1
2 /* pngread.c - read a PNG file
3 *
4 * Last changed in libpng 1.6.9 [February 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
78 return png_ptr;
79 }
80
81
82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83 /* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
90 */
91 void PNGAPI
png_read_info(png_structrp png_ptr,png_inforp info_ptr)92 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
93 {
94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
95 int keep;
96 #endif
97
98 png_debug(1, "in png_read_info");
99
100 if (png_ptr == NULL || info_ptr == NULL)
101 return;
102
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr, info_ptr);
105
106 for (;;)
107 {
108 png_uint_32 length = png_read_chunk_header(png_ptr);
109 png_uint_32 chunk_name = png_ptr->chunk_name;
110
111 /* IDAT logic needs to happen here to simplify getting the two flags
112 * right.
113 */
114 if (chunk_name == png_IDAT)
115 {
116 if (!(png_ptr->mode & PNG_HAVE_IHDR))
117 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
118
119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
120 !(png_ptr->mode & PNG_HAVE_PLTE))
121 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
122
123 else if (png_ptr->mode & PNG_AFTER_IDAT)
124 png_chunk_benign_error(png_ptr, "Too many IDATs found");
125
126 png_ptr->mode |= PNG_HAVE_IDAT;
127 }
128
129 else if (png_ptr->mode & PNG_HAVE_IDAT)
130 png_ptr->mode |= PNG_AFTER_IDAT;
131
132 /* This should be a binary subdivision search or a hash for
133 * matching the chunk name rather than a linear search.
134 */
135 if (chunk_name == png_IHDR)
136 png_handle_IHDR(png_ptr, info_ptr, length);
137
138 else if (chunk_name == png_IEND)
139 png_handle_IEND(png_ptr, info_ptr, length);
140
141 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
142 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
143 {
144 png_handle_unknown(png_ptr, info_ptr, length, keep);
145
146 if (chunk_name == png_PLTE)
147 png_ptr->mode |= PNG_HAVE_PLTE;
148
149 else if (chunk_name == png_IDAT)
150 {
151 png_ptr->idat_size = 0; /* It has been consumed */
152 break;
153 }
154 }
155 #endif
156 else if (chunk_name == png_PLTE)
157 png_handle_PLTE(png_ptr, info_ptr, length);
158
159 else if (chunk_name == png_IDAT)
160 {
161 png_ptr->idat_size = length;
162 break;
163 }
164
165 #ifdef PNG_READ_bKGD_SUPPORTED
166 else if (chunk_name == png_bKGD)
167 png_handle_bKGD(png_ptr, info_ptr, length);
168 #endif
169
170 #ifdef PNG_READ_cHRM_SUPPORTED
171 else if (chunk_name == png_cHRM)
172 png_handle_cHRM(png_ptr, info_ptr, length);
173 #endif
174
175 #ifdef PNG_READ_gAMA_SUPPORTED
176 else if (chunk_name == png_gAMA)
177 png_handle_gAMA(png_ptr, info_ptr, length);
178 #endif
179
180 #ifdef PNG_READ_hIST_SUPPORTED
181 else if (chunk_name == png_hIST)
182 png_handle_hIST(png_ptr, info_ptr, length);
183 #endif
184
185 #ifdef PNG_READ_oFFs_SUPPORTED
186 else if (chunk_name == png_oFFs)
187 png_handle_oFFs(png_ptr, info_ptr, length);
188 #endif
189
190 #ifdef PNG_READ_pCAL_SUPPORTED
191 else if (chunk_name == png_pCAL)
192 png_handle_pCAL(png_ptr, info_ptr, length);
193 #endif
194
195 #ifdef PNG_READ_sCAL_SUPPORTED
196 else if (chunk_name == png_sCAL)
197 png_handle_sCAL(png_ptr, info_ptr, length);
198 #endif
199
200 #ifdef PNG_READ_pHYs_SUPPORTED
201 else if (chunk_name == png_pHYs)
202 png_handle_pHYs(png_ptr, info_ptr, length);
203 #endif
204
205 #ifdef PNG_READ_sBIT_SUPPORTED
206 else if (chunk_name == png_sBIT)
207 png_handle_sBIT(png_ptr, info_ptr, length);
208 #endif
209
210 #ifdef PNG_READ_sRGB_SUPPORTED
211 else if (chunk_name == png_sRGB)
212 png_handle_sRGB(png_ptr, info_ptr, length);
213 #endif
214
215 #ifdef PNG_READ_iCCP_SUPPORTED
216 else if (chunk_name == png_iCCP)
217 png_handle_iCCP(png_ptr, info_ptr, length);
218 #endif
219
220 #ifdef PNG_READ_sPLT_SUPPORTED
221 else if (chunk_name == png_sPLT)
222 png_handle_sPLT(png_ptr, info_ptr, length);
223 #endif
224
225 #ifdef PNG_READ_tEXt_SUPPORTED
226 else if (chunk_name == png_tEXt)
227 png_handle_tEXt(png_ptr, info_ptr, length);
228 #endif
229
230 #ifdef PNG_READ_tIME_SUPPORTED
231 else if (chunk_name == png_tIME)
232 png_handle_tIME(png_ptr, info_ptr, length);
233 #endif
234
235 #ifdef PNG_READ_tRNS_SUPPORTED
236 else if (chunk_name == png_tRNS)
237 png_handle_tRNS(png_ptr, info_ptr, length);
238 #endif
239
240 #ifdef PNG_READ_zTXt_SUPPORTED
241 else if (chunk_name == png_zTXt)
242 png_handle_zTXt(png_ptr, info_ptr, length);
243 #endif
244
245 #ifdef PNG_READ_iTXt_SUPPORTED
246 else if (chunk_name == png_iTXt)
247 png_handle_iTXt(png_ptr, info_ptr, length);
248 #endif
249
250 else
251 png_handle_unknown(png_ptr, info_ptr, length,
252 PNG_HANDLE_CHUNK_AS_DEFAULT);
253 }
254 }
255 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
256
257 /* Optional call to update the users info_ptr structure */
258 void PNGAPI
png_read_update_info(png_structrp png_ptr,png_inforp info_ptr)259 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
260 {
261 png_debug(1, "in png_read_update_info");
262
263 if (png_ptr != NULL)
264 {
265 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
266 {
267 png_read_start_row(png_ptr);
268
269 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
270 png_read_transform_info(png_ptr, info_ptr);
271 # else
272 PNG_UNUSED(info_ptr)
273 # endif
274 }
275
276 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
277 else
278 png_app_error(png_ptr,
279 "png_read_update_info/png_start_read_image: duplicate call");
280 }
281 }
282
283 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
284 /* Initialize palette, background, etc, after transformations
285 * are set, but before any reading takes place. This allows
286 * the user to obtain a gamma-corrected palette, for example.
