1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /* pngread.c - read a PNG file
26 *
27 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file and, per its terms, should not be removed:
31 *
32 * Last changed in libpng 1.6.17 [March 26, 2015]
33 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
34 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
35 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
36 *
37 * This code is released under the libpng license.
38 * For conditions of distribution and use, see the disclaimer
39 * and license in png.h
40 *
41 * This file contains routines that an application calls directly to
42 * read a PNG file or stream.
43 */
44
45 #include "pngpriv.h"
46 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
47 # include <errno.h>
48 #endif
49
50 #ifdef PNG_READ_SUPPORTED
51
52 /* Create a PNG structure for reading, and allocate any memory needed. */
53 PNG_FUNCTION(png_structp,PNGAPI
54 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
55 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
56 {
57 #ifndef PNG_USER_MEM_SUPPORTED
58 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
59 error_fn, warn_fn, NULL, NULL, NULL);
60 #else
61 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
62 warn_fn, NULL, NULL, NULL);
63 }
64
65 /* Alternate create PNG structure for reading, and allocate any memory
66 * needed.
67 */
68 PNG_FUNCTION(png_structp,PNGAPI
69 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
70 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
71 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
72 {
73 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
74 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
75 #endif /* USER_MEM */
76
77 if (png_ptr != NULL)
78 {
79 png_ptr->mode = PNG_IS_READ_STRUCT;
80
81 /* Added in libpng-1.6.0; this can be used to detect a read structure if
82 * required (it will be zero in a write structure.)
83 */
84 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
85 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
86 # endif
87
88 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
89 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
90
91 /* In stable builds only warn if an application error can be completely
92 * handled.
93 */
94 # if PNG_RELEASE_BUILD
95 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
96 # endif
97 # endif
98
99 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
100 * do it itself) avoiding setting the default function if it is not
101 * required.
102 */
103 png_set_read_fn(png_ptr, NULL, NULL);
104 }
105
106 return png_ptr;
107 }
108
109
110 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
111 /* Read the information before the actual image data. This has been
112 * changed in v0.90 to allow reading a file that already has the magic
113 * bytes read from the stream. You can tell libpng how many bytes have
114 * been read from the beginning of the stream (up to the maximum of 8)
115 * via png_set_sig_bytes(), and we will only check the remaining bytes
116 * here. The application can then have access to the signature bytes we
117 * read if it is determined that this isn't a valid PNG file.
118 */
119 void PNGAPI
120 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
121 {
122 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
123 int keep;
124 #endif
125
126 png_debug(1, "in png_read_info");
127
128 if (png_ptr == NULL || info_ptr == NULL)
129 return;
130
131 /* Read and check the PNG file signature. */
132 png_read_sig(png_ptr, info_ptr);
133
134 for (;;)
135 {
136 png_uint_32 length = png_read_chunk_header(png_ptr);
137 png_uint_32 chunk_name = png_ptr->chunk_name;
138
139 /* IDAT logic needs to happen here to simplify getting the two flags
140 * right.
141 */
142 if (chunk_name == png_IDAT)
143 {
144 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
145 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
146
147 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
148 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
149 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
150
151 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
152 png_chunk_benign_error(png_ptr, "Too many IDATs found");
153
154 png_ptr->mode |= PNG_HAVE_IDAT;
155 }
156
157 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
158 png_ptr->mode |= PNG_AFTER_IDAT;
159
160 /* This should be a binary subdivision search or a hash for
161 * matching the chunk name rather than a linear search.
162 */
163 if (chunk_name == png_IHDR)
164 png_handle_IHDR(png_ptr, info_ptr, length);
165
166 else if (chunk_name == png_IEND)
167 png_handle_IEND(png_ptr, info_ptr, length);
168
169 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
170 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
171 {
172 png_handle_unknown(png_ptr, info_ptr, length, keep);
173
174 if (chunk_name == png_PLTE)
175 png_ptr->mode |= PNG_HAVE_PLTE;
176
177 else if (chunk_name == png_IDAT)
178 {
179 png_ptr->idat_size = 0; /* It has been consumed */
180 break;
181 }
182 }
183 #endif
184 else if (chunk_name == png_PLTE)
185 png_handle_PLTE(png_ptr, info_ptr, length);
186
187 else if (chunk_name == png_IDAT)
188 {
189 png_ptr->idat_size = length;
190 break;
191 }
192
193 #ifdef PNG_READ_bKGD_SUPPORTED
194 else if (chunk_name == png_bKGD)
195 png_handle_bKGD(png_ptr, info_ptr, length);
196 #endif
197
198 #ifdef PNG_READ_cHRM_SUPPORTED
199 else if (chunk_name == png_cHRM)
200 png_handle_cHRM(png_ptr, info_ptr, length);
201 #endif
202
203 #ifdef PNG_READ_gAMA_SUPPORTED
204 else if (chunk_name == png_gAMA)
205 png_handle_gAMA(png_ptr, info_ptr, length);
206 #endif
207
208 #ifdef PNG_READ_hIST_SUPPORTED
209 else if (chunk_name == png_hIST)
210 png_handle_hIST(png_ptr, info_ptr, length);
211 #endif
212
213 #ifdef PNG_READ_oFFs_SUPPORTED
214 else if (chunk_name == png_oFFs)
215 png_handle_oFFs(png_ptr, info_ptr, length);
216 #endif
217
218 #ifdef PNG_READ_pCAL_SUPPORTED
219 else if (chunk_name == png_pCAL)
220 png_handle_pCAL(png_ptr, info_ptr, length);
221 #endif
222
223 #ifdef PNG_READ_sCAL_SUPPORTED
224 else if (chunk_name == png_sCAL)
225 png_handle_sCAL(png_ptr, info_ptr, length);
226 #endif
227
228 #ifdef PNG_READ_pHYs_SUPPORTED
229 else if (chunk_name == png_pHYs)
230 png_handle_pHYs(png_ptr, info_ptr, length);
231 #endif
232
233 #ifdef PNG_READ_sBIT_SUPPORTED
234 else if (chunk_name == png_sBIT)
235 png_handle_sBIT(png_ptr, info_ptr, length);
236 #endif
237
238 #ifdef PNG_READ_sRGB_SUPPORTED
239 else if (chunk_name == png_sRGB)
240 png_handle_sRGB(png_ptr, info_ptr, length);
241 #endif
242
243 #ifdef PNG_READ_iCCP_SUPPORTED
244 else if (chunk_name == png_iCCP)
245 png_handle_iCCP(png_ptr, info_ptr, length);
246 #endif
247
248 #ifdef PNG_READ_sPLT_SUPPORTED
249 else if (chunk_name == png_sPLT)
250 png_handle_sPLT(png_ptr, info_ptr, length);
251 #endif
252
253 #ifdef PNG_READ_tEXt_SUPPORTED
254 else if (chunk_name == png_tEXt)
255 png_handle_tEXt(png_ptr, info_ptr, length);
256 #endif
257
258 #ifdef PNG_READ_tIME_SUPPORTED
259 else if (chunk_name == png_tIME)
260 png_handle_tIME(png_ptr, info_ptr, length);
261 #endif
262
263 #ifdef PNG_READ_tRNS_SUPPORTED
264 else if (chunk_name == png_tRNS)
265 png_handle_tRNS(png_ptr, info_ptr, length);
266 #endif
267
268 #ifdef PNG_READ_zTXt_SUPPORTED
269 else if (chunk_name == png_zTXt)
270 png_handle_zTXt(png_ptr, info_ptr, length);
271 #endif
272
273 #ifdef PNG_READ_iTXt_SUPPORTED
274 else if (chunk_name == png_iTXt)
275 png_handle_iTXt(png_ptr, info_ptr, length);
276 #endif
277
278 else
279 png_handle_unknown(png_ptr, info_ptr, length,
280 PNG_HANDLE_CHUNK_AS_DEFAULT);
281 }
282 }
283 #endif /* SEQUENTIAL_READ */
284
285 /* Optional call to update the users info_ptr structure */
286 void PNGAPI
287 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
288 {
289 png_debug(1, "in png_read_update_info");
290
291 if (png_ptr != NULL)
292 {
293 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
294 {
295 png_read_start_row(png_ptr);
296
297 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
298 png_read_transform_info(png_ptr, info_ptr);
299 # else
300 PNG_UNUSED(info_ptr)
301 # endif
302 }
303
304 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
305 else
306 png_app_error(png_ptr,
307 "png_read_update_info/png_start_read_image: duplicate call");
308 }
309 }
310
311 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
312 /* Initialize palette, background, etc, after transformations
313 * are set, but before any reading takes place. This allows
314 * the user to obtain a gamma-corrected palette, for example.
315 * If the user doesn't call this, we will do it ourselves.
316 */
317 void PNGAPI
318 png_start_read_image(png_structrp png_ptr)
319 {
320 png_debug(1, "in png_start_read_image");
321
322 if (png_ptr != NULL)
323 {
324 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
325 png_read_start_row(png_ptr);
326
327 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
328 else
329 png_app_error(png_ptr,
330 "png_start_read_image/png_read_update_info: duplicate call");
331 }
332 }
333 #endif /* SEQUENTIAL_READ */
334
335 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
336 #ifdef PNG_MNG_FEATURES_SUPPORTED
337 /* Undoes intrapixel differencing,
338 * NOTE: this is apparently only supported in the 'sequential' reader.
339 */
340 static void
341 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
342 {
343 png_debug(1, "in png_do_read_intrapixel");
344
345 if (
346 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
347 {
348 int bytes_per_pixel;
349 png_uint_32 row_width = row_info->width;
350
351 if (row_info->bit_depth == 8)
352 {
353 png_bytep rp;
354 png_uint_32 i;
355
356 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
357 bytes_per_pixel = 3;
358
359 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
360 bytes_per_pixel = 4;
361
362 else
363 return;
364
365 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
366 {
367 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
368 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
369 }
370 }
371 else if (row_info->bit_depth == 16)
372 {
373 png_bytep rp;
374 png_uint_32 i;
375
376 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
377 bytes_per_pixel = 6;
378
379 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
380 bytes_per_pixel = 8;
381
382 else
383 return;
384
385 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
386 {
387 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
388 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
389 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
390 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
391 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
392 *(rp ) = (png_byte)((red >> 8) & 0xff);
393 *(rp + 1) = (png_byte)(red & 0xff);
394 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
395 *(rp + 5) = (png_byte)(blue & 0xff);
396 }
397 }
398 }
399 }
400 #endif /* MNG_FEATURES */
401
402 void PNGAPI
403 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
404 {
405 png_row_info row_info;
406
407 if (png_ptr == NULL)
408 return;
409
410 png_debug2(1, "in png_read_row (row %lu, pass %d)",
411 (unsigned long)png_ptr->row_number, png_ptr->pass);
412
413 /* png_read_start_row sets the information (in particular iwidth) for this
414 * interlace pass.
415 */
416 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
417 png_read_start_row(png_ptr);
418
419 /* 1.5.6: row_info moved out of png_struct to a local here. */
420 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
421 row_info.color_type = png_ptr->color_type;
422 row_info.bit_depth = png_ptr->bit_depth;
423 row_info.channels = png_ptr->channels;
424 row_info.pixel_depth = png_ptr->pixel_depth;
425 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
426
427 #ifdef PNG_WARNINGS_SUPPORTED
428 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
429 {
430 /* Check for transforms that have been set but were defined out */
431 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
432 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
433 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
434 #endif
435
436 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
437 if ((png_ptr->transformations & PNG_FILLER) != 0)
438 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
439 #endif
440
441 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
442 !defined(PNG_READ_PACKSWAP_SUPPORTED)
443 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
444 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
445 #endif
446
447 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
448 if ((png_ptr->transformations & PNG_PACK) != 0)
449 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
450 #endif
451
452 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
453 if ((png_ptr->transformations & PNG_SHIFT) != 0)
454 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
455 #endif
456
457 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
458 if ((png_ptr->transformations & PNG_BGR) != 0)
459 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
460 #endif
461
462 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
463 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
464 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
465 #endif
466 }
467 #endif /* WARNINGS */
468
469 #ifdef PNG_READ_INTERLACING_SUPPORTED
470 /* If interlaced and we do not need a new row, combine row and return.
471 * Notice that the pixels we have from previous rows have been transformed
472 * already; we can only combine like with like (transformed or
473 * untransformed) and, because of the libpng API for interlaced images, this
474 * means we must transform before de-interlacing.
475 */
476 if (png_ptr->interlaced != 0 &&
477 (png_ptr->transformations & PNG_INTERLACE) != 0)
478 {
479 switch (png_ptr->pass)
480 {
481 case 0:
482 if (png_ptr->row_number & 0x07)
483 {
484 if (dsp_row != NULL)
485 png_combine_row(png_ptr, dsp_row, 1/*display*/);
486 png_read_finish_row(png_ptr);
487 return;
488 }
489 break;
490
491 case 1:
492 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
493 {
494 if (dsp_row != NULL)
495 png_combine_row(png_ptr, dsp_row, 1/*display*/);
496
497 png_read_finish_row(png_ptr);
498 return;
499 }
500 break;
501
502 case 2:
503 if ((png_ptr->row_number & 0x07) != 4)
504 {
505 if (dsp_row != NULL && (png_ptr->row_number & 4))
506 png_combine_row(png_ptr, dsp_row, 1/*display*/);
507
508 png_read_finish_row(png_ptr);
509 return;
510 }
511 break;
512
513 case 3:
514 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
515 {
516 if (dsp_row != NULL)
517 png_combine_row(png_ptr, dsp_row, 1/*display*/);
518
519 png_read_finish_row(png_ptr);
520 return;
521 }
522 break;
523
524 case 4:
525 if ((png_ptr->row_number & 3) != 2)
526 {
527 if (dsp_row != NULL && (png_ptr->row_number & 2))
528 png_combine_row(png_ptr, dsp_row, 1/*display*/);
529
530 png_read_finish_row(png_ptr);
531 return;
532 }
533 break;
534
535 case 5:
536 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
537 {
538 if (dsp_row != NULL)
539 png_combine_row(png_ptr, dsp_row, 1/*display*/);
540
541 png_read_finish_row(png_ptr);
542 return;
543 }
544 break;
545
546 default:
547 case 6:
548 if ((png_ptr->row_number & 1) == 0)
549 {
550 png_read_finish_row(png_ptr);
551 return;
552 }
553 break;
554 }
555 }
556 #endif
557
558 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
559 png_error(png_ptr, "Invalid attempt to read row data");
560
561 /* Fill the row with IDAT data: */
562 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
563
564 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
565 {
566 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
567 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
568 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
569 else
570 png_error(png_ptr, "bad adaptive filter value");
571 }
572
573 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
574 * 1.5.6, while the buffer really is this big in current versions of libpng
575 * it may not be in the future, so this was changed just to copy the
576 * interlaced count:
577 */
578 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
579
580 #ifdef PNG_MNG_FEATURES_SUPPORTED
581 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
582 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
583 {
584 /* Intrapixel differencing */
585 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
586 }
587 #endif
588
589 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
590 if (png_ptr->transformations)
591 png_do_read_transformations(png_ptr, &row_info);
592 #endif
593
594 /* The transformed pixel depth should match the depth now in row_info. */
595 if (png_ptr->transformed_pixel_depth == 0)
596 {
597 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
598 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
599 png_error(png_ptr, "sequential row overflow");
600 }
601
602 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
603 png_error(png_ptr, "internal sequential row size calculation error");
604
605 #ifdef PNG_READ_INTERLACING_SUPPORTED
606 /* Expand interlaced rows to full size */
607 if (png_ptr->interlaced != 0 &&
608 (png_ptr->transformations & PNG_INTERLACE) != 0)
609 {
610 if (png_ptr->pass < 6)
611 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
612 png_ptr->transformations);
613
614 if (dsp_row != NULL)
615 png_combine_row(png_ptr, dsp_row, 1/*display*/);
616
617 if (row != NULL)
618 png_combine_row(png_ptr, row, 0/*row*/);
619 }
620
621 else
622 #endif
623 {
624 if (row != NULL)
625 png_combine_row(png_ptr, row, -1/*ignored*/);
626
627 if (dsp_row != NULL)
628 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
629 }
630 png_read_finish_row(png_ptr);
631
632 if (png_ptr->read_row_fn != NULL)
633 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
634
635 }
636 #endif /* SEQUENTIAL_READ */
637
638 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
639 /* Read one or more rows of image data. If the image is interlaced,
640 * and png_set_interlace_handling() has been called, the rows need to
641 * contain the contents of the rows from the previous pass. If the
642 * image has alpha or transparency, and png_handle_alpha()[*] has been
643 * called, the rows contents must be initialized to the contents of the
644 * screen.
