1
2 /* pngread.c - read a PNG file
3 *
4 * Last changed in libpng 1.6.17 [March 26, 2015]
5 * Copyright (c) 1998-2002,2004,2006-2015 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,
1034 voidp params)
1035 {
1036 if (png_ptr == NULL || info_ptr == NULL)
1037 return;
1038
1039 /* png_read_info() gives us all of the information from the
1040 * PNG file before the first IDAT (image data chunk).
1041 */
1042 png_read_info(png_ptr, info_ptr);
1043 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1044 png_error(png_ptr, "Image is too high to process with png_read_png()");
1045
1046 /* -------------- image transformations start here ------------------- */
1047 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1048 * is not implemented. This will only happen in de-configured (non-default)
1049 * libpng builds. The results can be unexpected - png_read_png may return
1050 * short or mal-formed rows because the transform is skipped.
1051 */
1052
1053 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1054 */
1055 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1056 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1057 * did in earlier versions, while "scale_16" is now more accurate.
1058 */
1059 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1060 png_set_scale_16(png_ptr);
1061 #else
1062 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1063 #endif
1064
1065 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1066 * latter by doing SCALE first. This is ok and allows apps not to check for
1067 * which is supported to get the right answer.
1068 */
1069 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1070 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1071 png_set_strip_16(png_ptr);
1072 #else
1073 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1074 #endif
1075
1076 /* Strip alpha bytes from the input data without combining with
1077 * the background (not recommended).
1078 */
1079 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1080 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1081 png_set_strip_alpha(png_ptr);
1082 #else
1083 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1084 #endif
1085
1086 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1087 * byte into separate bytes (useful for paletted and grayscale images).
1088 */
1089 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1090 #ifdef PNG_READ_PACK_SUPPORTED
1091 png_set_packing(png_ptr);
1092 #else
1093 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1094 #endif
1095
1096 /* Change the order of packed pixels to least significant bit first
1097 * (not useful if you are using png_set_packing).
1098 */
1099 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1100 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1101 png_set_packswap(png_ptr);
1102 #else
1103 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1104 #endif
1105
1106 /* Expand paletted colors into true RGB triplets
1107 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1108 * Expand paletted or RGB images with transparency to full alpha
1109 * channels so the data will be available as RGBA quartets.
1110 */
1111 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1112 #ifdef PNG_READ_EXPAND_SUPPORTED
1113 png_set_expand(png_ptr);
1114 #else
1115 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1116 #endif
1117
1118 /* We don't handle background color or gamma transformation or quantizing.
1119 */
1120
1121 /* Invert monochrome files to have 0 as white and 1 as black
1122 */
1123 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1124 #ifdef PNG_READ_INVERT_SUPPORTED
1125 png_set_invert_mono(png_ptr);
1126 #else
1127 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1128 #endif
1129
1130 /* If you want to shift the pixel values from the range [0,255] or
1131 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1132 * colors were originally in:
1133 */
1134 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1135 #ifdef PNG_READ_SHIFT_SUPPORTED
1136 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1137 png_set_shift(png_ptr, &info_ptr->sig_bit);
1138 #else
1139 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1140 #endif
1141
1142 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1143 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1144 #ifdef PNG_READ_BGR_SUPPORTED
1145 png_set_bgr(png_ptr);
1146 #else
1147 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1148 #endif
1149
1150 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1151 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1152 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1153 png_set_swap_alpha(png_ptr);
1154 #else
1155 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1156 #endif
1157
1158 /* Swap bytes of 16-bit files to least significant byte first */
1159 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1160 #ifdef PNG_READ_SWAP_SUPPORTED
1161 png_set_swap(png_ptr);
1162 #else
1163 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1164 #endif
1165
1166 /* Added at libpng-1.2.41 */
1167 /* Invert the alpha channel from opacity to transparency */
1168 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1169 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1170 png_set_invert_alpha(png_ptr);
1171 #else
1172 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1173 #endif
1174
1175 /* Added at libpng-1.2.41 */
1176 /* Expand grayscale image to RGB */
1177 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1178 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1179 png_set_gray_to_rgb(png_ptr);
1180 #else
1181 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1182 #endif
1183
1184 /* Added at libpng-1.5.4 */
1185 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1186 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1187 png_set_expand_16(png_ptr);
1188 #else
1189 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1190 #endif
1191
1192 /* We don't handle adding filler bytes */
1193
1194 /* We use png_read_image and rely on that for interlace handling, but we also
1195 * call png_read_update_info therefore must turn on interlace handling now:
1196 */
1197 (void)png_set_interlace_handling(png_ptr);
1198
1199 /* Optional call to gamma correct and add the background to the palette
1200 * and update info structure. REQUIRED if you are expecting libpng to
1201 * update the palette for you (i.e., you selected such a transform above).
1202 */
1203 png_read_update_info(png_ptr, info_ptr);
1204
1205 /* -------------- image transformations end here ------------------- */
1206
1207 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1208 if (info_ptr->row_pointers == NULL)
1209 {
1210 png_uint_32 iptr;
1211
1212 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1213 info_ptr->height * (sizeof (png_bytep))));
1214
1215 for (iptr=0; iptr<info_ptr->height; iptr++)
1216 info_ptr->row_pointers[iptr] = NULL;
1217
1218 info_ptr->free_me |= PNG_FREE_ROWS;
1219
1220 for (iptr = 0; iptr < info_ptr->height; iptr++)
1221 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1222 png_malloc(png_ptr, info_ptr->rowbytes));
1223 }
1224
1225 png_read_image(png_ptr, info_ptr->row_pointers);
1226 info_ptr->valid |= PNG_INFO_IDAT;
1227
1228 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1229 png_read_end(png_ptr, info_ptr);
1230
1231 PNG_UNUSED(params)
1232 }
1233 #endif /* INFO_IMAGE */
1234 #endif /* SEQUENTIAL_READ */
1235
1236 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1237 /* SIMPLIFIED READ
1238 *
1239 * This code currently relies on the sequential reader, though it could easily
1240 * be made to work with the progressive one.
1241 */
1242 /* Arguments to png_image_finish_read: */
1243
1244 /* Encoding of PNG data (used by the color-map code) */
1245 # define P_NOTSET 0 /* File encoding not yet known */
1246 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1247 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1248 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1249 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1250
1251 /* Color-map processing: after libpng has run on the PNG image further
1252 * processing may be needed to convert the data to color-map indices.
1253 */
1254 #define PNG_CMAP_NONE 0
1255 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1256 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1257 #define PNG_CMAP_RGB 3 /* Process RGB data */
1258 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1259
1260 /* The following document where the background is for each processing case. */
1261 #define PNG_CMAP_NONE_BACKGROUND 256
1262 #define PNG_CMAP_GA_BACKGROUND 231
1263 #define PNG_CMAP_TRANS_BACKGROUND 254
1264 #define PNG_CMAP_RGB_BACKGROUND 256
1265 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1266
1267 typedef struct
1268 {
1269 /* Arguments: */
1270 png_imagep image;
1271 png_voidp buffer;
1272 png_int_32 row_stride;
1273 png_voidp colormap;
1274 png_const_colorp background;
1275 /* Local variables: */
1276 png_voidp local_row;
1277 png_voidp first_row;
1278 ptrdiff_t row_bytes; /* step between rows */
1279 int file_encoding; /* E_ values above */
1280 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1281 int colormap_processing; /* PNG_CMAP_ values above */
1282 } png_image_read_control;
1283
1284 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1285 * called, so setting up the jmp_buf is not required. This means that anything
1286 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1287 * instead so that control is returned safely back to this routine.
1288 */
1289 static int
png_image_read_init(png_imagep image)1290 png_image_read_init(png_imagep image)
1291 {
1292 if (image->opaque == NULL)
1293 {
1294 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1295 png_safe_error, png_safe_warning);
1296
1297 /* And set the rest of the structure to NULL to ensure that the various
1298 * fields are consistent.
1299 */
1300 memset(image, 0, (sizeof *image));
1301 image->version = PNG_IMAGE_VERSION;
1302
1303 if (png_ptr != NULL)
1304 {
1305 png_infop info_ptr = png_create_info_struct(png_ptr);
1306
1307 if (info_ptr != NULL)
1308 {
1309 png_controlp control = png_voidcast(png_controlp,
1310 png_malloc_warn(png_ptr, (sizeof *control)));
1311
1312 if (control != NULL)
1313 {
1314 memset(control, 0, (sizeof *control));
1315
1316 control->png_ptr = png_ptr;
1317 control->info_ptr = info_ptr;
1318 control->for_write = 0;
1319
1320 image->opaque = control;
1321 return 1;
1322 }
1323
1324 /* Error clean up */
1325 png_destroy_info_struct(png_ptr, &info_ptr);
1326 }
1327
1328 png_destroy_read_struct(&png_ptr, NULL, NULL);
1329 }
1330
1331 return png_image_error(image, "png_image_read: out of memory");
1332 }
1333
1334 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1335 }
1336
1337 /* Utility to find the base format of a PNG file from a png_struct. */
1338 static png_uint_32
png_image_format(png_structrp png_ptr)1339 png_image_format(png_structrp png_ptr)
1340 {
1341 png_uint_32 format = 0;
1342
1343 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1344 format |= PNG_FORMAT_FLAG_COLOR;
1345
1346 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1347 format |= PNG_FORMAT_FLAG_ALPHA;
1348
1349 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1350 * sets the png_struct fields; that's all we are interested in here. The
1351 * precise interaction with an app call to png_set_tRNS and PNG file reading
1352 * is unclear.
1353 */
1354 else if (png_ptr->num_trans > 0)
1355 format |= PNG_FORMAT_FLAG_ALPHA;
1356
1357 if (png_ptr->bit_depth == 16)
1358 format |= PNG_FORMAT_FLAG_LINEAR;
1359
1360 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1361 format |= PNG_FORMAT_FLAG_COLORMAP;
1362
1363 return format;
1364 }
1365
1366 /* Is the given gamma significantly different from sRGB? The test is the same
1367 * one used in pngrtran.c when deciding whether to do gamma correction. The
1368 * arithmetic optimizes the division by using the fact that the inverse of the
1369 * file sRGB gamma is 2.2
1370 */
1371 static int
png_gamma_not_sRGB(png_fixed_point g)1372 png_gamma_not_sRGB(png_fixed_point g)
1373 {
1374 if (g < PNG_FP_1)
1375 {
1376 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1377 if (g == 0)
1378 return 0;
1379
1380 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1381 }
1382
1383 return 1;
1384 }
1385
1386 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1387 * header and fill in all the information. This is executed in a safe context,
1388 * unlike the init routine above.
1389 */
1390 static int
png_image_read_header(png_voidp argument)1391 png_image_read_header(png_voidp argument)
1392 {
1393 png_imagep image = png_voidcast(png_imagep, argument);
1394 png_structrp png_ptr = image->opaque->png_ptr;
1395 png_inforp info_ptr = image->opaque->info_ptr;
1396
1397 png_set_benign_errors(png_ptr, 1/*warn*/);
1398 png_read_info(png_ptr, info_ptr);
1399
1400 /* Do this the fast way; just read directly out of png_struct. */
1401 image->width = png_ptr->width;
1402 image->height = png_ptr->height;
1403
1404 {
1405 png_uint_32 format = png_image_format(png_ptr);
1406
1407 image->format = format;
1408
1409 #ifdef PNG_COLORSPACE_SUPPORTED
1410 /* Does the colorspace match sRGB? If there is no color endpoint
1411 * (colorant) information assume yes, otherwise require the
1412 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1413 * colorspace has been determined to be invalid ignore it.
1414 */
1415 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1416 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1417 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1418 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1419 #endif
1420 }
1421
1422 /* We need the maximum number of entries regardless of the format the
1423 * application sets here.
