display);
2598
2599 /* But if the input has alpha or transparency it must be removed
2600 */
2601 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2602 png_ptr->num_trans > 0)
2603 {
2604 png_color_16 c;
2605 png_uint_32 gray = back_g;
2606
2607 /* We need to ensure that the application background exists in
2608 * the colormap and that completely transparent pixels map to
2609 * it. Achieve this simply by ensuring that the entry
2610 * selected for the background really is the background color.
2611 */
2612 if (data_encoding == P_FILE) /* from the fixup above */
2613 {
2614 /* The app supplied a gray which is in output_encoding, we
2615 * need to convert it to a value of the input (P_FILE)
2616 * encoding then set this palette entry to the required
2617 * output encoding.
2618 */
2619 if (output_encoding == P_sRGB)
2620 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2621
2622 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2623 png_ptr->colorspace.gamma)); /* now P_FILE */
2624
2625 /* And make sure the corresponding palette entry contains
2626 * exactly the required sRGB value.
2627 */
2628 png_create_colormap_entry(display, gray, back_g, back_g,
2629 back_g, 0/*unused*/, output_encoding);
2630 }
2631
2632 else if (output_encoding == P_LINEAR)
2633 {
2634 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2635
2636 /* And make sure the corresponding palette entry matches.
2637 */
2638 png_create_colormap_entry(display, gray, back_g, back_g,
2639 back_g, 0/*unused*/, P_LINEAR);
2640 }
2641
2642 /* The background passed to libpng, however, must be the
2643 * output (normally sRGB) value.
2644 */
2645 c.index = 0; /*unused*/
2646 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2647
2648 /* NOTE: the following is apparently a bug in libpng. Without
2649 * it the transparent color recognition in
2650 * png_set_background_fixed seems to go wrong.
2651 */
2652 expand_tRNS = 1;
2653 png_set_background_fixed(png_ptr, &c,
2654 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2655 0/*gamma: not used*/);
2656 }
2657
2658 output_processing = PNG_CMAP_NONE;
2659 }
2660 }
2661
2662 else /* output is color */
2663 {
2664 /* We could use png_quantize here so long as there is no transparent
2665 * color or alpha; png_quantize ignores alpha. Easier overall just
2666 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2667 * Consequently we always want libpng to produce sRGB data.
2668 */
2669 data_encoding = P_sRGB;
2670
2671 /* Is there any transparency or alpha? */
2672 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2673 png_ptr->num_trans > 0)
2674 {
2675 /* Is there alpha in the output too? If so all four channels are
2676 * processed into a special RGB cube with alpha support.
2677 */
2678 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2679 {
2680 png_uint_32 r;
2681
2682 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2683 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2684
2685 cmap_entries = (unsigned int)make_rgb_colormap(display);
2686
2687 /* Add a transparent entry. */
2688 png_create_colormap_entry(display, cmap_entries, 255, 255,
2689 255, 0, P_sRGB);
2690
2691 /* This is stored as the background index for the processing
2692 * algorithm.
2693 */
2694 background_index = cmap_entries++;
2695
2696 /* Add 27 r,g,b entries each with alpha 0.5. */
2697 for (r=0; r<256; r = (r << 1) | 0x7f)
2698 {
2699 png_uint_32 g;
2700
2701 for (g=0; g<256; g = (g << 1) | 0x7f)
2702 {
2703 png_uint_32 b;
2704
2705 /* This generates components with the values 0, 127 and
2706 * 255
2707 */
2708 for (b=0; b<256; b = (b << 1) | 0x7f)
2709 png_create_colormap_entry(display, cmap_entries++,
2710 r, g, b, 128, P_sRGB);
2711 }
2712 }
2713
2714 expand_tRNS = 1;
2715 output_processing = PNG_CMAP_RGB_ALPHA;
2716 }
2717
2718 else
2719 {
2720 /* Alpha/transparency must be removed. The background must
2721 * exist in the color map (achieved by setting adding it after
2722 * the 666 color-map). If the standard processing code will
2723 * pick up this entry automatically that's all that is
2724 * required; libpng can be called to do the background
2725 * processing.
2726 */
2727 unsigned int sample_size =
2728 PNG_IMAGE_SAMPLE_SIZE(output_format);
2729 png_uint_32 r, g, b; /* sRGB background */
2730
2731 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2732 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2733
2734 cmap_entries = (unsigned int)make_rgb_colormap(display);
2735
2736 png_create_colormap_entry(display, cmap_entries, back_r,
2737 back_g, back_b, 0/*unused*/, output_encoding);
2738
2739 if (output_encoding == P_LINEAR)
2740 {
2741 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2742 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2743 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2744 }
2745
2746 else
2747 {
2748 r = back_r;
2749 g = back_g;
2750 b = back_g;
2751 }
2752
2753 /* Compare the newly-created color-map entry with the one the
2754 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2755 * match, add the new one and set this as the background
2756 * index.
2757 */
2758 if (memcmp((png_const_bytep)display->colormap +
2759 sample_size * cmap_entries,
2760 (png_const_bytep)display->colormap +
2761 sample_size * PNG_RGB_INDEX(r,g,b),
2762 sample_size) != 0)
2763 {
2764 /* The background color must be added. */
2765 background_index = cmap_entries++;
2766
2767 /* Add 27 r,g,b entries each with created by composing with
2768 * the background at alpha 0.5.
2769 */
2770 for (r=0; r<256; r = (r << 1) | 0x7f)
2771 {
2772 for (g=0; g<256; g = (g << 1) | 0x7f)
2773 {
2774 /* This generates components with the values 0, 127
2775 * and 255
2776 */
2777 for (b=0; b<256; b = (b << 1) | 0x7f)
2778 png_create_colormap_entry(display, cmap_entries++,
2779 png_colormap_compose(display, r, P_sRGB, 128,
2780 back_r, output_encoding),
2781 png_colormap_compose(display, g, P_sRGB, 128,
2782 back_g, output_encoding),
2783 png_colormap_compose(display, b, P_sRGB, 128,
2784 back_b, output_encoding),
2785 0/*unused*/, output_encoding);
2786 }
2787 }
2788
2789 expand_tRNS = 1;
2790 output_processing = PNG_CMAP_RGB_ALPHA;
2791 }
2792
2793 else /* background color is in the standard color-map */
2794 {
2795 png_color_16 c;
2796
2797 c.index = 0; /*unused*/
2798 c.red = (png_uint_16)back_r;
2799 c.gray = c.green = (png_uint_16)back_g;
2800 c.blue = (png_uint_16)back_b;
2801
2802 png_set_background_fixed(png_ptr, &c,
2803 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2804 0/*gamma: not used*/);
2805
2806 output_processing = PNG_CMAP_RGB;
2807 }
2808 }
2809 }
2810
2811 else /* no alpha or transparency in the input */
2812 {
2813 /* Alpha in the output is irrelevant, simply map the opaque input
2814 * pixels to the 6x6x6 color-map.
