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 * Copyright (c) 2018-2019 Cosmin Truta
33 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
34 * Copyright (c) 1996-1997 Andreas Dilger
35 * 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
png_read_info(png_structrp png_ptr,png_inforp info_ptr)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
png_read_update_info(png_structrp png_ptr,png_inforp info_ptr)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
png_start_read_image(png_structrp png_ptr)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
png_do_read_intrapixel(png_row_infop row_info,png_bytep row)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
png_read_row(png_structrp png_ptr,png_bytep row,png_bytep dsp_row)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
png_read_rows(png_structrp png_ptr,png_bytepp row,png_bytepp display_row,png_uint_32 num_rows)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
png_read_image(png_structrp png_ptr,png_bytepp image)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
png_read_end(png_structrp png_ptr,png_inforp info_ptr)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
png_read_destroy(png_structrp png_ptr)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 #if defined(PNG_READ_EXPAND_SUPPORTED) && \
1026 defined(PNG_ARM_NEON_IMPLEMENTATION)
1027 png_free(png_ptr, png_ptr->riffled_palette);
1028 png_ptr->riffled_palette = NULL;
1029 #endif
1030
1031 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1032 * callbacks are still set at this point. They are required to complete the
1033 * destruction of the png_struct itself.
1034 */
1035 }
1036
1037 /* Free all memory used by the read */
1038 void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr,png_infopp info_ptr_ptr,png_infopp end_info_ptr_ptr)1039 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1040 png_infopp end_info_ptr_ptr)
1041 {
1042 png_structrp png_ptr = NULL;
1043
1044 png_debug(1, "in png_destroy_read_struct");
1045
1046 if (png_ptr_ptr != NULL)
1047 png_ptr = *png_ptr_ptr;
1048
1049 if (png_ptr == NULL)
1050 return;
1051
1052 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1053 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1054 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1055 */
1056 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1057 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1058
1059 *png_ptr_ptr = NULL;
1060 png_read_destroy(png_ptr);
1061 png_destroy_png_struct(png_ptr);
1062 }
1063
1064 void PNGAPI
png_set_read_status_fn(png_structrp png_ptr,png_read_status_ptr read_row_fn)1065 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1066 {
1067 if (png_ptr == NULL)
1068 return;
1069
1070 png_ptr->read_row_fn = read_row_fn;
1071 }
1072
1073
1074 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1075 #ifdef PNG_INFO_IMAGE_SUPPORTED
1076 void PNGAPI
png_read_png(png_structrp png_ptr,png_inforp info_ptr,int transforms,voidp params)1077 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1078 int transforms, voidp params)
1079 {
1080 if (png_ptr == NULL || info_ptr == NULL)
1081 return;
1082
1083 /* png_read_info() gives us all of the information from the
1084 * PNG file before the first IDAT (image data chunk).
1085 */
1086 png_read_info(png_ptr, info_ptr);
1087 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1088 png_error(png_ptr, "Image is too high to process with png_read_png()");
1089
1090 /* -------------- image transformations start here ------------------- */
1091 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1092 * is not implemented. This will only happen in de-configured (non-default)
1093 * libpng builds. The results can be unexpected - png_read_png may return
1094 * short or mal-formed rows because the transform is skipped.
1095 */
1096
1097 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1098 */
1099 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1100 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1101 * did in earlier versions, while "scale_16" is now more accurate.
1102 */
1103 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1104 png_set_scale_16(png_ptr);
1105 #else
1106 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1107 #endif
1108
1109 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1110 * latter by doing SCALE first. This is ok and allows apps not to check for
1111 * which is supported to get the right answer.
1112 */
1113 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1114 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1115 png_set_strip_16(png_ptr);
1116 #else
1117 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1118 #endif
1119
1120 /* Strip alpha bytes from the input data without combining with
1121 * the background (not recommended).
1122 */
1123 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1124 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1125 png_set_strip_alpha(png_ptr);
1126 #else
1127 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1128 #endif
1129
1130 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1131 * byte into separate bytes (useful for paletted and grayscale images).
1132 */
1133 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1134 #ifdef PNG_READ_PACK_SUPPORTED
1135 png_set_packing(png_ptr);
1136 #else
1137 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1138 #endif
1139
1140 /* Change the order of packed pixels to least significant bit first
1141 * (not useful if you are using png_set_packing).
1142 */
1143 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1144 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1145 png_set_packswap(png_ptr);
1146 #else
1147 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1148 #endif
1149
1150 /* Expand paletted colors into true RGB triplets
1151 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1152 * Expand paletted or RGB images with transparency to full alpha
1153 * channels so the data will be available as RGBA quartets.
1154 */
1155 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1156 #ifdef PNG_READ_EXPAND_SUPPORTED
1157 png_set_expand(png_ptr);
1158 #else
1159 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1160 #endif
1161
1162 /* We don't handle background color or gamma transformation or quantizing.
1163 */
1164
1165 /* Invert monochrome files to have 0 as white and 1 as black
1166 */
1167 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1168 #ifdef PNG_READ_INVERT_SUPPORTED
1169 png_set_invert_mono(png_ptr);
1170 #else
1171 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1172 #endif
1173
1174 /* If you want to shift the pixel values from the range [0,255] or
1175 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1176 * colors were originally in:
1177 */
1178 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1179 #ifdef PNG_READ_SHIFT_SUPPORTED
1180 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1181 png_set_shift(png_ptr, &info_ptr->sig_bit);
1182 #else
1183 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1184 #endif
1185
1186 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1187 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1188 #ifdef PNG_READ_BGR_SUPPORTED
1189 png_set_bgr(png_ptr);
1190 #else
1191 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1192 #endif
1193
1194 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1195 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1196 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1197 png_set_swap_alpha(png_ptr);
1198 #else
1199 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1200 #endif
1201
1202 /* Swap bytes of 16-bit files to least significant byte first */
1203 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1204 #ifdef PNG_READ_SWAP_SUPPORTED
1205 png_set_swap(png_ptr);
1206 #else
1207 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1208 #endif
1209
1210 /* Added at libpng-1.2.41 */
1211 /* Invert the alpha channel from opacity to transparency */
1212 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1213 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1214 png_set_invert_alpha(png_ptr);
1215 #else
1216 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1217 #endif
1218
1219 /* Added at libpng-1.2.41 */
1220 /* Expand grayscale image to RGB */
1221 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1222 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1223 png_set_gray_to_rgb(png_ptr);
1224 #else
1225 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1226 #endif
1227
1228 /* Added at libpng-1.5.4 */
1229 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1230 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1231 png_set_expand_16(png_ptr);
1232 #else
1233 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1234 #endif
1235
1236 /* We don't handle adding filler bytes */
1237
1238 /* We use png_read_image and rely on that for interlace handling, but we also
1239 * call png_read_update_info therefore must turn on interlace handling now:
1240 */
1241 (void)png_set_interlace_handling(png_ptr);
1242
1243 /* Optional call to gamma correct and add the background to the palette
1244 * and update info structure. REQUIRED if you are expecting libpng to
1245 * update the palette for you (i.e., you selected such a transform above).
1246 */
1247 png_read_update_info(png_ptr, info_ptr);
1248
1249 /* -------------- image transformations end here ------------------- */
1250
1251 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1252 if (info_ptr->row_pointers == NULL)
1253 {
1254 png_uint_32 iptr;
1255
1256 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1257 info_ptr->height * (sizeof (png_bytep))));
1258
1259 for (iptr=0; iptr<info_ptr->height; iptr++)
1260 info_ptr->row_pointers[iptr] = NULL;
1261
1262 info_ptr->free_me |= PNG_FREE_ROWS;
1263
1264 for (iptr = 0; iptr < info_ptr->height; iptr++)
1265 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1266 png_malloc(png_ptr, info_ptr->rowbytes));
1267 }
1268
1269 png_read_image(png_ptr, info_ptr->row_pointers);
1270 info_ptr->valid |= PNG_INFO_IDAT;
1271
1272 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1273 png_read_end(png_ptr, info_ptr);
1274
1275 PNG_UNUSED(params)
1276 }
1277 #endif /* INFO_IMAGE */
1278 #endif /* SEQUENTIAL_READ */
1279
1280 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1281 /* SIMPLIFIED READ
1282 *
1283 * This code currently relies on the sequential reader, though it could easily
1284 * be made to work with the progressive one.
1285 */
1286 /* Arguments to png_image_finish_read: */
1287
1288 /* Encoding of PNG data (used by the color-map code) */
1289 # define P_NOTSET 0 /* File encoding not yet known */
1290 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1291 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1292 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1293 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1294
1295 /* Color-map processing: after libpng has run on the PNG image further
1296 * processing may be needed to convert the data to color-map indices.
1297 */
1298 #define PNG_CMAP_NONE 0
1299 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1300 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1301 #define PNG_CMAP_RGB 3 /* Process RGB data */
1302 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1303
1304 /* The following document where the background is for each processing case. */
1305 #define PNG_CMAP_NONE_BACKGROUND 256
1306 #define PNG_CMAP_GA_BACKGROUND 231
1307 #define PNG_CMAP_TRANS_BACKGROUND 254
1308 #define PNG_CMAP_RGB_BACKGROUND 256
1309 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1310
1311 typedef struct
1312 {
1313 /* Arguments: */
1314 png_imagep image;
1315 png_voidp buffer;
1316 png_int_32 row_stride;
1317 png_voidp colormap;
1318 png_const_colorp background;
1319 /* Local variables: */
1320 png_voidp local_row;
1321 png_voidp first_row;
1322 ptrdiff_t row_bytes; /* step between rows */
1323 int file_encoding; /* E_ values above */
1324 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1325 int colormap_processing; /* PNG_CMAP_ values above */
1326 } png_image_read_control;
1327
1328 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1329 * called, so setting up the jmp_buf is not required. This means that anything
1330 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1331 * instead so that control is returned safely back to this routine.
1332 */
1333 static int
png_image_read_init(png_imagep image)1334 png_image_read_init(png_imagep image)
1335 {
1336 if (image->opaque == NULL)
1337 {
1338 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1339 png_safe_error, png_safe_warning);
1340
1341 /* And set the rest of the structure to NULL to ensure that the various
1342 * fields are consistent.
1343 */
1344 memset(image, 0, (sizeof *image));
1345 image->version = PNG_IMAGE_VERSION;
1346
1347 if (png_ptr != NULL)
1348 {
1349 png_infop info_ptr = png_create_info_struct(png_ptr);
1350
1351 if (info_ptr != NULL)
1352 {
1353 png_controlp control = png_voidcast(png_controlp,
1354 png_malloc_warn(png_ptr, (sizeof *control)));
1355
1356 if (control != NULL)
1357 {
1358 memset(control, 0, (sizeof *control));
1359
1360 control->png_ptr = png_ptr;
1361 control->info_ptr = info_ptr;
1362 control->for_write = 0;
1363
1364 image->opaque = control;
1365 return 1;
1366 }
1367
1368 /* Error clean up */
1369 png_destroy_info_struct(png_ptr, &info_ptr);
1370 }
1371
1372 png_destroy_read_struct(&png_ptr, NULL, NULL);
1373 }
1374
1375 return png_image_error(image, "png_image_read: out of memory");
1376 }
1377
1378 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1379 }
1380
1381 /* Utility to find the base format of a PNG file from a png_struct. */
1382 static png_uint_32
png_image_format(png_structrp png_ptr)1383 png_image_format(png_structrp png_ptr)
1384 {
1385 png_uint_32 format = 0;
1386
1387 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1388 format |= PNG_FORMAT_FLAG_COLOR;
1389
1390 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1391 format |= PNG_FORMAT_FLAG_ALPHA;
1392
1393 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1394 * sets the png_struct fields; that's all we are interested in here. The
1395 * precise interaction with an app call to png_set_tRNS and PNG file reading
1396 * is unclear.