1424 */
1425 {
1426 png_uint_32 cmap_entries;
1427
1428 switch (png_ptr->color_type)
1429 {
1430 case PNG_COLOR_TYPE_GRAY:
1431 cmap_entries = 1U << png_ptr->bit_depth;
1432 break;
1433
1434 case PNG_COLOR_TYPE_PALETTE:
1435 cmap_entries = png_ptr->num_palette;
1436 break;
1437
1438 default:
1439 cmap_entries = 256;
1440 break;
1441 }
1442
1443 if (cmap_entries > 256)
1444 cmap_entries = 256;
1445
1446 image->colormap_entries = cmap_entries;
1447 }
1448
1449 return 1;
1450 }
1451
1452 #ifdef PNG_STDIO_SUPPORTED
1453 int PNGAPI
png_image_begin_read_from_stdio(png_imagep image,FILE * file)1454 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1455 {
1456 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1457 {
1458 if (file != NULL)
1459 {
1460 if (png_image_read_init(image) != 0)
1461 {
1462 /* This is slightly evil, but png_init_io doesn't do anything other
1463 * than this and we haven't changed the standard IO functions so
1464 * this saves a 'safe' function.
1465 */
1466 image->opaque->png_ptr->io_ptr = file;
1467 return png_safe_execute(image, png_image_read_header, image);
1468 }
1469 }
1470
1471 else
1472 return png_image_error(image,
1473 "png_image_begin_read_from_stdio: invalid argument");
1474 }
1475
1476 else if (image != NULL)
1477 return png_image_error(image,
1478 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1479
1480 return 0;
1481 }
1482
1483 int PNGAPI
png_image_begin_read_from_file(png_imagep image,const char * file_name)1484 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1485 {
1486 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1487 {
1488 if (file_name != NULL)
1489 {
1490 FILE *fp = fopen(file_name, "rb");
1491
1492 if (fp != NULL)
1493 {
1494 if (png_image_read_init(image) != 0)
1495 {
1496 image->opaque->png_ptr->io_ptr = fp;
1497 image->opaque->owned_file = 1;
1498 return png_safe_execute(image, png_image_read_header, image);
1499 }
1500
1501 /* Clean up: just the opened file. */
1502 (void)fclose(fp);
1503 }
1504
1505 else
1506 return png_image_error(image, strerror(errno));
1507 }
1508
1509 else
1510 return png_image_error(image,
1511 "png_image_begin_read_from_file: invalid argument");
1512 }
1513
1514 else if (image != NULL)
1515 return png_image_error(image,
1516 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1517
1518 return 0;
1519 }
1520 #endif /* STDIO */
1521
1522 static void PNGCBAPI
png_image_memory_read(png_structp png_ptr,png_bytep out,png_size_t need)1523 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1524 {
1525 if (png_ptr != NULL)
1526 {
1527 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1528 if (image != NULL)
1529 {
1530 png_controlp cp = image->opaque;
1531 if (cp != NULL)
1532 {
1533 png_const_bytep memory = cp->memory;
1534 png_size_t size = cp->size;
1535
1536 if (memory != NULL && size >= need)
1537 {
1538 memcpy(out, memory, need);
1539 cp->memory = memory + need;
1540 cp->size = size - need;
1541 return;
1542 }
1543
1544 png_error(png_ptr, "read beyond end of data");
1545 }
1546 }
1547
1548 png_error(png_ptr, "invalid memory read");
1549 }
1550 }
1551
png_image_begin_read_from_memory(png_imagep image,png_const_voidp memory,png_size_t size)1552 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1553 png_const_voidp memory, png_size_t size)
1554 {
1555 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1556 {
1557 if (memory != NULL && size > 0)
1558 {
1559 if (png_image_read_init(image) != 0)
1560 {
1561 /* Now set the IO functions to read from the memory buffer and
1562 * store it into io_ptr. Again do this in-place to avoid calling a
1563 * libpng function that requires error handling.
1564 */
1565 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1566 image->opaque->size = size;
1567 image->opaque->png_ptr->io_ptr = image;
1568 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1569
1570 return png_safe_execute(image, png_image_read_header, image);
1571 }
1572 }
1573
1574 else
1575 return png_image_error(image,
1576 "png_image_begin_read_from_memory: invalid argument");
1577 }
1578
1579 else if (image != NULL)
1580 return png_image_error(image,
1581 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1582
1583 return 0;
1584 }
1585
1586 /* Utility function to skip chunks that are not used by the simplified image
1587 * read functions and an appropriate macro to call it.
1588 */
1589 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1590 static void
png_image_skip_unused_chunks(png_structrp png_ptr)1591 png_image_skip_unused_chunks(png_structrp png_ptr)
1592 {
1593 /* Prepare the reader to ignore all recognized chunks whose data will not
1594 * be used, i.e., all chunks recognized by libpng except for those
1595 * involved in basic image reading:
1596 *
1597 * IHDR, PLTE, IDAT, IEND
1598 *
1599 * Or image data handling:
1600 *
1601 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1602 *
1603 * This provides a small performance improvement and eliminates any
1604 * potential vulnerability to security problems in the unused chunks.
1605 *
1606 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1607 * too. This allows the simplified API to be compiled without iCCP support,
1608 * however if the support is there the chunk is still checked to detect
1609 * errors (which are unfortunately quite common.)
1610 */
1611 {
1612 static PNG_CONST png_byte chunks_to_process[] = {
1613 98, 75, 71, 68, '\0', /* bKGD */
1614 99, 72, 82, 77, '\0', /* cHRM */
1615 103, 65, 77, 65, '\0', /* gAMA */
1616 # ifdef PNG_READ_iCCP_SUPPORTED
1617 105, 67, 67, 80, '\0', /* iCCP */
1618 # endif
1619 115, 66, 73, 84, '\0', /* sBIT */
1620 115, 82, 71, 66, '\0', /* sRGB */
1621 };
1622
1623 /* Ignore unknown chunks and all other chunks except for the
1624 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1625 */
1626 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1627 NULL, -1);
1628
1629 /* But do not ignore image data handling chunks */
1630 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1631 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1632 }
1633 }
1634
1635 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1636 #else
1637 # define PNG_SKIP_CHUNKS(p) ((void)0)
1638 #endif /* HANDLE_AS_UNKNOWN */
1639
1640 /* The following macro gives the exact rounded answer for all values in the
1641 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1642 * the correct numbers 0..5
1643 */
1644 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1645
1646 /* Utility functions to make particular color-maps */
1647 static void
set_file_encoding(png_image_read_control * display)1648 set_file_encoding(png_image_read_control *display)
1649 {
1650 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1651 if (png_gamma_significant(g) != 0)
1652 {
1653 if (png_gamma_not_sRGB(g) != 0)
1654 {
1655 display->file_encoding = P_FILE;
1656 display->gamma_to_linear = png_reciprocal(g);
1657 }
1658
1659 else
1660 display->file_encoding = P_sRGB;
1661 }
1662
1663 else
1664 display->file_encoding = P_LINEAR8;
1665 }
1666
1667 static unsigned int
decode_gamma(png_image_read_control * display,png_uint_32 value,int encoding)1668 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1669 {
1670 if (encoding == P_FILE) /* double check */
1671 encoding = display->file_encoding;
1672
1673 if (encoding == P_NOTSET) /* must be the file encoding */
1674 {
1675 set_file_encoding(display);
1676 encoding = display->file_encoding;
1677 }
1678
1679 switch (encoding)
1680 {
1681 case P_FILE:
1682 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1683 break;
1684
1685 case P_sRGB:
1686 value = png_sRGB_table[value];
1687 break;
1688
1689 case P_LINEAR:
1690 break;
1691
1692 case P_LINEAR8:
1693 value *= 257;
1694 break;
1695
1696 #ifdef __GNUC__
1697 default:
1698 png_error(display->image->opaque->png_ptr,
1699 "unexpected encoding (internal error)");
1700 #endif
1701 }
1702
1703 return value;
1704 }
1705
1706 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)1707 png_colormap_compose(png_image_read_control *display,
1708 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1709 png_uint_32 background, int encoding)
1710 {
1711 /* The file value is composed on the background, the background has the given
1712 * encoding and so does the result, the file is encoded with P_FILE and the
1713 * file and alpha are 8-bit values. The (output) encoding will always be
1714 * P_LINEAR or P_sRGB.
1715 */
1716 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1717 png_uint_32 b = decode_gamma(display, background, encoding);
1718
1719 /* The alpha is always an 8-bit value (it comes from the palette), the value
1720 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1721 */
1722 f = f * alpha + b * (255-alpha);
1723
1724 if (encoding == P_LINEAR)
1725 {
1726 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1727 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1728 */
1729 f *= 257; /* Now scaled by 65535 */
1730 f += f >> 16;
1731 f = (f+32768) >> 16;
1732 }
1733
1734 else /* P_sRGB */
1735 f = PNG_sRGB_FROM_LINEAR(f);
1736
1737 return f;
1738 }
1739
1740 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1741 * be 8-bit.
1742 */
1743 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)1744 png_create_colormap_entry(png_image_read_control *display,
1745 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1746 png_uint_32 alpha, int encoding)
1747 {
1748 png_imagep image = display->image;
1749 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1750 P_LINEAR : P_sRGB;
1751 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1752 (red != green || green != blue);
1753
1754 if (ip > 255)
1755 png_error(image->opaque->png_ptr, "color-map index out of range");
1756
1757 /* Update the cache with whether the file gamma is significantly different
1758 * from sRGB.
1759 */
1760 if (encoding == P_FILE)
1761 {
1762 if (display->file_encoding == P_NOTSET)
1763 set_file_encoding(display);
1764
1765 /* Note that the cached value may be P_FILE too, but if it is then the
1766 * gamma_to_linear member has been set.
1767 */
1768 encoding = display->file_encoding;
1769 }
1770
1771 if (encoding == P_FILE)
1772 {
1773 png_fixed_point g = display->gamma_to_linear;
1774
1775 red = png_gamma_16bit_correct(red*257, g);
1776 green = png_gamma_16bit_correct(green*257, g);
1777 blue = png_gamma_16bit_correct(blue*257, g);
1778
1779 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1780 {
1781 alpha *= 257;
1782 encoding = P_LINEAR;
1783 }
1784
1785 else
1786 {
1787 red = PNG_sRGB_FROM_LINEAR(red * 255);
1788 green = PNG_sRGB_FROM_LINEAR(green * 255);
1789 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1790 encoding = P_sRGB;
1791 }
1792 }
1793
1794 else if (encoding == P_LINEAR8)
1795 {
1796 /* This encoding occurs quite frequently in test cases because PngSuite
1797 * includes a gAMA 1.0 chunk with most images.
1798 */
1799 red *= 257;
1800 green *= 257;
1801 blue *= 257;
1802 alpha *= 257;
1803 encoding = P_LINEAR;
1804 }
1805
1806 else if (encoding == P_sRGB &&
1807 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1808 {
1809 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1810 * linear.
1811 */
1812 red = png_sRGB_table[red];
1813 green = png_sRGB_table[green];
1814 blue = png_sRGB_table[blue];
1815 alpha *= 257;
1816 encoding = P_LINEAR;
1817 }
1818
1819 /* This is set if the color isn't gray but the output is. */
1820 if (encoding == P_LINEAR)
1821 {
1822 if (convert_to_Y != 0)
1823 {
1824 /* NOTE: these values are copied from png_do_rgb_to_gray */
1825 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1826 (png_uint_32)2366 * blue;
1827
1828 if (output_encoding == P_LINEAR)
1829 y = (y + 16384) >> 15;
1830
1831 else
1832 {
1833 /* y is scaled by 32768, we need it scaled by 255: */
1834 y = (y + 128) >> 8;
1835 y *= 255;
1836 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1837 alpha = PNG_DIV257(alpha);
1838 encoding = P_sRGB;
1839 }
1840
1841 blue = red = green = y;
1842 }
1843
1844 else if (output_encoding == P_sRGB)
1845 {
1846 red = PNG_sRGB_FROM_LINEAR(red * 255);
1847 green = PNG_sRGB_FROM_LINEAR(green * 255);
1848 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1849 alpha = PNG_DIV257(alpha);
1850 encoding = P_sRGB;
1851 }
1852 }
1853
1854 if (encoding != output_encoding)
1855 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1856
1857 /* Store the value. */
1858 {
1859 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1860 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1861 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1862 # else
1863 # define afirst 0
1864 # endif
1865 # ifdef PNG_FORMAT_BGR_SUPPORTED
1866 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1867 # else
1868 # define bgr 0
1869 # endif
1870
1871 if (output_encoding == P_LINEAR)
1872 {
1873 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1874
1875 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1876
1877 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1878 * value, if less than 65535 (this is, effectively, composite on black
1879 * if the alpha channel is removed.)
