1
2 /* pngread.c - read a PNG file
3 *
4 * Last changed in libpng 1.6.24 [August 4, 2016]
5 * Copyright (c) 1998-2002,2004,2006-2016 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 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 png_ptr->idat_size = length;
165 break;
166 }
167
168 #ifdef PNG_READ_bKGD_SUPPORTED
169 else if (chunk_name == png_bKGD)
170 png_handle_bKGD(png_ptr, info_ptr, length);
171 #endif
172
173 #ifdef PNG_READ_cHRM_SUPPORTED
174 else if (chunk_name == png_cHRM)
175 png_handle_cHRM(png_ptr, info_ptr, length);
176 #endif
177
178 #ifdef PNG_READ_gAMA_SUPPORTED
179 else if (chunk_name == png_gAMA)
180 png_handle_gAMA(png_ptr, info_ptr, length);
181 #endif
182
183 #ifdef PNG_READ_hIST_SUPPORTED
184 else if (chunk_name == png_hIST)
185 png_handle_hIST(png_ptr, info_ptr, length);
186 #endif
187
188 #ifdef PNG_READ_oFFs_SUPPORTED
189 else if (chunk_name == png_oFFs)
190 png_handle_oFFs(png_ptr, info_ptr, length);
191 #endif
192
193 #ifdef PNG_READ_pCAL_SUPPORTED
194 else if (chunk_name == png_pCAL)
195 png_handle_pCAL(png_ptr, info_ptr, length);
196 #endif
197
198 #ifdef PNG_READ_sCAL_SUPPORTED
199 else if (chunk_name == png_sCAL)
200 png_handle_sCAL(png_ptr, info_ptr, length);
201 #endif
202
203 #ifdef PNG_READ_pHYs_SUPPORTED
204 else if (chunk_name == png_pHYs)
205 png_handle_pHYs(png_ptr, info_ptr, length);
206 #endif
207
208 #ifdef PNG_READ_sBIT_SUPPORTED
209 else if (chunk_name == png_sBIT)
210 png_handle_sBIT(png_ptr, info_ptr, length);
211 #endif
212
213 #ifdef PNG_READ_sRGB_SUPPORTED
214 else if (chunk_name == png_sRGB)
215 png_handle_sRGB(png_ptr, info_ptr, length);
216 #endif
217
218 #ifdef PNG_READ_iCCP_SUPPORTED
219 else if (chunk_name == png_iCCP)
220 png_handle_iCCP(png_ptr, info_ptr, length);
221 #endif
222
223 #ifdef PNG_READ_sPLT_SUPPORTED
224 else if (chunk_name == png_sPLT)
225 png_handle_sPLT(png_ptr, info_ptr, length);
226 #endif
227
228 #ifdef PNG_READ_tEXt_SUPPORTED
229 else if (chunk_name == png_tEXt)
230 png_handle_tEXt(png_ptr, info_ptr, length);
231 #endif
232
233 #ifdef PNG_READ_tIME_SUPPORTED
234 else if (chunk_name == png_tIME)
235 png_handle_tIME(png_ptr, info_ptr, length);
236 #endif
237
238 #ifdef PNG_READ_tRNS_SUPPORTED
239 else if (chunk_name == png_tRNS)
240 png_handle_tRNS(png_ptr, info_ptr, length);
241 #endif
242
243 #ifdef PNG_READ_zTXt_SUPPORTED
244 else if (chunk_name == png_zTXt)
245 png_handle_zTXt(png_ptr, info_ptr, length);
246 #endif
247
248 #ifdef PNG_READ_iTXt_SUPPORTED
249 else if (chunk_name == png_iTXt)
250 png_handle_iTXt(png_ptr, info_ptr, length);
251 #endif
252
253 else
254 png_handle_unknown(png_ptr, info_ptr, length,
255 PNG_HANDLE_CHUNK_AS_DEFAULT);
256 }
257 }
258 #endif /* SEQUENTIAL_READ */
259
260 /* Optional call to update the users info_ptr structure */
261 void PNGAPI
png_read_update_info(png_structrp png_ptr,png_inforp info_ptr)262 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
263 {
264 png_debug(1, "in png_read_update_info");
265
266 if (png_ptr != NULL)
267 {
268 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
269 {
270 png_read_start_row(png_ptr);
271
272 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
273 png_read_transform_info(png_ptr, info_ptr);
274 # else
275 PNG_UNUSED(info_ptr)
276 # endif
277 }
278
279 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
280 else
281 png_app_error(png_ptr,
282 "png_read_update_info/png_start_read_image: duplicate call");
283 }
284 }
285
286 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
287 /* Initialize palette, background, etc, after transformations
288 * are set, but before any reading takes place. This allows
289 * the user to obtain a gamma-corrected palette, for example.
290 * If the user doesn't call this, we will do it ourselves.
291 */
292 void PNGAPI
png_start_read_image(png_structrp png_ptr)293 png_start_read_image(png_structrp png_ptr)
294 {
295 png_debug(1, "in png_start_read_image");
296
297 if (png_ptr != NULL)
298 {
299 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
300 png_read_start_row(png_ptr);
301
302 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
303 else
304 png_app_error(png_ptr,
305 "png_start_read_image/png_read_update_info: duplicate call");
306 }
307 }
308 #endif /* SEQUENTIAL_READ */
309
310 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
311 #ifdef PNG_MNG_FEATURES_SUPPORTED
312 /* Undoes intrapixel differencing,
313 * NOTE: this is apparently only supported in the 'sequential' reader.
314 */
315 static void
png_do_read_intrapixel(png_row_infop row_info,png_bytep row)316 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
317 {
318 png_debug(1, "in png_do_read_intrapixel");
319
320 if (
321 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
322 {
323 int bytes_per_pixel;
324 png_uint_32 row_width = row_info->width;
325
326 if (row_info->bit_depth == 8)
327 {
328 png_bytep rp;
329 png_uint_32 i;
330
331 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
332 bytes_per_pixel = 3;
333
334 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
335 bytes_per_pixel = 4;
336
337 else
338 return;
339
340 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
341 {
342 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
343 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
344 }
345 }
346 else if (row_info->bit_depth == 16)
347 {
348 png_bytep rp;
349 png_uint_32 i;
350
351 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
352 bytes_per_pixel = 6;
353
354 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
355 bytes_per_pixel = 8;
356
357 else
358 return;
359
360 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
361 {
362 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
363 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
364 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
365 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
366 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
367 *(rp ) = (png_byte)((red >> 8) & 0xff);
368 *(rp + 1) = (png_byte)(red & 0xff);
369 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
370 *(rp + 5) = (png_byte)(blue & 0xff);
371 }
372 }
373 }
374 }
375 #endif /* MNG_FEATURES */
376
377 void PNGAPI
png_read_row(png_structrp png_ptr,png_bytep row,png_bytep dsp_row)378 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
379 {
380 png_row_info row_info;
381
382 if (png_ptr == NULL)
383 return;
384
385 png_debug2(1, "in png_read_row (row %lu, pass %d)",
386 (unsigned long)png_ptr->row_number, png_ptr->pass);
387
388 /* png_read_start_row sets the information (in particular iwidth) for this
389 * interlace pass.
390 */
391 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
392 png_read_start_row(png_ptr);
393
394 /* 1.5.6: row_info moved out of png_struct to a local here. */
395 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
396 row_info.color_type = png_ptr->color_type;
397 row_info.bit_depth = png_ptr->bit_depth;
398 row_info.channels = png_ptr->channels;
399 row_info.pixel_depth = png_ptr->pixel_depth;
400 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
401
402 #ifdef PNG_WARNINGS_SUPPORTED
403 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
404 {
405 /* Check for transforms that have been set but were defined out */
406 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
407 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
408 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
409 #endif
410
411 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
412 if ((png_ptr->transformations & PNG_FILLER) != 0)
413 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
414 #endif
415
416 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
417 !defined(PNG_READ_PACKSWAP_SUPPORTED)
418 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
419 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
420 #endif
421
422 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
423 if ((png_ptr->transformations & PNG_PACK) != 0)
424 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
425 #endif
426
427 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
428 if ((png_ptr->transformations & PNG_SHIFT) != 0)
429 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
430 #endif
431
432 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
433 if ((png_ptr->transformations & PNG_BGR) != 0)
434 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
435 #endif
436
437 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
438 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
439 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
440 #endif
441 }
442 #endif /* WARNINGS */
443
444 #ifdef PNG_READ_INTERLACING_SUPPORTED
445 /* If interlaced and we do not need a new row, combine row and return.
446 * Notice that the pixels we have from previous rows have been transformed
447 * already; we can only combine like with like (transformed or
448 * untransformed) and, because of the libpng API for interlaced images, this
449 * means we must transform before de-interlacing.
450 */
451 if (png_ptr->interlaced != 0 &&
452 (png_ptr->transformations & PNG_INTERLACE) != 0)
453 {
454 switch (png_ptr->pass)
455 {
456 case 0:
457 if (png_ptr->row_number & 0x07)
458 {
459 if (dsp_row != NULL)
460 png_combine_row(png_ptr, dsp_row, 1/*display*/);
461 png_read_finish_row(png_ptr);
462 return;
463 }
464 break;
465
466 case 1:
467 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
468 {
469 if (dsp_row != NULL)
470 png_combine_row(png_ptr, dsp_row, 1/*display*/);
471
472 png_read_finish_row(png_ptr);
473 return;
474 }
475 break;
476
477 case 2:
478 if ((png_ptr->row_number & 0x07) != 4)
479 {
480 if (dsp_row != NULL && (png_ptr->row_number & 4))
481 png_combine_row(png_ptr, dsp_row, 1/*display*/);
482
483 png_read_finish_row(png_ptr);
484 return;
485 }
486 break;
487
488 case 3:
489 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
490 {
491 if (dsp_row != NULL)
492 png_combine_row(png_ptr, dsp_row, 1/*display*/);
493
494 png_read_finish_row(png_ptr);
495 return;
496 }
497 break;
498
499 case 4:
500 if ((png_ptr->row_number & 3) != 2)
501 {
502 if (dsp_row != NULL && (png_ptr->row_number & 2))
503 png_combine_row(png_ptr, dsp_row, 1/*display*/);
504
505 png_read_finish_row(png_ptr);
506 return;
507 }
508 break;
509
510 case 5:
511 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
512 {
513 if (dsp_row != NULL)
514 png_combine_row(png_ptr, dsp_row, 1/*display*/);
515
516 png_read_finish_row(png_ptr);
517 return;
518 }
519 break;
520
521 default:
522 case 6:
523 if ((png_ptr->row_number & 1) == 0)
524 {
525 png_read_finish_row(png_ptr);
526 return;
527 }
528 break;
529 }
530 }
531 #endif
532
533 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
534 png_error(png_ptr, "Invalid attempt to read row data");
535
536 /* Fill the row with IDAT data: */
537 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
538
539 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
540 {
541 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
542 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
543 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
544 else
545 png_error(png_ptr, "bad adaptive filter value");
546 }
547
548 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
549 * 1.5.6, while the buffer really is this big in current versions of libpng
550 * it may not be in the future, so this was changed just to copy the
551 * interlaced count:
552 */
553 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
554
555 #ifdef PNG_MNG_FEATURES_SUPPORTED
556 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
557 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
558 {
559 /* Intrapixel differencing */
560 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
561 }
562 #endif
563
564 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
565 if (png_ptr->transformations)
566 png_do_read_transformations(png_ptr, &row_info);
567 #endif
568
569 /* The transformed pixel depth should match the depth now in row_info. */
570 if (png_ptr->transformed_pixel_depth == 0)
571 {
572 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
573 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
574 png_error(png_ptr, "sequential row overflow");
575 }
576
577 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
578 png_error(png_ptr, "internal sequential row size calculation error");
579
580 #ifdef PNG_READ_INTERLACING_SUPPORTED
581 /* Expand interlaced rows to full size */
582 if (png_ptr->interlaced != 0 &&
583 (png_ptr->transformations & PNG_INTERLACE) != 0)
584 {
585 if (png_ptr->pass < 6)
586 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
587 png_ptr->transformations);
588
589 if (dsp_row != NULL)
590 png_combine_row(png_ptr, dsp_row, 1/*display*/);
591
592 if (row != NULL)
593 png_combine_row(png_ptr, row, 0/*row*/);
594 }
595
596 else
597 #endif
598 {
599 if (row != NULL)
600 png_combine_row(png_ptr, row, -1/*ignored*/);
601
602 if (dsp_row != NULL)
603 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
604 }
605 png_read_finish_row(png_ptr);
606
607 if (png_ptr->read_row_fn != NULL)
608 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
609
610 }
611 #endif /* SEQUENTIAL_READ */
612
613 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
614 /* Read one or more rows of image data. If the image is interlaced,
615 * and png_set_interlace_handling() has been called, the rows need to
616 * contain the contents of the rows from the previous pass. If the
617 * image has alpha or transparency, and png_handle_alpha()[*] has been
618 * called, the rows contents must be initialized to the contents of the
619 * screen.
620 *
621 * "row" holds the actual image, and pixels are placed in it
622 * as they arrive. If the image is displayed after each pass, it will
623 * appear to "sparkle" in. "display_row" can be used to display a
624 * "chunky" progressive image, with finer detail added as it becomes
625 * available. If you do not want this "chunky" display, you may pass
626 * NULL for display_row. If you do not want the sparkle display, and
627 * you have not called png_handle_alpha(), you may pass NULL for rows.
628 * If you have called png_handle_alpha(), and the image has either an
629 * alpha channel or a transparency chunk, you must provide a buffer for
630 * rows. In this case, you do not have to provide a display_row buffer
631 * also, but you may. If the image is not interlaced, or if you have
632 * not called png_set_interlace_handling(), the display_row buffer will
633 * be ignored, so pass NULL to it.
634 *
635 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
636 */
637
638 void PNGAPI
png_read_rows(png_structrp png_ptr,png_bytepp row,png_bytepp display_row,png_uint_32 num_rows)639 png_read_rows(png_structrp png_ptr, png_bytepp row,
640 png_bytepp display_row, png_uint_32 num_rows)
641 {
642 png_uint_32 i;
643 png_bytepp rp;
644 png_bytepp dp;
645
646 png_debug(1, "in png_read_rows");
647
648 if (png_ptr == NULL)
649 return;
650
651 rp = row;
652 dp = display_row;
653 if (rp != NULL && dp != NULL)
654 for (i = 0; i < num_rows; i++)
655 {
656 png_bytep rptr = *rp++;
657 png_bytep dptr = *dp++;
658
659 png_read_row(png_ptr, rptr, dptr);
660 }
661
662 else if (rp != NULL)
663 for (i = 0; i < num_rows; i++)
664 {
665 png_bytep rptr = *rp;
666 png_read_row(png_ptr, rptr, NULL);
667 rp++;
668 }
669
670 else if (dp != NULL)
671 for (i = 0; i < num_rows; i++)
672 {
673 png_bytep dptr = *dp;
674 png_read_row(png_ptr, NULL, dptr);
675 dp++;
676 }
677 }
678 #endif /* SEQUENTIAL_READ */
679
680 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
681 /* Read the entire image. If the image has an alpha channel or a tRNS
682 * chunk, and you have called png_handle_alpha()[*], you will need to
683 * initialize the image to the current image that PNG will be overlaying.