1397 */
1398 else if (png_ptr->num_trans > 0)
1399 format |= PNG_FORMAT_FLAG_ALPHA;
1400
1401 if (png_ptr->bit_depth == 16)
1402 format |= PNG_FORMAT_FLAG_LINEAR;
1403
1404 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1405 format |= PNG_FORMAT_FLAG_COLORMAP;
1406
1407 return format;
1408 }
1409
1410 /* Is the given gamma significantly different from sRGB? The test is the same
1411 * one used in pngrtran.c when deciding whether to do gamma correction. The
1412 * arithmetic optimizes the division by using the fact that the inverse of the
1413 * file sRGB gamma is 2.2
1414 */
1415 static int
png_gamma_not_sRGB(png_fixed_point g)1416 png_gamma_not_sRGB(png_fixed_point g)
1417 {
1418 if (g < PNG_FP_1)
1419 {
1420 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1421 if (g == 0)
1422 return 0;
1423
1424 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1425 }
1426
1427 return 1;
1428 }
1429
1430 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1431 * header and fill in all the information. This is executed in a safe context,
1432 * unlike the init routine above.
1433 */
1434 static int
png_image_read_header(png_voidp argument)1435 png_image_read_header(png_voidp argument)
1436 {
1437 png_imagep image = png_voidcast(png_imagep, argument);
1438 png_structrp png_ptr = image->opaque->png_ptr;
1439 png_inforp info_ptr = image->opaque->info_ptr;
1440
1441 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
1442 png_set_benign_errors(png_ptr, 1/*warn*/);
1443 #endif
1444 png_read_info(png_ptr, info_ptr);
1445
1446 /* Do this the fast way; just read directly out of png_struct. */
1447 image->width = png_ptr->width;
1448 image->height = png_ptr->height;
1449
1450 {
1451 png_uint_32 format = png_image_format(png_ptr);
1452
1453 image->format = format;
1454
1455 #ifdef PNG_COLORSPACE_SUPPORTED
1456 /* Does the colorspace match sRGB? If there is no color endpoint
1457 * (colorant) information assume yes, otherwise require the
1458 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1459 * colorspace has been determined to be invalid ignore it.
1460 */
1461 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1462 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1463 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1464 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1465 #endif
1466 }
1467
1468 /* We need the maximum number of entries regardless of the format the
1469 * application sets here.
1470 */
1471 {
1472 png_uint_32 cmap_entries;
1473
1474 switch (png_ptr->color_type)
1475 {
1476 case PNG_COLOR_TYPE_GRAY:
1477 cmap_entries = 1U << png_ptr->bit_depth;
1478 break;
1479
1480 case PNG_COLOR_TYPE_PALETTE:
1481 cmap_entries = (png_uint_32)png_ptr->num_palette;
1482 break;
1483
1484 default:
1485 cmap_entries = 256;
1486 break;
1487 }
1488
1489 if (cmap_entries > 256)
1490 cmap_entries = 256;
1491
1492 image->colormap_entries = cmap_entries;
1493 }
1494
1495 return 1;
1496 }
1497
1498 #ifdef PNG_STDIO_SUPPORTED
1499 int PNGAPI
png_image_begin_read_from_stdio(png_imagep image,FILE * file)1500 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1501 {
1502 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1503 {
1504 if (file != NULL)
1505 {
1506 if (png_image_read_init(image) != 0)
1507 {
1508 /* This is slightly evil, but png_init_io doesn't do anything other
1509 * than this and we haven't changed the standard IO functions so
1510 * this saves a 'safe' function.
1511 */
1512 image->opaque->png_ptr->io_ptr = file;
1513 return png_safe_execute(image, png_image_read_header, image);
1514 }
1515 }
1516
1517 else
1518 return png_image_error(image,
1519 "png_image_begin_read_from_stdio: invalid argument");
1520 }
1521
1522 else if (image != NULL)
1523 return png_image_error(image,
1524 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1525
1526 return 0;
1527 }
1528
1529 int PNGAPI
png_image_begin_read_from_file(png_imagep image,const char * file_name)1530 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1531 {
1532 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1533 {
1534 if (file_name != NULL)
1535 {
1536 FILE *fp = fopen(file_name, "rb");
1537
1538 if (fp != NULL)
1539 {
1540 if (png_image_read_init(image) != 0)
1541 {
1542 image->opaque->png_ptr->io_ptr = fp;
1543 image->opaque->owned_file = 1;
1544 return png_safe_execute(image, png_image_read_header, image);
1545 }
1546
1547 /* Clean up: just the opened file. */
1548 (void)fclose(fp);
1549 }
1550
1551 else
1552 return png_image_error(image, strerror(errno));
1553 }
1554
1555 else
1556 return png_image_error(image,
1557 "png_image_begin_read_from_file: invalid argument");
1558 }
1559
1560 else if (image != NULL)
1561 return png_image_error(image,
1562 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1563
1564 return 0;
1565 }
1566 #endif /* STDIO */
1567
1568 static void PNGCBAPI
png_image_memory_read(png_structp png_ptr,png_bytep out,size_t need)1569 png_image_memory_read(png_structp png_ptr, png_bytep out, size_t need)
1570 {
1571 if (png_ptr != NULL)
1572 {
1573 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1574 if (image != NULL)
1575 {
1576 png_controlp cp = image->opaque;
1577 if (cp != NULL)
1578 {
1579 png_const_bytep memory = cp->memory;
1580 size_t size = cp->size;
1581
1582 if (memory != NULL && size >= need)
1583 {
1584 memcpy(out, memory, need);
1585 cp->memory = memory + need;
1586 cp->size = size - need;
1587 return;
1588 }
1589
1590 png_error(png_ptr, "read beyond end of data");
1591 }
1592 }
1593
1594 png_error(png_ptr, "invalid memory read");
1595 }
1596 }
1597
png_image_begin_read_from_memory(png_imagep image,png_const_voidp memory,size_t size)1598 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1599 png_const_voidp memory, size_t size)
1600 {
1601 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1602 {
1603 if (memory != NULL && size > 0)
1604 {
1605 if (png_image_read_init(image) != 0)
1606 {
1607 /* Now set the IO functions to read from the memory buffer and
1608 * store it into io_ptr. Again do this in-place to avoid calling a
1609 * libpng function that requires error handling.
1610 */
1611 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1612 image->opaque->size = size;
1613 image->opaque->png_ptr->io_ptr = image;
1614 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1615
1616 return png_safe_execute(image, png_image_read_header, image);
1617 }
1618 }
1619
1620 else
1621 return png_image_error(image,
1622 "png_image_begin_read_from_memory: invalid argument");
1623 }
1624
1625 else if (image != NULL)
1626 return png_image_error(image,
1627 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1628
1629 return 0;
1630 }
1631
1632 /* Utility function to skip chunks that are not used by the simplified image
1633 * read functions and an appropriate macro to call it.
1634 */
1635 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1636 static void
png_image_skip_unused_chunks(png_structrp png_ptr)1637 png_image_skip_unused_chunks(png_structrp png_ptr)
1638 {
1639 /* Prepare the reader to ignore all recognized chunks whose data will not
1640 * be used, i.e., all chunks recognized by libpng except for those
1641 * involved in basic image reading:
1642 *
1643 * IHDR, PLTE, IDAT, IEND
1644 *
1645 * Or image data handling:
1646 *
1647 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1648 *
1649 * This provides a small performance improvement and eliminates any
1650 * potential vulnerability to security problems in the unused chunks.
1651 *
1652 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1653 * too. This allows the simplified API to be compiled without iCCP support,
1654 * however if the support is there the chunk is still checked to detect
1655 * errors (which are unfortunately quite common.)
1656 */
1657 {
1658 static const png_byte chunks_to_process[] = {
1659 98, 75, 71, 68, '\0', /* bKGD */
1660 99, 72, 82, 77, '\0', /* cHRM */
1661 103, 65, 77, 65, '\0', /* gAMA */
1662 # ifdef PNG_READ_iCCP_SUPPORTED
1663 105, 67, 67, 80, '\0', /* iCCP */
1664 # endif
1665 115, 66, 73, 84, '\0', /* sBIT */
1666 115, 82, 71, 66, '\0', /* sRGB */
1667 };
1668
1669 /* Ignore unknown chunks and all other chunks except for the
1670 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1671 */
1672 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1673 NULL, -1);
1674
1675 /* But do not ignore image data handling chunks */
1676 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1677 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1678 }
1679 }
1680
1681 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1682 #else
1683 # define PNG_SKIP_CHUNKS(p) ((void)0)
1684 #endif /* HANDLE_AS_UNKNOWN */
1685
1686 /* The following macro gives the exact rounded answer for all values in the
1687 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1688 * the correct numbers 0..5
1689 */
1690 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1691
1692 /* Utility functions to make particular color-maps */
1693 static void
set_file_encoding(png_image_read_control * display)1694 set_file_encoding(png_image_read_control *display)
1695 {
1696 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1697 if (png_gamma_significant(g) != 0)
1698 {
1699 if (png_gamma_not_sRGB(g) != 0)
1700 {
1701 display->file_encoding = P_FILE;
1702 display->gamma_to_linear = png_reciprocal(g);
1703 }
1704
1705 else
1706 display->file_encoding = P_sRGB;
1707 }
1708
1709 else
1710 display->file_encoding = P_LINEAR8;
1711 }
1712
1713 static unsigned int
decode_gamma(png_image_read_control * display,png_uint_32 value,int encoding)1714 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1715 {
1716 if (encoding == P_FILE) /* double check */
1717 encoding = display->file_encoding;
1718
1719 if (encoding == P_NOTSET) /* must be the file encoding */
1720 {
1721 set_file_encoding(display);
1722 encoding = display->file_encoding;
1723 }
1724
1725 switch (encoding)
1726 {
1727 case P_FILE:
1728 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1729 break;
1730
1731 case P_sRGB:
1732 value = png_sRGB_table[value];
1733 break;
1734
1735 case P_LINEAR:
1736 break;
1737
1738 case P_LINEAR8:
1739 value *= 257;
1740 break;
1741
1742 #ifdef __GNUC__
1743 default:
1744 png_error(display->image->opaque->png_ptr,
1745 "unexpected encoding (internal error)");
1746 #endif
1747 }
1748
1749 return value;
1750 }
1751
1752 static png_uint_32
png_colormap_compose(png_image_read_control * display,png_uint_32 foreground,int foreground_encoding,png_uint_32 alpha,png_uint_32 background,int encoding)1753 png_colormap_compose(png_image_read_control *display,
1754 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1755 png_uint_32 background, int encoding)
1756 {
1757 /* The file value is composed on the background, the background has the given
1758 * encoding and so does the result, the file is encoded with P_FILE and the
1759 * file and alpha are 8-bit values. The (output) encoding will always be
1760 * P_LINEAR or P_sRGB.
1761 */
1762 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1763 png_uint_32 b = decode_gamma(display, background, encoding);
1764
1765 /* The alpha is always an 8-bit value (it comes from the palette), the value
1766 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1767 */
1768 f = f * alpha + b * (255-alpha);
1769
1770 if (encoding == P_LINEAR)
1771 {
1772 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1773 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1774 */
1775 f *= 257; /* Now scaled by 65535 */
1776 f += f >> 16;
1777 f = (f+32768) >> 16;
1778 }
1779
1780 else /* P_sRGB */
1781 f = PNG_sRGB_FROM_LINEAR(f);
1782
1783 return f;
1784 }
1785
1786 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1787 * be 8-bit.
1788 */
1789 static void
png_create_colormap_entry(png_image_read_control * display,png_uint_32 ip,png_uint_32 red,png_uint_32 green,png_uint_32 blue,png_uint_32 alpha,int encoding)1790 png_create_colormap_entry(png_image_read_control *display,
1791 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1792 png_uint_32 alpha, int encoding)
1793 {
1794 png_imagep image = display->image;
1795 int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1796 P_LINEAR : P_sRGB;
1797 int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1798 (red != green || green != blue);
1799
1800 if (ip > 255)
1801 png_error(image->opaque->png_ptr, "color-map index out of range");
1802
1803 /* Update the cache with whether the file gamma is significantly different
1804 * from sRGB.
1805 */
1806 if (encoding == P_FILE)
1807 {
1808 if (display->file_encoding == P_NOTSET)
1809 set_file_encoding(display);
1810
1811 /* Note that the cached value may be P_FILE too, but if it is then the
1812 * gamma_to_linear member has been set.