2815 */
2816 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2817 png_error(png_ptr, "rgb color-map: too few entries");
2818
2819 cmap_entries = (unsigned int)make_rgb_colormap(display);
2820 output_processing = PNG_CMAP_RGB;
2821 }
2822 }
2823 break;
2824
2825 case PNG_COLOR_TYPE_PALETTE:
2826 /* It's already got a color-map. It may be necessary to eliminate the
2827 * tRNS entries though.
2828 */
2829 {
2830 unsigned int num_trans = png_ptr->num_trans;
2831 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2832 png_const_colorp colormap = png_ptr->palette;
2833 const int do_background = trans != NULL &&
2834 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2835 unsigned int i;
2836
2837 /* Just in case: */
2838 if (trans == NULL)
2839 num_trans = 0;
2840
2841 output_processing = PNG_CMAP_NONE;
2842 data_encoding = P_FILE; /* Don't change from color-map indices */
2843 cmap_entries = (unsigned int)png_ptr->num_palette;
2844 if (cmap_entries > 256)
2845 cmap_entries = 256;
2846
2847 if (cmap_entries > (unsigned int)image->colormap_entries)
2848 png_error(png_ptr, "palette color-map: too few entries");
2849
2850 for (i=0; i < cmap_entries; ++i)
2851 {
2852 if (do_background != 0 && i < num_trans && trans[i] < 255)
2853 {
2854 if (trans[i] == 0)
2855 png_create_colormap_entry(display, i, back_r, back_g,
2856 back_b, 0, output_encoding);
2857
2858 else
2859 {
2860 /* Must compose the PNG file color in the color-map entry
2861 * on the sRGB color in 'back'.
2862 */
2863 png_create_colormap_entry(display, i,
2864 png_colormap_compose(display, colormap[i].red,
2865 P_FILE, trans[i], back_r, output_encoding),
2866 png_colormap_compose(display, colormap[i].green,
2867 P_FILE, trans[i], back_g, output_encoding),
2868 png_colormap_compose(display, colormap[i].blue,
2869 P_FILE, trans[i], back_b, output_encoding),
2870 output_encoding == P_LINEAR ? trans[i] * 257U :
2871 trans[i],
2872 output_encoding);
2873 }
2874 }
2875
2876 else
2877 png_create_colormap_entry(display, i, colormap[i].red,
2878 colormap[i].green, colormap[i].blue,
2879 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2880 }
2881
2882 /* The PNG data may have indices packed in fewer than 8 bits, it
2883 * must be expanded if so.
2884 */
2885 if (png_ptr->bit_depth < 8)
2886 png_set_packing(png_ptr);
2887 }
2888 break;
2889
2890 default:
2891 png_error(png_ptr, "invalid PNG color type");
2892 /*NOT REACHED*/
2893 }
2894
2895 /* Now deal with the output processing */
2896 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2897 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2898 png_set_tRNS_to_alpha(png_ptr);
2899
2900 switch (data_encoding)
2901 {
2902 case P_sRGB:
2903 /* Change to 8-bit sRGB */
2904 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2905 /* FALLTHROUGH */
2906
2907 case P_FILE:
2908 if (png_ptr->bit_depth > 8)
2909 png_set_scale_16(png_ptr);
2910 break;
2911
2912 #ifdef __GNUC__
2913 default:
2914 png_error(png_ptr, "bad data option (internal error)");
2915 #endif
2916 }
2917
2918 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2919 png_error(png_ptr, "color map overflow (BAD internal error)");
2920
2921 image->colormap_entries = cmap_entries;
2922
2923 /* Double check using the recorded background index */
2924 switch (output_processing)
2925 {
2926 case PNG_CMAP_NONE:
2927 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2928 goto bad_background;
2929 break;
2930
2931 case PNG_CMAP_GA:
2932 if (background_index != PNG_CMAP_GA_BACKGROUND)
2933 goto bad_background;
2934 break;
2935
2936 case PNG_CMAP_TRANS:
2937 if (background_index >= cmap_entries ||
2938 background_index != PNG_CMAP_TRANS_BACKGROUND)
2939 goto bad_background;
2940 break;
2941
2942 case PNG_CMAP_RGB:
2943 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2944 goto bad_background;
2945 break;
2946
2947 case PNG_CMAP_RGB_ALPHA:
2948 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2949 goto bad_background;
2950 break;
2951
2952 default:
2953 png_error(png_ptr, "bad processing option (internal error)");
2954
2955 bad_background:
2956 png_error(png_ptr, "bad background index (internal error)");
2957 }
2958
2959 display->colormap_processing = (int)output_processing;
2960
2961 return 1/*ok*/;
2962 }
2963
2964 /* The final part of the color-map read called from png_image_finish_read. */
2965 static int
2966 png_image_read_and_map(png_voidp argument)
2967 {
2968 png_image_read_control *display = png_voidcast(png_image_read_control*,
2969 argument);
2970 png_imagep image = display->image;
2971 png_structrp png_ptr = image->opaque->png_ptr;
2972 int passes;
2973
2974 /* Called when the libpng data must be transformed into the color-mapped
2975 * form. There is a local row buffer in display->local and this routine must
2976 * do the interlace handling.