684 * We set the num_rows again here, in case it was incorrectly set in
685 * png_read_start_row() by a call to png_read_update_info() or
686 * png_start_read_image() if png_set_interlace_handling() wasn't called
687 * prior to either of these functions like it should have been. You can
688 * only call this function once. If you desire to have an image for
689 * each pass of a interlaced image, use png_read_rows() instead.
690 *
691 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
692 */
693 void PNGAPI
png_read_image(png_structrp png_ptr,png_bytepp image)694 png_read_image(png_structrp png_ptr, png_bytepp image)
695 {
696 png_uint_32 i, image_height;
697 int pass, j;
698 png_bytepp rp;
699
700 png_debug(1, "in png_read_image");
701
702 if (png_ptr == NULL)
703 return;
704
705 #ifdef PNG_READ_INTERLACING_SUPPORTED
706 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
707 {
708 pass = png_set_interlace_handling(png_ptr);
709 /* And make sure transforms are initialized. */
710 png_start_read_image(png_ptr);
711 }
712 else
713 {
714 if (png_ptr->interlaced != 0 &&
715 (png_ptr->transformations & PNG_INTERLACE) == 0)
716 {
717 /* Caller called png_start_read_image or png_read_update_info without
718 * first turning on the PNG_INTERLACE transform. We can fix this here,
719 * but the caller should do it!
720 */
721 png_warning(png_ptr, "Interlace handling should be turned on when "
722 "using png_read_image");
723 /* Make sure this is set correctly */
724 png_ptr->num_rows = png_ptr->height;
725 }
726
727 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
728 * the above error case.
729 */
730 pass = png_set_interlace_handling(png_ptr);
731 }
732 #else
733 if (png_ptr->interlaced)
734 png_error(png_ptr,
735 "Cannot read interlaced image -- interlace handler disabled");
736
737 pass = 1;
738 #endif
739
740 image_height=png_ptr->height;
741
742 for (j = 0; j < pass; j++)
743 {
744 rp = image;
745 for (i = 0; i < image_height; i++)
746 {
747 png_read_row(png_ptr, *rp, NULL);
748 rp++;
749 }
750 }
751 }
752 #endif /* SEQUENTIAL_READ */
753
754 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
755 /* Read the end of the PNG file. Will not read past the end of the
756 * file, will verify the end is accurate, and will read any comments
757 * or time information at the end of the file, if info is not NULL.
758 */
759 void PNGAPI
png_read_end(png_structrp png_ptr,png_inforp info_ptr)760 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
761 {
762 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
763 int keep;
764 #endif
765
766 png_debug(1, "in png_read_end");
767
768 if (png_ptr == NULL)
769 return;
770
771 /* If png_read_end is called in the middle of reading the rows there may
772 * still be pending IDAT data and an owned zstream. Deal with this here.
773 */
774 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
775 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
776 #endif
777 png_read_finish_IDAT(png_ptr);
778
779 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
780 /* Report invalid palette index; added at libng-1.5.10 */
781 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
782 png_ptr->num_palette_max > png_ptr->num_palette)
783 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
784 #endif
785
786 do
787 {
788 png_uint_32 length = png_read_chunk_header(png_ptr);
789 png_uint_32 chunk_name = png_ptr->chunk_name;
790
791 if (chunk_name != png_IDAT)
792 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
793
794 if (chunk_name == png_IEND)
795 png_handle_IEND(png_ptr, info_ptr, length);
796
797 else if (chunk_name == png_IHDR)
798 png_handle_IHDR(png_ptr, info_ptr, length);
799
800 else if (info_ptr == NULL)
801 png_crc_finish(png_ptr, length);
802
803 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
804 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
805 {
806 if (chunk_name == png_IDAT)
807 {
808 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
809 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
810 png_benign_error(png_ptr, ".Too many IDATs found");
811 }
812 png_handle_unknown(png_ptr, info_ptr, length, keep);
813 if (chunk_name == png_PLTE)
814 png_ptr->mode |= PNG_HAVE_PLTE;
815 }
816 #endif
817
818 else if (chunk_name == png_IDAT)
819 {
820 /* Zero length IDATs are legal after the last IDAT has been
821 * read, but not after other chunks have been read. 1.6 does not
822 * always read all the deflate data; specifically it cannot be relied
823 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
824 * chunks which are longer than zero as well:
825 */
826 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
827 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
828 png_benign_error(png_ptr, "..Too many IDATs found");
829
830 png_crc_finish(png_ptr, length);
831 }
832 else if (chunk_name == png_PLTE)
833 png_handle_PLTE(png_ptr, info_ptr, length);
834
835 #ifdef PNG_READ_bKGD_SUPPORTED
836 else if (chunk_name == png_bKGD)
837 png_handle_bKGD(png_ptr, info_ptr, length);
838 #endif
839
840 #ifdef PNG_READ_cHRM_SUPPORTED
841 else if (chunk_name == png_cHRM)
842 png_handle_cHRM(png_ptr, info_ptr, length);
843 #endif
844
845 #ifdef PNG_READ_gAMA_SUPPORTED
846 else if (chunk_name == png_gAMA)
847 png_handle_gAMA(png_ptr, info_ptr, length);
848 #endif
849
850 #ifdef PNG_READ_hIST_SUPPORTED
851 else if (chunk_name == png_hIST)
852 png_handle_hIST(png_ptr, info_ptr, length);
853 #endif
854
855 #ifdef PNG_READ_oFFs_SUPPORTED
856 else if (chunk_name == png_oFFs)
857 png_handle_oFFs(png_ptr, info_ptr, length);
858 #endif
859
860 #ifdef PNG_READ_pCAL_SUPPORTED
861 else if (chunk_name == png_pCAL)
862 png_handle_pCAL(png_ptr, info_ptr, length);
863 #endif
864
865 #ifdef PNG_READ_sCAL_SUPPORTED
866 else if (chunk_name == png_sCAL)
867 png_handle_sCAL(png_ptr, info_ptr, length);
868 #endif
869
870 #ifdef PNG_READ_pHYs_SUPPORTED
871 else if (chunk_name == png_pHYs)
872 png_handle_pHYs(png_ptr, info_ptr, length);
873 #endif
874
875 #ifdef PNG_READ_sBIT_SUPPORTED
876 else if (chunk_name == png_sBIT)
877 png_handle_sBIT(png_ptr, info_ptr, length);
878 #endif
879
880 #ifdef PNG_READ_sRGB_SUPPORTED
881 else if (chunk_name == png_sRGB)
882 png_handle_sRGB(png_ptr, info_ptr, length);
883 #endif
884
885 #ifdef PNG_READ_iCCP_SUPPORTED
886 else if (chunk_name == png_iCCP)
887 png_handle_iCCP(png_ptr, info_ptr, length);
888 #endif
889
890 #ifdef PNG_READ_sPLT_SUPPORTED
891 else if (chunk_name == png_sPLT)
892 png_handle_sPLT(png_ptr, info_ptr, length);
893 #endif
894
895 #ifdef PNG_READ_tEXt_SUPPORTED
896 else if (chunk_name == png_tEXt)
897 png_handle_tEXt(png_ptr, info_ptr, length);
898 #endif
899
900 #ifdef PNG_READ_tIME_SUPPORTED
901 else if (chunk_name == png_tIME)
902 png_handle_tIME(png_ptr, info_ptr, length);
903 #endif
904
905 #ifdef PNG_READ_tRNS_SUPPORTED
906 else if (chunk_name == png_tRNS)
907 png_handle_tRNS(png_ptr, info_ptr, length);
908 #endif
909
910 #ifdef PNG_READ_zTXt_SUPPORTED
911 else if (chunk_name == png_zTXt)
912 png_handle_zTXt(png_ptr, info_ptr, length);
913 #endif
914
915 #ifdef PNG_READ_iTXt_SUPPORTED
916 else if (chunk_name == png_iTXt)
917 png_handle_iTXt(png_ptr, info_ptr, length);
918 #endif
919
920 else
921 png_handle_unknown(png_ptr, info_ptr, length,
922 PNG_HANDLE_CHUNK_AS_DEFAULT);
923 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
924 }
925 #endif /* SEQUENTIAL_READ */
926
927 /* Free all memory used in the read struct */
928 static void
png_read_destroy(png_structrp png_ptr)929 png_read_destroy(png_structrp png_ptr)
930 {
931 png_debug(1, "in png_read_destroy");
932
933 #ifdef PNG_READ_GAMMA_SUPPORTED
934 png_destroy_gamma_table(png_ptr);
935 #endif
936
937 png_free(png_ptr, png_ptr->big_row_buf);
938 png_ptr->big_row_buf = NULL;
939 png_free(png_ptr, png_ptr->big_prev_row);
940 png_ptr->big_prev_row = NULL;
941 png_free(png_ptr, png_ptr->read_buffer);
942 png_ptr->read_buffer = NULL;
943
944 #ifdef PNG_READ_QUANTIZE_SUPPORTED
945 png_free(png_ptr, png_ptr->palette_lookup);
946 png_ptr->palette_lookup = NULL;
947 png_free(png_ptr, png_ptr->quantize_index);
948 png_ptr->quantize_index = NULL;
949 #endif
950
951 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
952 {
953 png_zfree(png_ptr, png_ptr->palette);
954 png_ptr->palette = NULL;
955 }
956 png_ptr->free_me &= ~PNG_FREE_PLTE;
957
958 #if defined(PNG_tRNS_SUPPORTED) || \
959 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
960 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
961 {
962 png_free(png_ptr, png_ptr->trans_alpha);
963 png_ptr->trans_alpha = NULL;
964 }
965 png_ptr->free_me &= ~PNG_FREE_TRNS;
966 #endif
967
968 inflateEnd(&png_ptr->zstream);
969
970 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
971 png_free(png_ptr, png_ptr->save_buffer);
972 png_ptr->save_buffer = NULL;
973 #endif
974
975 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
976 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
977 png_free(png_ptr, png_ptr->unknown_chunk.data);
978 png_ptr->unknown_chunk.data = NULL;
979 #endif
980
981 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
982 png_free(png_ptr, png_ptr->chunk_list);
983 png_ptr->chunk_list = NULL;
984 #endif
985
986 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
987 * callbacks are still set at this point. They are required to complete the
988 * destruction of the png_struct itself.
989 */
990 }
991
992 /* Free all memory used by the read */
993 void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr,png_infopp info_ptr_ptr,png_infopp end_info_ptr_ptr)994 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
995 png_infopp end_info_ptr_ptr)
996 {
997 png_structrp png_ptr = NULL;
998
999 png_debug(1, "in png_destroy_read_struct");
1000
1001 if (png_ptr_ptr != NULL)
1002 png_ptr = *png_ptr_ptr;
1003
1004 if (png_ptr == NULL)
1005 return;
1006
1007 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1008 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1009 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1010 */
1011 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1012 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1013
1014 *png_ptr_ptr = NULL;
1015 png_read_destroy(png_ptr);
1016 png_destroy_png_struct(png_ptr);
1017 }
1018
1019 void PNGAPI
png_set_read_status_fn(png_structrp png_ptr,png_read_status_ptr read_row_fn)1020 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1021 {
1022 if (png_ptr == NULL)
1023 return;
1024
1025 png_ptr->read_row_fn = read_row_fn;
1026 }
1027
1028
1029 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1030 #ifdef PNG_INFO_IMAGE_SUPPORTED
1031 void PNGAPI
png_read_png(png_structrp png_ptr,png_inforp info_ptr,int transforms,voidp params)1032 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1033 int transforms, voidp params)
1034 {
1035 if (png_ptr == NULL || info_ptr == NULL)
1036 return;
1037
1038 /* png_read_info() gives us all of the information from the
1039 * PNG file before the first IDAT (image data chunk).
1040 */
1041 png_read_info(png_ptr, info_ptr);
1042 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1043 png_error(png_ptr, "Image is too high to process with png_read_png()");
1044
1045 /* -------------- image transformations start here ------------------- */
1046 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1047 * is not implemented. This will only happen in de-configured (non-default)
1048 * libpng builds. The results can be unexpected - png_read_png may return
1049 * short or mal-formed rows because the transform is skipped.
1050 */
1051
1052 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1053 */
1054 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1055 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1056 * did in earlier versions, while "scale_16" is now more accurate.
1057 */
1058 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1059 png_set_scale_16(png_ptr);
1060 #else
1061 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1062 #endif
1063
1064 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1065 * latter by doing SCALE first. This is ok and allows apps not to check for
1066 * which is supported to get the right answer.
1067 */
1068 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1069 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1070 png_set_strip_16(png_ptr);
1071 #else
1072 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1073 #endif
1074
1075 /* Strip alpha bytes from the input data without combining with
1076 * the background (not recommended).
1077 */
1078 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1079 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1080 png_set_strip_alpha(png_ptr);
1081 #else
1082 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1083 #endif
1084
1085 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1086 * byte into separate bytes (useful for paletted and grayscale images).
1087 */
1088 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1089 #ifdef PNG_READ_PACK_SUPPORTED
1090 png_set_packing(png_ptr);
1091 #else
1092 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1093 #endif
1094
1095 /* Change the order of packed pixels to least significant bit first
1096 * (not useful if you are using png_set_packing).
1097 */
1098 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1099 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1100 png_set_packswap(png_ptr);
1101 #else
1102 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1103 #endif
1104
1105 /* Expand paletted colors into true RGB triplets
1106 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1107 * Expand paletted or RGB images with transparency to full alpha
1108 * channels so the data will be available as RGBA quartets.
1109 */
1110 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1111 #ifdef PNG_READ_EXPAND_SUPPORTED
1112 png_set_expand(png_ptr);
1113 #else
1114 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1115 #endif
1116
1117 /* We don't handle background color or gamma transformation or quantizing.
1118 */
1119
1120 /* Invert monochrome files to have 0 as white and 1 as black
1121 */
1122 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1123 #ifdef PNG_READ_INVERT_SUPPORTED
1124 png_set_invert_mono(png_ptr);
1125 #else
1126 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1127 #endif
1128
1129 /* If you want to shift the pixel values from the range [0,255] or
1130 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1131 * colors were originally in:
1132 */
1133 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1134 #ifdef PNG_READ_SHIFT_SUPPORTED
1135 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1136 png_set_shift(png_ptr, &info_ptr->sig_bit);
1137 #else
1138 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1139 #endif
1140
1141 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1142 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1143 #ifdef PNG_READ_BGR_SUPPORTED
1144 png_set_bgr(png_ptr);
1145 #else
1146 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1147 #endif
1148
1149 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1150 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1151 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1152 png_set_swap_alpha(png_ptr);
1153 #else
1154 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1155 #endif
1156
1157 /* Swap bytes of 16-bit files to least significant byte first */
1158 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1159 #ifdef PNG_READ_SWAP_SUPPORTED
1160 png_set_swap(png_ptr);
1161 #else
1162 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1163 #endif
1164
1165 /* Added at libpng-1.2.41 */
1166 /* Invert the alpha channel from opacity to transparency */
1167 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1168 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1169 png_set_invert_alpha(png_ptr);
1170 #else
1171 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1172 #endif
1173
1174 /* Added at libpng-1.2.41 */
1175 /* Expand grayscale image to RGB */
1176 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1177 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1178 png_set_gray_to_rgb(png_ptr);
1179 #else
1180 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1181 #endif
1182
1183 /* Added at libpng-1.5.4 */
1184 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1185 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1186 png_set_expand_16(png_ptr);
1187 #else
1188 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1189 #endif
1190
1191 /* We don't handle adding filler bytes */
1192
1193 /* We use png_read_image and rely on that for interlace handling, but we also
1194 * call png_read_update_info therefore must turn on interlace handling now:
1195 */
1196 (void)png_set_interlace_handling(png_ptr);
1197
1198 /* Optional call to gamma correct and add the background to the palette
1199 * and update info structure. REQUIRED if you are expecting libpng to
1200 * update the palette for you (i.e., you selected such a transform above).