1813 */
1814 encoding = display->file_encoding;
1815 }
1816
1817 if (encoding == P_FILE)
1818 {
1819 png_fixed_point g = display->gamma_to_linear;
1820
1821 red = png_gamma_16bit_correct(red*257, g);
1822 green = png_gamma_16bit_correct(green*257, g);
1823 blue = png_gamma_16bit_correct(blue*257, g);
1824
1825 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1826 {
1827 alpha *= 257;
1828 encoding = P_LINEAR;
1829 }
1830
1831 else
1832 {
1833 red = PNG_sRGB_FROM_LINEAR(red * 255);
1834 green = PNG_sRGB_FROM_LINEAR(green * 255);
1835 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1836 encoding = P_sRGB;
1837 }
1838 }
1839
1840 else if (encoding == P_LINEAR8)
1841 {
1842 /* This encoding occurs quite frequently in test cases because PngSuite
1843 * includes a gAMA 1.0 chunk with most images.
1844 */
1845 red *= 257;
1846 green *= 257;
1847 blue *= 257;
1848 alpha *= 257;
1849 encoding = P_LINEAR;
1850 }
1851
1852 else if (encoding == P_sRGB &&
1853 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1854 {
1855 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1856 * linear.
1857 */
1858 red = png_sRGB_table[red];
1859 green = png_sRGB_table[green];
1860 blue = png_sRGB_table[blue];
1861 alpha *= 257;
1862 encoding = P_LINEAR;
1863 }
1864
1865 /* This is set if the color isn't gray but the output is. */
1866 if (encoding == P_LINEAR)
1867 {
1868 if (convert_to_Y != 0)
1869 {
1870 /* NOTE: these values are copied from png_do_rgb_to_gray */
1871 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1872 (png_uint_32)2366 * blue;
1873
1874 if (output_encoding == P_LINEAR)
1875 y = (y + 16384) >> 15;
1876
1877 else
1878 {
1879 /* y is scaled by 32768, we need it scaled by 255: */
1880 y = (y + 128) >> 8;
1881 y *= 255;
1882 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1883 alpha = PNG_DIV257(alpha);
1884 encoding = P_sRGB;
1885 }
1886
1887 blue = red = green = y;
1888 }
1889
1890 else if (output_encoding == P_sRGB)
1891 {
1892 red = PNG_sRGB_FROM_LINEAR(red * 255);
1893 green = PNG_sRGB_FROM_LINEAR(green * 255);
1894 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1895 alpha = PNG_DIV257(alpha);
1896 encoding = P_sRGB;
1897 }
1898 }
1899
1900 if (encoding != output_encoding)
1901 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1902
1903 /* Store the value. */
1904 {
1905 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1906 int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1907 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1908 # else
1909 # define afirst 0
1910 # endif
1911 # ifdef PNG_FORMAT_BGR_SUPPORTED
1912 int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1913 # else
1914 # define bgr 0
1915 # endif
1916
1917 if (output_encoding == P_LINEAR)
1918 {
1919 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1920
1921 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1922
1923 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1924 * value, if less than 65535 (this is, effectively, composite on black
1925 * if the alpha channel is removed.)
1926 */
1927 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1928 {
1929 case 4:
1930 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1931 /* FALLTHROUGH */
1932
1933 case 3:
1934 if (alpha < 65535)
1935 {
1936 if (alpha > 0)
1937 {
1938 blue = (blue * alpha + 32767U)/65535U;
1939 green = (green * alpha + 32767U)/65535U;
1940 red = (red * alpha + 32767U)/65535U;
1941 }
1942
1943 else
1944 red = green = blue = 0;
1945 }
1946 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1947 entry[afirst + 1] = (png_uint_16)green;
1948 entry[afirst + bgr] = (png_uint_16)red;
1949 break;
1950
1951 case 2:
1952 entry[1 ^ afirst] = (png_uint_16)alpha;
1953 /* FALLTHROUGH */
1954
1955 case 1:
1956 if (alpha < 65535)
1957 {
1958 if (alpha > 0)
1959 green = (green * alpha + 32767U)/65535U;
1960
1961 else
1962 green = 0;
1963 }
1964 entry[afirst] = (png_uint_16)green;
1965 break;
1966
1967 default:
1968 break;
1969 }
1970 }
1971
1972 else /* output encoding is P_sRGB */
1973 {
1974 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1975
1976 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1977
1978 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1979 {
1980 case 4:
1981 entry[afirst ? 0 : 3] = (png_byte)alpha;
1982 /* FALLTHROUGH */
1983 case 3:
1984 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1985 entry[afirst + 1] = (png_byte)green;
1986 entry[afirst + bgr] = (png_byte)red;
1987 break;
1988
1989 case 2:
1990 entry[1 ^ afirst] = (png_byte)alpha;
1991 /* FALLTHROUGH */
1992 case 1:
1993 entry[afirst] = (png_byte)green;
1994 break;
1995
1996 default:
1997 break;
1998 }
1999 }
2000
2001 # ifdef afirst
2002 # undef afirst
2003 # endif
2004 # ifdef bgr
2005 # undef bgr
2006 # endif
2007 }
2008 }
2009
2010 static int
make_gray_file_colormap(png_image_read_control * display)2011 make_gray_file_colormap(png_image_read_control *display)
2012 {
2013 unsigned int i;
2014
2015 for (i=0; i<256; ++i)
2016 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
2017
2018 return (int)i;
2019 }
2020
2021 static int
make_gray_colormap(png_image_read_control * display)2022 make_gray_colormap(png_image_read_control *display)
2023 {
2024 unsigned int i;
2025
2026 for (i=0; i<256; ++i)
2027 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
2028
2029 return (int)i;
2030 }
2031 #define PNG_GRAY_COLORMAP_ENTRIES 256
2032
2033 static int
make_ga_colormap(png_image_read_control * display)2034 make_ga_colormap(png_image_read_control *display)
2035 {
2036 unsigned int i, a;
2037
2038 /* Alpha is retained, the output will be a color-map with entries
2039 * selected by six levels of alpha. One transparent entry, 6 gray
2040 * levels for all the intermediate alpha values, leaving 230 entries
2041 * for the opaque grays. The color-map entries are the six values
2042 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2043 * relevant entry.
2044 *
2045 * if (alpha > 229) // opaque
2046 * {
2047 * // The 231 entries are selected to make the math below work:
2048 * base = 0;
2049 * entry = (231 * gray + 128) >> 8;
2050 * }
2051 * else if (alpha < 26) // transparent
2052 * {
2053 * base = 231;
2054 * entry = 0;
2055 * }
2056 * else // partially opaque
2057 * {
2058 * base = 226 + 6 * PNG_DIV51(alpha);
2059 * entry = PNG_DIV51(gray);
2060 * }
2061 */
2062 i = 0;
2063 while (i < 231)
2064 {
2065 unsigned int gray = (i * 256 + 115) / 231;
2066 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2067 }
2068
2069 /* 255 is used here for the component values for consistency with the code
2070 * that undoes premultiplication in pngwrite.c.
2071 */
2072 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2073
2074 for (a=1; a<5; ++a)
2075 {
2076 unsigned int g;
2077
2078 for (g=0; g<6; ++g)
2079 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2080 P_sRGB);
2081 }
2082
2083 return (int)i;
2084 }
2085
2086 #define PNG_GA_COLORMAP_ENTRIES 256
2087
2088 static int
make_rgb_colormap(png_image_read_control * display)2089 make_rgb_colormap(png_image_read_control *display)
2090 {
2091 unsigned int i, r;
2092
2093 /* Build a 6x6x6 opaque RGB cube */
2094 for (i=r=0; r<6; ++r)
2095 {
2096 unsigned int g;
2097
2098 for (g=0; g<6; ++g)
2099 {
2100 unsigned int b;
2101
2102 for (b=0; b<6; ++b)
2103 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2104 P_sRGB);
2105 }
2106 }
2107
2108 return (int)i;
2109 }
2110
2111 #define PNG_RGB_COLORMAP_ENTRIES 216
2112
2113 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2114 #define PNG_RGB_INDEX(r,g,b) \
2115 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2116
2117 static int
png_image_read_colormap(png_voidp argument)2118 png_image_read_colormap(png_voidp argument)
2119 {
2120 png_image_read_control *display =
2121 png_voidcast(png_image_read_control*, argument);
2122 png_imagep image = display->image;
2123
2124 png_structrp png_ptr = image->opaque->png_ptr;
2125 png_uint_32 output_format = image->format;
2126 int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2127 P_LINEAR : P_sRGB;
2128
2129 unsigned int cmap_entries;
2130 unsigned int output_processing; /* Output processing option */
2131 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2132
2133 /* Background information; the background color and the index of this color
2134 * in the color-map if it exists (else 256).
2135 */
2136 unsigned int background_index = 256;
2137 png_uint_32 back_r, back_g, back_b;
2138
2139 /* Flags to accumulate things that need to be done to the input. */
2140 int expand_tRNS = 0;
2141
2142 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2143 * very difficult to do, the results look awful, and it is difficult to see
2144 * what possible use it is because the application can't control the
2145 * color-map.
2146 */
2147 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2148 png_ptr->num_trans > 0) /* alpha in input */ &&
2149 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2150 {
2151 if (output_encoding == P_LINEAR) /* compose on black */
2152 back_b = back_g = back_r = 0;
2153
2154 else if (display->background == NULL /* no way to remove it */)
2155 png_error(png_ptr,
2156 "background color must be supplied to remove alpha/transparency");
2157
2158 /* Get a copy of the background color (this avoids repeating the checks
2159 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2160 * output format.
2161 */
2162 else
2163 {
2164 back_g = display->background->green;
2165 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2166 {
2167 back_r = display->background->red;
2168 back_b = display->background->blue;
2169 }
2170 else
2171 back_b = back_r = back_g;
2172 }
2173 }
2174
2175 else if (output_encoding == P_LINEAR)
2176 back_b = back_r = back_g = 65535;
2177
2178 else
2179 back_b = back_r = back_g = 255;
2180
2181 /* Default the input file gamma if required - this is necessary because
2182 * libpng assumes that if no gamma information is present the data is in the
2183 * output format, but the simplified API deduces the gamma from the input
2184 * format.
2185 */
2186 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2187 {
2188 /* Do this directly, not using the png_colorspace functions, to ensure
2189 * that it happens even if the colorspace is invalid (though probably if
2190 * it is the setting will be ignored) Note that the same thing can be
2191 * achieved at the application interface with png_set_gAMA.
2192 */
2193 if (png_ptr->bit_depth == 16 &&
2194 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2195 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2196
2197 else
2198 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2199
2200 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2201 }
2202
2203 /* Decide what to do based on the PNG color type of the input data. The
2204 * utility function png_create_colormap_entry deals with most aspects of the
2205 * output transformations; this code works out how to produce bytes of
2206 * color-map entries from the original format.
2207 */
2208 switch (png_ptr->color_type)
2209 {
2210 case PNG_COLOR_TYPE_GRAY:
2211 if (png_ptr->bit_depth <= 8)
2212 {
2213 /* There at most 256 colors in the output, regardless of
2214 * transparency.
2215 */
2216 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2217
2218 cmap_entries = 1U << png_ptr->bit_depth;
2219 if (cmap_entries > image->colormap_entries)
2220 png_error(png_ptr, "gray[8] color-map: too few entries");
2221
2222 step = 255 / (cmap_entries - 1);
2223 output_processing = PNG_CMAP_NONE;
2224
2225 /* If there is a tRNS chunk then this either selects a transparent
2226 * value or, if the output has no alpha, the background color.
2227 */
2228 if (png_ptr->num_trans > 0)
2229 {
2230 trans = png_ptr->trans_color.gray;
2231
2232 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2233 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2234 }
2235
2236 /* png_create_colormap_entry just takes an RGBA and writes the
2237 * corresponding color-map entry using the format from 'image',
2238 * including the required conversion to sRGB or linear as
2239 * appropriate. The input values are always either sRGB (if the
2240 * gamma correction flag is 0) or 0..255 scaled file encoded values
2241 * (if the function must gamma correct them).
2242 */
2243 for (i=val=0; i<cmap_entries; ++i, val += step)
2244 {
2245 /* 'i' is a file value. While this will result in duplicated
2246 * entries for 8-bit non-sRGB encoded files it is necessary to
2247 * have non-gamma corrected values to do tRNS handling.