1880 */
1881 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1882 {
1883 case 4:
1884 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1885 /* FALL THROUGH */
1886
1887 case 3:
1888 if (alpha < 65535)
1889 {
1890 if (alpha > 0)
1891 {
1892 blue = (blue * alpha + 32767U)/65535U;
1893 green = (green * alpha + 32767U)/65535U;
1894 red = (red * alpha + 32767U)/65535U;
1895 }
1896
1897 else
1898 red = green = blue = 0;
1899 }
1900 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1901 entry[afirst + 1] = (png_uint_16)green;
1902 entry[afirst + bgr] = (png_uint_16)red;
1903 break;
1904
1905 case 2:
1906 entry[1 ^ afirst] = (png_uint_16)alpha;
1907 /* FALL THROUGH */
1908
1909 case 1:
1910 if (alpha < 65535)
1911 {
1912 if (alpha > 0)
1913 green = (green * alpha + 32767U)/65535U;
1914
1915 else
1916 green = 0;
1917 }
1918 entry[afirst] = (png_uint_16)green;
1919 break;
1920
1921 default:
1922 break;
1923 }
1924 }
1925
1926 else /* output encoding is P_sRGB */
1927 {
1928 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1929
1930 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1931
1932 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1933 {
1934 case 4:
1935 entry[afirst ? 0 : 3] = (png_byte)alpha;
1936 case 3:
1937 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1938 entry[afirst + 1] = (png_byte)green;
1939 entry[afirst + bgr] = (png_byte)red;
1940 break;
1941
1942 case 2:
1943 entry[1 ^ afirst] = (png_byte)alpha;
1944 case 1:
1945 entry[afirst] = (png_byte)green;
1946 break;
1947
1948 default:
1949 break;
1950 }
1951 }
1952
1953 # ifdef afirst
1954 # undef afirst
1955 # endif
1956 # ifdef bgr
1957 # undef bgr
1958 # endif
1959 }
1960 }
1961
1962 static int
make_gray_file_colormap(png_image_read_control * display)1963 make_gray_file_colormap(png_image_read_control *display)
1964 {
1965 unsigned int i;
1966
1967 for (i=0; i<256; ++i)
1968 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1969
1970 return i;
1971 }
1972
1973 static int
make_gray_colormap(png_image_read_control * display)1974 make_gray_colormap(png_image_read_control *display)
1975 {
1976 unsigned int i;
1977
1978 for (i=0; i<256; ++i)
1979 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
1980
1981 return i;
1982 }
1983 #define PNG_GRAY_COLORMAP_ENTRIES 256
1984
1985 static int
make_ga_colormap(png_image_read_control * display)1986 make_ga_colormap(png_image_read_control *display)
1987 {
1988 unsigned int i, a;
1989
1990 /* Alpha is retained, the output will be a color-map with entries
1991 * selected by six levels of alpha. One transparent entry, 6 gray
1992 * levels for all the intermediate alpha values, leaving 230 entries
1993 * for the opaque grays. The color-map entries are the six values
1994 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
1995 * relevant entry.
1996 *
1997 * if (alpha > 229) // opaque
1998 * {
1999 * // The 231 entries are selected to make the math below work:
2000 * base = 0;
2001 * entry = (231 * gray + 128) >> 8;
2002 * }
2003 * else if (alpha < 26) // transparent
2004 * {
2005 * base = 231;
2006 * entry = 0;
2007 * }
2008 * else // partially opaque
2009 * {
2010 * base = 226 + 6 * PNG_DIV51(alpha);
2011 * entry = PNG_DIV51(gray);
2012 * }
2013 */
2014 i = 0;
2015 while (i < 231)
2016 {
2017 unsigned int gray = (i * 256 + 115) / 231;
2018 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2019 }
2020
2021 /* 255 is used here for the component values for consistency with the code
2022 * that undoes premultiplication in pngwrite.c.
2023 */
2024 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2025
2026 for (a=1; a<5; ++a)
2027 {
2028 unsigned int g;
2029
2030 for (g=0; g<6; ++g)
2031 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2032 P_sRGB);
2033 }
2034
2035 return i;
2036 }
2037
2038 #define PNG_GA_COLORMAP_ENTRIES 256
2039
2040 static int
make_rgb_colormap(png_image_read_control * display)2041 make_rgb_colormap(png_image_read_control *display)
2042 {
2043 unsigned int i, r;
2044
2045 /* Build a 6x6x6 opaque RGB cube */
2046 for (i=r=0; r<6; ++r)
2047 {
2048 unsigned int g;
2049
2050 for (g=0; g<6; ++g)
2051 {
2052 unsigned int b;
2053
2054 for (b=0; b<6; ++b)
2055 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2056 P_sRGB);
2057 }
2058 }
2059
2060 return i;
2061 }
2062
2063 #define PNG_RGB_COLORMAP_ENTRIES 216
2064
2065 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2066 #define PNG_RGB_INDEX(r,g,b) \
2067 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2068
2069 static int
png_image_read_colormap(png_voidp argument)2070 png_image_read_colormap(png_voidp argument)
2071 {
2072 png_image_read_control *display =
2073 png_voidcast(png_image_read_control*, argument);
2074 const png_imagep image = display->image;
2075
2076 const png_structrp png_ptr = image->opaque->png_ptr;
2077 const png_uint_32 output_format = image->format;
2078 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2079 P_LINEAR : P_sRGB;
2080
2081 unsigned int cmap_entries;
2082 unsigned int output_processing; /* Output processing option */
2083 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2084
2085 /* Background information; the background color and the index of this color
2086 * in the color-map if it exists (else 256).
2087 */
2088 unsigned int background_index = 256;
2089 png_uint_32 back_r, back_g, back_b;
2090
2091 /* Flags to accumulate things that need to be done to the input. */
2092 int expand_tRNS = 0;
2093
2094 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2095 * very difficult to do, the results look awful, and it is difficult to see
2096 * what possible use it is because the application can't control the
2097 * color-map.
2098 */
2099 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2100 png_ptr->num_trans > 0) /* alpha in input */ &&
2101 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2102 {
2103 if (output_encoding == P_LINEAR) /* compose on black */
2104 back_b = back_g = back_r = 0;
2105
2106 else if (display->background == NULL /* no way to remove it */)
2107 png_error(png_ptr,
2108 "a background color must be supplied to remove alpha/transparency");
2109
2110 /* Get a copy of the background color (this avoids repeating the checks
2111 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2112 * output format.
2113 */
2114 else
2115 {
2116 back_g = display->background->green;
2117 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2118 {
2119 back_r = display->background->red;
2120 back_b = display->background->blue;
2121 }
2122 else
2123 back_b = back_r = back_g;
2124 }
2125 }
2126
2127 else if (output_encoding == P_LINEAR)
2128 back_b = back_r = back_g = 65535;
2129
2130 else
2131 back_b = back_r = back_g = 255;
2132
2133 /* Default the input file gamma if required - this is necessary because
2134 * libpng assumes that if no gamma information is present the data is in the
2135 * output format, but the simplified API deduces the gamma from the input
2136 * format.
2137 */
2138 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2139 {
2140 /* Do this directly, not using the png_colorspace functions, to ensure
2141 * that it happens even if the colorspace is invalid (though probably if
2142 * it is the setting will be ignored) Note that the same thing can be
2143 * achieved at the application interface with png_set_gAMA.
2144 */
2145 if (png_ptr->bit_depth == 16 &&
2146 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2147 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2148
2149 else
2150 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2151
2152 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2153 }
2154
2155 /* Decide what to do based on the PNG color type of the input data. The
2156 * utility function png_create_colormap_entry deals with most aspects of the
2157 * output transformations; this code works out how to produce bytes of
2158 * color-map entries from the original format.
2159 */
2160 switch (png_ptr->color_type)
2161 {
2162 case PNG_COLOR_TYPE_GRAY:
2163 if (png_ptr->bit_depth <= 8)
2164 {
2165 /* There at most 256 colors in the output, regardless of
2166 * transparency.
2167 */
2168 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2169
2170 cmap_entries = 1U << png_ptr->bit_depth;
2171 if (cmap_entries > image->colormap_entries)
2172 png_error(png_ptr, "gray[8] color-map: too few entries");
2173
2174 step = 255 / (cmap_entries - 1);
2175 output_processing = PNG_CMAP_NONE;
2176
2177 /* If there is a tRNS chunk then this either selects a transparent
2178 * value or, if the output has no alpha, the background color.
2179 */
2180 if (png_ptr->num_trans > 0)
2181 {
2182 trans = png_ptr->trans_color.gray;
2183
2184 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2185 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2186 }
2187
2188 /* png_create_colormap_entry just takes an RGBA and writes the
2189 * corresponding color-map entry using the format from 'image',
2190 * including the required conversion to sRGB or linear as
2191 * appropriate. The input values are always either sRGB (if the
2192 * gamma correction flag is 0) or 0..255 scaled file encoded values
2193 * (if the function must gamma correct them).
2194 */
2195 for (i=val=0; i<cmap_entries; ++i, val += step)
2196 {
2197 /* 'i' is a file value. While this will result in duplicated
2198 * entries for 8-bit non-sRGB encoded files it is necessary to
2199 * have non-gamma corrected values to do tRNS handling.
2200 */
2201 if (i != trans)
2202 png_create_colormap_entry(display, i, val, val, val, 255,
2203 P_FILE/*8-bit with file gamma*/);
2204
2205 /* Else this entry is transparent. The colors don't matter if
2206 * there is an alpha channel (back_alpha == 0), but it does no
2207 * harm to pass them in; the values are not set above so this
2208 * passes in white.
2209 *
2210 * NOTE: this preserves the full precision of the application
2211 * supplied background color when it is used.
2212 */
2213 else
2214 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2215 back_alpha, output_encoding);
2216 }
2217
2218 /* We need libpng to preserve the original encoding. */
2219 data_encoding = P_FILE;
2220
2221 /* The rows from libpng, while technically gray values, are now also
2222 * color-map indices; however, they may need to be expanded to 1
2223 * byte per pixel. This is what png_set_packing does (i.e., it
2224 * unpacks the bit values into bytes.)
2225 */
2226 if (png_ptr->bit_depth < 8)
2227 png_set_packing(png_ptr);
2228 }
2229
2230 else /* bit depth is 16 */
2231 {
2232 /* The 16-bit input values can be converted directly to 8-bit gamma
2233 * encoded values; however, if a tRNS chunk is present 257 color-map
2234 * entries are required. This means that the extra entry requires
2235 * special processing; add an alpha channel, sacrifice gray level
2236 * 254 and convert transparent (alpha==0) entries to that.
2237 *
2238 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2239 * same time to minimize quality loss. If a tRNS chunk is present
2240 * this means libpng must handle it too; otherwise it is impossible
2241 * to do the exact match on the 16-bit value.
2242 *
2243 * If the output has no alpha channel *and* the background color is
2244 * gray then it is possible to let libpng handle the substitution by
2245 * ensuring that the corresponding gray level matches the background
2246 * color exactly.