1201 */
1202 png_read_update_info(png_ptr, info_ptr);
1203
1204 /* -------------- image transformations end here ------------------- */
1205
1206 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1207 if (info_ptr->row_pointers == NULL)
1208 {
1209 png_uint_32 iptr;
1210
1211 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1212 info_ptr->height * (sizeof (png_bytep))));
1213
1214 for (iptr=0; iptr<info_ptr->height; iptr++)
1215 info_ptr->row_pointers[iptr] = NULL;
1216
1217 info_ptr->free_me |= PNG_FREE_ROWS;
1218
1219 for (iptr = 0; iptr < info_ptr->height; iptr++)
1220 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1221 png_malloc(png_ptr, info_ptr->rowbytes));
1222 }
1223
1224 png_read_image(png_ptr, info_ptr->row_pointers);
1225 info_ptr->valid |= PNG_INFO_IDAT;
1226
1227 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1228 png_read_end(png_ptr, info_ptr);
1229
1230 PNG_UNUSED(params)
1231 }
1232 #endif /* INFO_IMAGE */
1233 #endif /* SEQUENTIAL_READ */
1234
1235 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1236 /* SIMPLIFIED READ
1237 *
1238 * This code currently relies on the sequential reader, though it could easily
1239 * be made to work with the progressive one.
1240 */
1241 /* Arguments to png_image_finish_read: */
1242
1243 /* Encoding of PNG data (used by the color-map code) */
1244 # define P_NOTSET 0 /* File encoding not yet known */
1245 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1246 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1247 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1248 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1249
1250 /* Color-map processing: after libpng has run on the PNG image further
1251 * processing may be needed to convert the data to color-map indices.
1252 */
1253 #define PNG_CMAP_NONE 0
1254 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1255 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1256 #define PNG_CMAP_RGB 3 /* Process RGB data */
1257 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1258
1259 /* The following document where the background is for each processing case. */
1260 #define PNG_CMAP_NONE_BACKGROUND 256
1261 #define PNG_CMAP_GA_BACKGROUND 231
1262 #define PNG_CMAP_TRANS_BACKGROUND 254
1263 #define PNG_CMAP_RGB_BACKGROUND 256
1264 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1265
1266 typedef struct
1267 {
1268 /* Arguments: */
1269 png_imagep image;
1270 png_voidp buffer;
1271 png_int_32 row_stride;
1272 png_voidp colormap;
1273 png_const_colorp background;
1274 /* Local variables: */
1275 png_voidp local_row;
1276 png_voidp first_row;
1277 ptrdiff_t row_bytes; /* step between rows */
1278 int file_encoding; /* E_ values above */
1279 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1280 int colormap_processing; /* PNG_CMAP_ values above */
1281 } png_image_read_control;
1282
1283 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1284 * called, so setting up the jmp_buf is not required. This means that anything
1285 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1286 * instead so that control is returned safely back to this routine.
1287 */
1288 static int
png_image_read_init(png_imagep image)1289 png_image_read_init(png_imagep image)
1290 {
1291 if (image->opaque == NULL)
1292 {
1293 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1294 png_safe_error, png_safe_warning);
1295
1296 /* And set the rest of the structure to NULL to ensure that the various
1297 * fields are consistent.
1298 */
1299 memset(image, 0, (sizeof *image));
1300 image->version = PNG_IMAGE_VERSION;
1301
1302 if (png_ptr != NULL)
1303 {
1304 png_infop info_ptr = png_create_info_struct(png_ptr);
1305
1306 if (info_ptr != NULL)
1307 {
1308 png_controlp control = png_voidcast(png_controlp,
1309 png_malloc_warn(png_ptr, (sizeof *control)));
1310
1311 if (control != NULL)
1312 {
1313 memset(control, 0, (sizeof *control));
1314
1315 control->png_ptr = png_ptr;
1316 control->info_ptr = info_ptr;
1317 control->for_write = 0;
1318
1319 image->opaque = control;
1320 return 1;
1321 }
1322
1323 /* Error clean up */
1324 png_destroy_info_struct(png_ptr, &info_ptr);
1325 }
1326
1327 png_destroy_read_struct(&png_ptr, NULL, NULL);
1328 }
1329
1330 return png_image_error(image, "png_image_read: out of memory");
1331 }
1332
1333 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1334 }
1335
1336 /* Utility to find the base format of a PNG file from a png_struct. */
1337 static png_uint_32
png_image_format(png_structrp png_ptr)1338 png_image_format(png_structrp png_ptr)
1339 {
1340 png_uint_32 format = 0;
1341
1342 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1343 format |= PNG_FORMAT_FLAG_COLOR;
1344
1345 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1346 format |= PNG_FORMAT_FLAG_ALPHA;
1347
1348 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1349 * sets the png_struct fields; that's all we are interested in here. The
1350 * precise interaction with an app call to png_set_tRNS and PNG file reading
1351 * is unclear.
1352 */
1353 else if (png_ptr->num_trans > 0)
1354 format |= PNG_FORMAT_FLAG_ALPHA;
1355
1356 if (png_ptr->bit_depth == 16)
1357 format |= PNG_FORMAT_FLAG_LINEAR;
1358
1359 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1360 format |= PNG_FORMAT_FLAG_COLORMAP;
1361
1362 return format;
1363 }
1364
1365 /* Is the given gamma significantly different from sRGB? The test is the same
1366 * one used in pngrtran.c when deciding whether to do gamma correction. The
1367 * arithmetic optimizes the division by using the fact that the inverse of the
1368 * file sRGB gamma is 2.2
1369 */
1370 static int
png_gamma_not_sRGB(png_fixed_point g)1371 png_gamma_not_sRGB(png_fixed_point g)
1372 {
1373 if (g < PNG_FP_1)
1374 {
1375 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1376 if (g == 0)
1377 return 0;
1378
1379 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1380 }
1381
1382 return 1;
1383 }
1384
1385 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1386 * header and fill in all the information. This is executed in a safe context,
1387 * unlike the init routine above.
1388 */
1389 static int
png_image_read_header(png_voidp argument)1390 png_image_read_header(png_voidp argument)
1391 {
1392 png_imagep image = png_voidcast(png_imagep, argument);
1393 png_structrp png_ptr = image->opaque->png_ptr;
1394 png_inforp info_ptr = image->opaque->info_ptr;
1395
1396 png_set_benign_errors(png_ptr, 1/*warn*/);
1397 png_read_info(png_ptr, info_ptr);
1398
1399 /* Do this the fast way; just read directly out of png_struct. */
1400 image->width = png_ptr->width;
1401 image->height = png_ptr->height;
1402
1403 {
1404 png_uint_32 format = png_image_format(png_ptr);
1405
1406 image->format = format;
1407
1408 #ifdef PNG_COLORSPACE_SUPPORTED
1409 /* Does the colorspace match sRGB? If there is no color endpoint
1410 * (colorant) information assume yes, otherwise require the
1411 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1412 * colorspace has been determined to be invalid ignore it.
1413 */
1414 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1415 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1416 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1417 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1418 #endif
1419 }
1420
1421 /* We need the maximum number of entries regardless of the format the
1422 * application sets here.
1423 */
1424 {
1425 png_uint_32 cmap_entries;
1426
1427 switch (png_ptr->color_type)
1428 {
1429 case PNG_COLOR_TYPE_GRAY:
1430 cmap_entries = 1U << png_ptr->bit_depth;
1431 break;
1432
1433 case PNG_COLOR_TYPE_PALETTE:
1434 cmap_entries = png_ptr->num_palette;
1435 break;
1436
1437 default:
1438 cmap_entries = 256;
1439 break;
1440 }
1441
1442 if (cmap_entries > 256)
1443 cmap_entries = 256;
1444
1445 image->colormap_entries = cmap_entries;
1446 }
1447
1448 return 1;
1449 }
1450
1451 #ifdef PNG_STDIO_SUPPORTED
1452 int PNGAPI
png_image_begin_read_from_stdio(png_imagep image,FILE * file)1453 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1454 {
1455 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1456 {
1457 if (file != NULL)
1458 {
1459 if (png_image_read_init(image) != 0)
1460 {
1461 /* This is slightly evil, but png_init_io doesn't do anything other
1462 * than this and we haven't changed the standard IO functions so
1463 * this saves a 'safe' function.
1464 */
1465 image->opaque->png_ptr->io_ptr = file;
1466 return png_safe_execute(image, png_image_read_header, image);
1467 }
1468 }
1469
1470 else
1471 return png_image_error(image,
1472 "png_image_begin_read_from_stdio: invalid argument");
1473 }
1474
1475 else if (image != NULL)
1476 return png_image_error(image,
1477 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1478
1479 return 0;
1480 }
1481
1482 int PNGAPI
png_image_begin_read_from_file(png_imagep image,const char * file_name)1483 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1484 {
1485 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1486 {
1487 if (file_name != NULL)
1488 {
1489 FILE *fp = fopen(file_name, "rb");
1490
1491 if (fp != NULL)
1492 {
1493 if (png_image_read_init(image) != 0)
1494 {
1495 image->opaque->png_ptr->io_ptr = fp;
1496 image->opaque->owned_file = 1;
1497 return png_safe_execute(image, png_image_read_header, image);
1498 }
1499
1500 /* Clean up: just the opened file. */
1501 (void)fclose(fp);
1502 }
1503
1504 else
1505 return png_image_error(image, strerror(errno));
1506 }
1507
1508 else
1509 return png_image_error(image,
1510 "png_image_begin_read_from_file: invalid argument");
1511 }
1512
1513 else if (image != NULL)
1514 return png_image_error(image,
1515 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1516
1517 return 0;
1518 }
1519 #endif /* STDIO */
1520
1521 static void PNGCBAPI
png_image_memory_read(png_structp png_ptr,png_bytep out,png_size_t need)1522 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1523 {
1524 if (png_ptr != NULL)
1525 {
1526 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1527 if (image != NULL)
1528 {
1529 png_controlp cp = image->opaque;
1530 if (cp != NULL)
1531 {
1532 png_const_bytep memory = cp->memory;
1533 png_size_t size = cp->size;
1534
1535 if (memory != NULL && size >= need)
1536 {
1537 memcpy(out, memory, need);
1538 cp->memory = memory + need;
1539 cp->size = size - need;
1540 return;
1541 }
1542
1543 png_error(png_ptr, "read beyond end of data");
1544 }
1545 }
1546
1547 png_error(png_ptr, "invalid memory read");
1548 }
1549 }
1550
png_image_begin_read_from_memory(png_imagep image,png_const_voidp memory,png_size_t size)1551 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1552 png_const_voidp memory, png_size_t size)
1553 {
1554 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1555 {
1556 if (memory != NULL && size > 0)
1557 {
1558 if (png_image_read_init(image) != 0)
1559 {
1560 /* Now set the IO functions to read from the memory buffer and
1561 * store it into io_ptr. Again do this in-place to avoid calling a
1562 * libpng function that requires error handling.
1563 */
1564 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1565 image->opaque->size = size;
1566 image->opaque->png_ptr->io_ptr = image;
1567 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1568
1569 return png_safe_execute(image, png_image_read_header, image);
1570 }
1571 }
1572
1573 else
1574 return png_image_error(image,
1575 "png_image_begin_read_from_memory: invalid argument");
1576 }
1577
1578 else if (image != NULL)
1579 return png_image_error(image,
1580 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1581
1582 return 0;
1583 }
1584
1585 /* Utility function to skip chunks that are not used by the simplified image
1586 * read functions and an appropriate macro to call it.
1587 */
1588 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1589 static void
png_image_skip_unused_chunks(png_structrp png_ptr)1590 png_image_skip_unused_chunks(png_structrp png_ptr)
1591 {
1592 /* Prepare the reader to ignore all recognized chunks whose data will not
1593 * be used, i.e., all chunks recognized by libpng except for those
1594 * involved in basic image reading:
1595 *
1596 * IHDR, PLTE, IDAT, IEND
1597 *
1598 * Or image data handling:
1599 *
1600 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1601 *
1602 * This provides a small performance improvement and eliminates any
1603 * potential vulnerability to security problems in the unused chunks.
1604 *
1605 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1606 * too. This allows the simplified API to be compiled without iCCP support,
1607 * however if the support is there the chunk is still checked to detect
1608 * errors (which are unfortunately quite common.)
1609 */
1610 {
1611 static PNG_CONST png_byte chunks_to_process[] = {
1612 98, 75, 71, 68, '\0', /* bKGD */
1613 99, 72, 82, 77, '\0', /* cHRM */
1614 103, 65, 77, 65, '\0', /* gAMA */
1615 # ifdef PNG_READ_iCCP_SUPPORTED
1616 105, 67, 67, 80, '\0', /* iCCP */
1617 # endif
1618 115, 66, 73, 84, '\0', /* sBIT */
1619 115, 82, 71, 66, '\0', /* sRGB */
1620 };
1621
1622 /* Ignore unknown chunks and all other chunks except for the
1623 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1624 */
1625 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1626 NULL, -1);
1627
1628 /* But do not ignore image data handling chunks */
1629 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1630 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1631 }
1632 }
1633
1634 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1635 #else
1636 # define PNG_SKIP_CHUNKS(p) ((void)0)
1637 #endif /* HANDLE_AS_UNKNOWN */
1638
1639 /* The following macro gives the exact rounded answer for all values in the
1640 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1641 * the correct numbers 0..5
1642 */
1643 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1644
1645 /* Utility functions to make particular color-maps */
1646 static void
set_file_encoding(png_image_read_control * display)1647 set_file_encoding(png_image_read_control *display)
1648 {
1649 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1650 if (png_gamma_significant(g) != 0)
1651 {
1652 if (png_gamma_not_sRGB(g) != 0)
1653 {
1654 display->file_encoding = P_FILE;
1655 display->gamma_to_linear = png_reciprocal(g);
1656 }
1657
1658 else
1659 display->file_encoding = P_sRGB;
1660 }
1661
1662 else
1663 display->file_encoding = P_LINEAR8;
1664 }
1665
1666 static unsigned int
decode_gamma(png_image_read_control * display,png_uint_32 value,int encoding)1667 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1668 {
1669 if (encoding == P_FILE) /* double check */
1670 encoding = display->file_encoding;
1671
1672 if (encoding == P_NOTSET) /* must be the file encoding */
1673 {
1674 set_file_encoding(display);
1675 encoding = display->file_encoding;
1676 }
1677
1678 switch (encoding)
1679 {
1680 case P_FILE:
1681 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1682 break;
1683
1684 case P_sRGB:
1685 value = png_sRGB_table[value];
1686 break;
1687
1688 case P_LINEAR:
1689 break;
1690
1691 case P_LINEAR8:
1692 value *= 257;
1693 break;
1694
1695 #ifdef __GNUC__
1696 default:
1697 png_error(display->image->opaque->png_ptr,
1698 "unexpected encoding (internal error)");
1699 #endif
1700 }
1701
1702 return value;
1703 }
1704
1705 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)1706 png_colormap_compose(png_image_read_control *display,
1707 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1708 png_uint_32 background, int encoding)
1709 {
1710 /* The file value is composed on the background, the background has the given
1711 * encoding and so does the result, the file is encoded with P_FILE and the
1712 * file and alpha are 8-bit values. The (output) encoding will always be
1713 * P_LINEAR or P_sRGB.