2977 */
2978 switch (png_ptr->interlaced)
2979 {
2980 case PNG_INTERLACE_NONE:
2981 passes = 1;
2982 break;
2983
2984 case PNG_INTERLACE_ADAM7:
2985 passes = PNG_INTERLACE_ADAM7_PASSES;
2986 break;
2987
2988 default:
2989 png_error(png_ptr, "unknown interlace type");
2990 }
2991
2992 {
2993 png_uint_32 height = image->height;
2994 png_uint_32 width = image->width;
2995 int proc = display->colormap_processing;
2996 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2997 ptrdiff_t step_row = display->row_bytes;
2998 int pass;
2999
3000 for (pass = 0; pass < passes; ++pass)
3001 {
3002 unsigned int startx, stepx, stepy;
3003 png_uint_32 y;
3004
3005 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3006 {
3007 /* The row may be empty for a short image: */
3008 if (PNG_PASS_COLS(width, pass) == 0)
3009 continue;
3010
3011 startx = PNG_PASS_START_COL(pass);
3012 stepx = PNG_PASS_COL_OFFSET(pass);
3013 y = PNG_PASS_START_ROW(pass);
3014 stepy = PNG_PASS_ROW_OFFSET(pass);
3015 }
3016
3017 else
3018 {
3019 y = 0;
3020 startx = 0;
3021 stepx = stepy = 1;
3022 }
3023
3024 for (; y<height; y += stepy)
3025 {
3026 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3027 png_bytep outrow = first_row + y * step_row;
3028 png_const_bytep end_row = outrow + width;
3029
3030 /* Read read the libpng data into the temporary buffer. */
3031 png_read_row(png_ptr, inrow, NULL);
3032
3033 /* Now process the row according to the processing option, note
3034 * that the caller verifies that the format of the libpng output
3035 * data is as required.
3036 */
3037 outrow += startx;
3038 switch (proc)
3039 {
3040 case PNG_CMAP_GA:
3041 for (; outrow < end_row; outrow += stepx)
3042 {
3043 /* The data is always in the PNG order */
3044 unsigned int gray = *inrow++;
3045 unsigned int alpha = *inrow++;
3046 unsigned int entry;
3047
3048 /* NOTE: this code is copied as a comment in
3049 * make_ga_colormap above. Please update the
3050 * comment if you change this code!
3051 */
3052 if (alpha > 229) /* opaque */
3053 {
3054 entry = (231 * gray + 128) >> 8;
3055 }
3056 else if (alpha < 26) /* transparent */
3057 {
3058 entry = 231;
3059 }
3060 else /* partially opaque */
3061 {
3062 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3063 }
3064
3065 *outrow = (png_byte)entry;
3066 }
3067 break;
3068
3069 case PNG_CMAP_TRANS:
3070 for (; outrow < end_row; outrow += stepx)
3071 {
3072 png_byte gray = *inrow++;
3073 png_byte alpha = *inrow++;
3074
3075 if (alpha == 0)
3076 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3077
3078 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3079 *outrow = gray;
3080
3081 else
3082 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3083 }
3084 break;
3085
3086 case PNG_CMAP_RGB:
3087 for (; outrow < end_row; outrow += stepx)
3088 {
3089 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3090 inrow += 3;
3091 }
3092 break;
3093
3094 case PNG_CMAP_RGB_ALPHA:
3095 for (; outrow < end_row; outrow += stepx)
3096 {
3097 unsigned int alpha = inrow[3];
3098
3099 /* Because the alpha entries only hold alpha==0.5 values
3100 * split the processing at alpha==0.25 (64) and 0.75
3101 * (196).
3102 */
3103
3104 if (alpha >= 196)
3105 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3106 inrow[2]);
3107
3108 else if (alpha < 64)
3109 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3110
3111 else
3112 {
3113 /* Likewise there are three entries for each of r, g
3114 * and b. We could select the entry by popcount on
3115 * the top two bits on those architectures that
3116 * support it, this is what the code below does,
3117 * crudely.
3118 */
3119 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3120
3121 /* Here are how the values map:
3122 *
3123 * 0x00 .. 0x3f -> 0
3124 * 0x40 .. 0xbf -> 1
3125 * 0xc0 .. 0xff -> 2
3126 *
3127 * So, as above with the explicit alpha checks, the
3128 * breakpoints are at 64 and 196.
3129 */
3130 if (inrow[0] & 0x80) back_i += 9; /* red */
3131 if (inrow[0] & 0x40) back_i += 9;
3132 if (inrow[0] & 0x80) back_i += 3; /* green */
3133 if (inrow[0] & 0x40) back_i += 3;
3134 if (inrow[0] & 0x80) back_i += 1; /* blue */
3135 if (inrow[0] & 0x40) back_i += 1;
3136
3137 *outrow = (png_byte)back_i;
3138 }
3139
3140 inrow += 4;
3141 }
3142 break;
3143
3144 default:
3145 break;
3146 }
3147 }
3148 }
3149 }
3150
3151 return 1;
3152 }
3153
3154 static int
3155 png_image_read_colormapped(png_voidp argument)
3156 {
3157 png_image_read_control *display = png_voidcast(png_image_read_control*,
3158 argument);
3159 png_imagep image = display->image;
3160 png_controlp control = image->opaque;
3161 png_structrp png_ptr = control->png_ptr;
3162 png_inforp info_ptr = control->info_ptr;
3163
3164 int passes = 0; /* As a flag */
3165
3166 PNG_SKIP_CHUNKS(png_ptr);
3167
3168 /* Update the 'info' structure and make sure the result is as required; first
3169 * make sure to turn on the interlace handling if it will be required
3170 * (because it can't be turned on *after* the call to png_read_update_info!)
3171 */
3172 if (display->colormap_processing == PNG_CMAP_NONE)
3173 passes = png_set_interlace_handling(png_ptr);
3174
3175 png_read_update_info(png_ptr, info_ptr);
3176
3177 /* The expected output can be deduced from the colormap_processing option. */
3178 switch (display->colormap_processing)
3179 {
3180 case PNG_CMAP_NONE:
3181 /* Output must be one channel and one byte per pixel, the output
3182 * encoding can be anything.
3183 */
3184 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3185 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3186 info_ptr->bit_depth == 8)
3187 break;
3188
3189 goto bad_output;
3190
3191 case PNG_CMAP_TRANS:
3192 case PNG_CMAP_GA:
3193 /* Output must be two channels and the 'G' one must be sRGB, the latter
3194 * can be checked with an exact number because it should have been set
3195 * to this number above!
