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