645 *
646 * "row" holds the actual image, and pixels are placed in it
647 * as they arrive. If the image is displayed after each pass, it will
648 * appear to "sparkle" in. "display_row" can be used to display a
649 * "chunky" progressive image, with finer detail added as it becomes
650 * available. If you do not want this "chunky" display, you may pass
651 * NULL for display_row. If you do not want the sparkle display, and
652 * you have not called png_handle_alpha(), you may pass NULL for rows.
653 * If you have called png_handle_alpha(), and the image has either an
654 * alpha channel or a transparency chunk, you must provide a buffer for
655 * rows. In this case, you do not have to provide a display_row buffer
656 * also, but you may. If the image is not interlaced, or if you have
657 * not called png_set_interlace_handling(), the display_row buffer will
658 * be ignored, so pass NULL to it.
659 *
660 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
661 */
662
663 void PNGAPI
664 png_read_rows(png_structrp png_ptr, png_bytepp row,
665 png_bytepp display_row, png_uint_32 num_rows)
666 {
667 png_uint_32 i;
668 png_bytepp rp;
669 png_bytepp dp;
670
671 png_debug(1, "in png_read_rows");
672
673 if (png_ptr == NULL)
674 return;
675
676 rp = row;
677 dp = display_row;
678 if (rp != NULL && dp != NULL)
679 for (i = 0; i < num_rows; i++)
680 {
681 png_bytep rptr = *rp++;
682 png_bytep dptr = *dp++;
683
684 png_read_row(png_ptr, rptr, dptr);
685 }
686
687 else if (rp != NULL)
688 for (i = 0; i < num_rows; i++)
689 {
690 png_bytep rptr = *rp;
691 png_read_row(png_ptr, rptr, NULL);
692 rp++;
693 }
694
695 else if (dp != NULL)
696 for (i = 0; i < num_rows; i++)
697 {
698 png_bytep dptr = *dp;
699 png_read_row(png_ptr, NULL, dptr);
700 dp++;
701 }
702 }
703 #endif /* SEQUENTIAL_READ */
704
705 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
706 /* Read the entire image. If the image has an alpha channel or a tRNS
707 * chunk, and you have called png_handle_alpha()[*], you will need to
708 * initialize the image to the current image that PNG will be overlaying.
709 * We set the num_rows again here, in case it was incorrectly set in
710 * png_read_start_row() by a call to png_read_update_info() or
711 * png_start_read_image() if png_set_interlace_handling() wasn't called
712 * prior to either of these functions like it should have been. You can
713 * only call this function once. If you desire to have an image for
714 * each pass of a interlaced image, use png_read_rows() instead.
715 *
716 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
717 */
718 void PNGAPI
719 png_read_image(png_structrp png_ptr, png_bytepp image)
720 {
721 png_uint_32 i, image_height;
722 int pass, j;
723 png_bytepp rp;
724
725 png_debug(1, "in png_read_image");
726
727 if (png_ptr == NULL)
728 return;
729
730 #ifdef PNG_READ_INTERLACING_SUPPORTED
731 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
732 {
733 pass = png_set_interlace_handling(png_ptr);
734 /* And make sure transforms are initialized. */
735 png_start_read_image(png_ptr);
736 }
737 else
738 {
739 if (png_ptr->interlaced != 0 &&
740 (png_ptr->transformations & PNG_INTERLACE) == 0)
741 {
742 /* Caller called png_start_read_image or png_read_update_info without
743 * first turning on the PNG_INTERLACE transform. We can fix this here,
744 * but the caller should do it!
745 */
746 png_warning(png_ptr, "Interlace handling should be turned on when "
747 "using png_read_image");
748 /* Make sure this is set correctly */
749 png_ptr->num_rows = png_ptr->height;
750 }
751
752 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
753 * the above error case.
754 */
755 pass = png_set_interlace_handling(png_ptr);
756 }
757 #else
758 if (png_ptr->interlaced)
759 png_error(png_ptr,
760 "Cannot read interlaced image -- interlace handler disabled");
761
762 pass = 1;
763 #endif
764
765 image_height=png_ptr->height;
766
767 for (j = 0; j < pass; j++)
768 {
769 rp = image;
770 for (i = 0; i < image_height; i++)
771 {
772 png_read_row(png_ptr, *rp, NULL);
773 rp++;
774 }
775 }
776 }
777 #endif /* SEQUENTIAL_READ */
778
779 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
780 /* Read the end of the PNG file. Will not read past the end of the
781 * file, will verify the end is accurate, and will read any comments
782 * or time information at the end of the file, if info is not NULL.
783 */
784 void PNGAPI
785 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
786 {
787 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
788 int keep;
789 #endif
790
791 png_debug(1, "in png_read_end");
792
793 if (png_ptr == NULL)
794 return;
795
796 /* If png_read_end is called in the middle of reading the rows there may
797 * still be pending IDAT data and an owned zstream. Deal with this here.
798 */
799 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
800 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
801 #endif
802 png_read_finish_IDAT(png_ptr);
803
804 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
805 /* Report invalid palette index; added at libng-1.5.10 */
806 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
807 png_ptr->num_palette_max > png_ptr->num_palette)
808 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
809 #endif
810
811 do
812 {
813 png_uint_32 length = png_read_chunk_header(png_ptr);
814 png_uint_32 chunk_name = png_ptr->chunk_name;
815
816 if (chunk_name == png_IEND)
817 png_handle_IEND(png_ptr, info_ptr, length);
818
819 else if (chunk_name == png_IHDR)
820 png_handle_IHDR(png_ptr, info_ptr, length);
821
822 else if (info_ptr == NULL)
823 png_crc_finish(png_ptr, length);
824
825 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
826 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
827 {
828 if (chunk_name == png_IDAT)
829 {
830 if ((length > 0) ||
831 (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
832 png_benign_error(png_ptr, "Too many IDATs found");
833 }
834 png_handle_unknown(png_ptr, info_ptr, length, keep);
835 if (chunk_name == png_PLTE)
836 png_ptr->mode |= PNG_HAVE_PLTE;
837 }
838 #endif
839
840 else if (chunk_name == png_IDAT)
841 {
842 /* Zero length IDATs are legal after the last IDAT has been
843 * read, but not after other chunks have been read.
844 */
845 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
846 png_benign_error(png_ptr, "Too many IDATs found");
847
848 png_crc_finish(png_ptr, length);
849 }
850 else if (chunk_name == png_PLTE)
851 png_handle_PLTE(png_ptr, info_ptr, length);
852
853 #ifdef PNG_READ_bKGD_SUPPORTED
854 else if (chunk_name == png_bKGD)
855 png_handle_bKGD(png_ptr, info_ptr, length);
856 #endif
857
858 #ifdef PNG_READ_cHRM_SUPPORTED
859 else if (chunk_name == png_cHRM)
860 png_handle_cHRM(png_ptr, info_ptr, length);
861 #endif
862
863 #ifdef PNG_READ_gAMA_SUPPORTED
864 else if (chunk_name == png_gAMA)
865 png_handle_gAMA(png_ptr, info_ptr, length);
866 #endif
867
868 #ifdef PNG_READ_hIST_SUPPORTED
869 else if (chunk_name == png_hIST)
870 png_handle_hIST(png_ptr, info_ptr, length);
871 #endif
872
873 #ifdef PNG_READ_oFFs_SUPPORTED
874 else if (chunk_name == png_oFFs)
875 png_handle_oFFs(png_ptr, info_ptr, length);
876 #endif
877
878 #ifdef PNG_READ_pCAL_SUPPORTED
879 else if (chunk_name == png_pCAL)
880 png_handle_pCAL(png_ptr, info_ptr, length);
881 #endif
882
883 #ifdef PNG_READ_sCAL_SUPPORTED
884 else if (chunk_name == png_sCAL)
885 png_handle_sCAL(png_ptr, info_ptr, length);
886 #endif
887
888 #ifdef PNG_READ_pHYs_SUPPORTED
889 else if (chunk_name == png_pHYs)
890 png_handle_pHYs(png_ptr, info_ptr, length);
891 #endif
892
893 #ifdef PNG_READ_sBIT_SUPPORTED
894 else if (chunk_name == png_sBIT)
895 png_handle_sBIT(png_ptr, info_ptr, length);
896 #endif
897
898 #ifdef PNG_READ_sRGB_SUPPORTED
899 else if (chunk_name == png_sRGB)
900 png_handle_sRGB(png_ptr, info_ptr, length);
901 #endif
902
903 #ifdef PNG_READ_iCCP_SUPPORTED
904 else if (chunk_name == png_iCCP)
905 png_handle_iCCP(png_ptr, info_ptr, length);
906 #endif
907
908 #ifdef PNG_READ_sPLT_SUPPORTED
909 else if (chunk_name == png_sPLT)
910 png_handle_sPLT(png_ptr, info_ptr, length);
911 #endif
912
913 #ifdef PNG_READ_tEXt_SUPPORTED
914 else if (chunk_name == png_tEXt)
915 png_handle_tEXt(png_ptr, info_ptr, length);
916 #endif
917
918 #ifdef PNG_READ_tIME_SUPPORTED
919 else if (chunk_name == png_tIME)
920 png_handle_tIME(png_ptr, info_ptr, length);
921 #endif
922
923 #ifdef PNG_READ_tRNS_SUPPORTED
924 else if (chunk_name == png_tRNS)
925 png_handle_tRNS(png_ptr, info_ptr, length);
926 #endif
927
928 #ifdef PNG_READ_zTXt_SUPPORTED
929 else if (chunk_name == png_zTXt)
930 png_handle_zTXt(png_ptr, info_ptr, length);
931 #endif
932
933 #ifdef PNG_READ_iTXt_SUPPORTED
934 else if (chunk_name == png_iTXt)
935 png_handle_iTXt(png_ptr, info_ptr, length);
936 #endif
937
938 else
939 png_handle_unknown(png_ptr, info_ptr, length,
940 PNG_HANDLE_CHUNK_AS_DEFAULT);
941 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
942 }
943 #endif /* SEQUENTIAL_READ */
944
945 /* Free all memory used in the read struct */
946 static void
947 png_read_destroy(png_structrp png_ptr)
948 {
949 png_debug(1, "in png_read_destroy");
950
951 #ifdef PNG_READ_GAMMA_SUPPORTED
952 png_destroy_gamma_table(png_ptr);
953 #endif
954
955 png_free(png_ptr, png_ptr->big_row_buf);
956 png_ptr->big_row_buf = NULL;
957 png_free(png_ptr, png_ptr->big_prev_row);
958 png_ptr->big_prev_row = NULL;
959 png_free(png_ptr, png_ptr->read_buffer);
960 png_ptr->read_buffer = NULL;
961
962 #ifdef PNG_READ_QUANTIZE_SUPPORTED
963 png_free(png_ptr, png_ptr->palette_lookup);
964 png_ptr->palette_lookup = NULL;
965 png_free(png_ptr, png_ptr->quantize_index);
966 png_ptr->quantize_index = NULL;
967 #endif
968
969 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
970 {
971 png_zfree(png_ptr, png_ptr->palette);
972 png_ptr->palette = NULL;
973 }
974 png_ptr->free_me &= ~PNG_FREE_PLTE;
975
976 #if defined(PNG_tRNS_SUPPORTED) || \
977 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
978 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
979 {
980 png_free(png_ptr, png_ptr->trans_alpha);
981 png_ptr->trans_alpha = NULL;
982 }
983 png_ptr->free_me &= ~PNG_FREE_TRNS;
984 #endif
985
986 inflateEnd(&png_ptr->zstream);
987
988 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
989 png_free(png_ptr, png_ptr->save_buffer);
990 png_ptr->save_buffer = NULL;
991 #endif
992
993 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
994 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
995 png_free(png_ptr, png_ptr->unknown_chunk.data);
996 png_ptr->unknown_chunk.data = NULL;
997 #endif
998
999 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
1000 png_free(png_ptr, png_ptr->chunk_list);
1001 png_ptr->chunk_list = NULL;
1002 #endif
1003
1004 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1005 * callbacks are still set at this point. They are required to complete the
1006 * destruction of the png_struct itself.
1007 */
1008 }
1009
1010 /* Free all memory used by the read */
1011 void PNGAPI
1012 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1013 png_infopp end_info_ptr_ptr)
1014 {
1015 png_structrp png_ptr = NULL;
1016
1017 png_debug(1, "in png_destroy_read_struct");
1018
1019 if (png_ptr_ptr != NULL)
1020 png_ptr = *png_ptr_ptr;
1021
1022 if (png_ptr == NULL)
1023 return;
1024
1025 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1026 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1027 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1028 */
1029 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1030 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1031
1032 *png_ptr_ptr = NULL;
1033 png_read_destroy(png_ptr);
1034 png_destroy_png_struct(png_ptr);
1035 }
1036
1037 void PNGAPI
1038 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1039 {
1040 if (png_ptr == NULL)
1041 return;
1042
1043 png_ptr->read_row_fn = read_row_fn;
1044 }
1045
1046
1047 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1048 #ifdef PNG_INFO_IMAGE_SUPPORTED
1049 void PNGAPI
1050 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1051 int transforms,
1052 voidp params)
1053 {
1054 if (png_ptr == NULL || info_ptr == NULL)
1055 return;
1056
1057 /* png_read_info() gives us all of the information from the
1058 * PNG file before the first IDAT (image data chunk).