3196 */
3197 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3198 info_ptr->bit_depth == 8 &&
3199 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3200 image->colormap_entries == 256)
3201 break;
3202
3203 goto bad_output;
3204
3205 case PNG_CMAP_RGB:
3206 /* Output must be 8-bit sRGB encoded RGB */
3207 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3208 info_ptr->bit_depth == 8 &&
3209 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3210 image->colormap_entries == 216)
3211 break;
3212
3213 goto bad_output;
3214
3215 case PNG_CMAP_RGB_ALPHA:
3216 /* Output must be 8-bit sRGB encoded RGBA */
3217 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3218 info_ptr->bit_depth == 8 &&
3219 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3220 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3221 break;
3222
3223 goto bad_output;
3224
3225 default:
3226 bad_output:
3227 png_error(png_ptr, "bad color-map processing (internal error)");
3228 }
3229
3230 /* Now read the rows. Do this here if it is possible to read directly into
3231 * the output buffer, otherwise allocate a local row buffer of the maximum
3232 * size libpng requires and call the relevant processing routine safely.
3233 */
3234 {
3235 png_voidp first_row = display->buffer;
3236 ptrdiff_t row_bytes = display->row_stride;
3237
3238 /* The following expression is designed to work correctly whether it gives
3239 * a signed or an unsigned result.
3240 */
3241 if (row_bytes < 0)
3242 {
3243 char *ptr = png_voidcast(char*, first_row);
3244 ptr += (image->height-1) * (-row_bytes);
3245 first_row = png_voidcast(png_voidp, ptr);
3246 }
3247
3248 display->first_row = first_row;
3249 display->row_bytes = row_bytes;
3250 }
3251
3252 if (passes == 0)
3253 {
3254 int result;
3255 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3256
3257 display->local_row = row;
3258 result = png_safe_execute(image, png_image_read_and_map, display);
3259 display->local_row = NULL;
3260 png_free(png_ptr, row);
3261
3262 return result;
3263 }
3264
3265 else
3266 {
3267 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
3268
3269 while (--passes >= 0)
3270 {
3271 png_uint_32 y = image->height;
3272 png_bytep row = png_voidcast(png_bytep, display->first_row);
3273
3274 for (; y > 0; --y)
3275 {
3276 png_read_row(png_ptr, row, NULL);
3277 row += row_bytes;
3278 }
3279 }
3280
3281 return 1;
3282 }
3283 }
3284
3285 /* Just the row reading part of png_image_read. */
3286 static int
3287 png_image_read_composite(png_voidp argument)
3288 {
3289 png_image_read_control *display = png_voidcast(png_image_read_control*,
3290 argument);
3291 png_imagep image = display->image;
3292 png_structrp png_ptr = image->opaque->png_ptr;
3293 int passes;
3294
3295 switch (png_ptr->interlaced)
3296 {
3297 case PNG_INTERLACE_NONE:
3298 passes = 1;
3299 break;
3300
3301 case PNG_INTERLACE_ADAM7:
3302 passes = PNG_INTERLACE_ADAM7_PASSES;
3303 break;
3304
3305 default:
3306 png_error(png_ptr, "unknown interlace type");
3307 }
3308
3309 {
3310 png_uint_32 height = image->height;
3311 png_uint_32 width = image->width;
3312 ptrdiff_t step_row = display->row_bytes;
3313 unsigned int channels =
3314 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3315 int pass;
3316
3317 for (pass = 0; pass < passes; ++pass)
3318 {
3319 unsigned int startx, stepx, stepy;
3320 png_uint_32 y;
3321
3322 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3323 {
3324 /* The row may be empty for a short image: */
3325 if (PNG_PASS_COLS(width, pass) == 0)
3326 continue;
3327
3328 startx = PNG_PASS_START_COL(pass) * channels;
3329 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3330 y = PNG_PASS_START_ROW(pass);
3331 stepy = PNG_PASS_ROW_OFFSET(pass);
3332 }
3333
3334 else
3335 {
3336 y = 0;
3337 startx = 0;
3338 stepx = channels;
3339 stepy = 1;
3340 }
3341
3342 for (; y<height; y += stepy)
3343 {
3344 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3345 png_bytep outrow;
3346 png_const_bytep end_row;
3347
3348 /* Read the row, which is packed: */
3349 png_read_row(png_ptr, inrow, NULL);
3350
3351 outrow = png_voidcast(png_bytep, display->first_row);
3352 outrow += y * step_row;
3353 end_row = outrow + width * channels;
3354
3355 /* Now do the composition on each pixel in this row. */
3356 outrow += startx;
3357 for (; outrow < end_row; outrow += stepx)
3358 {
3359 png_byte alpha = inrow[channels];
3360
3361 if (alpha > 0) /* else no change to the output */
3362 {
3363 unsigned int c;
3364
3365 for (c=0; c<channels; ++c)
3366 {
3367 png_uint_32 component = inrow[c];
3368
3369 if (alpha < 255) /* else just use component */
3370 {
3371 /* This is PNG_OPTIMIZED_ALPHA, the component value
3372 * is a linear 8-bit value. Combine this with the
3373 * current outrow[c] value which is sRGB encoded.
3374 * Arithmetic here is 16-bits to preserve the output
3375 * values correctly.
3376 */
3377 component *= 257*255; /* =65535 */
3378 component += (255-alpha)*png_sRGB_table[outrow[c]];
3379
3380 /* So 'component' is scaled by 255*65535 and is
3381 * therefore appropriate for the sRGB to linear
3382 * conversion table.
3383 */
3384 component = PNG_sRGB_FROM_LINEAR(component);
3385 }
3386
3387 outrow[c] = (png_byte)component;
3388 }
3389 }
3390
3391 inrow += channels+1; /* components and alpha channel */
3392 }
3393 }
3394 }
3395 }
3396
3397 return 1;
3398 }
3399
3400 /* The do_local_background case; called when all the following transforms are to
3401 * be done:
3402 *
3403 * PNG_RGB_TO_GRAY
3404 * PNG_COMPOSITE
3405 * PNG_GAMMA
3406 *
3407 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3408 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3409 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3410 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3411 * row and handles the removal or pre-multiplication of the alpha channel.
