1
2 /* pngread.c - read a PNG file
3 *
4 * Copyright (c) 2018-2019 Cosmin Truta
5 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
6 * Copyright (c) 1996-1997 Andreas Dilger
7 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
8 *
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
12 *
13 * This file contains routines that an application calls directly to
14 * read a PNG file or stream.
15 */
16
17 #include "pngpriv.h"
18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
19 # include <errno.h>
20 #endif
21
22 #ifdef PNG_READ_SUPPORTED
23
24 /* Create a PNG structure for reading, and allocate any memory needed. */
25 PNG_FUNCTION(png_structp,PNGAPI
26 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
28 {
29 #ifndef PNG_USER_MEM_SUPPORTED
30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
31 error_fn, warn_fn, NULL, NULL, NULL);
32 #else
33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
34 warn_fn, NULL, NULL, NULL);
35 }
36
37 /* Alternate create PNG structure for reading, and allocate any memory
38 * needed.
39 */
40 PNG_FUNCTION(png_structp,PNGAPI
41 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
44 {
45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
47 #endif /* USER_MEM */
48
49 if (png_ptr != NULL)
50 {
51 png_ptr->mode = PNG_IS_READ_STRUCT;
52
53 /* Added in libpng-1.6.0; this can be used to detect a read structure if
54 * required (it will be zero in a write structure.)
55 */
56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
58 # endif
59
60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
62
63 /* In stable builds only warn if an application error can be completely
64 * handled.
65 */
66 # if PNG_RELEASE_BUILD
67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
68 # endif
69 # endif
70
71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
72 * do it itself) avoiding setting the default function if it is not
73 * required.
74 */
75 png_set_read_fn(png_ptr, NULL, NULL);
76 }
77
78 return png_ptr;
79 }
80
81
82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83 /* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
90 */
91 void PNGAPI
png_read_info(png_structrp png_ptr,png_inforp info_ptr)92 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
93 {
94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
95 int keep;
96 #endif
97
98 png_debug(1, "in png_read_info");
99
100 if (png_ptr == NULL || info_ptr == NULL)
101 return;
102
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr, info_ptr);
105
106 for (;;)
107 {
108 png_uint_32 length = png_read_chunk_header(png_ptr);
109 png_uint_32 chunk_name = png_ptr->chunk_name;
110
111 /* IDAT logic needs to happen here to simplify getting the two flags
112 * right.
113 */
114 if (chunk_name == png_IDAT)
115 {
116 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
117 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
118
119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
120 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
121 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
122
123 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
124 png_chunk_benign_error(png_ptr, "Too many IDATs found");
125
126 png_ptr->mode |= PNG_HAVE_IDAT;
127 }
128
129 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
130 {
131 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
132 png_ptr->mode |= PNG_AFTER_IDAT;
133 }
134
135 /* This should be a binary subdivision search or a hash for
136 * matching the chunk name rather than a linear search.
137 */
138 if (chunk_name == png_IHDR)
139 png_handle_IHDR(png_ptr, info_ptr, length);
140
141 else if (chunk_name == png_IEND)
142 png_handle_IEND(png_ptr, info_ptr, length);
143
144 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
145 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
146 {
147 png_handle_unknown(png_ptr, info_ptr, length, keep);
148
149 if (chunk_name == png_PLTE)
150 png_ptr->mode |= PNG_HAVE_PLTE;
151
152 else if (chunk_name == png_IDAT)
153 {
154 png_ptr->idat_size = 0; /* It has been consumed */
155 break;
156 }
157 }
158 #endif
159 else if (chunk_name == png_PLTE)
160 png_handle_PLTE(png_ptr, info_ptr, length);
161
162 else if (chunk_name == png_IDAT)
163 {
164 #ifdef PNG_READ_APNG_SUPPORTED
165 png_have_info(png_ptr, info_ptr);
166 #endif
167 png_ptr->idat_size = length;
168 break;
169 }
170
171 #ifdef PNG_READ_bKGD_SUPPORTED
172 else if (chunk_name == png_bKGD)
173 png_handle_bKGD(png_ptr, info_ptr, length);
174 #endif
175
176 #ifdef PNG_READ_cHRM_SUPPORTED
177 else if (chunk_name == png_cHRM)
178 png_handle_cHRM(png_ptr, info_ptr, length);
179 #endif
180
181 #ifdef PNG_READ_eXIf_SUPPORTED
182 else if (chunk_name == png_eXIf)
183 png_handle_eXIf(png_ptr, info_ptr, length);
184 #endif
185
186 #ifdef PNG_READ_gAMA_SUPPORTED
187 else if (chunk_name == png_gAMA)
188 png_handle_gAMA(png_ptr, info_ptr, length);
189 #endif
190
191 #ifdef PNG_READ_hIST_SUPPORTED
192 else if (chunk_name == png_hIST)
193 png_handle_hIST(png_ptr, info_ptr, length);
194 #endif
195
196 #ifdef PNG_READ_oFFs_SUPPORTED
197 else if (chunk_name == png_oFFs)
198 png_handle_oFFs(png_ptr, info_ptr, length);
199 #endif
200
201 #ifdef PNG_READ_pCAL_SUPPORTED
202 else if (chunk_name == png_pCAL)
203 png_handle_pCAL(png_ptr, info_ptr, length);
204 #endif
205
206 #ifdef PNG_READ_sCAL_SUPPORTED
207 else if (chunk_name == png_sCAL)
208 png_handle_sCAL(png_ptr, info_ptr, length);
209 #endif
210
211 #ifdef PNG_READ_pHYs_SUPPORTED
212 else if (chunk_name == png_pHYs)
213 png_handle_pHYs(png_ptr, info_ptr, length);
214 #endif
215
216 #ifdef PNG_READ_sBIT_SUPPORTED
217 else if (chunk_name == png_sBIT)
218 png_handle_sBIT(png_ptr, info_ptr, length);
219 #endif
220
221 #ifdef PNG_READ_sRGB_SUPPORTED
222 else if (chunk_name == png_sRGB)
223 png_handle_sRGB(png_ptr, info_ptr, length);
224 #endif
225
226 #ifdef PNG_READ_iCCP_SUPPORTED
227 else if (chunk_name == png_iCCP)
228 png_handle_iCCP(png_ptr, info_ptr, length);
229 #endif
230
231 #ifdef PNG_READ_sPLT_SUPPORTED
232 else if (chunk_name == png_sPLT)
233 png_handle_sPLT(png_ptr, info_ptr, length);
234 #endif
235
236 #ifdef PNG_READ_tEXt_SUPPORTED
237 else if (chunk_name == png_tEXt)
238 png_handle_tEXt(png_ptr, info_ptr, length);
239 #endif
240
241 #ifdef PNG_READ_tIME_SUPPORTED
242 else if (chunk_name == png_tIME)
243 png_handle_tIME(png_ptr, info_ptr, length);
244 #endif
245
246 #ifdef PNG_READ_tRNS_SUPPORTED
247 else if (chunk_name == png_tRNS)
248 png_handle_tRNS(png_ptr, info_ptr, length);
249 #endif
250
251 #ifdef PNG_READ_zTXt_SUPPORTED
252 else if (chunk_name == png_zTXt)
253 png_handle_zTXt(png_ptr, info_ptr, length);
254 #endif
255
256 #ifdef PNG_READ_iTXt_SUPPORTED
257 else if (chunk_name == png_iTXt)
258 png_handle_iTXt(png_ptr, info_ptr, length);
259 #endif
260
261 #ifdef PNG_READ_APNG_SUPPORTED
262 else if (chunk_name == png_acTL)
263 png_handle_acTL(png_ptr, info_ptr, length);
264
265 else if (chunk_name == png_fcTL)
266 png_handle_fcTL(png_ptr, info_ptr, length);
267
268 else if (chunk_name == png_fdAT)
269 png_handle_fdAT(png_ptr, info_ptr, length);
270 #endif
271
272 else
273 png_handle_unknown(png_ptr, info_ptr, length,
274 PNG_HANDLE_CHUNK_AS_DEFAULT);
275 }
276 }
277 #endif /* SEQUENTIAL_READ */
278
279 #ifdef PNG_READ_APNG_SUPPORTED
280 void PNGAPI
png_read_frame_head(png_structp png_ptr,png_infop info_ptr)281 png_read_frame_head(png_structp png_ptr, png_infop info_ptr)
282 {
283 png_byte have_chunk_after_DAT; /* after IDAT or after fdAT */
284
285 png_debug(0, "Reading frame head");
286
287 if ((png_ptr->mode & PNG_HAVE_acTL) == 0)
288 png_error(png_ptr, "attempt to png_read_frame_head() but "
289 "no acTL present");
290
291 /* do nothing for the main IDAT */
292 if (png_ptr->num_frames_read == 0)
293 return;
294
295 png_read_reset(png_ptr);
296 png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
297 png_ptr->mode &= ~PNG_HAVE_fcTL;
298
299 have_chunk_after_DAT = 0;
300 for (;;)
301 {
302 png_uint_32 length = png_read_chunk_header(png_ptr);
303
304 if (png_ptr->chunk_name == png_IDAT)
305 {
306 /* discard trailing IDATs for the first frame */
307 if (have_chunk_after_DAT != 0 || png_ptr->num_frames_read > 1)
308 png_error(png_ptr, "png_read_frame_head(): out of place IDAT");
309 png_crc_finish(png_ptr, length);
310 }
311
312 else if (png_ptr->chunk_name == png_fcTL)
313 {
314 png_handle_fcTL(png_ptr, info_ptr, length);
315 have_chunk_after_DAT = 1;
316 }
317
318 else if (png_ptr->chunk_name == png_fdAT)
319 {
320 png_ensure_sequence_number(png_ptr, length);
321
322 /* discard trailing fdATs for frames other than the first */
323 if (have_chunk_after_DAT == 0 && png_ptr->num_frames_read > 1)
324 png_crc_finish(png_ptr, length - 4);
325 else if (png_ptr->mode & PNG_HAVE_fcTL)
326 {
327 png_ptr->idat_size = length - 4;
328 png_ptr->mode |= PNG_HAVE_IDAT;
329
330 break;
331 }
332 else
333 png_error(png_ptr, "png_read_frame_head(): out of place fdAT");
334 }
335 else
336 {
337 png_warning(png_ptr, "Skipped (ignored) a chunk "
338 "between APNG chunks");
339 png_crc_finish(png_ptr, length);
340 }
341 }
342 }
343 #endif /* READ_APNG */
344
345 /* Optional call to update the users info_ptr structure */
346 void PNGAPI
png_read_update_info(png_structrp png_ptr,png_inforp info_ptr)347 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
348 {
349 png_debug(1, "in png_read_update_info");
350
351 if (png_ptr != NULL)
352 {
353 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
354 {
355 png_read_start_row(png_ptr);
356
357 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
358 png_read_transform_info(png_ptr, info_ptr);
359 # else
360 PNG_UNUSED(info_ptr)
361 # endif
362 }
363
364 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
365 else
366 png_app_error(png_ptr,
367 "png_read_update_info/png_start_read_image: duplicate call");
368 }
369 }
370
371 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
372 /* Initialize palette, background, etc, after transformations
373 * are set, but before any reading takes place. This allows
374 * the user to obtain a gamma-corrected palette, for example.
375 * If the user doesn't call this, we will do it ourselves.
376 */
377 void PNGAPI
png_start_read_image(png_structrp png_ptr)378 png_start_read_image(png_structrp png_ptr)
379 {
380 png_debug(1, "in png_start_read_image");
381
382 if (png_ptr != NULL)
383 {
384 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
385 png_read_start_row(png_ptr);
386
387 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
388 else
389 png_app_error(png_ptr,
390 "png_start_read_image/png_read_update_info: duplicate call");
391 }
392 }
393 #endif /* SEQUENTIAL_READ */
394
395 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
396 #ifdef PNG_MNG_FEATURES_SUPPORTED
397 /* Undoes intrapixel differencing,
398 * NOTE: this is apparently only supported in the 'sequential' reader.
399 */
400 static void
png_do_read_intrapixel(png_row_infop row_info,png_bytep row)401 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
402 {
403 png_debug(1, "in png_do_read_intrapixel");
404
405 if (
406 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
407 {
408 int bytes_per_pixel;
409 png_uint_32 row_width = row_info->width;
410
411 if (row_info->bit_depth == 8)
412 {
413 png_bytep rp;
414 png_uint_32 i;
415
416 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
417 bytes_per_pixel = 3;
418
419 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
420 bytes_per_pixel = 4;
421
422 else
423 return;
424
425 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
426 {
427 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
428 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
429 }
430 }
431 else if (row_info->bit_depth == 16)
432 {
433 png_bytep rp;
434 png_uint_32 i;
435
436 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
437 bytes_per_pixel = 6;
438
439 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
440 bytes_per_pixel = 8;
441
442 else
443 return;
444
445 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
446 {
447 png_uint_32 s0 = (png_uint_32)(*(rp ) << 8) | *(rp + 1);
448 png_uint_32 s1 = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
449 png_uint_32 s2 = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
450 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
451 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
452 *(rp ) = (png_byte)((red >> 8) & 0xff);
453 *(rp + 1) = (png_byte)(red & 0xff);
454 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
455 *(rp + 5) = (png_byte)(blue & 0xff);
456 }
457 }
458 }
459 }
460 #endif /* MNG_FEATURES */
461
462 void PNGAPI
png_read_row(png_structrp png_ptr,png_bytep row,png_bytep dsp_row)463 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
464 {
465 png_row_info row_info;
466
467 if (png_ptr == NULL)
468 return;
469
470 png_debug2(1, "in png_read_row (row %lu, pass %d)",
471 (unsigned long)png_ptr->row_number, png_ptr->pass);
472
473 /* png_read_start_row sets the information (in particular iwidth) for this
474 * interlace pass.
475 */
476 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
477 png_read_start_row(png_ptr);
478
479 /* 1.5.6: row_info moved out of png_struct to a local here. */
480 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
481 row_info.color_type = png_ptr->color_type;
482 row_info.bit_depth = png_ptr->bit_depth;
483 row_info.channels = png_ptr->channels;
484 row_info.pixel_depth = png_ptr->pixel_depth;
485 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
486
487 #ifdef PNG_WARNINGS_SUPPORTED
488 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
489 {
490 /* Check for transforms that have been set but were defined out */
491 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
492 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
493 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
494 #endif
495
496 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
497 if ((png_ptr->transformations & PNG_FILLER) != 0)
498 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
499 #endif
500
501 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
502 !defined(PNG_READ_PACKSWAP_SUPPORTED)
503 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
504 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
505 #endif
506
507 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
508 if ((png_ptr->transformations & PNG_PACK) != 0)
509 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
510 #endif
511
512 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
513 if ((png_ptr->transformations & PNG_SHIFT) != 0)
514 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
515 #endif
516
517 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
518 if ((png_ptr->transformations & PNG_BGR) != 0)
519 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
520 #endif
521
522 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
523 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
524 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
525 #endif
526 }
527 #endif /* WARNINGS */
528
529 #ifdef PNG_READ_INTERLACING_SUPPORTED
530 /* If interlaced and we do not need a new row, combine row and return.
531 * Notice that the pixels we have from previous rows have been transformed
532 * already; we can only combine like with like (transformed or
533 * untransformed) and, because of the libpng API for interlaced images, this
534 * means we must transform before de-interlacing.