2248 */
2249 if (i != trans)
2250 png_create_colormap_entry(display, i, val, val, val, 255,
2251 P_FILE/*8-bit with file gamma*/);
2252
2253 /* Else this entry is transparent. The colors don't matter if
2254 * there is an alpha channel (back_alpha == 0), but it does no
2255 * harm to pass them in; the values are not set above so this
2256 * passes in white.
2257 *
2258 * NOTE: this preserves the full precision of the application
2259 * supplied background color when it is used.
2260 */
2261 else
2262 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2263 back_alpha, output_encoding);
2264 }
2265
2266 /* We need libpng to preserve the original encoding. */
2267 data_encoding = P_FILE;
2268
2269 /* The rows from libpng, while technically gray values, are now also
2270 * color-map indices; however, they may need to be expanded to 1
2271 * byte per pixel. This is what png_set_packing does (i.e., it
2272 * unpacks the bit values into bytes.)
2273 */
2274 if (png_ptr->bit_depth < 8)
2275 png_set_packing(png_ptr);
2276 }
2277
2278 else /* bit depth is 16 */
2279 {
2280 /* The 16-bit input values can be converted directly to 8-bit gamma
2281 * encoded values; however, if a tRNS chunk is present 257 color-map
2282 * entries are required. This means that the extra entry requires
2283 * special processing; add an alpha channel, sacrifice gray level
2284 * 254 and convert transparent (alpha==0) entries to that.
2285 *
2286 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2287 * same time to minimize quality loss. If a tRNS chunk is present
2288 * this means libpng must handle it too; otherwise it is impossible
2289 * to do the exact match on the 16-bit value.
2290 *
2291 * If the output has no alpha channel *and* the background color is
2292 * gray then it is possible to let libpng handle the substitution by
2293 * ensuring that the corresponding gray level matches the background
2294 * color exactly.
2295 */
2296 data_encoding = P_sRGB;
2297
2298 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2299 png_error(png_ptr, "gray[16] color-map: too few entries");
2300
2301 cmap_entries = (unsigned int)make_gray_colormap(display);
2302
2303 if (png_ptr->num_trans > 0)
2304 {
2305 unsigned int back_alpha;
2306
2307 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2308 back_alpha = 0;
2309
2310 else
2311 {
2312 if (back_r == back_g && back_g == back_b)
2313 {
2314 /* Background is gray; no special processing will be
2315 * required.
2316 */
2317 png_color_16 c;
2318 png_uint_32 gray = back_g;
2319
2320 if (output_encoding == P_LINEAR)
2321 {
2322 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2323
2324 /* And make sure the corresponding palette entry
2325 * matches.
2326 */
2327 png_create_colormap_entry(display, gray, back_g, back_g,
2328 back_g, 65535, P_LINEAR);
2329 }
2330
2331 /* The background passed to libpng, however, must be the
2332 * sRGB value.
2333 */
2334 c.index = 0; /*unused*/
2335 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2336
2337 /* NOTE: does this work without expanding tRNS to alpha?
2338 * It should be the color->gray case below apparently
2339 * doesn't.
2340 */
2341 png_set_background_fixed(png_ptr, &c,
2342 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2343 0/*gamma: not used*/);
2344
2345 output_processing = PNG_CMAP_NONE;
2346 break;
2347 }
2348 #ifdef __COVERITY__
2349 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2350 * here.
2351 */
2352 back_alpha = 255;
2353 #else
2354 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2355 #endif
2356 }
2357
2358 /* output_processing means that the libpng-processed row will be
2359 * 8-bit GA and it has to be processing to single byte color-map
2360 * values. Entry 254 is replaced by either a completely
2361 * transparent entry or by the background color at full
2362 * precision (and the background color is not a simple gray
2363 * level in this case.)
2364 */
2365 expand_tRNS = 1;
2366 output_processing = PNG_CMAP_TRANS;
2367 background_index = 254;
2368
2369 /* And set (overwrite) color-map entry 254 to the actual
2370 * background color at full precision.
2371 */
2372 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2373 back_alpha, output_encoding);
2374 }
2375
2376 else
2377 output_processing = PNG_CMAP_NONE;
2378 }
2379 break;
2380
2381 case PNG_COLOR_TYPE_GRAY_ALPHA:
2382 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2383 * of 65536 combinations. If, however, the alpha channel is to be
2384 * removed there are only 256 possibilities if the background is gray.
2385 * (Otherwise there is a subset of the 65536 possibilities defined by
2386 * the triangle between black, white and the background color.)
2387 *
2388 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2389 * worry about tRNS matching - tRNS is ignored if there is an alpha
2390 * channel.
2391 */
2392 data_encoding = P_sRGB;
2393
2394 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2395 {
2396 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2397 png_error(png_ptr, "gray+alpha color-map: too few entries");
2398
2399 cmap_entries = (unsigned int)make_ga_colormap(display);
2400
2401 background_index = PNG_CMAP_GA_BACKGROUND;
2402 output_processing = PNG_CMAP_GA;
2403 }
2404
2405 else /* alpha is removed */
2406 {
2407 /* Alpha must be removed as the PNG data is processed when the
2408 * background is a color because the G and A channels are
2409 * independent and the vector addition (non-parallel vectors) is a
2410 * 2-D problem.
2411 *
2412 * This can be reduced to the same algorithm as above by making a
2413 * colormap containing gray levels (for the opaque grays), a
2414 * background entry (for a transparent pixel) and a set of four six
2415 * level color values, one set for each intermediate alpha value.
2416 * See the comments in make_ga_colormap for how this works in the
2417 * per-pixel processing.
2418 *
2419 * If the background is gray, however, we only need a 256 entry gray
2420 * level color map. It is sufficient to make the entry generated
2421 * for the background color be exactly the color specified.
2422 */
2423 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2424 (back_r == back_g && back_g == back_b))
2425 {
2426 /* Background is gray; no special processing will be required. */
2427 png_color_16 c;
2428 png_uint_32 gray = back_g;
2429
2430 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2431 png_error(png_ptr, "gray-alpha color-map: too few entries");
2432
2433 cmap_entries = (unsigned int)make_gray_colormap(display);
2434
2435 if (output_encoding == P_LINEAR)
2436 {
2437 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2438
2439 /* And make sure the corresponding palette entry matches. */
2440 png_create_colormap_entry(display, gray, back_g, back_g,
2441 back_g, 65535, P_LINEAR);
2442 }
2443
2444 /* The background passed to libpng, however, must be the sRGB
2445 * value.
2446 */
2447 c.index = 0; /*unused*/
2448 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2449
2450 png_set_background_fixed(png_ptr, &c,
2451 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2452 0/*gamma: not used*/);
2453
2454 output_processing = PNG_CMAP_NONE;
2455 }
2456
2457 else
2458 {
2459 png_uint_32 i, a;
2460
2461 /* This is the same as png_make_ga_colormap, above, except that
2462 * the entries are all opaque.
2463 */
2464 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2465 png_error(png_ptr, "ga-alpha color-map: too few entries");
2466
2467 i = 0;
2468 while (i < 231)
2469 {
2470 png_uint_32 gray = (i * 256 + 115) / 231;
2471 png_create_colormap_entry(display, i++, gray, gray, gray,
2472 255, P_sRGB);
2473 }
2474
2475 /* NOTE: this preserves the full precision of the application
2476 * background color.
2477 */
2478 background_index = i;
2479 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2480 #ifdef __COVERITY__
2481 /* Coverity claims that output_encoding
2482 * cannot be 2 (P_LINEAR) here.
2483 */ 255U,
2484 #else
2485 output_encoding == P_LINEAR ? 65535U : 255U,
2486 #endif
2487 output_encoding);
2488
2489 /* For non-opaque input composite on the sRGB background - this
2490 * requires inverting the encoding for each component. The input
2491 * is still converted to the sRGB encoding because this is a
2492 * reasonable approximate to the logarithmic curve of human
2493 * visual sensitivity, at least over the narrow range which PNG
2494 * represents. Consequently 'G' is always sRGB encoded, while
2495 * 'A' is linear. We need the linear background colors.
2496 */
2497 if (output_encoding == P_sRGB) /* else already linear */
2498 {
2499 /* This may produce a value not exactly matching the
2500 * background, but that's ok because these numbers are only
2501 * used when alpha != 0
2502 */
2503 back_r = png_sRGB_table[back_r];
2504 back_g = png_sRGB_table[back_g];
2505 back_b = png_sRGB_table[back_b];
2506 }
2507
2508 for (a=1; a<5; ++a)
2509 {
2510 unsigned int g;
2511
2512 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2513 * by an 8-bit alpha value (0..255).
2514 */
2515 png_uint_32 alpha = 51 * a;
2516 png_uint_32 back_rx = (255-alpha) * back_r;
2517 png_uint_32 back_gx = (255-alpha) * back_g;
2518 png_uint_32 back_bx = (255-alpha) * back_b;
2519
2520 for (g=0; g<6; ++g)
2521 {
2522 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2523
2524 png_create_colormap_entry(display, i++,
2525 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2526 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2527 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2528 }
2529 }
2530
2531 cmap_entries = i;
2532 output_processing = PNG_CMAP_GA;
2533 }
2534 }
2535 break;
2536
2537 case PNG_COLOR_TYPE_RGB:
2538 case PNG_COLOR_TYPE_RGB_ALPHA:
2539 /* Exclude the case where the output is gray; we can always handle this
2540 * with the cases above.
2541 */
2542 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2543 {
2544 /* The color-map will be grayscale, so we may as well convert the
2545 * input RGB values to a simple grayscale and use the grayscale
2546 * code above.
2547 *
2548 * NOTE: calling this apparently damages the recognition of the
2549 * transparent color in background color handling; call
2550 * png_set_tRNS_to_alpha before png_set_background_fixed.
2551 */
2552 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2553 -1);
2554 data_encoding = P_sRGB;
2555
2556 /* The output will now be one or two 8-bit gray or gray+alpha
2557 * channels. The more complex case arises when the input has alpha.
2558 */
2559 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2560 png_ptr->num_trans > 0) &&
2561 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2562 {
2563 /* Both input and output have an alpha channel, so no background
2564 * processing is required; just map the GA bytes to the right
2565 * color-map entry.
2566 */
2567 expand_tRNS = 1;
2568
2569 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2570 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2571
2572 cmap_entries = (unsigned int)make_ga_colormap(display);
2573 background_index = PNG_CMAP_GA_BACKGROUND;
2574 output_processing = PNG_CMAP_GA;
2575 }
2576
2577 else
2578 {
2579 /* Either the input or the output has no alpha channel, so there
2580 * will be no non-opaque pixels in the color-map; it will just be
2581 * grayscale.
2582 */
2583 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2584 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2585
2586 /* Ideally this code would use libpng to do the gamma correction,
2587 * but if an input alpha channel is to be removed we will hit the
2588 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2589 * correction bug). Fix this by dropping the gamma correction in
2590 * this case and doing it in the palette; this will result in
2591 * duplicate palette entries, but that's better than the
2592 * alternative of double gamma correction.
2593 */
2594 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2595 png_ptr->num_trans > 0) &&
2596 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2597 {
2598 cmap_entries = (unsigned int)make_gray_file_colormap(display);
2599 data_encoding = P_FILE;
2600 }
2601
2602 else
2603 cmap_entries = (unsigned int)make_gray_colormap(display);
2604
2605 /* But if the input has alpha or transparency it must be removed
2606 */
2607 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2608 png_ptr->num_trans > 0)
2609 {
2610 png_color_16 c;
2611 png_uint_32 gray = back_g;
2612
2613 /* We need to ensure that the application background exists in
2614 * the colormap and that completely transparent pixels map to
2615 * it. Achieve this simply by ensuring that the entry
2616 * selected for the background really is the background color.
2617 */
2618 if (data_encoding == P_FILE) /* from the fixup above */
2619 {
2620 /* The app supplied a gray which is in output_encoding, we
2621 * need to convert it to a value of the input (P_FILE)
2622 * encoding then set this palette entry to the required
2623 * output encoding.