1714 */
1715 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1716 png_uint_32 b = decode_gamma(display, background, encoding);
1717
1718 /* The alpha is always an 8-bit value (it comes from the palette), the value
1719 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1720 */
1721 f = f * alpha + b * (255-alpha);
1722
1723 if (encoding == P_LINEAR)
1724 {
1725 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1726 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1727 */
1728 f *= 257; /* Now scaled by 65535 */
1729 f += f >> 16;
1730 f = (f+32768) >> 16;
1731 }
1732
1733 else /* P_sRGB */
1734 f = PNG_sRGB_FROM_LINEAR(f);
1735
1736 return f;
1737 }
1738
1739 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1740 * be 8-bit.
1741 */
1742 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)1743 png_create_colormap_entry(png_image_read_control *display,
1744 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1745 png_uint_32 alpha, int encoding)
1746 {
1747 png_imagep image = display->image;
1748 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1749 P_LINEAR : P_sRGB;
1750 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1751 (red != green || green != blue);
1752
1753 if (ip > 255)
1754 png_error(image->opaque->png_ptr, "color-map index out of range");
1755
1756 /* Update the cache with whether the file gamma is significantly different
1757 * from sRGB.
1758 */
1759 if (encoding == P_FILE)
1760 {
1761 if (display->file_encoding == P_NOTSET)
1762 set_file_encoding(display);
1763
1764 /* Note that the cached value may be P_FILE too, but if it is then the
1765 * gamma_to_linear member has been set.
1766 */
1767 encoding = display->file_encoding;
1768 }
1769
1770 if (encoding == P_FILE)
1771 {
1772 png_fixed_point g = display->gamma_to_linear;
1773
1774 red = png_gamma_16bit_correct(red*257, g);
1775 green = png_gamma_16bit_correct(green*257, g);
1776 blue = png_gamma_16bit_correct(blue*257, g);
1777
1778 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1779 {
1780 alpha *= 257;
1781 encoding = P_LINEAR;
1782 }
1783
1784 else
1785 {
1786 red = PNG_sRGB_FROM_LINEAR(red * 255);
1787 green = PNG_sRGB_FROM_LINEAR(green * 255);
1788 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1789 encoding = P_sRGB;
1790 }
1791 }
1792
1793 else if (encoding == P_LINEAR8)
1794 {
1795 /* This encoding occurs quite frequently in test cases because PngSuite
1796 * includes a gAMA 1.0 chunk with most images.
1797 */
1798 red *= 257;
1799 green *= 257;
1800 blue *= 257;
1801 alpha *= 257;
1802 encoding = P_LINEAR;
1803 }
1804
1805 else if (encoding == P_sRGB &&
1806 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1807 {
1808 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1809 * linear.
1810 */
1811 red = png_sRGB_table[red];
1812 green = png_sRGB_table[green];
1813 blue = png_sRGB_table[blue];
1814 alpha *= 257;
1815 encoding = P_LINEAR;
1816 }
1817
1818 /* This is set if the color isn't gray but the output is. */
1819 if (encoding == P_LINEAR)
1820 {
1821 if (convert_to_Y != 0)
1822 {
1823 /* NOTE: these values are copied from png_do_rgb_to_gray */
1824 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1825 (png_uint_32)2366 * blue;
1826
1827 if (output_encoding == P_LINEAR)
1828 y = (y + 16384) >> 15;
1829
1830 else
1831 {
1832 /* y is scaled by 32768, we need it scaled by 255: */
1833 y = (y + 128) >> 8;
1834 y *= 255;
1835 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1836 alpha = PNG_DIV257(alpha);
1837 encoding = P_sRGB;
1838 }
1839
1840 blue = red = green = y;
1841 }
1842
1843 else if (output_encoding == P_sRGB)
1844 {
1845 red = PNG_sRGB_FROM_LINEAR(red * 255);
1846 green = PNG_sRGB_FROM_LINEAR(green * 255);
1847 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1848 alpha = PNG_DIV257(alpha);
1849 encoding = P_sRGB;
1850 }
1851 }
1852
1853 if (encoding != output_encoding)
1854 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1855
1856 /* Store the value. */
1857 {
1858 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1859 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1860 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1861 # else
1862 # define afirst 0
1863 # endif
1864 # ifdef PNG_FORMAT_BGR_SUPPORTED
1865 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1866 # else
1867 # define bgr 0
1868 # endif
1869
1870 if (output_encoding == P_LINEAR)
1871 {
1872 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1873
1874 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1875
1876 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1877 * value, if less than 65535 (this is, effectively, composite on black
1878 * if the alpha channel is removed.)
1879 */
1880 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1881 {
1882 case 4:
1883 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1884 /* FALL THROUGH */
1885
1886 case 3:
1887 if (alpha < 65535)
1888 {
1889 if (alpha > 0)
1890 {
1891 blue = (blue * alpha + 32767U)/65535U;
1892 green = (green * alpha + 32767U)/65535U;
1893 red = (red * alpha + 32767U)/65535U;
1894 }
1895
1896 else
1897 red = green = blue = 0;
1898 }
1899 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1900 entry[afirst + 1] = (png_uint_16)green;
1901 entry[afirst + bgr] = (png_uint_16)red;
1902 break;
1903
1904 case 2:
1905 entry[1 ^ afirst] = (png_uint_16)alpha;
1906 /* FALL THROUGH */
1907
1908 case 1:
1909 if (alpha < 65535)
1910 {
1911 if (alpha > 0)
1912 green = (green * alpha + 32767U)/65535U;
1913
1914 else
1915 green = 0;
1916 }
1917 entry[afirst] = (png_uint_16)green;
1918 break;
1919
1920 default:
1921 break;
1922 }
1923 }
1924
1925 else /* output encoding is P_sRGB */
1926 {
1927 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1928
1929 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1930
1931 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1932 {
1933 case 4:
1934 entry[afirst ? 0 : 3] = (png_byte)alpha;
1935 case 3:
1936 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1937 entry[afirst + 1] = (png_byte)green;
1938 entry[afirst + bgr] = (png_byte)red;
1939 break;
1940
1941 case 2:
1942 entry[1 ^ afirst] = (png_byte)alpha;
1943 case 1:
1944 entry[afirst] = (png_byte)green;
1945 break;
1946
1947 default:
1948 break;
1949 }
1950 }
1951
1952 # ifdef afirst
1953 # undef afirst
1954 # endif
1955 # ifdef bgr
1956 # undef bgr
1957 # endif
1958 }
1959 }
1960
1961 static int
make_gray_file_colormap(png_image_read_control * display)1962 make_gray_file_colormap(png_image_read_control *display)
1963 {
1964 unsigned int i;
1965
1966 for (i=0; i<256; ++i)
1967 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1968
1969 return i;
1970 }
1971
1972 static int
make_gray_colormap(png_image_read_control * display)1973 make_gray_colormap(png_image_read_control *display)
1974 {
1975 unsigned int i;
1976
1977 for (i=0; i<256; ++i)
1978 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
1979
1980 return i;
1981 }
1982 #define PNG_GRAY_COLORMAP_ENTRIES 256
1983
1984 static int
make_ga_colormap(png_image_read_control * display)1985 make_ga_colormap(png_image_read_control *display)
1986 {
1987 unsigned int i, a;
1988
1989 /* Alpha is retained, the output will be a color-map with entries
1990 * selected by six levels of alpha. One transparent entry, 6 gray
1991 * levels for all the intermediate alpha values, leaving 230 entries
1992 * for the opaque grays. The color-map entries are the six values
1993 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
1994 * relevant entry.
1995 *
1996 * if (alpha > 229) // opaque
1997 * {
1998 * // The 231 entries are selected to make the math below work:
1999 * base = 0;
2000 * entry = (231 * gray + 128) >> 8;
2001 * }
2002 * else if (alpha < 26) // transparent
2003 * {
2004 * base = 231;
2005 * entry = 0;
2006 * }
2007 * else // partially opaque
2008 * {
2009 * base = 226 + 6 * PNG_DIV51(alpha);
2010 * entry = PNG_DIV51(gray);
2011 * }
2012 */
2013 i = 0;
2014 while (i < 231)
2015 {
2016 unsigned int gray = (i * 256 + 115) / 231;
2017 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2018 }
2019
2020 /* 255 is used here for the component values for consistency with the code
2021 * that undoes premultiplication in pngwrite.c.
2022 */
2023 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2024
2025 for (a=1; a<5; ++a)
2026 {
2027 unsigned int g;
2028
2029 for (g=0; g<6; ++g)
2030 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2031 P_sRGB);
2032 }
2033
2034 return i;
2035 }
2036
2037 #define PNG_GA_COLORMAP_ENTRIES 256
2038
2039 static int
make_rgb_colormap(png_image_read_control * display)2040 make_rgb_colormap(png_image_read_control *display)
2041 {
2042 unsigned int i, r;
2043
2044 /* Build a 6x6x6 opaque RGB cube */
2045 for (i=r=0; r<6; ++r)
2046 {
2047 unsigned int g;
2048
2049 for (g=0; g<6; ++g)
2050 {
2051 unsigned int b;
2052
2053 for (b=0; b<6; ++b)
2054 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2055 P_sRGB);
2056 }
2057 }
2058
2059 return i;
2060 }
2061
2062 #define PNG_RGB_COLORMAP_ENTRIES 216
2063
2064 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2065 #define PNG_RGB_INDEX(r,g,b) \
2066 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2067
2068 static int
png_image_read_colormap(png_voidp argument)2069 png_image_read_colormap(png_voidp argument)
2070 {
2071 png_image_read_control *display =
2072 png_voidcast(png_image_read_control*, argument);
2073 const png_imagep image = display->image;
2074
2075 const png_structrp png_ptr = image->opaque->png_ptr;
2076 const png_uint_32 output_format = image->format;
2077 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2078 P_LINEAR : P_sRGB;
2079
2080 unsigned int cmap_entries;
2081 unsigned int output_processing; /* Output processing option */
2082 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2083
2084 /* Background information; the background color and the index of this color
2085 * in the color-map if it exists (else 256).
2086 */
2087 unsigned int background_index = 256;
2088 png_uint_32 back_r, back_g, back_b;
2089
2090 /* Flags to accumulate things that need to be done to the input. */
2091 int expand_tRNS = 0;
2092
2093 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2094 * very difficult to do, the results look awful, and it is difficult to see
2095 * what possible use it is because the application can't control the
2096 * color-map.
2097 */
2098 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2099 png_ptr->num_trans > 0) /* alpha in input */ &&
2100 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2101 {
2102 if (output_encoding == P_LINEAR) /* compose on black */
2103 back_b = back_g = back_r = 0;
2104
2105 else if (display->background == NULL /* no way to remove it */)
2106 png_error(png_ptr,
2107 "background color must be supplied to remove alpha/transparency");
2108
2109 /* Get a copy of the background color (this avoids repeating the checks
2110 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2111 * output format.
2112 */
2113 else
2114 {
2115 back_g = display->background->green;
2116 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2117 {
2118 back_r = display->background->red;
2119 back_b = display->background->blue;
2120 }
2121 else
2122 back_b = back_r = back_g;
2123 }
2124 }
2125
2126 else if (output_encoding == P_LINEAR)
2127 back_b = back_r = back_g = 65535;
2128
2129 else
2130 back_b = back_r = back_g = 255;
2131
2132 /* Default the input file gamma if required - this is necessary because
2133 * libpng assumes that if no gamma information is present the data is in the
2134 * output format, but the simplified API deduces the gamma from the input
2135 * format.
2136 */
2137 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2138 {
2139 /* Do this directly, not using the png_colorspace functions, to ensure
2140 * that it happens even if the colorspace is invalid (though probably if
2141 * it is the setting will be ignored) Note that the same thing can be
2142 * achieved at the application interface with png_set_gAMA.
2143 */
2144 if (png_ptr->bit_depth == 16 &&
2145 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2146 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2147
2148 else
2149 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2150
2151 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2152 }
2153
2154 /* Decide what to do based on the PNG color type of the input data. The
2155 * utility function png_create_colormap_entry deals with most aspects of the
2156 * output transformations; this code works out how to produce bytes of
2157 * color-map entries from the original format.
2158 */
2159 switch (png_ptr->color_type)
2160 {
2161 case PNG_COLOR_TYPE_GRAY:
2162 if (png_ptr->bit_depth <= 8)
2163 {
2164 /* There at most 256 colors in the output, regardless of
2165 * transparency.
2166 */
2167 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2168
2169 cmap_entries = 1U << png_ptr->bit_depth;
2170 if (cmap_entries > image->colormap_entries)
2171 png_error(png_ptr, "gray[8] color-map: too few entries");
2172
2173 step = 255 / (cmap_entries - 1);
2174 output_processing = PNG_CMAP_NONE;
2175
2176 /* If there is a tRNS chunk then this either selects a transparent
2177 * value or, if the output has no alpha, the background color.
2178 */
2179 if (png_ptr->num_trans > 0)
2180 {
2181 trans = png_ptr->trans_color.gray;
2182
2183 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2184 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2185 }
2186
2187 /* png_create_colormap_entry just takes an RGBA and writes the
2188 * corresponding color-map entry using the format from 'image',
2189 * including the required conversion to sRGB or linear as
2190 * appropriate. The input values are always either sRGB (if the
2191 * gamma correction flag is 0) or 0..255 scaled file encoded values
2192 * (if the function must gamma correct them).
2193 */
2194 for (i=val=0; i<cmap_entries; ++i, val += step)
2195 {
2196 /* 'i' is a file value. While this will result in duplicated
2197 * entries for 8-bit non-sRGB encoded files it is necessary to
2198 * have non-gamma corrected values to do tRNS handling.
