1
2 /* pngread.c - read a PNG file
3 *
4 * Last changed in libpng 1.6.10 [March 6, 2014]
5 * Copyright (c) 1998-2014 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 /* PNG_USER_MEM_SUPPORTED */
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_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
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 #ifdef PNG_INDEX_SUPPORTED
78 png_ptr->index = NULL;
79 #endif
80 }
81
82 return png_ptr;
83 }
84
85
86 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
87 /* Read the information before the actual image data. This has been
88 * changed in v0.90 to allow reading a file that already has the magic
89 * bytes read from the stream. You can tell libpng how many bytes have
90 * been read from the beginning of the stream (up to the maximum of 8)
91 * via png_set_sig_bytes(), and we will only check the remaining bytes
92 * here. The application can then have access to the signature bytes we
93 * read if it is determined that this isn't a valid PNG file.
94 */
95 void PNGAPI
png_read_info(png_structrp png_ptr,png_inforp info_ptr)96 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
97 {
98 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
99 int keep;
100 #endif
101
102 png_debug(1, "in png_read_info");
103
104 if (png_ptr == NULL || info_ptr == NULL)
105 return;
106
107 /* Read and check the PNG file signature. */
108 png_read_sig(png_ptr, info_ptr);
109
110 for (;;)
111 {
112 png_uint_32 length = png_read_chunk_header(png_ptr);
113 png_uint_32 chunk_name = png_ptr->chunk_name;
114
115 /* IDAT logic needs to happen here to simplify getting the two flags
116 * right.
117 */
118 if (chunk_name == png_IDAT)
119 {
120 if (!(png_ptr->mode & PNG_HAVE_IHDR))
121 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
122
123 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
124 !(png_ptr->mode & PNG_HAVE_PLTE))
125 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
126
127 else if (png_ptr->mode & PNG_AFTER_IDAT)
128 png_chunk_benign_error(png_ptr, "Too many IDATs found");
129
130 png_ptr->mode |= PNG_HAVE_IDAT;
131 }
132
133 else if (png_ptr->mode & PNG_HAVE_IDAT)
134 png_ptr->mode |= PNG_AFTER_IDAT;
135
136 /* This should be a binary subdivision search or a hash for
137 * matching the chunk name rather than a linear search.
138 */
139 if (chunk_name == png_IHDR)
140 png_handle_IHDR(png_ptr, info_ptr, length);
141
142 else if (chunk_name == png_IEND)
143 png_handle_IEND(png_ptr, info_ptr, length);
144
145 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
146 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
147 {
148 png_handle_unknown(png_ptr, info_ptr, length, keep);
149
150 if (chunk_name == png_PLTE)
151 png_ptr->mode |= PNG_HAVE_PLTE;
152
153 else if (chunk_name == png_IDAT)
154 {
155 png_ptr->idat_size = 0; /* It has been consumed */
156 break;
157 }
158 }
159 #endif
160 else if (chunk_name == png_PLTE)
161 png_handle_PLTE(png_ptr, info_ptr, length);
162
163 else if (chunk_name == png_IDAT)
164 {
165 png_ptr->idat_size = length;
166 break;
167 }
168
169 #ifdef PNG_READ_bKGD_SUPPORTED
170 else if (chunk_name == png_bKGD)
171 png_handle_bKGD(png_ptr, info_ptr, length);
172 #endif
173
174 #ifdef PNG_READ_cHRM_SUPPORTED
175 else if (chunk_name == png_cHRM)
176 png_handle_cHRM(png_ptr, info_ptr, length);
177 #endif
178
179 #ifdef PNG_READ_gAMA_SUPPORTED
180 else if (chunk_name == png_gAMA)
181 png_handle_gAMA(png_ptr, info_ptr, length);
182 #endif
183
184 #ifdef PNG_READ_hIST_SUPPORTED
185 else if (chunk_name == png_hIST)
186 png_handle_hIST(png_ptr, info_ptr, length);
187 #endif
188
189 #ifdef PNG_READ_oFFs_SUPPORTED
190 else if (chunk_name == png_oFFs)
191 png_handle_oFFs(png_ptr, info_ptr, length);
192 #endif
193
194 #ifdef PNG_READ_pCAL_SUPPORTED
195 else if (chunk_name == png_pCAL)
196 png_handle_pCAL(png_ptr, info_ptr, length);
197 #endif
198
199 #ifdef PNG_READ_sCAL_SUPPORTED
200 else if (chunk_name == png_sCAL)
201 png_handle_sCAL(png_ptr, info_ptr, length);
202 #endif
203
204 #ifdef PNG_READ_pHYs_SUPPORTED
205 else if (chunk_name == png_pHYs)
206 png_handle_pHYs(png_ptr, info_ptr, length);
207 #endif
208
209 #ifdef PNG_READ_sBIT_SUPPORTED
210 else if (chunk_name == png_sBIT)
211 png_handle_sBIT(png_ptr, info_ptr, length);
212 #endif
213
214 #ifdef PNG_READ_sRGB_SUPPORTED
215 else if (chunk_name == png_sRGB)
216 png_handle_sRGB(png_ptr, info_ptr, length);
217 #endif
218
219 #ifdef PNG_READ_iCCP_SUPPORTED
220 else if (chunk_name == png_iCCP)
221 png_handle_iCCP(png_ptr, info_ptr, length);
222 #endif
223
224 #ifdef PNG_READ_sPLT_SUPPORTED
225 else if (chunk_name == png_sPLT)
226 png_handle_sPLT(png_ptr, info_ptr, length);
227 #endif
228
229 #ifdef PNG_READ_tEXt_SUPPORTED
230 else if (chunk_name == png_tEXt)
231 png_handle_tEXt(png_ptr, info_ptr, length);
232 #endif
233
234 #ifdef PNG_READ_tIME_SUPPORTED
235 else if (chunk_name == png_tIME)
236 png_handle_tIME(png_ptr, info_ptr, length);
237 #endif
238
239 #ifdef PNG_READ_tRNS_SUPPORTED
240 else if (chunk_name == png_tRNS)
241 png_handle_tRNS(png_ptr, info_ptr, length);
242 #endif
243
244 #ifdef PNG_READ_zTXt_SUPPORTED
245 else if (chunk_name == png_zTXt)
246 png_handle_zTXt(png_ptr, info_ptr, length);
247 #endif
248
249 #ifdef PNG_READ_iTXt_SUPPORTED
250 else if (chunk_name == png_iTXt)
251 png_handle_iTXt(png_ptr, info_ptr, length);
252 #endif
253
254 else
255 png_handle_unknown(png_ptr, info_ptr, length,
256 PNG_HANDLE_CHUNK_AS_DEFAULT);
257 }
258 }
259 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
260
261 /* Optional call to update the users info_ptr structure */
262 void PNGAPI
png_read_update_info(png_structrp png_ptr,png_inforp info_ptr)263 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
264 {
265 png_debug(1, "in png_read_update_info");
266
267 if (png_ptr != NULL)
268 {
269 #ifdef PNG_INDEX_SUPPORTED
270 if (png_ptr->index) {
271 png_read_start_row(png_ptr);
272 }
273 #endif
274 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
275 {
276 png_read_start_row(png_ptr);
277
278 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
279 png_read_transform_info(png_ptr, info_ptr);
280 # else
281 PNG_UNUSED(info_ptr)
282 # endif
283 }
284 #ifndef PNG_INDEX_SUPPORTED
285 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
286 else
287 png_app_error(png_ptr,
288 "png_read_update_info/png_start_read_image: duplicate call");
289 #endif
290 }
291 }
292
293 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
294 /* Initialize palette, background, etc, after transformations
295 * are set, but before any reading takes place. This allows
296 * the user to obtain a gamma-corrected palette, for example.
297 * If the user doesn't call this, we will do it ourselves.
298 */
299 void PNGAPI
png_start_read_image(png_structrp png_ptr)300 png_start_read_image(png_structrp png_ptr)
301 {
302 png_debug(1, "in png_start_read_image");
303
304 if (png_ptr != NULL)
305 {
306 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
307 png_read_start_row(png_ptr);
308
309 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
310 else
311 png_app_error(png_ptr,
312 "png_start_read_image/png_read_update_info: duplicate call");
313 }
314 }
315 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
316
317 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
318 #ifdef PNG_MNG_FEATURES_SUPPORTED
319 /* Undoes intrapixel differencing,
320 * NOTE: this is apparently only supported in the 'sequential' reader.
321 */
322 static void
png_do_read_intrapixel(png_row_infop row_info,png_bytep row)323 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
324 {
325 png_debug(1, "in png_do_read_intrapixel");
326
327 if (
328 (row_info->color_type & PNG_COLOR_MASK_COLOR))
329 {
330 int bytes_per_pixel;
331 png_uint_32 row_width = row_info->width;
332
333 if (row_info->bit_depth == 8)
334 {
335 png_bytep rp;
336 png_uint_32 i;
337
338 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
339 bytes_per_pixel = 3;
340
341 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
342 bytes_per_pixel = 4;
343
344 else
345 return;
346
347 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
348 {
349 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
350 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
351 }
352 }
353 else if (row_info->bit_depth == 16)
354 {
355 png_bytep rp;
356 png_uint_32 i;
357
358 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
359 bytes_per_pixel = 6;
360
361 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
362 bytes_per_pixel = 8;
363
364 else
365 return;
366
367 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
368 {
369 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
370 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
371 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
372 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
373 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
374 *(rp ) = (png_byte)((red >> 8) & 0xff);
375 *(rp + 1) = (png_byte)(red & 0xff);
376 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
377 *(rp + 5) = (png_byte)(blue & 0xff);
378 }
379 }
380 }
381 }
382 #endif /* PNG_MNG_FEATURES_SUPPORTED */
383
384 void PNGAPI
png_read_row(png_structrp png_ptr,png_bytep row,png_bytep dsp_row)385 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
386 {
387 png_row_info row_info;
388
389 if (png_ptr == NULL)
390 return;
391
392 png_debug2(1, "in png_read_row (row %lu, pass %d)",
393 (unsigned long)png_ptr->row_number, png_ptr->pass);
394
395 /* png_read_start_row sets the information (in particular iwidth) for this
396 * interlace pass.
397 */
398 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
399 png_read_start_row(png_ptr);
400
401 /* 1.5.6: row_info moved out of png_struct to a local here. */
402 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
403 row_info.color_type = png_ptr->color_type;
404 row_info.bit_depth = png_ptr->bit_depth;
405 row_info.channels = png_ptr->channels;
406 row_info.pixel_depth = png_ptr->pixel_depth;
407 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
408
409 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
410 {
411 /* Check for transforms that have been set but were defined out */
412 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
413 if (png_ptr->transformations & PNG_INVERT_MONO)
414 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
415 #endif
416
417 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
418 if (png_ptr->transformations & PNG_FILLER)
419 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
420 #endif
421
422 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
423 !defined(PNG_READ_PACKSWAP_SUPPORTED)
424 if (png_ptr->transformations & PNG_PACKSWAP)
425 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
426 #endif
427
428 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
429 if (png_ptr->transformations & PNG_PACK)
430 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
431 #endif
432
433 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
434 if (png_ptr->transformations & PNG_SHIFT)
435 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
436 #endif
437
438 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
439 if (png_ptr->transformations & PNG_BGR)
440 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
441 #endif
442
443 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
444 if (png_ptr->transformations & PNG_SWAP_BYTES)
445 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
446 #endif
447 }
448
449 #ifdef PNG_READ_INTERLACING_SUPPORTED
450 /* If interlaced and we do not need a new row, combine row and return.
451 * Notice that the pixels we have from previous rows have been transformed
452 * already; we can only combine like with like (transformed or
453 * untransformed) and, because of the libpng API for interlaced images, this
454 * means we must transform before de-interlacing.
455 */
456 if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
457 {
458 switch (png_ptr->pass)
459 {
460 case 0:
461 if (png_ptr->row_number & 0x07)
462 {
463 if (dsp_row != NULL)
464 png_combine_row(png_ptr, dsp_row, 1/*display*/);
465 png_read_finish_row(png_ptr);
466 return;
467 }
468 break;
469
470 case 1:
471 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
472 {
473 if (dsp_row != NULL)
474 png_combine_row(png_ptr, dsp_row, 1/*display*/);
475
476 png_read_finish_row(png_ptr);
477 return;
478 }
479 break;
480
481 case 2:
482 if ((png_ptr->row_number & 0x07) != 4)
483 {
484 if (dsp_row != NULL && (png_ptr->row_number & 4))
485 png_combine_row(png_ptr, dsp_row, 1/*display*/);
486
487 png_read_finish_row(png_ptr);
488 return;
489 }
490 break;
491
492 case 3:
493 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
494 {
495 if (dsp_row != NULL)
496 png_combine_row(png_ptr, dsp_row, 1/*display*/);
497
498 png_read_finish_row(png_ptr);
499 return;
500 }
501 break;
502
503 case 4:
504 if ((png_ptr->row_number & 3) != 2)
505 {
506 if (dsp_row != NULL && (png_ptr->row_number & 2))
507 png_combine_row(png_ptr, dsp_row, 1/*display*/);
508
509 png_read_finish_row(png_ptr);
510 return;
511 }
512 break;
513
514 case 5:
515 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
516 {
517 if (dsp_row != NULL)
518 png_combine_row(png_ptr, dsp_row, 1/*display*/);
519
520 png_read_finish_row(png_ptr);
521 return;
522 }
523 break;
524
525 default:
526 case 6:
527 if (!(png_ptr->row_number & 1))
528 {
529 png_read_finish_row(png_ptr);
530 return;
531 }
532 break;
533 }
534 }
535 #endif
536
537 if (!(png_ptr->mode & PNG_HAVE_IDAT))
538 png_error(png_ptr, "Invalid attempt to read row data");
539
540 /* Fill the row with IDAT data: */
541 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
542
543 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
544 {
545 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
546 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
547 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
548 else
549 png_error(png_ptr, "bad adaptive filter value");
550 }
551
552 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
553 * 1.5.6, while the buffer really is this big in current versions of libpng
554 * it may not be in the future, so this was changed just to copy the
555 * interlaced count:
556 */
557 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
558
559 #ifdef PNG_MNG_FEATURES_SUPPORTED
560 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
561 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
562 {
563 /* Intrapixel differencing */
564 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
565 }
566 #endif
567
568 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
569 if (png_ptr->transformations)
570 png_do_read_transformations(png_ptr, &row_info);
571 #endif
572
573 /* The transformed pixel depth should match the depth now in row_info. */
574 if (png_ptr->transformed_pixel_depth == 0)
575 {
576 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
577 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
578 png_error(png_ptr, "sequential row overflow");
579 }
580
581 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
582 png_error(png_ptr, "internal sequential row size calculation error");
583
584 #ifdef PNG_READ_INTERLACING_SUPPORTED
585 /* Blow up interlaced rows to full size */
586 if (png_ptr->interlaced &&
587 (png_ptr->transformations & PNG_INTERLACE))
588 {
589 if (png_ptr->pass < 6)
590 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
591 png_ptr->transformations);
592
593 if (dsp_row != NULL)
594 png_combine_row(png_ptr, dsp_row, 1/*display*/);
595
596 if (row != NULL)
597 png_combine_row(png_ptr, row, 0/*row*/);
598 }
599
600 else
601 #endif
602 {
603 if (row != NULL)
604 png_combine_row(png_ptr, row, -1/*ignored*/);
605
606 if (dsp_row != NULL)
607 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
608 }
609 png_read_finish_row(png_ptr);
610
611 if (png_ptr->read_row_fn != NULL)
612 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
613
614 }
615 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
616
617 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
618 /* Read one or more rows of image data. If the image is interlaced,
619 * and png_set_interlace_handling() has been called, the rows need to
620 * contain the contents of the rows from the previous pass. If the
621 * image has alpha or transparency, and png_handle_alpha()[*] has been
622 * called, the rows contents must be initialized to the contents of the
623 * screen.
624 *
625 * "row" holds the actual image, and pixels are placed in it
626 * as they arrive. If the image is displayed after each pass, it will
627 * appear to "sparkle" in. "display_row" can be used to display a
628 * "chunky" progressive image, with finer detail added as it becomes
629 * available. If you do not want this "chunky" display, you may pass
630 * NULL for display_row. If you do not want the sparkle display, and
631 * you have not called png_handle_alpha(), you may pass NULL for rows.