1059 */
1060 png_read_info(png_ptr, info_ptr);
1061 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1062 png_error(png_ptr, "Image is too high to process with png_read_png()");
1063
1064 /* -------------- image transformations start here ------------------- */
1065 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1066 * is not implemented. This will only happen in de-configured (non-default)
1067 * libpng builds. The results can be unexpected - png_read_png may return
1068 * short or mal-formed rows because the transform is skipped.
1069 */
1070
1071 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1072 */
1073 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1074 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1075 * did in earlier versions, while "scale_16" is now more accurate.
1076 */
1077 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1078 png_set_scale_16(png_ptr);
1079 #else
1080 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1081 #endif
1082
1083 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1084 * latter by doing SCALE first. This is ok and allows apps not to check for
1085 * which is supported to get the right answer.
1086 */
1087 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1088 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1089 png_set_strip_16(png_ptr);
1090 #else
1091 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1092 #endif
1093
1094 /* Strip alpha bytes from the input data without combining with
1095 * the background (not recommended).
1096 */
1097 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1098 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1099 png_set_strip_alpha(png_ptr);
1100 #else
1101 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1102 #endif
1103
1104 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1105 * byte into separate bytes (useful for paletted and grayscale images).
1106 */
1107 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1108 #ifdef PNG_READ_PACK_SUPPORTED
1109 png_set_packing(png_ptr);
1110 #else
1111 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1112 #endif
1113
1114 /* Change the order of packed pixels to least significant bit first
1115 * (not useful if you are using png_set_packing).
1116 */
1117 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1118 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1119 png_set_packswap(png_ptr);
1120 #else
1121 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1122 #endif
1123
1124 /* Expand paletted colors into true RGB triplets
1125 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1126 * Expand paletted or RGB images with transparency to full alpha
1127 * channels so the data will be available as RGBA quartets.
1128 */
1129 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1130 #ifdef PNG_READ_EXPAND_SUPPORTED
1131 png_set_expand(png_ptr);
1132 #else
1133 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1134 #endif
1135
1136 /* We don't handle background color or gamma transformation or quantizing.
1137 */
1138
1139 /* Invert monochrome files to have 0 as white and 1 as black
1140 */
1141 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1142 #ifdef PNG_READ_INVERT_SUPPORTED
1143 png_set_invert_mono(png_ptr);
1144 #else
1145 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1146 #endif
1147
1148 /* If you want to shift the pixel values from the range [0,255] or
1149 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1150 * colors were originally in:
1151 */
1152 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1153 #ifdef PNG_READ_SHIFT_SUPPORTED
1154 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1155 png_set_shift(png_ptr, &info_ptr->sig_bit);
1156 #else
1157 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1158 #endif
1159
1160 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1161 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1162 #ifdef PNG_READ_BGR_SUPPORTED
1163 png_set_bgr(png_ptr);
1164 #else
1165 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1166 #endif
1167
1168 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1169 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1170 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1171 png_set_swap_alpha(png_ptr);
1172 #else
1173 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1174 #endif
1175
1176 /* Swap bytes of 16-bit files to least significant byte first */
1177 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1178 #ifdef PNG_READ_SWAP_SUPPORTED
1179 png_set_swap(png_ptr);
1180 #else
1181 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1182 #endif
1183
1184 /* Added at libpng-1.2.41 */
1185 /* Invert the alpha channel from opacity to transparency */
1186 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1187 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1188 png_set_invert_alpha(png_ptr);
1189 #else
1190 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1191 #endif
1192
1193 /* Added at libpng-1.2.41 */
1194 /* Expand grayscale image to RGB */
1195 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1196 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1197 png_set_gray_to_rgb(png_ptr);
1198 #else
1199 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1200 #endif
1201
1202 /* Added at libpng-1.5.4 */
1203 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1204 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1205 png_set_expand_16(png_ptr);
1206 #else
1207 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1208 #endif
1209
1210 /* We don't handle adding filler bytes */
1211
1212 /* We use png_read_image and rely on that for interlace handling, but we also
1213 * call png_read_update_info therefore must turn on interlace handling now:
1214 */
1215 (void)png_set_interlace_handling(png_ptr);
1216
1217 /* Optional call to gamma correct and add the background to the palette
1218 * and update info structure. REQUIRED if you are expecting libpng to
1219 * update the palette for you (i.e., you selected such a transform above).
1220 */
1221 png_read_update_info(png_ptr, info_ptr);
1222
1223 /* -------------- image transformations end here ------------------- */
1224
1225 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1226 if (info_ptr->row_pointers == NULL)
1227 {
1228 png_uint_32 iptr;
1229
1230 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1231 info_ptr->height * (sizeof (png_bytep))));
1232
1233 for (iptr=0; iptr<info_ptr->height; iptr++)
1234 info_ptr->row_pointers[iptr] = NULL;
1235
1236 info_ptr->free_me |= PNG_FREE_ROWS;
1237
1238 for (iptr = 0; iptr < info_ptr->height; iptr++)
1239 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1240 png_malloc(png_ptr, info_ptr->rowbytes));
1241 }
1242
1243 png_read_image(png_ptr, info_ptr->row_pointers);
1244 info_ptr->valid |= PNG_INFO_IDAT;
1245
1246 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1247 png_read_end(png_ptr, info_ptr);
1248
1249 PNG_UNUSED(params)
1250 }
1251 #endif /* INFO_IMAGE */
1252 #endif /* SEQUENTIAL_READ */
1253
1254 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1255 /* SIMPLIFIED READ
1256 *
1257 * This code currently relies on the sequential reader, though it could easily
1258 * be made to work with the progressive one.
1259 */
1260 /* Arguments to png_image_finish_read: */
1261
1262 /* Encoding of PNG data (used by the color-map code) */
1263 # define P_NOTSET 0 /* File encoding not yet known */
1264 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1265 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1266 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1267 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1268
1269 /* Color-map processing: after libpng has run on the PNG image further
1270 * processing may be needed to convert the data to color-map indices.
1271 */
1272 #define PNG_CMAP_NONE 0
1273 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1274 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1275 #define PNG_CMAP_RGB 3 /* Process RGB data */
1276 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1277
1278 /* The following document where the background is for each processing case. */
1279 #define PNG_CMAP_NONE_BACKGROUND 256
1280 #define PNG_CMAP_GA_BACKGROUND 231
1281 #define PNG_CMAP_TRANS_BACKGROUND 254
1282 #define PNG_CMAP_RGB_BACKGROUND 256
1283 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1284
1285 typedef struct
1286 {
1287 /* Arguments: */
1288 png_imagep image;
1289 png_voidp buffer;
1290 png_int_32 row_stride;
1291 png_voidp colormap;
1292 png_const_colorp background;
1293 /* Local variables: */
1294 png_voidp local_row;
1295 png_voidp first_row;
1296 ptrdiff_t row_bytes; /* step between rows */
1297 int file_encoding; /* E_ values above */
1298 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1299 int colormap_processing; /* PNG_CMAP_ values above */
1300 } png_image_read_control;
1301
1302 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1303 * called, so setting up the jmp_buf is not required. This means that anything
1304 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1305 * instead so that control is returned safely back to this routine.
1306 */
1307 static int
1308 png_image_read_init(png_imagep image)
1309 {
1310 if (image->opaque == NULL)
1311 {
1312 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1313 png_safe_error, png_safe_warning);
1314
1315 /* And set the rest of the structure to NULL to ensure that the various
1316 * fields are consistent.
1317 */
1318 memset(image, 0, (sizeof *image));
1319 image->version = PNG_IMAGE_VERSION;
1320
1321 if (png_ptr != NULL)
1322 {
1323 png_infop info_ptr = png_create_info_struct(png_ptr);
1324
1325 if (info_ptr != NULL)
1326 {
1327 png_controlp control = png_voidcast(png_controlp,
1328 png_malloc_warn(png_ptr, (sizeof *control)));
1329
1330 if (control != NULL)
1331 {
1332 memset(control, 0, (sizeof *control));
1333
1334 control->png_ptr = png_ptr;
1335 control->info_ptr = info_ptr;
1336 control->for_write = 0;
1337
1338 image->opaque = control;
1339 return 1;
1340 }
1341
1342 /* Error clean up */
1343 png_destroy_info_struct(png_ptr, &info_ptr);
1344 }
1345
1346 png_destroy_read_struct(&png_ptr, NULL, NULL);
1347 }
1348
1349 return png_image_error(image, "png_image_read: out of memory");
1350 }
1351
1352 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1353 }
1354
1355 /* Utility to find the base format of a PNG file from a png_struct. */
1356 static png_uint_32
1357 png_image_format(png_structrp png_ptr)
1358 {
1359 png_uint_32 format = 0;
1360
1361 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1362 format |= PNG_FORMAT_FLAG_COLOR;
1363
1364 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1365 format |= PNG_FORMAT_FLAG_ALPHA;
1366
1367 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1368 * sets the png_struct fields; that's all we are interested in here. The
1369 * precise interaction with an app call to png_set_tRNS and PNG file reading
1370 * is unclear.
1371 */
1372 else if (png_ptr->num_trans > 0)
1373 format |= PNG_FORMAT_FLAG_ALPHA;
1374
1375 if (png_ptr->bit_depth == 16)
1376 format |= PNG_FORMAT_FLAG_LINEAR;
1377
1378 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1379 format |= PNG_FORMAT_FLAG_COLORMAP;
1380
1381 return format;
1382 }
1383
1384 /* Is the given gamma significantly different from sRGB? The test is the same
1385 * one used in pngrtran.c when deciding whether to do gamma correction. The
1386 * arithmetic optimizes the division by using the fact that the inverse of the
1387 * file sRGB gamma is 2.2
1388 */
1389 static int
1390 png_gamma_not_sRGB(png_fixed_point g)
1391 {
1392 if (g < PNG_FP_1)
1393 {
1394 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1395 if (g == 0)
1396 return 0;
1397
1398 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1399 }
1400
1401 return 1;
1402 }
1403
1404 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1405 * header and fill in all the information. This is executed in a safe context,
1406 * unlike the init routine above.
1407 */
1408 static int
1409 png_image_read_header(png_voidp argument)
1410 {
1411 png_imagep image = png_voidcast(png_imagep, argument);
1412 png_structrp png_ptr = image->opaque->png_ptr;
1413 png_inforp info_ptr = image->opaque->info_ptr;
1414
1415 png_set_benign_errors(png_ptr, 1/*warn*/);
1416 png_read_info(png_ptr, info_ptr);
1417
1418 /* Do this the fast way; just read directly out of png_struct. */
1419 image->width = png_ptr->width;
1420 image->height = png_ptr->height;
1421
1422 {
1423 png_uint_32 format = png_image_format(png_ptr);
1424
1425 image->format = format;
1426
1427 #ifdef PNG_COLORSPACE_SUPPORTED
1428 /* Does the colorspace match sRGB? If there is no color endpoint
1429 * (colorant) information assume yes, otherwise require the
1430 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1431 * colorspace has been determined to be invalid ignore it.
1432 */
1433 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1434 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1435 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1436 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1437 #endif
1438 }
1439
1440 /* We need the maximum number of entries regardless of the format the
1441 * application sets here.
1442 */
1443 {
1444 png_uint_32 cmap_entries;
1445
1446 switch (png_ptr->color_type)
1447 {
1448 case PNG_COLOR_TYPE_GRAY:
1449 cmap_entries = 1U << png_ptr->bit_depth;
1450 break;
1451
1452 case PNG_COLOR_TYPE_PALETTE:
1453 cmap_entries = png_ptr->num_palette;
1454 break;
1455
1456 default:
1457 cmap_entries = 256;
1458 break;
1459 }
1460
1461 if (cmap_entries > 256)
1462 cmap_entries = 256;
1463
1464 image->colormap_entries = cmap_entries;
1465 }
1466
1467 return 1;
1468 }
1469
1470 #ifdef PNG_STDIO_SUPPORTED
1471 int PNGAPI
1472 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1473 {
1474 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1475 {
1476 if (file != NULL)
1477 {
1478 if (png_image_read_init(image) != 0)
1479 {
1480 /* This is slightly evil, but png_init_io doesn't do anything other
1481 * than this and we haven't changed the standard IO functions so
1482 * this saves a 'safe' function.
1483 */
1484 image->opaque->png_ptr->io_ptr = file;
1485 return png_safe_execute(image, png_image_read_header, image);
1486 }
1487 }
1488
1489 else
1490 return png_image_error(image,
1491 "png_image_begin_read_from_stdio: invalid argument");
1492 }
1493
1494 else if (image != NULL)
1495 return png_image_error(image,
1496 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1497
1498 return 0;
1499 }
1500
1501 int PNGAPI
1502 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1503 {
1504 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1505 {
1506 if (file_name != NULL)
1507 {
1508 FILE *fp = fopen(file_name, "rb");
1509
1510 if (fp != NULL)
1511 {
1512 if (png_image_read_init(image) != 0)
1513 {
1514 image->opaque->png_ptr->io_ptr = fp;
1515 image->opaque->owned_file = 1;
1516 return png_safe_execute(image, png_image_read_header, image);
1517 }
1518
1519 /* Clean up: just the opened file. */
1520 (void)fclose(fp);
1521 }
1522
1523 else
1524 return png_image_error(image, strerror(errno));
1525 }
1526
1527 else
1528 return png_image_error(image,
1529 "png_image_begin_read_from_file: invalid argument");
1530 }
1531
1532 else if (image != NULL)
1533 return png_image_error(image,
1534 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1535
1536 return 0;
1537 }
1538 #endif /* STDIO */
1539
1540 static void PNGCBAPI
1541 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1542 {
1543 if (png_ptr != NULL)
1544 {
1545 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1546 if (image != NULL)
1547 {
1548 png_controlp cp = image->opaque;
1549 if (cp != NULL)
1550 {
1551 png_const_bytep memory = cp->memory;
1552 png_size_t size = cp->size;
1553
1554 if (memory != NULL && size >= need)
1555 {
1556 memcpy(out, memory, need);
1557 cp->memory = memory + need;
1558 cp->size = size - need;
1559 return;
1560 }
1561
1562 png_error(png_ptr, "read beyond end of data");
1563 }
1564 }
1565
1566 png_error(png_ptr, "invalid memory read");
1567 }
1568 }
1569
1570 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1571 png_const_voidp memory, png_size_t size)
1572 {
1573 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1574 {
1575 if (memory != NULL && size > 0)
1576 {
1577 if (png_image_read_init(image) != 0)
1578 {
1579 /* Now set the IO functions to read from the memory buffer and
1580 * store it into io_ptr. Again do this in-place to avoid calling a
1581 * libpng function that requires error handling.
1582 */
1583 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1584 image->opaque->size = size;
1585 image->opaque->png_ptr->io_ptr = image;
1586 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1587
1588 return png_safe_execute(image, png_image_read_header, image);
1589 }
1590 }
1591
1592 else
1593 return png_image_error(image,
1594 "png_image_begin_read_from_memory: invalid argument");
1595 }
1596
1597 else if (image != NULL)
1598 return png_image_error(image,
1599 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1600
1601 return 0;
1602 }
1603
1604 /* Utility function to skip chunks that are not used by the simplified image
1605 * read functions and an appropriate macro to call it.