2624 */
2625 if (output_encoding == P_sRGB)
2626 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2627
2628 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2629 png_ptr->colorspace.gamma)); /* now P_FILE */
2630
2631 /* And make sure the corresponding palette entry contains
2632 * exactly the required sRGB value.
2633 */
2634 png_create_colormap_entry(display, gray, back_g, back_g,
2635 back_g, 0/*unused*/, output_encoding);
2636 }
2637
2638 else if (output_encoding == P_LINEAR)
2639 {
2640 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2641
2642 /* And make sure the corresponding palette entry matches.
2643 */
2644 png_create_colormap_entry(display, gray, back_g, back_g,
2645 back_g, 0/*unused*/, P_LINEAR);
2646 }
2647
2648 /* The background passed to libpng, however, must be the
2649 * output (normally sRGB) value.
2650 */
2651 c.index = 0; /*unused*/
2652 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2653
2654 /* NOTE: the following is apparently a bug in libpng. Without
2655 * it the transparent color recognition in
2656 * png_set_background_fixed seems to go wrong.
2657 */
2658 expand_tRNS = 1;
2659 png_set_background_fixed(png_ptr, &c,
2660 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2661 0/*gamma: not used*/);
2662 }
2663
2664 output_processing = PNG_CMAP_NONE;
2665 }
2666 }
2667
2668 else /* output is color */
2669 {
2670 /* We could use png_quantize here so long as there is no transparent
2671 * color or alpha; png_quantize ignores alpha. Easier overall just
2672 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2673 * Consequently we always want libpng to produce sRGB data.
2674 */
2675 data_encoding = P_sRGB;
2676
2677 /* Is there any transparency or alpha? */
2678 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2679 png_ptr->num_trans > 0)
2680 {
2681 /* Is there alpha in the output too? If so all four channels are
2682 * processed into a special RGB cube with alpha support.
2683 */
2684 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2685 {
2686 png_uint_32 r;
2687
2688 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2689 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2690
2691 cmap_entries = (unsigned int)make_rgb_colormap(display);
2692
2693 /* Add a transparent entry. */
2694 png_create_colormap_entry(display, cmap_entries, 255, 255,
2695 255, 0, P_sRGB);
2696
2697 /* This is stored as the background index for the processing
2698 * algorithm.
2699 */
2700 background_index = cmap_entries++;
2701
2702 /* Add 27 r,g,b entries each with alpha 0.5. */
2703 for (r=0; r<256; r = (r << 1) | 0x7f)
2704 {
2705 png_uint_32 g;
2706
2707 for (g=0; g<256; g = (g << 1) | 0x7f)
2708 {
2709 png_uint_32 b;
2710
2711 /* This generates components with the values 0, 127 and
2712 * 255
2713 */
2714 for (b=0; b<256; b = (b << 1) | 0x7f)
2715 png_create_colormap_entry(display, cmap_entries++,
2716 r, g, b, 128, P_sRGB);
2717 }
2718 }
2719
2720 expand_tRNS = 1;
2721 output_processing = PNG_CMAP_RGB_ALPHA;
2722 }
2723
2724 else
2725 {
2726 /* Alpha/transparency must be removed. The background must
2727 * exist in the color map (achieved by setting adding it after
2728 * the 666 color-map). If the standard processing code will
2729 * pick up this entry automatically that's all that is
2730 * required; libpng can be called to do the background
2731 * processing.
2732 */
2733 unsigned int sample_size =
2734 PNG_IMAGE_SAMPLE_SIZE(output_format);
2735 png_uint_32 r, g, b; /* sRGB background */
2736
2737 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2738 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2739
2740 cmap_entries = (unsigned int)make_rgb_colormap(display);
2741
2742 png_create_colormap_entry(display, cmap_entries, back_r,
2743 back_g, back_b, 0/*unused*/, output_encoding);
2744
2745 if (output_encoding == P_LINEAR)
2746 {
2747 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2748 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2749 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2750 }
2751
2752 else
2753 {
2754 r = back_r;
2755 g = back_g;
2756 b = back_g;
2757 }
2758
2759 /* Compare the newly-created color-map entry with the one the
2760 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2761 * match, add the new one and set this as the background
2762 * index.
2763 */
2764 if (memcmp((png_const_bytep)display->colormap +
2765 sample_size * cmap_entries,
2766 (png_const_bytep)display->colormap +
2767 sample_size * PNG_RGB_INDEX(r,g,b),
2768 sample_size) != 0)
2769 {
2770 /* The background color must be added. */
2771 background_index = cmap_entries++;
2772
2773 /* Add 27 r,g,b entries each with created by composing with
2774 * the background at alpha 0.5.
2775 */
2776 for (r=0; r<256; r = (r << 1) | 0x7f)
2777 {
2778 for (g=0; g<256; g = (g << 1) | 0x7f)
2779 {
2780 /* This generates components with the values 0, 127
2781 * and 255
2782 */
2783 for (b=0; b<256; b = (b << 1) | 0x7f)
2784 png_create_colormap_entry(display, cmap_entries++,
2785 png_colormap_compose(display, r, P_sRGB, 128,
2786 back_r, output_encoding),
2787 png_colormap_compose(display, g, P_sRGB, 128,
2788 back_g, output_encoding),
2789 png_colormap_compose(display, b, P_sRGB, 128,
2790 back_b, output_encoding),
2791 0/*unused*/, output_encoding);
2792 }
2793 }
2794
2795 expand_tRNS = 1;
2796 output_processing = PNG_CMAP_RGB_ALPHA;
2797 }
2798
2799 else /* background color is in the standard color-map */
2800 {
2801 png_color_16 c;
2802
2803 c.index = 0; /*unused*/
2804 c.red = (png_uint_16)back_r;
2805 c.gray = c.green = (png_uint_16)back_g;
2806 c.blue = (png_uint_16)back_b;
2807
2808 png_set_background_fixed(png_ptr, &c,
2809 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2810 0/*gamma: not used*/);
2811
2812 output_processing = PNG_CMAP_RGB;
2813 }
2814 }
2815 }
2816
2817 else /* no alpha or transparency in the input */
2818 {
2819 /* Alpha in the output is irrelevant, simply map the opaque input
2820 * pixels to the 6x6x6 color-map.
2821 */
2822 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2823 png_error(png_ptr, "rgb color-map: too few entries");
2824
2825 cmap_entries = (unsigned int)make_rgb_colormap(display);
2826 output_processing = PNG_CMAP_RGB;
2827 }
2828 }
2829 break;
2830
2831 case PNG_COLOR_TYPE_PALETTE:
2832 /* It's already got a color-map. It may be necessary to eliminate the
2833 * tRNS entries though.
2834 */
2835 {
2836 unsigned int num_trans = png_ptr->num_trans;
2837 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2838 png_const_colorp colormap = png_ptr->palette;
2839 int do_background = trans != NULL &&
2840 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2841 unsigned int i;
2842
2843 /* Just in case: */
2844 if (trans == NULL)
2845 num_trans = 0;
2846
2847 output_processing = PNG_CMAP_NONE;
2848 data_encoding = P_FILE; /* Don't change from color-map indices */
2849 cmap_entries = (unsigned int)png_ptr->num_palette;
2850 if (cmap_entries > 256)
2851 cmap_entries = 256;
2852
2853 if (cmap_entries > (unsigned int)image->colormap_entries)
2854 png_error(png_ptr, "palette color-map: too few entries");
2855
2856 for (i=0; i < cmap_entries; ++i)
2857 {
2858 if (do_background != 0 && i < num_trans && trans[i] < 255)
2859 {
2860 if (trans[i] == 0)
2861 png_create_colormap_entry(display, i, back_r, back_g,
2862 back_b, 0, output_encoding);
2863
2864 else
2865 {
2866 /* Must compose the PNG file color in the color-map entry
2867 * on the sRGB color in 'back'.
2868 */
2869 png_create_colormap_entry(display, i,
2870 png_colormap_compose(display, colormap[i].red,
2871 P_FILE, trans[i], back_r, output_encoding),
2872 png_colormap_compose(display, colormap[i].green,
2873 P_FILE, trans[i], back_g, output_encoding),
2874 png_colormap_compose(display, colormap[i].blue,
2875 P_FILE, trans[i], back_b, output_encoding),
2876 output_encoding == P_LINEAR ? trans[i] * 257U :
2877 trans[i],
2878 output_encoding);
2879 }
2880 }
2881
2882 else
2883 png_create_colormap_entry(display, i, colormap[i].red,
2884 colormap[i].green, colormap[i].blue,
2885 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2886 }
2887
2888 /* The PNG data may have indices packed in fewer than 8 bits, it
2889 * must be expanded if so.
2890 */
2891 if (png_ptr->bit_depth < 8)
2892 png_set_packing(png_ptr);
2893 }
2894 break;
2895
2896 default:
2897 png_error(png_ptr, "invalid PNG color type");
2898 /*NOT REACHED*/
2899 }
2900
2901 /* Now deal with the output processing */
2902 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2903 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2904 png_set_tRNS_to_alpha(png_ptr);
2905
2906 switch (data_encoding)
2907 {
2908 case P_sRGB:
2909 /* Change to 8-bit sRGB */
2910 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2911 /* FALLTHROUGH */
2912
2913 case P_FILE:
2914 if (png_ptr->bit_depth > 8)
2915 png_set_scale_16(png_ptr);
2916 break;
2917
2918 #ifdef __GNUC__
2919 default:
2920 png_error(png_ptr, "bad data option (internal error)");
2921 #endif
2922 }
2923
2924 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2925 png_error(png_ptr, "color map overflow (BAD internal error)");
2926
2927 image->colormap_entries = cmap_entries;
2928
2929 /* Double check using the recorded background index */
2930 switch (output_processing)
2931 {
2932 case PNG_CMAP_NONE:
2933 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2934 goto bad_background;
2935 break;
2936
2937 case PNG_CMAP_GA:
2938 if (background_index != PNG_CMAP_GA_BACKGROUND)
2939 goto bad_background;
2940 break;
2941
2942 case PNG_CMAP_TRANS:
2943 if (background_index >= cmap_entries ||
2944 background_index != PNG_CMAP_TRANS_BACKGROUND)
2945 goto bad_background;
2946 break;
2947
2948 case PNG_CMAP_RGB:
2949 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2950 goto bad_background;
2951 break;
2952
2953 case PNG_CMAP_RGB_ALPHA:
2954 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2955 goto bad_background;
2956 break;
2957
2958 default:
2959 png_error(png_ptr, "bad processing option (internal error)");
2960
2961 bad_background:
2962 png_error(png_ptr, "bad background index (internal error)");
2963 }
2964
2965 display->colormap_processing = (int)output_processing;
2966
2967 return 1/*ok*/;
2968 }
2969
2970 /* The final part of the color-map read called from png_image_finish_read. */
2971 static int
png_image_read_and_map(png_voidp argument)2972 png_image_read_and_map(png_voidp argument)
2973 {
2974 png_image_read_control *display = png_voidcast(png_image_read_control*,
2975 argument);
2976 png_imagep image = display->image;
2977 png_structrp png_ptr = image->opaque->png_ptr;
2978 int passes;
2979
2980 /* Called when the libpng data must be transformed into the color-mapped
2981 * form. There is a local row buffer in display->local and this routine must
2982 * do the interlace handling.
2983 */
2984 switch (png_ptr->interlaced)
2985 {
2986 case PNG_INTERLACE_NONE:
2987 passes = 1;
2988 break;
2989
2990 case PNG_INTERLACE_ADAM7:
2991 passes = PNG_INTERLACE_ADAM7_PASSES;
2992 break;
2993
2994 default:
2995 png_error(png_ptr, "unknown interlace type");
2996 }
2997
2998 {
2999 png_uint_32 height = image->height;
3000 png_uint_32 width = image->width;
3001 int proc = display->colormap_processing;
3002 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3003 ptrdiff_t step_row = display->row_bytes;
3004 int pass;
3005
3006 for (pass = 0; pass < passes; ++pass)
3007 {
3008 unsigned int startx, stepx, stepy;
3009 png_uint_32 y;
3010
3011 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3012 {
3013 /* The row may be empty for a short image: */
3014 if (PNG_PASS_COLS(width, pass) == 0)
3015 continue;
3016
3017 startx = PNG_PASS_START_COL(pass);
3018 stepx = PNG_PASS_COL_OFFSET(pass);
3019 y = PNG_PASS_START_ROW(pass);
3020 stepy = PNG_PASS_ROW_OFFSET(pass);
3021 }
3022
3023 else
3024 {
3025 y = 0;
3026 startx = 0;
3027 stepx = stepy = 1;
3028 }
3029
3030 for (; y<height; y += stepy)
3031 {
3032 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3033 png_bytep outrow = first_row + y * step_row;
3034 png_const_bytep end_row = outrow + width;
3035
3036 /* Read read the libpng data into the temporary buffer. */
3037 png_read_row(png_ptr, inrow, NULL);
3038
3039 /* Now process the row according to the processing option, note
3040 * that the caller verifies that the format of the libpng output
3041 * data is as required.