2247 */
2248 data_encoding = P_sRGB;
2249
2250 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2251 png_error(png_ptr, "gray[16] color-map: too few entries");
2252
2253 cmap_entries = make_gray_colormap(display);
2254
2255 if (png_ptr->num_trans > 0)
2256 {
2257 unsigned int back_alpha;
2258
2259 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2260 back_alpha = 0;
2261
2262 else
2263 {
2264 if (back_r == back_g && back_g == back_b)
2265 {
2266 /* Background is gray; no special processing will be
2267 * required.
2268 */
2269 png_color_16 c;
2270 png_uint_32 gray = back_g;
2271
2272 if (output_encoding == P_LINEAR)
2273 {
2274 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2275
2276 /* And make sure the corresponding palette entry
2277 * matches.
2278 */
2279 png_create_colormap_entry(display, gray, back_g, back_g,
2280 back_g, 65535, P_LINEAR);
2281 }
2282
2283 /* The background passed to libpng, however, must be the
2284 * sRGB value.
2285 */
2286 c.index = 0; /*unused*/
2287 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2288
2289 /* NOTE: does this work without expanding tRNS to alpha?
2290 * It should be the color->gray case below apparently
2291 * doesn't.
2292 */
2293 png_set_background_fixed(png_ptr, &c,
2294 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2295 0/*gamma: not used*/);
2296
2297 output_processing = PNG_CMAP_NONE;
2298 break;
2299 }
2300 #ifdef __COVERITY__
2301 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2302 * here.
2303 */
2304 back_alpha = 255;
2305 #else
2306 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2307 #endif
2308 }
2309
2310 /* output_processing means that the libpng-processed row will be
2311 * 8-bit GA and it has to be processing to single byte color-map
2312 * values. Entry 254 is replaced by either a completely
2313 * transparent entry or by the background color at full
2314 * precision (and the background color is not a simple gray
2315 * level in this case.)
2316 */
2317 expand_tRNS = 1;
2318 output_processing = PNG_CMAP_TRANS;
2319 background_index = 254;
2320
2321 /* And set (overwrite) color-map entry 254 to the actual
2322 * background color at full precision.
2323 */
2324 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2325 back_alpha, output_encoding);
2326 }
2327
2328 else
2329 output_processing = PNG_CMAP_NONE;
2330 }
2331 break;
2332
2333 case PNG_COLOR_TYPE_GRAY_ALPHA:
2334 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2335 * of 65536 combinations. If, however, the alpha channel is to be
2336 * removed there are only 256 possibilities if the background is gray.
2337 * (Otherwise there is a subset of the 65536 possibilities defined by
2338 * the triangle between black, white and the background color.)
2339 *
2340 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2341 * worry about tRNS matching - tRNS is ignored if there is an alpha
2342 * channel.
2343 */
2344 data_encoding = P_sRGB;
2345
2346 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2347 {
2348 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2349 png_error(png_ptr, "gray+alpha color-map: too few entries");
2350
2351 cmap_entries = make_ga_colormap(display);
2352
2353 background_index = PNG_CMAP_GA_BACKGROUND;
2354 output_processing = PNG_CMAP_GA;
2355 }
2356
2357 else /* alpha is removed */
2358 {
2359 /* Alpha must be removed as the PNG data is processed when the
2360 * background is a color because the G and A channels are
2361 * independent and the vector addition (non-parallel vectors) is a
2362 * 2-D problem.
2363 *
2364 * This can be reduced to the same algorithm as above by making a
2365 * colormap containing gray levels (for the opaque grays), a
2366 * background entry (for a transparent pixel) and a set of four six
2367 * level color values, one set for each intermediate alpha value.
2368 * See the comments in make_ga_colormap for how this works in the
2369 * per-pixel processing.
2370 *
2371 * If the background is gray, however, we only need a 256 entry gray
2372 * level color map. It is sufficient to make the entry generated
2373 * for the background color be exactly the color specified.
2374 */
2375 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2376 (back_r == back_g && back_g == back_b))
2377 {
2378 /* Background is gray; no special processing will be required. */
2379 png_color_16 c;
2380 png_uint_32 gray = back_g;
2381
2382 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2383 png_error(png_ptr, "gray-alpha color-map: too few entries");
2384
2385 cmap_entries = make_gray_colormap(display);
2386
2387 if (output_encoding == P_LINEAR)
2388 {
2389 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2390
2391 /* And make sure the corresponding palette entry matches. */
2392 png_create_colormap_entry(display, gray, back_g, back_g,
2393 back_g, 65535, P_LINEAR);
2394 }
2395
2396 /* The background passed to libpng, however, must be the sRGB
2397 * value.
2398 */
2399 c.index = 0; /*unused*/
2400 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2401
2402 png_set_background_fixed(png_ptr, &c,
2403 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2404 0/*gamma: not used*/);
2405
2406 output_processing = PNG_CMAP_NONE;
2407 }
2408
2409 else
2410 {
2411 png_uint_32 i, a;
2412
2413 /* This is the same as png_make_ga_colormap, above, except that
2414 * the entries are all opaque.
2415 */
2416 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2417 png_error(png_ptr, "ga-alpha color-map: too few entries");
2418
2419 i = 0;
2420 while (i < 231)
2421 {
2422 png_uint_32 gray = (i * 256 + 115) / 231;
2423 png_create_colormap_entry(display, i++, gray, gray, gray,
2424 255, P_sRGB);
2425 }
2426
2427 /* NOTE: this preserves the full precision of the application
2428 * background color.
2429 */
2430 background_index = i;
2431 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2432 #ifdef __COVERITY__
2433 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2434 * here.
2435 */ 255U,
2436 #else
2437 output_encoding == P_LINEAR ? 65535U : 255U,
2438 #endif
2439 output_encoding);
2440
2441 /* For non-opaque input composite on the sRGB background - this
2442 * requires inverting the encoding for each component. The input
2443 * is still converted to the sRGB encoding because this is a
2444 * reasonable approximate to the logarithmic curve of human
2445 * visual sensitivity, at least over the narrow range which PNG
2446 * represents. Consequently 'G' is always sRGB encoded, while
2447 * 'A' is linear. We need the linear background colors.
2448 */
2449 if (output_encoding == P_sRGB) /* else already linear */
2450 {
2451 /* This may produce a value not exactly matching the
2452 * background, but that's ok because these numbers are only
2453 * used when alpha != 0
2454 */
2455 back_r = png_sRGB_table[back_r];
2456 back_g = png_sRGB_table[back_g];
2457 back_b = png_sRGB_table[back_b];
2458 }
2459
2460 for (a=1; a<5; ++a)
2461 {
2462 unsigned int g;
2463
2464 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2465 * by an 8-bit alpha value (0..255).
2466 */
2467 png_uint_32 alpha = 51 * a;
2468 png_uint_32 back_rx = (255-alpha) * back_r;
2469 png_uint_32 back_gx = (255-alpha) * back_g;
2470 png_uint_32 back_bx = (255-alpha) * back_b;
2471
2472 for (g=0; g<6; ++g)
2473 {
2474 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2475
2476 png_create_colormap_entry(display, i++,
2477 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2478 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2479 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2480 }
2481 }
2482
2483 cmap_entries = i;
2484 output_processing = PNG_CMAP_GA;
2485 }
2486 }
2487 break;
2488
2489 case PNG_COLOR_TYPE_RGB:
2490 case PNG_COLOR_TYPE_RGB_ALPHA:
2491 /* Exclude the case where the output is gray; we can always handle this
2492 * with the cases above.
2493 */
2494 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2495 {
2496 /* The color-map will be grayscale, so we may as well convert the
2497 * input RGB values to a simple grayscale and use the grayscale
2498 * code above.
2499 *
2500 * NOTE: calling this apparently damages the recognition of the
2501 * transparent color in background color handling; call
2502 * png_set_tRNS_to_alpha before png_set_background_fixed.
2503 */
2504 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2505 -1);
2506 data_encoding = P_sRGB;
2507
2508 /* The output will now be one or two 8-bit gray or gray+alpha
2509 * channels. The more complex case arises when the input has alpha.
2510 */
2511 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2512 png_ptr->num_trans > 0) &&
2513 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2514 {
2515 /* Both input and output have an alpha channel, so no background
2516 * processing is required; just map the GA bytes to the right
2517 * color-map entry.
2518 */
2519 expand_tRNS = 1;
2520
2521 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2522 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2523
2524 cmap_entries = make_ga_colormap(display);
2525 background_index = PNG_CMAP_GA_BACKGROUND;
2526 output_processing = PNG_CMAP_GA;
2527 }
2528
2529 else
2530 {
2531 /* Either the input or the output has no alpha channel, so there
2532 * will be no non-opaque pixels in the color-map; it will just be
2533 * grayscale.
2534 */
2535 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2536 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2537
2538 /* Ideally this code would use libpng to do the gamma correction,
2539 * but if an input alpha channel is to be removed we will hit the
2540 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2541 * correction bug). Fix this by dropping the gamma correction in
2542 * this case and doing it in the palette; this will result in
2543 * duplicate palette entries, but that's better than the
2544 * alternative of double gamma correction.
2545 */
2546 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2547 png_ptr->num_trans > 0) &&
2548 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2549 {
2550 cmap_entries = make_gray_file_colormap(display);
2551 data_encoding = P_FILE;
2552 }
2553
2554 else
2555 cmap_entries = make_gray_colormap(display);
2556
2557 /* But if the input has alpha or transparency it must be removed
2558 */
2559 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2560 png_ptr->num_trans > 0)
2561 {
2562 png_color_16 c;
2563 png_uint_32 gray = back_g;
2564
2565 /* We need to ensure that the application background exists in
2566 * the colormap and that completely transparent pixels map to
2567 * it. Achieve this simply by ensuring that the entry
2568 * selected for the background really is the background color.
2569 */
2570 if (data_encoding == P_FILE) /* from the fixup above */
2571 {
2572 /* The app supplied a gray which is in output_encoding, we
2573 * need to convert it to a value of the input (P_FILE)
2574 * encoding then set this palette entry to the required
2575 * output encoding.
2576 */
2577 if (output_encoding == P_sRGB)
2578 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2579
2580 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2581 png_ptr->colorspace.gamma)); /* now P_FILE */
2582
2583 /* And make sure the corresponding palette entry contains
2584 * exactly the required sRGB value.
2585 */
2586 png_create_colormap_entry(display, gray, back_g, back_g,
2587 back_g, 0/*unused*/, output_encoding);
2588 }
2589
2590 else if (output_encoding == P_LINEAR)
2591 {
2592 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2593
2594 /* And make sure the corresponding palette entry matches.
2595 */
2596 png_create_colormap_entry(display, gray, back_g, back_g,
2597 back_g, 0/*unused*/, P_LINEAR);
2598 }
2599
2600 /* The background passed to libpng, however, must be the
2601 * output (normally sRGB) value.
2602 */
2603 c.index = 0; /*unused*/
2604 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2605
2606 /* NOTE: the following is apparently a bug in libpng. Without
2607 * it the transparent color recognition in
2608 * png_set_background_fixed seems to go wrong.
2609 */
2610 expand_tRNS = 1;
2611 png_set_background_fixed(png_ptr, &c,
2612 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2613 0/*gamma: not used*/);
2614 }
2615
2616 output_processing = PNG_CMAP_NONE;
2617 }
2618 }
2619
2620 else /* output is color */
2621 {
2622 /* We could use png_quantize here so long as there is no transparent
2623 * color or alpha; png_quantize ignores alpha. Easier overall just
2624 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2625 * Consequently we always want libpng to produce sRGB data.
2626 */
2627 data_encoding = P_sRGB;
2628
2629 /* Is there any transparency or alpha? */
2630 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2631 png_ptr->num_trans > 0)
2632 {
2633 /* Is there alpha in the output too? If so all four channels are
2634 * processed into a special RGB cube with alpha support.