535 */
536 if (png_ptr->interlaced != 0 &&
537 (png_ptr->transformations & PNG_INTERLACE) != 0)
538 {
539 switch (png_ptr->pass)
540 {
541 case 0:
542 if (png_ptr->row_number & 0x07)
543 {
544 if (dsp_row != NULL)
545 png_combine_row(png_ptr, dsp_row, 1/*display*/);
546 png_read_finish_row(png_ptr);
547 return;
548 }
549 break;
550
551 case 1:
552 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
553 {
554 if (dsp_row != NULL)
555 png_combine_row(png_ptr, dsp_row, 1/*display*/);
556
557 png_read_finish_row(png_ptr);
558 return;
559 }
560 break;
561
562 case 2:
563 if ((png_ptr->row_number & 0x07) != 4)
564 {
565 if (dsp_row != NULL && (png_ptr->row_number & 4))
566 png_combine_row(png_ptr, dsp_row, 1/*display*/);
567
568 png_read_finish_row(png_ptr);
569 return;
570 }
571 break;
572
573 case 3:
574 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
575 {
576 if (dsp_row != NULL)
577 png_combine_row(png_ptr, dsp_row, 1/*display*/);
578
579 png_read_finish_row(png_ptr);
580 return;
581 }
582 break;
583
584 case 4:
585 if ((png_ptr->row_number & 3) != 2)
586 {
587 if (dsp_row != NULL && (png_ptr->row_number & 2))
588 png_combine_row(png_ptr, dsp_row, 1/*display*/);
589
590 png_read_finish_row(png_ptr);
591 return;
592 }
593 break;
594
595 case 5:
596 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
597 {
598 if (dsp_row != NULL)
599 png_combine_row(png_ptr, dsp_row, 1/*display*/);
600
601 png_read_finish_row(png_ptr);
602 return;
603 }
604 break;
605
606 default:
607 case 6:
608 if ((png_ptr->row_number & 1) == 0)
609 {
610 png_read_finish_row(png_ptr);
611 return;
612 }
613 break;
614 }
615 }
616 #endif
617
618 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
619 png_error(png_ptr, "Invalid attempt to read row data");
620
621 /* Fill the row with IDAT data: */
622 png_ptr->row_buf[0]=255; /* to force error if no data was found */
623 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
624
625 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
626 {
627 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
628 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
629 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
630 else
631 png_error(png_ptr, "bad adaptive filter value");
632 }
633
634 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
635 * 1.5.6, while the buffer really is this big in current versions of libpng
636 * it may not be in the future, so this was changed just to copy the
637 * interlaced count:
638 */
639 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
640
641 #ifdef PNG_MNG_FEATURES_SUPPORTED
642 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
643 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
644 {
645 /* Intrapixel differencing */
646 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
647 }
648 #endif
649
650 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
651 if (png_ptr->transformations)
652 png_do_read_transformations(png_ptr, &row_info);
653 #endif
654
655 /* The transformed pixel depth should match the depth now in row_info. */
656 if (png_ptr->transformed_pixel_depth == 0)
657 {
658 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
659 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
660 png_error(png_ptr, "sequential row overflow");
661 }
662
663 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
664 png_error(png_ptr, "internal sequential row size calculation error");
665
666 #ifdef PNG_READ_INTERLACING_SUPPORTED
667 /* Expand interlaced rows to full size */
668 if (png_ptr->interlaced != 0 &&
669 (png_ptr->transformations & PNG_INTERLACE) != 0)
670 {
671 if (png_ptr->pass < 6)
672 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
673 png_ptr->transformations);
674
675 if (dsp_row != NULL)
676 png_combine_row(png_ptr, dsp_row, 1/*display*/);
677
678 if (row != NULL)
679 png_combine_row(png_ptr, row, 0/*row*/);
680 }
681
682 else
683 #endif
684 {
685 if (row != NULL)
686 png_combine_row(png_ptr, row, -1/*ignored*/);
687
688 if (dsp_row != NULL)
689 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
690 }
691 png_read_finish_row(png_ptr);
692
693 if (png_ptr->read_row_fn != NULL)
694 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
695
696 }
697 #endif /* SEQUENTIAL_READ */
698
699 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
700 /* Read one or more rows of image data. If the image is interlaced,
701 * and png_set_interlace_handling() has been called, the rows need to
702 * contain the contents of the rows from the previous pass. If the
703 * image has alpha or transparency, and png_handle_alpha()[*] has been
704 * called, the rows contents must be initialized to the contents of the
705 * screen.
706 *
707 * "row" holds the actual image, and pixels are placed in it
708 * as they arrive. If the image is displayed after each pass, it will
709 * appear to "sparkle" in. "display_row" can be used to display a
710 * "chunky" progressive image, with finer detail added as it becomes
711 * available. If you do not want this "chunky" display, you may pass
712 * NULL for display_row. If you do not want the sparkle display, and
713 * you have not called png_handle_alpha(), you may pass NULL for rows.
714 * If you have called png_handle_alpha(), and the image has either an
715 * alpha channel or a transparency chunk, you must provide a buffer for
716 * rows. In this case, you do not have to provide a display_row buffer
717 * also, but you may. If the image is not interlaced, or if you have
718 * not called png_set_interlace_handling(), the display_row buffer will
719 * be ignored, so pass NULL to it.
720 *
721 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
722 */
723
724 void PNGAPI
png_read_rows(png_structrp png_ptr,png_bytepp row,png_bytepp display_row,png_uint_32 num_rows)725 png_read_rows(png_structrp png_ptr, png_bytepp row,
726 png_bytepp display_row, png_uint_32 num_rows)
727 {
728 png_uint_32 i;
729 png_bytepp rp;
730 png_bytepp dp;
731
732 png_debug(1, "in png_read_rows");
733
734 if (png_ptr == NULL)
735 return;
736
737 rp = row;
738 dp = display_row;
739 if (rp != NULL && dp != NULL)
740 for (i = 0; i < num_rows; i++)
741 {
742 png_bytep rptr = *rp++;
743 png_bytep dptr = *dp++;
744
745 png_read_row(png_ptr, rptr, dptr);
746 }
747
748 else if (rp != NULL)
749 for (i = 0; i < num_rows; i++)
750 {
751 png_bytep rptr = *rp;
752 png_read_row(png_ptr, rptr, NULL);
753 rp++;
754 }
755
756 else if (dp != NULL)
757 for (i = 0; i < num_rows; i++)
758 {
759 png_bytep dptr = *dp;
760 png_read_row(png_ptr, NULL, dptr);
761 dp++;
762 }
763 }
764 #endif /* SEQUENTIAL_READ */
765
766 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
767 /* Read the entire image. If the image has an alpha channel or a tRNS
768 * chunk, and you have called png_handle_alpha()[*], you will need to
769 * initialize the image to the current image that PNG will be overlaying.
770 * We set the num_rows again here, in case it was incorrectly set in
771 * png_read_start_row() by a call to png_read_update_info() or
772 * png_start_read_image() if png_set_interlace_handling() wasn't called
773 * prior to either of these functions like it should have been. You can
774 * only call this function once. If you desire to have an image for
775 * each pass of a interlaced image, use png_read_rows() instead.
776 *
777 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
778 */
779 void PNGAPI
png_read_image(png_structrp png_ptr,png_bytepp image)780 png_read_image(png_structrp png_ptr, png_bytepp image)
781 {
782 png_uint_32 i, image_height;
783 int pass, j;
784 png_bytepp rp;
785
786 png_debug(1, "in png_read_image");
787
788 if (png_ptr == NULL)
789 return;
790
791 #ifdef PNG_READ_INTERLACING_SUPPORTED
792 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
793 {
794 pass = png_set_interlace_handling(png_ptr);
795 /* And make sure transforms are initialized. */
796 png_start_read_image(png_ptr);
797 }
798 else
799 {
800 if (png_ptr->interlaced != 0 &&
801 (png_ptr->transformations & PNG_INTERLACE) == 0)
802 {
803 /* Caller called png_start_read_image or png_read_update_info without
804 * first turning on the PNG_INTERLACE transform. We can fix this here,
805 * but the caller should do it!
806 */
807 png_warning(png_ptr, "Interlace handling should be turned on when "
808 "using png_read_image");
809 /* Make sure this is set correctly */
810 png_ptr->num_rows = png_ptr->height;
811 }
812
813 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
814 * the above error case.
815 */
816 pass = png_set_interlace_handling(png_ptr);
817 }
818 #else
819 if (png_ptr->interlaced)
820 png_error(png_ptr,
821 "Cannot read interlaced image -- interlace handler disabled");
822
823 pass = 1;
824 #endif
825
826 image_height=png_ptr->height;
827
828 for (j = 0; j < pass; j++)
829 {
830 rp = image;
831 for (i = 0; i < image_height; i++)
832 {
833 png_read_row(png_ptr, *rp, NULL);
834 rp++;
835 }
836 }
837 }
838 #endif /* SEQUENTIAL_READ */
839
840 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
841 /* Read the end of the PNG file. Will not read past the end of the
842 * file, will verify the end is accurate, and will read any comments
843 * or time information at the end of the file, if info is not NULL.
844 */
845 void PNGAPI
png_read_end(png_structrp png_ptr,png_inforp info_ptr)846 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
847 {
848 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
849 int keep;
850 #endif
851
852 png_debug(1, "in png_read_end");
853
854 if (png_ptr == NULL)
855 return;
856
857 /* If png_read_end is called in the middle of reading the rows there may
858 * still be pending IDAT data and an owned zstream. Deal with this here.
859 */
860 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
861 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
862 #endif
863 png_read_finish_IDAT(png_ptr);
864
865 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
866 /* Report invalid palette index; added at libng-1.5.10 */
867 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
868 png_ptr->num_palette_max > png_ptr->num_palette)
869 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
870 #endif
871
872 do
873 {
874 png_uint_32 length = png_read_chunk_header(png_ptr);
875 png_uint_32 chunk_name = png_ptr->chunk_name;
876
877 if (chunk_name != png_IDAT)
878 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
879
880 if (chunk_name == png_IEND)
881 png_handle_IEND(png_ptr, info_ptr, length);
882
883 else if (chunk_name == png_IHDR)
884 png_handle_IHDR(png_ptr, info_ptr, length);
885
886 else if (info_ptr == NULL)
887 png_crc_finish(png_ptr, length);
888
889 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
890 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
891 {
892 if (chunk_name == png_IDAT)
893 {
894 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
895 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
896 png_benign_error(png_ptr, ".Too many IDATs found");
897 }
898 png_handle_unknown(png_ptr, info_ptr, length, keep);
899 if (chunk_name == png_PLTE)
900 png_ptr->mode |= PNG_HAVE_PLTE;
901 }
902 #endif
903
904 else if (chunk_name == png_IDAT)
905 {
906 /* Zero length IDATs are legal after the last IDAT has been
907 * read, but not after other chunks have been read. 1.6 does not
908 * always read all the deflate data; specifically it cannot be relied
909 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
910 * chunks which are longer than zero as well:
911 */
912 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
913 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
914 png_benign_error(png_ptr, "..Too many IDATs found");
915
916 png_crc_finish(png_ptr, length);
917 }
918 else if (chunk_name == png_PLTE)
919 png_handle_PLTE(png_ptr, info_ptr, length);
920
921 #ifdef PNG_READ_bKGD_SUPPORTED
922 else if (chunk_name == png_bKGD)
923 png_handle_bKGD(png_ptr, info_ptr, length);
924 #endif
925
926 #ifdef PNG_READ_cHRM_SUPPORTED
927 else if (chunk_name == png_cHRM)
928 png_handle_cHRM(png_ptr, info_ptr, length);
929 #endif
930
931 #ifdef PNG_READ_eXIf_SUPPORTED
932 else if (chunk_name == png_eXIf)
933 png_handle_eXIf(png_ptr, info_ptr, length);
934 #endif
935
936 #ifdef PNG_READ_gAMA_SUPPORTED
937 else if (chunk_name == png_gAMA)
938 png_handle_gAMA(png_ptr, info_ptr, length);
939 #endif
940
941 #ifdef PNG_READ_hIST_SUPPORTED
942 else if (chunk_name == png_hIST)
943 png_handle_hIST(png_ptr, info_ptr, length);
944 #endif
945
946 #ifdef PNG_READ_oFFs_SUPPORTED
947 else if (chunk_name == png_oFFs)
948 png_handle_oFFs(png_ptr, info_ptr, length);
949 #endif
950
951 #ifdef PNG_READ_pCAL_SUPPORTED
952 else if (chunk_name == png_pCAL)
953 png_handle_pCAL(png_ptr, info_ptr, length);
954 #endif
955
956 #ifdef PNG_READ_sCAL_SUPPORTED
957 else if (chunk_name == png_sCAL)
958 png_handle_sCAL(png_ptr, info_ptr, length);
959 #endif
960
961 #ifdef PNG_READ_pHYs_SUPPORTED
962 else if (chunk_name == png_pHYs)
963 png_handle_pHYs(png_ptr, info_ptr, length);
964 #endif
965
966 #ifdef PNG_READ_sBIT_SUPPORTED
967 else if (chunk_name == png_sBIT)
968 png_handle_sBIT(png_ptr, info_ptr, length);
969 #endif
970
971 #ifdef PNG_READ_sRGB_SUPPORTED
972 else if (chunk_name == png_sRGB)
973 png_handle_sRGB(png_ptr, info_ptr, length);
974 #endif
975
976 #ifdef PNG_READ_iCCP_SUPPORTED
977 else if (chunk_name == png_iCCP)
978 png_handle_iCCP(png_ptr, info_ptr, length);
979 #endif
980
981 #ifdef PNG_READ_sPLT_SUPPORTED
982 else if (chunk_name == png_sPLT)
983 png_handle_sPLT(png_ptr, info_ptr, length);
984 #endif
985
986 #ifdef PNG_READ_tEXt_SUPPORTED
987 else if (chunk_name == png_tEXt)
988 png_handle_tEXt(png_ptr, info_ptr, length);
989 #endif
990
991 #ifdef PNG_READ_tIME_SUPPORTED
992 else if (chunk_name == png_tIME)
993 png_handle_tIME(png_ptr, info_ptr, length);
994 #endif
995
996 #ifdef PNG_READ_tRNS_SUPPORTED
997 else if (chunk_name == png_tRNS)
998 png_handle_tRNS(png_ptr, info_ptr, length);
999 #endif
1000
1001 #ifdef PNG_READ_zTXt_SUPPORTED
1002 else if (chunk_name == png_zTXt)
1003 png_handle_zTXt(png_ptr, info_ptr, length);
1004 #endif
1005
1006 #ifdef PNG_READ_iTXt_SUPPORTED
1007 else if (chunk_name == png_iTXt)
1008 png_handle_iTXt(png_ptr, info_ptr, length);
1009 #endif
1010
1011 else
1012 png_handle_unknown(png_ptr, info_ptr, length,
1013 PNG_HANDLE_CHUNK_AS_DEFAULT);
1014 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
1015 }
1016 #endif /* SEQUENTIAL_READ */
1017
1018 /* Free all memory used in the read struct */
1019 static void
png_read_destroy(png_structrp png_ptr)1020 png_read_destroy(png_structrp png_ptr)
1021 {
1022 png_debug(1, "in png_read_destroy");
1023
1024 #ifdef PNG_READ_GAMMA_SUPPORTED
1025 png_destroy_gamma_table(png_ptr);
1026 #endif
1027
1028 png_free(png_ptr, png_ptr->big_row_buf);
1029 png_ptr->big_row_buf = NULL;
1030 png_free(png_ptr, png_ptr->big_prev_row);
1031 png_ptr->big_prev_row = NULL;
1032 png_free(png_ptr, png_ptr->read_buffer);
1033 png_ptr->read_buffer = NULL;
1034
1035 #ifdef PNG_READ_QUANTIZE_SUPPORTED
1036 png_free(png_ptr, png_ptr->palette_lookup);
1037 png_ptr->palette_lookup = NULL;
1038 png_free(png_ptr, png_ptr->quantize_index);
1039 png_ptr->quantize_index = NULL;
1040 #endif
1041
1042 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
1043 {
1044 png_zfree(png_ptr, png_ptr->palette);
1045 png_ptr->palette = NULL;
1046 }
1047 png_ptr->free_me &= ~PNG_FREE_PLTE;
1048
1049 #if defined(PNG_tRNS_SUPPORTED) || \
1050 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
1051 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
1052 {
1053 png_free(png_ptr, png_ptr->trans_alpha);
1054 png_ptr->trans_alpha = NULL;
1055 }
1056 png_ptr->free_me &= ~PNG_FREE_TRNS;
1057 #endif
1058
1059 inflateEnd(&png_ptr->zstream);
1060
1061 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
1062 png_free(png_ptr, png_ptr->save_buffer);
1063 png_ptr->save_buffer = NULL;
1064 #endif
1065
1066 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
1067 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
1068 png_free(png_ptr, png_ptr->unknown_chunk.data);
1069 png_ptr->unknown_chunk.data = NULL;
1070 #endif
1071
1072 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
1073 png_free(png_ptr, png_ptr->chunk_list);
1074 png_ptr->chunk_list = NULL;
1075 #endif
1076
1077 #if defined(PNG_READ_EXPAND_SUPPORTED) && \
1078 defined(PNG_ARM_NEON_IMPLEMENTATION)
1079 png_free(png_ptr, png_ptr->riffled_palette);
1080 png_ptr->riffled_palette = NULL;
1081 #endif
1082
1083 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1084 * callbacks are still set at this point. They are required to complete the
1085 * destruction of the png_struct itself.