3412 */
3413 static int
3414 png_image_read_background(png_voidp argument)
3415 {
3416 png_image_read_control *display = png_voidcast(png_image_read_control*,
3417 argument);
3418 png_imagep image = display->image;
3419 png_structrp png_ptr = image->opaque->png_ptr;
3420 png_inforp info_ptr = image->opaque->info_ptr;
3421 png_uint_32 height = image->height;
3422 png_uint_32 width = image->width;
3423 int pass, passes;
3424
3425 /* Double check the convoluted logic below. We expect to get here with
3426 * libpng doing rgb to gray and gamma correction but background processing
3427 * left to the png_image_read_background function. The rows libpng produce
3428 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3429 */
3430 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3431 png_error(png_ptr, "lost rgb to gray");
3432
3433 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3434 png_error(png_ptr, "unexpected compose");
3435
3436 if (png_get_channels(png_ptr, info_ptr) != 2)
3437 png_error(png_ptr, "lost/gained channels");
3438
3439 /* Expect the 8-bit case to always remove the alpha channel */
3440 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3441 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3442 png_error(png_ptr, "unexpected 8-bit transformation");
3443
3444 switch (png_ptr->interlaced)
3445 {
3446 case PNG_INTERLACE_NONE:
3447 passes = 1;
3448 break;
3449
3450 case PNG_INTERLACE_ADAM7:
3451 passes = PNG_INTERLACE_ADAM7_PASSES;
3452 break;
3453
3454 default:
3455 png_error(png_ptr, "unknown interlace type");
3456 }
3457
3458 /* Use direct access to info_ptr here because otherwise the simplified API
3459 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3460 * checking the value after libpng expansions, not the original value in the
3461 * PNG.
3462 */
3463 switch (info_ptr->bit_depth)
3464 {
3465 case 8:
3466 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3467 * to be removed by composing on a background: either the row if
3468 * display->background is NULL or display->background->green if not.
3469 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3470 */
3471 {
3472 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3473 ptrdiff_t step_row = display->row_bytes;
3474
3475 for (pass = 0; pass < passes; ++pass)
3476 {
3477 png_bytep row = png_voidcast(png_bytep, display->first_row);
3478 unsigned int startx, stepx, stepy;
3479 png_uint_32 y;
3480
3481 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3482 {
3483 /* The row may be empty for a short image: */
3484 if (PNG_PASS_COLS(width, pass) == 0)
3485 continue;
3486
3487 startx = PNG_PASS_START_COL(pass);
3488 stepx = PNG_PASS_COL_OFFSET(pass);
3489 y = PNG_PASS_START_ROW(pass);
3490 stepy = PNG_PASS_ROW_OFFSET(pass);
3491 }
3492
3493 else
3494 {
3495 y = 0;
3496 startx = 0;
3497 stepx = stepy = 1;
3498 }
3499
3500 if (display->background == NULL)
3501 {
3502 for (; y<height; y += stepy)
3503 {
3504 png_bytep inrow = png_voidcast(png_bytep,
3505 display->local_row);
3506 png_bytep outrow = first_row + y * step_row;
3507 png_const_bytep end_row = outrow + width;
3508
3509 /* Read the row, which is packed: */
3510 png_read_row(png_ptr, inrow, NULL);
3511
3512 /* Now do the composition on each pixel in this row. */
3513 outrow += startx;
3514 for (; outrow < end_row; outrow += stepx)
3515 {
3516 png_byte alpha = inrow[1];
3517
3518 if (alpha > 0) /* else no change to the output */
3519 {
3520 png_uint_32 component = inrow[0];
3521
3522 if (alpha < 255) /* else just use component */
3523 {
3524 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3525 * necessary to invert the sRGB transfer
3526 * function and multiply the alpha out.
3527 */
3528 component = png_sRGB_table[component] * alpha;
3529 component += png_sRGB_table[outrow[0]] *
3530 (255-alpha);
3531 component = PNG_sRGB_FROM_LINEAR(component);
3532 }
3533
3534 outrow[0] = (png_byte)component;
3535 }
3536
3537 inrow += 2; /* gray and alpha channel */
3538 }
3539 }
3540 }
3541
3542 else /* constant background value */
3543 {
3544 png_byte background8 = display->background->green;
3545 png_uint_16 background = png_sRGB_table[background8];
3546
3547 for (; y<height; y += stepy)
3548 {
3549 png_bytep inrow = png_voidcast(png_bytep,
3550 display->local_row);
3551 png_bytep outrow = first_row + y * step_row;
3552 png_const_bytep end_row = outrow + width;
3553
3554 /* Read the row, which is packed: */
3555 png_read_row(png_ptr, inrow, NULL);
3556
3557 /* Now do the composition on each pixel in this row. */
3558 outrow += startx;
3559 for (; outrow < end_row; outrow += stepx)
3560 {
3561 png_byte alpha = inrow[1];
3562
3563 if (alpha > 0) /* else use background */
3564 {
3565 png_uint_32 component = inrow[0];
3566
3567 if (alpha < 255) /* else just use component */
3568 {
3569 component = png_sRGB_table[component] * alpha;
3570 component += background * (255-alpha);
3571 component = PNG_sRGB_FROM_LINEAR(component);
3572 }
3573
3574 outrow[0] = (png_byte)component;
3575 }
3576
3577 else
3578 outrow[0] = background8;
3579
3580 inrow += 2; /* gray and alpha channel */
3581 }
3582
3583 row += display->row_bytes;
3584 }
3585 }
3586 }
3587 }
3588 break;
3589
3590 case 16:
3591 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3592 * still be done and, maybe, the alpha channel removed. This code also
3593 * handles the alpha-first option.
3594 */
3595 {
3596 png_uint_16p first_row = png_voidcast(png_uint_16p,
3597 display->first_row);
3598 /* The division by two is safe because the caller passed in a
3599 * stride which was multiplied by 2 (below) to get row_bytes.
3600 */
3601 ptrdiff_t step_row = display->row_bytes / 2;
3602 unsigned int preserve_alpha = (image->format &
3603 PNG_FORMAT_FLAG_ALPHA) != 0;
3604 unsigned int outchannels = 1U+preserve_alpha;
3605 int swap_alpha = 0;
3606
3607 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3608 if (preserve_alpha != 0 &&
3609 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3610 swap_alpha = 1;
3611 # endif
3612
3613 for (pass = 0; pass < passes; ++pass)
3614 {
3615 unsigned int startx, stepx, stepy;
3616 png_uint_32 y;
3617
3618 /* The 'x' start and step are adjusted to output components here.