632 * If you have called png_handle_alpha(), and the image has either an
633 * alpha channel or a transparency chunk, you must provide a buffer for
634 * rows. In this case, you do not have to provide a display_row buffer
635 * also, but you may. If the image is not interlaced, or if you have
636 * not called png_set_interlace_handling(), the display_row buffer will
637 * be ignored, so pass NULL to it.
638 *
639 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
640 */
641
642 void PNGAPI
png_read_rows(png_structrp png_ptr,png_bytepp row,png_bytepp display_row,png_uint_32 num_rows)643 png_read_rows(png_structrp png_ptr, png_bytepp row,
644 png_bytepp display_row, png_uint_32 num_rows)
645 {
646 png_uint_32 i;
647 png_bytepp rp;
648 png_bytepp dp;
649
650 png_debug(1, "in png_read_rows");
651
652 if (png_ptr == NULL)
653 return;
654
655 rp = row;
656 dp = display_row;
657 if (rp != NULL && dp != NULL)
658 for (i = 0; i < num_rows; i++)
659 {
660 png_bytep rptr = *rp++;
661 png_bytep dptr = *dp++;
662
663 png_read_row(png_ptr, rptr, dptr);
664 }
665
666 else if (rp != NULL)
667 for (i = 0; i < num_rows; i++)
668 {
669 png_bytep rptr = *rp;
670 png_read_row(png_ptr, rptr, NULL);
671 rp++;
672 }
673
674 else if (dp != NULL)
675 for (i = 0; i < num_rows; i++)
676 {
677 png_bytep dptr = *dp;
678 png_read_row(png_ptr, NULL, dptr);
679 dp++;
680 }
681 }
682 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
683
684 #ifdef PNG_INDEX_SUPPORTED
685 #define IDAT_HEADER_SIZE 8
686
687 /* Set the png read position to a new position based on idat_position and
688 * offset.
689 */
690 void
png_set_read_offset(png_structp png_ptr,png_uint_32 idat_position,png_uint_32 bytes_left)691 png_set_read_offset(png_structp png_ptr,
692 png_uint_32 idat_position, png_uint_32 bytes_left)
693 {
694 png_seek_data(png_ptr, idat_position);
695 png_ptr->idat_size = png_read_chunk_header(png_ptr);
696
697 // We need to add back IDAT_HEADER_SIZE because in zlib's perspective,
698 // IDAT_HEADER in PNG is already stripped out.
699 png_seek_data(png_ptr, idat_position + IDAT_HEADER_SIZE + png_ptr->idat_size - bytes_left);
700 png_ptr->idat_size = bytes_left;
701 }
702
703 /* Configure png decoder to decode the pass starting from *row.
704 * The requested row may be adjusted to align with an indexing row.
705 * The actual row for the decoder to start its decoding will be returned in
706 * *row.
707 */
708 void PNGAPI
png_configure_decoder(png_structp png_ptr,int * row,int pass)709 png_configure_decoder(png_structp png_ptr, int *row, int pass)
710 {
711 png_indexp index = png_ptr->index;
712 int n = *row / index->step[pass];
713 png_line_indexp line_index = index->pass_line_index[pass][n];
714
715 // Adjust row to an indexing row.
716 *row = n * index->step[pass];
717 png_ptr->row_number = *row;
718
719 #ifdef PNG_READ_INTERLACING_SUPPORTED
720 if (png_ptr->interlaced)
721 png_set_interlaced_pass(png_ptr, pass);
722 #endif
723
724 long row_byte_length =
725 PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1;
726
727 inflateEnd(&png_ptr->zstream);
728 inflateCopy(&png_ptr->zstream, line_index->z_state);
729
730 // Set the png read position to line_index.
731 png_set_read_offset(png_ptr, line_index->stream_idat_position,
732 line_index->bytes_left_in_idat);
733 memcpy(png_ptr->prev_row, line_index->prev_row, row_byte_length);
734 png_ptr->zstream.avail_in = 0;
735 }
736
737 /* Build the line index and store the index in png_ptr->index.
738 */
739 void PNGAPI
png_build_index(png_structp png_ptr)740 png_build_index(png_structp png_ptr)
741 {
742 // number of rows in a 8x8 block for each interlaced pass.
743 int number_rows_in_pass[7] = {1, 1, 1, 2, 2, 4, 4};
744
745 int ret;
746 png_uint_32 i, j;
747 png_bytep rp;
748 int p, pass_number = 1;
749
750 #ifdef PNG_READ_INTERLACING_SUPPORTED
751 pass_number = png_set_interlace_handling(png_ptr);
752 #endif
753
754 if (png_ptr == NULL)
755 return;
756
757 png_read_start_row(png_ptr);
758
759 #ifdef PNG_READ_INTERLACING_SUPPORTED
760 if (!png_ptr->interlaced)
761 #endif
762 {
763 number_rows_in_pass[0] = 8;
764 }
765
766 // Allocate a buffer big enough for any transform.
767 rp = png_malloc(png_ptr, PNG_ROWBYTES(png_ptr->maximum_pixel_depth, png_ptr->width));
768
769 png_indexp index = png_malloc(png_ptr, sizeof(png_index));
770 png_ptr->index = index;
771
772 index->stream_idat_position = png_ptr->total_data_read - IDAT_HEADER_SIZE;
773
774 // Set the default size of index in each pass to 0,
775 // so that we can free index correctly in png_destroy_read_struct.
776 for (p = 0; p < 7; p++)
777 index->size[p] = 0;
778
779 for (p = 0; p < pass_number; p++)
780 {
781 // We adjust the index step in each pass to make sure each pass
782 // has roughly the same size of index.
783 // This way, we won't consume to much memory in recording index.
784 index->step[p] = INDEX_SAMPLE_SIZE * (8 / number_rows_in_pass[p]);
785 const png_uint_32 temp_size =
786 (png_ptr->height + index->step[p] - 1) / index->step[p];
787 index->pass_line_index[p] =
788 png_malloc(png_ptr, temp_size * sizeof(png_line_indexp));
789
790 // Get the row_byte_length seen by the filter. This value may be
791 // different from the row_byte_length of a bitmap in the case of
792 // color palette mode.
793 int row_byte_length =
794 PNG_ROWBYTES(png_ptr->pixel_depth, png_ptr->iwidth) + 1;
795
796 // Now, we record index for each indexing row.
797 for (i = 0; i < temp_size; i++)
798 {
799 png_line_indexp line_index = png_malloc(png_ptr, sizeof(png_line_index));
800 index->pass_line_index[p][i] = line_index;
801
802 line_index->z_state = png_malloc(png_ptr, sizeof(z_stream));
803 inflateCopy(line_index->z_state, &png_ptr->zstream);
804 line_index->prev_row = png_malloc(png_ptr, row_byte_length);
805 memcpy(line_index->prev_row, png_ptr->prev_row, row_byte_length);
806 line_index->stream_idat_position = index->stream_idat_position;
807 line_index->bytes_left_in_idat = png_ptr->idat_size + png_ptr->zstream.avail_in;
808
809 // increment the size now that we have the backing data structures.
810 // This prevents a crash in the event that png_read_row fails and
811 // we need to cleanup the partially constructed png_index_struct;
812 index->size[p] += 1;
813
814 // Skip the "step" number of rows to the next indexing row.
815 for (j = 0; j < index->step[p] &&
816 i * index->step[p] + j < png_ptr->height; j++)
817 {
818 png_read_row(png_ptr, rp, NULL);
819 }
820 }
821 }
822 png_free(png_ptr, rp);
823 }
824 #endif
825
826 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
827 /* Read the entire image. If the image has an alpha channel or a tRNS
828 * chunk, and you have called png_handle_alpha()[*], you will need to
829 * initialize the image to the current image that PNG will be overlaying.
830 * We set the num_rows again here, in case it was incorrectly set in
831 * png_read_start_row() by a call to png_read_update_info() or
832 * png_start_read_image() if png_set_interlace_handling() wasn't called
833 * prior to either of these functions like it should have been. You can
834 * only call this function once. If you desire to have an image for
835 * each pass of a interlaced image, use png_read_rows() instead.
836 *
837 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
838 */
839 void PNGAPI
png_read_image(png_structrp png_ptr,png_bytepp image)840 png_read_image(png_structrp png_ptr, png_bytepp image)
841 {
842 png_uint_32 i, image_height;
843 int pass, j;
844 png_bytepp rp;
845
846 png_debug(1, "in png_read_image");
847
848 if (png_ptr == NULL)
849 return;
850
851 #ifdef PNG_READ_INTERLACING_SUPPORTED
852 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
853 {
854 pass = png_set_interlace_handling(png_ptr);
855 /* And make sure transforms are initialized. */
856 png_start_read_image(png_ptr);
857 }
858 else
859 {
860 if (png_ptr->interlaced && !(png_ptr->transformations & PNG_INTERLACE))
861 {
862 /* Caller called png_start_read_image or png_read_update_info without
863 * first turning on the PNG_INTERLACE transform. We can fix this here,
864 * but the caller should do it!
865 */
866 png_warning(png_ptr, "Interlace handling should be turned on when "
867 "using png_read_image");
868 /* Make sure this is set correctly */
869 png_ptr->num_rows = png_ptr->height;
870 }
871
872 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
873 * the above error case.
874 */
875 pass = png_set_interlace_handling(png_ptr);
876 }
877 #else
878 if (png_ptr->interlaced)
879 png_error(png_ptr,
880 "Cannot read interlaced image -- interlace handler disabled");
881
882 pass = 1;
883 #endif
884
885 image_height=png_ptr->height;
886
887 for (j = 0; j < pass; j++)
888 {
889 rp = image;
890 for (i = 0; i < image_height; i++)
891 {
892 png_read_row(png_ptr, *rp, NULL);
893 rp++;
894 }
895 }
896 }
897 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
898
899 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
900 /* Read the end of the PNG file. Will not read past the end of the
901 * file, will verify the end is accurate, and will read any comments
902 * or time information at the end of the file, if info is not NULL.
903 */
904 void PNGAPI
png_read_end(png_structrp png_ptr,png_inforp info_ptr)905 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
906 {
907 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
908 int keep;
909 #endif
910
911 png_debug(1, "in png_read_end");
912
913 if (png_ptr == NULL)
914 return;
915
916 /* If png_read_end is called in the middle of reading the rows there may
917 * still be pending IDAT data and an owned zstream. Deal with this here.
918 */
919 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
920 if (!png_chunk_unknown_handling(png_ptr, png_IDAT))
921 #endif
922 png_read_finish_IDAT(png_ptr);
923
924 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
925 /* Report invalid palette index; added at libng-1.5.10 */
926 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
927 png_ptr->num_palette_max > png_ptr->num_palette)
928 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
929 #endif
930
931 do
932 {
933 png_uint_32 length = png_read_chunk_header(png_ptr);
934 png_uint_32 chunk_name = png_ptr->chunk_name;
935
936 if (chunk_name == png_IEND)
937 png_handle_IEND(png_ptr, info_ptr, length);
938
939 else if (chunk_name == png_IHDR)
940 png_handle_IHDR(png_ptr, info_ptr, length);
941
942 else if (info_ptr == NULL)
943 png_crc_finish(png_ptr, length);
944
945 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
946 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
947 {
948 if (chunk_name == png_IDAT)
949 {
950 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
951 png_benign_error(png_ptr, "Too many IDATs found");
952 }
953 png_handle_unknown(png_ptr, info_ptr, length, keep);
954 if (chunk_name == png_PLTE)
955 png_ptr->mode |= PNG_HAVE_PLTE;
956 }
957 #endif
958
959 else if (chunk_name == png_IDAT)
960 {
961 /* Zero length IDATs are legal after the last IDAT has been
962 * read, but not after other chunks have been read.
963 */
964 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
965 png_benign_error(png_ptr, "Too many IDATs found");
966
967 png_crc_finish(png_ptr, length);
968 }
969 else if (chunk_name == png_PLTE)
970 png_handle_PLTE(png_ptr, info_ptr, length);
971
972 #ifdef PNG_READ_bKGD_SUPPORTED
973 else if (chunk_name == png_bKGD)
974 png_handle_bKGD(png_ptr, info_ptr, length);
975 #endif
976
977 #ifdef PNG_READ_cHRM_SUPPORTED
978 else if (chunk_name == png_cHRM)
979 png_handle_cHRM(png_ptr, info_ptr, length);
980 #endif
981
982 #ifdef PNG_READ_gAMA_SUPPORTED
983 else if (chunk_name == png_gAMA)
984 png_handle_gAMA(png_ptr, info_ptr, length);
985 #endif
986
987 #ifdef PNG_READ_hIST_SUPPORTED
988 else if (chunk_name == png_hIST)
989 png_handle_hIST(png_ptr, info_ptr, length);
990 #endif
991
992 #ifdef PNG_READ_oFFs_SUPPORTED
993 else if (chunk_name == png_oFFs)
994 png_handle_oFFs(png_ptr, info_ptr, length);
995 #endif
996
997 #ifdef PNG_READ_pCAL_SUPPORTED
998 else if (chunk_name == png_pCAL)
999 png_handle_pCAL(png_ptr, info_ptr, length);
1000 #endif
1001
1002 #ifdef PNG_READ_sCAL_SUPPORTED
1003 else if (chunk_name == png_sCAL)
1004 png_handle_sCAL(png_ptr, info_ptr, length);
1005 #endif
1006
1007 #ifdef PNG_READ_pHYs_SUPPORTED
1008 else if (chunk_name == png_pHYs)
1009 png_handle_pHYs(png_ptr, info_ptr, length);
1010 #endif
1011
1012 #ifdef PNG_READ_sBIT_SUPPORTED
1013 else if (chunk_name == png_sBIT)
1014 png_handle_sBIT(png_ptr, info_ptr, length);
1015 #endif
1016
1017 #ifdef PNG_READ_sRGB_SUPPORTED
1018 else if (chunk_name == png_sRGB)
1019 png_handle_sRGB(png_ptr, info_ptr, length);
1020 #endif
1021
1022 #ifdef PNG_READ_iCCP_SUPPORTED
1023 else if (chunk_name == png_iCCP)
1024 png_handle_iCCP(png_ptr, info_ptr, length);
1025 #endif
1026
1027 #ifdef PNG_READ_sPLT_SUPPORTED
1028 else if (chunk_name == png_sPLT)
1029 png_handle_sPLT(png_ptr, info_ptr, length);
1030 #endif
1031
1032 #ifdef PNG_READ_tEXt_SUPPORTED
1033 else if (chunk_name == png_tEXt)
1034 png_handle_tEXt(png_ptr, info_ptr, length);
1035 #endif
1036
1037 #ifdef PNG_READ_tIME_SUPPORTED
1038 else if (chunk_name == png_tIME)
1039 png_handle_tIME(png_ptr, info_ptr, length);
1040 #endif
1041
1042 #ifdef PNG_READ_tRNS_SUPPORTED
1043 else if (chunk_name == png_tRNS)
1044 png_handle_tRNS(png_ptr, info_ptr, length);
1045 #endif
1046
1047 #ifdef PNG_READ_zTXt_SUPPORTED
1048 else if (chunk_name == png_zTXt)
1049 png_handle_zTXt(png_ptr, info_ptr, length);
1050 #endif
1051
1052 #ifdef PNG_READ_iTXt_SUPPORTED
1053 else if (chunk_name == png_iTXt)
1054 png_handle_iTXt(png_ptr, info_ptr, length);
1055 #endif
1056
1057 else
1058 png_handle_unknown(png_ptr, info_ptr, length,
1059 PNG_HANDLE_CHUNK_AS_DEFAULT);
1060 } while (!(png_ptr->mode & PNG_HAVE_IEND));
1061 }
1062 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
1063
1064 /* Free all memory used in the read struct */
1065 static void
png_read_destroy(png_structrp png_ptr)1066 png_read_destroy(png_structrp png_ptr)
1067 {
1068 png_debug(1, "in png_read_destroy");
1069
1070 #ifdef PNG_READ_GAMMA_SUPPORTED
1071 png_destroy_gamma_table(png_ptr);
1072 #endif
1073
1074 png_free(png_ptr, png_ptr->big_row_buf);
1075 png_free(png_ptr, png_ptr->big_prev_row);
1076 png_free(png_ptr, png_ptr->read_buffer);
1077
1078 #ifdef PNG_READ_QUANTIZE_SUPPORTED
1079 png_free(png_ptr, png_ptr->palette_lookup);
1080 png_free(png_ptr, png_ptr->quantize_index);
1081 #endif
1082
1083 if (png_ptr->free_me & PNG_FREE_PLTE)
1084 png_zfree(png_ptr, png_ptr->palette);
1085 png_ptr->free_me &= ~PNG_FREE_PLTE;
1086
1087 #if defined(PNG_tRNS_SUPPORTED) || \
1088 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
1089 if (png_ptr->free_me & PNG_FREE_TRNS)
1090 png_free(png_ptr, png_ptr->trans_alpha);
1091 png_ptr->free_me &= ~PNG_FREE_TRNS;
1092 #endif
1093
1094 inflateEnd(&png_ptr->zstream);
1095
1096 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
1097 png_free(png_ptr, png_ptr->save_buffer);
1098 #endif
1099
1100 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) &&\
1101 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
1102 png_free(png_ptr, png_ptr->unknown_chunk.data);
1103 #endif
1104
1105 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
1106 png_free(png_ptr, png_ptr->chunk_list);
1107 #endif
1108
1109 #ifdef PNG_INDEX_SUPPORTED
1110 if (png_ptr->index) {
1111 unsigned int i, p;
1112 png_indexp index = png_ptr->index;
1113 for (p = 0; p < 7; p++) {
1114 for (i = 0; i < index->size[p]; i++) {
1115 inflateEnd(index->pass_line_index[p][i]->z_state);
1116 png_free(png_ptr, index->pass_line_index[p][i]->z_state);
1117 png_free(png_ptr, index->pass_line_index[p][i]->prev_row);
1118 png_free(png_ptr, index->pass_line_index[p][i]);
1119 }
1120 if (index->size[p] != 0) {
1121 png_free(png_ptr, index->pass_line_index[p]);
1122 }
1123 }
1124 png_free(png_ptr, index);
1125 }
1126 #endif
1127
1128 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
1129 * callbacks are still set at this point. They are required to complete the
1130 * destruction of the png_struct itself.