1086 */
1087 }
1088
1089 /* Free all memory used by the read */
1090 void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr,png_infopp info_ptr_ptr,png_infopp end_info_ptr_ptr)1091 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1092 png_infopp end_info_ptr_ptr)
1093 {
1094 png_structrp png_ptr = NULL;
1095
1096 png_debug(1, "in png_destroy_read_struct");
1097
1098 if (png_ptr_ptr != NULL)
1099 png_ptr = *png_ptr_ptr;
1100
1101 if (png_ptr == NULL)
1102 return;
1103
1104 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1105 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1106 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1107 */
1108 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1109 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1110
1111 *png_ptr_ptr = NULL;
1112 png_read_destroy(png_ptr);
1113 png_destroy_png_struct(png_ptr);
1114 }
1115
1116 void PNGAPI
png_set_read_status_fn(png_structrp png_ptr,png_read_status_ptr read_row_fn)1117 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1118 {
1119 if (png_ptr == NULL)
1120 return;
1121
1122 png_ptr->read_row_fn = read_row_fn;
1123 }
1124
1125
1126 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1127 #ifdef PNG_INFO_IMAGE_SUPPORTED
1128 void PNGAPI
png_read_png(png_structrp png_ptr,png_inforp info_ptr,int transforms,voidp params)1129 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1130 int transforms, voidp params)
1131 {
1132 if (png_ptr == NULL || info_ptr == NULL)
1133 return;
1134
1135 /* png_read_info() gives us all of the information from the
1136 * PNG file before the first IDAT (image data chunk).
1137 */
1138 png_read_info(png_ptr, info_ptr);
1139 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1140 png_error(png_ptr, "Image is too high to process with png_read_png()");
1141
1142 /* -------------- image transformations start here ------------------- */
1143 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1144 * is not implemented. This will only happen in de-configured (non-default)
1145 * libpng builds. The results can be unexpected - png_read_png may return
1146 * short or mal-formed rows because the transform is skipped.
1147 */
1148
1149 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1150 */
1151 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1152 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1153 * did in earlier versions, while "scale_16" is now more accurate.
1154 */
1155 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1156 png_set_scale_16(png_ptr);
1157 #else
1158 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1159 #endif
1160
1161 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1162 * latter by doing SCALE first. This is ok and allows apps not to check for
1163 * which is supported to get the right answer.
1164 */
1165 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1166 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1167 png_set_strip_16(png_ptr);
1168 #else
1169 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1170 #endif
1171
1172 /* Strip alpha bytes from the input data without combining with
1173 * the background (not recommended).
1174 */
1175 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1176 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1177 png_set_strip_alpha(png_ptr);
1178 #else
1179 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1180 #endif
1181
1182 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1183 * byte into separate bytes (useful for paletted and grayscale images).
1184 */
1185 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1186 #ifdef PNG_READ_PACK_SUPPORTED
1187 png_set_packing(png_ptr);
1188 #else
1189 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1190 #endif
1191
1192 /* Change the order of packed pixels to least significant bit first
1193 * (not useful if you are using png_set_packing).
1194 */
1195 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1196 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1197 png_set_packswap(png_ptr);
1198 #else
1199 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1200 #endif
1201
1202 /* Expand paletted colors into true RGB triplets
1203 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1204 * Expand paletted or RGB images with transparency to full alpha
1205 * channels so the data will be available as RGBA quartets.
1206 */
1207 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1208 #ifdef PNG_READ_EXPAND_SUPPORTED
1209 png_set_expand(png_ptr);
1210 #else
1211 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1212 #endif
1213
1214 /* We don't handle background color or gamma transformation or quantizing.
1215 */
1216
1217 /* Invert monochrome files to have 0 as white and 1 as black
1218 */
1219 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1220 #ifdef PNG_READ_INVERT_SUPPORTED
1221 png_set_invert_mono(png_ptr);
1222 #else
1223 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1224 #endif
1225
1226 /* If you want to shift the pixel values from the range [0,255] or
1227 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1228 * colors were originally in:
1229 */
1230 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1231 #ifdef PNG_READ_SHIFT_SUPPORTED
1232 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1233 png_set_shift(png_ptr, &info_ptr->sig_bit);
1234 #else
1235 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1236 #endif
1237
1238 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1239 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1240 #ifdef PNG_READ_BGR_SUPPORTED
1241 png_set_bgr(png_ptr);
1242 #else
1243 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1244 #endif
1245
1246 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1247 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1248 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1249 png_set_swap_alpha(png_ptr);
1250 #else
1251 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1252 #endif
1253
1254 /* Swap bytes of 16-bit files to least significant byte first */
1255 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1256 #ifdef PNG_READ_SWAP_SUPPORTED
1257 png_set_swap(png_ptr);
1258 #else
1259 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1260 #endif
1261
1262 /* Added at libpng-1.2.41 */
1263 /* Invert the alpha channel from opacity to transparency */
1264 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1265 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1266 png_set_invert_alpha(png_ptr);
1267 #else
1268 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1269 #endif
1270
1271 /* Added at libpng-1.2.41 */
1272 /* Expand grayscale image to RGB */
1273 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1274 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1275 png_set_gray_to_rgb(png_ptr);
1276 #else
1277 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1278 #endif
1279
1280 /* Added at libpng-1.5.4 */
1281 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1282 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1283 png_set_expand_16(png_ptr);
1284 #else
1285 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1286 #endif
1287
1288 /* We don't handle adding filler bytes */
1289
1290 /* We use png_read_image and rely on that for interlace handling, but we also
1291 * call png_read_update_info therefore must turn on interlace handling now:
1292 */
1293 (void)png_set_interlace_handling(png_ptr);
1294
1295 /* Optional call to gamma correct and add the background to the palette
1296 * and update info structure. REQUIRED if you are expecting libpng to
1297 * update the palette for you (i.e., you selected such a transform above).
1298 */
1299 png_read_update_info(png_ptr, info_ptr);
1300
1301 /* -------------- image transformations end here ------------------- */
1302
1303 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1304 if (info_ptr->row_pointers == NULL)
1305 {
1306 png_uint_32 iptr;
1307
1308 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1309 info_ptr->height * (sizeof (png_bytep))));
1310
1311 for (iptr=0; iptr<info_ptr->height; iptr++)
1312 info_ptr->row_pointers[iptr] = NULL;
1313
1314 info_ptr->free_me |= PNG_FREE_ROWS;
1315
1316 for (iptr = 0; iptr < info_ptr->height; iptr++)
1317 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1318 png_malloc(png_ptr, info_ptr->rowbytes));
1319 }
1320
1321 png_read_image(png_ptr, info_ptr->row_pointers);
1322 info_ptr->valid |= PNG_INFO_IDAT;
1323
1324 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1325 png_read_end(png_ptr, info_ptr);
1326
1327 PNG_UNUSED(params)
1328 }
1329 #endif /* INFO_IMAGE */
1330 #endif /* SEQUENTIAL_READ */
1331
1332 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1333 /* SIMPLIFIED READ
1334 *
1335 * This code currently relies on the sequential reader, though it could easily
1336 * be made to work with the progressive one.
1337 */
1338 /* Arguments to png_image_finish_read: */
1339
1340 /* Encoding of PNG data (used by the color-map code) */
1341 # define P_NOTSET 0 /* File encoding not yet known */
1342 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1343 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1344 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1345 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1346
1347 /* Color-map processing: after libpng has run on the PNG image further
1348 * processing may be needed to convert the data to color-map indices.
1349 */
1350 #define PNG_CMAP_NONE 0
1351 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1352 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1353 #define PNG_CMAP_RGB 3 /* Process RGB data */
1354 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1355
1356 /* The following document where the background is for each processing case. */
1357 #define PNG_CMAP_NONE_BACKGROUND 256
1358 #define PNG_CMAP_GA_BACKGROUND 231
1359 #define PNG_CMAP_TRANS_BACKGROUND 254
1360 #define PNG_CMAP_RGB_BACKGROUND 256
1361 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1362
1363 typedef struct
1364 {
1365 /* Arguments: */
1366 png_imagep image;
1367 png_voidp buffer;
1368 png_int_32 row_stride;
1369 png_voidp colormap;
1370 png_const_colorp background;
1371 /* Local variables: */
1372 png_voidp local_row;
1373 png_voidp first_row;
1374 ptrdiff_t row_bytes; /* step between rows */
1375 int file_encoding; /* E_ values above */
1376 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1377 int colormap_processing; /* PNG_CMAP_ values above */
1378 } png_image_read_control;
1379
1380 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1381 * called, so setting up the jmp_buf is not required. This means that anything
1382 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1383 * instead so that control is returned safely back to this routine.
1384 */
1385 static int
png_image_read_init(png_imagep image)1386 png_image_read_init(png_imagep image)
1387 {
1388 if (image->opaque == NULL)
1389 {
1390 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1391 png_safe_error, png_safe_warning);
1392
1393 /* And set the rest of the structure to NULL to ensure that the various
1394 * fields are consistent.
1395 */
1396 memset(image, 0, (sizeof *image));
1397 image->version = PNG_IMAGE_VERSION;
1398
1399 if (png_ptr != NULL)
1400 {
1401 png_infop info_ptr = png_create_info_struct(png_ptr);
1402
1403 if (info_ptr != NULL)
1404 {
1405 png_controlp control = png_voidcast(png_controlp,
1406 png_malloc_warn(png_ptr, (sizeof *control)));
1407
1408 if (control != NULL)
1409 {
1410 memset(control, 0, (sizeof *control));
1411
1412 control->png_ptr = png_ptr;
1413 control->info_ptr = info_ptr;
1414 control->for_write = 0;
1415
1416 image->opaque = control;
1417 return 1;
1418 }
1419
1420 /* Error clean up */
1421 png_destroy_info_struct(png_ptr, &info_ptr);
1422 }
1423
1424 png_destroy_read_struct(&png_ptr, NULL, NULL);
1425 }
1426
1427 return png_image_error(image, "png_image_read: out of memory");
1428 }
1429
1430 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1431 }
1432
1433 /* Utility to find the base format of a PNG file from a png_struct. */
1434 static png_uint_32
png_image_format(png_structrp png_ptr)1435 png_image_format(png_structrp png_ptr)
1436 {
1437 png_uint_32 format = 0;
1438
1439 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1440 format |= PNG_FORMAT_FLAG_COLOR;
1441
1442 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1443 format |= PNG_FORMAT_FLAG_ALPHA;
1444
1445 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1446 * sets the png_struct fields; that's all we are interested in here. The
1447 * precise interaction with an app call to png_set_tRNS and PNG file reading
1448 * is unclear.
1449 */
1450 else if (png_ptr->num_trans > 0)
1451 format |= PNG_FORMAT_FLAG_ALPHA;
1452
1453 if (png_ptr->bit_depth == 16)
1454 format |= PNG_FORMAT_FLAG_LINEAR;
1455
1456 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1457 format |= PNG_FORMAT_FLAG_COLORMAP;
1458
1459 return format;
1460 }
1461
1462 /* Is the given gamma significantly different from sRGB? The test is the same
1463 * one used in pngrtran.c when deciding whether to do gamma correction. The
1464 * arithmetic optimizes the division by using the fact that the inverse of the
1465 * file sRGB gamma is 2.2
1466 */
1467 static int
png_gamma_not_sRGB(png_fixed_point g)1468 png_gamma_not_sRGB(png_fixed_point g)
1469 {
1470 if (g < PNG_FP_1)
1471 {
1472 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1473 if (g == 0)
1474 return 0;
1475
1476 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1477 }
1478
1479 return 1;
1480 }
1481
1482 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1483 * header and fill in all the information. This is executed in a safe context,
1484 * unlike the init routine above.
1485 */
1486 static int
png_image_read_header(png_voidp argument)1487 png_image_read_header(png_voidp argument)
1488 {
1489 png_imagep image = png_voidcast(png_imagep, argument);
1490 png_structrp png_ptr = image->opaque->png_ptr;
1491 png_inforp info_ptr = image->opaque->info_ptr;
1492
1493 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
1494 png_set_benign_errors(png_ptr, 1/*warn*/);
1495 #endif
1496 png_read_info(png_ptr, info_ptr);
1497
1498 /* Do this the fast way; just read directly out of png_struct. */
1499 image->width = png_ptr->width;
1500 image->height = png_ptr->height;
1501
1502 {
1503 png_uint_32 format = png_image_format(png_ptr);
1504
1505 image->format = format;
1506
1507 #ifdef PNG_COLORSPACE_SUPPORTED
1508 /* Does the colorspace match sRGB? If there is no color endpoint
1509 * (colorant) information assume yes, otherwise require the
1510 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1511 * colorspace has been determined to be invalid ignore it.
1512 */
1513 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1514 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1515 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1516 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1517 #endif
1518 }
1519
1520 /* We need the maximum number of entries regardless of the format the
1521 * application sets here.
1522 */
1523 {
1524 png_uint_32 cmap_entries;
1525
1526 switch (png_ptr->color_type)
1527 {
1528 case PNG_COLOR_TYPE_GRAY:
1529 cmap_entries = 1U << png_ptr->bit_depth;
1530 break;
1531
1532 case PNG_COLOR_TYPE_PALETTE:
1533 cmap_entries = (png_uint_32)png_ptr->num_palette;
1534 break;
1535
1536 default:
1537 cmap_entries = 256;
1538 break;
1539 }
1540
1541 if (cmap_entries > 256)
1542 cmap_entries = 256;
1543
1544 image->colormap_entries = cmap_entries;
1545 }
1546
1547 return 1;
1548 }
1549
1550 #ifdef PNG_STDIO_SUPPORTED
1551 int PNGAPI
png_image_begin_read_from_stdio(png_imagep image,FILE * file)1552 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1553 {
1554 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1555 {
1556 if (file != NULL)
1557 {
1558 if (png_image_read_init(image) != 0)
1559 {
1560 /* This is slightly evil, but png_init_io doesn't do anything other
1561 * than this and we haven't changed the standard IO functions so
1562 * this saves a 'safe' function.
1563 */
1564 image->opaque->png_ptr->io_ptr = file;
1565 return png_safe_execute(image, png_image_read_header, image);
1566 }
1567 }
1568
1569 else
1570 return png_image_error(image,
1571 "png_image_begin_read_from_stdio: invalid argument");
1572 }
1573
1574 else if (image != NULL)
1575 return png_image_error(image,
1576 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1577
1578 return 0;
1579 }
1580
1581 int PNGAPI
png_image_begin_read_from_file(png_imagep image,const char * file_name)1582 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1583 {
1584 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1585 {
1586 if (file_name != NULL)
1587 {
1588 FILE *fp = fopen(file_name, "rb");
1589
1590 if (fp != NULL)
1591 {
1592 if (png_image_read_init(image) != 0)
1593 {
1594 image->opaque->png_ptr->io_ptr = fp;
1595 image->opaque->owned_file = 1;
1596 return png_safe_execute(image, png_image_read_header, image);
1597 }
1598
1599 /* Clean up: just the opened file. */
1600 (void)fclose(fp);
1601 }
1602
1603 else
1604 return png_image_error(image, strerror(errno));
1605 }
1606
1607 else
1608 return png_image_error(image,
1609 "png_image_begin_read_from_file: invalid argument");
1610 }
1611
1612 else if (image != NULL)
1613 return png_image_error(image,
1614 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1615
1616 return 0;
1617 }
1618 #endif /* STDIO */
1619
1620 static void PNGCBAPI
png_image_memory_read(png_structp png_ptr,png_bytep out,size_t need)1621 png_image_memory_read(png_structp png_ptr, png_bytep out, size_t need)
1622 {
1623 if (png_ptr != NULL)
1624 {
1625 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1626 if (image != NULL)
1627 {
1628 png_controlp cp = image->opaque;
1629 if (cp != NULL)
1630 {
1631 png_const_bytep memory = cp->memory;
1632 size_t size = cp->size;
1633
1634 if (memory != NULL && size >= need)
1635 {
1636 memcpy(out, memory, need);
1637 cp->memory = memory + need;
1638 cp->size = size - need;
1639 return;
1640 }
1641
1642 png_error(png_ptr, "read beyond end of data");
1643 }
1644 }
1645
1646 png_error(png_ptr, "invalid memory read");
1647 }
1648 }
1649
png_image_begin_read_from_memory(png_imagep image,png_const_voidp memory,size_t size)1650 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1651 png_const_voidp memory, size_t size)
1652 {
1653 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1654 {
1655 if (memory != NULL && size > 0)
1656 {
1657 if (png_image_read_init(image) != 0)
1658 {
1659 /* Now set the IO functions to read from the memory buffer and
1660 * store it into io_ptr. Again do this in-place to avoid calling a
1661 * libpng function that requires error handling.