1606 */
1607 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1608 static void
1609 png_image_skip_unused_chunks(png_structrp png_ptr)
1610 {
1611 /* Prepare the reader to ignore all recognized chunks whose data will not
1612 * be used, i.e., all chunks recognized by libpng except for those
1613 * involved in basic image reading:
1614 *
1615 * IHDR, PLTE, IDAT, IEND
1616 *
1617 * Or image data handling:
1618 *
1619 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1620 *
1621 * This provides a small performance improvement and eliminates any
1622 * potential vulnerability to security problems in the unused chunks.
1623 *
1624 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1625 * too. This allows the simplified API to be compiled without iCCP support,
1626 * however if the support is there the chunk is still checked to detect
1627 * errors (which are unfortunately quite common.)
1628 */
1629 {
1630 static PNG_CONST png_byte chunks_to_process[] = {
1631 98, 75, 71, 68, '\0', /* bKGD */
1632 99, 72, 82, 77, '\0', /* cHRM */
1633 103, 65, 77, 65, '\0', /* gAMA */
1634 # ifdef PNG_READ_iCCP_SUPPORTED
1635 105, 67, 67, 80, '\0', /* iCCP */
1636 # endif
1637 115, 66, 73, 84, '\0', /* sBIT */
1638 115, 82, 71, 66, '\0', /* sRGB */
1639 };
1640
1641 /* Ignore unknown chunks and all other chunks except for the
1642 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1643 */
1644 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1645 NULL, -1);
1646
1647 /* But do not ignore image data handling chunks */
1648 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1649 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1650 }
1651 }
1652
1653 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1654 #else
1655 # define PNG_SKIP_CHUNKS(p) ((void)0)
1656 #endif /* HANDLE_AS_UNKNOWN */
1657
1658 /* The following macro gives the exact rounded answer for all values in the
1659 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1660 * the correct numbers 0..5
1661 */
1662 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1663
1664 /* Utility functions to make particular color-maps */
1665 static void
1666 set_file_encoding(png_image_read_control *display)
1667 {
1668 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1669 if (png_gamma_significant(g) != 0)
1670 {
1671 if (png_gamma_not_sRGB(g) != 0)
1672 {
1673 display->file_encoding = P_FILE;
1674 display->gamma_to_linear = png_reciprocal(g);
1675 }
1676
1677 else
1678 display->file_encoding = P_sRGB;
1679 }
1680
1681 else
1682 display->file_encoding = P_LINEAR8;
1683 }
1684
1685 static unsigned int
1686 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1687 {
1688 if (encoding == P_FILE) /* double check */
1689 encoding = display->file_encoding;
1690
1691 if (encoding == P_NOTSET) /* must be the file encoding */
1692 {
1693 set_file_encoding(display);
1694 encoding = display->file_encoding;
1695 }
1696
1697 switch (encoding)
1698 {
1699 case P_FILE:
1700 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1701 break;
1702
1703 case P_sRGB:
1704 value = png_sRGB_table[value];
1705 break;
1706
1707 case P_LINEAR:
1708 break;
1709
1710 case P_LINEAR8:
1711 value *= 257;
1712 break;
1713
1714 #ifdef __GNUC__
1715 default:
1716 png_error(display->image->opaque->png_ptr,
1717 "unexpected encoding (internal error)");
1718 #endif
1719 }
1720
1721 return value;
1722 }
1723
1724 static png_uint_32
1725 png_colormap_compose(png_image_read_control *display,
1726 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1727 png_uint_32 background, int encoding)
1728 {
1729 /* The file value is composed on the background, the background has the given
1730 * encoding and so does the result, the file is encoded with P_FILE and the
1731 * file and alpha are 8-bit values. The (output) encoding will always be
1732 * P_LINEAR or P_sRGB.
1733 */
1734 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1735 png_uint_32 b = decode_gamma(display, background, encoding);
1736
1737 /* The alpha is always an 8-bit value (it comes from the palette), the value
1738 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1739 */
1740 f = f * alpha + b * (255-alpha);
1741
1742 if (encoding == P_LINEAR)
1743 {
1744 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1745 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1746 */
1747 f *= 257; /* Now scaled by 65535 */
1748 f += f >> 16;
1749 f = (f+32768) >> 16;
1750 }
1751
1752 else /* P_sRGB */
1753 f = PNG_sRGB_FROM_LINEAR(f);
1754
1755 return f;
1756 }
1757
1758 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1759 * be 8-bit.
1760 */
1761 static void
1762 png_create_colormap_entry(png_image_read_control *display,
1763 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1764 png_uint_32 alpha, int encoding)
1765 {
1766 png_imagep image = display->image;
1767 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1768 P_LINEAR : P_sRGB;
1769 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1770 (red != green || green != blue);
1771
1772 if (ip > 255)
1773 png_error(image->opaque->png_ptr, "color-map index out of range");
1774
1775 /* Update the cache with whether the file gamma is significantly different
1776 * from sRGB.
1777 */
1778 if (encoding == P_FILE)
1779 {
1780 if (display->file_encoding == P_NOTSET)
1781 set_file_encoding(display);
1782
1783 /* Note that the cached value may be P_FILE too, but if it is then the
1784 * gamma_to_linear member has been set.
1785 */
1786 encoding = display->file_encoding;
1787 }
1788
1789 if (encoding == P_FILE)
1790 {
1791 png_fixed_point g = display->gamma_to_linear;
1792
1793 red = png_gamma_16bit_correct(red*257, g);
1794 green = png_gamma_16bit_correct(green*257, g);
1795 blue = png_gamma_16bit_correct(blue*257, g);
1796
1797 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1798 {
1799 alpha *= 257;
1800 encoding = P_LINEAR;
1801 }
1802
1803 else
1804 {
1805 red = PNG_sRGB_FROM_LINEAR(red * 255);
1806 green = PNG_sRGB_FROM_LINEAR(green * 255);
1807 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1808 encoding = P_sRGB;
1809 }
1810 }
1811
1812 else if (encoding == P_LINEAR8)
1813 {
1814 /* This encoding occurs quite frequently in test cases because PngSuite
1815 * includes a gAMA 1.0 chunk with most images.
1816 */
1817 red *= 257;
1818 green *= 257;
1819 blue *= 257;
1820 alpha *= 257;
1821 encoding = P_LINEAR;
1822 }
1823
1824 else if (encoding == P_sRGB &&
1825 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1826 {
1827 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1828 * linear.
1829 */
1830 red = png_sRGB_table[red];
1831 green = png_sRGB_table[green];
1832 blue = png_sRGB_table[blue];
1833 alpha *= 257;
1834 encoding = P_LINEAR;
1835 }
1836
1837 /* This is set if the color isn't gray but the output is. */
1838 if (encoding == P_LINEAR)
1839 {
1840 if (convert_to_Y != 0)
1841 {
1842 /* NOTE: these values are copied from png_do_rgb_to_gray */
1843 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1844 (png_uint_32)2366 * blue;
1845
1846 if (output_encoding == P_LINEAR)
1847 y = (y + 16384) >> 15;
1848
1849 else
1850 {
1851 /* y is scaled by 32768, we need it scaled by 255: */
1852 y = (y + 128) >> 8;
1853 y *= 255;
1854 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1855 alpha = PNG_DIV257(alpha);
1856 encoding = P_sRGB;
1857 }
1858
1859 blue = red = green = y;
1860 }
1861
1862 else if (output_encoding == P_sRGB)
1863 {
1864 red = PNG_sRGB_FROM_LINEAR(red * 255);
1865 green = PNG_sRGB_FROM_LINEAR(green * 255);
1866 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1867 alpha = PNG_DIV257(alpha);
1868 encoding = P_sRGB;
1869 }
1870 }
1871
1872 if (encoding != output_encoding)
1873 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1874
1875 /* Store the value. */
1876 {
1877 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1878 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1879 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1880 # else
1881 # define afirst 0
1882 # endif
1883 # ifdef PNG_FORMAT_BGR_SUPPORTED
1884 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1885 # else
1886 # define bgr 0
1887 # endif
1888
1889 if (output_encoding == P_LINEAR)
1890 {
1891 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1892
1893 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1894
1895 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1896 * value, if less than 65535 (this is, effectively, composite on black
1897 * if the alpha channel is removed.)
1898 */
1899 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1900 {
1901 case 4:
1902 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1903 /* FALL THROUGH */
1904
1905 case 3:
1906 if (alpha < 65535)
1907 {
1908 if (alpha > 0)
1909 {
1910 blue = (blue * alpha + 32767U)/65535U;
1911 green = (green * alpha + 32767U)/65535U;
1912 red = (red * alpha + 32767U)/65535U;
1913 }
1914
1915 else
1916 red = green = blue = 0;
1917 }
1918 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1919 entry[afirst + 1] = (png_uint_16)green;
1920 entry[afirst + bgr] = (png_uint_16)red;
1921 break;
1922
1923 case 2:
1924 entry[1 ^ afirst] = (png_uint_16)alpha;
1925 /* FALL THROUGH */
1926
1927 case 1:
1928 if (alpha < 65535)
1929 {
1930 if (alpha > 0)
1931 green = (green * alpha + 32767U)/65535U;
1932
1933 else
1934 green = 0;
1935 }
1936 entry[afirst] = (png_uint_16)green;
1937 break;
1938
1939 default:
1940 break;
1941 }
1942 }
1943
1944 else /* output encoding is P_sRGB */
1945 {
1946 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1947
1948 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1949
1950 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1951 {
1952 case 4:
1953 entry[afirst ? 0 : 3] = (png_byte)alpha;
1954 case 3:
1955 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1956 entry[afirst + 1] = (png_byte)green;
1957 entry[afirst + bgr] = (png_byte)red;
1958 break;
1959
1960 case 2:
1961 entry[1 ^ afirst] = (png_byte)alpha;
1962 case 1:
1963 entry[afirst] = (png_byte)green;
1964 break;
1965
1966 default:
1967 break;
1968 }
1969 }
1970
1971 # ifdef afirst
1972 # undef afirst
1973 # endif
1974 # ifdef bgr
1975 # undef bgr
1976 # endif
1977 }
1978 }
1979
1980 static int
1981 make_gray_file_colormap(png_image_read_control *display)
1982 {
1983 unsigned int i;
1984
1985 for (i=0; i<256; ++i)
1986 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1987
1988 return i;
1989 }
1990
1991 static int
1992 make_gray_colormap(png_image_read_control *display)
1993 {
1994 unsigned int i;
1995
1996 for (i=0; i<256; ++i)
1997 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
1998
1999 return i;
2000 }
2001 #define PNG_GRAY_COLORMAP_ENTRIES 256
2002
2003 static int
2004 make_ga_colormap(png_image_read_control *display)
2005 {
2006 unsigned int i, a;
2007
2008 /* Alpha is retained, the output will be a color-map with entries
2009 * selected by six levels of alpha. One transparent entry, 6 gray
2010 * levels for all the intermediate alpha values, leaving 230 entries
2011 * for the opaque grays. The color-map entries are the six values
2012 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2013 * relevant entry.
2014 *
2015 * if (alpha > 229) // opaque
2016 * {
2017 * // The 231 entries are selected to make the math below work:
2018 * base = 0;
2019 * entry = (231 * gray + 128) >> 8;
2020 * }
2021 * else if (alpha < 26) // transparent
2022 * {
2023 * base = 231;
2024 * entry = 0;
2025 * }
2026 * else // partially opaque
2027 * {
2028 * base = 226 + 6 * PNG_DIV51(alpha);
2029 * entry = PNG_DIV51(gray);
2030 * }
2031 */
2032 i = 0;
2033 while (i < 231)
2034 {
2035 unsigned int gray = (i * 256 + 115) / 231;
2036 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2037 }
2038
2039 /* 255 is used here for the component values for consistency with the code
2040 * that undoes premultiplication in pngwrite.c.
2041 */
2042 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2043
2044 for (a=1; a<5; ++a)
2045 {
2046 unsigned int g;
2047
2048 for (g=0; g<6; ++g)
2049 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2050 P_sRGB);
2051 }
2052
2053 return i;
2054 }
2055
2056 #define PNG_GA_COLORMAP_ENTRIES 256
2057
2058 static int
2059 make_rgb_colormap(png_image_read_control *display)
2060 {
2061 unsigned int i, r;
2062
2063 /* Build a 6x6x6 opaque RGB cube */
2064 for (i=r=0; r<6; ++r)
2065 {
2066 unsigned int g;
2067
2068 for (g=0; g<6; ++g)
2069 {
2070 unsigned int b;
2071
2072 for (b=0; b<6; ++b)
2073 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2074 P_sRGB);
2075 }
2076 }
2077
2078 return i;
2079 }
2080
2081 #define PNG_RGB_COLORMAP_ENTRIES 216
2082
2083 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2084 #define PNG_RGB_INDEX(r,g,b) \
2085 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2086
2087 static int
2088 png_image_read_colormap(png_voidp argument)
2089 {
2090 png_image_read_control *display =
2091 png_voidcast(png_image_read_control*, argument);
2092 const png_imagep image = display->image;
2093
2094 const png_structrp png_ptr = image->opaque->png_ptr;
2095 const png_uint_32 output_format = image->format;
2096 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2097 P_LINEAR : P_sRGB;
2098
2099 unsigned int cmap_entries;
2100 unsigned int output_processing; /* Output processing option */
2101 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2102
2103 /* Background information; the background color and the index of this color
2104 * in the color-map if it exists (else 256).
2105 */
2106 unsigned int background_index = 256;
2107 png_uint_32 back_r, back_g, back_b;
2108
2109 /* Flags to accumulate things that need to be done to the input. */
2110 int expand_tRNS = 0;
2111
2112 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2113 * very difficult to do, the results look awful, and it is difficult to see
2114 * what possible use it is because the application can't control the
2115 * color-map.
2116 */
2117 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2118 png_ptr->num_trans > 0) /* alpha in input */ &&
2119 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2120 {
2121 if (output_encoding == P_LINEAR) /* compose on black */
2122 back_b = back_g = back_r = 0;
2123
2124 else if (display->background == NULL /* no way to remove it */)
2125 png_error(png_ptr,
2126 "a background color must be supplied to remove alpha/transparency");
2127
2128 /* Get a copy of the background color (this avoids repeating the checks
2129 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2130 * output format.
2131 */
2132 else
2133 {
2134 back_g = display->background->green;
2135 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2136 {
2137 back_r = display->background->red;
2138 back_b = display->background->blue;
2139 }
2140 else
2141 back_b = back_r = back_g;
2142 }
2143 }
2144
2145 else if (output_encoding == P_LINEAR)
2146 back_b = back_r = back_g = 65535;
2147
2148 else
2149 back_b = back_r = back_g = 255;
2150
2151 /* Default the input file gamma if required - this is necessary because
2152 * libpng assumes that if no gamma information is present the data is in the
2153 * output format, but the simplified API deduces the gamma from the input
2154 * format.
2155 */
2156 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2157 {
2158 /* Do this directly, not using the png_colorspace functions, to ensure
2159 * that it happens even if the colorspace is invalid (though probably if
2160 * it is the setting will be ignored) Note that the same thing can be
2161 * achieved at the application interface with png_set_gAMA.