3042 */
3043 outrow += startx;
3044 switch (proc)
3045 {
3046 case PNG_CMAP_GA:
3047 for (; outrow < end_row; outrow += stepx)
3048 {
3049 /* The data is always in the PNG order */
3050 unsigned int gray = *inrow++;
3051 unsigned int alpha = *inrow++;
3052 unsigned int entry;
3053
3054 /* NOTE: this code is copied as a comment in
3055 * make_ga_colormap above. Please update the
3056 * comment if you change this code!
3057 */
3058 if (alpha > 229) /* opaque */
3059 {
3060 entry = (231 * gray + 128) >> 8;
3061 }
3062 else if (alpha < 26) /* transparent */
3063 {
3064 entry = 231;
3065 }
3066 else /* partially opaque */
3067 {
3068 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3069 }
3070
3071 *outrow = (png_byte)entry;
3072 }
3073 break;
3074
3075 case PNG_CMAP_TRANS:
3076 for (; outrow < end_row; outrow += stepx)
3077 {
3078 png_byte gray = *inrow++;
3079 png_byte alpha = *inrow++;
3080
3081 if (alpha == 0)
3082 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3083
3084 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3085 *outrow = gray;
3086
3087 else
3088 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3089 }
3090 break;
3091
3092 case PNG_CMAP_RGB:
3093 for (; outrow < end_row; outrow += stepx)
3094 {
3095 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3096 inrow += 3;
3097 }
3098 break;
3099
3100 case PNG_CMAP_RGB_ALPHA:
3101 for (; outrow < end_row; outrow += stepx)
3102 {
3103 unsigned int alpha = inrow[3];
3104
3105 /* Because the alpha entries only hold alpha==0.5 values
3106 * split the processing at alpha==0.25 (64) and 0.75
3107 * (196).
3108 */
3109
3110 if (alpha >= 196)
3111 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3112 inrow[2]);
3113
3114 else if (alpha < 64)
3115 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3116
3117 else
3118 {
3119 /* Likewise there are three entries for each of r, g
3120 * and b. We could select the entry by popcount on
3121 * the top two bits on those architectures that
3122 * support it, this is what the code below does,
3123 * crudely.
3124 */
3125 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3126
3127 /* Here are how the values map:
3128 *
3129 * 0x00 .. 0x3f -> 0
3130 * 0x40 .. 0xbf -> 1
3131 * 0xc0 .. 0xff -> 2
3132 *
3133 * So, as above with the explicit alpha checks, the
3134 * breakpoints are at 64 and 196.
3135 */
3136 if (inrow[0] & 0x80) back_i += 9; /* red */
3137 if (inrow[0] & 0x40) back_i += 9;
3138 if (inrow[0] & 0x80) back_i += 3; /* green */
3139 if (inrow[0] & 0x40) back_i += 3;
3140 if (inrow[0] & 0x80) back_i += 1; /* blue */
3141 if (inrow[0] & 0x40) back_i += 1;
3142
3143 *outrow = (png_byte)back_i;
3144 }
3145
3146 inrow += 4;
3147 }
3148 break;
3149
3150 default:
3151 break;
3152 }
3153 }
3154 }
3155 }
3156
3157 return 1;
3158 }
3159
3160 static int
png_image_read_colormapped(png_voidp argument)3161 png_image_read_colormapped(png_voidp argument)
3162 {
3163 png_image_read_control *display = png_voidcast(png_image_read_control*,
3164 argument);
3165 png_imagep image = display->image;
3166 png_controlp control = image->opaque;
3167 png_structrp png_ptr = control->png_ptr;
3168 png_inforp info_ptr = control->info_ptr;
3169
3170 int passes = 0; /* As a flag */
3171
3172 PNG_SKIP_CHUNKS(png_ptr);
3173
3174 /* Update the 'info' structure and make sure the result is as required; first
3175 * make sure to turn on the interlace handling if it will be required
3176 * (because it can't be turned on *after* the call to png_read_update_info!)
3177 */
3178 if (display->colormap_processing == PNG_CMAP_NONE)
3179 passes = png_set_interlace_handling(png_ptr);
3180
3181 png_read_update_info(png_ptr, info_ptr);
3182
3183 /* The expected output can be deduced from the colormap_processing option. */
3184 switch (display->colormap_processing)
3185 {
3186 case PNG_CMAP_NONE:
3187 /* Output must be one channel and one byte per pixel, the output
3188 * encoding can be anything.
3189 */
3190 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3191 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3192 info_ptr->bit_depth == 8)
3193 break;
3194
3195 goto bad_output;
3196
3197 case PNG_CMAP_TRANS:
3198 case PNG_CMAP_GA:
3199 /* Output must be two channels and the 'G' one must be sRGB, the latter
3200 * can be checked with an exact number because it should have been set
3201 * to this number above!
3202 */
3203 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3204 info_ptr->bit_depth == 8 &&
3205 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3206 image->colormap_entries == 256)
3207 break;
3208
3209 goto bad_output;
3210
3211 case PNG_CMAP_RGB:
3212 /* Output must be 8-bit sRGB encoded RGB */
3213 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3214 info_ptr->bit_depth == 8 &&
3215 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3216 image->colormap_entries == 216)
3217 break;
3218
3219 goto bad_output;
3220
3221 case PNG_CMAP_RGB_ALPHA:
3222 /* Output must be 8-bit sRGB encoded RGBA */
3223 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3224 info_ptr->bit_depth == 8 &&
3225 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3226 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3227 break;
3228
3229 goto bad_output;
3230
3231 default:
3232 bad_output:
3233 png_error(png_ptr, "bad color-map processing (internal error)");
3234 }
3235
3236 /* Now read the rows. Do this here if it is possible to read directly into
3237 * the output buffer, otherwise allocate a local row buffer of the maximum
3238 * size libpng requires and call the relevant processing routine safely.
3239 */
3240 {
3241 png_voidp first_row = display->buffer;
3242 ptrdiff_t row_bytes = display->row_stride;
3243
3244 /* The following expression is designed to work correctly whether it gives
3245 * a signed or an unsigned result.
3246 */
3247 if (row_bytes < 0)
3248 {
3249 char *ptr = png_voidcast(char*, first_row);
3250 ptr += (image->height-1) * (-row_bytes);
3251 first_row = png_voidcast(png_voidp, ptr);
3252 }
3253
3254 display->first_row = first_row;
3255 display->row_bytes = row_bytes;
3256 }
3257
3258 if (passes == 0)
3259 {
3260 int result;
3261 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3262
3263 display->local_row = row;
3264 result = png_safe_execute(image, png_image_read_and_map, display);
3265 display->local_row = NULL;
3266 png_free(png_ptr, row);
3267
3268 return result;
3269 }
3270
3271 else
3272 {
3273 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
3274
3275 while (--passes >= 0)
3276 {
3277 png_uint_32 y = image->height;
3278 png_bytep row = png_voidcast(png_bytep, display->first_row);
3279
3280 for (; y > 0; --y)
3281 {
3282 png_read_row(png_ptr, row, NULL);
3283 row += row_bytes;
3284 }
3285 }
3286
3287 return 1;
3288 }
3289 }
3290
3291 /* Just the row reading part of png_image_read. */
3292 static int
png_image_read_composite(png_voidp argument)3293 png_image_read_composite(png_voidp argument)
3294 {
3295 png_image_read_control *display = png_voidcast(png_image_read_control*,
3296 argument);
3297 png_imagep image = display->image;
3298 png_structrp png_ptr = image->opaque->png_ptr;
3299 int passes;
3300
3301 switch (png_ptr->interlaced)
3302 {
3303 case PNG_INTERLACE_NONE:
3304 passes = 1;
3305 break;
3306
3307 case PNG_INTERLACE_ADAM7:
3308 passes = PNG_INTERLACE_ADAM7_PASSES;
3309 break;
3310
3311 default:
3312 png_error(png_ptr, "unknown interlace type");
3313 }
3314
3315 {
3316 png_uint_32 height = image->height;
3317 png_uint_32 width = image->width;
3318 ptrdiff_t step_row = display->row_bytes;
3319 unsigned int channels =
3320 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3321 int pass;
3322
3323 for (pass = 0; pass < passes; ++pass)
3324 {
3325 unsigned int startx, stepx, stepy;
3326 png_uint_32 y;
3327
3328 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3329 {
3330 /* The row may be empty for a short image: */
3331 if (PNG_PASS_COLS(width, pass) == 0)
3332 continue;
3333
3334 startx = PNG_PASS_START_COL(pass) * channels;
3335 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3336 y = PNG_PASS_START_ROW(pass);
3337 stepy = PNG_PASS_ROW_OFFSET(pass);
3338 }
3339
3340 else
3341 {
3342 y = 0;
3343 startx = 0;
3344 stepx = channels;
3345 stepy = 1;
3346 }
3347
3348 for (; y<height; y += stepy)
3349 {
3350 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3351 png_bytep outrow;
3352 png_const_bytep end_row;
3353
3354 /* Read the row, which is packed: */
3355 png_read_row(png_ptr, inrow, NULL);
3356
3357 outrow = png_voidcast(png_bytep, display->first_row);
3358 outrow += y * step_row;
3359 end_row = outrow + width * channels;
3360
3361 /* Now do the composition on each pixel in this row. */
3362 outrow += startx;
3363 for (; outrow < end_row; outrow += stepx)
3364 {
3365 png_byte alpha = inrow[channels];
3366
3367 if (alpha > 0) /* else no change to the output */
3368 {
3369 unsigned int c;
3370
3371 for (c=0; c<channels; ++c)
3372 {
3373 png_uint_32 component = inrow[c];
3374
3375 if (alpha < 255) /* else just use component */
3376 {
3377 /* This is PNG_OPTIMIZED_ALPHA, the component value
3378 * is a linear 8-bit value. Combine this with the
3379 * current outrow[c] value which is sRGB encoded.
3380 * Arithmetic here is 16-bits to preserve the output
3381 * values correctly.
3382 */
3383 component *= 257*255; /* =65535 */
3384 component += (255-alpha)*png_sRGB_table[outrow[c]];
3385
3386 /* So 'component' is scaled by 255*65535 and is
3387 * therefore appropriate for the sRGB to linear
3388 * conversion table.
3389 */
3390 component = PNG_sRGB_FROM_LINEAR(component);
3391 }
3392
3393 outrow[c] = (png_byte)component;
3394 }
3395 }
3396
3397 inrow += channels+1; /* components and alpha channel */
3398 }
3399 }
3400 }
3401 }
3402
3403 return 1;
3404 }
3405
3406 /* The do_local_background case; called when all the following transforms are to
3407 * be done:
3408 *
3409 * PNG_RGB_TO_GRAY
3410 * PNG_COMPOSITE
3411 * PNG_GAMMA
3412 *
3413 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3414 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3415 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3416 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3417 * row and handles the removal or pre-multiplication of the alpha channel.