1662 */
1663 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1664 image->opaque->size = size;
1665 image->opaque->png_ptr->io_ptr = image;
1666 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1667
1668 return png_safe_execute(image, png_image_read_header, image);
1669 }
1670 }
1671
1672 else
1673 return png_image_error(image,
1674 "png_image_begin_read_from_memory: invalid argument");
1675 }
1676
1677 else if (image != NULL)
1678 return png_image_error(image,
1679 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1680
1681 return 0;
1682 }
1683
1684 /* Utility function to skip chunks that are not used by the simplified image
1685 * read functions and an appropriate macro to call it.
1686 */
1687 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1688 static void
png_image_skip_unused_chunks(png_structrp png_ptr)1689 png_image_skip_unused_chunks(png_structrp png_ptr)
1690 {
1691 /* Prepare the reader to ignore all recognized chunks whose data will not
1692 * be used, i.e., all chunks recognized by libpng except for those
1693 * involved in basic image reading:
1694 *
1695 * IHDR, PLTE, IDAT, IEND
1696 *
1697 * Or image data handling:
1698 *
1699 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1700 *
1701 * This provides a small performance improvement and eliminates any
1702 * potential vulnerability to security problems in the unused chunks.
1703 *
1704 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1705 * too. This allows the simplified API to be compiled without iCCP support,
1706 * however if the support is there the chunk is still checked to detect
1707 * errors (which are unfortunately quite common.)
1708 */
1709 {
1710 static const png_byte chunks_to_process[] = {
1711 98, 75, 71, 68, '\0', /* bKGD */
1712 99, 72, 82, 77, '\0', /* cHRM */
1713 103, 65, 77, 65, '\0', /* gAMA */
1714 # ifdef PNG_READ_iCCP_SUPPORTED
1715 105, 67, 67, 80, '\0', /* iCCP */
1716 # endif
1717 115, 66, 73, 84, '\0', /* sBIT */
1718 115, 82, 71, 66, '\0', /* sRGB */
1719 };
1720
1721 /* Ignore unknown chunks and all other chunks except for the
1722 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1723 */
1724 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1725 NULL, -1);
1726
1727 /* But do not ignore image data handling chunks */
1728 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1729 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1730 }
1731 }
1732
1733 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1734 #else
1735 # define PNG_SKIP_CHUNKS(p) ((void)0)
1736 #endif /* HANDLE_AS_UNKNOWN */
1737
1738 /* The following macro gives the exact rounded answer for all values in the
1739 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1740 * the correct numbers 0..5
1741 */
1742 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1743
1744 /* Utility functions to make particular color-maps */
1745 static void
set_file_encoding(png_image_read_control * display)1746 set_file_encoding(png_image_read_control *display)
1747 {
1748 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1749 if (png_gamma_significant(g) != 0)
1750 {
1751 if (png_gamma_not_sRGB(g) != 0)
1752 {
1753 display->file_encoding = P_FILE;
1754 display->gamma_to_linear = png_reciprocal(g);
1755 }
1756
1757 else
1758 display->file_encoding = P_sRGB;
1759 }
1760
1761 else
1762 display->file_encoding = P_LINEAR8;
1763 }
1764
1765 static unsigned int
decode_gamma(png_image_read_control * display,png_uint_32 value,int encoding)1766 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1767 {
1768 if (encoding == P_FILE) /* double check */
1769 encoding = display->file_encoding;
1770
1771 if (encoding == P_NOTSET) /* must be the file encoding */
1772 {
1773 set_file_encoding(display);
1774 encoding = display->file_encoding;
1775 }
1776
1777 switch (encoding)
1778 {
1779 case P_FILE:
1780 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1781 break;
1782
1783 case P_sRGB:
1784 value = png_sRGB_table[value];
1785 break;
1786
1787 case P_LINEAR:
1788 break;
1789
1790 case P_LINEAR8:
1791 value *= 257;
1792 break;
1793
1794 #ifdef __GNUC__
1795 default:
1796 png_error(display->image->opaque->png_ptr,
1797 "unexpected encoding (internal error)");
1798 #endif
1799 }
1800
1801 return value;
1802 }
1803
1804 static png_uint_32
png_colormap_compose(png_image_read_control * display,png_uint_32 foreground,int foreground_encoding,png_uint_32 alpha,png_uint_32 background,int encoding)1805 png_colormap_compose(png_image_read_control *display,
1806 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1807 png_uint_32 background, int encoding)
1808 {
1809 /* The file value is composed on the background, the background has the given
1810 * encoding and so does the result, the file is encoded with P_FILE and the
1811 * file and alpha are 8-bit values. The (output) encoding will always be
1812 * P_LINEAR or P_sRGB.
1813 */
1814 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1815 png_uint_32 b = decode_gamma(display, background, encoding);
1816
1817 /* The alpha is always an 8-bit value (it comes from the palette), the value
1818 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1819 */
1820 f = f * alpha + b * (255-alpha);
1821
1822 if (encoding == P_LINEAR)
1823 {
1824 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1825 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1826 */
1827 f *= 257; /* Now scaled by 65535 */
1828 f += f >> 16;
1829 f = (f+32768) >> 16;
1830 }
1831
1832 else /* P_sRGB */
1833 f = PNG_sRGB_FROM_LINEAR(f);
1834
1835 return f;
1836 }
1837
1838 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1839 * be 8-bit.
1840 */
1841 static void
png_create_colormap_entry(png_image_read_control * display,png_uint_32 ip,png_uint_32 red,png_uint_32 green,png_uint_32 blue,png_uint_32 alpha,int encoding)1842 png_create_colormap_entry(png_image_read_control *display,
1843 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1844 png_uint_32 alpha, int encoding)
1845 {
1846 png_imagep image = display->image;
1847 int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1848 P_LINEAR : P_sRGB;
1849 int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1850 (red != green || green != blue);
1851
1852 if (ip > 255)
1853 png_error(image->opaque->png_ptr, "color-map index out of range");
1854
1855 /* Update the cache with whether the file gamma is significantly different
1856 * from sRGB.
1857 */
1858 if (encoding == P_FILE)
1859 {
1860 if (display->file_encoding == P_NOTSET)
1861 set_file_encoding(display);
1862
1863 /* Note that the cached value may be P_FILE too, but if it is then the
1864 * gamma_to_linear member has been set.
1865 */
1866 encoding = display->file_encoding;
1867 }
1868
1869 if (encoding == P_FILE)
1870 {
1871 png_fixed_point g = display->gamma_to_linear;
1872
1873 red = png_gamma_16bit_correct(red*257, g);
1874 green = png_gamma_16bit_correct(green*257, g);
1875 blue = png_gamma_16bit_correct(blue*257, g);
1876
1877 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1878 {
1879 alpha *= 257;
1880 encoding = P_LINEAR;
1881 }
1882
1883 else
1884 {
1885 red = PNG_sRGB_FROM_LINEAR(red * 255);
1886 green = PNG_sRGB_FROM_LINEAR(green * 255);
1887 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1888 encoding = P_sRGB;
1889 }
1890 }
1891
1892 else if (encoding == P_LINEAR8)
1893 {
1894 /* This encoding occurs quite frequently in test cases because PngSuite
1895 * includes a gAMA 1.0 chunk with most images.
1896 */
1897 red *= 257;
1898 green *= 257;
1899 blue *= 257;
1900 alpha *= 257;
1901 encoding = P_LINEAR;
1902 }
1903
1904 else if (encoding == P_sRGB &&
1905 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1906 {
1907 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1908 * linear.
1909 */
1910 red = png_sRGB_table[red];
1911 green = png_sRGB_table[green];
1912 blue = png_sRGB_table[blue];
1913 alpha *= 257;
1914 encoding = P_LINEAR;
1915 }
1916
1917 /* This is set if the color isn't gray but the output is. */
1918 if (encoding == P_LINEAR)
1919 {
1920 if (convert_to_Y != 0)
1921 {
1922 /* NOTE: these values are copied from png_do_rgb_to_gray */
1923 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1924 (png_uint_32)2366 * blue;
1925
1926 if (output_encoding == P_LINEAR)
1927 y = (y + 16384) >> 15;
1928
1929 else
1930 {
1931 /* y is scaled by 32768, we need it scaled by 255: */
1932 y = (y + 128) >> 8;
1933 y *= 255;
1934 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1935 alpha = PNG_DIV257(alpha);
1936 encoding = P_sRGB;
1937 }
1938
1939 blue = red = green = y;
1940 }
1941
1942 else if (output_encoding == P_sRGB)
1943 {
1944 red = PNG_sRGB_FROM_LINEAR(red * 255);
1945 green = PNG_sRGB_FROM_LINEAR(green * 255);
1946 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1947 alpha = PNG_DIV257(alpha);
1948 encoding = P_sRGB;
1949 }
1950 }
1951
1952 if (encoding != output_encoding)
1953 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1954
1955 /* Store the value. */
1956 {
1957 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1958 int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1959 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1960 # else
1961 # define afirst 0
1962 # endif
1963 # ifdef PNG_FORMAT_BGR_SUPPORTED
1964 int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1965 # else
1966 # define bgr 0
1967 # endif
1968
1969 if (output_encoding == P_LINEAR)
1970 {
1971 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1972
1973 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1974
1975 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1976 * value, if less than 65535 (this is, effectively, composite on black
1977 * if the alpha channel is removed.)
1978 */
1979 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1980 {
1981 case 4:
1982 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1983 /* FALLTHROUGH */
1984
1985 case 3:
1986 if (alpha < 65535)
1987 {
1988 if (alpha > 0)
1989 {
1990 blue = (blue * alpha + 32767U)/65535U;
1991 green = (green * alpha + 32767U)/65535U;
1992 red = (red * alpha + 32767U)/65535U;
1993 }
1994
1995 else
1996 red = green = blue = 0;
1997 }
1998 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1999 entry[afirst + 1] = (png_uint_16)green;
2000 entry[afirst + bgr] = (png_uint_16)red;
2001 break;
2002
2003 case 2:
2004 entry[1 ^ afirst] = (png_uint_16)alpha;
2005 /* FALLTHROUGH */
2006
2007 case 1:
2008 if (alpha < 65535)
2009 {
2010 if (alpha > 0)
2011 green = (green * alpha + 32767U)/65535U;
2012
2013 else
2014 green = 0;
2015 }
2016 entry[afirst] = (png_uint_16)green;
2017 break;
2018
2019 default:
2020 break;
2021 }
2022 }
2023
2024 else /* output encoding is P_sRGB */
2025 {
2026 png_bytep entry = png_voidcast(png_bytep, display->colormap);
2027
2028 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
2029
2030 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
2031 {
2032 case 4:
2033 entry[afirst ? 0 : 3] = (png_byte)alpha;
2034 /* FALLTHROUGH */
2035 case 3:
2036 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
2037 entry[afirst + 1] = (png_byte)green;
2038 entry[afirst + bgr] = (png_byte)red;
2039 break;
2040
2041 case 2:
2042 entry[1 ^ afirst] = (png_byte)alpha;
2043 /* FALLTHROUGH */
2044 case 1:
2045 entry[afirst] = (png_byte)green;
2046 break;
2047
2048 default:
2049 break;
2050 }
2051 }
2052
2053 # ifdef afirst
2054 # undef afirst
2055 # endif
2056 # ifdef bgr
2057 # undef bgr
2058 # endif
2059 }
2060 }
2061
2062 static int
make_gray_file_colormap(png_image_read_control * display)2063 make_gray_file_colormap(png_image_read_control *display)
2064 {
2065 unsigned int i;
2066
2067 for (i=0; i<256; ++i)
2068 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
2069
2070 return (int)i;
2071 }
2072
2073 static int
make_gray_colormap(png_image_read_control * display)2074 make_gray_colormap(png_image_read_control *display)
2075 {
2076 unsigned int i;
2077
2078 for (i=0; i<256; ++i)
2079 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
2080
2081 return (int)i;
2082 }
2083 #define PNG_GRAY_COLORMAP_ENTRIES 256
2084
2085 static int
make_ga_colormap(png_image_read_control * display)2086 make_ga_colormap(png_image_read_control *display)
2087 {
2088 unsigned int i, a;
2089
2090 /* Alpha is retained, the output will be a color-map with entries
2091 * selected by six levels of alpha. One transparent entry, 6 gray
2092 * levels for all the intermediate alpha values, leaving 230 entries
2093 * for the opaque grays. The color-map entries are the six values
2094 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2095 * relevant entry.
2096 *
2097 * if (alpha > 229) // opaque
2098 * {
2099 * // The 231 entries are selected to make the math below work:
2100 * base = 0;
2101 * entry = (231 * gray + 128) >> 8;
2102 * }
2103 * else if (alpha < 26) // transparent
2104 * {
2105 * base = 231;
2106 * entry = 0;
2107 * }
2108 * else // partially opaque
2109 * {
2110 * base = 226 + 6 * PNG_DIV51(alpha);
2111 * entry = PNG_DIV51(gray);
2112 * }
2113 */
2114 i = 0;
2115 while (i < 231)
2116 {
2117 unsigned int gray = (i * 256 + 115) / 231;
2118 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2119 }
2120
2121 /* 255 is used here for the component values for consistency with the code
2122 * that undoes premultiplication in pngwrite.c.
2123 */
2124 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2125
2126 for (a=1; a<5; ++a)
2127 {
2128 unsigned int g;
2129
2130 for (g=0; g<6; ++g)
2131 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2132 P_sRGB);
2133 }
2134
2135 return (int)i;
2136 }
2137
2138 #define PNG_GA_COLORMAP_ENTRIES 256
2139
2140 static int
make_rgb_colormap(png_image_read_control * display)2141 make_rgb_colormap(png_image_read_control *display)
2142 {
2143 unsigned int i, r;
2144
2145 /* Build a 6x6x6 opaque RGB cube */
2146 for (i=r=0; r<6; ++r)
2147 {
2148 unsigned int g;
2149
2150 for (g=0; g<6; ++g)
2151 {
2152 unsigned int b;
2153
2154 for (b=0; b<6; ++b)
2155 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2156 P_sRGB);
2157 }
2158 }
2159
2160 return (int)i;
2161 }
2162
2163 #define PNG_RGB_COLORMAP_ENTRIES 216
2164
2165 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2166 #define PNG_RGB_INDEX(r,g,b) \
2167 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2168
2169 static int
png_image_read_colormap(png_voidp argument)2170 png_image_read_colormap(png_voidp argument)
2171 {
2172 png_image_read_control *display =
2173 png_voidcast(png_image_read_control*, argument);
2174 png_imagep image = display->image;
2175
2176 png_structrp png_ptr = image->opaque->png_ptr;
2177 png_uint_32 output_format = image->format;
2178 int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2179 P_LINEAR : P_sRGB;
2180
2181 unsigned int cmap_entries;
2182 unsigned int output_processing; /* Output processing option */
2183 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2184
2185 /* Background information; the background color and the index of this color
2186 * in the color-map if it exists (else 256).