2162 */
2163 if (png_ptr->bit_depth == 16 &&
2164 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2165 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2166
2167 else
2168 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2169
2170 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2171 }
2172
2173 /* Decide what to do based on the PNG color type of the input data. The
2174 * utility function png_create_colormap_entry deals with most aspects of the
2175 * output transformations; this code works out how to produce bytes of
2176 * color-map entries from the original format.
2177 */
2178 switch (png_ptr->color_type)
2179 {
2180 case PNG_COLOR_TYPE_GRAY:
2181 if (png_ptr->bit_depth <= 8)
2182 {
2183 /* There at most 256 colors in the output, regardless of
2184 * transparency.
2185 */
2186 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2187
2188 cmap_entries = 1U << png_ptr->bit_depth;
2189 if (cmap_entries > image->colormap_entries)
2190 png_error(png_ptr, "gray[8] color-map: too few entries");
2191
2192 step = 255 / (cmap_entries - 1);
2193 output_processing = PNG_CMAP_NONE;
2194
2195 /* If there is a tRNS chunk then this either selects a transparent
2196 * value or, if the output has no alpha, the background color.
2197 */
2198 if (png_ptr->num_trans > 0)
2199 {
2200 trans = png_ptr->trans_color.gray;
2201
2202 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2203 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2204 }
2205
2206 /* png_create_colormap_entry just takes an RGBA and writes the
2207 * corresponding color-map entry using the format from 'image',
2208 * including the required conversion to sRGB or linear as
2209 * appropriate. The input values are always either sRGB (if the
2210 * gamma correction flag is 0) or 0..255 scaled file encoded values
2211 * (if the function must gamma correct them).
2212 */
2213 for (i=val=0; i<cmap_entries; ++i, val += step)
2214 {
2215 /* 'i' is a file value. While this will result in duplicated
2216 * entries for 8-bit non-sRGB encoded files it is necessary to
2217 * have non-gamma corrected values to do tRNS handling.
2218 */
2219 if (i != trans)
2220 png_create_colormap_entry(display, i, val, val, val, 255,
2221 P_FILE/*8-bit with file gamma*/);
2222
2223 /* Else this entry is transparent. The colors don't matter if
2224 * there is an alpha channel (back_alpha == 0), but it does no
2225 * harm to pass them in; the values are not set above so this
2226 * passes in white.
2227 *
2228 * NOTE: this preserves the full precision of the application
2229 * supplied background color when it is used.
2230 */
2231 else
2232 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2233 back_alpha, output_encoding);
2234 }
2235
2236 /* We need libpng to preserve the original encoding. */
2237 data_encoding = P_FILE;
2238
2239 /* The rows from libpng, while technically gray values, are now also
2240 * color-map indices; however, they may need to be expanded to 1
2241 * byte per pixel. This is what png_set_packing does (i.e., it
2242 * unpacks the bit values into bytes.)
2243 */
2244 if (png_ptr->bit_depth < 8)
2245 png_set_packing(png_ptr);
2246 }
2247
2248 else /* bit depth is 16 */
2249 {
2250 /* The 16-bit input values can be converted directly to 8-bit gamma
2251 * encoded values; however, if a tRNS chunk is present 257 color-map
2252 * entries are required. This means that the extra entry requires
2253 * special processing; add an alpha channel, sacrifice gray level
2254 * 254 and convert transparent (alpha==0) entries to that.
2255 *
2256 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2257 * same time to minimize quality loss. If a tRNS chunk is present
2258 * this means libpng must handle it too; otherwise it is impossible
2259 * to do the exact match on the 16-bit value.
2260 *
2261 * If the output has no alpha channel *and* the background color is
2262 * gray then it is possible to let libpng handle the substitution by
2263 * ensuring that the corresponding gray level matches the background
2264 * color exactly.
2265 */
2266 data_encoding = P_sRGB;
2267
2268 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2269 png_error(png_ptr, "gray[16] color-map: too few entries");
2270
2271 cmap_entries = make_gray_colormap(display);
2272
2273 if (png_ptr->num_trans > 0)
2274 {
2275 unsigned int back_alpha;
2276
2277 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2278 back_alpha = 0;
2279
2280 else
2281 {
2282 if (back_r == back_g && back_g == back_b)
2283 {
2284 /* Background is gray; no special processing will be
2285 * required.
2286 */
2287 png_color_16 c;
2288 png_uint_32 gray = back_g;
2289
2290 if (output_encoding == P_LINEAR)
2291 {
2292 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2293
2294 /* And make sure the corresponding palette entry
2295 * matches.
2296 */
2297 png_create_colormap_entry(display, gray, back_g, back_g,
2298 back_g, 65535, P_LINEAR);
2299 }
2300
2301 /* The background passed to libpng, however, must be the
2302 * sRGB value.
2303 */
2304 c.index = 0; /*unused*/
2305 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2306
2307 /* NOTE: does this work without expanding tRNS to alpha?
2308 * It should be the color->gray case below apparently
2309 * doesn't.
2310 */
2311 png_set_background_fixed(png_ptr, &c,
2312 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2313 0/*gamma: not used*/);
2314
2315 output_processing = PNG_CMAP_NONE;
2316 break;
2317 }
2318 #ifdef __COVERITY__
2319 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2320 * here.
2321 */
2322 back_alpha = 255;
2323 #else
2324 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2325 #endif
2326 }
2327
2328 /* output_processing means that the libpng-processed row will be
2329 * 8-bit GA and it has to be processing to single byte color-map
2330 * values. Entry 254 is replaced by either a completely
2331 * transparent entry or by the background color at full
2332 * precision (and the background color is not a simple gray
2333 * level in this case.)
2334 */
2335 expand_tRNS = 1;
2336 output_processing = PNG_CMAP_TRANS;
2337 background_index = 254;
2338
2339 /* And set (overwrite) color-map entry 254 to the actual
2340 * background color at full precision.
2341 */
2342 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2343 back_alpha, output_encoding);
2344 }
2345
2346 else
2347 output_processing = PNG_CMAP_NONE;
2348 }
2349 break;
2350
2351 case PNG_COLOR_TYPE_GRAY_ALPHA:
2352 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2353 * of 65536 combinations. If, however, the alpha channel is to be
2354 * removed there are only 256 possibilities if the background is gray.
2355 * (Otherwise there is a subset of the 65536 possibilities defined by
2356 * the triangle between black, white and the background color.)
2357 *
2358 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2359 * worry about tRNS matching - tRNS is ignored if there is an alpha
2360 * channel.
2361 */
2362 data_encoding = P_sRGB;
2363
2364 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2365 {
2366 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2367 png_error(png_ptr, "gray+alpha color-map: too few entries");
2368
2369 cmap_entries = make_ga_colormap(display);
2370
2371 background_index = PNG_CMAP_GA_BACKGROUND;
2372 output_processing = PNG_CMAP_GA;
2373 }
2374
2375 else /* alpha is removed */
2376 {
2377 /* Alpha must be removed as the PNG data is processed when the
2378 * background is a color because the G and A channels are
2379 * independent and the vector addition (non-parallel vectors) is a
2380 * 2-D problem.
2381 *
2382 * This can be reduced to the same algorithm as above by making a
2383 * colormap containing gray levels (for the opaque grays), a
2384 * background entry (for a transparent pixel) and a set of four six
2385 * level color values, one set for each intermediate alpha value.
2386 * See the comments in make_ga_colormap for how this works in the
2387 * per-pixel processing.
2388 *
2389 * If the background is gray, however, we only need a 256 entry gray
2390 * level color map. It is sufficient to make the entry generated
2391 * for the background color be exactly the color specified.
2392 */
2393 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2394 (back_r == back_g && back_g == back_b))
2395 {
2396 /* Background is gray; no special processing will be required. */
2397 png_color_16 c;
2398 png_uint_32 gray = back_g;
2399
2400 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2401 png_error(png_ptr, "gray-alpha color-map: too few entries");
2402
2403 cmap_entries = make_gray_colormap(display);
2404
2405 if (output_encoding == P_LINEAR)
2406 {
2407 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2408
2409 /* And make sure the corresponding palette entry matches. */
2410 png_create_colormap_entry(display, gray, back_g, back_g,
2411 back_g, 65535, P_LINEAR);
2412 }
2413
2414 /* The background passed to libpng, however, must be the sRGB
2415 * value.
2416 */
2417 c.index = 0; /*unused*/
2418 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2419
2420 png_set_background_fixed(png_ptr, &c,
2421 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2422 0/*gamma: not used*/);
2423
2424 output_processing = PNG_CMAP_NONE;
2425 }
2426
2427 else
2428 {
2429 png_uint_32 i, a;
2430
2431 /* This is the same as png_make_ga_colormap, above, except that
2432 * the entries are all opaque.
2433 */
2434 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2435 png_error(png_ptr, "ga-alpha color-map: too few entries");
2436
2437 i = 0;
2438 while (i < 231)
2439 {
2440 png_uint_32 gray = (i * 256 + 115) / 231;
2441 png_create_colormap_entry(display, i++, gray, gray, gray,
2442 255, P_sRGB);
2443 }
2444
2445 /* NOTE: this preserves the full precision of the application
2446 * background color.
2447 */
2448 background_index = i;
2449 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2450 #ifdef __COVERITY__
2451 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2452 * here.
2453 */ 255U,
2454 #else
2455 output_encoding == P_LINEAR ? 65535U : 255U,
2456 #endif
2457 output_encoding);
2458
2459 /* For non-opaque input composite on the sRGB background - this
2460 * requires inverting the encoding for each component. The input
2461 * is still converted to the sRGB encoding because this is a
2462 * reasonable approximate to the logarithmic curve of human
2463 * visual sensitivity, at least over the narrow range which PNG
2464 * represents. Consequently 'G' is always sRGB encoded, while
2465 * 'A' is linear. We need the linear background colors.
2466 */
2467 if (output_encoding == P_sRGB) /* else already linear */
2468 {
2469 /* This may produce a value not exactly matching the
2470 * background, but that's ok because these numbers are only
2471 * used when alpha != 0
2472 */
2473 back_r = png_sRGB_table[back_r];
2474 back_g = png_sRGB_table[back_g];
2475 back_b = png_sRGB_table[back_b];
2476 }
2477
2478 for (a=1; a<5; ++a)
2479 {
2480 unsigned int g;
2481
2482 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2483 * by an 8-bit alpha value (0..255).
2484 */
2485 png_uint_32 alpha = 51 * a;
2486 png_uint_32 back_rx = (255-alpha) * back_r;
2487 png_uint_32 back_gx = (255-alpha) * back_g;
2488 png_uint_32 back_bx = (255-alpha) * back_b;
2489
2490 for (g=0; g<6; ++g)
2491 {
2492 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2493
2494 png_create_colormap_entry(display, i++,
2495 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2496 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2497 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2498 }
2499 }
2500
2501 cmap_entries = i;
2502 output_processing = PNG_CMAP_GA;
2503 }
2504 }
2505 break;
2506
2507 case PNG_COLOR_TYPE_RGB:
2508 case PNG_COLOR_TYPE_RGB_ALPHA:
2509 /* Exclude the case where the output is gray; we can always handle this
2510 * with the cases above.
2511 */
2512 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2513 {
2514 /* The color-map will be grayscale, so we may as well convert the
2515 * input RGB values to a simple grayscale and use the grayscale
2516 * code above.
2517 *
2518 * NOTE: calling this apparently damages the recognition of the
2519 * transparent color in background color handling; call
2520 * png_set_tRNS_to_alpha before png_set_background_fixed.
2521 */
2522 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2523 -1);
2524 data_encoding = P_sRGB;
2525
2526 /* The output will now be one or two 8-bit gray or gray+alpha
2527 * channels. The more complex case arises when the input has alpha.
2528 */
2529 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2530 png_ptr->num_trans > 0) &&
2531 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2532 {
2533 /* Both input and output have an alpha channel, so no background
2534 * processing is required; just map the GA bytes to the right
2535 * color-map entry.
2536 */
2537 expand_tRNS = 1;
2538
2539 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2540 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2541
2542 cmap_entries = make_ga_colormap(display);
2543 background_index = PNG_CMAP_GA_BACKGROUND;
2544 output_processing = PNG_CMAP_GA;
2545 }
2546
2547 else
2548 {
2549 /* Either the input or the output has no alpha channel, so there
2550 * will be no non-opaque pixels in the color-map; it will just be
2551 * grayscale.
2552 */
2553 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2554 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2555
2556 /* Ideally this code would use libpng to do the gamma correction,
2557 * but if an input alpha channel is to be removed we will hit the
2558 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2559 * correction bug). Fix this by dropping the gamma correction in
2560 * this case and doing it in the palette; this will result in
2561 * duplicate palette entries, but that's better than the
2562 * alternative of double gamma correction.
2563 */
2564 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2565 png_ptr->num_trans > 0) &&
2566 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2567 {
2568 cmap_entries = make_gray_file_colormap(display);
2569 data_encoding = P_FILE;
2570 }
2571
2572 else
2573 cmap_entries = make_gray_colormap(display);
2574
2575 /* But if the input has alpha or transparency it must be removed
2576 */
2577 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2578 png_ptr->num_trans > 0)
2579 {
2580 png_color_16 c;
2581 png_uint_32 gray = back_g;
2582
2583 /* We need to ensure that the application background exists in
2584 * the colormap and that completely transparent pixels map to
2585 * it. Achieve this simply by ensuring that the entry
2586 * selected for the background really is the background color.
2587 */
2588 if (data_encoding == P_FILE) /* from the fixup above */
2589 {
2590 /* The app supplied a gray which is in output_encoding, we
2591 * need to convert it to a value of the input (P_FILE)
2592 * encoding then set this palette entry to the required
2593 * output encoding.
2594 */
2595 if (output_encoding == P_sRGB)
2596 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2597
2598 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2599 png_ptr->colorspace.gamma)); /* now P_FILE */
2600
2601 /* And make sure the corresponding palette entry contains
2602 * exactly the required sRGB value.
2603 */
2604 png_create_colormap_entry(display, gray, back_g, back_g,
2605 back_g, 0/*unused*/, output_encoding);
2606 }
2607
2608 else if (output_encoding == P_LINEAR)
2609 {
2610 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2611
2612 /* And make sure the corresponding palette entry matches.
2613 */
2614 png_create_colormap_entry(display, gray, back_g, back_g,
2615 back_g, 0/*unused*/, P_LINEAR);
2616 }
2617
2618 /* The background passed to libpng, however, must be the
2619 * output (normally sRGB) value.
2620 */
2621 c.index = 0; /*unused*/
2622 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2623
2624 /* NOTE: the following is apparently a bug in libpng. Without
2625 * it the transparent color recognition in
2626 * png_set_background_fixed seems to go wrong.