3418 */
3419 static int
png_image_read_background(png_voidp argument)3420 png_image_read_background(png_voidp argument)
3421 {
3422 png_image_read_control *display = png_voidcast(png_image_read_control*,
3423 argument);
3424 png_imagep image = display->image;
3425 png_structrp png_ptr = image->opaque->png_ptr;
3426 png_inforp info_ptr = image->opaque->info_ptr;
3427 png_uint_32 height = image->height;
3428 png_uint_32 width = image->width;
3429 int pass, passes;
3430
3431 /* Double check the convoluted logic below. We expect to get here with
3432 * libpng doing rgb to gray and gamma correction but background processing
3433 * left to the png_image_read_background function. The rows libpng produce
3434 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3435 */
3436 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3437 png_error(png_ptr, "lost rgb to gray");
3438
3439 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3440 png_error(png_ptr, "unexpected compose");
3441
3442 if (png_get_channels(png_ptr, info_ptr) != 2)
3443 png_error(png_ptr, "lost/gained channels");
3444
3445 /* Expect the 8-bit case to always remove the alpha channel */
3446 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3447 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3448 png_error(png_ptr, "unexpected 8-bit transformation");
3449
3450 switch (png_ptr->interlaced)
3451 {
3452 case PNG_INTERLACE_NONE:
3453 passes = 1;
3454 break;
3455
3456 case PNG_INTERLACE_ADAM7:
3457 passes = PNG_INTERLACE_ADAM7_PASSES;
3458 break;
3459
3460 default:
3461 png_error(png_ptr, "unknown interlace type");
3462 }
3463
3464 /* Use direct access to info_ptr here because otherwise the simplified API
3465 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3466 * checking the value after libpng expansions, not the original value in the
3467 * PNG.
3468 */
3469 switch (info_ptr->bit_depth)
3470 {
3471 case 8:
3472 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3473 * to be removed by composing on a background: either the row if
3474 * display->background is NULL or display->background->green if not.
3475 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3476 */
3477 {
3478 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3479 ptrdiff_t step_row = display->row_bytes;
3480
3481 for (pass = 0; pass < passes; ++pass)
3482 {
3483 png_bytep row = png_voidcast(png_bytep, display->first_row);
3484 unsigned int startx, stepx, stepy;
3485 png_uint_32 y;
3486
3487 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3488 {
3489 /* The row may be empty for a short image: */
3490 if (PNG_PASS_COLS(width, pass) == 0)
3491 continue;
3492
3493 startx = PNG_PASS_START_COL(pass);
3494 stepx = PNG_PASS_COL_OFFSET(pass);
3495 y = PNG_PASS_START_ROW(pass);
3496 stepy = PNG_PASS_ROW_OFFSET(pass);
3497 }
3498
3499 else
3500 {
3501 y = 0;
3502 startx = 0;
3503 stepx = stepy = 1;
3504 }
3505
3506 if (display->background == NULL)
3507 {
3508 for (; y<height; y += stepy)
3509 {
3510 png_bytep inrow = png_voidcast(png_bytep,
3511 display->local_row);
3512 png_bytep outrow = first_row + y * step_row;
3513 png_const_bytep end_row = outrow + width;
3514
3515 /* Read the row, which is packed: */
3516 png_read_row(png_ptr, inrow, NULL);
3517
3518 /* Now do the composition on each pixel in this row. */
3519 outrow += startx;
3520 for (; outrow < end_row; outrow += stepx)
3521 {
3522 png_byte alpha = inrow[1];
3523
3524 if (alpha > 0) /* else no change to the output */
3525 {
3526 png_uint_32 component = inrow[0];
3527
3528 if (alpha < 255) /* else just use component */
3529 {
3530 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3531 * necessary to invert the sRGB transfer
3532 * function and multiply the alpha out.
3533 */
3534 component = png_sRGB_table[component] * alpha;
3535 component += png_sRGB_table[outrow[0]] *
3536 (255-alpha);
3537 component = PNG_sRGB_FROM_LINEAR(component);
3538 }
3539
3540 outrow[0] = (png_byte)component;
3541 }
3542
3543 inrow += 2; /* gray and alpha channel */
3544 }
3545 }
3546 }
3547
3548 else /* constant background value */
3549 {
3550 png_byte background8 = display->background->green;
3551 png_uint_16 background = png_sRGB_table[background8];
3552
3553 for (; y<height; y += stepy)
3554 {
3555 png_bytep inrow = png_voidcast(png_bytep,
3556 display->local_row);
3557 png_bytep outrow = first_row + y * step_row;
3558 png_const_bytep end_row = outrow + width;
3559
3560 /* Read the row, which is packed: */
3561 png_read_row(png_ptr, inrow, NULL);
3562
3563 /* Now do the composition on each pixel in this row. */
3564 outrow += startx;
3565 for (; outrow < end_row; outrow += stepx)
3566 {
3567 png_byte alpha = inrow[1];
3568
3569 if (alpha > 0) /* else use background */
3570 {
3571 png_uint_32 component = inrow[0];
3572
3573 if (alpha < 255) /* else just use component */
3574 {
3575 component = png_sRGB_table[component] * alpha;
3576 component += background * (255-alpha);
3577 component = PNG_sRGB_FROM_LINEAR(component);
3578 }
3579
3580 outrow[0] = (png_byte)component;
3581 }
3582
3583 else
3584 outrow[0] = background8;
3585
3586 inrow += 2; /* gray and alpha channel */
3587 }
3588
3589 row += display->row_bytes;
3590 }
3591 }
3592 }
3593 }
3594 break;
3595
3596 case 16:
3597 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3598 * still be done and, maybe, the alpha channel removed. This code also
3599 * handles the alpha-first option.
3600 */
3601 {
3602 png_uint_16p first_row = png_voidcast(png_uint_16p,
3603 display->first_row);
3604 /* The division by two is safe because the caller passed in a
3605 * stride which was multiplied by 2 (below) to get row_bytes.
3606 */
3607 ptrdiff_t step_row = display->row_bytes / 2;
3608 unsigned int preserve_alpha = (image->format &
3609 PNG_FORMAT_FLAG_ALPHA) != 0;
3610 unsigned int outchannels = 1U+preserve_alpha;
3611 int swap_alpha = 0;
3612
3613 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3614 if (preserve_alpha != 0 &&
3615 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3616 swap_alpha = 1;
3617 # endif
3618
3619 for (pass = 0; pass < passes; ++pass)
3620 {
3621 unsigned int startx, stepx, stepy;
3622 png_uint_32 y;
3623
3624 /* The 'x' start and step are adjusted to output components here.
3625 */
3626 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3627 {
3628 /* The row may be empty for a short image: */
3629 if (PNG_PASS_COLS(width, pass) == 0)
3630 continue;
3631
3632 startx = PNG_PASS_START_COL(pass) * outchannels;
3633 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3634 y = PNG_PASS_START_ROW(pass);
3635 stepy = PNG_PASS_ROW_OFFSET(pass);
3636 }
3637
3638 else
3639 {
3640 y = 0;
3641 startx = 0;
3642 stepx = outchannels;
3643 stepy = 1;
3644 }
3645
3646 for (; y<height; y += stepy)
3647 {
3648 png_const_uint_16p inrow;
3649 png_uint_16p outrow = first_row + y*step_row;
3650 png_uint_16p end_row = outrow + width * outchannels;
3651
3652 /* Read the row, which is packed: */
3653 png_read_row(png_ptr, png_voidcast(png_bytep,
3654 display->local_row), NULL);
3655 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3656
3657 /* Now do the pre-multiplication on each pixel in this row.
3658 */
3659 outrow += startx;
3660 for (; outrow < end_row; outrow += stepx)
3661 {
3662 png_uint_32 component = inrow[0];
3663 png_uint_16 alpha = inrow[1];
3664
3665 if (alpha > 0) /* else 0 */
3666 {
3667 if (alpha < 65535) /* else just use component */
3668 {
3669 component *= alpha;
3670 component += 32767;
3671 component /= 65535;
3672 }
3673 }
3674
3675 else
3676 component = 0;
3677
3678 outrow[swap_alpha] = (png_uint_16)component;
3679 if (preserve_alpha != 0)
3680 outrow[1 ^ swap_alpha] = alpha;
3681
3682 inrow += 2; /* components and alpha channel */
3683 }
3684 }
3685 }
3686 }
3687 break;
3688
3689 #ifdef __GNUC__
3690 default:
3691 png_error(png_ptr, "unexpected bit depth");
3692 #endif
3693 }
3694
3695 return 1;
3696 }
3697
3698 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3699 static int
png_image_read_direct(png_voidp argument)3700 png_image_read_direct(png_voidp argument)
3701 {
3702 png_image_read_control *display = png_voidcast(png_image_read_control*,
3703 argument);
3704 png_imagep image = display->image;
3705 png_structrp png_ptr = image->opaque->png_ptr;
3706 png_inforp info_ptr = image->opaque->info_ptr;
3707
3708 png_uint_32 format = image->format;
3709 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3710 int do_local_compose = 0;
3711 int do_local_background = 0; /* to avoid double gamma correction bug */
3712 int passes = 0;
3713
3714 /* Add transforms to ensure the correct output format is produced then check
3715 * that the required implementation support is there. Always expand; always
3716 * need 8 bits minimum, no palette and expanded tRNS.
3717 */
3718 png_set_expand(png_ptr);
3719
3720 /* Now check the format to see if it was modified. */
3721 {
3722 png_uint_32 base_format = png_image_format(png_ptr) &
3723 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3724 png_uint_32 change = format ^ base_format;
3725 png_fixed_point output_gamma;
3726 int mode; /* alpha mode */
3727
3728 /* Do this first so that we have a record if rgb to gray is happening. */
3729 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3730 {
3731 /* gray<->color transformation required. */
3732 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3733 png_set_gray_to_rgb(png_ptr);
3734
3735 else
3736 {
3737 /* libpng can't do both rgb to gray and
3738 * background/pre-multiplication if there is also significant gamma
3739 * correction, because both operations require linear colors and
3740 * the code only supports one transform doing the gamma correction.
3741 * Handle this by doing the pre-multiplication or background
3742 * operation in this code, if necessary.
3743 *
3744 * TODO: fix this by rewriting pngrtran.c (!)
3745 *
3746 * For the moment (given that fixing this in pngrtran.c is an
3747 * enormous change) 'do_local_background' is used to indicate that
3748 * the problem exists.
3749 */
3750 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3751 do_local_background = 1/*maybe*/;
3752
3753 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3754 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3755 }
3756
3757 change &= ~PNG_FORMAT_FLAG_COLOR;
3758 }
3759
3760 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3761 */
3762 {
3763 png_fixed_point input_gamma_default;
3764
3765 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3766 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3767 input_gamma_default = PNG_GAMMA_LINEAR;
3768 else
3769 input_gamma_default = PNG_DEFAULT_sRGB;
3770
3771 /* Call png_set_alpha_mode to set the default for the input gamma; the
3772 * output gamma is set by a second call below.
3773 */
3774 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3775 }
3776
3777 if (linear != 0)
3778 {
3779 /* If there *is* an alpha channel in the input it must be multiplied
3780 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3781 */
3782 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3783 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3784
3785 else
3786 mode = PNG_ALPHA_PNG;
3787
3788 output_gamma = PNG_GAMMA_LINEAR;
3789 }
3790
3791 else
3792 {
3793 mode = PNG_ALPHA_PNG;
3794 output_gamma = PNG_DEFAULT_sRGB;
3795 }
3796
3797 if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0)
3798 {
3799 mode = PNG_ALPHA_OPTIMIZED;
3800 change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
3801 }
3802
3803 /* If 'do_local_background' is set check for the presence of gamma
3804 * correction; this is part of the work-round for the libpng bug
3805 * described above.
3806 *
3807 * TODO: fix libpng and remove this.
3808 */
3809 if (do_local_background != 0)
3810 {
3811 png_fixed_point gtest;
3812
3813 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3814 * gamma correction, the screen gamma hasn't been set on png_struct
3815 * yet; it's set below. png_struct::gamma, however, is set to the
3816 * final value.
3817 */
3818 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3819 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3820 do_local_background = 0;
3821
3822 else if (mode == PNG_ALPHA_STANDARD)
3823 {
3824 do_local_background = 2/*required*/;
3825 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3826 }
3827
3828 /* else leave as 1 for the checks below */
3829 }
3830
3831 /* If the bit-depth changes then handle that here. */
3832 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3833 {
3834 if (linear != 0 /*16-bit output*/)
3835 png_set_expand_16(png_ptr);
3836
3837 else /* 8-bit output */
3838 png_set_scale_16(png_ptr);
3839
3840 change &= ~PNG_FORMAT_FLAG_LINEAR;
3841 }
3842
3843 /* Now the background/alpha channel changes. */
3844 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3845 {
3846 /* Removing an alpha channel requires composition for the 8-bit
3847 * formats; for the 16-bit it is already done, above, by the
3848 * pre-multiplication and the channel just needs to be stripped.