2187 */
2188 unsigned int background_index = 256;
2189 png_uint_32 back_r, back_g, back_b;
2190
2191 /* Flags to accumulate things that need to be done to the input. */
2192 int expand_tRNS = 0;
2193
2194 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2195 * very difficult to do, the results look awful, and it is difficult to see
2196 * what possible use it is because the application can't control the
2197 * color-map.
2198 */
2199 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2200 png_ptr->num_trans > 0) /* alpha in input */ &&
2201 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2202 {
2203 if (output_encoding == P_LINEAR) /* compose on black */
2204 back_b = back_g = back_r = 0;
2205
2206 else if (display->background == NULL /* no way to remove it */)
2207 png_error(png_ptr,
2208 "background color must be supplied to remove alpha/transparency");
2209
2210 /* Get a copy of the background color (this avoids repeating the checks
2211 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2212 * output format.
2213 */
2214 else
2215 {
2216 back_g = display->background->green;
2217 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2218 {
2219 back_r = display->background->red;
2220 back_b = display->background->blue;
2221 }
2222 else
2223 back_b = back_r = back_g;
2224 }
2225 }
2226
2227 else if (output_encoding == P_LINEAR)
2228 back_b = back_r = back_g = 65535;
2229
2230 else
2231 back_b = back_r = back_g = 255;
2232
2233 /* Default the input file gamma if required - this is necessary because
2234 * libpng assumes that if no gamma information is present the data is in the
2235 * output format, but the simplified API deduces the gamma from the input
2236 * format.
2237 */
2238 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2239 {
2240 /* Do this directly, not using the png_colorspace functions, to ensure
2241 * that it happens even if the colorspace is invalid (though probably if
2242 * it is the setting will be ignored) Note that the same thing can be
2243 * achieved at the application interface with png_set_gAMA.
2244 */
2245 if (png_ptr->bit_depth == 16 &&
2246 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2247 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2248
2249 else
2250 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2251
2252 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2253 }
2254
2255 /* Decide what to do based on the PNG color type of the input data. The
2256 * utility function png_create_colormap_entry deals with most aspects of the
2257 * output transformations; this code works out how to produce bytes of
2258 * color-map entries from the original format.
2259 */
2260 switch (png_ptr->color_type)
2261 {
2262 case PNG_COLOR_TYPE_GRAY:
2263 if (png_ptr->bit_depth <= 8)
2264 {
2265 /* There at most 256 colors in the output, regardless of
2266 * transparency.
2267 */
2268 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2269
2270 cmap_entries = 1U << png_ptr->bit_depth;
2271 if (cmap_entries > image->colormap_entries)
2272 png_error(png_ptr, "gray[8] color-map: too few entries");
2273
2274 step = 255 / (cmap_entries - 1);
2275 output_processing = PNG_CMAP_NONE;
2276
2277 /* If there is a tRNS chunk then this either selects a transparent
2278 * value or, if the output has no alpha, the background color.
2279 */
2280 if (png_ptr->num_trans > 0)
2281 {
2282 trans = png_ptr->trans_color.gray;
2283
2284 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2285 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2286 }
2287
2288 /* png_create_colormap_entry just takes an RGBA and writes the
2289 * corresponding color-map entry using the format from 'image',
2290 * including the required conversion to sRGB or linear as
2291 * appropriate. The input values are always either sRGB (if the
2292 * gamma correction flag is 0) or 0..255 scaled file encoded values
2293 * (if the function must gamma correct them).
2294 */
2295 for (i=val=0; i<cmap_entries; ++i, val += step)
2296 {
2297 /* 'i' is a file value. While this will result in duplicated
2298 * entries for 8-bit non-sRGB encoded files it is necessary to
2299 * have non-gamma corrected values to do tRNS handling.
2300 */
2301 if (i != trans)
2302 png_create_colormap_entry(display, i, val, val, val, 255,
2303 P_FILE/*8-bit with file gamma*/);
2304
2305 /* Else this entry is transparent. The colors don't matter if
2306 * there is an alpha channel (back_alpha == 0), but it does no
2307 * harm to pass them in; the values are not set above so this
2308 * passes in white.
2309 *
2310 * NOTE: this preserves the full precision of the application
2311 * supplied background color when it is used.
2312 */
2313 else
2314 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2315 back_alpha, output_encoding);
2316 }
2317
2318 /* We need libpng to preserve the original encoding. */
2319 data_encoding = P_FILE;
2320
2321 /* The rows from libpng, while technically gray values, are now also
2322 * color-map indices; however, they may need to be expanded to 1
2323 * byte per pixel. This is what png_set_packing does (i.e., it
2324 * unpacks the bit values into bytes.)
2325 */
2326 if (png_ptr->bit_depth < 8)
2327 png_set_packing(png_ptr);
2328 }
2329
2330 else /* bit depth is 16 */
2331 {
2332 /* The 16-bit input values can be converted directly to 8-bit gamma
2333 * encoded values; however, if a tRNS chunk is present 257 color-map
2334 * entries are required. This means that the extra entry requires
2335 * special processing; add an alpha channel, sacrifice gray level
2336 * 254 and convert transparent (alpha==0) entries to that.
2337 *
2338 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2339 * same time to minimize quality loss. If a tRNS chunk is present
2340 * this means libpng must handle it too; otherwise it is impossible
2341 * to do the exact match on the 16-bit value.
2342 *
2343 * If the output has no alpha channel *and* the background color is
2344 * gray then it is possible to let libpng handle the substitution by
2345 * ensuring that the corresponding gray level matches the background
2346 * color exactly.
2347 */
2348 data_encoding = P_sRGB;
2349
2350 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2351 png_error(png_ptr, "gray[16] color-map: too few entries");
2352
2353 cmap_entries = (unsigned int)make_gray_colormap(display);
2354
2355 if (png_ptr->num_trans > 0)
2356 {
2357 unsigned int back_alpha;
2358
2359 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2360 back_alpha = 0;
2361
2362 else
2363 {
2364 if (back_r == back_g && back_g == back_b)
2365 {
2366 /* Background is gray; no special processing will be
2367 * required.
2368 */
2369 png_color_16 c;
2370 png_uint_32 gray = back_g;
2371
2372 if (output_encoding == P_LINEAR)
2373 {
2374 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2375
2376 /* And make sure the corresponding palette entry
2377 * matches.
2378 */
2379 png_create_colormap_entry(display, gray, back_g, back_g,
2380 back_g, 65535, P_LINEAR);
2381 }
2382
2383 /* The background passed to libpng, however, must be the
2384 * sRGB value.
2385 */
2386 c.index = 0; /*unused*/
2387 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2388
2389 /* NOTE: does this work without expanding tRNS to alpha?
2390 * It should be the color->gray case below apparently
2391 * doesn't.
2392 */
2393 png_set_background_fixed(png_ptr, &c,
2394 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2395 0/*gamma: not used*/);
2396
2397 output_processing = PNG_CMAP_NONE;
2398 break;
2399 }
2400 #ifdef __COVERITY__
2401 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2402 * here.
2403 */
2404 back_alpha = 255;
2405 #else
2406 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2407 #endif
2408 }
2409
2410 /* output_processing means that the libpng-processed row will be
2411 * 8-bit GA and it has to be processing to single byte color-map
2412 * values. Entry 254 is replaced by either a completely
2413 * transparent entry or by the background color at full
2414 * precision (and the background color is not a simple gray
2415 * level in this case.)
2416 */
2417 expand_tRNS = 1;
2418 output_processing = PNG_CMAP_TRANS;
2419 background_index = 254;
2420
2421 /* And set (overwrite) color-map entry 254 to the actual
2422 * background color at full precision.
2423 */
2424 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2425 back_alpha, output_encoding);
2426 }
2427
2428 else
2429 output_processing = PNG_CMAP_NONE;
2430 }
2431 break;
2432
2433 case PNG_COLOR_TYPE_GRAY_ALPHA:
2434 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2435 * of 65536 combinations. If, however, the alpha channel is to be
2436 * removed there are only 256 possibilities if the background is gray.
2437 * (Otherwise there is a subset of the 65536 possibilities defined by
2438 * the triangle between black, white and the background color.)
2439 *
2440 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2441 * worry about tRNS matching - tRNS is ignored if there is an alpha
2442 * channel.
2443 */
2444 data_encoding = P_sRGB;
2445
2446 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2447 {
2448 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2449 png_error(png_ptr, "gray+alpha color-map: too few entries");
2450
2451 cmap_entries = (unsigned int)make_ga_colormap(display);
2452
2453 background_index = PNG_CMAP_GA_BACKGROUND;
2454 output_processing = PNG_CMAP_GA;
2455 }
2456
2457 else /* alpha is removed */
2458 {
2459 /* Alpha must be removed as the PNG data is processed when the
2460 * background is a color because the G and A channels are
2461 * independent and the vector addition (non-parallel vectors) is a
2462 * 2-D problem.
2463 *
2464 * This can be reduced to the same algorithm as above by making a
2465 * colormap containing gray levels (for the opaque grays), a
2466 * background entry (for a transparent pixel) and a set of four six
2467 * level color values, one set for each intermediate alpha value.
2468 * See the comments in make_ga_colormap for how this works in the
2469 * per-pixel processing.
2470 *
2471 * If the background is gray, however, we only need a 256 entry gray
2472 * level color map. It is sufficient to make the entry generated
2473 * for the background color be exactly the color specified.
2474 */
2475 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2476 (back_r == back_g && back_g == back_b))
2477 {
2478 /* Background is gray; no special processing will be required. */
2479 png_color_16 c;
2480 png_uint_32 gray = back_g;
2481
2482 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2483 png_error(png_ptr, "gray-alpha color-map: too few entries");
2484
2485 cmap_entries = (unsigned int)make_gray_colormap(display);
2486
2487 if (output_encoding == P_LINEAR)
2488 {
2489 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2490
2491 /* And make sure the corresponding palette entry matches. */
2492 png_create_colormap_entry(display, gray, back_g, back_g,
2493 back_g, 65535, P_LINEAR);
2494 }
2495
2496 /* The background passed to libpng, however, must be the sRGB
2497 * value.
2498 */
2499 c.index = 0; /*unused*/
2500 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2501
2502 png_set_background_fixed(png_ptr, &c,
2503 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2504 0/*gamma: not used*/);
2505
2506 output_processing = PNG_CMAP_NONE;
2507 }
2508
2509 else
2510 {
2511 png_uint_32 i, a;
2512
2513 /* This is the same as png_make_ga_colormap, above, except that
2514 * the entries are all opaque.
2515 */
2516 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2517 png_error(png_ptr, "ga-alpha color-map: too few entries");
2518
2519 i = 0;
2520 while (i < 231)
2521 {
2522 png_uint_32 gray = (i * 256 + 115) / 231;
2523 png_create_colormap_entry(display, i++, gray, gray, gray,
2524 255, P_sRGB);
2525 }
2526
2527 /* NOTE: this preserves the full precision of the application
2528 * background color.
2529 */
2530 background_index = i;
2531 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2532 #ifdef __COVERITY__
2533 /* Coverity claims that output_encoding
2534 * cannot be 2 (P_LINEAR) here.
2535 */ 255U,
2536 #else
2537 output_encoding == P_LINEAR ? 65535U : 255U,
2538 #endif
2539 output_encoding);
2540
2541 /* For non-opaque input composite on the sRGB background - this
2542 * requires inverting the encoding for each component. The input
2543 * is still converted to the sRGB encoding because this is a
2544 * reasonable approximate to the logarithmic curve of human
2545 * visual sensitivity, at least over the narrow range which PNG
2546 * represents. Consequently 'G' is always sRGB encoded, while
2547 * 'A' is linear. We need the linear background colors.
2548 */
2549 if (output_encoding == P_sRGB) /* else already linear */
2550 {
2551 /* This may produce a value not exactly matching the
2552 * background, but that's ok because these numbers are only
2553 * used when alpha != 0
2554 */
2555 back_r = png_sRGB_table[back_r];
2556 back_g = png_sRGB_table[back_g];
2557 back_b = png_sRGB_table[back_b];
2558 }
2559
2560 for (a=1; a<5; ++a)
2561 {
2562 unsigned int g;
2563
2564 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2565 * by an 8-bit alpha value (0..255).
2566 */
2567 png_uint_32 alpha = 51 * a;
2568 png_uint_32 back_rx = (255-alpha) * back_r;
2569 png_uint_32 back_gx = (255-alpha) * back_g;
2570 png_uint_32 back_bx = (255-alpha) * back_b;
2571
2572 for (g=0; g<6; ++g)
2573 {
2574 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2575
2576 png_create_colormap_entry(display, i++,
2577 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2578 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2579 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2580 }
2581 }
2582
2583 cmap_entries = i;
2584 output_processing = PNG_CMAP_GA;
2585 }
2586 }
2587 break;
2588
2589 case PNG_COLOR_TYPE_RGB:
2590 case PNG_COLOR_TYPE_RGB_ALPHA:
2591 /* Exclude the case where the output is gray; we can always handle this
2592 * with the cases above.
2593 */
2594 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2595 {
2596 /* The color-map will be grayscale, so we may as well convert the
2597 * input RGB values to a simple grayscale and use the grayscale
2598 * code above.
2599 *
2600 * NOTE: calling this apparently damages the recognition of the
2601 * transparent color in background color handling; call
2602 * png_set_tRNS_to_alpha before png_set_background_fixed.
2603 */
2604 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2605 -1);
2606 data_encoding = P_sRGB;
2607
2608 /* The output will now be one or two 8-bit gray or gray+alpha
2609 * channels. The more complex case arises when the input has alpha.
2610 */
2611 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2612 png_ptr->num_trans > 0) &&
2613 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2614 {
2615 /* Both input and output have an alpha channel, so no background
2616 * processing is required; just map the GA bytes to the right
2617 * color-map entry.
2618 */
2619 expand_tRNS = 1;
2620
2621 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2622 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2623
2624 cmap_entries = (unsigned int)make_ga_colormap(display);
2625 background_index = PNG_CMAP_GA_BACKGROUND;
2626 output_processing = PNG_CMAP_GA;
2627 }
2628
2629 else
2630 {
2631 /* Either the input or the output has no alpha channel, so there
2632 * will be no non-opaque pixels in the color-map; it will just be
2633 * grayscale.
2634 */
2635 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2636 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2637
2638 /* Ideally this code would use libpng to do the gamma correction,
2639 * but if an input alpha channel is to be removed we will hit the
2640 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2641 * correction bug). Fix this by dropping the gamma correction in
2642 * this case and doing it in the palette; this will result in
2643 * duplicate palette entries, but that's better than the
2644 * alternative of double gamma correction.
2645 */
2646 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2647 png_ptr->num_trans > 0) &&
2648 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2649 {
2650 cmap_entries = (unsigned int)make_gray_file_colormap(display);
2651 data_encoding = P_FILE;
2652 }
2653
2654 else
2655 cmap_entries = (unsigned int)make_gray_colormap(display);
2656
2657 /* But if the input has alpha or transparency it must be removed
2658 */
2659 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2660 png_ptr->num_trans > 0)
2661 {
2662 png_color_16 c;
2663 png_uint_32 gray = back_g;
2664
2665 /* We need to ensure that the application background exists in
2666 * the colormap and that completely transparent pixels map to
2667 * it. Achieve this simply by ensuring that the entry
2668 * selected for the background really is the background color.
2669 */
2670 if (data_encoding == P_FILE) /* from the fixup above */
2671 {
2672 /* The app supplied a gray which is in output_encoding, we
2673 * need to convert it to a value of the input (P_FILE)
2674 * encoding then set this palette entry to the required
2675 * output encoding.
2676 */
2677 if (output_encoding == P_sRGB)
2678 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2679
2680 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2681 png_ptr->colorspace.gamma)); /* now P_FILE */
2682
2683 /* And make sure the corresponding palette entry contains
2684 * exactly the required sRGB value.
2685 */
2686 png_create_colormap_entry(display, gray, back_g, back_g,
2687 back_g, 0/*unused*/, output_encoding);
2688 }
2689
2690 else if (output_encoding == P_LINEAR)
2691 {
2692 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2693
2694 /* And make sure the corresponding palette entry matches.