2199 */
2200 if (i != trans)
2201 png_create_colormap_entry(display, i, val, val, val, 255,
2202 P_FILE/*8-bit with file gamma*/);
2203
2204 /* Else this entry is transparent. The colors don't matter if
2205 * there is an alpha channel (back_alpha == 0), but it does no
2206 * harm to pass them in; the values are not set above so this
2207 * passes in white.
2208 *
2209 * NOTE: this preserves the full precision of the application
2210 * supplied background color when it is used.
2211 */
2212 else
2213 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2214 back_alpha, output_encoding);
2215 }
2216
2217 /* We need libpng to preserve the original encoding. */
2218 data_encoding = P_FILE;
2219
2220 /* The rows from libpng, while technically gray values, are now also
2221 * color-map indices; however, they may need to be expanded to 1
2222 * byte per pixel. This is what png_set_packing does (i.e., it
2223 * unpacks the bit values into bytes.)
2224 */
2225 if (png_ptr->bit_depth < 8)
2226 png_set_packing(png_ptr);
2227 }
2228
2229 else /* bit depth is 16 */
2230 {
2231 /* The 16-bit input values can be converted directly to 8-bit gamma
2232 * encoded values; however, if a tRNS chunk is present 257 color-map
2233 * entries are required. This means that the extra entry requires
2234 * special processing; add an alpha channel, sacrifice gray level
2235 * 254 and convert transparent (alpha==0) entries to that.
2236 *
2237 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2238 * same time to minimize quality loss. If a tRNS chunk is present
2239 * this means libpng must handle it too; otherwise it is impossible
2240 * to do the exact match on the 16-bit value.
2241 *
2242 * If the output has no alpha channel *and* the background color is
2243 * gray then it is possible to let libpng handle the substitution by
2244 * ensuring that the corresponding gray level matches the background
2245 * color exactly.
2246 */
2247 data_encoding = P_sRGB;
2248
2249 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2250 png_error(png_ptr, "gray[16] color-map: too few entries");
2251
2252 cmap_entries = make_gray_colormap(display);
2253
2254 if (png_ptr->num_trans > 0)
2255 {
2256 unsigned int back_alpha;
2257
2258 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2259 back_alpha = 0;
2260
2261 else
2262 {
2263 if (back_r == back_g && back_g == back_b)
2264 {
2265 /* Background is gray; no special processing will be
2266 * required.
2267 */
2268 png_color_16 c;
2269 png_uint_32 gray = back_g;
2270
2271 if (output_encoding == P_LINEAR)
2272 {
2273 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2274
2275 /* And make sure the corresponding palette entry
2276 * matches.
2277 */
2278 png_create_colormap_entry(display, gray, back_g, back_g,
2279 back_g, 65535, P_LINEAR);
2280 }
2281
2282 /* The background passed to libpng, however, must be the
2283 * sRGB value.
2284 */
2285 c.index = 0; /*unused*/
2286 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2287
2288 /* NOTE: does this work without expanding tRNS to alpha?
2289 * It should be the color->gray case below apparently
2290 * doesn't.
2291 */
2292 png_set_background_fixed(png_ptr, &c,
2293 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2294 0/*gamma: not used*/);
2295
2296 output_processing = PNG_CMAP_NONE;
2297 break;
2298 }
2299 #ifdef __COVERITY__
2300 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2301 * here.
2302 */
2303 back_alpha = 255;
2304 #else
2305 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2306 #endif
2307 }
2308
2309 /* output_processing means that the libpng-processed row will be
2310 * 8-bit GA and it has to be processing to single byte color-map
2311 * values. Entry 254 is replaced by either a completely
2312 * transparent entry or by the background color at full
2313 * precision (and the background color is not a simple gray
2314 * level in this case.)
2315 */
2316 expand_tRNS = 1;
2317 output_processing = PNG_CMAP_TRANS;
2318 background_index = 254;
2319
2320 /* And set (overwrite) color-map entry 254 to the actual
2321 * background color at full precision.
2322 */
2323 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2324 back_alpha, output_encoding);
2325 }
2326
2327 else
2328 output_processing = PNG_CMAP_NONE;
2329 }
2330 break;
2331
2332 case PNG_COLOR_TYPE_GRAY_ALPHA:
2333 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2334 * of 65536 combinations. If, however, the alpha channel is to be
2335 * removed there are only 256 possibilities if the background is gray.
2336 * (Otherwise there is a subset of the 65536 possibilities defined by
2337 * the triangle between black, white and the background color.)
2338 *
2339 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2340 * worry about tRNS matching - tRNS is ignored if there is an alpha
2341 * channel.
2342 */
2343 data_encoding = P_sRGB;
2344
2345 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2346 {
2347 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2348 png_error(png_ptr, "gray+alpha color-map: too few entries");
2349
2350 cmap_entries = make_ga_colormap(display);
2351
2352 background_index = PNG_CMAP_GA_BACKGROUND;
2353 output_processing = PNG_CMAP_GA;
2354 }
2355
2356 else /* alpha is removed */
2357 {
2358 /* Alpha must be removed as the PNG data is processed when the
2359 * background is a color because the G and A channels are
2360 * independent and the vector addition (non-parallel vectors) is a
2361 * 2-D problem.
2362 *
2363 * This can be reduced to the same algorithm as above by making a
2364 * colormap containing gray levels (for the opaque grays), a
2365 * background entry (for a transparent pixel) and a set of four six
2366 * level color values, one set for each intermediate alpha value.
2367 * See the comments in make_ga_colormap for how this works in the
2368 * per-pixel processing.
2369 *
2370 * If the background is gray, however, we only need a 256 entry gray
2371 * level color map. It is sufficient to make the entry generated
2372 * for the background color be exactly the color specified.
2373 */
2374 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2375 (back_r == back_g && back_g == back_b))
2376 {
2377 /* Background is gray; no special processing will be required. */
2378 png_color_16 c;
2379 png_uint_32 gray = back_g;
2380
2381 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2382 png_error(png_ptr, "gray-alpha color-map: too few entries");
2383
2384 cmap_entries = make_gray_colormap(display);
2385
2386 if (output_encoding == P_LINEAR)
2387 {
2388 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2389
2390 /* And make sure the corresponding palette entry matches. */
2391 png_create_colormap_entry(display, gray, back_g, back_g,
2392 back_g, 65535, P_LINEAR);
2393 }
2394
2395 /* The background passed to libpng, however, must be the sRGB
2396 * value.
2397 */
2398 c.index = 0; /*unused*/
2399 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2400
2401 png_set_background_fixed(png_ptr, &c,
2402 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2403 0/*gamma: not used*/);
2404
2405 output_processing = PNG_CMAP_NONE;
2406 }
2407
2408 else
2409 {
2410 png_uint_32 i, a;
2411
2412 /* This is the same as png_make_ga_colormap, above, except that
2413 * the entries are all opaque.
2414 */
2415 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2416 png_error(png_ptr, "ga-alpha color-map: too few entries");
2417
2418 i = 0;
2419 while (i < 231)
2420 {
2421 png_uint_32 gray = (i * 256 + 115) / 231;
2422 png_create_colormap_entry(display, i++, gray, gray, gray,
2423 255, P_sRGB);
2424 }
2425
2426 /* NOTE: this preserves the full precision of the application
2427 * background color.
2428 */
2429 background_index = i;
2430 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2431 #ifdef __COVERITY__
2432 /* Coverity claims that output_encoding
2433 * cannot be 2 (P_LINEAR) here.
2434 */ 255U,
2435 #else
2436 output_encoding == P_LINEAR ? 65535U : 255U,
2437 #endif
2438 output_encoding);
2439
2440 /* For non-opaque input composite on the sRGB background - this
2441 * requires inverting the encoding for each component. The input
2442 * is still converted to the sRGB encoding because this is a
2443 * reasonable approximate to the logarithmic curve of human
2444 * visual sensitivity, at least over the narrow range which PNG
2445 * represents. Consequently 'G' is always sRGB encoded, while
2446 * 'A' is linear. We need the linear background colors.
2447 */
2448 if (output_encoding == P_sRGB) /* else already linear */
2449 {
2450 /* This may produce a value not exactly matching the
2451 * background, but that's ok because these numbers are only
2452 * used when alpha != 0
2453 */
2454 back_r = png_sRGB_table[back_r];
2455 back_g = png_sRGB_table[back_g];
2456 back_b = png_sRGB_table[back_b];
2457 }
2458
2459 for (a=1; a<5; ++a)
2460 {
2461 unsigned int g;
2462
2463 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2464 * by an 8-bit alpha value (0..255).
2465 */
2466 png_uint_32 alpha = 51 * a;
2467 png_uint_32 back_rx = (255-alpha) * back_r;
2468 png_uint_32 back_gx = (255-alpha) * back_g;
2469 png_uint_32 back_bx = (255-alpha) * back_b;
2470
2471 for (g=0; g<6; ++g)
2472 {
2473 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2474
2475 png_create_colormap_entry(display, i++,
2476 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2477 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2478 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2479 }
2480 }
2481
2482 cmap_entries = i;
2483 output_processing = PNG_CMAP_GA;
2484 }
2485 }
2486 break;
2487
2488 case PNG_COLOR_TYPE_RGB:
2489 case PNG_COLOR_TYPE_RGB_ALPHA:
2490 /* Exclude the case where the output is gray; we can always handle this
2491 * with the cases above.
2492 */
2493 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2494 {
2495 /* The color-map will be grayscale, so we may as well convert the
2496 * input RGB values to a simple grayscale and use the grayscale
2497 * code above.
2498 *
2499 * NOTE: calling this apparently damages the recognition of the
2500 * transparent color in background color handling; call
2501 * png_set_tRNS_to_alpha before png_set_background_fixed.
2502 */
2503 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2504 -1);
2505 data_encoding = P_sRGB;
2506
2507 /* The output will now be one or two 8-bit gray or gray+alpha
2508 * channels. The more complex case arises when the input has alpha.
2509 */
2510 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2511 png_ptr->num_trans > 0) &&
2512 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2513 {
2514 /* Both input and output have an alpha channel, so no background
2515 * processing is required; just map the GA bytes to the right
2516 * color-map entry.
2517 */
2518 expand_tRNS = 1;
2519
2520 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2521 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2522
2523 cmap_entries = make_ga_colormap(display);
2524 background_index = PNG_CMAP_GA_BACKGROUND;
2525 output_processing = PNG_CMAP_GA;
2526 }
2527
2528 else
2529 {
2530 /* Either the input or the output has no alpha channel, so there
2531 * will be no non-opaque pixels in the color-map; it will just be
2532 * grayscale.
2533 */
2534 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2535 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2536
2537 /* Ideally this code would use libpng to do the gamma correction,
2538 * but if an input alpha channel is to be removed we will hit the
2539 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2540 * correction bug). Fix this by dropping the gamma correction in
2541 * this case and doing it in the palette; this will result in
2542 * duplicate palette entries, but that's better than the
2543 * alternative of double gamma correction.
2544 */
2545 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2546 png_ptr->num_trans > 0) &&
2547 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2548 {
2549 cmap_entries = make_gray_file_colormap(display);
2550 data_encoding = P_FILE;
2551 }
2552
2553 else
2554 cmap_entries = make_gray_colormap(display);
2555
2556 /* But if the input has alpha or transparency it must be removed
2557 */
2558 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2559 png_ptr->num_trans > 0)
2560 {
2561 png_color_16 c;
2562 png_uint_32 gray = back_g;
2563
2564 /* We need to ensure that the application background exists in
2565 * the colormap and that completely transparent pixels map to
2566 * it. Achieve this simply by ensuring that the entry
2567 * selected for the background really is the background color.
2568 */
2569 if (data_encoding == P_FILE) /* from the fixup above */
2570 {
2571 /* The app supplied a gray which is in output_encoding, we
2572 * need to convert it to a value of the input (P_FILE)
2573 * encoding then set this palette entry to the required
2574 * output encoding.
2575 */
2576 if (output_encoding == P_sRGB)
2577 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2578
2579 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2580 png_ptr->colorspace.gamma)); /* now P_FILE */
2581
2582 /* And make sure the corresponding palette entry contains
2583 * exactly the required sRGB value.
2584 */
2585 png_create_colormap_entry(display, gray, back_g, back_g,
2586 back_g, 0/*unused*/, output_encoding);
2587 }
2588
2589 else if (output_encoding == P_LINEAR)
2590 {
2591 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2592
2593 /* And make sure the corresponding palette entry matches.
2594 */
2595 png_create_colormap_entry(display, gray, back_g, back_g,
2596 back_g, 0/*unused*/, P_LINEAR);
2597 }
2598
2599 /* The background passed to libpng, however, must be the
2600 * output (normally sRGB) value.
2601 */
2602 c.index = 0; /*unused*/
2603 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2604
2605 /* NOTE: the following is apparently a bug in libpng. Without
2606 * it the transparent color recognition in
2607 * png_set_background_fixed seems to go wrong.
2608 */
2609 expand_tRNS = 1;
2610 png_set_background_fixed(png_ptr, &c,
2611 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2612 0/*gamma: not used*/);
2613 }
2614
2615 output_processing = PNG_CMAP_NONE;
2616 }
2617 }
2618
2619 else /* output is color */
2620 {
2621 /* We could use png_quantize here so long as there is no transparent
2622 * color or alpha; png_quantize ignores alpha. Easier overall just
2623 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2624 * Consequently we always want libpng to produce sRGB data.
2625 */
2626 data_encoding = P_sRGB;
2627
2628 /* Is there any transparency or alpha? */
2629 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2630 png_ptr->num_trans > 0)
2631 {
2632 /* Is there alpha in the output too? If so all four channels are
2633 * processed into a special RGB cube with alpha support.
2634 */
2635 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2636 {
2637 png_uint_32 r;
2638
2639 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2640 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2641
2642 cmap_entries = make_rgb_colormap(display);
2643
2644 /* Add a transparent entry. */
2645 png_create_colormap_entry(display, cmap_entries, 255, 255,
2646 255, 0, P_sRGB);
2647
2648 /* This is stored as the background index for the processing
2649 * algorithm.
2650 */
2651 background_index = cmap_entries++;
2652
2653 /* Add 27 r,g,b entries each with alpha 0.5. */
2654 for (r=0; r<256; r = (r << 1) | 0x7f)
2655 {
2656 png_uint_32 g;
2657
2658 for (g=0; g<256; g = (g << 1) | 0x7f)
2659 {
2660 png_uint_32 b;
2661
2662 /* This generates components with the values 0, 127 and
2663 * 255
2664 */
2665 for (b=0; b<256; b = (b << 1) | 0x7f)
2666 png_create_colormap_entry(display, cmap_entries++,
2667 r, g, b, 128, P_sRGB);
2668 }
2669 }
2670
2671 expand_tRNS = 1;
2672 output_processing = PNG_CMAP_RGB_ALPHA;
2673 }
2674
2675 else
2676 {
2677 /* Alpha/transparency must be removed. The background must
2678 * exist in the color map (achieved by setting adding it after
2679 * the 666 color-map). If the standard processing code will
2680 * pick up this entry automatically that's all that is
2681 * required; libpng can be called to do the background
2682 * processing.