1131 */
1132 }
1133
1134 /* Free all memory used by the read */
1135 void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr,png_infopp info_ptr_ptr,png_infopp end_info_ptr_ptr)1136 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1137 png_infopp end_info_ptr_ptr)
1138 {
1139 png_structrp png_ptr = NULL;
1140
1141 png_debug(1, "in png_destroy_read_struct");
1142
1143 if (png_ptr_ptr != NULL)
1144 png_ptr = *png_ptr_ptr;
1145
1146 if (png_ptr == NULL)
1147 return;
1148
1149 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1150 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1151 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1152 */
1153 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1154 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1155
1156 *png_ptr_ptr = NULL;
1157 png_read_destroy(png_ptr);
1158 png_destroy_png_struct(png_ptr);
1159 }
1160
1161 void PNGAPI
png_set_read_status_fn(png_structrp png_ptr,png_read_status_ptr read_row_fn)1162 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1163 {
1164 if (png_ptr == NULL)
1165 return;
1166
1167 png_ptr->read_row_fn = read_row_fn;
1168 }
1169
1170
1171 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1172 #ifdef PNG_INFO_IMAGE_SUPPORTED
1173 void PNGAPI
png_read_png(png_structrp png_ptr,png_inforp info_ptr,int transforms,voidp params)1174 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1175 int transforms,
1176 voidp params)
1177 {
1178 if (png_ptr == NULL || info_ptr == NULL)
1179 return;
1180
1181 /* png_read_info() gives us all of the information from the
1182 * PNG file before the first IDAT (image data chunk).
1183 */
1184 png_read_info(png_ptr, info_ptr);
1185 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1186 png_error(png_ptr, "Image is too high to process with png_read_png()");
1187
1188 /* -------------- image transformations start here ------------------- */
1189 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1190 * is not implemented. This will only happen in de-configured (non-default)
1191 * libpng builds. The results can be unexpected - png_read_png may return
1192 * short or mal-formed rows because the transform is skipped.
1193 */
1194
1195 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1196 */
1197 if (transforms & PNG_TRANSFORM_SCALE_16)
1198 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1199 * did in earlier versions, while "scale_16" is now more accurate.
1200 */
1201 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1202 png_set_scale_16(png_ptr);
1203 #else
1204 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1205 #endif
1206
1207 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1208 * latter by doing SCALE first. This is ok and allows apps not to check for
1209 * which is supported to get the right answer.
1210 */
1211 if (transforms & PNG_TRANSFORM_STRIP_16)
1212 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1213 png_set_strip_16(png_ptr);
1214 #else
1215 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1216 #endif
1217
1218 /* Strip alpha bytes from the input data without combining with
1219 * the background (not recommended).
1220 */
1221 if (transforms & PNG_TRANSFORM_STRIP_ALPHA)
1222 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1223 png_set_strip_alpha(png_ptr);
1224 #else
1225 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1226 #endif
1227
1228 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1229 * byte into separate bytes (useful for paletted and grayscale images).
1230 */
1231 if (transforms & PNG_TRANSFORM_PACKING)
1232 #ifdef PNG_READ_PACK_SUPPORTED
1233 png_set_packing(png_ptr);
1234 #else
1235 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1236 #endif
1237
1238 /* Change the order of packed pixels to least significant bit first
1239 * (not useful if you are using png_set_packing).
1240 */
1241 if (transforms & PNG_TRANSFORM_PACKSWAP)
1242 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1243 png_set_packswap(png_ptr);
1244 #else
1245 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1246 #endif
1247
1248 /* Expand paletted colors into true RGB triplets
1249 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1250 * Expand paletted or RGB images with transparency to full alpha
1251 * channels so the data will be available as RGBA quartets.
1252 */
1253 if (transforms & PNG_TRANSFORM_EXPAND)
1254 #ifdef PNG_READ_EXPAND_SUPPORTED
1255 png_set_expand(png_ptr);
1256 #else
1257 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1258 #endif
1259
1260 /* We don't handle background color or gamma transformation or quantizing.
1261 */
1262
1263 /* Invert monochrome files to have 0 as white and 1 as black
1264 */
1265 if (transforms & PNG_TRANSFORM_INVERT_MONO)
1266 #ifdef PNG_READ_INVERT_SUPPORTED
1267 png_set_invert_mono(png_ptr);
1268 #else
1269 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1270 #endif
1271
1272 /* If you want to shift the pixel values from the range [0,255] or
1273 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1274 * colors were originally in:
1275 */
1276 if (transforms & PNG_TRANSFORM_SHIFT)
1277 #ifdef PNG_READ_SHIFT_SUPPORTED
1278 if (info_ptr->valid & PNG_INFO_sBIT)
1279 png_set_shift(png_ptr, &info_ptr->sig_bit);
1280 #else
1281 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1282 #endif
1283
1284 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1285 if (transforms & PNG_TRANSFORM_BGR)
1286 #ifdef PNG_READ_BGR_SUPPORTED
1287 png_set_bgr(png_ptr);
1288 #else
1289 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1290 #endif
1291
1292 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1293 if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
1294 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1295 png_set_swap_alpha(png_ptr);
1296 #else
1297 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1298 #endif
1299
1300 /* Swap bytes of 16-bit files to least significant byte first */
1301 if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
1302 #ifdef PNG_READ_SWAP_SUPPORTED
1303 png_set_swap(png_ptr);
1304 #else
1305 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1306 #endif
1307
1308 /* Added at libpng-1.2.41 */
1309 /* Invert the alpha channel from opacity to transparency */
1310 if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
1311 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1312 png_set_invert_alpha(png_ptr);
1313 #else
1314 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1315 #endif
1316
1317 /* Added at libpng-1.2.41 */
1318 /* Expand grayscale image to RGB */
1319 if (transforms & PNG_TRANSFORM_GRAY_TO_RGB)
1320 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1321 png_set_gray_to_rgb(png_ptr);
1322 #else
1323 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1324 #endif
1325
1326 /* Added at libpng-1.5.4 */
1327 if (transforms & PNG_TRANSFORM_EXPAND_16)
1328 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1329 png_set_expand_16(png_ptr);
1330 #else
1331 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1332 #endif
1333
1334 /* We don't handle adding filler bytes */
1335
1336 /* We use png_read_image and rely on that for interlace handling, but we also
1337 * call png_read_update_info therefore must turn on interlace handling now:
1338 */
1339 (void)png_set_interlace_handling(png_ptr);
1340
1341 /* Optional call to gamma correct and add the background to the palette
1342 * and update info structure. REQUIRED if you are expecting libpng to
1343 * update the palette for you (i.e., you selected such a transform above).
1344 */
1345 png_read_update_info(png_ptr, info_ptr);
1346
1347 /* -------------- image transformations end here ------------------- */
1348
1349 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1350 if (info_ptr->row_pointers == NULL)
1351 {
1352 png_uint_32 iptr;
1353
1354 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1355 info_ptr->height * (sizeof (png_bytep))));
1356
1357 for (iptr=0; iptr<info_ptr->height; iptr++)
1358 info_ptr->row_pointers[iptr] = NULL;
1359
1360 info_ptr->free_me |= PNG_FREE_ROWS;
1361
1362 for (iptr = 0; iptr < info_ptr->height; iptr++)
1363 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1364 png_malloc(png_ptr, info_ptr->rowbytes));
1365 }
1366
1367 png_read_image(png_ptr, info_ptr->row_pointers);
1368 info_ptr->valid |= PNG_INFO_IDAT;
1369
1370 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1371 png_read_end(png_ptr, info_ptr);
1372
1373 PNG_UNUSED(params)
1374 }
1375 #endif /* PNG_INFO_IMAGE_SUPPORTED */
1376 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
1377
1378 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1379 /* SIMPLIFIED READ
1380 *
1381 * This code currently relies on the sequential reader, though it could easily
1382 * be made to work with the progressive one.
1383 */
1384 /* Arguments to png_image_finish_read: */
1385
1386 /* Encoding of PNG data (used by the color-map code) */
1387 # define P_NOTSET 0 /* File encoding not yet known */
1388 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1389 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1390 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1391 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1392
1393 /* Color-map processing: after libpng has run on the PNG image further
1394 * processing may be needed to conver the data to color-map indicies.
1395 */
1396 #define PNG_CMAP_NONE 0
1397 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1398 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1399 #define PNG_CMAP_RGB 3 /* Process RGB data */
1400 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1401
1402 /* The following document where the background is for each processing case. */
1403 #define PNG_CMAP_NONE_BACKGROUND 256
1404 #define PNG_CMAP_GA_BACKGROUND 231
1405 #define PNG_CMAP_TRANS_BACKGROUND 254
1406 #define PNG_CMAP_RGB_BACKGROUND 256
1407 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1408
1409 typedef struct
1410 {
1411 /* Arguments: */
1412 png_imagep image;
1413 png_voidp buffer;
1414 png_int_32 row_stride;
1415 png_voidp colormap;
1416 png_const_colorp background;
1417 /* Local variables: */
1418 png_voidp local_row;
1419 png_voidp first_row;
1420 ptrdiff_t row_bytes; /* step between rows */
1421 int file_encoding; /* E_ values above */
1422 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1423 int colormap_processing; /* PNG_CMAP_ values above */
1424 } png_image_read_control;
1425
1426 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1427 * called, so setting up the jmp_buf is not required. This means that anything
1428 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1429 * instead so that control is returned safely back to this routine.
1430 */
1431 static int
png_image_read_init(png_imagep image)1432 png_image_read_init(png_imagep image)
1433 {
1434 if (image->opaque == NULL)
1435 {
1436 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1437 png_safe_error, png_safe_warning);
1438
1439 /* And set the rest of the structure to NULL to ensure that the various
1440 * fields are consistent.
1441 */
1442 memset(image, 0, (sizeof *image));
1443 image->version = PNG_IMAGE_VERSION;
1444
1445 if (png_ptr != NULL)
1446 {
1447 png_infop info_ptr = png_create_info_struct(png_ptr);
1448
1449 if (info_ptr != NULL)
1450 {
1451 png_controlp control = png_voidcast(png_controlp,
1452 png_malloc_warn(png_ptr, (sizeof *control)));
1453
1454 if (control != NULL)
1455 {
1456 memset(control, 0, (sizeof *control));
1457
1458 control->png_ptr = png_ptr;
1459 control->info_ptr = info_ptr;
1460 control->for_write = 0;
1461
1462 image->opaque = control;
1463 return 1;
1464 }
1465
1466 /* Error clean up */
1467 png_destroy_info_struct(png_ptr, &info_ptr);
1468 }
1469
1470 png_destroy_read_struct(&png_ptr, NULL, NULL);
1471 }
1472
1473 return png_image_error(image, "png_image_read: out of memory");
1474 }
1475
1476 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1477 }
1478
1479 /* Utility to find the base format of a PNG file from a png_struct. */
1480 static png_uint_32
png_image_format(png_structrp png_ptr)1481 png_image_format(png_structrp png_ptr)
1482 {
1483 png_uint_32 format = 0;
1484
1485 if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
1486 format |= PNG_FORMAT_FLAG_COLOR;
1487
1488 if (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)
1489 format |= PNG_FORMAT_FLAG_ALPHA;
1490
1491 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1492 * sets the png_struct fields; that's all we are interested in here. The
1493 * precise interaction with an app call to png_set_tRNS and PNG file reading
1494 * is unclear.
1495 */
1496 else if (png_ptr->num_trans > 0)
1497 format |= PNG_FORMAT_FLAG_ALPHA;
1498
1499 if (png_ptr->bit_depth == 16)
1500 format |= PNG_FORMAT_FLAG_LINEAR;
1501
1502 if (png_ptr->color_type & PNG_COLOR_MASK_PALETTE)
1503 format |= PNG_FORMAT_FLAG_COLORMAP;
1504
1505 return format;
1506 }
1507
1508 /* Is the given gamma significantly different from sRGB? The test is the same
1509 * one used in pngrtran.c when deciding whether to do gamma correction. The
1510 * arithmetic optimizes the division by using the fact that the inverse of the
1511 * file sRGB gamma is 2.2
1512 */
1513 static int
png_gamma_not_sRGB(png_fixed_point g)1514 png_gamma_not_sRGB(png_fixed_point g)
1515 {
1516 if (g < PNG_FP_1)
1517 {
1518 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1519 if (g == 0)
1520 return 0;
1521
1522 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1523 }
1524
1525 return 1;
1526 }
1527
1528 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1529 * header and fill in all the information. This is executed in a safe context,
1530 * unlike the init routine above.
1531 */
1532 static int
png_image_read_header(png_voidp argument)1533 png_image_read_header(png_voidp argument)
1534 {
1535 png_imagep image = png_voidcast(png_imagep, argument);
1536 png_structrp png_ptr = image->opaque->png_ptr;
1537 png_inforp info_ptr = image->opaque->info_ptr;
1538
1539 png_set_benign_errors(png_ptr, 1/*warn*/);
1540 png_read_info(png_ptr, info_ptr);
1541
1542 /* Do this the fast way; just read directly out of png_struct. */
1543 image->width = png_ptr->width;
1544 image->height = png_ptr->height;
1545
1546 {
1547 png_uint_32 format = png_image_format(png_ptr);
1548
1549 image->format = format;
1550
1551 #ifdef PNG_COLORSPACE_SUPPORTED
1552 /* Does the colorspace match sRGB? If there is no color endpoint
1553 * (colorant) information assume yes, otherwise require the
1554 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1555 * colorspace has been determined to be invalid ignore it.
1556 */
1557 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1558 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1559 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1560 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1561 #endif
1562 }
1563
1564 /* We need the maximum number of entries regardless of the format the
1565 * application sets here.
1566 */
1567 {
1568 png_uint_32 cmap_entries;
1569
1570 switch (png_ptr->color_type)
1571 {
1572 case PNG_COLOR_TYPE_GRAY:
1573 cmap_entries = 1U << png_ptr->bit_depth;
1574 break;
1575
1576 case PNG_COLOR_TYPE_PALETTE:
1577 cmap_entries = png_ptr->num_palette;
1578 break;
1579
1580 default:
1581 cmap_entries = 256;
1582 break;
1583 }
1584
1585 if (cmap_entries > 256)
1586 cmap_entries = 256;
1587
1588 image->colormap_entries = cmap_entries;
1589 }
1590
1591 return 1;
1592 }
1593
1594 #ifdef PNG_STDIO_SUPPORTED
1595 int PNGAPI
png_image_begin_read_from_stdio(png_imagep image,FILE * file)1596 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1597 {
1598 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1599 {
1600 if (file != NULL)
1601 {
1602 if (png_image_read_init(image))
1603 {
1604 /* This is slightly evil, but png_init_io doesn't do anything other
1605 * than this and we haven't changed the standard IO functions so
1606 * this saves a 'safe' function.