2695 */
2696 png_create_colormap_entry(display, gray, back_g, back_g,
2697 back_g, 0/*unused*/, P_LINEAR);
2698 }
2699
2700 /* The background passed to libpng, however, must be the
2701 * output (normally sRGB) value.
2702 */
2703 c.index = 0; /*unused*/
2704 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2705
2706 /* NOTE: the following is apparently a bug in libpng. Without
2707 * it the transparent color recognition in
2708 * png_set_background_fixed seems to go wrong.
2709 */
2710 expand_tRNS = 1;
2711 png_set_background_fixed(png_ptr, &c,
2712 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2713 0/*gamma: not used*/);
2714 }
2715
2716 output_processing = PNG_CMAP_NONE;
2717 }
2718 }
2719
2720 else /* output is color */
2721 {
2722 /* We could use png_quantize here so long as there is no transparent
2723 * color or alpha; png_quantize ignores alpha. Easier overall just
2724 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2725 * Consequently we always want libpng to produce sRGB data.
2726 */
2727 data_encoding = P_sRGB;
2728
2729 /* Is there any transparency or alpha? */
2730 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2731 png_ptr->num_trans > 0)
2732 {
2733 /* Is there alpha in the output too? If so all four channels are
2734 * processed into a special RGB cube with alpha support.
2735 */
2736 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2737 {
2738 png_uint_32 r;
2739
2740 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2741 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2742
2743 cmap_entries = (unsigned int)make_rgb_colormap(display);
2744
2745 /* Add a transparent entry. */
2746 png_create_colormap_entry(display, cmap_entries, 255, 255,
2747 255, 0, P_sRGB);
2748
2749 /* This is stored as the background index for the processing
2750 * algorithm.
2751 */
2752 background_index = cmap_entries++;
2753
2754 /* Add 27 r,g,b entries each with alpha 0.5. */
2755 for (r=0; r<256; r = (r << 1) | 0x7f)
2756 {
2757 png_uint_32 g;
2758
2759 for (g=0; g<256; g = (g << 1) | 0x7f)
2760 {
2761 png_uint_32 b;
2762
2763 /* This generates components with the values 0, 127 and
2764 * 255
2765 */
2766 for (b=0; b<256; b = (b << 1) | 0x7f)
2767 png_create_colormap_entry(display, cmap_entries++,
2768 r, g, b, 128, P_sRGB);
2769 }
2770 }
2771
2772 expand_tRNS = 1;
2773 output_processing = PNG_CMAP_RGB_ALPHA;
2774 }
2775
2776 else
2777 {
2778 /* Alpha/transparency must be removed. The background must
2779 * exist in the color map (achieved by setting adding it after
2780 * the 666 color-map). If the standard processing code will
2781 * pick up this entry automatically that's all that is
2782 * required; libpng can be called to do the background
2783 * processing.
2784 */
2785 unsigned int sample_size =
2786 PNG_IMAGE_SAMPLE_SIZE(output_format);
2787 png_uint_32 r, g, b; /* sRGB background */
2788
2789 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2790 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2791
2792 cmap_entries = (unsigned int)make_rgb_colormap(display);
2793
2794 png_create_colormap_entry(display, cmap_entries, back_r,
2795 back_g, back_b, 0/*unused*/, output_encoding);
2796
2797 if (output_encoding == P_LINEAR)
2798 {
2799 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2800 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2801 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2802 }
2803
2804 else
2805 {
2806 r = back_r;
2807 g = back_g;
2808 b = back_g;
2809 }
2810
2811 /* Compare the newly-created color-map entry with the one the
2812 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2813 * match, add the new one and set this as the background
2814 * index.
2815 */
2816 if (memcmp((png_const_bytep)display->colormap +
2817 sample_size * cmap_entries,
2818 (png_const_bytep)display->colormap +
2819 sample_size * PNG_RGB_INDEX(r,g,b),
2820 sample_size) != 0)
2821 {
2822 /* The background color must be added. */
2823 background_index = cmap_entries++;
2824
2825 /* Add 27 r,g,b entries each with created by composing with
2826 * the background at alpha 0.5.
2827 */
2828 for (r=0; r<256; r = (r << 1) | 0x7f)
2829 {
2830 for (g=0; g<256; g = (g << 1) | 0x7f)
2831 {
2832 /* This generates components with the values 0, 127
2833 * and 255
2834 */
2835 for (b=0; b<256; b = (b << 1) | 0x7f)
2836 png_create_colormap_entry(display, cmap_entries++,
2837 png_colormap_compose(display, r, P_sRGB, 128,
2838 back_r, output_encoding),
2839 png_colormap_compose(display, g, P_sRGB, 128,
2840 back_g, output_encoding),
2841 png_colormap_compose(display, b, P_sRGB, 128,
2842 back_b, output_encoding),
2843 0/*unused*/, output_encoding);
2844 }
2845 }
2846
2847 expand_tRNS = 1;
2848 output_processing = PNG_CMAP_RGB_ALPHA;
2849 }
2850
2851 else /* background color is in the standard color-map */
2852 {
2853 png_color_16 c;
2854
2855 c.index = 0; /*unused*/
2856 c.red = (png_uint_16)back_r;
2857 c.gray = c.green = (png_uint_16)back_g;
2858 c.blue = (png_uint_16)back_b;
2859
2860 png_set_background_fixed(png_ptr, &c,
2861 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2862 0/*gamma: not used*/);
2863
2864 output_processing = PNG_CMAP_RGB;
2865 }
2866 }
2867 }
2868
2869 else /* no alpha or transparency in the input */
2870 {
2871 /* Alpha in the output is irrelevant, simply map the opaque input
2872 * pixels to the 6x6x6 color-map.
2873 */
2874 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2875 png_error(png_ptr, "rgb color-map: too few entries");
2876
2877 cmap_entries = (unsigned int)make_rgb_colormap(display);
2878 output_processing = PNG_CMAP_RGB;
2879 }
2880 }
2881 break;
2882
2883 case PNG_COLOR_TYPE_PALETTE:
2884 /* It's already got a color-map. It may be necessary to eliminate the
2885 * tRNS entries though.
2886 */
2887 {
2888 unsigned int num_trans = png_ptr->num_trans;
2889 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2890 png_const_colorp colormap = png_ptr->palette;
2891 int do_background = trans != NULL &&
2892 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2893 unsigned int i;
2894
2895 /* Just in case: */
2896 if (trans == NULL)
2897 num_trans = 0;
2898
2899 output_processing = PNG_CMAP_NONE;
2900 data_encoding = P_FILE; /* Don't change from color-map indices */
2901 cmap_entries = (unsigned int)png_ptr->num_palette;
2902 if (cmap_entries > 256)
2903 cmap_entries = 256;
2904
2905 if (cmap_entries > (unsigned int)image->colormap_entries)
2906 png_error(png_ptr, "palette color-map: too few entries");
2907
2908 for (i=0; i < cmap_entries; ++i)
2909 {
2910 if (do_background != 0 && i < num_trans && trans[i] < 255)
2911 {
2912 if (trans[i] == 0)
2913 png_create_colormap_entry(display, i, back_r, back_g,
2914 back_b, 0, output_encoding);
2915
2916 else
2917 {
2918 /* Must compose the PNG file color in the color-map entry
2919 * on the sRGB color in 'back'.
2920 */
2921 png_create_colormap_entry(display, i,
2922 png_colormap_compose(display, colormap[i].red,
2923 P_FILE, trans[i], back_r, output_encoding),
2924 png_colormap_compose(display, colormap[i].green,
2925 P_FILE, trans[i], back_g, output_encoding),
2926 png_colormap_compose(display, colormap[i].blue,
2927 P_FILE, trans[i], back_b, output_encoding),
2928 output_encoding == P_LINEAR ? trans[i] * 257U :
2929 trans[i],
2930 output_encoding);
2931 }
2932 }
2933
2934 else
2935 png_create_colormap_entry(display, i, colormap[i].red,
2936 colormap[i].green, colormap[i].blue,
2937 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2938 }
2939
2940 /* The PNG data may have indices packed in fewer than 8 bits, it
2941 * must be expanded if so.
2942 */
2943 if (png_ptr->bit_depth < 8)
2944 png_set_packing(png_ptr);
2945 }
2946 break;
2947
2948 default:
2949 png_error(png_ptr, "invalid PNG color type");
2950 /*NOT REACHED*/
2951 }
2952
2953 /* Now deal with the output processing */
2954 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2955 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2956 png_set_tRNS_to_alpha(png_ptr);
2957
2958 switch (data_encoding)
2959 {
2960 case P_sRGB:
2961 /* Change to 8-bit sRGB */
2962 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2963 /* FALLTHROUGH */
2964
2965 case P_FILE:
2966 if (png_ptr->bit_depth > 8)
2967 png_set_scale_16(png_ptr);
2968 break;
2969
2970 #ifdef __GNUC__
2971 default:
2972 png_error(png_ptr, "bad data option (internal error)");
2973 #endif
2974 }
2975
2976 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2977 png_error(png_ptr, "color map overflow (BAD internal error)");
2978
2979 image->colormap_entries = cmap_entries;
2980
2981 /* Double check using the recorded background index */
2982 switch (output_processing)
2983 {
2984 case PNG_CMAP_NONE:
2985 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2986 goto bad_background;
2987 break;
2988
2989 case PNG_CMAP_GA:
2990 if (background_index != PNG_CMAP_GA_BACKGROUND)
2991 goto bad_background;
2992 break;
2993
2994 case PNG_CMAP_TRANS:
2995 if (background_index >= cmap_entries ||
2996 background_index != PNG_CMAP_TRANS_BACKGROUND)
2997 goto bad_background;
2998 break;
2999
3000 case PNG_CMAP_RGB:
3001 if (background_index != PNG_CMAP_RGB_BACKGROUND)
3002 goto bad_background;
3003 break;
3004
3005 case PNG_CMAP_RGB_ALPHA:
3006 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
3007 goto bad_background;
3008 break;
3009
3010 default:
3011 png_error(png_ptr, "bad processing option (internal error)");
3012
3013 bad_background:
3014 png_error(png_ptr, "bad background index (internal error)");
3015 }
3016
3017 display->colormap_processing = (int)output_processing;
3018
3019 return 1/*ok*/;
3020 }
3021
3022 /* The final part of the color-map read called from png_image_finish_read. */
3023 static int
png_image_read_and_map(png_voidp argument)3024 png_image_read_and_map(png_voidp argument)
3025 {
3026 png_image_read_control *display = png_voidcast(png_image_read_control*,
3027 argument);
3028 png_imagep image = display->image;
3029 png_structrp png_ptr = image->opaque->png_ptr;
3030 int passes;
3031
3032 /* Called when the libpng data must be transformed into the color-mapped
3033 * form. There is a local row buffer in display->local and this routine must
3034 * do the interlace handling.
3035 */
3036 switch (png_ptr->interlaced)
3037 {
3038 case PNG_INTERLACE_NONE:
3039 passes = 1;
3040 break;
3041
3042 case PNG_INTERLACE_ADAM7:
3043 passes = PNG_INTERLACE_ADAM7_PASSES;
3044 break;
3045
3046 default:
3047 png_error(png_ptr, "unknown interlace type");
3048 }
3049
3050 {
3051 png_uint_32 height = image->height;
3052 png_uint_32 width = image->width;
3053 int proc = display->colormap_processing;
3054 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3055 ptrdiff_t step_row = display->row_bytes;
3056 int pass;
3057
3058 for (pass = 0; pass < passes; ++pass)
3059 {
3060 unsigned int startx, stepx, stepy;
3061 png_uint_32 y;
3062
3063 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3064 {
3065 /* The row may be empty for a short image: */
3066 if (PNG_PASS_COLS(width, pass) == 0)
3067 continue;
3068
3069 startx = PNG_PASS_START_COL(pass);
3070 stepx = PNG_PASS_COL_OFFSET(pass);
3071 y = PNG_PASS_START_ROW(pass);
3072 stepy = PNG_PASS_ROW_OFFSET(pass);
3073 }
3074
3075 else
3076 {
3077 y = 0;
3078 startx = 0;
3079 stepx = stepy = 1;
3080 }
3081
3082 for (; y<height; y += stepy)
3083 {
3084 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3085 png_bytep outrow = first_row + y * step_row;
3086 png_const_bytep end_row = outrow + width;
3087
3088 /* Read read the libpng data into the temporary buffer. */
3089 png_read_row(png_ptr, inrow, NULL);
3090
3091 /* Now process the row according to the processing option, note
3092 * that the caller verifies that the format of the libpng output
3093 * data is as required.
3094 */
3095 outrow += startx;
3096 switch (proc)
3097 {
3098 case PNG_CMAP_GA:
3099 for (; outrow < end_row; outrow += stepx)
3100 {
3101 /* The data is always in the PNG order */
3102 unsigned int gray = *inrow++;
3103 unsigned int alpha = *inrow++;
3104 unsigned int entry;
3105
3106 /* NOTE: this code is copied as a comment in
3107 * make_ga_colormap above. Please update the
3108 * comment if you change this code!
3109 */
3110 if (alpha > 229) /* opaque */
3111 {
3112 entry = (231 * gray + 128) >> 8;
3113 }
3114 else if (alpha < 26) /* transparent */
3115 {
3116 entry = 231;
3117 }
3118 else /* partially opaque */
3119 {
3120 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3121 }
3122
3123 *outrow = (png_byte)entry;
3124 }
3125 break;
3126
3127 case PNG_CMAP_TRANS:
3128 for (; outrow < end_row; outrow += stepx)
3129 {
3130 png_byte gray = *inrow++;
3131 png_byte alpha = *inrow++;
3132
3133 if (alpha == 0)
3134 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3135
3136 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3137 *outrow = gray;
3138
3139 else
3140 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3141 }
3142 break;
3143
3144 case PNG_CMAP_RGB:
3145 for (; outrow < end_row; outrow += stepx)
3146 {
3147 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3148 inrow += 3;
3149 }
3150 break;
3151
3152 case PNG_CMAP_RGB_ALPHA:
3153 for (; outrow < end_row; outrow += stepx)
3154 {
3155 unsigned int alpha = inrow[3];
3156
3157 /* Because the alpha entries only hold alpha==0.5 values
3158 * split the processing at alpha==0.25 (64) and 0.75
3159 * (196).
3160 */
3161
3162 if (alpha >= 196)
3163 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3164 inrow[2]);
3165
3166 else if (alpha < 64)
3167 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3168
3169 else
3170 {
3171 /* Likewise there are three entries for each of r, g
3172 * and b. We could select the entry by popcount on
3173 * the top two bits on those architectures that
3174 * support it, this is what the code below does,
3175 * crudely.
3176 */
3177 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3178
3179 /* Here are how the values map:
3180 *
3181 * 0x00 .. 0x3f -> 0
3182 * 0x40 .. 0xbf -> 1
3183 * 0xc0 .. 0xff -> 2
3184 *
3185 * So, as above with the explicit alpha checks, the
3186 * breakpoints are at 64 and 196.
3187 */
3188 if (inrow[0] & 0x80) back_i += 9; /* red */
3189 if (inrow[0] & 0x40) back_i += 9;
3190 if (inrow[0] & 0x80) back_i += 3; /* green */
3191 if (inrow[0] & 0x40) back_i += 3;
3192 if (inrow[0] & 0x80) back_i += 1; /* blue */
3193 if (inrow[0] & 0x40) back_i += 1;
3194
3195 *outrow = (png_byte)back_i;
3196 }
3197
3198 inrow += 4;
3199 }
3200 break;
3201
3202 default:
3203 break;
3204 }
3205 }
3206 }
3207 }
3208
3209 return 1;
3210 }
3211
3212 static int
png_image_read_colormapped(png_voidp argument)3213 png_image_read_colormapped(png_voidp argument)
3214 {
3215 png_image_read_control *display = png_voidcast(png_image_read_control*,
3216 argument);
3217 png_imagep image = display->image;
3218 png_controlp control = image->opaque;
3219 png_structrp png_ptr = control->png_ptr;
3220 png_inforp info_ptr = control->info_ptr;
3221
3222 int passes = 0; /* As a flag */
3223
3224 PNG_SKIP_CHUNKS(png_ptr);
3225
3226 /* Update the 'info' structure and make sure the result is as required; first
3227 * make sure to turn on the interlace handling if it will be required
3228 * (because it can't be turned on *after* the call to png_read_update_info!)