2627 */
2628 expand_tRNS = 1;
2629 png_set_background_fixed(png_ptr, &c,
2630 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2631 0/*gamma: not used*/);
2632 }
2633
2634 output_processing = PNG_CMAP_NONE;
2635 }
2636 }
2637
2638 else /* output is color */
2639 {
2640 /* We could use png_quantize here so long as there is no transparent
2641 * color or alpha; png_quantize ignores alpha. Easier overall just
2642 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2643 * Consequently we always want libpng to produce sRGB data.
2644 */
2645 data_encoding = P_sRGB;
2646
2647 /* Is there any transparency or alpha? */
2648 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2649 png_ptr->num_trans > 0)
2650 {
2651 /* Is there alpha in the output too? If so all four channels are
2652 * processed into a special RGB cube with alpha support.
2653 */
2654 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2655 {
2656 png_uint_32 r;
2657
2658 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2659 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2660
2661 cmap_entries = make_rgb_colormap(display);
2662
2663 /* Add a transparent entry. */
2664 png_create_colormap_entry(display, cmap_entries, 255, 255,
2665 255, 0, P_sRGB);
2666
2667 /* This is stored as the background index for the processing
2668 * algorithm.
2669 */
2670 background_index = cmap_entries++;
2671
2672 /* Add 27 r,g,b entries each with alpha 0.5. */
2673 for (r=0; r<256; r = (r << 1) | 0x7f)
2674 {
2675 png_uint_32 g;
2676
2677 for (g=0; g<256; g = (g << 1) | 0x7f)
2678 {
2679 png_uint_32 b;
2680
2681 /* This generates components with the values 0, 127 and
2682 * 255
2683 */
2684 for (b=0; b<256; b = (b << 1) | 0x7f)
2685 png_create_colormap_entry(display, cmap_entries++,
2686 r, g, b, 128, P_sRGB);
2687 }
2688 }
2689
2690 expand_tRNS = 1;
2691 output_processing = PNG_CMAP_RGB_ALPHA;
2692 }
2693
2694 else
2695 {
2696 /* Alpha/transparency must be removed. The background must
2697 * exist in the color map (achieved by setting adding it after
2698 * the 666 color-map). If the standard processing code will
2699 * pick up this entry automatically that's all that is
2700 * required; libpng can be called to do the background
2701 * processing.
2702 */
2703 unsigned int sample_size =
2704 PNG_IMAGE_SAMPLE_SIZE(output_format);
2705 png_uint_32 r, g, b; /* sRGB background */
2706
2707 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2708 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2709
2710 cmap_entries = make_rgb_colormap(display);
2711
2712 png_create_colormap_entry(display, cmap_entries, back_r,
2713 back_g, back_b, 0/*unused*/, output_encoding);
2714
2715 if (output_encoding == P_LINEAR)
2716 {
2717 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2718 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2719 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2720 }
2721
2722 else
2723 {
2724 r = back_r;
2725 g = back_g;
2726 b = back_g;
2727 }
2728
2729 /* Compare the newly-created color-map entry with the one the
2730 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2731 * match, add the new one and set this as the background
2732 * index.
2733 */
2734 if (memcmp((png_const_bytep)display->colormap +
2735 sample_size * cmap_entries,
2736 (png_const_bytep)display->colormap +
2737 sample_size * PNG_RGB_INDEX(r,g,b),
2738 sample_size) != 0)
2739 {
2740 /* The background color must be added. */
2741 background_index = cmap_entries++;
2742
2743 /* Add 27 r,g,b entries each with created by composing with
2744 * the background at alpha 0.5.
2745 */
2746 for (r=0; r<256; r = (r << 1) | 0x7f)
2747 {
2748 for (g=0; g<256; g = (g << 1) | 0x7f)
2749 {
2750 /* This generates components with the values 0, 127
2751 * and 255
2752 */
2753 for (b=0; b<256; b = (b << 1) | 0x7f)
2754 png_create_colormap_entry(display, cmap_entries++,
2755 png_colormap_compose(display, r, P_sRGB, 128,
2756 back_r, output_encoding),
2757 png_colormap_compose(display, g, P_sRGB, 128,
2758 back_g, output_encoding),
2759 png_colormap_compose(display, b, P_sRGB, 128,
2760 back_b, output_encoding),
2761 0/*unused*/, output_encoding);
2762 }
2763 }
2764
2765 expand_tRNS = 1;
2766 output_processing = PNG_CMAP_RGB_ALPHA;
2767 }
2768
2769 else /* background color is in the standard color-map */
2770 {
2771 png_color_16 c;
2772
2773 c.index = 0; /*unused*/
2774 c.red = (png_uint_16)back_r;
2775 c.gray = c.green = (png_uint_16)back_g;
2776 c.blue = (png_uint_16)back_b;
2777
2778 png_set_background_fixed(png_ptr, &c,
2779 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2780 0/*gamma: not used*/);
2781
2782 output_processing = PNG_CMAP_RGB;
2783 }
2784 }
2785 }
2786
2787 else /* no alpha or transparency in the input */
2788 {
2789 /* Alpha in the output is irrelevant, simply map the opaque input
2790 * pixels to the 6x6x6 color-map.
2791 */
2792 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2793 png_error(png_ptr, "rgb color-map: too few entries");
2794
2795 cmap_entries = make_rgb_colormap(display);
2796 output_processing = PNG_CMAP_RGB;
2797 }
2798 }
2799 break;
2800
2801 case PNG_COLOR_TYPE_PALETTE:
2802 /* It's already got a color-map. It may be necessary to eliminate the
2803 * tRNS entries though.
2804 */
2805 {
2806 unsigned int num_trans = png_ptr->num_trans;
2807 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2808 png_const_colorp colormap = png_ptr->palette;
2809 const int do_background = trans != NULL &&
2810 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2811 unsigned int i;
2812
2813 /* Just in case: */
2814 if (trans == NULL)
2815 num_trans = 0;
2816
2817 output_processing = PNG_CMAP_NONE;
2818 data_encoding = P_FILE; /* Don't change from color-map indices */
2819 cmap_entries = png_ptr->num_palette;
2820 if (cmap_entries > 256)
2821 cmap_entries = 256;
2822
2823 if (cmap_entries > image->colormap_entries)
2824 png_error(png_ptr, "palette color-map: too few entries");
2825
2826 for (i=0; i < cmap_entries; ++i)
2827 {
2828 if (do_background != 0 && i < num_trans && trans[i] < 255)
2829 {
2830 if (trans[i] == 0)
2831 png_create_colormap_entry(display, i, back_r, back_g,
2832 back_b, 0, output_encoding);
2833
2834 else
2835 {
2836 /* Must compose the PNG file color in the color-map entry
2837 * on the sRGB color in 'back'.
2838 */
2839 png_create_colormap_entry(display, i,
2840 png_colormap_compose(display, colormap[i].red, P_FILE,
2841 trans[i], back_r, output_encoding),
2842 png_colormap_compose(display, colormap[i].green, P_FILE,
2843 trans[i], back_g, output_encoding),
2844 png_colormap_compose(display, colormap[i].blue, P_FILE,
2845 trans[i], back_b, output_encoding),
2846 output_encoding == P_LINEAR ? trans[i] * 257U :
2847 trans[i],
2848 output_encoding);
2849 }
2850 }
2851
2852 else
2853 png_create_colormap_entry(display, i, colormap[i].red,
2854 colormap[i].green, colormap[i].blue,
2855 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2856 }
2857
2858 /* The PNG data may have indices packed in fewer than 8 bits, it
2859 * must be expanded if so.
2860 */
2861 if (png_ptr->bit_depth < 8)
2862 png_set_packing(png_ptr);
2863 }
2864 break;
2865
2866 default:
2867 png_error(png_ptr, "invalid PNG color type");
2868 /*NOT REACHED*/
2869 }
2870
2871 /* Now deal with the output processing */
2872 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2873 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2874 png_set_tRNS_to_alpha(png_ptr);
2875
2876 switch (data_encoding)
2877 {
2878 case P_sRGB:
2879 /* Change to 8-bit sRGB */
2880 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2881 /* FALL THROUGH */
2882
2883 case P_FILE:
2884 if (png_ptr->bit_depth > 8)
2885 png_set_scale_16(png_ptr);
2886 break;
2887
2888 #ifdef __GNUC__
2889 default:
2890 png_error(png_ptr, "bad data option (internal error)");
2891 #endif
2892 }
2893
2894 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2895 png_error(png_ptr, "color map overflow (BAD internal error)");
2896
2897 image->colormap_entries = cmap_entries;
2898
2899 /* Double check using the recorded background index */
2900 switch (output_processing)
2901 {
2902 case PNG_CMAP_NONE:
2903 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2904 goto bad_background;
2905 break;
2906
2907 case PNG_CMAP_GA:
2908 if (background_index != PNG_CMAP_GA_BACKGROUND)
2909 goto bad_background;
2910 break;
2911
2912 case PNG_CMAP_TRANS:
2913 if (background_index >= cmap_entries ||
2914 background_index != PNG_CMAP_TRANS_BACKGROUND)
2915 goto bad_background;
2916 break;
2917
2918 case PNG_CMAP_RGB:
2919 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2920 goto bad_background;
2921 break;
2922
2923 case PNG_CMAP_RGB_ALPHA:
2924 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2925 goto bad_background;
2926 break;
2927
2928 default:
2929 png_error(png_ptr, "bad processing option (internal error)");
2930
2931 bad_background:
2932 png_error(png_ptr, "bad background index (internal error)");
2933 }
2934
2935 display->colormap_processing = output_processing;
2936
2937 return 1/*ok*/;
2938 }
2939
2940 /* The final part of the color-map read called from png_image_finish_read. */
2941 static int
2942 png_image_read_and_map(png_voidp argument)
2943 {
2944 png_image_read_control *display = png_voidcast(png_image_read_control*,
2945 argument);
2946 png_imagep image = display->image;
2947 png_structrp png_ptr = image->opaque->png_ptr;
2948 int passes;
2949
2950 /* Called when the libpng data must be transformed into the color-mapped
2951 * form. There is a local row buffer in display->local and this routine must
2952 * do the interlace handling.
2953 */
2954 switch (png_ptr->interlaced)
2955 {
2956 case PNG_INTERLACE_NONE:
2957 passes = 1;
2958 break;
2959
2960 case PNG_INTERLACE_ADAM7:
2961 passes = PNG_INTERLACE_ADAM7_PASSES;
2962 break;
2963
2964 default:
2965 png_error(png_ptr, "unknown interlace type");
2966 }
2967
2968 {
2969 png_uint_32 height = image->height;
2970 png_uint_32 width = image->width;
2971 int proc = display->colormap_processing;
2972 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2973 ptrdiff_t step_row = display->row_bytes;
2974 int pass;
2975
2976 for (pass = 0; pass < passes; ++pass)
2977 {
2978 unsigned int startx, stepx, stepy;
2979 png_uint_32 y;
2980
2981 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2982 {
2983 /* The row may be empty for a short image: */
2984 if (PNG_PASS_COLS(width, pass) == 0)
2985 continue;
2986
2987 startx = PNG_PASS_START_COL(pass);
2988 stepx = PNG_PASS_COL_OFFSET(pass);
2989 y = PNG_PASS_START_ROW(pass);
2990 stepy = PNG_PASS_ROW_OFFSET(pass);
2991 }
2992
2993 else
2994 {
2995 y = 0;
2996 startx = 0;
2997 stepx = stepy = 1;
2998 }
2999
3000 for (; y<height; y += stepy)
3001 {
3002 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3003 png_bytep outrow = first_row + y * step_row;
3004 png_const_bytep end_row = outrow + width;
3005
3006 /* Read read the libpng data into the temporary buffer. */
3007 png_read_row(png_ptr, inrow, NULL);
3008
3009 /* Now process the row according to the processing option, note
3010 * that the caller verifies that the format of the libpng output
3011 * data is as required.
3012 */
3013 outrow += startx;
3014 switch (proc)
3015 {
3016 case PNG_CMAP_GA:
3017 for (; outrow < end_row; outrow += stepx)
3018 {
3019 /* The data is always in the PNG order */
3020 unsigned int gray = *inrow++;
3021 unsigned int alpha = *inrow++;
3022 unsigned int entry;
3023
3024 /* NOTE: this code is copied as a comment in
3025 * make_ga_colormap above. Please update the
3026 * comment if you change this code!
3027 */
3028 if (alpha > 229) /* opaque */
3029 {
3030 entry = (231 * gray + 128) >> 8;
3031 }
3032 else if (alpha < 26) /* transparent */
3033 {
3034 entry = 231;
3035 }
3036 else /* partially opaque */
3037 {
3038 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3039 }
3040
3041 *outrow = (png_byte)entry;
3042 }
3043 break;
3044
3045 case PNG_CMAP_TRANS:
3046 for (; outrow < end_row; outrow += stepx)
3047 {
3048 png_byte gray = *inrow++;
3049 png_byte alpha = *inrow++;
3050
3051 if (alpha == 0)
3052 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3053
3054 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3055 *outrow = gray;
3056
3057 else
3058 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3059 }
3060 break;
3061
3062 case PNG_CMAP_RGB:
3063 for (; outrow < end_row; outrow += stepx)
3064 {
3065 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3066 inrow += 3;
3067 }
3068 break;
3069
3070 case PNG_CMAP_RGB_ALPHA:
3071 for (; outrow < end_row; outrow += stepx)
3072 {
3073 unsigned int alpha = inrow[3];
3074
3075 /* Because the alpha entries only hold alpha==0.5 values
3076 * split the processing at alpha==0.25 (64) and 0.75
3077 * (196).
3078 */
3079
3080 if (alpha >= 196)
3081 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3082 inrow[2]);
3083
3084 else if (alpha < 64)
3085 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3086
3087 else
3088 {
3089 /* Likewise there are three entries for each of r, g
3090 * and b. We could select the entry by popcount on
3091 * the top two bits on those architectures that
3092 * support it, this is what the code below does,
3093 * crudely.
3094 */
3095 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3096
3097 /* Here are how the values map:
3098 *
3099 * 0x00 .. 0x3f -> 0
3100 * 0x40 .. 0xbf -> 1
3101 * 0xc0 .. 0xff -> 2
3102 *
3103 * So, as above with the explicit alpha checks, the
3104 * breakpoints are at 64 and 196.
3105 */
3106 if (inrow[0] & 0x80) back_i += 9; /* red */
3107 if (inrow[0] & 0x40) back_i += 9;
3108 if (inrow[0] & 0x80) back_i += 3; /* green */
3109 if (inrow[0] & 0x40) back_i += 3;
3110 if (inrow[0] & 0x80) back_i += 1; /* blue */
3111 if (inrow[0] & 0x40) back_i += 1;
3112
3113 *outrow = (png_byte)back_i;
3114 }
3115
3116 inrow += 4;
3117 }
3118 break;
3119
3120 default:
3121 break;
3122 }
3123 }
3124 }
3125 }
3126
3127 return 1;
3128 }
3129
3130 static int
3131 png_image_read_colormapped(png_voidp argument)
3132 {
3133 png_image_read_control *display = png_voidcast(png_image_read_control*,
3134 argument);
3135 png_imagep image = display->image;
3136 png_controlp control = image->opaque;
3137 png_structrp png_ptr = control->png_ptr;
3138 png_inforp info_ptr = control->info_ptr;
3139
3140 int passes = 0; /* As a flag */
3141
3142 PNG_SKIP_CHUNKS(png_ptr);
3143
3144 /* Update the 'info' structure and make sure the result is as required; first
3145 * make sure to turn on the interlace handling if it will be required
3146 * (because it can't be turned on *after* the call to png_read_update_info!)