2683 */
2684 unsigned int sample_size =
2685 PNG_IMAGE_SAMPLE_SIZE(output_format);
2686 png_uint_32 r, g, b; /* sRGB background */
2687
2688 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2689 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2690
2691 cmap_entries = make_rgb_colormap(display);
2692
2693 png_create_colormap_entry(display, cmap_entries, back_r,
2694 back_g, back_b, 0/*unused*/, output_encoding);
2695
2696 if (output_encoding == P_LINEAR)
2697 {
2698 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2699 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2700 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2701 }
2702
2703 else
2704 {
2705 r = back_r;
2706 g = back_g;
2707 b = back_g;
2708 }
2709
2710 /* Compare the newly-created color-map entry with the one the
2711 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2712 * match, add the new one and set this as the background
2713 * index.
2714 */
2715 if (memcmp((png_const_bytep)display->colormap +
2716 sample_size * cmap_entries,
2717 (png_const_bytep)display->colormap +
2718 sample_size * PNG_RGB_INDEX(r,g,b),
2719 sample_size) != 0)
2720 {
2721 /* The background color must be added. */
2722 background_index = cmap_entries++;
2723
2724 /* Add 27 r,g,b entries each with created by composing with
2725 * the background at alpha 0.5.
2726 */
2727 for (r=0; r<256; r = (r << 1) | 0x7f)
2728 {
2729 for (g=0; g<256; g = (g << 1) | 0x7f)
2730 {
2731 /* This generates components with the values 0, 127
2732 * and 255
2733 */
2734 for (b=0; b<256; b = (b << 1) | 0x7f)
2735 png_create_colormap_entry(display, cmap_entries++,
2736 png_colormap_compose(display, r, P_sRGB, 128,
2737 back_r, output_encoding),
2738 png_colormap_compose(display, g, P_sRGB, 128,
2739 back_g, output_encoding),
2740 png_colormap_compose(display, b, P_sRGB, 128,
2741 back_b, output_encoding),
2742 0/*unused*/, output_encoding);
2743 }
2744 }
2745
2746 expand_tRNS = 1;
2747 output_processing = PNG_CMAP_RGB_ALPHA;
2748 }
2749
2750 else /* background color is in the standard color-map */
2751 {
2752 png_color_16 c;
2753
2754 c.index = 0; /*unused*/
2755 c.red = (png_uint_16)back_r;
2756 c.gray = c.green = (png_uint_16)back_g;
2757 c.blue = (png_uint_16)back_b;
2758
2759 png_set_background_fixed(png_ptr, &c,
2760 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2761 0/*gamma: not used*/);
2762
2763 output_processing = PNG_CMAP_RGB;
2764 }
2765 }
2766 }
2767
2768 else /* no alpha or transparency in the input */
2769 {
2770 /* Alpha in the output is irrelevant, simply map the opaque input
2771 * pixels to the 6x6x6 color-map.
2772 */
2773 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2774 png_error(png_ptr, "rgb color-map: too few entries");
2775
2776 cmap_entries = make_rgb_colormap(display);
2777 output_processing = PNG_CMAP_RGB;
2778 }
2779 }
2780 break;
2781
2782 case PNG_COLOR_TYPE_PALETTE:
2783 /* It's already got a color-map. It may be necessary to eliminate the
2784 * tRNS entries though.
2785 */
2786 {
2787 unsigned int num_trans = png_ptr->num_trans;
2788 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2789 png_const_colorp colormap = png_ptr->palette;
2790 const int do_background = trans != NULL &&
2791 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2792 unsigned int i;
2793
2794 /* Just in case: */
2795 if (trans == NULL)
2796 num_trans = 0;
2797
2798 output_processing = PNG_CMAP_NONE;
2799 data_encoding = P_FILE; /* Don't change from color-map indices */
2800 cmap_entries = png_ptr->num_palette;
2801 if (cmap_entries > 256)
2802 cmap_entries = 256;
2803
2804 if (cmap_entries > image->colormap_entries)
2805 png_error(png_ptr, "palette color-map: too few entries");
2806
2807 for (i=0; i < cmap_entries; ++i)
2808 {
2809 if (do_background != 0 && i < num_trans && trans[i] < 255)
2810 {
2811 if (trans[i] == 0)
2812 png_create_colormap_entry(display, i, back_r, back_g,
2813 back_b, 0, output_encoding);
2814
2815 else
2816 {
2817 /* Must compose the PNG file color in the color-map entry
2818 * on the sRGB color in 'back'.
2819 */
2820 png_create_colormap_entry(display, i,
2821 png_colormap_compose(display, colormap[i].red,
2822 P_FILE, trans[i], back_r, output_encoding),
2823 png_colormap_compose(display, colormap[i].green,
2824 P_FILE, trans[i], back_g, output_encoding),
2825 png_colormap_compose(display, colormap[i].blue,
2826 P_FILE, trans[i], back_b, output_encoding),
2827 output_encoding == P_LINEAR ? trans[i] * 257U :
2828 trans[i],
2829 output_encoding);
2830 }
2831 }
2832
2833 else
2834 png_create_colormap_entry(display, i, colormap[i].red,
2835 colormap[i].green, colormap[i].blue,
2836 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2837 }
2838
2839 /* The PNG data may have indices packed in fewer than 8 bits, it
2840 * must be expanded if so.
2841 */
2842 if (png_ptr->bit_depth < 8)
2843 png_set_packing(png_ptr);
2844 }
2845 break;
2846
2847 default:
2848 png_error(png_ptr, "invalid PNG color type");
2849 /*NOT REACHED*/
2850 }
2851
2852 /* Now deal with the output processing */
2853 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2854 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2855 png_set_tRNS_to_alpha(png_ptr);
2856
2857 switch (data_encoding)
2858 {
2859 case P_sRGB:
2860 /* Change to 8-bit sRGB */
2861 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2862 /* FALL THROUGH */
2863
2864 case P_FILE:
2865 if (png_ptr->bit_depth > 8)
2866 png_set_scale_16(png_ptr);
2867 break;
2868
2869 #ifdef __GNUC__
2870 default:
2871 png_error(png_ptr, "bad data option (internal error)");
2872 #endif
2873 }
2874
2875 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2876 png_error(png_ptr, "color map overflow (BAD internal error)");
2877
2878 image->colormap_entries = cmap_entries;
2879
2880 /* Double check using the recorded background index */
2881 switch (output_processing)
2882 {
2883 case PNG_CMAP_NONE:
2884 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2885 goto bad_background;
2886 break;
2887
2888 case PNG_CMAP_GA:
2889 if (background_index != PNG_CMAP_GA_BACKGROUND)
2890 goto bad_background;
2891 break;
2892
2893 case PNG_CMAP_TRANS:
2894 if (background_index >= cmap_entries ||
2895 background_index != PNG_CMAP_TRANS_BACKGROUND)
2896 goto bad_background;
2897 break;
2898
2899 case PNG_CMAP_RGB:
2900 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2901 goto bad_background;
2902 break;
2903
2904 case PNG_CMAP_RGB_ALPHA:
2905 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2906 goto bad_background;
2907 break;
2908
2909 default:
2910 png_error(png_ptr, "bad processing option (internal error)");
2911
2912 bad_background:
2913 png_error(png_ptr, "bad background index (internal error)");
2914 }
2915
2916 display->colormap_processing = output_processing;
2917
2918 return 1/*ok*/;
2919 }
2920
2921 /* The final part of the color-map read called from png_image_finish_read. */
2922 static int
png_image_read_and_map(png_voidp argument)2923 png_image_read_and_map(png_voidp argument)
2924 {
2925 png_image_read_control *display = png_voidcast(png_image_read_control*,
2926 argument);
2927 png_imagep image = display->image;
2928 png_structrp png_ptr = image->opaque->png_ptr;
2929 int passes;
2930
2931 /* Called when the libpng data must be transformed into the color-mapped
2932 * form. There is a local row buffer in display->local and this routine must
2933 * do the interlace handling.
2934 */
2935 switch (png_ptr->interlaced)
2936 {
2937 case PNG_INTERLACE_NONE:
2938 passes = 1;
2939 break;
2940
2941 case PNG_INTERLACE_ADAM7:
2942 passes = PNG_INTERLACE_ADAM7_PASSES;
2943 break;
2944
2945 default:
2946 png_error(png_ptr, "unknown interlace type");
2947 }
2948
2949 {
2950 png_uint_32 height = image->height;
2951 png_uint_32 width = image->width;
2952 int proc = display->colormap_processing;
2953 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2954 ptrdiff_t step_row = display->row_bytes;
2955 int pass;
2956
2957 for (pass = 0; pass < passes; ++pass)
2958 {
2959 unsigned int startx, stepx, stepy;
2960 png_uint_32 y;
2961
2962 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2963 {
2964 /* The row may be empty for a short image: */
2965 if (PNG_PASS_COLS(width, pass) == 0)
2966 continue;
2967
2968 startx = PNG_PASS_START_COL(pass);
2969 stepx = PNG_PASS_COL_OFFSET(pass);
2970 y = PNG_PASS_START_ROW(pass);
2971 stepy = PNG_PASS_ROW_OFFSET(pass);
2972 }
2973
2974 else
2975 {
2976 y = 0;
2977 startx = 0;
2978 stepx = stepy = 1;
2979 }
2980
2981 for (; y<height; y += stepy)
2982 {
2983 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
2984 png_bytep outrow = first_row + y * step_row;
2985 png_const_bytep end_row = outrow + width;
2986
2987 /* Read read the libpng data into the temporary buffer. */
2988 png_read_row(png_ptr, inrow, NULL);
2989
2990 /* Now process the row according to the processing option, note
2991 * that the caller verifies that the format of the libpng output
2992 * data is as required.
2993 */
2994 outrow += startx;
2995 switch (proc)
2996 {
2997 case PNG_CMAP_GA:
2998 for (; outrow < end_row; outrow += stepx)
2999 {
3000 /* The data is always in the PNG order */
3001 unsigned int gray = *inrow++;
3002 unsigned int alpha = *inrow++;
3003 unsigned int entry;
3004
3005 /* NOTE: this code is copied as a comment in
3006 * make_ga_colormap above. Please update the
3007 * comment if you change this code!
3008 */
3009 if (alpha > 229) /* opaque */
3010 {
3011 entry = (231 * gray + 128) >> 8;
3012 }
3013 else if (alpha < 26) /* transparent */
3014 {
3015 entry = 231;
3016 }
3017 else /* partially opaque */
3018 {
3019 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3020 }
3021
3022 *outrow = (png_byte)entry;
3023 }
3024 break;
3025
3026 case PNG_CMAP_TRANS:
3027 for (; outrow < end_row; outrow += stepx)
3028 {
3029 png_byte gray = *inrow++;
3030 png_byte alpha = *inrow++;
3031
3032 if (alpha == 0)
3033 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3034
3035 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3036 *outrow = gray;
3037
3038 else
3039 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3040 }
3041 break;
3042
3043 case PNG_CMAP_RGB:
3044 for (; outrow < end_row; outrow += stepx)
3045 {
3046 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3047 inrow += 3;
3048 }
3049 break;
3050
3051 case PNG_CMAP_RGB_ALPHA:
3052 for (; outrow < end_row; outrow += stepx)
3053 {
3054 unsigned int alpha = inrow[3];
3055
3056 /* Because the alpha entries only hold alpha==0.5 values
3057 * split the processing at alpha==0.25 (64) and 0.75
3058 * (196).
3059 */
3060
3061 if (alpha >= 196)
3062 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3063 inrow[2]);
3064
3065 else if (alpha < 64)
3066 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3067
3068 else
3069 {
3070 /* Likewise there are three entries for each of r, g
3071 * and b. We could select the entry by popcount on
3072 * the top two bits on those architectures that
3073 * support it, this is what the code below does,
3074 * crudely.
3075 */
3076 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3077
3078 /* Here are how the values map:
3079 *
3080 * 0x00 .. 0x3f -> 0
3081 * 0x40 .. 0xbf -> 1
3082 * 0xc0 .. 0xff -> 2
3083 *
3084 * So, as above with the explicit alpha checks, the
3085 * breakpoints are at 64 and 196.
3086 */
3087 if (inrow[0] & 0x80) back_i += 9; /* red */
3088 if (inrow[0] & 0x40) back_i += 9;
3089 if (inrow[0] & 0x80) back_i += 3; /* green */
3090 if (inrow[0] & 0x40) back_i += 3;
3091 if (inrow[0] & 0x80) back_i += 1; /* blue */
3092 if (inrow[0] & 0x40) back_i += 1;
3093
3094 *outrow = (png_byte)back_i;
3095 }
3096
3097 inrow += 4;
3098 }
3099 break;
3100
3101 default:
3102 break;
3103 }
3104 }
3105 }
3106 }
3107
3108 return 1;
3109 }
3110
3111 static int
png_image_read_colormapped(png_voidp argument)3112 png_image_read_colormapped(png_voidp argument)
3113 {
3114 png_image_read_control *display = png_voidcast(png_image_read_control*,
3115 argument);
3116 png_imagep image = display->image;
3117 png_controlp control = image->opaque;
3118 png_structrp png_ptr = control->png_ptr;
3119 png_inforp info_ptr = control->info_ptr;
3120
3121 int passes = 0; /* As a flag */
3122
3123 PNG_SKIP_CHUNKS(png_ptr);
3124
3125 /* Update the 'info' structure and make sure the result is as required; first
3126 * make sure to turn on the interlace handling if it will be required
3127 * (because it can't be turned on *after* the call to png_read_update_info!)
3128 */
3129 if (display->colormap_processing == PNG_CMAP_NONE)
3130 passes = png_set_interlace_handling(png_ptr);
3131
3132 png_read_update_info(png_ptr, info_ptr);
3133
3134 /* The expected output can be deduced from the colormap_processing option. */
3135 switch (display->colormap_processing)
3136 {
3137 case PNG_CMAP_NONE:
3138 /* Output must be one channel and one byte per pixel, the output
3139 * encoding can be anything.
3140 */
3141 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3142 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3143 info_ptr->bit_depth == 8)
3144 break;
3145
3146 goto bad_output;
3147
3148 case PNG_CMAP_TRANS:
3149 case PNG_CMAP_GA:
3150 /* Output must be two channels and the 'G' one must be sRGB, the latter
3151 * can be checked with an exact number because it should have been set
3152 * to this number above!
3153 */
3154 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3155 info_ptr->bit_depth == 8 &&
3156 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3157 image->colormap_entries == 256)
3158 break;
3159
3160 goto bad_output;
3161
3162 case PNG_CMAP_RGB:
3163 /* Output must be 8-bit sRGB encoded RGB */
3164 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3165 info_ptr->bit_depth == 8 &&
3166 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3167 image->colormap_entries == 216)
3168 break;
3169
3170 goto bad_output;
3171
3172 case PNG_CMAP_RGB_ALPHA:
3173 /* Output must be 8-bit sRGB encoded RGBA */
3174 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3175 info_ptr->bit_depth == 8 &&
3176 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3177 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3178 break;
3179
3180 /* goto bad_output; */
3181 /* FALL THROUGH */
3182
3183 default:
3184 bad_output:
3185 png_error(png_ptr, "bad color-map processing (internal error)");
3186 }
3187
3188 /* Now read the rows. Do this here if it is possible to read directly into
3189 * the output buffer, otherwise allocate a local row buffer of the maximum
3190 * size libpng requires and call the relevant processing routine safely.