3229 */
3230 if (display->colormap_processing == PNG_CMAP_NONE)
3231 passes = png_set_interlace_handling(png_ptr);
3232
3233 png_read_update_info(png_ptr, info_ptr);
3234
3235 /* The expected output can be deduced from the colormap_processing option. */
3236 switch (display->colormap_processing)
3237 {
3238 case PNG_CMAP_NONE:
3239 /* Output must be one channel and one byte per pixel, the output
3240 * encoding can be anything.
3241 */
3242 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3243 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3244 info_ptr->bit_depth == 8)
3245 break;
3246
3247 goto bad_output;
3248
3249 case PNG_CMAP_TRANS:
3250 case PNG_CMAP_GA:
3251 /* Output must be two channels and the 'G' one must be sRGB, the latter
3252 * can be checked with an exact number because it should have been set
3253 * to this number above!
3254 */
3255 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3256 info_ptr->bit_depth == 8 &&
3257 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3258 image->colormap_entries == 256)
3259 break;
3260
3261 goto bad_output;
3262
3263 case PNG_CMAP_RGB:
3264 /* Output must be 8-bit sRGB encoded RGB */
3265 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3266 info_ptr->bit_depth == 8 &&
3267 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3268 image->colormap_entries == 216)
3269 break;
3270
3271 goto bad_output;
3272
3273 case PNG_CMAP_RGB_ALPHA:
3274 /* Output must be 8-bit sRGB encoded RGBA */
3275 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3276 info_ptr->bit_depth == 8 &&
3277 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3278 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3279 break;
3280
3281 goto bad_output;
3282
3283 default:
3284 bad_output:
3285 png_error(png_ptr, "bad color-map processing (internal error)");
3286 }
3287
3288 /* Now read the rows. Do this here if it is possible to read directly into
3289 * the output buffer, otherwise allocate a local row buffer of the maximum
3290 * size libpng requires and call the relevant processing routine safely.
3291 */
3292 {
3293 png_voidp first_row = display->buffer;
3294 ptrdiff_t row_bytes = display->row_stride;
3295
3296 /* The following expression is designed to work correctly whether it gives
3297 * a signed or an unsigned result.
3298 */
3299 if (row_bytes < 0)
3300 {
3301 char *ptr = png_voidcast(char*, first_row);
3302 ptr += (image->height-1) * (-row_bytes);
3303 first_row = png_voidcast(png_voidp, ptr);
3304 }
3305
3306 display->first_row = first_row;
3307 display->row_bytes = row_bytes;
3308 }
3309
3310 if (passes == 0)
3311 {
3312 int result;
3313 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3314
3315 display->local_row = row;
3316 result = png_safe_execute(image, png_image_read_and_map, display);
3317 display->local_row = NULL;
3318 png_free(png_ptr, row);
3319
3320 return result;
3321 }
3322
3323 else
3324 {
3325 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
3326
3327 while (--passes >= 0)
3328 {
3329 png_uint_32 y = image->height;
3330 png_bytep row = png_voidcast(png_bytep, display->first_row);
3331
3332 for (; y > 0; --y)
3333 {
3334 png_read_row(png_ptr, row, NULL);
3335 row += row_bytes;
3336 }
3337 }
3338
3339 return 1;
3340 }
3341 }
3342
3343 /* Just the row reading part of png_image_read. */
3344 static int
png_image_read_composite(png_voidp argument)3345 png_image_read_composite(png_voidp argument)
3346 {
3347 png_image_read_control *display = png_voidcast(png_image_read_control*,
3348 argument);
3349 png_imagep image = display->image;
3350 png_structrp png_ptr = image->opaque->png_ptr;
3351 int passes;
3352
3353 switch (png_ptr->interlaced)
3354 {
3355 case PNG_INTERLACE_NONE:
3356 passes = 1;
3357 break;
3358
3359 case PNG_INTERLACE_ADAM7:
3360 passes = PNG_INTERLACE_ADAM7_PASSES;
3361 break;
3362
3363 default:
3364 png_error(png_ptr, "unknown interlace type");
3365 }
3366
3367 {
3368 png_uint_32 height = image->height;
3369 png_uint_32 width = image->width;
3370 ptrdiff_t step_row = display->row_bytes;
3371 unsigned int channels =
3372 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3373 int pass;
3374
3375 for (pass = 0; pass < passes; ++pass)
3376 {
3377 unsigned int startx, stepx, stepy;
3378 png_uint_32 y;
3379
3380 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3381 {
3382 /* The row may be empty for a short image: */
3383 if (PNG_PASS_COLS(width, pass) == 0)
3384 continue;
3385
3386 startx = PNG_PASS_START_COL(pass) * channels;
3387 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3388 y = PNG_PASS_START_ROW(pass);
3389 stepy = PNG_PASS_ROW_OFFSET(pass);
3390 }
3391
3392 else
3393 {
3394 y = 0;
3395 startx = 0;
3396 stepx = channels;
3397 stepy = 1;
3398 }
3399
3400 for (; y<height; y += stepy)
3401 {
3402 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3403 png_bytep outrow;
3404 png_const_bytep end_row;
3405
3406 /* Read the row, which is packed: */
3407 png_read_row(png_ptr, inrow, NULL);
3408
3409 outrow = png_voidcast(png_bytep, display->first_row);
3410 outrow += y * step_row;
3411 end_row = outrow + width * channels;
3412
3413 /* Now do the composition on each pixel in this row. */
3414 outrow += startx;
3415 for (; outrow < end_row; outrow += stepx)
3416 {
3417 png_byte alpha = inrow[channels];
3418
3419 if (alpha > 0) /* else no change to the output */
3420 {
3421 unsigned int c;
3422
3423 for (c=0; c<channels; ++c)
3424 {
3425 png_uint_32 component = inrow[c];
3426
3427 if (alpha < 255) /* else just use component */
3428 {
3429 /* This is PNG_OPTIMIZED_ALPHA, the component value
3430 * is a linear 8-bit value. Combine this with the
3431 * current outrow[c] value which is sRGB encoded.
3432 * Arithmetic here is 16-bits to preserve the output
3433 * values correctly.
3434 */
3435 component *= 257*255; /* =65535 */
3436 component += (255-alpha)*png_sRGB_table[outrow[c]];
3437
3438 /* So 'component' is scaled by 255*65535 and is
3439 * therefore appropriate for the sRGB to linear
3440 * conversion table.
3441 */
3442 component = PNG_sRGB_FROM_LINEAR(component);
3443 }
3444
3445 outrow[c] = (png_byte)component;
3446 }
3447 }
3448
3449 inrow += channels+1; /* components and alpha channel */
3450 }
3451 }
3452 }
3453 }
3454
3455 return 1;
3456 }
3457
3458 /* The do_local_background case; called when all the following transforms are to
3459 * be done:
3460 *
3461 * PNG_RGB_TO_GRAY
3462 * PNG_COMPOSITE
3463 * PNG_GAMMA
3464 *
3465 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3466 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3467 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3468 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3469 * row and handles the removal or pre-multiplication of the alpha channel.
3470 */
3471 static int
png_image_read_background(png_voidp argument)3472 png_image_read_background(png_voidp argument)
3473 {
3474 png_image_read_control *display = png_voidcast(png_image_read_control*,
3475 argument);
3476 png_imagep image = display->image;
3477 png_structrp png_ptr = image->opaque->png_ptr;
3478 png_inforp info_ptr = image->opaque->info_ptr;
3479 png_uint_32 height = image->height;
3480 png_uint_32 width = image->width;
3481 int pass, passes;
3482
3483 /* Double check the convoluted logic below. We expect to get here with
3484 * libpng doing rgb to gray and gamma correction but background processing
3485 * left to the png_image_read_background function. The rows libpng produce
3486 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3487 */
3488 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3489 png_error(png_ptr, "lost rgb to gray");
3490
3491 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3492 png_error(png_ptr, "unexpected compose");
3493
3494 if (png_get_channels(png_ptr, info_ptr) != 2)
3495 png_error(png_ptr, "lost/gained channels");
3496
3497 /* Expect the 8-bit case to always remove the alpha channel */
3498 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3499 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3500 png_error(png_ptr, "unexpected 8-bit transformation");
3501
3502 switch (png_ptr->interlaced)
3503 {
3504 case PNG_INTERLACE_NONE:
3505 passes = 1;
3506 break;
3507
3508 case PNG_INTERLACE_ADAM7:
3509 passes = PNG_INTERLACE_ADAM7_PASSES;
3510 break;
3511
3512 default:
3513 png_error(png_ptr, "unknown interlace type");
3514 }
3515
3516 /* Use direct access to info_ptr here because otherwise the simplified API
3517 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3518 * checking the value after libpng expansions, not the original value in the
3519 * PNG.
3520 */
3521 switch (info_ptr->bit_depth)
3522 {
3523 case 8:
3524 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3525 * to be removed by composing on a background: either the row if
3526 * display->background is NULL or display->background->green if not.
3527 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3528 */
3529 {
3530 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3531 ptrdiff_t step_row = display->row_bytes;
3532
3533 for (pass = 0; pass < passes; ++pass)
3534 {
3535 png_bytep row = png_voidcast(png_bytep, display->first_row);
3536 unsigned int startx, stepx, stepy;
3537 png_uint_32 y;
3538
3539 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3540 {
3541 /* The row may be empty for a short image: */
3542 if (PNG_PASS_COLS(width, pass) == 0)
3543 continue;
3544
3545 startx = PNG_PASS_START_COL(pass);
3546 stepx = PNG_PASS_COL_OFFSET(pass);
3547 y = PNG_PASS_START_ROW(pass);
3548 stepy = PNG_PASS_ROW_OFFSET(pass);
3549 }
3550
3551 else
3552 {
3553 y = 0;
3554 startx = 0;
3555 stepx = stepy = 1;
3556 }
3557
3558 if (display->background == NULL)
3559 {
3560 for (; y<height; y += stepy)
3561 {
3562 png_bytep inrow = png_voidcast(png_bytep,
3563 display->local_row);
3564 png_bytep outrow = first_row + y * step_row;
3565 png_const_bytep end_row = outrow + width;
3566
3567 /* Read the row, which is packed: */
3568 png_read_row(png_ptr, inrow, NULL);
3569
3570 /* Now do the composition on each pixel in this row. */
3571 outrow += startx;
3572 for (; outrow < end_row; outrow += stepx)
3573 {
3574 png_byte alpha = inrow[1];
3575
3576 if (alpha > 0) /* else no change to the output */
3577 {
3578 png_uint_32 component = inrow[0];
3579
3580 if (alpha < 255) /* else just use component */
3581 {
3582 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3583 * necessary to invert the sRGB transfer
3584 * function and multiply the alpha out.
3585 */
3586 component = png_sRGB_table[component] * alpha;
3587 component += png_sRGB_table[outrow[0]] *
3588 (255-alpha);
3589 component = PNG_sRGB_FROM_LINEAR(component);
3590 }
3591
3592 outrow[0] = (png_byte)component;
3593 }
3594
3595 inrow += 2; /* gray and alpha channel */
3596 }
3597 }
3598 }
3599
3600 else /* constant background value */
3601 {
3602 png_byte background8 = display->background->green;
3603 png_uint_16 background = png_sRGB_table[background8];
3604
3605 for (; y<height; y += stepy)
3606 {
3607 png_bytep inrow = png_voidcast(png_bytep,
3608 display->local_row);
3609 png_bytep outrow = first_row + y * step_row;
3610 png_const_bytep end_row = outrow + width;
3611
3612 /* Read the row, which is packed: */
3613 png_read_row(png_ptr, inrow, NULL);
3614
3615 /* Now do the composition on each pixel in this row. */
3616 outrow += startx;
3617 for (; outrow < end_row; outrow += stepx)
3618 {
3619 png_byte alpha = inrow[1];
3620
3621 if (alpha > 0) /* else use background */
3622 {
3623 png_uint_32 component = inrow[0];
3624
3625 if (alpha < 255) /* else just use component */
3626 {
3627 component = png_sRGB_table[component] * alpha;
3628 component += background * (255-alpha);
3629 component = PNG_sRGB_FROM_LINEAR(component);
3630 }
3631
3632 outrow[0] = (png_byte)component;
3633 }
3634
3635 else
3636 outrow[0] = background8;
3637
3638 inrow += 2; /* gray and alpha channel */
3639 }
3640
3641 row += display->row_bytes;
3642 }
3643 }
3644 }
3645 }
3646 break;
3647
3648 case 16:
3649 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3650 * still be done and, maybe, the alpha channel removed. This code also
3651 * handles the alpha-first option.
3652 */
3653 {
3654 png_uint_16p first_row = png_voidcast(png_uint_16p,
3655 display->first_row);
3656 /* The division by two is safe because the caller passed in a
3657 * stride which was multiplied by 2 (below) to get row_bytes.
3658 */
3659 ptrdiff_t step_row = display->row_bytes / 2;
3660 unsigned int preserve_alpha = (image->format &
3661 PNG_FORMAT_FLAG_ALPHA) != 0;
3662 unsigned int outchannels = 1U+preserve_alpha;
3663 int swap_alpha = 0;
3664
3665 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3666 if (preserve_alpha != 0 &&
3667 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3668 swap_alpha = 1;
3669 # endif
3670
3671 for (pass = 0; pass < passes; ++pass)
3672 {
3673 unsigned int startx, stepx, stepy;
3674 png_uint_32 y;
3675
3676 /* The 'x' start and step are adjusted to output components here.
3677 */
3678 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3679 {
3680 /* The row may be empty for a short image: */
3681 if (PNG_PASS_COLS(width, pass) == 0)
3682 continue;
3683
3684 startx = PNG_PASS_START_COL(pass) * outchannels;
3685 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3686 y = PNG_PASS_START_ROW(pass);
3687 stepy = PNG_PASS_ROW_OFFSET(pass);
3688 }
3689
3690 else
3691 {
3692 y = 0;
3693 startx = 0;
3694 stepx = outchannels;
3695 stepy = 1;
3696 }
3697
3698 for (; y<height; y += stepy)
3699 {
3700 png_const_uint_16p inrow;
3701 png_uint_16p outrow = first_row + y*step_row;
3702 png_uint_16p end_row = outrow + width * outchannels;
3703
3704 /* Read the row, which is packed: */
3705 png_read_row(png_ptr, png_voidcast(png_bytep,
3706 display->local_row), NULL);
3707 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3708
3709 /* Now do the pre-multiplication on each pixel in this row.
3710 */
3711 outrow += startx;
3712 for (; outrow < end_row; outrow += stepx)
3713 {
3714 png_uint_32 component = inrow[0];
3715 png_uint_16 alpha = inrow[1];
3716
3717 if (alpha > 0) /* else 0 */
3718 {
3719 if (alpha < 65535) /* else just use component */
3720 {
3721 component *= alpha;
3722 component += 32767;
3723 component /= 65535;
3724 }
3725 }
3726
3727 else
3728 component = 0;
3729
3730 outrow[swap_alpha] = (png_uint_16)component;
3731 if (preserve_alpha != 0)
3732 outrow[1 ^ swap_alpha] = alpha;
3733
3734 inrow += 2; /* components and alpha channel */
3735 }
3736 }
3737 }
3738 }
3739 break;
3740
3741 #ifdef __GNUC__
3742 default:
3743 png_error(png_ptr, "unexpected bit depth");
3744 #endif
3745 }
3746
3747 return 1;
3748 }
3749
3750 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3751 static int
png_image_read_direct(png_voidp argument)3752 png_image_read_direct(png_voidp argument)
3753 {
3754 png_image_read_control *display = png_voidcast(png_image_read_control*,
3755 argument);
3756 png_imagep image = display->image;
3757 png_structrp png_ptr = image->opaque->png_ptr;
3758 png_inforp info_ptr = image->opaque->info_ptr;
3759
3760 png_uint_32 format = image->format;
3761 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3762 int do_local_compose = 0;
3763 int do_local_background = 0; /* to avoid double gamma correction bug */
3764 int passes = 0;
3765
3766 /* Add transforms to ensure the correct output format is produced then check
3767 * that the required implementation support is there. Always expand; always
3768 * need 8 bits minimum, no palette and expanded tRNS.