3147 */
3148 if (display->colormap_processing == PNG_CMAP_NONE)
3149 passes = png_set_interlace_handling(png_ptr);
3150
3151 png_read_update_info(png_ptr, info_ptr);
3152
3153 /* The expected output can be deduced from the colormap_processing option. */
3154 switch (display->colormap_processing)
3155 {
3156 case PNG_CMAP_NONE:
3157 /* Output must be one channel and one byte per pixel, the output
3158 * encoding can be anything.
3159 */
3160 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3161 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3162 info_ptr->bit_depth == 8)
3163 break;
3164
3165 goto bad_output;
3166
3167 case PNG_CMAP_TRANS:
3168 case PNG_CMAP_GA:
3169 /* Output must be two channels and the 'G' one must be sRGB, the latter
3170 * can be checked with an exact number because it should have been set
3171 * to this number above!
3172 */
3173 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3174 info_ptr->bit_depth == 8 &&
3175 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3176 image->colormap_entries == 256)
3177 break;
3178
3179 goto bad_output;
3180
3181 case PNG_CMAP_RGB:
3182 /* Output must be 8-bit sRGB encoded RGB */
3183 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3184 info_ptr->bit_depth == 8 &&
3185 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3186 image->colormap_entries == 216)
3187 break;
3188
3189 goto bad_output;
3190
3191 case PNG_CMAP_RGB_ALPHA:
3192 /* Output must be 8-bit sRGB encoded RGBA */
3193 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3194 info_ptr->bit_depth == 8 &&
3195 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3196 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3197 break;
3198
3199 /* goto bad_output; */
3200 /* FALL THROUGH */
3201
3202 default:
3203 bad_output:
3204 png_error(png_ptr, "bad color-map processing (internal error)");
3205 }
3206
3207 /* Now read the rows. Do this here if it is possible to read directly into
3208 * the output buffer, otherwise allocate a local row buffer of the maximum
3209 * size libpng requires and call the relevant processing routine safely.
3210 */
3211 {
3212 png_voidp first_row = display->buffer;
3213 ptrdiff_t row_bytes = display->row_stride;
3214
3215 /* The following expression is designed to work correctly whether it gives
3216 * a signed or an unsigned result.
3217 */
3218 if (row_bytes < 0)
3219 {
3220 char *ptr = png_voidcast(char*, first_row);
3221 ptr += (image->height-1) * (-row_bytes);
3222 first_row = png_voidcast(png_voidp, ptr);
3223 }
3224
3225 display->first_row = first_row;
3226 display->row_bytes = row_bytes;
3227 }
3228
3229 if (passes == 0)
3230 {
3231 int result;
3232 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3233
3234 display->local_row = row;
3235 result = png_safe_execute(image, png_image_read_and_map, display);
3236 display->local_row = NULL;
3237 png_free(png_ptr, row);
3238
3239 return result;
3240 }
3241
3242 else
3243 {
3244 png_alloc_size_t row_bytes = display->row_bytes;
3245
3246 while (--passes >= 0)
3247 {
3248 png_uint_32 y = image->height;
3249 png_bytep row = png_voidcast(png_bytep, display->first_row);
3250
3251 while (y-- > 0)
3252 {
3253 png_read_row(png_ptr, row, NULL);
3254 row += row_bytes;
3255 }
3256 }
3257
3258 return 1;
3259 }
3260 }
3261
3262 /* Just the row reading part of png_image_read. */
3263 static int
3264 png_image_read_composite(png_voidp argument)
3265 {
3266 png_image_read_control *display = png_voidcast(png_image_read_control*,
3267 argument);
3268 png_imagep image = display->image;
3269 png_structrp png_ptr = image->opaque->png_ptr;
3270 int passes;
3271
3272 switch (png_ptr->interlaced)
3273 {
3274 case PNG_INTERLACE_NONE:
3275 passes = 1;
3276 break;
3277
3278 case PNG_INTERLACE_ADAM7:
3279 passes = PNG_INTERLACE_ADAM7_PASSES;
3280 break;
3281
3282 default:
3283 png_error(png_ptr, "unknown interlace type");
3284 }
3285
3286 {
3287 png_uint_32 height = image->height;
3288 png_uint_32 width = image->width;
3289 ptrdiff_t step_row = display->row_bytes;
3290 unsigned int channels =
3291 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3292 int pass;
3293
3294 for (pass = 0; pass < passes; ++pass)
3295 {
3296 unsigned int startx, stepx, stepy;
3297 png_uint_32 y;
3298
3299 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3300 {
3301 /* The row may be empty for a short image: */
3302 if (PNG_PASS_COLS(width, pass) == 0)
3303 continue;
3304
3305 startx = PNG_PASS_START_COL(pass) * channels;
3306 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3307 y = PNG_PASS_START_ROW(pass);
3308 stepy = PNG_PASS_ROW_OFFSET(pass);
3309 }
3310
3311 else
3312 {
3313 y = 0;
3314 startx = 0;
3315 stepx = channels;
3316 stepy = 1;
3317 }
3318
3319 for (; y<height; y += stepy)
3320 {
3321 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3322 png_bytep outrow;
3323 png_const_bytep end_row;
3324
3325 /* Read the row, which is packed: */
3326 png_read_row(png_ptr, inrow, NULL);
3327
3328 outrow = png_voidcast(png_bytep, display->first_row);
3329 outrow += y * step_row;
3330 end_row = outrow + width * channels;
3331
3332 /* Now do the composition on each pixel in this row. */
3333 outrow += startx;
3334 for (; outrow < end_row; outrow += stepx)
3335 {
3336 png_byte alpha = inrow[channels];
3337
3338 if (alpha > 0) /* else no change to the output */
3339 {
3340 unsigned int c;
3341
3342 for (c=0; c<channels; ++c)
3343 {
3344 png_uint_32 component = inrow[c];
3345
3346 if (alpha < 255) /* else just use component */
3347 {
3348 /* This is PNG_OPTIMIZED_ALPHA, the component value
3349 * is a linear 8-bit value. Combine this with the
3350 * current outrow[c] value which is sRGB encoded.
3351 * Arithmetic here is 16-bits to preserve the output
3352 * values correctly.
3353 */
3354 component *= 257*255; /* =65535 */
3355 component += (255-alpha)*png_sRGB_table[outrow[c]];
3356
3357 /* So 'component' is scaled by 255*65535 and is
3358 * therefore appropriate for the sRGB to linear
3359 * conversion table.
3360 */
3361 component = PNG_sRGB_FROM_LINEAR(component);
3362 }
3363
3364 outrow[c] = (png_byte)component;
3365 }
3366 }
3367
3368 inrow += channels+1; /* components and alpha channel */
3369 }
3370 }
3371 }
3372 }
3373
3374 return 1;
3375 }
3376
3377 /* The do_local_background case; called when all the following transforms are to
3378 * be done:
3379 *
3380 * PNG_RGB_TO_GRAY
3381 * PNG_COMPOSITE
3382 * PNG_GAMMA
3383 *
3384 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3385 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3386 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3387 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3388 * row and handles the removal or pre-multiplication of the alpha channel.
3389 */
3390 static int
3391 png_image_read_background(png_voidp argument)
3392 {
3393 png_image_read_control *display = png_voidcast(png_image_read_control*,
3394 argument);
3395 png_imagep image = display->image;
3396 png_structrp png_ptr = image->opaque->png_ptr;
3397 png_inforp info_ptr = image->opaque->info_ptr;
3398 png_uint_32 height = image->height;
3399 png_uint_32 width = image->width;
3400 int pass, passes;
3401
3402 /* Double check the convoluted logic below. We expect to get here with
3403 * libpng doing rgb to gray and gamma correction but background processing
3404 * left to the png_image_read_background function. The rows libpng produce
3405 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3406 */
3407 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3408 png_error(png_ptr, "lost rgb to gray");
3409
3410 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3411 png_error(png_ptr, "unexpected compose");
3412
3413 if (png_get_channels(png_ptr, info_ptr) != 2)
3414 png_error(png_ptr, "lost/gained channels");
3415
3416 /* Expect the 8-bit case to always remove the alpha channel */
3417 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3418 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3419 png_error(png_ptr, "unexpected 8-bit transformation");
3420
3421 switch (png_ptr->interlaced)
3422 {
3423 case PNG_INTERLACE_NONE:
3424 passes = 1;
3425 break;
3426
3427 case PNG_INTERLACE_ADAM7:
3428 passes = PNG_INTERLACE_ADAM7_PASSES;
3429 break;
3430
3431 default:
3432 png_error(png_ptr, "unknown interlace type");
3433 }
3434
3435 /* Use direct access to info_ptr here because otherwise the simplified API
3436 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3437 * checking the value after libpng expansions, not the original value in the
3438 * PNG.
3439 */
3440 switch (info_ptr->bit_depth)
3441 {
3442 case 8:
3443 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3444 * to be removed by composing on a background: either the row if
3445 * display->background is NULL or display->background->green if not.
3446 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3447 */
3448 {
3449 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3450 ptrdiff_t step_row = display->row_bytes;
3451
3452 for (pass = 0; pass < passes; ++pass)
3453 {
3454 png_bytep row = png_voidcast(png_bytep,
3455 display->first_row);
3456 unsigned int startx, stepx, stepy;
3457 png_uint_32 y;
3458
3459 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3460 {
3461 /* The row may be empty for a short image: */
3462 if (PNG_PASS_COLS(width, pass) == 0)
3463 continue;
3464
3465 startx = PNG_PASS_START_COL(pass);
3466 stepx = PNG_PASS_COL_OFFSET(pass);
3467 y = PNG_PASS_START_ROW(pass);
3468 stepy = PNG_PASS_ROW_OFFSET(pass);
3469 }
3470
3471 else
3472 {
3473 y = 0;
3474 startx = 0;
3475 stepx = stepy = 1;
3476 }
3477
3478 if (display->background == NULL)
3479 {
3480 for (; y<height; y += stepy)
3481 {
3482 png_bytep inrow = png_voidcast(png_bytep,
3483 display->local_row);
3484 png_bytep outrow = first_row + y * step_row;
3485 png_const_bytep end_row = outrow + width;
3486
3487 /* Read the row, which is packed: */
3488 png_read_row(png_ptr, inrow, NULL);
3489
3490 /* Now do the composition on each pixel in this row. */
3491 outrow += startx;
3492 for (; outrow < end_row; outrow += stepx)
3493 {
3494 png_byte alpha = inrow[1];
3495
3496 if (alpha > 0) /* else no change to the output */
3497 {
3498 png_uint_32 component = inrow[0];
3499
3500 if (alpha < 255) /* else just use component */
3501 {
3502 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3503 * necessary to invert the sRGB transfer
3504 * function and multiply the alpha out.
3505 */
3506 component = png_sRGB_table[component] * alpha;
3507 component += png_sRGB_table[outrow[0]] *
3508 (255-alpha);
3509 component = PNG_sRGB_FROM_LINEAR(component);
3510 }
3511
3512 outrow[0] = (png_byte)component;
3513 }
3514
3515 inrow += 2; /* gray and alpha channel */
3516 }
3517 }
3518 }
3519
3520 else /* constant background value */
3521 {
3522 png_byte background8 = display->background->green;
3523 png_uint_16 background = png_sRGB_table[background8];
3524
3525 for (; y<height; y += stepy)
3526 {
3527 png_bytep inrow = png_voidcast(png_bytep,
3528 display->local_row);
3529 png_bytep outrow = first_row + y * step_row;
3530 png_const_bytep end_row = outrow + width;
3531
3532 /* Read the row, which is packed: */
3533 png_read_row(png_ptr, inrow, NULL);
3534
3535 /* Now do the composition on each pixel in this row. */
3536 outrow += startx;
3537 for (; outrow < end_row; outrow += stepx)
3538 {
3539 png_byte alpha = inrow[1];
3540
3541 if (alpha > 0) /* else use background */
3542 {
3543 png_uint_32 component = inrow[0];
3544
3545 if (alpha < 255) /* else just use component */
3546 {
3547 component = png_sRGB_table[component] * alpha;
3548 component += background * (255-alpha);
3549 component = PNG_sRGB_FROM_LINEAR(component);
3550 }
3551
3552 outrow[0] = (png_byte)component;
3553 }
3554
3555 else
3556 outrow[0] = background8;
3557
3558 inrow += 2; /* gray and alpha channel */
3559 }
3560
3561 row += display->row_bytes;
3562 }
3563 }
3564 }
3565 }
3566 break;
3567
3568 case 16:
3569 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3570 * still be done and, maybe, the alpha channel removed. This code also
3571 * handles the alpha-first option.
3572 */
3573 {
3574 png_uint_16p first_row = png_voidcast(png_uint_16p,
3575 display->first_row);
3576 /* The division by two is safe because the caller passed in a
3577 * stride which was multiplied by 2 (below) to get row_bytes.
3578 */
3579 ptrdiff_t step_row = display->row_bytes / 2;
3580 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
3581 unsigned int outchannels = 1+preserve_alpha;
3582 int swap_alpha = 0;
3583
3584 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3585 if (preserve_alpha != 0 &&
3586 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3587 swap_alpha = 1;
3588 # endif
3589
3590 for (pass = 0; pass < passes; ++pass)
3591 {
3592 unsigned int startx, stepx, stepy;
3593 png_uint_32 y;
3594
3595 /* The 'x' start and step are adjusted to output components here.
3596 */
3597 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3598 {
3599 /* The row may be empty for a short image: */
3600 if (PNG_PASS_COLS(width, pass) == 0)
3601 continue;
3602
3603 startx = PNG_PASS_START_COL(pass) * outchannels;
3604 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3605 y = PNG_PASS_START_ROW(pass);
3606 stepy = PNG_PASS_ROW_OFFSET(pass);
3607 }
3608
3609 else
3610 {
3611 y = 0;
3612 startx = 0;
3613 stepx = outchannels;
3614 stepy = 1;
3615 }
3616
3617 for (; y<height; y += stepy)
3618 {
3619 png_const_uint_16p inrow;
3620 png_uint_16p outrow = first_row + y*step_row;
3621 png_uint_16p end_row = outrow + width * outchannels;
3622
3623 /* Read the row, which is packed: */
3624 png_read_row(png_ptr, png_voidcast(png_bytep,
3625 display->local_row), NULL);
3626 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3627
3628 /* Now do the pre-multiplication on each pixel in this row.