3191 */
3192 {
3193 png_voidp first_row = display->buffer;
3194 ptrdiff_t row_bytes = display->row_stride;
3195
3196 /* The following expression is designed to work correctly whether it gives
3197 * a signed or an unsigned result.
3198 */
3199 if (row_bytes < 0)
3200 {
3201 char *ptr = png_voidcast(char*, first_row);
3202 ptr += (image->height-1) * (-row_bytes);
3203 first_row = png_voidcast(png_voidp, ptr);
3204 }
3205
3206 display->first_row = first_row;
3207 display->row_bytes = row_bytes;
3208 }
3209
3210 if (passes == 0)
3211 {
3212 int result;
3213 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3214
3215 display->local_row = row;
3216 result = png_safe_execute(image, png_image_read_and_map, display);
3217 display->local_row = NULL;
3218 png_free(png_ptr, row);
3219
3220 return result;
3221 }
3222
3223 else
3224 {
3225 png_alloc_size_t row_bytes = display->row_bytes;
3226
3227 while (--passes >= 0)
3228 {
3229 png_uint_32 y = image->height;
3230 png_bytep row = png_voidcast(png_bytep, display->first_row);
3231
3232 while (y-- > 0)
3233 {
3234 png_read_row(png_ptr, row, NULL);
3235 row += row_bytes;
3236 }
3237 }
3238
3239 return 1;
3240 }
3241 }
3242
3243 /* Just the row reading part of png_image_read. */
3244 static int
png_image_read_composite(png_voidp argument)3245 png_image_read_composite(png_voidp argument)
3246 {
3247 png_image_read_control *display = png_voidcast(png_image_read_control*,
3248 argument);
3249 png_imagep image = display->image;
3250 png_structrp png_ptr = image->opaque->png_ptr;
3251 int passes;
3252
3253 switch (png_ptr->interlaced)
3254 {
3255 case PNG_INTERLACE_NONE:
3256 passes = 1;
3257 break;
3258
3259 case PNG_INTERLACE_ADAM7:
3260 passes = PNG_INTERLACE_ADAM7_PASSES;
3261 break;
3262
3263 default:
3264 png_error(png_ptr, "unknown interlace type");
3265 }
3266
3267 {
3268 png_uint_32 height = image->height;
3269 png_uint_32 width = image->width;
3270 ptrdiff_t step_row = display->row_bytes;
3271 unsigned int channels =
3272 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3273 int pass;
3274
3275 for (pass = 0; pass < passes; ++pass)
3276 {
3277 unsigned int startx, stepx, stepy;
3278 png_uint_32 y;
3279
3280 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3281 {
3282 /* The row may be empty for a short image: */
3283 if (PNG_PASS_COLS(width, pass) == 0)
3284 continue;
3285
3286 startx = PNG_PASS_START_COL(pass) * channels;
3287 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3288 y = PNG_PASS_START_ROW(pass);
3289 stepy = PNG_PASS_ROW_OFFSET(pass);
3290 }
3291
3292 else
3293 {
3294 y = 0;
3295 startx = 0;
3296 stepx = channels;
3297 stepy = 1;
3298 }
3299
3300 for (; y<height; y += stepy)
3301 {
3302 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3303 png_bytep outrow;
3304 png_const_bytep end_row;
3305
3306 /* Read the row, which is packed: */
3307 png_read_row(png_ptr, inrow, NULL);
3308
3309 outrow = png_voidcast(png_bytep, display->first_row);
3310 outrow += y * step_row;
3311 end_row = outrow + width * channels;
3312
3313 /* Now do the composition on each pixel in this row. */
3314 outrow += startx;
3315 for (; outrow < end_row; outrow += stepx)
3316 {
3317 png_byte alpha = inrow[channels];
3318
3319 if (alpha > 0) /* else no change to the output */
3320 {
3321 unsigned int c;
3322
3323 for (c=0; c<channels; ++c)
3324 {
3325 png_uint_32 component = inrow[c];
3326
3327 if (alpha < 255) /* else just use component */
3328 {
3329 /* This is PNG_OPTIMIZED_ALPHA, the component value
3330 * is a linear 8-bit value. Combine this with the
3331 * current outrow[c] value which is sRGB encoded.
3332 * Arithmetic here is 16-bits to preserve the output
3333 * values correctly.
3334 */
3335 component *= 257*255; /* =65535 */
3336 component += (255-alpha)*png_sRGB_table[outrow[c]];
3337
3338 /* So 'component' is scaled by 255*65535 and is
3339 * therefore appropriate for the sRGB to linear
3340 * conversion table.
3341 */
3342 component = PNG_sRGB_FROM_LINEAR(component);
3343 }
3344
3345 outrow[c] = (png_byte)component;
3346 }
3347 }
3348
3349 inrow += channels+1; /* components and alpha channel */
3350 }
3351 }
3352 }
3353 }
3354
3355 return 1;
3356 }
3357
3358 /* The do_local_background case; called when all the following transforms are to
3359 * be done:
3360 *
3361 * PNG_RGB_TO_GRAY
3362 * PNG_COMPOSITE
3363 * PNG_GAMMA
3364 *
3365 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3366 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3367 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3368 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3369 * row and handles the removal or pre-multiplication of the alpha channel.
3370 */
3371 static int
png_image_read_background(png_voidp argument)3372 png_image_read_background(png_voidp argument)
3373 {
3374 png_image_read_control *display = png_voidcast(png_image_read_control*,
3375 argument);
3376 png_imagep image = display->image;
3377 png_structrp png_ptr = image->opaque->png_ptr;
3378 png_inforp info_ptr = image->opaque->info_ptr;
3379 png_uint_32 height = image->height;
3380 png_uint_32 width = image->width;
3381 int pass, passes;
3382
3383 /* Double check the convoluted logic below. We expect to get here with
3384 * libpng doing rgb to gray and gamma correction but background processing
3385 * left to the png_image_read_background function. The rows libpng produce
3386 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3387 */
3388 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3389 png_error(png_ptr, "lost rgb to gray");
3390
3391 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3392 png_error(png_ptr, "unexpected compose");
3393
3394 if (png_get_channels(png_ptr, info_ptr) != 2)
3395 png_error(png_ptr, "lost/gained channels");
3396
3397 /* Expect the 8-bit case to always remove the alpha channel */
3398 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3399 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3400 png_error(png_ptr, "unexpected 8-bit transformation");
3401
3402 switch (png_ptr->interlaced)
3403 {
3404 case PNG_INTERLACE_NONE:
3405 passes = 1;
3406 break;
3407
3408 case PNG_INTERLACE_ADAM7:
3409 passes = PNG_INTERLACE_ADAM7_PASSES;
3410 break;
3411
3412 default:
3413 png_error(png_ptr, "unknown interlace type");
3414 }
3415
3416 /* Use direct access to info_ptr here because otherwise the simplified API
3417 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3418 * checking the value after libpng expansions, not the original value in the
3419 * PNG.
3420 */
3421 switch (info_ptr->bit_depth)
3422 {
3423 case 8:
3424 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3425 * to be removed by composing on a background: either the row if
3426 * display->background is NULL or display->background->green if not.
3427 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3428 */
3429 {
3430 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3431 ptrdiff_t step_row = display->row_bytes;
3432
3433 for (pass = 0; pass < passes; ++pass)
3434 {
3435 png_bytep row = png_voidcast(png_bytep, display->first_row);
3436 unsigned int startx, stepx, stepy;
3437 png_uint_32 y;
3438
3439 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3440 {
3441 /* The row may be empty for a short image: */
3442 if (PNG_PASS_COLS(width, pass) == 0)
3443 continue;
3444
3445 startx = PNG_PASS_START_COL(pass);
3446 stepx = PNG_PASS_COL_OFFSET(pass);
3447 y = PNG_PASS_START_ROW(pass);
3448 stepy = PNG_PASS_ROW_OFFSET(pass);
3449 }
3450
3451 else
3452 {
3453 y = 0;
3454 startx = 0;
3455 stepx = stepy = 1;
3456 }
3457
3458 if (display->background == NULL)
3459 {
3460 for (; y<height; y += stepy)
3461 {
3462 png_bytep inrow = png_voidcast(png_bytep,
3463 display->local_row);
3464 png_bytep outrow = first_row + y * step_row;
3465 png_const_bytep end_row = outrow + width;
3466
3467 /* Read the row, which is packed: */
3468 png_read_row(png_ptr, inrow, NULL);
3469
3470 /* Now do the composition on each pixel in this row. */
3471 outrow += startx;
3472 for (; outrow < end_row; outrow += stepx)
3473 {
3474 png_byte alpha = inrow[1];
3475
3476 if (alpha > 0) /* else no change to the output */
3477 {
3478 png_uint_32 component = inrow[0];
3479
3480 if (alpha < 255) /* else just use component */
3481 {
3482 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3483 * necessary to invert the sRGB transfer
3484 * function and multiply the alpha out.
3485 */
3486 component = png_sRGB_table[component] * alpha;
3487 component += png_sRGB_table[outrow[0]] *
3488 (255-alpha);
3489 component = PNG_sRGB_FROM_LINEAR(component);
3490 }
3491
3492 outrow[0] = (png_byte)component;
3493 }
3494
3495 inrow += 2; /* gray and alpha channel */
3496 }
3497 }
3498 }
3499
3500 else /* constant background value */
3501 {
3502 png_byte background8 = display->background->green;
3503 png_uint_16 background = png_sRGB_table[background8];
3504
3505 for (; y<height; y += stepy)
3506 {
3507 png_bytep inrow = png_voidcast(png_bytep,
3508 display->local_row);
3509 png_bytep outrow = first_row + y * step_row;
3510 png_const_bytep end_row = outrow + width;
3511
3512 /* Read the row, which is packed: */
3513 png_read_row(png_ptr, inrow, NULL);
3514
3515 /* Now do the composition on each pixel in this row. */
3516 outrow += startx;
3517 for (; outrow < end_row; outrow += stepx)
3518 {
3519 png_byte alpha = inrow[1];
3520
3521 if (alpha > 0) /* else use background */
3522 {
3523 png_uint_32 component = inrow[0];
3524
3525 if (alpha < 255) /* else just use component */
3526 {
3527 component = png_sRGB_table[component] * alpha;
3528 component += background * (255-alpha);
3529 component = PNG_sRGB_FROM_LINEAR(component);
3530 }
3531
3532 outrow[0] = (png_byte)component;
3533 }
3534
3535 else
3536 outrow[0] = background8;
3537
3538 inrow += 2; /* gray and alpha channel */
3539 }
3540
3541 row += display->row_bytes;
3542 }
3543 }
3544 }
3545 }
3546 break;
3547
3548 case 16:
3549 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3550 * still be done and, maybe, the alpha channel removed. This code also
3551 * handles the alpha-first option.
3552 */
3553 {
3554 png_uint_16p first_row = png_voidcast(png_uint_16p,
3555 display->first_row);
3556 /* The division by two is safe because the caller passed in a
3557 * stride which was multiplied by 2 (below) to get row_bytes.
3558 */
3559 ptrdiff_t step_row = display->row_bytes / 2;
3560 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
3561 unsigned int outchannels = 1+preserve_alpha;
3562 int swap_alpha = 0;
3563
3564 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3565 if (preserve_alpha != 0 &&
3566 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3567 swap_alpha = 1;
3568 # endif
3569
3570 for (pass = 0; pass < passes; ++pass)
3571 {
3572 unsigned int startx, stepx, stepy;
3573 png_uint_32 y;
3574
3575 /* The 'x' start and step are adjusted to output components here.
3576 */
3577 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3578 {
3579 /* The row may be empty for a short image: */
3580 if (PNG_PASS_COLS(width, pass) == 0)
3581 continue;
3582
3583 startx = PNG_PASS_START_COL(pass) * outchannels;
3584 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3585 y = PNG_PASS_START_ROW(pass);
3586 stepy = PNG_PASS_ROW_OFFSET(pass);
3587 }
3588
3589 else
3590 {
3591 y = 0;
3592 startx = 0;
3593 stepx = outchannels;
3594 stepy = 1;
3595 }
3596
3597 for (; y<height; y += stepy)
3598 {
3599 png_const_uint_16p inrow;
3600 png_uint_16p outrow = first_row + y*step_row;
3601 png_uint_16p end_row = outrow + width * outchannels;
3602
3603 /* Read the row, which is packed: */
3604 png_read_row(png_ptr, png_voidcast(png_bytep,
3605 display->local_row), NULL);
3606 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3607
3608 /* Now do the pre-multiplication on each pixel in this row.
3609 */
3610 outrow += startx;
3611 for (; outrow < end_row; outrow += stepx)
3612 {
3613 png_uint_32 component = inrow[0];
3614 png_uint_16 alpha = inrow[1];
3615
3616 if (alpha > 0) /* else 0 */
3617 {
3618 if (alpha < 65535) /* else just use component */
3619 {
3620 component *= alpha;
3621 component += 32767;
3622 component /= 65535;
3623 }
3624 }
3625
3626 else
3627 component = 0;
3628
3629 outrow[swap_alpha] = (png_uint_16)component;
3630 if (preserve_alpha != 0)
3631 outrow[1 ^ swap_alpha] = alpha;
3632
3633 inrow += 2; /* components and alpha channel */
3634 }
3635 }
3636 }
3637 }
3638 break;
3639
3640 #ifdef __GNUC__
3641 default:
3642 png_error(png_ptr, "unexpected bit depth");
3643 #endif
3644 }
3645
3646 return 1;
3647 }
3648
3649 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3650 static int
png_image_read_direct(png_voidp argument)3651 png_image_read_direct(png_voidp argument)
3652 {
3653 png_image_read_control *display = png_voidcast(png_image_read_control*,
3654 argument);
3655 png_imagep image = display->image;
3656 png_structrp png_ptr = image->opaque->png_ptr;
3657 png_inforp info_ptr = image->opaque->info_ptr;
3658
3659 png_uint_32 format = image->format;
3660 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3661 int do_local_compose = 0;
3662 int do_local_background = 0; /* to avoid double gamma correction bug */
3663 int passes = 0;
3664
3665 /* Add transforms to ensure the correct output format is produced then check
3666 * that the required implementation support is there. Always expand; always
3667 * need 8 bits minimum, no palette and expanded tRNS.
3668 */
3669 png_set_expand(png_ptr);
3670
3671 /* Now check the format to see if it was modified. */
3672 {
3673 png_uint_32 base_format = png_image_format(png_ptr) &
3674 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3675 png_uint_32 change = format ^ base_format;
3676 png_fixed_point output_gamma;
3677 int mode; /* alpha mode */
3678
3679 /* Do this first so that we have a record if rgb to gray is happening. */
3680 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3681 {
3682 /* gray<->color transformation required. */
3683 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3684 png_set_gray_to_rgb(png_ptr);
3685
3686 else
3687 {
3688 /* libpng can't do both rgb to gray and
3689 * background/pre-multiplication if there is also significant gamma
3690 * correction, because both operations require linear colors and
3691 * the code only supports one transform doing the gamma correction.