2635 */
2636 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2637 {
2638 png_uint_32 r;
2639
2640 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2641 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2642
2643 cmap_entries = make_rgb_colormap(display);
2644
2645 /* Add a transparent entry. */
2646 png_create_colormap_entry(display, cmap_entries, 255, 255,
2647 255, 0, P_sRGB);
2648
2649 /* This is stored as the background index for the processing
2650 * algorithm.
2651 */
2652 background_index = cmap_entries++;
2653
2654 /* Add 27 r,g,b entries each with alpha 0.5. */
2655 for (r=0; r<256; r = (r << 1) | 0x7f)
2656 {
2657 png_uint_32 g;
2658
2659 for (g=0; g<256; g = (g << 1) | 0x7f)
2660 {
2661 png_uint_32 b;
2662
2663 /* This generates components with the values 0, 127 and
2664 * 255
2665 */
2666 for (b=0; b<256; b = (b << 1) | 0x7f)
2667 png_create_colormap_entry(display, cmap_entries++,
2668 r, g, b, 128, P_sRGB);
2669 }
2670 }
2671
2672 expand_tRNS = 1;
2673 output_processing = PNG_CMAP_RGB_ALPHA;
2674 }
2675
2676 else
2677 {
2678 /* Alpha/transparency must be removed. The background must
2679 * exist in the color map (achieved by setting adding it after
2680 * the 666 color-map). If the standard processing code will
2681 * pick up this entry automatically that's all that is
2682 * required; libpng can be called to do the background
2683 * processing.
2684 */
2685 unsigned int sample_size =
2686 PNG_IMAGE_SAMPLE_SIZE(output_format);
2687 png_uint_32 r, g, b; /* sRGB background */
2688
2689 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2690 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2691
2692 cmap_entries = make_rgb_colormap(display);
2693
2694 png_create_colormap_entry(display, cmap_entries, back_r,
2695 back_g, back_b, 0/*unused*/, output_encoding);
2696
2697 if (output_encoding == P_LINEAR)
2698 {
2699 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2700 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2701 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2702 }
2703
2704 else
2705 {
2706 r = back_r;
2707 g = back_g;
2708 b = back_g;
2709 }
2710
2711 /* Compare the newly-created color-map entry with the one the
2712 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2713 * match, add the new one and set this as the background
2714 * index.
2715 */
2716 if (memcmp((png_const_bytep)display->colormap +
2717 sample_size * cmap_entries,
2718 (png_const_bytep)display->colormap +
2719 sample_size * PNG_RGB_INDEX(r,g,b),
2720 sample_size) != 0)
2721 {
2722 /* The background color must be added. */
2723 background_index = cmap_entries++;
2724
2725 /* Add 27 r,g,b entries each with created by composing with
2726 * the background at alpha 0.5.
2727 */
2728 for (r=0; r<256; r = (r << 1) | 0x7f)
2729 {
2730 for (g=0; g<256; g = (g << 1) | 0x7f)
2731 {
2732 /* This generates components with the values 0, 127
2733 * and 255
2734 */
2735 for (b=0; b<256; b = (b << 1) | 0x7f)
2736 png_create_colormap_entry(display, cmap_entries++,
2737 png_colormap_compose(display, r, P_sRGB, 128,
2738 back_r, output_encoding),
2739 png_colormap_compose(display, g, P_sRGB, 128,
2740 back_g, output_encoding),
2741 png_colormap_compose(display, b, P_sRGB, 128,
2742 back_b, output_encoding),
2743 0/*unused*/, output_encoding);
2744 }
2745 }
2746
2747 expand_tRNS = 1;
2748 output_processing = PNG_CMAP_RGB_ALPHA;
2749 }
2750
2751 else /* background color is in the standard color-map */
2752 {
2753 png_color_16 c;
2754
2755 c.index = 0; /*unused*/
2756 c.red = (png_uint_16)back_r;
2757 c.gray = c.green = (png_uint_16)back_g;
2758 c.blue = (png_uint_16)back_b;
2759
2760 png_set_background_fixed(png_ptr, &c,
2761 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2762 0/*gamma: not used*/);
2763
2764 output_processing = PNG_CMAP_RGB;
2765 }
2766 }
2767 }
2768
2769 else /* no alpha or transparency in the input */
2770 {
2771 /* Alpha in the output is irrelevant, simply map the opaque input
2772 * pixels to the 6x6x6 color-map.
2773 */
2774 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2775 png_error(png_ptr, "rgb color-map: too few entries");
2776
2777 cmap_entries = make_rgb_colormap(display);
2778 output_processing = PNG_CMAP_RGB;
2779 }
2780 }
2781 break;
2782
2783 case PNG_COLOR_TYPE_PALETTE:
2784 /* It's already got a color-map. It may be necessary to eliminate the
2785 * tRNS entries though.
2786 */
2787 {
2788 unsigned int num_trans = png_ptr->num_trans;
2789 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2790 png_const_colorp colormap = png_ptr->palette;
2791 const int do_background = trans != NULL &&
2792 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2793 unsigned int i;
2794
2795 /* Just in case: */
2796 if (trans == NULL)
2797 num_trans = 0;
2798
2799 output_processing = PNG_CMAP_NONE;
2800 data_encoding = P_FILE; /* Don't change from color-map indices */
2801 cmap_entries = png_ptr->num_palette;
2802 if (cmap_entries > 256)
2803 cmap_entries = 256;
2804
2805 if (cmap_entries > image->colormap_entries)
2806 png_error(png_ptr, "palette color-map: too few entries");
2807
2808 for (i=0; i < cmap_entries; ++i)
2809 {
2810 if (do_background != 0 && i < num_trans && trans[i] < 255)
2811 {
2812 if (trans[i] == 0)
2813 png_create_colormap_entry(display, i, back_r, back_g,
2814 back_b, 0, output_encoding);
2815
2816 else
2817 {
2818 /* Must compose the PNG file color in the color-map entry
2819 * on the sRGB color in 'back'.
2820 */
2821 png_create_colormap_entry(display, i,
2822 png_colormap_compose(display, colormap[i].red, P_FILE,
2823 trans[i], back_r, output_encoding),
2824 png_colormap_compose(display, colormap[i].green, P_FILE,
2825 trans[i], back_g, output_encoding),
2826 png_colormap_compose(display, colormap[i].blue, P_FILE,
2827 trans[i], back_b, output_encoding),
2828 output_encoding == P_LINEAR ? trans[i] * 257U :
2829 trans[i],
2830 output_encoding);
2831 }
2832 }
2833
2834 else
2835 png_create_colormap_entry(display, i, colormap[i].red,
2836 colormap[i].green, colormap[i].blue,
2837 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2838 }
2839
2840 /* The PNG data may have indices packed in fewer than 8 bits, it
2841 * must be expanded if so.
2842 */
2843 if (png_ptr->bit_depth < 8)
2844 png_set_packing(png_ptr);
2845 }
2846 break;
2847
2848 default:
2849 png_error(png_ptr, "invalid PNG color type");
2850 /*NOT REACHED*/
2851 }
2852
2853 /* Now deal with the output processing */
2854 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2855 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2856 png_set_tRNS_to_alpha(png_ptr);
2857
2858 switch (data_encoding)
2859 {
2860 case P_sRGB:
2861 /* Change to 8-bit sRGB */
2862 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2863 /* FALL THROUGH */
2864
2865 case P_FILE:
2866 if (png_ptr->bit_depth > 8)
2867 png_set_scale_16(png_ptr);
2868 break;
2869
2870 #ifdef __GNUC__
2871 default:
2872 png_error(png_ptr, "bad data option (internal error)");
2873 #endif
2874 }
2875
2876 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2877 png_error(png_ptr, "color map overflow (BAD internal error)");
2878
2879 image->colormap_entries = cmap_entries;
2880
2881 /* Double check using the recorded background index */
2882 switch (output_processing)
2883 {
2884 case PNG_CMAP_NONE:
2885 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2886 goto bad_background;
2887 break;
2888
2889 case PNG_CMAP_GA:
2890 if (background_index != PNG_CMAP_GA_BACKGROUND)
2891 goto bad_background;
2892 break;
2893
2894 case PNG_CMAP_TRANS:
2895 if (background_index >= cmap_entries ||
2896 background_index != PNG_CMAP_TRANS_BACKGROUND)
2897 goto bad_background;
2898 break;
2899
2900 case PNG_CMAP_RGB:
2901 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2902 goto bad_background;
2903 break;
2904
2905 case PNG_CMAP_RGB_ALPHA:
2906 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2907 goto bad_background;
2908 break;
2909
2910 default:
2911 png_error(png_ptr, "bad processing option (internal error)");
2912
2913 bad_background:
2914 png_error(png_ptr, "bad background index (internal error)");
2915 }
2916
2917 display->colormap_processing = output_processing;
2918
2919 return 1/*ok*/;
2920 }
2921
2922 /* The final part of the color-map read called from png_image_finish_read. */
2923 static int
png_image_read_and_map(png_voidp argument)2924 png_image_read_and_map(png_voidp argument)
2925 {
2926 png_image_read_control *display = png_voidcast(png_image_read_control*,
2927 argument);
2928 png_imagep image = display->image;
2929 png_structrp png_ptr = image->opaque->png_ptr;
2930 int passes;
2931
2932 /* Called when the libpng data must be transformed into the color-mapped
2933 * form. There is a local row buffer in display->local and this routine must
2934 * do the interlace handling.
2935 */
2936 switch (png_ptr->interlaced)
2937 {
2938 case PNG_INTERLACE_NONE:
2939 passes = 1;
2940 break;
2941
2942 case PNG_INTERLACE_ADAM7:
2943 passes = PNG_INTERLACE_ADAM7_PASSES;
2944 break;
2945
2946 default:
2947 png_error(png_ptr, "unknown interlace type");
2948 }
2949
2950 {
2951 png_uint_32 height = image->height;
2952 png_uint_32 width = image->width;
2953 int proc = display->colormap_processing;
2954 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2955 ptrdiff_t step_row = display->row_bytes;
2956 int pass;
2957
2958 for (pass = 0; pass < passes; ++pass)
2959 {
2960 unsigned int startx, stepx, stepy;
2961 png_uint_32 y;
2962
2963 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2964 {
2965 /* The row may be empty for a short image: */
2966 if (PNG_PASS_COLS(width, pass) == 0)
2967 continue;
2968
2969 startx = PNG_PASS_START_COL(pass);
2970 stepx = PNG_PASS_COL_OFFSET(pass);
2971 y = PNG_PASS_START_ROW(pass);
2972 stepy = PNG_PASS_ROW_OFFSET(pass);
2973 }
2974
2975 else
2976 {
2977 y = 0;
2978 startx = 0;
2979 stepx = stepy = 1;
2980 }
2981
2982 for (; y<height; y += stepy)
2983 {
2984 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
2985 png_bytep outrow = first_row + y * step_row;
2986 png_const_bytep end_row = outrow + width;
2987
2988 /* Read read the libpng data into the temporary buffer. */
2989 png_read_row(png_ptr, inrow, NULL);
2990
2991 /* Now process the row according to the processing option, note
2992 * that the caller verifies that the format of the libpng output
2993 * data is as required.
2994 */
2995 outrow += startx;
2996 switch (proc)
2997 {
2998 case PNG_CMAP_GA:
2999 for (; outrow < end_row; outrow += stepx)
3000 {
3001 /* The data is always in the PNG order */
3002 unsigned int gray = *inrow++;
3003 unsigned int alpha = *inrow++;
3004 unsigned int entry;
3005
3006 /* NOTE: this code is copied as a comment in
3007 * make_ga_colormap above. Please update the
3008 * comment if you change this code!