1607 */
1608 image->opaque->png_ptr->io_ptr = file;
1609 return png_safe_execute(image, png_image_read_header, image);
1610 }
1611 }
1612
1613 else
1614 return png_image_error(image,
1615 "png_image_begin_read_from_stdio: invalid argument");
1616 }
1617
1618 else if (image != NULL)
1619 return png_image_error(image,
1620 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1621
1622 return 0;
1623 }
1624
1625 int PNGAPI
png_image_begin_read_from_file(png_imagep image,const char * file_name)1626 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1627 {
1628 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1629 {
1630 if (file_name != NULL)
1631 {
1632 FILE *fp = fopen(file_name, "rb");
1633
1634 if (fp != NULL)
1635 {
1636 if (png_image_read_init(image))
1637 {
1638 image->opaque->png_ptr->io_ptr = fp;
1639 image->opaque->owned_file = 1;
1640 return png_safe_execute(image, png_image_read_header, image);
1641 }
1642
1643 /* Clean up: just the opened file. */
1644 (void)fclose(fp);
1645 }
1646
1647 else
1648 return png_image_error(image, strerror(errno));
1649 }
1650
1651 else
1652 return png_image_error(image,
1653 "png_image_begin_read_from_file: invalid argument");
1654 }
1655
1656 else if (image != NULL)
1657 return png_image_error(image,
1658 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1659
1660 return 0;
1661 }
1662 #endif /* PNG_STDIO_SUPPORTED */
1663
1664 static void PNGCBAPI
png_image_memory_read(png_structp png_ptr,png_bytep out,png_size_t need)1665 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1666 {
1667 if (png_ptr != NULL)
1668 {
1669 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1670 if (image != NULL)
1671 {
1672 png_controlp cp = image->opaque;
1673 if (cp != NULL)
1674 {
1675 png_const_bytep memory = cp->memory;
1676 png_size_t size = cp->size;
1677
1678 if (memory != NULL && size >= need)
1679 {
1680 memcpy(out, memory, need);
1681 cp->memory = memory + need;
1682 cp->size = size - need;
1683 return;
1684 }
1685
1686 png_error(png_ptr, "read beyond end of data");
1687 }
1688 }
1689
1690 png_error(png_ptr, "invalid memory read");
1691 }
1692 }
1693
png_image_begin_read_from_memory(png_imagep image,png_const_voidp memory,png_size_t size)1694 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1695 png_const_voidp memory, png_size_t size)
1696 {
1697 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1698 {
1699 if (memory != NULL && size > 0)
1700 {
1701 if (png_image_read_init(image))
1702 {
1703 /* Now set the IO functions to read from the memory buffer and
1704 * store it into io_ptr. Again do this in-place to avoid calling a
1705 * libpng function that requires error handling.
1706 */
1707 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1708 image->opaque->size = size;
1709 image->opaque->png_ptr->io_ptr = image;
1710 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1711
1712 return png_safe_execute(image, png_image_read_header, image);
1713 }
1714 }
1715
1716 else
1717 return png_image_error(image,
1718 "png_image_begin_read_from_memory: invalid argument");
1719 }
1720
1721 else if (image != NULL)
1722 return png_image_error(image,
1723 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1724
1725 return 0;
1726 }
1727
1728 /* Utility function to skip chunks that are not used by the simplified image
1729 * read functions and an appropriate macro to call it.
1730 */
1731 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1732 static void
png_image_skip_unused_chunks(png_structrp png_ptr)1733 png_image_skip_unused_chunks(png_structrp png_ptr)
1734 {
1735 /* Prepare the reader to ignore all recognized chunks whose data will not
1736 * be used, i.e., all chunks recognized by libpng except for those
1737 * involved in basic image reading:
1738 *
1739 * IHDR, PLTE, IDAT, IEND
1740 *
1741 * Or image data handling:
1742 *
1743 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1744 *
1745 * This provides a small performance improvement and eliminates any
1746 * potential vulnerability to security problems in the unused chunks.
1747 *
1748 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1749 * too. This allows the simplified API to be compiled without iCCP support,
1750 * however if the support is there the chunk is still checked to detect
1751 * errors (which are unfortunately quite common.)
1752 */
1753 {
1754 static PNG_CONST png_byte chunks_to_process[] = {
1755 98, 75, 71, 68, '\0', /* bKGD */
1756 99, 72, 82, 77, '\0', /* cHRM */
1757 103, 65, 77, 65, '\0', /* gAMA */
1758 # ifdef PNG_READ_iCCP_SUPPORTED
1759 105, 67, 67, 80, '\0', /* iCCP */
1760 # endif
1761 115, 66, 73, 84, '\0', /* sBIT */
1762 115, 82, 71, 66, '\0', /* sRGB */
1763 };
1764
1765 /* Ignore unknown chunks and all other chunks except for the
1766 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1767 */
1768 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1769 NULL, -1);
1770
1771 /* But do not ignore image data handling chunks */
1772 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1773 chunks_to_process, (sizeof chunks_to_process)/5);
1774 }
1775 }
1776
1777 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1778 #else
1779 # define PNG_SKIP_CHUNKS(p) ((void)0)
1780 #endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */
1781
1782 /* The following macro gives the exact rounded answer for all values in the
1783 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1784 * the correct numbers 0..5
1785 */
1786 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1787
1788 /* Utility functions to make particular color-maps */
1789 static void
set_file_encoding(png_image_read_control * display)1790 set_file_encoding(png_image_read_control *display)
1791 {
1792 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1793 if (png_gamma_significant(g))
1794 {
1795 if (png_gamma_not_sRGB(g))
1796 {
1797 display->file_encoding = P_FILE;
1798 display->gamma_to_linear = png_reciprocal(g);
1799 }
1800
1801 else
1802 display->file_encoding = P_sRGB;
1803 }
1804
1805 else
1806 display->file_encoding = P_LINEAR8;
1807 }
1808
1809 static unsigned int
decode_gamma(png_image_read_control * display,png_uint_32 value,int encoding)1810 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1811 {
1812 if (encoding == P_FILE) /* double check */
1813 encoding = display->file_encoding;
1814
1815 if (encoding == P_NOTSET) /* must be the file encoding */
1816 {
1817 set_file_encoding(display);
1818 encoding = display->file_encoding;
1819 }
1820
1821 switch (encoding)
1822 {
1823 case P_FILE:
1824 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1825 break;
1826
1827 case P_sRGB:
1828 value = png_sRGB_table[value];
1829 break;
1830
1831 case P_LINEAR:
1832 break;
1833
1834 case P_LINEAR8:
1835 value *= 257;
1836 break;
1837
1838 default:
1839 png_error(display->image->opaque->png_ptr,
1840 "unexpected encoding (internal error)");
1841 break;
1842 }
1843
1844 return value;
1845 }
1846
1847 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)1848 png_colormap_compose(png_image_read_control *display,
1849 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1850 png_uint_32 background, int encoding)
1851 {
1852 /* The file value is composed on the background, the background has the given
1853 * encoding and so does the result, the file is encoded with P_FILE and the
1854 * file and alpha are 8-bit values. The (output) encoding will always be
1855 * P_LINEAR or P_sRGB.
1856 */
1857 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1858 png_uint_32 b = decode_gamma(display, background, encoding);
1859
1860 /* The alpha is always an 8-bit value (it comes from the palette), the value
1861 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1862 */
1863 f = f * alpha + b * (255-alpha);
1864
1865 if (encoding == P_LINEAR)
1866 {
1867 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1868 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1869 */
1870 f *= 257; /* Now scaled by 65535 */
1871 f += f >> 16;
1872 f = (f+32768) >> 16;
1873 }
1874
1875 else /* P_sRGB */
1876 f = PNG_sRGB_FROM_LINEAR(f);
1877
1878 return f;
1879 }
1880
1881 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1882 * be 8-bit.
1883 */
1884 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)1885 png_create_colormap_entry(png_image_read_control *display,
1886 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1887 png_uint_32 alpha, int encoding)
1888 {
1889 png_imagep image = display->image;
1890 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) ?
1891 P_LINEAR : P_sRGB;
1892 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1893 (red != green || green != blue);
1894
1895 if (ip > 255)
1896 png_error(image->opaque->png_ptr, "color-map index out of range");
1897
1898 /* Update the cache with whether the file gamma is significantly different
1899 * from sRGB.
1900 */
1901 if (encoding == P_FILE)
1902 {
1903 if (display->file_encoding == P_NOTSET)
1904 set_file_encoding(display);
1905
1906 /* Note that the cached value may be P_FILE too, but if it is then the
1907 * gamma_to_linear member has been set.
1908 */
1909 encoding = display->file_encoding;
1910 }
1911
1912 if (encoding == P_FILE)
1913 {
1914 png_fixed_point g = display->gamma_to_linear;
1915
1916 red = png_gamma_16bit_correct(red*257, g);
1917 green = png_gamma_16bit_correct(green*257, g);
1918 blue = png_gamma_16bit_correct(blue*257, g);
1919
1920 if (convert_to_Y || output_encoding == P_LINEAR)
1921 {
1922 alpha *= 257;
1923 encoding = P_LINEAR;
1924 }
1925
1926 else
1927 {
1928 red = PNG_sRGB_FROM_LINEAR(red * 255);
1929 green = PNG_sRGB_FROM_LINEAR(green * 255);
1930 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1931 encoding = P_sRGB;
1932 }
1933 }
1934
1935 else if (encoding == P_LINEAR8)
1936 {
1937 /* This encoding occurs quite frequently in test cases because PngSuite
1938 * includes a gAMA 1.0 chunk with most images.
1939 */
1940 red *= 257;
1941 green *= 257;
1942 blue *= 257;
1943 alpha *= 257;
1944 encoding = P_LINEAR;
1945 }
1946
1947 else if (encoding == P_sRGB && (convert_to_Y || output_encoding == P_LINEAR))
1948 {
1949 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1950 * linear.
1951 */
1952 red = png_sRGB_table[red];
1953 green = png_sRGB_table[green];
1954 blue = png_sRGB_table[blue];
1955 alpha *= 257;
1956 encoding = P_LINEAR;
1957 }
1958
1959 /* This is set if the color isn't gray but the output is. */
1960 if (encoding == P_LINEAR)
1961 {
1962 if (convert_to_Y)
1963 {
1964 /* NOTE: these values are copied from png_do_rgb_to_gray */
1965 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1966 (png_uint_32)2366 * blue;
1967
1968 if (output_encoding == P_LINEAR)
1969 y = (y + 16384) >> 15;
1970
1971 else
1972 {
1973 /* y is scaled by 32768, we need it scaled by 255: */
1974 y = (y + 128) >> 8;
1975 y *= 255;
1976 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1977 encoding = P_sRGB;
1978 }
1979
1980 blue = red = green = y;
1981 }
1982
1983 else if (output_encoding == P_sRGB)
1984 {
1985 red = PNG_sRGB_FROM_LINEAR(red * 255);
1986 green = PNG_sRGB_FROM_LINEAR(green * 255);
1987 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1988 alpha = PNG_DIV257(alpha);
1989 encoding = P_sRGB;
1990 }
1991 }
1992
1993 if (encoding != output_encoding)
1994 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1995
1996 /* Store the value. */
1997 {
1998 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1999 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
2000 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
2001 # else
2002 # define afirst 0
2003 # endif
2004 # ifdef PNG_FORMAT_BGR_SUPPORTED
2005 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) ? 2 : 0;
2006 # else
2007 # define bgr 0
2008 # endif
2009
2010 if (output_encoding == P_LINEAR)
2011 {
2012 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
2013
2014 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
2015
2016 /* The linear 16-bit values must be pre-multiplied by the alpha channel
2017 * value, if less than 65535 (this is, effectively, composite on black
2018 * if the alpha channel is removed.)
2019 */
2020 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
2021 {
2022 case 4:
2023 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
2024 /* FALL THROUGH */
2025
2026 case 3:
2027 if (alpha < 65535)
2028 {
2029 if (alpha > 0)
2030 {
2031 blue = (blue * alpha + 32767U)/65535U;
2032 green = (green * alpha + 32767U)/65535U;
2033 red = (red * alpha + 32767U)/65535U;
2034 }
2035
2036 else
2037 red = green = blue = 0;
2038 }
2039 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
2040 entry[afirst + 1] = (png_uint_16)green;
2041 entry[afirst + bgr] = (png_uint_16)red;
2042 break;
2043
2044 case 2:
2045 entry[1 ^ afirst] = (png_uint_16)alpha;
2046 /* FALL THROUGH */
2047
2048 case 1:
2049 if (alpha < 65535)
2050 {
2051 if (alpha > 0)
2052 green = (green * alpha + 32767U)/65535U;
2053
2054 else
2055 green = 0;
2056 }
2057 entry[afirst] = (png_uint_16)green;
2058 break;
2059
2060 default:
2061 break;
2062 }
2063 }
2064
2065 else /* output encoding is P_sRGB */
2066 {
2067 png_bytep entry = png_voidcast(png_bytep, display->colormap);
2068
2069 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
2070
2071 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
2072 {
2073 case 4:
2074 entry[afirst ? 0 : 3] = (png_byte)alpha;
2075 case 3:
2076 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
2077 entry[afirst + 1] = (png_byte)green;
2078 entry[afirst + bgr] = (png_byte)red;
2079 break;
2080
2081 case 2:
2082 entry[1 ^ afirst] = (png_byte)alpha;
2083 case 1:
2084 entry[afirst] = (png_byte)green;
2085 break;
2086
2087 default:
2088 break;
2089 }
2090 }
2091
2092 # ifdef afirst
2093 # undef afirst
2094 # endif
2095 # ifdef bgr
2096 # undef bgr
2097 # endif
2098 }
2099 }
2100
2101 static int
make_gray_file_colormap(png_image_read_control * display)2102 make_gray_file_colormap(png_image_read_control *display)
2103 {
2104 unsigned int i;
2105
2106 for (i=0; i<256; ++i)
2107 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
2108
2109 return i;
2110 }
2111
2112 static int
make_gray_colormap(png_image_read_control * display)2113 make_gray_colormap(png_image_read_control *display)
2114 {
2115 unsigned int i;
2116
2117 for (i=0; i<256; ++i)
2118 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
2119
2120 return i;
2121 }
2122 #define PNG_GRAY_COLORMAP_ENTRIES 256
2123
2124 static int
make_ga_colormap(png_image_read_control * display)2125 make_ga_colormap(png_image_read_control *display)
2126 {
2127 unsigned int i, a;
2128
2129 /* Alpha is retained, the output will be a color-map with entries
2130 * selected by six levels of alpha. One transparent entry, 6 gray
2131 * levels for all the intermediate alpha values, leaving 230 entries
2132 * for the opaque grays. The color-map entries are the six values
2133 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2134 * relevant entry.
2135 *
2136 * if (alpha > 229) // opaque
2137 * {
2138 * // The 231 entries are selected to make the math below work:
2139 * base = 0;
2140 * entry = (231 * gray + 128) >> 8;
2141 * }
2142 * else if (alpha < 26) // transparent
2143 * {
2144 * base = 231;
2145 * entry = 0;
2146 * }
2147 * else // partially opaque
2148 * {
2149 * base = 226 + 6 * PNG_DIV51(alpha);
2150 * entry = PNG_DIV51(gray);
2151 * }
2152 */
2153 i = 0;
2154 while (i < 231)
2155 {
2156 unsigned int gray = (i * 256 + 115) / 231;
2157 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2158 }
2159
2160 /* 255 is used here for the component values for consistency with the code
2161 * that undoes premultiplication in pngwrite.c.