3619 */
3620 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3621 {
3622 /* The row may be empty for a short image: */
3623 if (PNG_PASS_COLS(width, pass) == 0)
3624 continue;
3625
3626 startx = PNG_PASS_START_COL(pass) * outchannels;
3627 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3628 y = PNG_PASS_START_ROW(pass);
3629 stepy = PNG_PASS_ROW_OFFSET(pass);
3630 }
3631
3632 else
3633 {
3634 y = 0;
3635 startx = 0;
3636 stepx = outchannels;
3637 stepy = 1;
3638 }
3639
3640 for (; y<height; y += stepy)
3641 {
3642 png_const_uint_16p inrow;
3643 png_uint_16p outrow = first_row + y*step_row;
3644 png_uint_16p end_row = outrow + width * outchannels;
3645
3646 /* Read the row, which is packed: */
3647 png_read_row(png_ptr, png_voidcast(png_bytep,
3648 display->local_row), NULL);
3649 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3650
3651 /* Now do the pre-multiplication on each pixel in this row.
3652 */
3653 outrow += startx;
3654 for (; outrow < end_row; outrow += stepx)
3655 {
3656 png_uint_32 component = inrow[0];
3657 png_uint_16 alpha = inrow[1];
3658
3659 if (alpha > 0) /* else 0 */
3660 {
3661 if (alpha < 65535) /* else just use component */
3662 {
3663 component *= alpha;
3664 component += 32767;
3665 component /= 65535;
3666 }
3667 }
3668
3669 else
3670 component = 0;
3671
3672 outrow[swap_alpha] = (png_uint_16)component;
3673 if (preserve_alpha != 0)
3674 outrow[1 ^ swap_alpha] = alpha;
3675
3676 inrow += 2; /* components and alpha channel */
3677 }
3678 }
3679 }
3680 }
3681 break;
3682
3683 #ifdef __GNUC__
3684 default:
3685 png_error(png_ptr, "unexpected bit depth");
3686 #endif
3687 }
3688
3689 return 1;
3690 }
3691
3692 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3693 static int
3694 png_image_read_direct(png_voidp argument)
3695 {
3696 png_image_read_control *display = png_voidcast(png_image_read_control*,
3697 argument);
3698 png_imagep image = display->image;
3699 png_structrp png_ptr = image->opaque->png_ptr;
3700 png_inforp info_ptr = image->opaque->info_ptr;
3701
3702 png_uint_32 format = image->format;
3703 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3704 int do_local_compose = 0;
3705 int do_local_background = 0; /* to avoid double gamma correction bug */
3706 int passes = 0;
3707
3708 /* Add transforms to ensure the correct output format is produced then check
3709 * that the required implementation support is there. Always expand; always
3710 * need 8 bits minimum, no palette and expanded tRNS.
3711 */
3712 png_set_expand(png_ptr);
3713
3714 /* Now check the format to see if it was modified. */
3715 {
3716 png_uint_32 base_format = png_image_format(png_ptr) &
3717 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3718 png_uint_32 change = format ^ base_format;
3719 png_fixed_point output_gamma;
3720 int mode; /* alpha mode */
3721
3722 /* Do this first so that we have a record if rgb to gray is happening. */
3723 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3724 {
3725 /* gray<->color transformation required. */
3726 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3727 png_set_gray_to_rgb(png_ptr);
3728
3729 else
3730 {
3731 /* libpng can't do both rgb to gray and
3732 * background/pre-multiplication if there is also significant gamma
3733 * correction, because both operations require linear colors and
3734 * the code only supports one transform doing the gamma correction.
3735 * Handle this by doing the pre-multiplication or background
3736 * operation in this code, if necessary.
3737 *
3738 * TODO: fix this by rewriting pngrtran.c (!)
3739 *
3740 * For the moment (given that fixing this in pngrtran.c is an
3741 * enormous change) 'do_local_background' is used to indicate that
3742 * the problem exists.
3743 */
3744 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3745 do_local_background = 1/*maybe*/;
3746
3747 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3748 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3749 }
3750
3751 change &= ~PNG_FORMAT_FLAG_COLOR;
3752 }
3753
3754 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3755 */
3756 {
3757 png_fixed_point input_gamma_default;
3758
3759 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3760 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3761 input_gamma_default = PNG_GAMMA_LINEAR;
3762 else
3763 input_gamma_default = PNG_DEFAULT_sRGB;
3764
3765 /* Call png_set_alpha_mode to set the default for the input gamma; the
3766 * output gamma is set by a second call below.
3767 */
3768 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3769 }
3770
3771 if (linear != 0)
3772 {
3773 /* If there *is* an alpha channel in the input it must be multiplied
3774 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3775 */
3776 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3777 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3778
3779 else
3780 mode = PNG_ALPHA_PNG;
3781
3782 output_gamma = PNG_GAMMA_LINEAR;
3783 }
3784
3785 else
3786 {
3787 mode = PNG_ALPHA_PNG;
3788 output_gamma = PNG_DEFAULT_sRGB;
3789 }
3790
3791 if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0)
3792 {
3793 mode = PNG_ALPHA_OPTIMIZED;
3794 change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
3795 }
3796
3797 /* If 'do_local_background' is set check for the presence of gamma
3798 * correction; this is part of the work-round for the libpng bug
3799 * described above.
3800 *
3801 * TODO: fix libpng and remove this.
3802 */
3803 if (do_local_background != 0)
3804 {
3805 png_fixed_point gtest;
3806
3807 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3808 * gamma correction, the screen gamma hasn't been set on png_struct
3809 * yet; it's set below. png_struct::gamma, however, is set to the
3810 * final value.