3009 */
3010 if (alpha > 229) /* opaque */
3011 {
3012 entry = (231 * gray + 128) >> 8;
3013 }
3014 else if (alpha < 26) /* transparent */
3015 {
3016 entry = 231;
3017 }
3018 else /* partially opaque */
3019 {
3020 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3021 }
3022
3023 *outrow = (png_byte)entry;
3024 }
3025 break;
3026
3027 case PNG_CMAP_TRANS:
3028 for (; outrow < end_row; outrow += stepx)
3029 {
3030 png_byte gray = *inrow++;
3031 png_byte alpha = *inrow++;
3032
3033 if (alpha == 0)
3034 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3035
3036 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3037 *outrow = gray;
3038
3039 else
3040 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3041 }
3042 break;
3043
3044 case PNG_CMAP_RGB:
3045 for (; outrow < end_row; outrow += stepx)
3046 {
3047 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3048 inrow += 3;
3049 }
3050 break;
3051
3052 case PNG_CMAP_RGB_ALPHA:
3053 for (; outrow < end_row; outrow += stepx)
3054 {
3055 unsigned int alpha = inrow[3];
3056
3057 /* Because the alpha entries only hold alpha==0.5 values
3058 * split the processing at alpha==0.25 (64) and 0.75
3059 * (196).
3060 */
3061
3062 if (alpha >= 196)
3063 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3064 inrow[2]);
3065
3066 else if (alpha < 64)
3067 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3068
3069 else
3070 {
3071 /* Likewise there are three entries for each of r, g
3072 * and b. We could select the entry by popcount on
3073 * the top two bits on those architectures that
3074 * support it, this is what the code below does,
3075 * crudely.
3076 */
3077 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3078
3079 /* Here are how the values map:
3080 *
3081 * 0x00 .. 0x3f -> 0
3082 * 0x40 .. 0xbf -> 1
3083 * 0xc0 .. 0xff -> 2
3084 *
3085 * So, as above with the explicit alpha checks, the
3086 * breakpoints are at 64 and 196.
3087 */
3088 if (inrow[0] & 0x80) back_i += 9; /* red */
3089 if (inrow[0] & 0x40) back_i += 9;
3090 if (inrow[0] & 0x80) back_i += 3; /* green */
3091 if (inrow[0] & 0x40) back_i += 3;
3092 if (inrow[0] & 0x80) back_i += 1; /* blue */
3093 if (inrow[0] & 0x40) back_i += 1;
3094
3095 *outrow = (png_byte)back_i;
3096 }
3097
3098 inrow += 4;
3099 }
3100 break;
3101
3102 default:
3103 break;
3104 }
3105 }
3106 }
3107 }
3108
3109 return 1;
3110 }
3111
3112 static int
png_image_read_colormapped(png_voidp argument)3113 png_image_read_colormapped(png_voidp argument)
3114 {
3115 png_image_read_control *display = png_voidcast(png_image_read_control*,
3116 argument);
3117 png_imagep image = display->image;
3118 png_controlp control = image->opaque;
3119 png_structrp png_ptr = control->png_ptr;
3120 png_inforp info_ptr = control->info_ptr;
3121
3122 int passes = 0; /* As a flag */
3123
3124 PNG_SKIP_CHUNKS(png_ptr);
3125
3126 /* Update the 'info' structure and make sure the result is as required; first
3127 * make sure to turn on the interlace handling if it will be required
3128 * (because it can't be turned on *after* the call to png_read_update_info!)
3129 */
3130 if (display->colormap_processing == PNG_CMAP_NONE)
3131 passes = png_set_interlace_handling(png_ptr);
3132
3133 png_read_update_info(png_ptr, info_ptr);
3134
3135 /* The expected output can be deduced from the colormap_processing option. */
3136 switch (display->colormap_processing)
3137 {
3138 case PNG_CMAP_NONE:
3139 /* Output must be one channel and one byte per pixel, the output
3140 * encoding can be anything.
3141 */
3142 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3143 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3144 info_ptr->bit_depth == 8)
3145 break;
3146
3147 goto bad_output;
3148
3149 case PNG_CMAP_TRANS:
3150 case PNG_CMAP_GA:
3151 /* Output must be two channels and the 'G' one must be sRGB, the latter
3152 * can be checked with an exact number because it should have been set
3153 * to this number above!
3154 */
3155 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3156 info_ptr->bit_depth == 8 &&
3157 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3158 image->colormap_entries == 256)
3159 break;
3160
3161 goto bad_output;
3162
3163 case PNG_CMAP_RGB:
3164 /* Output must be 8-bit sRGB encoded RGB */
3165 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3166 info_ptr->bit_depth == 8 &&
3167 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3168 image->colormap_entries == 216)
3169 break;
3170
3171 goto bad_output;
3172
3173 case PNG_CMAP_RGB_ALPHA:
3174 /* Output must be 8-bit sRGB encoded RGBA */
3175 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3176 info_ptr->bit_depth == 8 &&
3177 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3178 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3179 break;
3180
3181 /* goto bad_output; */
3182 /* FALL THROUGH */
3183
3184 default:
3185 bad_output:
3186 png_error(png_ptr, "bad color-map processing (internal error)");
3187 }
3188
3189 /* Now read the rows. Do this here if it is possible to read directly into
3190 * the output buffer, otherwise allocate a local row buffer of the maximum
3191 * size libpng requires and call the relevant processing routine safely.
3192 */
3193 {
3194 png_voidp first_row = display->buffer;
3195 ptrdiff_t row_bytes = display->row_stride;
3196
3197 /* The following expression is designed to work correctly whether it gives
3198 * a signed or an unsigned result.
3199 */
3200 if (row_bytes < 0)
3201 {
3202 char *ptr = png_voidcast(char*, first_row);
3203 ptr += (image->height-1) * (-row_bytes);
3204 first_row = png_voidcast(png_voidp, ptr);
3205 }
3206
3207 display->first_row = first_row;
3208 display->row_bytes = row_bytes;
3209 }
3210
3211 if (passes == 0)
3212 {
3213 int result;
3214 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3215
3216 display->local_row = row;
3217 result = png_safe_execute(image, png_image_read_and_map, display);
3218 display->local_row = NULL;
3219 png_free(png_ptr, row);
3220
3221 return result;
3222 }
3223
3224 else
3225 {
3226 png_alloc_size_t row_bytes = display->row_bytes;
3227
3228 while (--passes >= 0)
3229 {
3230 png_uint_32 y = image->height;
3231 png_bytep row = png_voidcast(png_bytep, display->first_row);
3232
3233 while (y-- > 0)
3234 {
3235 png_read_row(png_ptr, row, NULL);
3236 row += row_bytes;
3237 }
3238 }
3239
3240 return 1;
3241 }
3242 }
3243
3244 /* Just the row reading part of png_image_read. */
3245 static int
png_image_read_composite(png_voidp argument)3246 png_image_read_composite(png_voidp argument)
3247 {
3248 png_image_read_control *display = png_voidcast(png_image_read_control*,
3249 argument);
3250 png_imagep image = display->image;
3251 png_structrp png_ptr = image->opaque->png_ptr;
3252 int passes;
3253
3254 switch (png_ptr->interlaced)
3255 {
3256 case PNG_INTERLACE_NONE:
3257 passes = 1;
3258 break;
3259
3260 case PNG_INTERLACE_ADAM7:
3261 passes = PNG_INTERLACE_ADAM7_PASSES;
3262 break;
3263
3264 default:
3265 png_error(png_ptr, "unknown interlace type");
3266 }
3267
3268 {
3269 png_uint_32 height = image->height;
3270 png_uint_32 width = image->width;
3271 ptrdiff_t step_row = display->row_bytes;
3272 unsigned int channels =
3273 (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ? 3 : 1;
3274 int pass;
3275
3276 for (pass = 0; pass < passes; ++pass)
3277 {
3278 unsigned int startx, stepx, stepy;
3279 png_uint_32 y;
3280
3281 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3282 {
3283 /* The row may be empty for a short image: */
3284 if (PNG_PASS_COLS(width, pass) == 0)
3285 continue;
3286
3287 startx = PNG_PASS_START_COL(pass) * channels;
3288 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3289 y = PNG_PASS_START_ROW(pass);
3290 stepy = PNG_PASS_ROW_OFFSET(pass);
3291 }
3292
3293 else
3294 {
3295 y = 0;
3296 startx = 0;
3297 stepx = channels;
3298 stepy = 1;
3299 }
3300
3301 for (; y<height; y += stepy)
3302 {
3303 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3304 png_bytep outrow;
3305 png_const_bytep end_row;
3306
3307 /* Read the row, which is packed: */
3308 png_read_row(png_ptr, inrow, NULL);
3309
3310 outrow = png_voidcast(png_bytep, display->first_row);
3311 outrow += y * step_row;
3312 end_row = outrow + width * channels;
3313
3314 /* Now do the composition on each pixel in this row. */
3315 outrow += startx;
3316 for (; outrow < end_row; outrow += stepx)
3317 {
3318 png_byte alpha = inrow[channels];
3319
3320 if (alpha > 0) /* else no change to the output */
3321 {
3322 unsigned int c;
3323
3324 for (c=0; c<channels; ++c)
3325 {
3326 png_uint_32 component = inrow[c];
3327
3328 if (alpha < 255) /* else just use component */
3329 {
3330 /* This is PNG_OPTIMIZED_ALPHA, the component value
3331 * is a linear 8-bit value. Combine this with the
3332 * current outrow[c] value which is sRGB encoded.
3333 * Arithmetic here is 16-bits to preserve the output
3334 * values correctly.
3335 */
3336 component *= 257*255; /* =65535 */
3337 component += (255-alpha)*png_sRGB_table[outrow[c]];
3338
3339 /* So 'component' is scaled by 255*65535 and is
3340 * therefore appropriate for the sRGB to linear
3341 * conversion table.
3342 */
3343 component = PNG_sRGB_FROM_LINEAR(component);
3344 }
3345
3346 outrow[c] = (png_byte)component;
3347 }
3348 }
3349
3350 inrow += channels+1; /* components and alpha channel */
3351 }
3352 }
3353 }
3354 }
3355
3356 return 1;
3357 }
3358
3359 /* The do_local_background case; called when all the following transforms are to
3360 * be done:
3361 *
3362 * PNG_RGB_TO_GRAY
3363 * PNG_COMPOSITE
3364 * PNG_GAMMA
3365 *
3366 * This is a work-around for the fact that both the PNG_RGB_TO_GRAY and
3367 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3368 * correction. The fix-up is to prevent the PNG_COMPOSITE operation from
3369 * happening inside libpng, so this routine sees an 8 or 16-bit gray+alpha
3370 * row and handles the removal or pre-multiplication of the alpha channel.
3371 */
3372 static int
png_image_read_background(png_voidp argument)3373 png_image_read_background(png_voidp argument)
3374 {
3375 png_image_read_control *display = png_voidcast(png_image_read_control*,
3376 argument);
3377 png_imagep image = display->image;
3378 png_structrp png_ptr = image->opaque->png_ptr;
3379 png_inforp info_ptr = image->opaque->info_ptr;
3380 png_uint_32 height = image->height;
3381 png_uint_32 width = image->width;
3382 int pass, passes;
3383
3384 /* Double check the convoluted logic below. We expect to get here with
3385 * libpng doing rgb to gray and gamma correction but background processing
3386 * left to the png_image_read_background function. The rows libpng produce
3387 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3388 */
3389 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3390 png_error(png_ptr, "lost rgb to gray");
3391
3392 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3393 png_error(png_ptr, "unexpected compose");
3394
3395 if (png_get_channels(png_ptr, info_ptr) != 2)
3396 png_error(png_ptr, "lost/gained channels");
3397
3398 /* Expect the 8-bit case to always remove the alpha channel */
3399 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3400 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3401 png_error(png_ptr, "unexpected 8-bit transformation");
3402
3403 switch (png_ptr->interlaced)
3404 {
3405 case PNG_INTERLACE_NONE:
3406 passes = 1;
3407 break;
3408
3409 case PNG_INTERLACE_ADAM7:
3410 passes = PNG_INTERLACE_ADAM7_PASSES;
3411 break;
3412
3413 default:
3414 png_error(png_ptr, "unknown interlace type");
3415 }
3416
3417 /* Use direct access to info_ptr here because otherwise the simplified API
3418 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3419 * checking the value after libpng expansions, not the original value in the
3420 * PNG.