2162 */
2163 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2164
2165 for (a=1; a<5; ++a)
2166 {
2167 unsigned int g;
2168
2169 for (g=0; g<6; ++g)
2170 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2171 P_sRGB);
2172 }
2173
2174 return i;
2175 }
2176
2177 #define PNG_GA_COLORMAP_ENTRIES 256
2178
2179 static int
make_rgb_colormap(png_image_read_control * display)2180 make_rgb_colormap(png_image_read_control *display)
2181 {
2182 unsigned int i, r;
2183
2184 /* Build a 6x6x6 opaque RGB cube */
2185 for (i=r=0; r<6; ++r)
2186 {
2187 unsigned int g;
2188
2189 for (g=0; g<6; ++g)
2190 {
2191 unsigned int b;
2192
2193 for (b=0; b<6; ++b)
2194 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2195 P_sRGB);
2196 }
2197 }
2198
2199 return i;
2200 }
2201
2202 #define PNG_RGB_COLORMAP_ENTRIES 216
2203
2204 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2205 #define PNG_RGB_INDEX(r,g,b) \
2206 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2207
2208 static int
png_image_read_colormap(png_voidp argument)2209 png_image_read_colormap(png_voidp argument)
2210 {
2211 png_image_read_control *display =
2212 png_voidcast(png_image_read_control*, argument);
2213 const png_imagep image = display->image;
2214
2215 const png_structrp png_ptr = image->opaque->png_ptr;
2216 const png_uint_32 output_format = image->format;
2217 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) ?
2218 P_LINEAR : P_sRGB;
2219
2220 unsigned int cmap_entries;
2221 unsigned int output_processing; /* Output processing option */
2222 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2223
2224 /* Background information; the background color and the index of this color
2225 * in the color-map if it exists (else 256).
2226 */
2227 unsigned int background_index = 256;
2228 png_uint_32 back_r, back_g, back_b;
2229
2230 /* Flags to accumulate things that need to be done to the input. */
2231 int expand_tRNS = 0;
2232
2233 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2234 * very difficult to do, the results look awful, and it is difficult to see
2235 * what possible use it is because the application can't control the
2236 * color-map.
2237 */
2238 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2239 png_ptr->num_trans > 0) /* alpha in input */ &&
2240 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2241 {
2242 if (output_encoding == P_LINEAR) /* compose on black */
2243 back_b = back_g = back_r = 0;
2244
2245 else if (display->background == NULL /* no way to remove it */)
2246 png_error(png_ptr,
2247 "a background color must be supplied to remove alpha/transparency");
2248
2249 /* Get a copy of the background color (this avoids repeating the checks
2250 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2251 * output format.
2252 */
2253 else
2254 {
2255 back_g = display->background->green;
2256 if (output_format & PNG_FORMAT_FLAG_COLOR)
2257 {
2258 back_r = display->background->red;
2259 back_b = display->background->blue;
2260 }
2261 else
2262 back_b = back_r = back_g;
2263 }
2264 }
2265
2266 else if (output_encoding == P_LINEAR)
2267 back_b = back_r = back_g = 65535;
2268
2269 else
2270 back_b = back_r = back_g = 255;
2271
2272 /* Default the input file gamma if required - this is necessary because
2273 * libpng assumes that if no gamma information is present the data is in the
2274 * output format, but the simplified API deduces the gamma from the input
2275 * format.
2276 */
2277 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2278 {
2279 /* Do this directly, not using the png_colorspace functions, to ensure
2280 * that it happens even if the colorspace is invalid (though probably if
2281 * it is the setting will be ignored) Note that the same thing can be
2282 * achieved at the application interface with png_set_gAMA.
2283 */
2284 if (png_ptr->bit_depth == 16 &&
2285 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2286 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2287
2288 else
2289 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2290
2291 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2292 }
2293
2294 /* Decide what to do based on the PNG color type of the input data. The
2295 * utility function png_create_colormap_entry deals with most aspects of the
2296 * output transformations; this code works out how to produce bytes of
2297 * color-map entries from the original format.
2298 */
2299 switch (png_ptr->color_type)
2300 {
2301 case PNG_COLOR_TYPE_GRAY:
2302 if (png_ptr->bit_depth <= 8)
2303 {
2304 /* There at most 256 colors in the output, regardless of
2305 * transparency.
2306 */
2307 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2308
2309 cmap_entries = 1U << png_ptr->bit_depth;
2310 if (cmap_entries > image->colormap_entries)
2311 png_error(png_ptr, "gray[8] color-map: too few entries");
2312
2313 step = 255 / (cmap_entries - 1);
2314 output_processing = PNG_CMAP_NONE;
2315
2316 /* If there is a tRNS chunk then this either selects a transparent
2317 * value or, if the output has no alpha, the background color.
2318 */
2319 if (png_ptr->num_trans > 0)
2320 {
2321 trans = png_ptr->trans_color.gray;
2322
2323 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2324 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2325 }
2326
2327 /* png_create_colormap_entry just takes an RGBA and writes the
2328 * corresponding color-map entry using the format from 'image',
2329 * including the required conversion to sRGB or linear as
2330 * appropriate. The input values are always either sRGB (if the
2331 * gamma correction flag is 0) or 0..255 scaled file encoded values
2332 * (if the function must gamma correct them).
2333 */
2334 for (i=val=0; i<cmap_entries; ++i, val += step)
2335 {
2336 /* 'i' is a file value. While this will result in duplicated
2337 * entries for 8-bit non-sRGB encoded files it is necessary to
2338 * have non-gamma corrected values to do tRNS handling.
2339 */
2340 if (i != trans)
2341 png_create_colormap_entry(display, i, val, val, val, 255,
2342 P_FILE/*8-bit with file gamma*/);
2343
2344 /* Else this entry is transparent. The colors don't matter if
2345 * there is an alpha channel (back_alpha == 0), but it does no
2346 * harm to pass them in; the values are not set above so this
2347 * passes in white.
2348 *
2349 * NOTE: this preserves the full precision of the application
2350 * supplied background color when it is used.
2351 */
2352 else
2353 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2354 back_alpha, output_encoding);
2355 }
2356
2357 /* We need libpng to preserve the original encoding. */
2358 data_encoding = P_FILE;
2359
2360 /* The rows from libpng, while technically gray values, are now also
2361 * color-map indicies; however, they may need to be expanded to 1
2362 * byte per pixel. This is what png_set_packing does (i.e., it
2363 * unpacks the bit values into bytes.)
2364 */
2365 if (png_ptr->bit_depth < 8)
2366 png_set_packing(png_ptr);
2367 }
2368
2369 else /* bit depth is 16 */
2370 {
2371 /* The 16-bit input values can be converted directly to 8-bit gamma
2372 * encoded values; however, if a tRNS chunk is present 257 color-map
2373 * entries are required. This means that the extra entry requires
2374 * special processing; add an alpha channel, sacrifice gray level
2375 * 254 and convert transparent (alpha==0) entries to that.
2376 *
2377 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2378 * same time to minimize quality loss. If a tRNS chunk is present
2379 * this means libpng must handle it too; otherwise it is impossible
2380 * to do the exact match on the 16-bit value.
2381 *
2382 * If the output has no alpha channel *and* the background color is
2383 * gray then it is possible to let libpng handle the substitution by
2384 * ensuring that the corresponding gray level matches the background
2385 * color exactly.
2386 */
2387 data_encoding = P_sRGB;
2388
2389 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2390 png_error(png_ptr, "gray[16] color-map: too few entries");
2391
2392 cmap_entries = make_gray_colormap(display);
2393
2394 if (png_ptr->num_trans > 0)
2395 {
2396 unsigned int back_alpha;
2397
2398 if (output_format & PNG_FORMAT_FLAG_ALPHA)
2399 back_alpha = 0;
2400
2401 else
2402 {
2403 if (back_r == back_g && back_g == back_b)
2404 {
2405 /* Background is gray; no special processing will be
2406 * required.
2407 */
2408 png_color_16 c;
2409 png_uint_32 gray = back_g;
2410
2411 if (output_encoding == P_LINEAR)
2412 {
2413 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2414
2415 /* And make sure the corresponding palette entry
2416 * matches.
2417 */
2418 png_create_colormap_entry(display, gray, back_g, back_g,
2419 back_g, 65535, P_LINEAR);
2420 }
2421
2422 /* The background passed to libpng, however, must be the
2423 * sRGB value.
2424 */
2425 c.index = 0; /*unused*/
2426 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2427
2428 /* NOTE: does this work without expanding tRNS to alpha?
2429 * It should be the color->gray case below apparently
2430 * doesn't.
2431 */
2432 png_set_background_fixed(png_ptr, &c,
2433 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2434 0/*gamma: not used*/);
2435
2436 output_processing = PNG_CMAP_NONE;
2437 break;
2438 }
2439
2440 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2441 }
2442
2443 /* output_processing means that the libpng-processed row will be
2444 * 8-bit GA and it has to be processing to single byte color-map
2445 * values. Entry 254 is replaced by either a completely
2446 * transparent entry or by the background color at full
2447 * precision (and the background color is not a simple gray leve
2448 * in this case.)
2449 */
2450 expand_tRNS = 1;
2451 output_processing = PNG_CMAP_TRANS;
2452 background_index = 254;
2453
2454 /* And set (overwrite) color-map entry 254 to the actual
2455 * background color at full precision.
2456 */
2457 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2458 back_alpha, output_encoding);
2459 }
2460
2461 else
2462 output_processing = PNG_CMAP_NONE;
2463 }
2464 break;
2465
2466 case PNG_COLOR_TYPE_GRAY_ALPHA:
2467 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2468 * of 65536 combinations. If, however, the alpha channel is to be
2469 * removed there are only 256 possibilities if the background is gray.
2470 * (Otherwise there is a subset of the 65536 possibilities defined by
2471 * the triangle between black, white and the background color.)
2472 *
2473 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2474 * worry about tRNS matching - tRNS is ignored if there is an alpha
2475 * channel.
2476 */
2477 data_encoding = P_sRGB;
2478
2479 if (output_format & PNG_FORMAT_FLAG_ALPHA)
2480 {
2481 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2482 png_error(png_ptr, "gray+alpha color-map: too few entries");
2483
2484 cmap_entries = make_ga_colormap(display);
2485
2486 background_index = PNG_CMAP_GA_BACKGROUND;
2487 output_processing = PNG_CMAP_GA;
2488 }
2489
2490 else /* alpha is removed */
2491 {
2492 /* Alpha must be removed as the PNG data is processed when the
2493 * background is a color because the G and A channels are
2494 * independent and the vector addition (non-parallel vectors) is a
2495 * 2-D problem.
2496 *
2497 * This can be reduced to the same algorithm as above by making a
2498 * colormap containing gray levels (for the opaque grays), a
2499 * background entry (for a transparent pixel) and a set of four six
2500 * level color values, one set for each intermediate alpha value.
2501 * See the comments in make_ga_colormap for how this works in the
2502 * per-pixel processing.
2503 *
2504 * If the background is gray, however, we only need a 256 entry gray
2505 * level color map. It is sufficient to make the entry generated
2506 * for the background color be exactly the color specified.
2507 */
2508 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2509 (back_r == back_g && back_g == back_b))
2510 {
2511 /* Background is gray; no special processing will be required. */
2512 png_color_16 c;
2513 png_uint_32 gray = back_g;
2514
2515 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2516 png_error(png_ptr, "gray-alpha color-map: too few entries");
2517
2518 cmap_entries = make_gray_colormap(display);
2519
2520 if (output_encoding == P_LINEAR)
2521 {
2522 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2523
2524 /* And make sure the corresponding palette entry matches. */
2525 png_create_colormap_entry(display, gray, back_g, back_g,
2526 back_g, 65535, P_LINEAR);
2527 }
2528
2529 /* The background passed to libpng, however, must be the sRGB
2530 * value.
2531 */
2532 c.index = 0; /*unused*/
2533 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2534
2535 png_set_background_fixed(png_ptr, &c,
2536 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2537 0/*gamma: not used*/);
2538
2539 output_processing = PNG_CMAP_NONE;
2540 }
2541
2542 else
2543 {
2544 png_uint_32 i, a;
2545
2546 /* This is the same as png_make_ga_colormap, above, except that
2547 * the entries are all opaque.
2548 */
2549 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2550 png_error(png_ptr, "ga-alpha color-map: too few entries");
2551
2552 i = 0;
2553 while (i < 231)
2554 {
2555 png_uint_32 gray = (i * 256 + 115) / 231;
2556 png_create_colormap_entry(display, i++, gray, gray, gray,
2557 255, P_sRGB);
2558 }
2559
2560 /* NOTE: this preserves the full precision of the application
2561 * background color.
2562 */
2563 background_index = i;
2564 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2565 output_encoding == P_LINEAR ? 65535U : 255U, output_encoding);
2566
2567 /* For non-opaque input composite on the sRGB background - this
2568 * requires inverting the encoding for each component. The input
2569 * is still converted to the sRGB encoding because this is a
2570 * reasonable approximate to the logarithmic curve of human
2571 * visual sensitivity, at least over the narrow range which PNG
2572 * represents. Consequently 'G' is always sRGB encoded, while
2573 * 'A' is linear. We need the linear background colors.
2574 */
2575 if (output_encoding == P_sRGB) /* else already linear */
2576 {
2577 /* This may produce a value not exactly matching the
2578 * background, but that's ok because these numbers are only
2579 * used when alpha != 0
2580 */
2581 back_r = png_sRGB_table[back_r];
2582 back_g = png_sRGB_table[back_g];
2583 back_b = png_sRGB_table[back_b];
2584 }
2585
2586 for (a=1; a<5; ++a)
2587 {
2588 unsigned int g;
2589
2590 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2591 * by an 8-bit alpha value (0..255).
2592 */
2593 png_uint_32 alpha = 51 * a;
2594 png_uint_32 back_rx = (255-alpha) * back_r;
2595 png_uint_32 back_gx = (255-alpha) * back_g;
2596 png_uint_32 back_bx = (255-alpha) * back_b;
2597
2598 for (g=0; g<6; ++g)
2599 {
2600 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2601
2602 png_create_colormap_entry(display, i++,
2603 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2604 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2605 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2606 }
2607 }
2608
2609 cmap_entries = i;
2610 output_processing = PNG_CMAP_GA;
2611 }
2612 }
2613 break;
2614
2615 case PNG_COLOR_TYPE_RGB:
2616 case PNG_COLOR_TYPE_RGB_ALPHA:
2617 /* Exclude the case where the output is gray; we can always handle this
2618 * with the cases above.
2619 */
2620 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2621 {
2622 /* The color-map will be grayscale, so we may as well convert the
2623 * input RGB values to a simple grayscale and use the grayscale
2624 * code above.
2625 *
2626 * NOTE: calling this apparently damages the recognition of the
2627 * transparent color in background color handling; call
2628 * png_set_tRNS_to_alpha before png_set_background_fixed.
2629 */
2630 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2631 -1);
2632 data_encoding = P_sRGB;
2633
2634 /* The output will now be one or two 8-bit gray or gray+alpha
2635 * channels. The more complex case arises when the input has alpha.
2636 */
2637 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2638 png_ptr->num_trans > 0) &&
2639 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2640 {
2641 /* Both input and output have an alpha channel, so no background
2642 * processing is required; just map the GA bytes to the right
2643 * color-map entry.
2644 */
2645 expand_tRNS = 1;
2646
2647 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2648 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2649
2650 cmap_entries = make_ga_colormap(display);
2651 background_index = PNG_CMAP_GA_BACKGROUND;
2652 output_processing = PNG_CMAP_GA;
2653 }
2654
2655 else
2656 {
2657 /* Either the input or the output has no alpha channel, so there
2658 * will be no non-opaque pixels in the color-map; it will just be
2659 * grayscale.
2660 */
2661 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2662 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2663
2664 /* Ideally this code would use libpng to do the gamma correction,
2665 * but if an input alpha channel is to be removed we will hit the
2666 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2667 * correction bug). Fix this by dropping the gamma correction in
2668 * this case and doing it in the palette; this will result in
2669 * duplicate palette entries, but that's better than the
2670 * alternative of double gamma correction.
2671 */
2672 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2673 png_ptr->num_trans > 0) &&
2674 png_gamma_not_sRGB(png_ptr->colorspace.gamma))
2675 {
2676 cmap_entries = make_gray_file_colormap(display);
2677 data_encoding = P_FILE;
2678 }
2679
2680 else
2681 cmap_entries = make_gray_colormap(display);
2682
2683 /* But if the input has alpha or transparency it must be removed
2684 */
2685 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2686 png_ptr->num_trans > 0)
2687 {
2688 png_color_16 c;
2689 png_uint_32 gray = back_g;
2690
2691 /* We need to ensure that the application background exists in
2692 * the colormap and that completely transparent pixels map to
2693 * it. Achieve this simply by ensuring that the entry
2694 * selected for the background really is the background color.