3811 */
3812 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3813 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3814 do_local_background = 0;
3815
3816 else if (mode == PNG_ALPHA_STANDARD)
3817 {
3818 do_local_background = 2/*required*/;
3819 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3820 }
3821
3822 /* else leave as 1 for the checks below */
3823 }
3824
3825 /* If the bit-depth changes then handle that here. */
3826 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3827 {
3828 if (linear != 0 /*16-bit output*/)
3829 png_set_expand_16(png_ptr);
3830
3831 else /* 8-bit output */
3832 png_set_scale_16(png_ptr);
3833
3834 change &= ~PNG_FORMAT_FLAG_LINEAR;
3835 }
3836
3837 /* Now the background/alpha channel changes. */
3838 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3839 {
3840 /* Removing an alpha channel requires composition for the 8-bit
3841 * formats; for the 16-bit it is already done, above, by the
3842 * pre-multiplication and the channel just needs to be stripped.
3843 */
3844 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3845 {
3846 /* If RGB->gray is happening the alpha channel must be left and the
3847 * operation completed locally.
3848 *
3849 * TODO: fix libpng and remove this.
3850 */
3851 if (do_local_background != 0)
3852 do_local_background = 2/*required*/;
3853
3854 /* 16-bit output: just remove the channel */
3855 else if (linear != 0) /* compose on black (well, pre-multiply) */
3856 png_set_strip_alpha(png_ptr);
3857
3858 /* 8-bit output: do an appropriate compose */
3859 else if (display->background != NULL)
3860 {
3861 png_color_16 c;
3862
3863 c.index = 0; /*unused*/
3864 c.red = display->background->red;
3865 c.green = display->background->green;
3866 c.blue = display->background->blue;
3867 c.gray = display->background->green;
3868
3869 /* This is always an 8-bit sRGB value, using the 'green' channel
3870 * for gray is much better than calculating the luminance here;
3871 * we can get off-by-one errors in that calculation relative to
3872 * the app expectations and that will show up in transparent
3873 * pixels.
3874 */
3875 png_set_background_fixed(png_ptr, &c,
3876 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3877 0/*gamma: not used*/);
3878 }
3879
3880 else /* compose on row: implemented below. */
3881 {
3882 do_local_compose = 1;
3883 /* This leaves the alpha channel in the output, so it has to be
3884 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3885 * one so the code only has to hack on the pixels that require
3886 * composition.
3887 */
3888 mode = PNG_ALPHA_OPTIMIZED;
3889 }
3890 }
3891
3892 else /* output needs an alpha channel */
3893 {
3894 /* This is tricky because it happens before the swap operation has
3895 * been accomplished; however, the swap does *not* swap the added
3896 * alpha channel (weird API), so it must be added in the correct
3897 * place.
3898 */
3899 png_uint_32 filler; /* opaque filler */
3900 int where;
3901
3902 if (linear != 0)
3903 filler = 65535;
3904
3905 else
3906 filler = 255;
3907
3908 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3909 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3910 {
3911 where = PNG_FILLER_BEFORE;
3912 change &= ~PNG_FORMAT_FLAG_AFIRST;
3913 }
3914
3915 else
3916 #endif
3917 where = PNG_FILLER_AFTER;
3918
3919 png_set_add_alpha(png_ptr, filler, where);
3920 }
3921
3922 /* This stops the (irrelevant) call to swap_alpha below. */
3923 change &= ~PNG_FORMAT_FLAG_ALPHA;
3924 }
3925
3926 /* Now set the alpha mode correctly; this is always done, even if there is
3927 * no alpha channel in either the input or the output because it correctly
3928 * sets the output gamma.
3929 */
3930 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3931
3932 # ifdef PNG_FORMAT_BGR_SUPPORTED
3933 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3934 {
3935 /* Check only the output format; PNG is never BGR; don't do this if
3936 * the output is gray, but fix up the 'format' value in that case.
3937 */
3938 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3939 png_set_bgr(png_ptr);
3940
3941 else
3942 format &= ~PNG_FORMAT_FLAG_BGR;
3943
3944 change &= ~PNG_FORMAT_FLAG_BGR;
3945 }
3946 # endif
3947
3948 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3949 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3950 {
3951 /* Only relevant if there is an alpha channel - it's particularly
3952 * important to handle this correctly because do_local_compose may
3953 * be set above and then libpng will keep the alpha channel for this
3954 * code to remove.
3955 */
3956 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3957 {
3958 /* Disable this if doing a local background,
3959 * TODO: remove this when local background is no longer required.
3960 */
3961 if (do_local_background != 2)
3962 png_set_swap_alpha(png_ptr);
3963 }
3964
3965 else
3966 format &= ~PNG_FORMAT_FLAG_AFIRST;
3967
3968 change &= ~PNG_FORMAT_FLAG_AFIRST;
3969 }
3970 # endif
3971
3972 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3973 * architecture.
3974 */
3975 if (linear != 0)
3976 {
3977 PNG_CONST png_uint_16 le = 0x0001;
3978
3979 if ((*(png_const_bytep) & le) != 0)
3980 png_set_swap(png_ptr);
3981 }
3982
3983 /* If change is not now 0 some transformation is missing - error out. */
3984 if (change != 0)
3985 png_error(png_ptr, "png_read_image: unsupported transformation");
3986 }
3987
3988 PNG_SKIP_CHUNKS(png_ptr);
3989
3990 /* Update the 'info' structure and make sure the result is as required; first
3991 * make sure to turn on the interlace handling if it will be required
3992 * (because it can't be turned on *after* the call to png_read_update_info!)
3993 *
3994 * TODO: remove the do_local_background fixup below.