3421 */
3422 switch (info_ptr->bit_depth)
3423 {
3424 case 8:
3425 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3426 * to be removed by composing on a background: either the row if
3427 * display->background is NULL or display->background->green if not.
3428 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3429 */
3430 {
3431 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3432 ptrdiff_t step_row = display->row_bytes;
3433
3434 for (pass = 0; pass < passes; ++pass)
3435 {
3436 png_bytep row = png_voidcast(png_bytep,
3437 display->first_row);
3438 unsigned int startx, stepx, stepy;
3439 png_uint_32 y;
3440
3441 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3442 {
3443 /* The row may be empty for a short image: */
3444 if (PNG_PASS_COLS(width, pass) == 0)
3445 continue;
3446
3447 startx = PNG_PASS_START_COL(pass);
3448 stepx = PNG_PASS_COL_OFFSET(pass);
3449 y = PNG_PASS_START_ROW(pass);
3450 stepy = PNG_PASS_ROW_OFFSET(pass);
3451 }
3452
3453 else
3454 {
3455 y = 0;
3456 startx = 0;
3457 stepx = stepy = 1;
3458 }
3459
3460 if (display->background == NULL)
3461 {
3462 for (; y<height; y += stepy)
3463 {
3464 png_bytep inrow = png_voidcast(png_bytep,
3465 display->local_row);
3466 png_bytep outrow = first_row + y * step_row;
3467 png_const_bytep end_row = outrow + width;
3468
3469 /* Read the row, which is packed: */
3470 png_read_row(png_ptr, inrow, NULL);
3471
3472 /* Now do the composition on each pixel in this row. */
3473 outrow += startx;
3474 for (; outrow < end_row; outrow += stepx)
3475 {
3476 png_byte alpha = inrow[1];
3477
3478 if (alpha > 0) /* else no change to the output */
3479 {
3480 png_uint_32 component = inrow[0];
3481
3482 if (alpha < 255) /* else just use component */
3483 {
3484 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3485 * necessary to invert the sRGB transfer
3486 * function and multiply the alpha out.
3487 */
3488 component = png_sRGB_table[component] * alpha;
3489 component += png_sRGB_table[outrow[0]] *
3490 (255-alpha);
3491 component = PNG_sRGB_FROM_LINEAR(component);
3492 }
3493
3494 outrow[0] = (png_byte)component;
3495 }
3496
3497 inrow += 2; /* gray and alpha channel */
3498 }
3499 }
3500 }
3501
3502 else /* constant background value */
3503 {
3504 png_byte background8 = display->background->green;
3505 png_uint_16 background = png_sRGB_table[background8];
3506
3507 for (; y<height; y += stepy)
3508 {
3509 png_bytep inrow = png_voidcast(png_bytep,
3510 display->local_row);
3511 png_bytep outrow = first_row + y * step_row;
3512 png_const_bytep end_row = outrow + width;
3513
3514 /* Read the row, which is packed: */
3515 png_read_row(png_ptr, inrow, NULL);
3516
3517 /* Now do the composition on each pixel in this row. */
3518 outrow += startx;
3519 for (; outrow < end_row; outrow += stepx)
3520 {
3521 png_byte alpha = inrow[1];
3522
3523 if (alpha > 0) /* else use background */
3524 {
3525 png_uint_32 component = inrow[0];
3526
3527 if (alpha < 255) /* else just use component */
3528 {
3529 component = png_sRGB_table[component] * alpha;
3530 component += background * (255-alpha);
3531 component = PNG_sRGB_FROM_LINEAR(component);
3532 }
3533
3534 outrow[0] = (png_byte)component;
3535 }
3536
3537 else
3538 outrow[0] = background8;
3539
3540 inrow += 2; /* gray and alpha channel */
3541 }
3542
3543 row += display->row_bytes;
3544 }
3545 }
3546 }
3547 }
3548 break;
3549
3550 case 16:
3551 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3552 * still be done and, maybe, the alpha channel removed. This code also
3553 * handles the alpha-first option.
3554 */
3555 {
3556 png_uint_16p first_row = png_voidcast(png_uint_16p,
3557 display->first_row);
3558 /* The division by two is safe because the caller passed in a
3559 * stride which was multiplied by 2 (below) to get row_bytes.
3560 */
3561 ptrdiff_t step_row = display->row_bytes / 2;
3562 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
3563 unsigned int outchannels = 1+preserve_alpha;
3564 int swap_alpha = 0;
3565
3566 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3567 if (preserve_alpha != 0 &&
3568 (image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
3569 swap_alpha = 1;
3570 # endif
3571
3572 for (pass = 0; pass < passes; ++pass)
3573 {
3574 unsigned int startx, stepx, stepy;
3575 png_uint_32 y;
3576
3577 /* The 'x' start and step are adjusted to output components here.
3578 */
3579 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3580 {
3581 /* The row may be empty for a short image: */
3582 if (PNG_PASS_COLS(width, pass) == 0)
3583 continue;
3584
3585 startx = PNG_PASS_START_COL(pass) * outchannels;
3586 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3587 y = PNG_PASS_START_ROW(pass);
3588 stepy = PNG_PASS_ROW_OFFSET(pass);
3589 }
3590
3591 else
3592 {
3593 y = 0;
3594 startx = 0;
3595 stepx = outchannels;
3596 stepy = 1;
3597 }
3598
3599 for (; y<height; y += stepy)
3600 {
3601 png_const_uint_16p inrow;
3602 png_uint_16p outrow = first_row + y*step_row;
3603 png_uint_16p end_row = outrow + width * outchannels;
3604
3605 /* Read the row, which is packed: */
3606 png_read_row(png_ptr, png_voidcast(png_bytep,
3607 display->local_row), NULL);
3608 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3609
3610 /* Now do the pre-multiplication on each pixel in this row.
3611 */
3612 outrow += startx;
3613 for (; outrow < end_row; outrow += stepx)
3614 {
3615 png_uint_32 component = inrow[0];
3616 png_uint_16 alpha = inrow[1];
3617
3618 if (alpha > 0) /* else 0 */
3619 {
3620 if (alpha < 65535) /* else just use component */
3621 {
3622 component *= alpha;
3623 component += 32767;
3624 component /= 65535;
3625 }
3626 }
3627
3628 else
3629 component = 0;
3630
3631 outrow[swap_alpha] = (png_uint_16)component;
3632 if (preserve_alpha != 0)
3633 outrow[1 ^ swap_alpha] = alpha;
3634
3635 inrow += 2; /* components and alpha channel */
3636 }
3637 }
3638 }
3639 }
3640 break;
3641
3642 #ifdef __GNUC__
3643 default:
3644 png_error(png_ptr, "unexpected bit depth");
3645 #endif
3646 }
3647
3648 return 1;
3649 }
3650
3651 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3652 static int
png_image_read_direct(png_voidp argument)3653 png_image_read_direct(png_voidp argument)
3654 {
3655 png_image_read_control *display = png_voidcast(png_image_read_control*,
3656 argument);
3657 png_imagep image = display->image;
3658 png_structrp png_ptr = image->opaque->png_ptr;
3659 png_inforp info_ptr = image->opaque->info_ptr;
3660
3661 png_uint_32 format = image->format;
3662 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3663 int do_local_compose = 0;
3664 int do_local_background = 0; /* to avoid double gamma correction bug */
3665 int passes = 0;
3666
3667 /* Add transforms to ensure the correct output format is produced then check
3668 * that the required implementation support is there. Always expand; always
3669 * need 8 bits minimum, no palette and expanded tRNS.
3670 */
3671 png_set_expand(png_ptr);
3672
3673 /* Now check the format to see if it was modified. */
3674 {
3675 png_uint_32 base_format = png_image_format(png_ptr) &
3676 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3677 png_uint_32 change = format ^ base_format;
3678 png_fixed_point output_gamma;
3679 int mode; /* alpha mode */
3680
3681 /* Do this first so that we have a record if rgb to gray is happening. */
3682 if ((change & PNG_FORMAT_FLAG_COLOR) != 0)
3683 {
3684 /* gray<->color transformation required. */
3685 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3686 png_set_gray_to_rgb(png_ptr);
3687
3688 else
3689 {
3690 /* libpng can't do both rgb to gray and
3691 * background/pre-multiplication if there is also significant gamma
3692 * correction, because both operations require linear colors and
3693 * the code only supports one transform doing the gamma correction.
3694 * Handle this by doing the pre-multiplication or background
3695 * operation in this code, if necessary.
3696 *
3697 * TODO: fix this by rewriting pngrtran.c (!)
3698 *
3699 * For the moment (given that fixing this in pngrtran.c is an
3700 * enormous change) 'do_local_background' is used to indicate that
3701 * the problem exists.
3702 */
3703 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3704 do_local_background = 1/*maybe*/;
3705
3706 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3707 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3708 }
3709
3710 change &= ~PNG_FORMAT_FLAG_COLOR;
3711 }
3712
3713 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3714 */
3715 {
3716 png_fixed_point input_gamma_default;
3717
3718 if ((base_format & PNG_FORMAT_FLAG_LINEAR) != 0 &&
3719 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3720 input_gamma_default = PNG_GAMMA_LINEAR;
3721 else
3722 input_gamma_default = PNG_DEFAULT_sRGB;
3723
3724 /* Call png_set_alpha_mode to set the default for the input gamma; the
3725 * output gamma is set by a second call below.
3726 */
3727 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3728 }
3729
3730 if (linear != 0)
3731 {
3732 /* If there *is* an alpha channel in the input it must be multiplied
3733 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3734 */
3735 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3736 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3737
3738 else
3739 mode = PNG_ALPHA_PNG;
3740
3741 output_gamma = PNG_GAMMA_LINEAR;
3742 }
3743
3744 else
3745 {
3746 mode = PNG_ALPHA_PNG;
3747 output_gamma = PNG_DEFAULT_sRGB;
3748 }
3749
3750 /* If 'do_local_background' is set check for the presence of gamma
3751 * correction; this is part of the work-round for the libpng bug
3752 * described above.
3753 *
3754 * TODO: fix libpng and remove this.
3755 */
3756 if (do_local_background != 0)
3757 {
3758 png_fixed_point gtest;
3759
3760 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3761 * gamma correction, the screen gamma hasn't been set on png_struct
3762 * yet; it's set below. png_struct::gamma, however, is set to the
3763 * final value.
3764 */
3765 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3766 PNG_FP_1) != 0 && png_gamma_significant(gtest) == 0)
3767 do_local_background = 0;
3768
3769 else if (mode == PNG_ALPHA_STANDARD)
3770 {
3771 do_local_background = 2/*required*/;
3772 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3773 }
3774
3775 /* else leave as 1 for the checks below */
3776 }
3777
3778 /* If the bit-depth changes then handle that here. */
3779 if ((change & PNG_FORMAT_FLAG_LINEAR) != 0)
3780 {
3781 if (linear != 0 /*16-bit output*/)
3782 png_set_expand_16(png_ptr);
3783
3784 else /* 8-bit output */
3785 png_set_scale_16(png_ptr);
3786
3787 change &= ~PNG_FORMAT_FLAG_LINEAR;
3788 }
3789
3790 /* Now the background/alpha channel changes. */
3791 if ((change & PNG_FORMAT_FLAG_ALPHA) != 0)
3792 {
3793 /* Removing an alpha channel requires composition for the 8-bit
3794 * formats; for the 16-bit it is already done, above, by the
3795 * pre-multiplication and the channel just needs to be stripped.