3849 */
3850 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3851 {
3852 /* If RGB->gray is happening the alpha channel must be left and the
3853 * operation completed locally.
3854 *
3855 * TODO: fix libpng and remove this.
3856 */
3857 if (do_local_background != 0)
3858 do_local_background = 2/*required*/;
3859
3860 /* 16-bit output: just remove the channel */
3861 else if (linear != 0) /* compose on black (well, pre-multiply) */
3862 png_set_strip_alpha(png_ptr);
3863
3864 /* 8-bit output: do an appropriate compose */
3865 else if (display->background != NULL)
3866 {
3867 png_color_16 c;
3868
3869 c.index = 0; /*unused*/
3870 c.red = display->background->red;
3871 c.green = display->background->green;
3872 c.blue = display->background->blue;
3873 c.gray = display->background->green;
3874
3875 /* This is always an 8-bit sRGB value, using the 'green' channel
3876 * for gray is much better than calculating the luminance here;
3877 * we can get off-by-one errors in that calculation relative to
3878 * the app expectations and that will show up in transparent
3879 * pixels.
3880 */
3881 png_set_background_fixed(png_ptr, &c,
3882 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3883 0/*gamma: not used*/);
3884 }
3885
3886 else /* compose on row: implemented below. */
3887 {
3888 do_local_compose = 1;
3889 /* This leaves the alpha channel in the output, so it has to be
3890 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3891 * one so the code only has to hack on the pixels that require
3892 * composition.
3893 */
3894 mode = PNG_ALPHA_OPTIMIZED;
3895 }
3896 }
3897
3898 else /* output needs an alpha channel */
3899 {
3900 /* This is tricky because it happens before the swap operation has
3901 * been accomplished; however, the swap does *not* swap the added
3902 * alpha channel (weird API), so it must be added in the correct
3903 * place.
3904 */
3905 png_uint_32 filler; /* opaque filler */
3906 int where;
3907
3908 if (linear != 0)
3909 filler = 65535;
3910
3911 else
3912 filler = 255;
3913
3914 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3915 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3916 {
3917 where = PNG_FILLER_BEFORE;
3918 change &= ~PNG_FORMAT_FLAG_AFIRST;
3919 }
3920
3921 else
3922 #endif
3923 where = PNG_FILLER_AFTER;
3924
3925 png_set_add_alpha(png_ptr, filler, where);
3926 }
3927
3928 /* This stops the (irrelevant) call to swap_alpha below. */
3929 change &= ~PNG_FORMAT_FLAG_ALPHA;
3930 }
3931
3932 /* Now set the alpha mode correctly; this is always done, even if there is
3933 * no alpha channel in either the input or the output because it correctly
3934 * sets the output gamma.
3935 */
3936 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3937
3938 # ifdef PNG_FORMAT_BGR_SUPPORTED
3939 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3940 {
3941 /* Check only the output format; PNG is never BGR; don't do this if
3942 * the output is gray, but fix up the 'format' value in that case.
3943 */
3944 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3945 png_set_bgr(png_ptr);
3946
3947 else
3948 format &= ~PNG_FORMAT_FLAG_BGR;
3949
3950 change &= ~PNG_FORMAT_FLAG_BGR;
3951 }
3952 # endif
3953
3954 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3955 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3956 {
3957 /* Only relevant if there is an alpha channel - it's particularly
3958 * important to handle this correctly because do_local_compose may
3959 * be set above and then libpng will keep the alpha channel for this
3960 * code to remove.
3961 */
3962 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3963 {
3964 /* Disable this if doing a local background,
3965 * TODO: remove this when local background is no longer required.
3966 */
3967 if (do_local_background != 2)
3968 png_set_swap_alpha(png_ptr);
3969 }
3970
3971 else
3972 format &= ~PNG_FORMAT_FLAG_AFIRST;
3973
3974 change &= ~PNG_FORMAT_FLAG_AFIRST;
3975 }
3976 # endif
3977
3978 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3979 * architecture.
3980 */
3981 if (linear != 0)
3982 {
3983 png_uint_16 le = 0x0001;
3984
3985 if ((*(png_const_bytep) & le) != 0)
3986 png_set_swap(png_ptr);
3987 }
3988
3989 /* If change is not now 0 some transformation is missing - error out. */
3990 if (change != 0)
3991 png_error(png_ptr, "png_read_image: unsupported transformation");
3992 }
3993
3994 PNG_SKIP_CHUNKS(png_ptr);
3995
3996 /* Update the 'info' structure and make sure the result is as required; first
3997 * make sure to turn on the interlace handling if it will be required
3998 * (because it can't be turned on *after* the call to png_read_update_info!)
3999 *
4000 * TODO: remove the do_local_background fixup below.
4001 */
4002 if (do_local_compose == 0 && do_local_background != 2)
4003 passes = png_set_interlace_handling(png_ptr);
4004
4005 png_read_update_info(png_ptr, info_ptr);
4006
4007 {
4008 png_uint_32 info_format = 0;
4009
4010 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
4011 info_format |= PNG_FORMAT_FLAG_COLOR;
4012
4013 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
4014 {
4015 /* do_local_compose removes this channel below. */
4016 if (do_local_compose == 0)
4017 {
4018 /* do_local_background does the same if required. */
4019 if (do_local_background != 2 ||
4020 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
4021 info_format |= PNG_FORMAT_FLAG_ALPHA;
4022 }
4023 }
4024
4025 else if (do_local_compose != 0) /* internal error */
4026 png_error(png_ptr, "png_image_read: alpha channel lost");
4027
4028 if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) {
4029 info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
4030 }
4031
4032 if (info_ptr->bit_depth == 16)
4033 info_format |= PNG_FORMAT_FLAG_LINEAR;
4034
4035 #ifdef PNG_FORMAT_BGR_SUPPORTED
4036 if ((png_ptr->transformations & PNG_BGR) != 0)
4037 info_format |= PNG_FORMAT_FLAG_BGR;
4038 #endif
4039
4040 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
4041 if (do_local_background == 2)
4042 {
4043 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4044 info_format |= PNG_FORMAT_FLAG_AFIRST;
4045 }
4046
4047 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4048 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4049 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4050 {
4051 if (do_local_background == 2)
4052 png_error(png_ptr, "unexpected alpha swap transformation");
4053
4054 info_format |= PNG_FORMAT_FLAG_AFIRST;
4055 }
4056 # endif
4057
4058 /* This is actually an internal error. */
4059 if (info_format != format)
4060 png_error(png_ptr, "png_read_image: invalid transformations");
4061 }
4062
4063 /* Now read the rows. If do_local_compose is set then it is necessary to use
4064 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4065 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4066 * display acts as a flag.
4067 */
4068 {
4069 png_voidp first_row = display->buffer;
4070 ptrdiff_t row_bytes = display->row_stride;
4071
4072 if (linear != 0)
4073 row_bytes *= 2;
4074
4075 /* The following expression is designed to work correctly whether it gives
4076 * a signed or an unsigned result.
4077 */
4078 if (row_bytes < 0)
4079 {
4080 char *ptr = png_voidcast(char*, first_row);
4081 ptr += (image->height-1) * (-row_bytes);
4082 first_row = png_voidcast(png_voidp, ptr);
4083 }
4084
4085 display->first_row = first_row;
4086 display->row_bytes = row_bytes;
4087 }
4088
4089 if (do_local_compose != 0)
4090 {
4091 int result;
4092 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4093
4094 display->local_row = row;
4095 result = png_safe_execute(image, png_image_read_composite, display);
4096 display->local_row = NULL;
4097 png_free(png_ptr, row);
4098
4099 return result;
4100 }
4101
4102 else if (do_local_background == 2)
4103 {
4104 int result;
4105 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4106
4107 display->local_row = row;
4108 result = png_safe_execute(image, png_image_read_background, display);
4109 display->local_row = NULL;
4110 png_free(png_ptr, row);
4111
4112 return result;
4113 }
4114
4115 else
4116 {
4117 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
4118
4119 while (--passes >= 0)
4120 {
4121 png_uint_32 y = image->height;
4122 png_bytep row = png_voidcast(png_bytep, display->first_row);
4123
4124 for (; y > 0; --y)
4125 {
4126 png_read_row(png_ptr, row, NULL);
4127 row += row_bytes;
4128 }
4129 }
4130
4131 return 1;
4132 }
4133 }
4134
4135 int PNGAPI
png_image_finish_read(png_imagep image,png_const_colorp background,void * buffer,png_int_32 row_stride,void * colormap)4136 png_image_finish_read(png_imagep image, png_const_colorp background,
4137 void *buffer, png_int_32 row_stride, void *colormap)
4138 {
4139 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4140 {
4141 /* Check for row_stride overflow. This check is not performed on the
4142 * original PNG format because it may not occur in the output PNG format
4143 * and libpng deals with the issues of reading the original.
4144 */
4145 unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4146
4147 /* The following checks just the 'row_stride' calculation to ensure it
4148 * fits in a signed 32-bit value. Because channels/components can be
4149 * either 1 or 2 bytes in size the length of a row can still overflow 32
4150 * bits; this is just to verify that the 'row_stride' argument can be
4151 * represented.
4152 */
4153 if (image->width <= 0x7fffffffU/channels) /* no overflow */
4154 {
4155 png_uint_32 check;
4156 png_uint_32 png_row_stride = image->width * channels;
4157
4158 if (row_stride == 0)
4159 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4160
4161 if (row_stride < 0)
4162 check = (png_uint_32)(-row_stride);
4163
4164 else
4165 check = (png_uint_32)row_stride;
4166
4167 /* This verifies 'check', the absolute value of the actual stride
4168 * passed in and detects overflow in the application calculation (i.e.
4169 * if the app did actually pass in a non-zero 'row_stride'.
4170 */
4171 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4172 {
4173 /* Now check for overflow of the image buffer calculation; this
4174 * limits the whole image size to 32 bits for API compatibility with
4175 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4176 *
4177 * The PNG_IMAGE_BUFFER_SIZE macro is:
4178 *
4179 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4180 *
4181 * And the component size is always 1 or 2, so make sure that the
4182 * number of *bytes* that the application is saying are available
4183 * does actually fit into a 32-bit number.
4184 *
4185 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4186 * will be changed to use png_alloc_size_t; bigger images can be
4187 * accommodated on 64-bit systems.
4188 */
4189 if (image->height <=
4190 0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
4191 {
4192 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4193 (image->colormap_entries > 0 && colormap != NULL))
4194 {
4195 int result;
4196 png_image_read_control display;
4197
4198 memset(&display, 0, (sizeof display));
4199 display.image = image;
4200 display.buffer = buffer;
4201 display.row_stride = row_stride;
4202 display.colormap = colormap;
4203 display.background = background;
4204 display.local_row = NULL;
4205
4206 /* Choose the correct 'end' routine; for the color-map case
4207 * all the setup has already been done.
4208 */
4209 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4210 result =
4211 png_safe_execute(image,
4212 png_image_read_colormap, &display) &&
4213 png_safe_execute(image,
4214 png_image_read_colormapped, &display);
4215
4216 else
4217 result =
4218 png_safe_execute(image,
4219 png_image_read_direct, &display);
4220
4221 png_image_free(image);
4222 return result;
4223 }
4224
4225 else
4226 return png_image_error(image,
4227 "png_image_finish_read[color-map]: no color-map");
4228 }
4229
4230 else
4231 return png_image_error(image,
4232 "png_image_finish_read: image too large");
4233 }
4234
4235 else
4236 return png_image_error(image,
4237 "png_image_finish_read: invalid argument");
4238 }
4239
4240 else
4241 return png_image_error(image,
4242 "png_image_finish_read: row_stride too large");
4243 }
4244
4245 else if (image != NULL)
4246 return png_image_error(image,
4247 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4248
4249 return 0;
4250 }
4251
4252 #endif /* SIMPLIFIED_READ */
4253 #endif /* READ */
4254