2695 */
2696 if (data_encoding == P_FILE) /* from the fixup above */
2697 {
2698 /* The app supplied a gray which is in output_encoding, we
2699 * need to convert it to a value of the input (P_FILE)
2700 * encoding then set this palette entry to the required
2701 * output encoding.
2702 */
2703 if (output_encoding == P_sRGB)
2704 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2705
2706 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2707 png_ptr->colorspace.gamma)); /* now P_FILE */
2708
2709 /* And make sure the corresponding palette entry contains
2710 * exactly the required sRGB value.
2711 */
2712 png_create_colormap_entry(display, gray, back_g, back_g,
2713 back_g, 0/*unused*/, output_encoding);
2714 }
2715
2716 else if (output_encoding == P_LINEAR)
2717 {
2718 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2719
2720 /* And make sure the corresponding palette entry matches.
2721 */
2722 png_create_colormap_entry(display, gray, back_g, back_g,
2723 back_g, 0/*unused*/, P_LINEAR);
2724 }
2725
2726 /* The background passed to libpng, however, must be the
2727 * output (normally sRGB) value.
2728 */
2729 c.index = 0; /*unused*/
2730 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2731
2732 /* NOTE: the following is apparently a bug in libpng. Without
2733 * it the transparent color recognition in
2734 * png_set_background_fixed seems to go wrong.
2735 */
2736 expand_tRNS = 1;
2737 png_set_background_fixed(png_ptr, &c,
2738 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2739 0/*gamma: not used*/);
2740 }
2741
2742 output_processing = PNG_CMAP_NONE;
2743 }
2744 }
2745
2746 else /* output is color */
2747 {
2748 /* We could use png_quantize here so long as there is no transparent
2749 * color or alpha; png_quantize ignores alpha. Easier overall just
2750 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2751 * Consequently we always want libpng to produce sRGB data.
2752 */
2753 data_encoding = P_sRGB;
2754
2755 /* Is there any transparency or alpha? */
2756 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2757 png_ptr->num_trans > 0)
2758 {
2759 /* Is there alpha in the output too? If so all four channels are
2760 * processed into a special RGB cube with alpha support.
2761 */
2762 if (output_format & PNG_FORMAT_FLAG_ALPHA)
2763 {
2764 png_uint_32 r;
2765
2766 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2767 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2768
2769 cmap_entries = make_rgb_colormap(display);
2770
2771 /* Add a transparent entry. */
2772 png_create_colormap_entry(display, cmap_entries, 255, 255,
2773 255, 0, P_sRGB);
2774
2775 /* This is stored as the background index for the processing
2776 * algorithm.
2777 */
2778 background_index = cmap_entries++;
2779
2780 /* Add 27 r,g,b entries each with alpha 0.5. */
2781 for (r=0; r<256; r = (r << 1) | 0x7f)
2782 {
2783 png_uint_32 g;
2784
2785 for (g=0; g<256; g = (g << 1) | 0x7f)
2786 {
2787 png_uint_32 b;
2788
2789 /* This generates components with the values 0, 127 and
2790 * 255
2791 */
2792 for (b=0; b<256; b = (b << 1) | 0x7f)
2793 png_create_colormap_entry(display, cmap_entries++,
2794 r, g, b, 128, P_sRGB);
2795 }
2796 }
2797
2798 expand_tRNS = 1;
2799 output_processing = PNG_CMAP_RGB_ALPHA;
2800 }
2801
2802 else
2803 {
2804 /* Alpha/transparency must be removed. The background must
2805 * exist in the color map (achieved by setting adding it after
2806 * the 666 color-map). If the standard processing code will
2807 * pick up this entry automatically that's all that is
2808 * required; libpng can be called to do the background
2809 * processing.
2810 */
2811 unsigned int sample_size =
2812 PNG_IMAGE_SAMPLE_SIZE(output_format);
2813 png_uint_32 r, g, b; /* sRGB background */
2814
2815 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2816 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2817
2818 cmap_entries = make_rgb_colormap(display);
2819
2820 png_create_colormap_entry(display, cmap_entries, back_r,
2821 back_g, back_b, 0/*unused*/, output_encoding);
2822
2823 if (output_encoding == P_LINEAR)
2824 {
2825 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2826 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2827 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2828 }
2829
2830 else
2831 {
2832 r = back_r;
2833 g = back_g;
2834 b = back_g;
2835 }
2836
2837 /* Compare the newly-created color-map entry with the one the
2838 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2839 * match, add the new one and set this as the background
2840 * index.
2841 */
2842 if (memcmp((png_const_bytep)display->colormap +
2843 sample_size * cmap_entries,
2844 (png_const_bytep)display->colormap +
2845 sample_size * PNG_RGB_INDEX(r,g,b),
2846 sample_size) != 0)
2847 {
2848 /* The background color must be added. */
2849 background_index = cmap_entries++;
2850
2851 /* Add 27 r,g,b entries each with created by composing with
2852 * the background at alpha 0.5.
2853 */
2854 for (r=0; r<256; r = (r << 1) | 0x7f)
2855 {
2856 for (g=0; g<256; g = (g << 1) | 0x7f)
2857 {
2858 /* This generates components with the values 0, 127
2859 * and 255
2860 */
2861 for (b=0; b<256; b = (b << 1) | 0x7f)
2862 png_create_colormap_entry(display, cmap_entries++,
2863 png_colormap_compose(display, r, P_sRGB, 128,
2864 back_r, output_encoding),
2865 png_colormap_compose(display, g, P_sRGB, 128,
2866 back_g, output_encoding),
2867 png_colormap_compose(display, b, P_sRGB, 128,
2868 back_b, output_encoding),
2869 0/*unused*/, output_encoding);
2870 }
2871 }
2872
2873 expand_tRNS = 1;
2874 output_processing = PNG_CMAP_RGB_ALPHA;
2875 }
2876
2877 else /* background color is in the standard color-map */
2878 {
2879 png_color_16 c;
2880
2881 c.index = 0; /*unused*/
2882 c.red = (png_uint_16)back_r;
2883 c.gray = c.green = (png_uint_16)back_g;
2884 c.blue = (png_uint_16)back_b;
2885
2886 png_set_background_fixed(png_ptr, &c,
2887 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2888 0/*gamma: not used*/);
2889
2890 output_processing = PNG_CMAP_RGB;
2891 }
2892 }
2893 }
2894
2895 else /* no alpha or transparency in the input */
2896 {
2897 /* Alpha in the output is irrelevant, simply map the opaque input
2898 * pixels to the 6x6x6 color-map.
2899 */
2900 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2901 png_error(png_ptr, "rgb color-map: too few entries");
2902
2903 cmap_entries = make_rgb_colormap(display);
2904 output_processing = PNG_CMAP_RGB;
2905 }
2906 }
2907 break;
2908
2909 case PNG_COLOR_TYPE_PALETTE:
2910 /* It's already got a color-map. It may be necessary to eliminate the
2911 * tRNS entries though.
2912 */
2913 {
2914 unsigned int num_trans = png_ptr->num_trans;
2915 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2916 png_const_colorp colormap = png_ptr->palette;
2917 const int do_background = trans != NULL &&
2918 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2919 unsigned int i;
2920
2921 /* Just in case: */
2922 if (trans == NULL)
2923 num_trans = 0;
2924
2925 output_processing = PNG_CMAP_NONE;
2926 data_encoding = P_FILE; /* Don't change from color-map indicies */
2927 cmap_entries = png_ptr->num_palette;
2928 if (cmap_entries > 256)
2929 cmap_entries = 256;
2930
2931 if (cmap_entries > image->colormap_entries)
2932 png_error(png_ptr, "palette color-map: too few entries");
2933
2934 for (i=0; i < cmap_entries; ++i)
2935 {
2936 if (do_background && i < num_trans && trans[i] < 255)
2937 {
2938 if (trans[i] == 0)
2939 png_create_colormap_entry(display, i, back_r, back_g,
2940 back_b, 0, output_encoding);
2941
2942 else
2943 {
2944 /* Must compose the PNG file color in the color-map entry
2945 * on the sRGB color in 'back'.
2946 */
2947 png_create_colormap_entry(display, i,
2948 png_colormap_compose(display, colormap[i].red, P_FILE,
2949 trans[i], back_r, output_encoding),
2950 png_colormap_compose(display, colormap[i].green, P_FILE,
2951 trans[i], back_g, output_encoding),
2952 png_colormap_compose(display, colormap[i].blue, P_FILE,
2953 trans[i], back_b, output_encoding),
2954 output_encoding == P_LINEAR ? trans[i] * 257U :
2955 trans[i],
2956 output_encoding);
2957 }
2958 }
2959
2960 else
2961 png_create_colormap_entry(display, i, colormap[i].red,
2962 colormap[i].green, colormap[i].blue,
2963 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2964 }
2965
2966 /* The PNG data may have indicies packed in fewer than 8 bits, it
2967 * must be expanded if so.
2968 */
2969 if (png_ptr->bit_depth < 8)
2970 png_set_packing(png_ptr);
2971 }
2972 break;
2973
2974 default:
2975 png_error(png_ptr, "invalid PNG color type");
2976 /*NOT REACHED*/
2977 break;
2978 }
2979
2980 /* Now deal with the output processing */
2981 if (expand_tRNS && png_ptr->num_trans > 0 &&
2982 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2983 png_set_tRNS_to_alpha(png_ptr);
2984
2985 switch (data_encoding)
2986 {
2987 default:
2988 png_error(png_ptr, "bad data option (internal error)");
2989 break;
2990
2991 case P_sRGB:
2992 /* Change to 8-bit sRGB */
2993 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2994 /* FALL THROUGH */
2995
2996 case P_FILE:
2997 if (png_ptr->bit_depth > 8)
2998 png_set_scale_16(png_ptr);
2999 break;
3000 }
3001
3002 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
3003 png_error(png_ptr, "color map overflow (BAD internal error)");
3004
3005 image->colormap_entries = cmap_entries;
3006
3007 /* Double check using the recorded background index */
3008 switch (output_processing)
3009 {
3010 case PNG_CMAP_NONE:
3011 if (background_index != PNG_CMAP_NONE_BACKGROUND)
3012 goto bad_background;
3013 break;
3014
3015 case PNG_CMAP_GA:
3016 if (background_index != PNG_CMAP_GA_BACKGROUND)
3017 goto bad_background;
3018 break;
3019
3020 case PNG_CMAP_TRANS:
3021 if (background_index >= cmap_entries ||
3022 background_index != PNG_CMAP_TRANS_BACKGROUND)
3023 goto bad_background;
3024 break;
3025
3026 case PNG_CMAP_RGB:
3027 if (background_index != PNG_CMAP_RGB_BACKGROUND)
3028 goto bad_background;
3029 break;
3030
3031 case PNG_CMAP_RGB_ALPHA:
3032 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
3033 goto bad_background;
3034 break;
3035
3036 default:
3037 png_error(png_ptr, "bad processing option (internal error)");
3038
3039 bad_background:
3040 png_error(png_ptr, "bad background index (internal error)");
3041 }
3042
3043 display->colormap_processing = output_processing;
3044
3045 return 1/*ok*/;
3046 }
3047
3048 /* The final part of the color-map read called from png_image_finish_read. */
3049 static int
png_image_read_and_map(png_voidp argument)3050 png_image_read_and_map(png_voidp argument)
3051 {
3052 png_image_read_control *display = png_voidcast(png_image_read_control*,
3053 argument);
3054 png_imagep image = display->image;
3055 png_structrp png_ptr = image->opaque->png_ptr;
3056 int passes;
3057
3058 /* Called when the libpng data must be transformed into the color-mapped
3059 * form. There is a local row buffer in display->local and this routine must
3060 * do the interlace handling.
3061 */
3062 switch (png_ptr->interlaced)
3063 {
3064 case PNG_INTERLACE_NONE:
3065 passes = 1;
3066 break;
3067
3068 case PNG_INTERLACE_ADAM7:
3069 passes = PNG_INTERLACE_ADAM7_PASSES;
3070 break;
3071
3072 default:
3073 png_error(png_ptr, "unknown interlace type");
3074 }
3075
3076 {
3077 png_uint_32 height = image->height;
3078 png_uint_32 width = image->width;
3079 int proc = display->colormap_processing;
3080 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3081 ptrdiff_t step_row = display->row_bytes;
3082 int pass;
3083
3084 for (pass = 0; pass < passes; ++pass)
3085 {
3086 unsigned int startx, stepx, stepy;
3087 png_uint_32 y;
3088
3089 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3090 {
3091 /* The row may be empty for a short image: */
3092 if (PNG_PASS_COLS(width, pass) == 0)
3093 continue;
3094
3095 startx = PNG_PASS_START_COL(pass);
3096 stepx = PNG_PASS_COL_OFFSET(pass);
3097 y = PNG_PASS_START_ROW(pass);
3098 stepy = PNG_PASS_ROW_OFFSET(pass);
3099 }
3100
3101 else
3102 {
3103 y = 0;
3104 startx = 0;
3105 stepx = stepy = 1;
3106 }
3107
3108 for (; y<height; y += stepy)
3109 {
3110 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3111 png_bytep outrow = first_row + y * step_row;
3112 png_const_bytep end_row = outrow + width;
3113
3114 /* Read read the libpng data into the temporary buffer. */
3115 png_read_row(png_ptr, inrow, NULL);
3116
3117 /* Now process the row according to the processing option, note
3118 * that the caller verifies that the format of the libpng output
3119 * data is as required.
3120 */
3121 outrow += startx;
3122 switch (proc)
3123 {
3124 case PNG_CMAP_GA:
3125 for (; outrow < end_row; outrow += stepx)
3126 {
3127 /* The data is always in the PNG order */
3128 unsigned int gray = *inrow++;
3129 unsigned int alpha = *inrow++;
3130 unsigned int entry;
3131
3132 /* NOTE: this code is copied as a comment in
3133 * make_ga_colormap above. Please update the
3134 * comment if you change this code!
3135 */
3136 if (alpha > 229) /* opaque */
3137 {
3138 entry = (231 * gray + 128) >> 8;
3139 }
3140 else if (alpha < 26) /* transparent */
3141 {
3142 entry = 231;
3143 }
3144 else /* partially opaque */
3145 {
3146 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3147 }
3148
3149 *outrow = (png_byte)entry;
3150 }
3151 break;
3152
3153 case PNG_CMAP_TRANS:
3154 for (; outrow < end_row; outrow += stepx)
3155 {
3156 png_byte gray = *inrow++;
3157 png_byte alpha = *inrow++;
3158
3159 if (alpha == 0)
3160 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3161
3162 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3163 *outrow = gray;
3164
3165 else
3166 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3167 }
3168 break;
3169
3170 case PNG_CMAP_RGB:
3171 for (; outrow < end_row; outrow += stepx)
3172 {
3173 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3174 inrow += 3;
3175 }
3176 break;
3177
3178 case PNG_CMAP_RGB_ALPHA:
3179 for (; outrow < end_row; outrow += stepx)
3180 {
3181 unsigned int alpha = inrow[3];
3182
3183 /* Because the alpha entries only hold alpha==0.5 values
3184 * split the processing at alpha==0.25 (64) and 0.75
3185 * (196).
3186 */
3187
3188 if (alpha >= 196)
3189 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3190 inrow[2]);
3191
3192 else if (alpha < 64)
3193 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3194
3195 else
3196 {
3197 /* Likewise there are three entries for each of r, g
3198 * and b. We could select the entry by popcount on
3199 * the top two bits on those architectures that
3200 * support it, this is what the code below does,
3201 * crudely.
3202 */
3203 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3204
3205 /* Here are how the values map:
3206 *
3207 * 0x00 .. 0x3f -> 0
3208 * 0x40 .. 0xbf -> 1
3209 * 0xc0 .. 0xff -> 2
3210 *
3211 * So, as above with the explicit alpha checks, the
3212 * breakpoints are at 64 and 196.