3995 */
3996 if (do_local_compose == 0 && do_local_background != 2)
3997 passes = png_set_interlace_handling(png_ptr);
3998
3999 png_read_update_info(png_ptr, info_ptr);
4000
4001 {
4002 png_uint_32 info_format = 0;
4003
4004 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
4005 info_format |= PNG_FORMAT_FLAG_COLOR;
4006
4007 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
4008 {
4009 /* do_local_compose removes this channel below. */
4010 if (do_local_compose == 0)
4011 {
4012 /* do_local_background does the same if required. */
4013 if (do_local_background != 2 ||
4014 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
4015 info_format |= PNG_FORMAT_FLAG_ALPHA;
4016 }
4017 }
4018
4019 else if (do_local_compose != 0) /* internal error */
4020 png_error(png_ptr, "png_image_read: alpha channel lost");
4021
4022 if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) {
4023 info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
4024 }
4025
4026 if (info_ptr->bit_depth == 16)
4027 info_format |= PNG_FORMAT_FLAG_LINEAR;
4028
4029 #ifdef PNG_FORMAT_BGR_SUPPORTED
4030 if ((png_ptr->transformations & PNG_BGR) != 0)
4031 info_format |= PNG_FORMAT_FLAG_BGR;
4032 #endif
4033
4034 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
4035 if (do_local_background == 2)
4036 {
4037 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4038 info_format |= PNG_FORMAT_FLAG_AFIRST;
4039 }
4040
4041 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4042 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4043 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4044 {
4045 if (do_local_background == 2)
4046 png_error(png_ptr, "unexpected alpha swap transformation");
4047
4048 info_format |= PNG_FORMAT_FLAG_AFIRST;
4049 }
4050 # endif
4051
4052 /* This is actually an internal error. */
4053 if (info_format != format)
4054 png_error(png_ptr, "png_read_image: invalid transformations");
4055 }
4056
4057 /* Now read the rows. If do_local_compose is set then it is necessary to use
4058 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4059 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4060 * display acts as a flag.
4061 */
4062 {
4063 png_voidp first_row = display->buffer;
4064 ptrdiff_t row_bytes = display->row_stride;
4065
4066 if (linear != 0)
4067 row_bytes *= 2;
4068
4069 /* The following expression is designed to work correctly whether it gives
4070 * a signed or an unsigned result.
4071 */
4072 if (row_bytes < 0)
4073 {
4074 char *ptr = png_voidcast(char*, first_row);
4075 ptr += (image->height-1) * (-row_bytes);
4076 first_row = png_voidcast(png_voidp, ptr);
4077 }
4078
4079 display->first_row = first_row;
4080 display->row_bytes = row_bytes;
4081 }
4082
4083 if (do_local_compose != 0)
4084 {
4085 int result;
4086 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4087
4088 display->local_row = row;
4089 result = png_safe_execute(image, png_image_read_composite, display);
4090 display->local_row = NULL;
4091 png_free(png_ptr, row);
4092
4093 return result;
4094 }
4095
4096 else if (do_local_background == 2)
4097 {
4098 int result;
4099 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4100
4101 display->local_row = row;
4102 result = png_safe_execute(image, png_image_read_background, display);
4103 display->local_row = NULL;
4104 png_free(png_ptr, row);
4105
4106 return result;
4107 }
4108
4109 else
4110 {
4111 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
4112
4113 while (--passes >= 0)
4114 {
4115 png_uint_32 y = image->height;
4116 png_bytep row = png_voidcast(png_bytep, display->first_row);
4117
4118 for (; y > 0; --y)
4119 {
4120 png_read_row(png_ptr, row, NULL);
4121 row += row_bytes;
4122 }
4123 }
4124
4125 return 1;
4126 }
4127 }
4128
4129 int PNGAPI
4130 png_image_finish_read(png_imagep image, png_const_colorp background,
4131 void *buffer, png_int_32 row_stride, void *colormap)
4132 {
4133 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4134 {
4135 /* Check for row_stride overflow. This check is not performed on the
4136 * original PNG format because it may not occur in the output PNG format
4137 * and libpng deals with the issues of reading the original.
4138 */
4139 const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4140
4141 /* The following checks just the 'row_stride' calculation to ensure it
4142 * fits in a signed 32-bit value. Because channels/components can be
4143 * either 1 or 2 bytes in size the length of a row can still overflow 32
4144 * bits; this is just to verify that the 'row_stride' argument can be
4145 * represented.
4146 */
4147 if (image->width <= 0x7fffffffU/channels) /* no overflow */
4148 {
4149 png_uint_32 check;
4150 const png_uint_32 png_row_stride = image->width * channels;
4151
4152 if (row_stride == 0)
4153 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4154
4155 if (row_stride < 0)
4156 check = (png_uint_32)(-row_stride);
4157
4158 else
4159 check = (png_uint_32)row_stride;
4160
4161 /* This verifies 'check', the absolute value of the actual stride
4162 * passed in and detects overflow in the application calculation (i.e.
4163 * if the app did actually pass in a non-zero 'row_stride'.
4164 */
4165 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4166 {
4167 /* Now check for overflow of the image buffer calculation; this
4168 * limits the whole image size to 32 bits for API compatibility with
4169 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4170 *
4171 * The PNG_IMAGE_BUFFER_SIZE macro is:
4172 *
4173 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4174 *
4175 * And the component size is always 1 or 2, so make sure that the
4176 * number of *bytes* that the application is saying are available
4177 * does actually fit into a 32-bit number.
4178 *
4179 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4180 * will be changed to use png_alloc_size_t; bigger images can be
4181 * accommodated on 64-bit systems.
4182 */
4183 if (image->height <=
4184 0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
4185 {
4186 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4187 (image->colormap_entries > 0 && colormap != NULL))
4188 {
4189 int result;
4190 png_image_read_control display;
4191
4192 memset(&display, 0, (sizeof display));
4193 display.image = image;
4194 display.buffer = buffer;
4195 display.row_stride = row_stride;
4196 display.colormap = colormap;
4197 display.background = background;
4198 display.local_row = NULL;
4199
4200 /* Choose the correct 'end' routine; for the color-map case
4201 * all the setup has already been done.
4202 */
4203 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4204 result =
4205 png_safe_execute(image,
4206 png_image_read_colormap, &display) &&
4207 png_safe_execute(image,
4208 png_image_read_colormapped, &display);
4209
4210 else
4211 result =
4212 png_safe_execute(image,
4213 png_image_read_direct, &display);
4214
4215 png_image_free(image);
4216 return result;
4217 }
4218
4219 else
4220 return png_image_error(image,
4221 "png_image_finish_read[color-map]: no color-map");
4222 }
4223
4224 else
4225 return png_image_error(image,
4226 "png_image_finish_read: image too large");
4227 }
4228
4229 else
4230 return png_image_error(image,
4231 "png_image_finish_read: invalid argument");
4232 }
4233
4234 else
4235 return png_image_error(image,
4236 "png_image_finish_read: row_stride too large");
4237 }
4238
4239 else if (image != NULL)
4240 return png_image_error(image,
4241 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4242
4243 return 0;
4244 }
4245
4246 #endif /* SIMPLIFIED_READ */
4247 #endif /* READ */