3796 */
3797 if ((base_format & PNG_FORMAT_FLAG_ALPHA) != 0)
3798 {
3799 /* If RGB->gray is happening the alpha channel must be left and the
3800 * operation completed locally.
3801 *
3802 * TODO: fix libpng and remove this.
3803 */
3804 if (do_local_background != 0)
3805 do_local_background = 2/*required*/;
3806
3807 /* 16-bit output: just remove the channel */
3808 else if (linear != 0) /* compose on black (well, pre-multiply) */
3809 png_set_strip_alpha(png_ptr);
3810
3811 /* 8-bit output: do an appropriate compose */
3812 else if (display->background != NULL)
3813 {
3814 png_color_16 c;
3815
3816 c.index = 0; /*unused*/
3817 c.red = display->background->red;
3818 c.green = display->background->green;
3819 c.blue = display->background->blue;
3820 c.gray = display->background->green;
3821
3822 /* This is always an 8-bit sRGB value, using the 'green' channel
3823 * for gray is much better than calculating the luminance here;
3824 * we can get off-by-one errors in that calculation relative to
3825 * the app expectations and that will show up in transparent
3826 * pixels.
3827 */
3828 png_set_background_fixed(png_ptr, &c,
3829 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3830 0/*gamma: not used*/);
3831 }
3832
3833 else /* compose on row: implemented below. */
3834 {
3835 do_local_compose = 1;
3836 /* This leaves the alpha channel in the output, so it has to be
3837 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3838 * one so the code only has to hack on the pixels that require
3839 * composition.
3840 */
3841 mode = PNG_ALPHA_OPTIMIZED;
3842 }
3843 }
3844
3845 else /* output needs an alpha channel */
3846 {
3847 /* This is tricky because it happens before the swap operation has
3848 * been accomplished; however, the swap does *not* swap the added
3849 * alpha channel (weird API), so it must be added in the correct
3850 * place.
3851 */
3852 png_uint_32 filler; /* opaque filler */
3853 int where;
3854
3855 if (linear != 0)
3856 filler = 65535;
3857
3858 else
3859 filler = 255;
3860
3861 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3862 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3863 {
3864 where = PNG_FILLER_BEFORE;
3865 change &= ~PNG_FORMAT_FLAG_AFIRST;
3866 }
3867
3868 else
3869 #endif
3870 where = PNG_FILLER_AFTER;
3871
3872 png_set_add_alpha(png_ptr, filler, where);
3873 }
3874
3875 /* This stops the (irrelevant) call to swap_alpha below. */
3876 change &= ~PNG_FORMAT_FLAG_ALPHA;
3877 }
3878
3879 /* Now set the alpha mode correctly; this is always done, even if there is
3880 * no alpha channel in either the input or the output because it correctly
3881 * sets the output gamma.
3882 */
3883 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3884
3885 # ifdef PNG_FORMAT_BGR_SUPPORTED
3886 if ((change & PNG_FORMAT_FLAG_BGR) != 0)
3887 {
3888 /* Check only the output format; PNG is never BGR; don't do this if
3889 * the output is gray, but fix up the 'format' value in that case.
3890 */
3891 if ((format & PNG_FORMAT_FLAG_COLOR) != 0)
3892 png_set_bgr(png_ptr);
3893
3894 else
3895 format &= ~PNG_FORMAT_FLAG_BGR;
3896
3897 change &= ~PNG_FORMAT_FLAG_BGR;
3898 }
3899 # endif
3900
3901 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3902 if ((change & PNG_FORMAT_FLAG_AFIRST) != 0)
3903 {
3904 /* Only relevant if there is an alpha channel - it's particularly
3905 * important to handle this correctly because do_local_compose may
3906 * be set above and then libpng will keep the alpha channel for this
3907 * code to remove.
3908 */
3909 if ((format & PNG_FORMAT_FLAG_ALPHA) != 0)
3910 {
3911 /* Disable this if doing a local background,
3912 * TODO: remove this when local background is no longer required.
3913 */
3914 if (do_local_background != 2)
3915 png_set_swap_alpha(png_ptr);
3916 }
3917
3918 else
3919 format &= ~PNG_FORMAT_FLAG_AFIRST;
3920
3921 change &= ~PNG_FORMAT_FLAG_AFIRST;
3922 }
3923 # endif
3924
3925 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3926 * architecture.
3927 */
3928 if (linear != 0)
3929 {
3930 PNG_CONST png_uint_16 le = 0x0001;
3931
3932 if ((*(png_const_bytep) & le) != 0)
3933 png_set_swap(png_ptr);
3934 }
3935
3936 /* If change is not now 0 some transformation is missing - error out. */
3937 if (change != 0)
3938 png_error(png_ptr, "png_read_image: unsupported transformation");
3939 }
3940
3941 PNG_SKIP_CHUNKS(png_ptr);
3942
3943 /* Update the 'info' structure and make sure the result is as required; first
3944 * make sure to turn on the interlace handling if it will be required
3945 * (because it can't be turned on *after* the call to png_read_update_info!)
3946 *
3947 * TODO: remove the do_local_background fixup below.
3948 */
3949 if (do_local_compose == 0 && do_local_background != 2)
3950 passes = png_set_interlace_handling(png_ptr);
3951
3952 png_read_update_info(png_ptr, info_ptr);
3953
3954 {
3955 png_uint_32 info_format = 0;
3956
3957 if ((info_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
3958 info_format |= PNG_FORMAT_FLAG_COLOR;
3959
3960 if ((info_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
3961 {
3962 /* do_local_compose removes this channel below. */
3963 if (do_local_compose == 0)
3964 {
3965 /* do_local_background does the same if required. */
3966 if (do_local_background != 2 ||
3967 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
3968 info_format |= PNG_FORMAT_FLAG_ALPHA;
3969 }
3970 }
3971
3972 else if (do_local_compose != 0) /* internal error */
3973 png_error(png_ptr, "png_image_read: alpha channel lost");
3974
3975 if (info_ptr->bit_depth == 16)
3976 info_format |= PNG_FORMAT_FLAG_LINEAR;
3977
3978 #ifdef PNG_FORMAT_BGR_SUPPORTED
3979 if ((png_ptr->transformations & PNG_BGR) != 0)
3980 info_format |= PNG_FORMAT_FLAG_BGR;
3981 #endif
3982
3983 #ifdef PNG_FORMAT_AFIRST_SUPPORTED
3984 if (do_local_background == 2)
3985 {
3986 if ((format & PNG_FORMAT_FLAG_AFIRST) != 0)
3987 info_format |= PNG_FORMAT_FLAG_AFIRST;
3988 }
3989
3990 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
3991 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
3992 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
3993 {
3994 if (do_local_background == 2)
3995 png_error(png_ptr, "unexpected alpha swap transformation");
3996
3997 info_format |= PNG_FORMAT_FLAG_AFIRST;
3998 }
3999 # endif
4000
4001 /* This is actually an internal error. */
4002 if (info_format != format)
4003 png_error(png_ptr, "png_read_image: invalid transformations");
4004 }
4005
4006 /* Now read the rows. If do_local_compose is set then it is necessary to use
4007 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4008 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4009 * display acts as a flag.
4010 */
4011 {
4012 png_voidp first_row = display->buffer;
4013 ptrdiff_t row_bytes = display->row_stride;
4014
4015 if (linear != 0)
4016 row_bytes *= 2;
4017
4018 /* The following expression is designed to work correctly whether it gives
4019 * a signed or an unsigned result.
4020 */
4021 if (row_bytes < 0)
4022 {
4023 char *ptr = png_voidcast(char*, first_row);
4024 ptr += (image->height-1) * (-row_bytes);
4025 first_row = png_voidcast(png_voidp, ptr);
4026 }
4027
4028 display->first_row = first_row;
4029 display->row_bytes = row_bytes;
4030 }
4031
4032 if (do_local_compose != 0)
4033 {
4034 int result;
4035 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4036
4037 display->local_row = row;
4038 result = png_safe_execute(image, png_image_read_composite, display);
4039 display->local_row = NULL;
4040 png_free(png_ptr, row);
4041
4042 return result;
4043 }
4044
4045 else if (do_local_background == 2)
4046 {
4047 int result;
4048 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4049
4050 display->local_row = row;
4051 result = png_safe_execute(image, png_image_read_background, display);
4052 display->local_row = NULL;
4053 png_free(png_ptr, row);
4054
4055 return result;
4056 }
4057
4058 else
4059 {
4060 png_alloc_size_t row_bytes = display->row_bytes;
4061
4062 while (--passes >= 0)
4063 {
4064 png_uint_32 y = image->height;
4065 png_bytep row = png_voidcast(png_bytep, display->first_row);
4066
4067 while (y-- > 0)
4068 {
4069 png_read_row(png_ptr, row, NULL);
4070 row += row_bytes;
4071 }
4072 }
4073
4074 return 1;
4075 }
4076 }
4077
4078 int PNGAPI
png_image_finish_read(png_imagep image,png_const_colorp background,void * buffer,png_int_32 row_stride,void * colormap)4079 png_image_finish_read(png_imagep image, png_const_colorp background,
4080 void *buffer, png_int_32 row_stride, void *colormap)
4081 {
4082 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4083 {
4084 /* Check for row_stride overflow. This check is not performed on the
4085 * original PNG format because it may not occur in the output PNG format
4086 * and libpng deals with the issues of reading the original.
4087 */
4088 const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
4089
4090 if (image->width <= 0x7FFFFFFFU/channels) /* no overflow */
4091 {
4092 png_uint_32 check;
4093 const png_uint_32 png_row_stride = image->width * channels;
4094
4095 if (row_stride == 0)
4096 row_stride = (png_int_32)/*SAFE*/png_row_stride;
4097
4098 if (row_stride < 0)
4099 check = -row_stride;
4100
4101 else
4102 check = row_stride;
4103
4104 if (image->opaque != NULL && buffer != NULL && check >= png_row_stride)
4105 {
4106 /* Now check for overflow of the image buffer calculation; this
4107 * limits the whole image size to 32 bits for API compatibility with
4108 * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
4109 */
4110 if (image->height <= 0xFFFFFFFF/png_row_stride)
4111 {
4112 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4113 (image->colormap_entries > 0 && colormap != NULL))
4114 {
4115 int result;
4116 png_image_read_control display;
4117
4118 memset(&display, 0, (sizeof display));
4119 display.image = image;
4120 display.buffer = buffer;
4121 display.row_stride = row_stride;
4122 display.colormap = colormap;
4123 display.background = background;
4124 display.local_row = NULL;
4125
4126 /* Choose the correct 'end' routine; for the color-map case
4127 * all the setup has already been done.
4128 */
4129 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) != 0)
4130 result = png_safe_execute(image,
4131 png_image_read_colormap, &display) &&
4132 png_safe_execute(image,
4133 png_image_read_colormapped, &display);
4134
4135 else
4136 result =
4137 png_safe_execute(image,
4138 png_image_read_direct, &display);
4139
4140 png_image_free(image);
4141 return result;
4142 }
4143
4144 else
4145 return png_image_error(image,
4146 "png_image_finish_read[color-map]: no color-map");
4147 }
4148
4149 else
4150 return png_image_error(image,
4151 "png_image_finish_read: image too large");
4152 }
4153
4154 else
4155 return png_image_error(image,
4156 "png_image_finish_read: invalid argument");
4157 }
4158
4159 else
4160 return png_image_error(image,
4161 "png_image_finish_read: row_stride too large");
4162 }
4163
4164 else if (image != NULL)
4165 return png_image_error(image,
4166 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4167
4168 return 0;
4169 }
4170
4171 #endif /* SIMPLIFIED_READ */
4172 #endif /* READ */
4173