3213 */
3214 if (inrow[0] & 0x80) back_i += 9; /* red */
3215 if (inrow[0] & 0x40) back_i += 9;
3216 if (inrow[0] & 0x80) back_i += 3; /* green */
3217 if (inrow[0] & 0x40) back_i += 3;
3218 if (inrow[0] & 0x80) back_i += 1; /* blue */
3219 if (inrow[0] & 0x40) back_i += 1;
3220
3221 *outrow = (png_byte)back_i;
3222 }
3223
3224 inrow += 4;
3225 }
3226 break;
3227
3228 default:
3229 break;
3230 }
3231 }
3232 }
3233 }
3234
3235 return 1;
3236 }
3237
3238 static int
png_image_read_colormapped(png_voidp argument)3239 png_image_read_colormapped(png_voidp argument)
3240 {
3241 png_image_read_control *display = png_voidcast(png_image_read_control*,
3242 argument);
3243 png_imagep image = display->image;
3244 png_controlp control = image->opaque;
3245 png_structrp png_ptr = control->png_ptr;
3246 png_inforp info_ptr = control->info_ptr;
3247
3248 int passes = 0; /* As a flag */
3249
3250 PNG_SKIP_CHUNKS(png_ptr);
3251
3252 /* Update the 'info' structure and make sure the result is as required; first
3253 * make sure to turn on the interlace handling if it will be required
3254 * (because it can't be turned on *after* the call to png_read_update_info!)
3255 */
3256 if (display->colormap_processing == PNG_CMAP_NONE)
3257 passes = png_set_interlace_handling(png_ptr);
3258
3259 png_read_update_info(png_ptr, info_ptr);
3260
3261 /* The expected output can be deduced from the colormap_processing option. */
3262 switch (display->colormap_processing)
3263 {
3264 case PNG_CMAP_NONE:
3265 /* Output must be one channel and one byte per pixel, the output
3266 * encoding can be anything.
3267 */
3268 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3269 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3270 info_ptr->bit_depth == 8)
3271 break;
3272
3273 goto bad_output;
3274
3275 case PNG_CMAP_TRANS:
3276 case PNG_CMAP_GA:
3277 /* Output must be two channels and the 'G' one must be sRGB, the latter
3278 * can be checked with an exact number because it should have been set
3279 * to this number above!
3280 */
3281 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3282 info_ptr->bit_depth == 8 &&
3283 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3284 image->colormap_entries == 256)
3285 break;
3286
3287 goto bad_output;
3288
3289 case PNG_CMAP_RGB:
3290 /* Output must be 8-bit sRGB encoded RGB */
3291 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3292 info_ptr->bit_depth == 8 &&
3293 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3294 image->colormap_entries == 216)
3295 break;
3296
3297 goto bad_output;
3298
3299 case PNG_CMAP_RGB_ALPHA:
3300 /* Output must be 8-bit sRGB encoded RGBA */
3301 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3302 info_ptr->bit_depth == 8 &&
3303 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3304 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3305 break;
3306
3307 /* goto bad_output; */
3308 /* FALL THROUGH */
3309
3310 default:
3311 bad_output:
3312 png_error(png_ptr, "bad color-map processing (internal error)");
3313 }
3314
3315 /* Now read the rows. Do this here if it is possible to read directly into
3316 * the output buffer, otherwise allocate a local row buffer of the maximum
3317 * size libpng requires and call the relevant processing routine safely.
3318 */
3319 {
3320 png_voidp first_row = display->buffer;
3321 ptrdiff_t row_bytes = display->row_stride;
3322
3323 /* The following expression is designed to work correctly whether it gives
3324 * a signed or an unsigned result.
3325 */
3326 if (row_bytes < 0)
3327 {
3328 char *ptr = png_voidcast(char*, first_row);
3329 ptr += (image->height-1) * (-row_bytes);
3330 first_row = png_voidcast(png_voidp, ptr);
3331 }
3332
3333 display->first_row = first_row;
3334 display->row_bytes = row_bytes;
3335 }
3336
3337 if (passes == 0)
3338 {
3339 int result;
3340 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3341
3342 display->local_row = row;
3343 result = png_safe_execute(image, png_image_read_and_map, display);
3344 display->local_row = NULL;
3345 png_free(png_ptr, row);
3346
3347 return result;
3348 }
3349
3350 else
3351 {
3352 png_alloc_size_t row_bytes = display->row_bytes;
3353
3354 while (--passes >= 0)
3355 {
3356 png_uint_32 y = image->height;
3357 png_bytep row = png_voidcast(png_bytep, display->first_row);
3358
3359 while (y-- > 0)
3360 {
3361 png_read_row(png_ptr, row, NULL);
3362 row += row_bytes;
3363 }
3364 }
3365
3366 return 1;
3367 }
3368 }
3369
3370 /* Just the row reading part of png_image_read. */
3371 static int
png_image_read_composite(png_voidp argument)3372 png_image_read_composite(png_voidp argument)
3373 {
3374 png_image_read_control *display = png_voidcast(png_image_read_control*,
3375 argument);
3376 png_imagep image = display->image;
3377 png_structrp png_ptr = image->opaque->png_ptr;
3378 int passes;
3379
3380 switch (png_ptr->interlaced)
3381 {
3382 case PNG_INTERLACE_NONE:
3383 passes = 1;
3384 break;
3385
3386 case PNG_INTERLACE_ADAM7:
3387 passes = PNG_INTERLACE_ADAM7_PASSES;
3388 break;
3389
3390 default:
3391 png_error(png_ptr, "unknown interlace type");
3392 }
3393
3394 {
3395 png_uint_32 height = image->height;
3396 png_uint_32 width = image->width;
3397 ptrdiff_t step_row = display->row_bytes;
3398 unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
3399 int pass;
3400
3401 for (pass = 0; pass < passes; ++pass)
3402 {
3403 unsigned int startx, stepx, stepy;
3404 png_uint_32 y;
3405
3406 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3407 {
3408 /* The row may be empty for a short image: */
3409 if (PNG_PASS_COLS(width, pass) == 0)
3410 continue;
3411
3412 startx = PNG_PASS_START_COL(pass) * channels;
3413 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3414 y = PNG_PASS_START_ROW(pass);
3415 stepy = PNG_PASS_ROW_OFFSET(pass);
3416 }
3417
3418 else
3419 {
3420 y = 0;
3421 startx = 0;
3422 stepx = channels;
3423 stepy = 1;
3424 }
3425
3426 for (; y<height; y += stepy)
3427 {
3428 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3429 png_bytep outrow;
3430 png_const_bytep end_row;
3431
3432 /* Read the row, which is packed: */
3433 png_read_row(png_ptr, inrow, NULL);
3434
3435 outrow = png_voidcast(png_bytep, display->first_row);
3436 outrow += y * step_row;
3437 end_row = outrow + width * channels;
3438
3439 /* Now do the composition on each pixel in this row. */
3440 outrow += startx;
3441 for (; outrow < end_row; outrow += stepx)
3442 {
3443 png_byte alpha = inrow[channels];
3444
3445 if (alpha > 0) /* else no change to the output */
3446 {
3447 unsigned int c;
3448
3449 for (c=0; c<channels; ++c)
3450 {
3451 png_uint_32 component = inrow[c];
3452
3453 if (alpha < 255) /* else just use component */
3454 {
3455 /* This is PNG_OPTIMIZED_ALPHA, the component value
3456 * is a linear 8-bit value. Combine this with the
3457 * current outrow[c] value which is sRGB encoded.
3458 * Arithmetic here is 16-bits to preserve the output
3459 * values correctly.
3460 */
3461 component *= 257*255; /* =65535 */
3462 component += (255-alpha)*png_sRGB_table[outrow[c]];
3463
3464 /* So 'component' is scaled by 255*65535 and is
3465 * therefore appropriate for the sRGB to linear
3466 * conversion table.
3467 */
3468 component = PNG_sRGB_FROM_LINEAR(component);
3469 }
3470
3471 outrow[c] = (png_byte)component;
3472 }
3473 }
3474
3475 inrow += channels+1; /* components and alpha channel */
3476 }
3477 }
3478 }
3479 }
3480
3481 return 1;
3482 }
3483
3484 /* The do_local_background case; called when all the following transforms are to
3485 * be done:
3486 *
3487 * PNG_RGB_TO_GRAY
3488 * PNG_COMPOSITE
3489 * PNG_GAMMA
3490 *
3491 * This is a work-round for the fact that both the PNG_RGB_TO_GRAY and
3492 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3493 * correction. The fix-up is to prevent the PNG_COMPOSITE operation happening
3494 * inside libpng, so this routine sees an 8 or 16-bit gray+alpha row and handles
3495 * the removal or pre-multiplication of the alpha channel.
3496 */
3497 static int
png_image_read_background(png_voidp argument)3498 png_image_read_background(png_voidp argument)
3499 {
3500 png_image_read_control *display = png_voidcast(png_image_read_control*,
3501 argument);
3502 png_imagep image = display->image;
3503 png_structrp png_ptr = image->opaque->png_ptr;
3504 png_inforp info_ptr = image->opaque->info_ptr;
3505 png_uint_32 height = image->height;
3506 png_uint_32 width = image->width;
3507 int pass, passes;
3508
3509 /* Double check the convoluted logic below. We expect to get here with
3510 * libpng doing rgb to gray and gamma correction but background processing
3511 * left to the png_image_read_background function. The rows libpng produce
3512 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3513 */
3514 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3515 png_error(png_ptr, "lost rgb to gray");
3516
3517 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3518 png_error(png_ptr, "unexpected compose");
3519
3520 if (png_get_channels(png_ptr, info_ptr) != 2)
3521 png_error(png_ptr, "lost/gained channels");
3522
3523 /* Expect the 8-bit case to always remove the alpha channel */
3524 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3525 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3526 png_error(png_ptr, "unexpected 8-bit transformation");
3527
3528 switch (png_ptr->interlaced)
3529 {
3530 case PNG_INTERLACE_NONE:
3531 passes = 1;
3532 break;
3533
3534 case PNG_INTERLACE_ADAM7:
3535 passes = PNG_INTERLACE_ADAM7_PASSES;
3536 break;
3537
3538 default:
3539 png_error(png_ptr, "unknown interlace type");
3540 }
3541
3542 /* Use direct access to info_ptr here because otherwise the simplified API
3543 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3544 * checking the value after libpng expansions, not the original value in the
3545 * PNG.
3546 */
3547 switch (info_ptr->bit_depth)
3548 {
3549 default:
3550 png_error(png_ptr, "unexpected bit depth");
3551 break;
3552
3553 case 8:
3554 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3555 * to be removed by composing on a background: either the row if
3556 * display->background is NULL or display->background->green if not.
3557 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3558 */
3559 {
3560 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3561 ptrdiff_t step_row = display->row_bytes;
3562
3563 for (pass = 0; pass < passes; ++pass)
3564 {
3565 png_bytep row = png_voidcast(png_bytep,
3566 display->first_row);
3567 unsigned int startx, stepx, stepy;
3568 png_uint_32 y;
3569
3570 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3571 {
3572 /* The row may be empty for a short image: */
3573 if (PNG_PASS_COLS(width, pass) == 0)
3574 continue;
3575
3576 startx = PNG_PASS_START_COL(pass);
3577 stepx = PNG_PASS_COL_OFFSET(pass);
3578 y = PNG_PASS_START_ROW(pass);
3579 stepy = PNG_PASS_ROW_OFFSET(pass);
3580 }
3581
3582 else
3583 {
3584 y = 0;
3585 startx = 0;
3586 stepx = stepy = 1;
3587 }
3588
3589 if (display->background == NULL)
3590 {
3591 for (; y<height; y += stepy)
3592 {
3593 png_bytep inrow = png_voidcast(png_bytep,
3594 display->local_row);
3595 png_bytep outrow = first_row + y * step_row;
3596 png_const_bytep end_row = outrow + width;
3597
3598 /* Read the row, which is packed: */
3599 png_read_row(png_ptr, inrow, NULL);
3600
3601 /* Now do the composition on each pixel in this row. */
3602 outrow += startx;
3603 for (; outrow < end_row; outrow += stepx)
3604 {
3605 png_byte alpha = inrow[1];
3606
3607 if (alpha > 0) /* else no change to the output */
3608 {
3609 png_uint_32 component = inrow[0];
3610
3611 if (alpha < 255) /* else just use component */
3612 {
3613 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3614 * necessary to invert the sRGB transfer
3615 * function and multiply the alpha out.
3616 */
3617 component = png_sRGB_table[component] * alpha;
3618 component += png_sRGB_table[outrow[0]] *
3619 (255-alpha);
3620 component = PNG_sRGB_FROM_LINEAR(component);
3621 }
3622
3623 outrow[0] = (png_byte)component;
3624 }
3625
3626 inrow += 2; /* gray and alpha channel */
3627 }
3628 }
3629 }
3630
3631 else /* constant background value */
3632 {
3633 png_byte background8 = display->background->green;
3634 png_uint_16 background = png_sRGB_table[background8];
3635
3636 for (; y<height; y += stepy)
3637 {
3638 png_bytep inrow = png_voidcast(png_bytep,
3639 display->local_row);
3640 png_bytep outrow = first_row + y * step_row;
3641 png_const_bytep end_row = outrow + width;
3642
3643 /* Read the row, which is packed: */
3644 png_read_row(png_ptr, inrow, NULL);
3645
3646 /* Now do the composition on each pixel in this row. */
3647 outrow += startx;
3648 for (; outrow < end_row; outrow += stepx)
3649 {
3650 png_byte alpha = inrow[1];
3651
3652 if (alpha > 0) /* else use background */
3653 {
3654 png_uint_32 component = inrow[0];
3655
3656 if (alpha < 255) /* else just use component */
3657 {
3658 component = png_sRGB_table[component] * alpha;
3659 component += background * (255-alpha);
3660 component = PNG_sRGB_FROM_LINEAR(component);
3661 }
3662
3663 outrow[0] = (png_byte)component;
3664 }
3665
3666 else
3667 outrow[0] = background8;
3668
3669 inrow += 2; /* gray and alpha channel */
3670 }
3671
3672 row += display->row_bytes;
3673 }
3674 }
3675 }
3676 }
3677 break;
3678
3679 case 16:
3680 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3681 * still be done and, maybe, the alpha channel removed. This code also
3682 * handles the alpha-first option.
3683 */
3684 {
3685 png_uint_16p first_row = png_voidcast(png_uint_16p,
3686 display->first_row);
3687 /* The division by two is safe because the caller passed in a
3688 * stride which was multiplied by 2 (below) to get row_bytes.
3689 */
3690 ptrdiff_t step_row = display->row_bytes / 2;
3691 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
3692 unsigned int outchannels = 1+preserve_alpha;
3693 int swap_alpha = 0;
3694
3695 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3696 if (preserve_alpha && (image->format & PNG_FORMAT_FLAG_AFIRST))
3697 swap_alpha = 1;
3698 # endif
3699
3700 for (pass = 0; pass < passes; ++pass)
3701 {
3702 unsigned int startx, stepx, stepy;
3703 png_uint_32 y;
3704
3705 /* The 'x' start and step are adjusted to output components here.
3706 */
3707 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3708 {
3709 /* The row may be empty for a short image: */
3710 if (PNG_PASS_COLS(width, pass) == 0)
3711 continue;
3712
3713 startx = PNG_PASS_START_COL(pass) * outchannels;
3714 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3715 y = PNG_PASS_START_ROW(pass);
3716 stepy = PNG_PASS_ROW_OFFSET(pass);
3717 }
3718
3719 else
3720 {
3721 y = 0;
3722 startx = 0;
3723 stepx = outchannels;
3724 stepy = 1;
3725 }
3726
3727 for (; y<height; y += stepy)
3728 {
3729 png_const_uint_16p inrow;
3730 png_uint_16p outrow = first_row + y*step_row;
3731 png_uint_16p end_row = outrow + width * outchannels;
3732
3733 /* Read the row, which is packed: */
3734 png_read_row(png_ptr, png_voidcast(png_bytep,
3735 display->local_row), NULL);
3736 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3737
3738 /* Now do the pre-multiplication on each pixel in this row.