3692 * Handle this by doing the pre-multiplication or background
3693 * operation in this code, if necessary.
3694 *
3695 * TODO: fix this by rewriting pngrtran.c (!)
3696 *
3697 * For the moment (given that fixing this in pngrtran.c is an
3698 * enormous change) 'do_local_background' is used to indicate that
3699 * the problem exists.
3700 */
3701 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3702 do_local_background = 1/*maybe*/;
3703
3704 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3705 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3706 }
3707
3708 change &= ~PNG_FORMAT_FLAG_COLOR;
3709 }
3710
3711 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3712 */
3713 {
3714 png_fixed_point input_gamma_default;
3715
3716 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3717 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3718 input_gamma_default = PNG_GAMMA_LINEAR;
3719 else
3720 input_gamma_default = PNG_DEFAULT_sRGB;
3721
3722 /* Call png_set_alpha_mode to set the default for the input gamma; the
3723 * output gamma is set by a second call below.
3724 */
3725 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3726 }
3727
3728 if (linear != 0)
3729 {
3730 /* If there *is* an alpha channel in the input it must be multiplied
3731 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3732 */
3733 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3734 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3735
3736 else
3737 mode = PNG_ALPHA_PNG;
3738
3739 output_gamma = PNG_GAMMA_LINEAR;
3740 }
3741
3742 else
3743 {
3744 mode = PNG_ALPHA_PNG;
3745 output_gamma = PNG_DEFAULT_sRGB;
3746 }
3747
3748 /* If 'do_local_background' is set check for the presence of gamma
3749 * correction; this is part of the work-round for the libpng bug
3750 * described above.
3751 *
3752 * TODO: fix libpng and remove this.
3753 */
3754 if (do_local_background != 0)
3755 {
3756 png_fixed_point gtest;
3757
3758 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3759 * gamma correction, the screen gamma hasn't been set on png_struct
3760 * yet; it's set below. png_struct::gamma, however, is set to the
3761 * final value.
3762 */
3763 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3764 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3765 do_local_background = 0;
3766
3767 else if (mode == PNG_ALPHA_STANDARD)
3768 {
3769 do_local_background = 2/*required*/;
3770 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3771 }
3772
3773 /* else leave as 1 for the checks below */
3774 }
3775
3776 /* If the bit-depth changes then handle that here. */
3777 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3778 {
3779 if (linear != 0 /*16-bit output*/)
3780 png_set_expand_16(png_ptr);
3781
3782 else /* 8-bit output */
3783 png_set_scale_16(png_ptr);
3784
3785 change &= ~PNG_FORMAT_FLAG_LINEAR;
3786 }
3787
3788 /* Now the background/alpha channel changes. */
3789 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3790 {
3791 /* Removing an alpha channel requires composition for the 8-bit
3792 * formats; for the 16-bit it is already done, above, by the
3793 * pre-multiplication and the channel just needs to be stripped.
3794 */
3795 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3796 {
3797 /* If RGB->gray is happening the alpha channel must be left and the
3798 * operation completed locally.
3799 *
3800 * TODO: fix libpng and remove this.
3801 */
3802 if (do_local_background != 0)
3803 do_local_background = 2/*required*/;
3804
3805 /* 16-bit output: just remove the channel */
3806 else if (linear != 0) /* compose on black (well, pre-multiply) */
3807 png_set_strip_alpha(png_ptr);
3808
3809 /* 8-bit output: do an appropriate compose */
3810 else if (display->background != NULL)
3811 {
3812 png_color_16 c;
3813
3814 c.index = 0; /*unused*/
3815 c.red = display->background->red;
3816 c.green = display->background->green;
3817 c.blue = display->background->blue;
3818 c.gray = display->background->green;
3819
3820 /* This is always an 8-bit sRGB value, using the 'green' channel
3821 * for gray is much better than calculating the luminance here;
3822 * we can get off-by-one errors in that calculation relative to
3823 * the app expectations and that will show up in transparent
3824 * pixels.
3825 */
3826 png_set_background_fixed(png_ptr, &c,
3827 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3828 0/*gamma: not used*/);
3829 }
3830
3831 else /* compose on row: implemented below. */
3832 {
3833 do_local_compose = 1;
3834 /* This leaves the alpha channel in the output, so it has to be
3835 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3836 * one so the code only has to hack on the pixels that require
3837 * composition.
3838 */
3839 mode = PNG_ALPHA_OPTIMIZED;
3840 }
3841 }
3842
3843 else /* output needs an alpha channel */
3844 {
3845 /* This is tricky because it happens before the swap operation has
3846 * been accomplished; however, the swap does *not* swap the added
3847 * alpha channel (weird API), so it must be added in the correct
3848 * place.
3849 */
3850 png_uint_32 filler; /* opaque filler */
3851 int where;
3852
3853 if (linear != 0)
3854 filler = 65535;
3855
3856 else
3857 filler = 255;
3858
3859 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3860 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3861 {
3862 where = PNG_FILLER_BEFORE;
3863 change &= ~PNG_FORMAT_FLAG_AFIRST;
3864 }
3865
3866 else
3867 #endif
3868 where = PNG_FILLER_AFTER;
3869
3870 png_set_add_alpha(png_ptr, filler, where);
3871 }
3872
3873 /* This stops the (irrelevant) call to swap_alpha below. */
3874 change &= ~PNG_FORMAT_FLAG_ALPHA;
3875 }
3876
3877 /* Now set the alpha mode correctly; this is always done, even if there is
3878 * no alpha channel in either the input or the output because it correctly
3879 * sets the output gamma.
3880 */
3881 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3882
3883 # ifdef PNG_FORMAT_BGR_SUPPORTED
3884 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3885 {
3886 /* Check only the output format; PNG is never BGR; don't do this if
3887 * the output is gray, but fix up the 'format' value in that case.
3888 */
3889 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3890 png_set_bgr(png_ptr);
3891
3892 else
3893 format &= ~PNG_FORMAT_FLAG_BGR;
3894
3895 change &= ~PNG_FORMAT_FLAG_BGR;
3896 }
3897 # endif
3898
3899 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3900 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3901 {
3902 /* Only relevant if there is an alpha channel - it's particularly
3903 * important to handle this correctly because do_local_compose may
3904 * be set above and then libpng will keep the alpha channel for this
3905 * code to remove.
3906 */
3907 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3908 {
3909 /* Disable this if doing a local background,
3910 * TODO: remove this when local background is no longer required.
3911 */
3912 if (do_local_background != 2)
3913 png_set_swap_alpha(png_ptr);
3914 }
3915
3916 else
3917 format &= ~PNG_FORMAT_FLAG_AFIRST;
3918
3919 change &= ~PNG_FORMAT_FLAG_AFIRST;
3920 }
3921 # endif
3922
3923 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3924 * architecture.
3925 */
3926 if (linear != 0)
3927 {
3928 PNG_CONST png_uint_16 le = 0x0001;
3929
3930 if ((*(png_const_bytep) & le) != 0)
3931 png_set_swap(png_ptr);
3932 }
3933
3934 /* If change is not now 0 some transformation is missing - error out. */
3935 if (change != 0)
3936 png_error(png_ptr, "png_read_image: unsupported transformation");
3937 }
3938
3939 PNG_SKIP_CHUNKS(png_ptr);
3940
3941 /* Update the 'info' structure and make sure the result is as required; first
3942 * make sure to turn on the interlace handling if it will be required
3943 * (because it can't be turned on *after* the call to png_read_update_info!)
3944 *
3945 * TODO: remove the do_local_background fixup below.
3946 */
3947 if (do_local_compose == 0 && do_local_background != 2)
3948 passes = png_set_interlace_handling(png_ptr);
3949
3950 png_read_update_info(png_ptr, info_ptr);
3951
3952 {
3953 png_uint_32 info_format = 0;
3954
3955 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
3956 info_format |= PNG_FORMAT_FLAG_COLOR;
3957
3958 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
3959 {
3960 /* do_local_compose removes this channel below. */
3961 if (do_local_compose == 0)
3962 {
3963 /* do_local_background does the same if required. */
3964 if (do_local_background != 2 ||
3965 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
3966 info_format |= PNG_FORMAT_FLAG_ALPHA;
3967 }
3968 }
3969
3970 else if (do_local_compose != 0) /* internal error */
3971 png_error(png_ptr, "png_image_read: alpha channel lost");
3972
3973 if (info_ptr->bit_depth == 16)
3974 info_format |= PNG_FORMAT_FLAG_LINEAR;
3975
3976 #ifdef PNG_FORMAT_BGR_SUPPORTED
3977 if ((png_ptr->transformations & PNG_BGR) != 0)
3978 info_format |= PNG_FORMAT_FLAG_BGR;
3979 #endif
3980
3981 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3982 if (do_local_background == 2)
3983 {
3984 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3985 info_format |= PNG_FORMAT_FLAG_AFIRST;
3986 }
3987
3988 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
3989 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
3990 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
3991 {
3992 if (do_local_background == 2)
3993 png_error(png_ptr, "unexpected alpha swap transformation");
3994
3995 info_format |= PNG_FORMAT_FLAG_AFIRST;
3996 }
3997 # endif
3998
3999 /* This is actually an internal error. */
4000 if (info_format != format)
4001 png_error(png_ptr, "png_read_image: invalid transformations");
4002 }
4003
4004 /* Now read the rows. If do_local_compose is set then it is necessary to use
4005 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4006 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4007 * display acts as a flag.
4008 */
4009 {
4010 png_voidp first_row = display->buffer;
4011 ptrdiff_t row_bytes = display->row_stride;
4012
4013 if (linear != 0)
4014 row_bytes *= 2;
4015
4016 /* The following expression is designed to work correctly whether it gives
4017 * a signed or an unsigned result.
4018 */
4019 if (row_bytes < 0)
4020 {
4021 char *ptr = png_voidcast(char*, first_row);
4022 ptr += (image->height-1) * (-row_bytes);
4023 first_row = png_voidcast(png_voidp, ptr);
4024 }
4025
4026 display->first_row = first_row;
4027 display->row_bytes = row_bytes;
4028 }
4029
4030 if (do_local_compose != 0)
4031 {
4032 int result;
4033 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4034
4035 display->local_row = row;
4036 result = png_safe_execute(image, png_image_read_composite, display);
4037 display->local_row = NULL;
4038 png_free(png_ptr, row);
4039
4040 return result;
4041 }
4042
4043 else if (do_local_background == 2)
4044 {
4045 int result;
4046 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4047
4048 display->local_row = row;
4049 result = png_safe_execute(image, png_image_read_background, display);
4050 display->local_row = NULL;
4051 png_free(png_ptr, row);
4052
4053 return result;
4054 }
4055
4056 else
4057 {
4058 png_alloc_size_t row_bytes = display->row_bytes;
4059
4060 while (--passes >= 0)
4061 {
4062 png_uint_32 y = image->height;
4063 png_bytep row = png_voidcast(png_bytep, display->first_row);
4064
4065 while (y-- > 0)
4066 {
4067 png_read_row(png_ptr, row, NULL);
4068 row += row_bytes;
4069 }
4070 }
4071
4072 return 1;
4073 }
4074 }
4075
4076 int PNGAPI
png_image_finish_read(png_imagep image,png_const_colorp background,void * buffer,png_int_32 row_stride,void * colormap)4077 png_image_finish_read(png_imagep image, png_const_colorp background,
4078 void *buffer, png_int_32 row_stride, void *colormap)
4079 {
4080 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4081 {
4082 /* Check for row_stride overflow. This check is not performed on the
4083 * original PNG format because it may not occur in the output PNG format
4084 * and libpng deals with the issues of reading the original.
4085 */
4086 const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4087
4088 /* The following checks just the 'row_stride' calculation to ensure it
4089 * fits in a signed 32-bit value. Because channels/components can be
4090 * either 1 or 2 bytes in size the length of a row can still overflow 32
4091 * bits; this is just to verify that the 'row_stride' argument can be
4092 * represented.
4093 */
4094 if (image->width <= 0x7FFFFFFFU/channels) /* no overflow */
4095 {
4096 png_uint_32 check;
4097 const png_uint_32 png_row_stride = image->width * channels;
4098
4099 if (row_stride == 0)
4100 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4101
4102 if (row_stride < 0)
4103 check = -row_stride;
4104
4105 else
4106 check = row_stride;
4107
4108 /* This verifies 'check', the absolute value of the actual stride
4109 * passed in and detects overflow in the application calculation (i.e.
4110 * if the app did actually pass in a non-zero 'row_stride'.
4111 */
4112 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4113 {
4114 /* Now check for overflow of the image buffer calculation; this
4115 * limits the whole image size to 32 bits for API compatibility with
4116 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4117 *
4118 * The PNG_IMAGE_BUFFER_SIZE macro is:
4119 *
4120 * (PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)*height*(row_stride))
4121 *
4122 * And the component size is always 1 or 2, so make sure that the
4123 * number of *bytes* that the application is saying are available
4124 * does actually fit into a 32-bit number.
4125 *
4126 * NOTE: this will be changed in 1.7 because PNG_IMAGE_BUFFER_SIZE
4127 * will be changed to use png_alloc_size_t; bigger images can be
4128 * accomodated on 64-bit systems.
4129 */
4130 if (image->height <=
4131 0xFFFFFFFFU/PNG_IMAGE_PIXEL_COMPONENT_SIZE(image->format)/check)
4132 {
4133 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4134 (image->colormap_entries > 0 && colormap != NULL))
4135 {
4136 int result;
4137 png_image_read_control display;
4138
4139 memset(&display, 0, (sizeof display));
4140 display.image = image;
4141 display.buffer = buffer;
4142 display.row_stride = row_stride;
4143 display.colormap = colormap;
4144 display.background = background;
4145 display.local_row = NULL;
4146
4147 /* Choose the correct 'end' routine; for the color-map case
4148 * all the setup has already been done.
4149 */
4150 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4151 result =
4152 png_safe_execute(image,
4153 png_image_read_colormap, &display) &&
4154 png_safe_execute(image,
4155 png_image_read_colormapped, &display);
4156
4157 else
4158 result =
4159 png_safe_execute(image,
4160 png_image_read_direct, &display);
4161
4162 png_image_free(image);
4163 return result;
4164 }
4165
4166 else
4167 return png_image_error(image,
4168 "png_image_finish_read[color-map]: no color-map");
4169 }
4170
4171 else
4172 return png_image_error(image,
4173 "png_image_finish_read: image too large");
4174 }
4175
4176 else
4177 return png_image_error(image,
4178 "png_image_finish_read: invalid argument");
4179 }
4180
4181 else
4182 return png_image_error(image,
4183 "png_image_finish_read: row_stride too large");
4184 }
4185
4186 else if (image != NULL)
4187 return png_image_error(image,
4188 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4189
4190 return 0;
4191 }
4192
4193 #endif /* SIMPLIFIED_READ */
4194 #endif /* READ */
4195