3629 */
3630 outrow += startx;
3631 for (; outrow < end_row; outrow += stepx)
3632 {
3633 png_uint_32 component = inrow[0];
3634 png_uint_16 alpha = inrow[1];
3635
3636 if (alpha > 0) /* else 0 */
3637 {
3638 if (alpha < 65535) /* else just use component */
3639 {
3640 component *= alpha;
3641 component += 32767;
3642 component /= 65535;
3643 }
3644 }
3645
3646 else
3647 component = 0;
3648
3649 outrow[swap_alpha] = (png_uint_16)component;
3650 if (preserve_alpha != 0)
3651 outrow[1 ^ swap_alpha] = alpha;
3652
3653 inrow += 2; /* components and alpha channel */
3654 }
3655 }
3656 }
3657 }
3658 break;
3659
3660 #ifdef __GNUC__
3661 default:
3662 png_error(png_ptr, "unexpected bit depth");
3663 #endif
3664 }
3665
3666 return 1;
3667 }
3668
3669 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3670 static int
3671 png_image_read_direct(png_voidp argument)
3672 {
3673 png_image_read_control *display = png_voidcast(png_image_read_control*,
3674 argument);
3675 png_imagep image = display->image;
3676 png_structrp png_ptr = image->opaque->png_ptr;
3677 png_inforp info_ptr = image->opaque->info_ptr;
3678
3679 png_uint_32 format = image->format;
3680 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3681 int do_local_compose = 0;
3682 int do_local_background = 0; /* to avoid double gamma correction bug */
3683 int passes = 0;
3684
3685 /* Add transforms to ensure the correct output format is produced then check
3686 * that the required implementation support is there. Always expand; always
3687 * need 8 bits minimum, no palette and expanded tRNS.
3688 */
3689 png_set_expand(png_ptr);
3690
3691 /* Now check the format to see if it was modified. */
3692 {
3693 png_uint_32 base_format = png_image_format(png_ptr) &
3694 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3695 png_uint_32 change = format ^ base_format;
3696 png_fixed_point output_gamma;
3697 int mode; /* alpha mode */
3698
3699 /* Do this first so that we have a record if rgb to gray is happening. */
3700 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3701 {
3702 /* gray<->color transformation required. */
3703 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3704 png_set_gray_to_rgb(png_ptr);
3705
3706 else
3707 {
3708 /* libpng can't do both rgb to gray and
3709 * background/pre-multiplication if there is also significant gamma
3710 * correction, because both operations require linear colors and
3711 * the code only supports one transform doing the gamma correction.
3712 * Handle this by doing the pre-multiplication or background
3713 * operation in this code, if necessary.
3714 *
3715 * TODO: fix this by rewriting pngrtran.c (!)
3716 *
3717 * For the moment (given that fixing this in pngrtran.c is an
3718 * enormous change) 'do_local_background' is used to indicate that
3719 * the problem exists.
3720 */
3721 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3722 do_local_background = 1/*maybe*/;
3723
3724 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3725 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3726 }
3727
3728 change &= ~PNG_FORMAT_FLAG_COLOR;
3729 }
3730
3731 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3732 */
3733 {
3734 png_fixed_point input_gamma_default;
3735
3736 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3737 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3738 input_gamma_default = PNG_GAMMA_LINEAR;
3739 else
3740 input_gamma_default = PNG_DEFAULT_sRGB;
3741
3742 /* Call png_set_alpha_mode to set the default for the input gamma; the
3743 * output gamma is set by a second call below.
3744 */
3745 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3746 }
3747
3748 if (linear != 0)
3749 {
3750 /* If there *is* an alpha channel in the input it must be multiplied
3751 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3752 */
3753 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3754 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3755
3756 else
3757 mode = PNG_ALPHA_PNG;
3758
3759 output_gamma = PNG_GAMMA_LINEAR;
3760 }
3761
3762 else
3763 {
3764 mode = PNG_ALPHA_PNG;
3765 output_gamma = PNG_DEFAULT_sRGB;
3766 }
3767
3768 /* If 'do_local_background' is set check for the presence of gamma
3769 * correction; this is part of the work-round for the libpng bug
3770 * described above.
3771 *
3772 * TODO: fix libpng and remove this.
3773 */
3774 if (do_local_background != 0)
3775 {
3776 png_fixed_point gtest;
3777
3778 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3779 * gamma correction, the screen gamma hasn't been set on png_struct
3780 * yet; it's set below. png_struct::gamma, however, is set to the
3781 * final value.
3782 */
3783 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3784 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3785 do_local_background = 0;
3786
3787 else if (mode == PNG_ALPHA_STANDARD)
3788 {
3789 do_local_background = 2/*required*/;
3790 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3791 }
3792
3793 /* else leave as 1 for the checks below */
3794 }
3795
3796 /* If the bit-depth changes then handle that here. */
3797 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3798 {
3799 if (linear != 0 /*16-bit output*/)
3800 png_set_expand_16(png_ptr);
3801
3802 else /* 8-bit output */
3803 png_set_scale_16(png_ptr);
3804
3805 change &= ~PNG_FORMAT_FLAG_LINEAR;
3806 }
3807
3808 /* Now the background/alpha channel changes. */
3809 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3810 {
3811 /* Removing an alpha channel requires composition for the 8-bit
3812 * formats; for the 16-bit it is already done, above, by the
3813 * pre-multiplication and the channel just needs to be stripped.
3814 */
3815 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3816 {
3817 /* If RGB->gray is happening the alpha channel must be left and the
3818 * operation completed locally.
3819 *
3820 * TODO: fix libpng and remove this.
3821 */
3822 if (do_local_background != 0)
3823 do_local_background = 2/*required*/;
3824
3825 /* 16-bit output: just remove the channel */
3826 else if (linear != 0) /* compose on black (well, pre-multiply) */
3827 png_set_strip_alpha(png_ptr);
3828
3829 /* 8-bit output: do an appropriate compose */
3830 else if (display->background != NULL)
3831 {
3832 png_color_16 c;
3833
3834 c.index = 0; /*unused*/
3835 c.red = display->background->red;
3836 c.green = display->background->green;
3837 c.blue = display->background->blue;
3838 c.gray = display->background->green;
3839
3840 /* This is always an 8-bit sRGB value, using the 'green' channel
3841 * for gray is much better than calculating the luminance here;
3842 * we can get off-by-one errors in that calculation relative to
3843 * the app expectations and that will show up in transparent
3844 * pixels.
3845 */
3846 png_set_background_fixed(png_ptr, &c,
3847 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3848 0/*gamma: not used*/);
3849 }
3850
3851 else /* compose on row: implemented below. */
3852 {
3853 do_local_compose = 1;
3854 /* This leaves the alpha channel in the output, so it has to be
3855 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3856 * one so the code only has to hack on the pixels that require
3857 * composition.
3858 */
3859 mode = PNG_ALPHA_OPTIMIZED;
3860 }
3861 }
3862
3863 else /* output needs an alpha channel */
3864 {
3865 /* This is tricky because it happens before the swap operation has
3866 * been accomplished; however, the swap does *not* swap the added
3867 * alpha channel (weird API), so it must be added in the correct
3868 * place.
3869 */
3870 png_uint_32 filler; /* opaque filler */
3871 int where;
3872
3873 if (linear != 0)
3874 filler = 65535;
3875
3876 else
3877 filler = 255;
3878
3879 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3880 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3881 {
3882 where = PNG_FILLER_BEFORE;
3883 change &= ~PNG_FORMAT_FLAG_AFIRST;
3884 }
3885
3886 else
3887 # endif
3888 where = PNG_FILLER_AFTER;
3889
3890 png_set_add_alpha(png_ptr, filler, where);
3891 }
3892
3893 /* This stops the (irrelevant) call to swap_alpha below. */
3894 change &= ~PNG_FORMAT_FLAG_ALPHA;
3895 }
3896
3897 /* Now set the alpha mode correctly; this is always done, even if there is
3898 * no alpha channel in either the input or the output because it correctly
3899 * sets the output gamma.
3900 */
3901 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3902
3903 # ifdef PNG_FORMAT_BGR_SUPPORTED
3904 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3905 {
3906 /* Check only the output format; PNG is never BGR; don't do this if
3907 * the output is gray, but fix up the 'format' value in that case.
3908 */
3909 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3910 png_set_bgr(png_ptr);
3911
3912 else
3913 format &= ~PNG_FORMAT_FLAG_BGR;
3914
3915 change &= ~PNG_FORMAT_FLAG_BGR;
3916 }
3917 # endif
3918
3919 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3920 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3921 {
3922 /* Only relevant if there is an alpha channel - it's particularly
3923 * important to handle this correctly because do_local_compose may
3924 * be set above and then libpng will keep the alpha channel for this
3925 * code to remove.
3926 */
3927 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3928 {
3929 /* Disable this if doing a local background,
3930 * TODO: remove this when local background is no longer required.
3931 */
3932 if (do_local_background != 2)
3933 png_set_swap_alpha(png_ptr);
3934 }
3935
3936 else
3937 format &= ~PNG_FORMAT_FLAG_AFIRST;
3938
3939 change &= ~PNG_FORMAT_FLAG_AFIRST;
3940 }
3941 # endif
3942
3943 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3944 * architecture.
3945 */
3946 if (linear != 0)
3947 {
3948 PNG_CONST png_uint_16 le = 0x0001;
3949
3950 if ((*(png_const_bytep) & le) != 0)
3951 png_set_swap(png_ptr);
3952 }
3953
3954 /* If change is not now 0 some transformation is missing - error out. */
3955 if (change != 0)
3956 png_error(png_ptr, "png_read_image: unsupported transformation");
3957 }
3958
3959 PNG_SKIP_CHUNKS(png_ptr);
3960
3961 /* Update the 'info' structure and make sure the result is as required; first
3962 * make sure to turn on the interlace handling if it will be required
3963 * (because it can't be turned on *after* the call to png_read_update_info!)
3964 *
3965 * TODO: remove the do_local_background fixup below.
3966 */
3967 if (do_local_compose == 0 && do_local_background != 2)
3968 passes = png_set_interlace_handling(png_ptr);
3969
3970 png_read_update_info(png_ptr, info_ptr);
3971
3972 {
3973 png_uint_32 info_format = 0;
3974
3975 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
3976 info_format |= PNG_FORMAT_FLAG_COLOR;
3977
3978 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
3979 {
3980 /* do_local_compose removes this channel below. */
3981 if (do_local_compose == 0)
3982 {
3983 /* do_local_background does the same if required. */
3984 if (do_local_background != 2 ||
3985 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
3986 info_format |= PNG_FORMAT_FLAG_ALPHA;
3987 }
3988 }
3989
3990 else if (do_local_compose != 0) /* internal error */
3991 png_error(png_ptr, "png_image_read: alpha channel lost");
3992
3993 if (info_ptr->bit_depth == 16)
3994 info_format |= PNG_FORMAT_FLAG_LINEAR;
3995
3996 # ifdef PNG_FORMAT_BGR_SUPPORTED
3997 if ((png_ptr->transformations & PNG_BGR) != 0)
3998 info_format |= PNG_FORMAT_FLAG_BGR;
3999 # endif
4000
4001 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
4002 if (do_local_background == 2)
4003 {
4004 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4005 info_format |= PNG_FORMAT_FLAG_AFIRST;
4006 }
4007
4008 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4009 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4010 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4011 {
4012 if (do_local_background == 2)
4013 png_error(png_ptr, "unexpected alpha swap transformation");
4014
4015 info_format |= PNG_FORMAT_FLAG_AFIRST;
4016 }
4017 # endif
4018
4019 /* This is actually an internal error. */
4020 if (info_format != format)
4021 png_error(png_ptr, "png_read_image: invalid transformations");
4022 }
4023
4024 /* Now read the rows. If do_local_compose is set then it is necessary to use
4025 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4026 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4027 * display acts as a flag.
4028 */
4029 {
4030 png_voidp first_row = display->buffer;
4031 ptrdiff_t row_bytes = display->row_stride;
4032
4033 if (linear != 0)
4034 row_bytes *= 2;
4035
4036 /* The following expression is designed to work correctly whether it gives
4037 * a signed or an unsigned result.
4038 */
4039 if (row_bytes < 0)
4040 {
4041 char *ptr = png_voidcast(char*, first_row);
4042 ptr += (image->height-1) * (-row_bytes);
4043 first_row = png_voidcast(png_voidp, ptr);
4044 }
4045
4046 display->first_row = first_row;
4047 display->row_bytes = row_bytes;
4048 }
4049
4050 if (do_local_compose != 0)
4051 {
4052 int result;
4053 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4054
4055 display->local_row = row;
4056 result = png_safe_execute(image, png_image_read_composite, display);
4057 display->local_row = NULL;
4058 png_free(png_ptr, row);
4059
4060 return result;
4061 }
4062
4063 else if (do_local_background == 2)
4064 {
4065 int result;
4066 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4067
4068 display->local_row = row;
4069 result = png_safe_execute(image, png_image_read_background, display);
4070 display->local_row = NULL;
4071 png_free(png_ptr, row);
4072
4073 return result;
4074 }
4075
4076 else
4077 {
4078 png_alloc_size_t row_bytes = display->row_bytes;
4079
4080 while (--passes >= 0)
4081 {
4082 png_uint_32 y = image->height;
4083 png_bytep row = png_voidcast(png_bytep, display->first_row);
4084
4085 while (y-- > 0)
4086 {
4087 png_read_row(png_ptr, row, NULL);
4088 row += row_bytes;
4089 }
4090 }
4091
4092 return 1;
4093 }
4094 }
4095
4096 int PNGAPI
4097 png_image_finish_read(png_imagep image, png_const_colorp background,
4098 void *buffer, png_int_32 row_stride, void *colormap)
4099 {
4100 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4101 {
4102 png_uint_32 check;
4103
4104 if (row_stride == 0)
4105 row_stride = PNG_IMAGE_ROW_STRIDE(*image);
4106
4107 if (row_stride < 0)
4108 check = -row_stride;
4109
4110 else
4111 check = row_stride;
4112
4113 if (image->opaque != NULL && buffer != NULL &&
4114 check >= PNG_IMAGE_ROW_STRIDE(*image))
4115 {
4116 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4117 (image->colormap_entries > 0 && colormap != NULL))
4118 {
4119 int result;
4120 png_image_read_control display;
4121
4122 memset(&display, 0, (sizeof display));
4123 display.image = image;
4124 display.buffer = buffer;
4125 display.row_stride = row_stride;
4126 display.colormap = colormap;
4127 display.background = background;
4128 display.local_row = NULL;
4129
4130 /* Choose the correct 'end' routine; for the color-map case all the
4131 * setup has already been done.
4132 */
4133 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4134 result =
4135 png_safe_execute(image, png_image_read_colormap, &display) &&
4136 png_safe_execute(image, png_image_read_colormapped, &display);
4137
4138 else
4139 result =
4140 png_safe_execute(image, png_image_read_direct, &display);
4141
4142 png_image_free(image);
4143 return result;
4144 }
4145
4146 else
4147 return png_image_error(image,
4148 "png_image_finish_read[color-map]: no color-map");
4149 }
4150
4151 else
4152 return png_image_error(image,
4153 "png_image_finish_read: invalid argument");
4154 }
4155
4156 else if (image != NULL)
4157 return png_image_error(image,
4158 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4159
4160 return 0;
4161 }
4162
4163 #endif /* SIMPLIFIED_READ */
4164 #endif /* READ */