3739 */
3740 outrow += startx;
3741 for (; outrow < end_row; outrow += stepx)
3742 {
3743 png_uint_32 component = inrow[0];
3744 png_uint_16 alpha = inrow[1];
3745
3746 if (alpha > 0) /* else 0 */
3747 {
3748 if (alpha < 65535) /* else just use component */
3749 {
3750 component *= alpha;
3751 component += 32767;
3752 component /= 65535;
3753 }
3754 }
3755
3756 else
3757 component = 0;
3758
3759 outrow[swap_alpha] = (png_uint_16)component;
3760 if (preserve_alpha)
3761 outrow[1 ^ swap_alpha] = alpha;
3762
3763 inrow += 2; /* components and alpha channel */
3764 }
3765 }
3766 }
3767 }
3768 break;
3769 }
3770
3771 return 1;
3772 }
3773
3774 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3775 static int
png_image_read_direct(png_voidp argument)3776 png_image_read_direct(png_voidp argument)
3777 {
3778 png_image_read_control *display = png_voidcast(png_image_read_control*,
3779 argument);
3780 png_imagep image = display->image;
3781 png_structrp png_ptr = image->opaque->png_ptr;
3782 png_inforp info_ptr = image->opaque->info_ptr;
3783
3784 png_uint_32 format = image->format;
3785 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3786 int do_local_compose = 0;
3787 int do_local_background = 0; /* to avoid double gamma correction bug */
3788 int passes = 0;
3789
3790 /* Add transforms to ensure the correct output format is produced then check
3791 * that the required implementation support is there. Always expand; always
3792 * need 8 bits minimum, no palette and expanded tRNS.
3793 */
3794 png_set_expand(png_ptr);
3795
3796 /* Now check the format to see if it was modified. */
3797 {
3798 png_uint_32 base_format = png_image_format(png_ptr) &
3799 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3800 png_uint_32 change = format ^ base_format;
3801 png_fixed_point output_gamma;
3802 int mode; /* alpha mode */
3803
3804 /* Do this first so that we have a record if rgb to gray is happening. */
3805 if (change & PNG_FORMAT_FLAG_COLOR)
3806 {
3807 /* gray<->color transformation required. */
3808 if (format & PNG_FORMAT_FLAG_COLOR)
3809 png_set_gray_to_rgb(png_ptr);
3810
3811 else
3812 {
3813 /* libpng can't do both rgb to gray and
3814 * background/pre-multiplication if there is also significant gamma
3815 * correction, because both operations require linear colors and
3816 * the code only supports one transform doing the gamma correction.
3817 * Handle this by doing the pre-multiplication or background
3818 * operation in this code, if necessary.
3819 *
3820 * TODO: fix this by rewriting pngrtran.c (!)
3821 *
3822 * For the moment (given that fixing this in pngrtran.c is an
3823 * enormous change) 'do_local_background' is used to indicate that
3824 * the problem exists.
3825 */
3826 if (base_format & PNG_FORMAT_FLAG_ALPHA)
3827 do_local_background = 1/*maybe*/;
3828
3829 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3830 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3831 }
3832
3833 change &= ~PNG_FORMAT_FLAG_COLOR;
3834 }
3835
3836 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3837 */
3838 {
3839 png_fixed_point input_gamma_default;
3840
3841 if ((base_format & PNG_FORMAT_FLAG_LINEAR) &&
3842 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3843 input_gamma_default = PNG_GAMMA_LINEAR;
3844 else
3845 input_gamma_default = PNG_DEFAULT_sRGB;
3846
3847 /* Call png_set_alpha_mode to set the default for the input gamma; the
3848 * output gamma is set by a second call below.
3849 */
3850 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3851 }
3852
3853 if (linear)
3854 {
3855 /* If there *is* an alpha channel in the input it must be multiplied
3856 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3857 */
3858 if (base_format & PNG_FORMAT_FLAG_ALPHA)
3859 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3860
3861 else
3862 mode = PNG_ALPHA_PNG;
3863
3864 output_gamma = PNG_GAMMA_LINEAR;
3865 }
3866
3867 else
3868 {
3869 mode = PNG_ALPHA_PNG;
3870 output_gamma = PNG_DEFAULT_sRGB;
3871 }
3872
3873 /* If 'do_local_background' is set check for the presence of gamma
3874 * correction; this is part of the work-round for the libpng bug
3875 * described above.
3876 *
3877 * TODO: fix libpng and remove this.
3878 */
3879 if (do_local_background)
3880 {
3881 png_fixed_point gtest;
3882
3883 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3884 * gamma correction, the screen gamma hasn't been set on png_struct
3885 * yet; it's set below. png_struct::gamma, however, is set to the
3886 * final value.
3887 */
3888 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3889 PNG_FP_1) && !png_gamma_significant(gtest))
3890 do_local_background = 0;
3891
3892 else if (mode == PNG_ALPHA_STANDARD)
3893 {
3894 do_local_background = 2/*required*/;
3895 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3896 }
3897
3898 /* else leave as 1 for the checks below */
3899 }
3900
3901 /* If the bit-depth changes then handle that here. */
3902 if (change & PNG_FORMAT_FLAG_LINEAR)
3903 {
3904 if (linear /*16-bit output*/)
3905 png_set_expand_16(png_ptr);
3906
3907 else /* 8-bit output */
3908 png_set_scale_16(png_ptr);
3909
3910 change &= ~PNG_FORMAT_FLAG_LINEAR;
3911 }
3912
3913 /* Now the background/alpha channel changes. */
3914 if (change & PNG_FORMAT_FLAG_ALPHA)
3915 {
3916 /* Removing an alpha channel requires composition for the 8-bit
3917 * formats; for the 16-bit it is already done, above, by the
3918 * pre-multiplication and the channel just needs to be stripped.
3919 */
3920 if (base_format & PNG_FORMAT_FLAG_ALPHA)
3921 {
3922 /* If RGB->gray is happening the alpha channel must be left and the
3923 * operation completed locally.
3924 *
3925 * TODO: fix libpng and remove this.
3926 */
3927 if (do_local_background)
3928 do_local_background = 2/*required*/;
3929
3930 /* 16-bit output: just remove the channel */
3931 else if (linear) /* compose on black (well, pre-multiply) */
3932 png_set_strip_alpha(png_ptr);
3933
3934 /* 8-bit output: do an appropriate compose */
3935 else if (display->background != NULL)
3936 {
3937 png_color_16 c;
3938
3939 c.index = 0; /*unused*/
3940 c.red = display->background->red;
3941 c.green = display->background->green;
3942 c.blue = display->background->blue;
3943 c.gray = display->background->green;
3944
3945 /* This is always an 8-bit sRGB value, using the 'green' channel
3946 * for gray is much better than calculating the luminance here;
3947 * we can get off-by-one errors in that calculation relative to
3948 * the app expectations and that will show up in transparent
3949 * pixels.
3950 */
3951 png_set_background_fixed(png_ptr, &c,
3952 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3953 0/*gamma: not used*/);
3954 }
3955
3956 else /* compose on row: implemented below. */
3957 {
3958 do_local_compose = 1;
3959 /* This leaves the alpha channel in the output, so it has to be
3960 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3961 * one so the code only has to hack on the pixels that require
3962 * composition.
3963 */
3964 mode = PNG_ALPHA_OPTIMIZED;
3965 }
3966 }
3967
3968 else /* output needs an alpha channel */
3969 {
3970 /* This is tricky because it happens before the swap operation has
3971 * been accomplished; however, the swap does *not* swap the added
3972 * alpha channel (weird API), so it must be added in the correct
3973 * place.
3974 */
3975 png_uint_32 filler; /* opaque filler */
3976 int where;
3977
3978 if (linear)
3979 filler = 65535;
3980
3981 else
3982 filler = 255;
3983
3984 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3985 if (format & PNG_FORMAT_FLAG_AFIRST)
3986 {
3987 where = PNG_FILLER_BEFORE;
3988 change &= ~PNG_FORMAT_FLAG_AFIRST;
3989 }
3990
3991 else
3992 # endif
3993 where = PNG_FILLER_AFTER;
3994
3995 png_set_add_alpha(png_ptr, filler, where);
3996 }
3997
3998 /* This stops the (irrelevant) call to swap_alpha below. */
3999 change &= ~PNG_FORMAT_FLAG_ALPHA;
4000 }
4001
4002 /* Now set the alpha mode correctly; this is always done, even if there is
4003 * no alpha channel in either the input or the output because it correctly
4004 * sets the output gamma.
4005 */
4006 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
4007
4008 # ifdef PNG_FORMAT_BGR_SUPPORTED
4009 if (change & PNG_FORMAT_FLAG_BGR)
4010 {
4011 /* Check only the output format; PNG is never BGR; don't do this if
4012 * the output is gray, but fix up the 'format' value in that case.
4013 */
4014 if (format & PNG_FORMAT_FLAG_COLOR)
4015 png_set_bgr(png_ptr);
4016
4017 else
4018 format &= ~PNG_FORMAT_FLAG_BGR;
4019
4020 change &= ~PNG_FORMAT_FLAG_BGR;
4021 }
4022 # endif
4023
4024 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
4025 if (change & PNG_FORMAT_FLAG_AFIRST)
4026 {
4027 /* Only relevant if there is an alpha channel - it's particularly
4028 * important to handle this correctly because do_local_compose may
4029 * be set above and then libpng will keep the alpha channel for this
4030 * code to remove.
4031 */
4032 if (format & PNG_FORMAT_FLAG_ALPHA)
4033 {
4034 /* Disable this if doing a local background,
4035 * TODO: remove this when local background is no longer required.
4036 */
4037 if (do_local_background != 2)
4038 png_set_swap_alpha(png_ptr);
4039 }
4040
4041 else
4042 format &= ~PNG_FORMAT_FLAG_AFIRST;
4043
4044 change &= ~PNG_FORMAT_FLAG_AFIRST;
4045 }
4046 # endif
4047
4048 /* If the *output* is 16-bit then we need to check for a byte-swap on this
4049 * architecture.
4050 */
4051 if (linear)
4052 {
4053 PNG_CONST png_uint_16 le = 0x0001;
4054
4055 if (*(png_const_bytep)&le)
4056 png_set_swap(png_ptr);
4057 }
4058
4059 /* If change is not now 0 some transformation is missing - error out. */
4060 if (change)
4061 png_error(png_ptr, "png_read_image: unsupported transformation");
4062 }
4063
4064 PNG_SKIP_CHUNKS(png_ptr);
4065
4066 /* Update the 'info' structure and make sure the result is as required; first
4067 * make sure to turn on the interlace handling if it will be required
4068 * (because it can't be turned on *after* the call to png_read_update_info!)
4069 *
4070 * TODO: remove the do_local_background fixup below.
4071 */
4072 if (!do_local_compose && do_local_background != 2)
4073 passes = png_set_interlace_handling(png_ptr);
4074
4075 png_read_update_info(png_ptr, info_ptr);
4076
4077 {
4078 png_uint_32 info_format = 0;
4079
4080 if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
4081 info_format |= PNG_FORMAT_FLAG_COLOR;
4082
4083 if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
4084 {
4085 /* do_local_compose removes this channel below. */
4086 if (!do_local_compose)
4087 {
4088 /* do_local_background does the same if required. */
4089 if (do_local_background != 2 ||
4090 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
4091 info_format |= PNG_FORMAT_FLAG_ALPHA;
4092 }
4093 }
4094
4095 else if (do_local_compose) /* internal error */
4096 png_error(png_ptr, "png_image_read: alpha channel lost");
4097
4098 if (info_ptr->bit_depth == 16)
4099 info_format |= PNG_FORMAT_FLAG_LINEAR;
4100
4101 # ifdef PNG_FORMAT_BGR_SUPPORTED
4102 if (png_ptr->transformations & PNG_BGR)
4103 info_format |= PNG_FORMAT_FLAG_BGR;
4104 # endif
4105
4106 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
4107 if (do_local_background == 2)
4108 {
4109 if (format & PNG_FORMAT_FLAG_AFIRST)
4110 info_format |= PNG_FORMAT_FLAG_AFIRST;
4111 }
4112
4113 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
4114 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
4115 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
4116 {
4117 if (do_local_background == 2)
4118 png_error(png_ptr, "unexpected alpha swap transformation");
4119
4120 info_format |= PNG_FORMAT_FLAG_AFIRST;
4121 }
4122 # endif
4123
4124 /* This is actually an internal error. */
4125 if (info_format != format)
4126 png_error(png_ptr, "png_read_image: invalid transformations");
4127 }
4128
4129 /* Now read the rows. If do_local_compose is set then it is necessary to use
4130 * a local row buffer. The output will be GA, RGBA or BGRA and must be
4131 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
4132 * display acts as a flag.
4133 */
4134 {
4135 png_voidp first_row = display->buffer;
4136 ptrdiff_t row_bytes = display->row_stride;
4137
4138 if (linear)
4139 row_bytes *= 2;
4140
4141 /* The following expression is designed to work correctly whether it gives
4142 * a signed or an unsigned result.
4143 */
4144 if (row_bytes < 0)
4145 {
4146 char *ptr = png_voidcast(char*, first_row);
4147 ptr += (image->height-1) * (-row_bytes);
4148 first_row = png_voidcast(png_voidp, ptr);
4149 }
4150
4151 display->first_row = first_row;
4152 display->row_bytes = row_bytes;
4153 }
4154
4155 if (do_local_compose)
4156 {
4157 int result;
4158 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4159
4160 display->local_row = row;
4161 result = png_safe_execute(image, png_image_read_composite, display);
4162 display->local_row = NULL;
4163 png_free(png_ptr, row);
4164
4165 return result;
4166 }
4167
4168 else if (do_local_background == 2)
4169 {
4170 int result;
4171 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
4172
4173 display->local_row = row;
4174 result = png_safe_execute(image, png_image_read_background, display);
4175 display->local_row = NULL;
4176 png_free(png_ptr, row);
4177
4178 return result;
4179 }
4180
4181 else
4182 {
4183 png_alloc_size_t row_bytes = display->row_bytes;
4184
4185 while (--passes >= 0)
4186 {
4187 png_uint_32 y = image->height;
4188 png_bytep row = png_voidcast(png_bytep, display->first_row);
4189
4190 while (y-- > 0)
4191 {
4192 png_read_row(png_ptr, row, NULL);
4193 row += row_bytes;
4194 }
4195 }
4196
4197 return 1;
4198 }
4199 }
4200
4201 int PNGAPI
png_image_finish_read(png_imagep image,png_const_colorp background,void * buffer,png_int_32 row_stride,void * colormap)4202 png_image_finish_read(png_imagep image, png_const_colorp background,
4203 void *buffer, png_int_32 row_stride, void *colormap)
4204 {
4205 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4206 {
4207 png_uint_32 check;
4208
4209 if (row_stride == 0)
4210 row_stride = PNG_IMAGE_ROW_STRIDE(*image);
4211
4212 if (row_stride < 0)
4213 check = -row_stride;
4214
4215 else
4216 check = row_stride;
4217
4218 if (image->opaque != NULL && buffer != NULL &&
4219 check >= PNG_IMAGE_ROW_STRIDE(*image))
4220 {
4221 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4222 (image->colormap_entries > 0 && colormap != NULL))
4223 {
4224 int result;
4225 png_image_read_control display;
4226
4227 memset(&display, 0, (sizeof display));
4228 display.image = image;
4229 display.buffer = buffer;
4230 display.row_stride = row_stride;
4231 display.colormap = colormap;
4232 display.background = background;
4233 display.local_row = NULL;
4234
4235 /* Choose the correct 'end' routine; for the color-map case all the
4236 * setup has already been done.
4237 */
4238 if (image->format & PNG_FORMAT_FLAG_COLORMAP)
4239 result =
4240 png_safe_execute(image, png_image_read_colormap, &display) &&
4241 png_safe_execute(image, png_image_read_colormapped, &display);
4242
4243 else
4244 result =
4245 png_safe_execute(image, png_image_read_direct, &display);
4246
4247 png_image_free(image);
4248 return result;
4249 }
4250
4251 else
4252 return png_image_error(image,
4253 "png_image_finish_read[color-map]: no color-map");
4254 }
4255
4256 else
4257 return png_image_error(image,
4258 "png_image_finish_read: invalid argument");
4259 }
4260
4261 else if (image != NULL)
4262 return png_image_error(image,
4263 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4264
4265 return 0;
4266 }
4267
4268 #endif /* PNG_SIMPLIFIED_READ_SUPPORTED */
4269 #endif /* PNG_READ_SUPPORTED */
4270