3769 */
3770 png_set_expand(png_ptr);
3771
3772 /* Now check the format to see if it was modified. */
3773 {
3774 png_uint_32 base_format = png_image_format(png_ptr) &
3775 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3776 png_uint_32 change = format ^ base_format;
3777 png_fixed_point output_gamma;
3778 int mode; /* alpha mode */
3779
3780 /* Do this first so that we have a record if rgb to gray is happening. */
3781 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3782 {
3783 /* gray<->color transformation required. */
3784 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3785 png_set_gray_to_rgb(png_ptr);
3786
3787 else
3788 {
3789 /* libpng can't do both rgb to gray and
3790 * background/pre-multiplication if there is also significant gamma
3791 * correction, because both operations require linear colors and
3792 * the code only supports one transform doing the gamma correction.
3793 * Handle this by doing the pre-multiplication or background
3794 * operation in this code, if necessary.
3795 *
3796 * TODO: fix this by rewriting pngrtran.c (!)
3797 *
3798 * For the moment (given that fixing this in pngrtran.c is an
3799 * enormous change) 'do_local_background' is used to indicate that
3800 * the problem exists.
3801 */
3802 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3803 do_local_background = 1/*maybe*/;
3804
3805 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3806 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3807 }
3808
3809 change &= ~PNG_FORMAT_FLAG_COLOR;
3810 }
3811
3812 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3813 */
3814 {
3815 png_fixed_point input_gamma_default;
3816
3817 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3818 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3819 input_gamma_default = PNG_GAMMA_LINEAR;
3820 else
3821 input_gamma_default = PNG_DEFAULT_sRGB;
3822
3823 /* Call png_set_alpha_mode to set the default for the input gamma; the
3824 * output gamma is set by a second call below.
3825 */
3826 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3827 }
3828
3829 if (linear != 0)
3830 {
3831 /* If there *is* an alpha channel in the input it must be multiplied
3832 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3833 */
3834 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3835 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3836
3837 else
3838 mode = PNG_ALPHA_PNG;
3839
3840 output_gamma = PNG_GAMMA_LINEAR;
3841 }
3842
3843 else
3844 {
3845 mode = PNG_ALPHA_PNG;
3846 output_gamma = PNG_DEFAULT_sRGB;
3847 }
3848
3849 if ((change & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0)
3850 {
3851 mode = PNG_ALPHA_OPTIMIZED;
3852 change &= ~PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
3853 }
3854
3855 /* If 'do_local_background' is set check for the presence of gamma
3856 * correction; this is part of the work-round for the libpng bug
3857 * described above.
3858 *
3859 * TODO: fix libpng and remove this.
3860 */
3861 if (do_local_background != 0)
3862 {
3863 png_fixed_point gtest;
3864
3865 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3866 * gamma correction, the screen gamma hasn't been set on png_struct
3867 * yet; it's set below. png_struct::gamma, however, is set to the
3868 * final value.
3869 */
3870 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3871 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3872 do_local_background = 0;
3873
3874 else if (mode == PNG_ALPHA_STANDARD)
3875 {
3876 do_local_background = 2/*required*/;
3877 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3878 }
3879
3880 /* else leave as 1 for the checks below */
3881 }
3882
3883 /* If the bit-depth changes then handle that here. */
3884 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3885 {
3886 if (linear != 0 /*16-bit output*/)
3887 png_set_expand_16(png_ptr);
3888
3889 else /* 8-bit output */
3890 png_set_scale_16(png_ptr);
3891
3892 change &= ~PNG_FORMAT_FLAG_LINEAR;
3893 }
3894
3895 /* Now the background/alpha channel changes. */
3896 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3897 {
3898 /* Removing an alpha channel requires composition for the 8-bit
3899 * formats; for the 16-bit it is already done, above, by the
3900 * pre-multiplication and the channel just needs to be stripped.
3901 */
3902 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3903 {
3904 /* If RGB->gray is happening the alpha channel must be left and the
3905 * operation completed locally.
3906 *
3907 * TODO: fix libpng and remove this.
3908 */
3909 if (do_local_background != 0)
3910 do_local_background = 2/*required*/;
3911
3912 /* 16-bit output: just remove the channel */
3913 else if (linear != 0) /* compose on black (well, pre-multiply) */
3914 png_set_strip_alpha(png_ptr);
3915
3916 /* 8-bit output: do an appropriate compose */
3917 else if (display->background != NULL)
3918 {
3919 png_color_16 c;
3920
3921 c.index = 0; /*unused*/
3922 c.red = display->background->red;
3923 c.green = display->background->green;
3924 c.blue = display->background->blue;
3925 c.gray = display->background->green;
3926
3927 /* This is always an 8-bit sRGB value, using the 'green' channel
3928 * for gray is much better than calculating the luminance here;
3929 * we can get off-by-one errors in that calculation relative to
3930 * the app expectations and that will show up in transparent
3931 * pixels.
3932 */
3933 png_set_background_fixed(png_ptr, &c,
3934 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3935 0/*gamma: not used*/);
3936 }
3937
3938 else /* compose on row: implemented below. */
3939 {
3940 do_local_compose = 1;
3941 /* This leaves the alpha channel in the output, so it has to be
3942 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3943 * one so the code only has to hack on the pixels that require
3944 * composition.
3945 */
3946 mode = PNG_ALPHA_OPTIMIZED;
3947 }
3948 }
3949
3950 else /* output needs an alpha channel */
3951 {
3952 /* This is tricky because it happens before the swap operation has
3953 * been accomplished; however, the swap does *not* swap the added
3954 * alpha channel (weird API), so it must be added in the correct
3955 * place.
3956 */
3957 png_uint_32 filler; /* opaque filler */
3958 int where;
3959
3960 if (linear != 0)
3961 filler = 65535;
3962
3963 else
3964 filler = 255;
3965
3966 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3967 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3968 {
3969 where = PNG_FILLER_BEFORE;
3970 change &= ~PNG_FORMAT_FLAG_AFIRST;
3971 }
3972
3973 else
3974 #endif
3975 where = PNG_FILLER_AFTER;
3976
3977 png_set_add_alpha(png_ptr, filler, where);
3978 }
3979
3980 /* This stops the (irrelevant) call to swap_alpha below. */
3981 change &= ~PNG_FORMAT_FLAG_ALPHA;
3982 }
3983
3984 /* Now set the alpha mode correctly; this is always done, even if there is
3985 * no alpha channel in either the input or the output because it correctly
3986 * sets the output gamma.
3987 */
3988 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3989
3990 # ifdef PNG_FORMAT_BGR_SUPPORTED
3991 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3992 {
3993 /* Check only the output format; PNG is never BGR; don't do this if
3994 * the output is gray, but fix up the 'format' value in that case.
3995 */
3996 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3997 png_set_bgr(png_ptr);
3998
3999 else
4000 format &= ~PNG_FORMAT_FLAG_BGR;
4001
4002 change &= ~PNG_FORMAT_FLAG_BGR;
4003 }
4004 # endif
4005
4006 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
4007 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
4008 {
4009 /* Only relevant if there is an alpha channel - it's particularly
4010 * important to handle this correctly because do_local_compose may
4011 * be set above and then libpng will keep the alpha channel for this
4012 * code to remove.
4013 */
4014 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
4015 {
4016 /* Disable this if doing a local background,
4017 * TODO: remove this when local background is no longer required.
4018 */
4019 if (do_local_background != 2)
4020 png_set_swap_alpha(png_ptr);
4021 }
4022
4023 else
4024 format &= ~PNG_FORMAT_FLAG_AFIRST;
4025
4026 change &= ~PNG_FORMAT_FLAG_AFIRST;
4027 }
4028 # endif
4029
4030 /* If the *output* is 16-bit then we need to check for a byte-swap on this
4031 * architecture.
4032 */
4033 if (linear != 0)
4034 {
4035 png_uint_16 le = 0x0001;
4036
4037 if ((*(png_const_bytep) & le) != 0)
4038 png_set_swap(png_ptr);
4039 }
4040
4041 /* If change is not now 0 some transformation is missing - error out. */
4042 if (change != 0)
4043 png_error(png_ptr, "png_read_image: unsupported transformation");
4044 }
4045
4046 PNG_SKIP_CHUNKS(png_ptr);
4047
4048 /* Update the 'info' structure and make sure the result is as required; first
4049 * make sure to turn on the interlace handling if it will be required
4050 * (because it can't be turned on *after* the call to png_read_update_info!)
4051 *
4052 * TODO: remove the do_local_background fixup below.
4053 */
4054 if (do_local_compose == 0 && do_local_background != 2)
4055 passes = png_set_interlace_handling(png_ptr);
4056
4057 png_read_update_info(png_ptr, info_ptr);
4058
4059 {
4060 png_uint_32 info_format = 0;
4061
4062 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
4063 info_format |= PNG_FORMAT_FLAG_COLOR;
4064
4065 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
4066 {
4067 /* do_local_compose removes this channel below. */
4068 if (do_local_compose == 0)
4069 {
4070 /* do_local_background does the same if required. */
4071 if (do_local_background != 2 ||
4072 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
4073 info_format |= PNG_FORMAT_FLAG_ALPHA;
4074 }
4075 }
4076
4077 else if (do_local_compose != 0) /* internal error */
4078 png_error(png_ptr, "png_image_read: alpha channel lost");
4079
4080 if ((format & PNG_FORMAT_FLAG_ASSOCIATED_ALPHA) != 0) {
4081 info_format |= PNG_FORMAT_FLAG_ASSOCIATED_ALPHA;
4082 }
4083
4084 if (info_ptr->bit_depth == 16)
4085 info_format |= PNG_FORMAT_FLAG_LINEAR;
4086
4087 #ifdef PNG_FORMAT_BGR_SUPPORTED
4088 if ((png_ptr->transformations & PNG_BGR) != 0)
4089 info_format |= PNG_FORMAT_FLAG_BGR;
4090 #endif
4091
4092 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
4093 if (do_local_background == 2)
4094 {
4095 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
4096 info_format |= PNG_FORMAT_FLAG_AFIRST;
4097 }
4098
4099 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4100 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4101 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4102 {
4103 if (do_local_background == 2)
4104 png_error(png_ptr, "unexpected alpha swap transformation");
4105
4106 info_format |= PNG_FORMAT_FLAG_AFIRST;
4107 }
4108 # endif
4109
4110 /* This is actually an internal error. */
4111 if (info_format != format)
4112 png_error(png_ptr, "png_read_image: invalid transformations");
4113 }
4114
4115 /* Now read the rows. If do_local_compose is set then it is necessary to use
4116 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4117 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4118 * display acts as a flag.
4119 */
4120 {
4121 png_voidp first_row = display->buffer;
4122 ptrdiff_t row_bytes = display->row_stride;
4123
4124 if (linear != 0)
4125 row_bytes *= 2;
4126
4127 /* The following expression is designed to work correctly whether it gives
4128 * a signed or an unsigned result.
4129 */
4130 if (row_bytes < 0)
4131 {
4132 char *ptr = png_voidcast(char*, first_row);
4133 ptr += (image->height-1) * (-row_bytes);
4134 first_row = png_voidcast(png_voidp, ptr);
4135 }
4136
4137 display->first_row = first_row;
4138 display->row_bytes = row_bytes;
4139 }
4140
4141 if (do_local_compose != 0)
4142 {
4143 int result;
4144 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4145
4146 display->local_row = row;
4147 result = png_safe_execute(image, png_image_read_composite, display);
4148 display->local_row = NULL;
4149 png_free(png_ptr, row);
4150
4151 return result;
4152 }
4153
4154 else if (do_local_background == 2)
4155 {
4156 int result;
4157 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4158
4159 display->local_row = row;
4160 result = png_safe_execute(image, png_image_read_background, display);
4161 display->local_row = NULL;
4162 png_free(png_ptr, row);
4163
4164 return result;
4165 }
4166
4167 else
4168 {
4169 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
4170
4171 while (--passes >= 0)
4172 {
4173 png_uint_32 y = image->height;
4174 png_bytep row = png_voidcast(png_bytep, display->first_row);
4175
4176 for (; y > 0; --y)
4177 {
4178 png_read_row(png_ptr, row, NULL);
4179 row += row_bytes;
4180 }
4181 }
4182
4183 return 1;
4184 }
4185 }
4186
4187 int PNGAPI
png_image_finish_read(png_imagep image,png_const_colorp background,void * buffer,png_int_32 row_stride,void * colormap)4188 png_image_finish_read(png_imagep image, png_const_colorp background,
4189 void *buffer, png_int_32 row_stride, void *colormap)
4190 {
4191 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4192 {
4193 /* Check for row_stride overflow. This check is not performed on the
4194 * original PNG format because it may not occur in the output PNG format
4195 * and libpng deals with the issues of reading the original.
4196 */
4197 unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4198
4199 /* The following checks just the 'row_stride' calculation to ensure it
4200 * fits in a signed 32-bit value. Because channels/components can be
4201 * either 1 or 2 bytes in size the length of a row can still overflow 32
4202 * bits; this is just to verify that the 'row_stride' argument can be
4203 * represented.
4204 */
4205 if (image->width <= 0x7fffffffU/channels) /* no overflow */
4206 {
4207 png_uint_32 check;
4208 png_uint_32 png_row_stride = image->width * channels;
4209
4210 if (row_stride == 0)
4211 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4212
4213 if (row_stride < 0)
4214 check = (png_uint_32)(-row_stride);
4215
4216 else
4217 check = (png_uint_32)row_stride;
4218
4219 /* This verifies 'check', the absolute value of the actual stride
4220 * passed in and detects overflow in the application calculation (i.e.
4221 * if the app did actually pass in a non-zero 'row_stride'.
4222 */
4223 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4224 {
4225 /* Now check for overflow of the image buffer calculation; this
4226 * limits the whole image size to 32 bits for API compatibility with
4227 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4228 *
4229 * The PNG_IMAGE_BUFFER_SIZE macro is:
4230 *
4231 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4232 *
4233 * And the component size is always 1 or 2, so make sure that the
4234 * number of *bytes* that the application is saying are available
4235 * does actually fit into a 32-bit number.
4236 *
4237 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4238 * will be changed to use png_alloc_size_t; bigger images can be
4239 * accommodated on 64-bit systems.
4240 */
4241 if (image->height <=
4242 0xffffffffU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
4243 {
4244 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4245 (image->colormap_entries > 0 && colormap != NULL))
4246 {
4247 int result;
4248 png_image_read_control display;
4249
4250 memset(&display, 0, (sizeof display));
4251 display.image = image;
4252 display.buffer = buffer;
4253 display.row_stride = row_stride;
4254 display.colormap = colormap;
4255 display.background = background;
4256 display.local_row = NULL;
4257
4258 /* Choose the correct 'end' routine; for the color-map case
4259 * all the setup has already been done.
4260 */
4261 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4262 result =
4263 png_safe_execute(image,
4264 png_image_read_colormap, &display) &&
4265 png_safe_execute(image,
4266 png_image_read_colormapped, &display);
4267
4268 else
4269 result =
4270 png_safe_execute(image,
4271 png_image_read_direct, &display);
4272
4273 png_image_free(image);
4274 return result;
4275 }
4276
4277 else
4278 return png_image_error(image,
4279 "png_image_finish_read[color-map]: no color-map");
4280 }
4281
4282 else
4283 return png_image_error(image,
4284 "png_image_finish_read: image too large");
4285 }
4286
4287 else
4288 return png_image_error(image,
4289 "png_image_finish_read: invalid argument");
4290 }
4291
4292 else
4293 return png_image_error(image,
4294 "png_image_finish_read: row_stride too large");
4295 }
4296
4297 else if (image != NULL)
4298 return png_image_error(image,
4299 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4300
4301 return 0;
4302 }
4303
4304 #endif /* SIMPLIFIED_READ */
4305 #endif /* READ */
4306