287 * If the user doesn't call this, we will do it ourselves.
288 */
289 void PNGAPI
png_start_read_image(png_structrp png_ptr)290 png_start_read_image(png_structrp png_ptr)
291 {
292 png_debug(1, "in png_start_read_image");
293
294 if (png_ptr != NULL)
295 {
296 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
297 png_read_start_row(png_ptr);
298
299 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
300 else
301 png_app_error(png_ptr,
302 "png_start_read_image/png_read_update_info: duplicate call");
303 }
304 }
305 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
306
307 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
308 #ifdef PNG_MNG_FEATURES_SUPPORTED
309 /* Undoes intrapixel differencing,
310 * NOTE: this is apparently only supported in the 'sequential' reader.
311 */
312 static void
png_do_read_intrapixel(png_row_infop row_info,png_bytep row)313 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
314 {
315 png_debug(1, "in png_do_read_intrapixel");
316
317 if (
318 (row_info->color_type & PNG_COLOR_MASK_COLOR))
319 {
320 int bytes_per_pixel;
321 png_uint_32 row_width = row_info->width;
322
323 if (row_info->bit_depth == 8)
324 {
325 png_bytep rp;
326 png_uint_32 i;
327
328 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
329 bytes_per_pixel = 3;
330
331 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
332 bytes_per_pixel = 4;
333
334 else
335 return;
336
337 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
338 {
339 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
340 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
341 }
342 }
343 else if (row_info->bit_depth == 16)
344 {
345 png_bytep rp;
346 png_uint_32 i;
347
348 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
349 bytes_per_pixel = 6;
350
351 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
352 bytes_per_pixel = 8;
353
354 else
355 return;
356
357 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
358 {
359 png_uint_32 s0 = (*(rp ) << 8) | *(rp + 1);
360 png_uint_32 s1 = (*(rp + 2) << 8) | *(rp + 3);
361 png_uint_32 s2 = (*(rp + 4) << 8) | *(rp + 5);
362 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
363 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
364 *(rp ) = (png_byte)((red >> 8) & 0xff);
365 *(rp + 1) = (png_byte)(red & 0xff);
366 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
367 *(rp + 5) = (png_byte)(blue & 0xff);
368 }
369 }
370 }
371 }
372 #endif /* PNG_MNG_FEATURES_SUPPORTED */
373
374 void PNGAPI
png_read_row(png_structrp png_ptr,png_bytep row,png_bytep dsp_row)375 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
376 {
377 png_row_info row_info;
378
379 if (png_ptr == NULL)
380 return;
381
382 png_debug2(1, "in png_read_row (row %lu, pass %d)",
383 (unsigned long)png_ptr->row_number, png_ptr->pass);
384
385 /* png_read_start_row sets the information (in particular iwidth) for this
386 * interlace pass.
387 */
388 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
389 png_read_start_row(png_ptr);
390
391 /* 1.5.6: row_info moved out of png_struct to a local here. */
392 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
393 row_info.color_type = png_ptr->color_type;
394 row_info.bit_depth = png_ptr->bit_depth;
395 row_info.channels = png_ptr->channels;
396 row_info.pixel_depth = png_ptr->pixel_depth;
397 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
398
399 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
400 {
401 /* Check for transforms that have been set but were defined out */
402 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
403 if (png_ptr->transformations & PNG_INVERT_MONO)
404 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
405 #endif
406
407 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
408 if (png_ptr->transformations & PNG_FILLER)
409 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
410 #endif
411
412 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
413 !defined(PNG_READ_PACKSWAP_SUPPORTED)
414 if (png_ptr->transformations & PNG_PACKSWAP)
415 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
416 #endif
417
418 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
419 if (png_ptr->transformations & PNG_PACK)
420 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
421 #endif
422
423 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
424 if (png_ptr->transformations & PNG_SHIFT)
425 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
426 #endif
427
428 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
429 if (png_ptr->transformations & PNG_BGR)
430 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
431 #endif
432
433 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
434 if (png_ptr->transformations & PNG_SWAP_BYTES)
435 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
436 #endif
437 }
438
439 #ifdef PNG_READ_INTERLACING_SUPPORTED
440 /* If interlaced and we do not need a new row, combine row and return.
441 * Notice that the pixels we have from previous rows have been transformed
442 * already; we can only combine like with like (transformed or
443 * untransformed) and, because of the libpng API for interlaced images, this
444 * means we must transform before de-interlacing.
445 */
446 if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
447 {
448 switch (png_ptr->pass)
449 {
450 case 0:
451 if (png_ptr->row_number & 0x07)
452 {
453 if (dsp_row != NULL)
454 png_combine_row(png_ptr, dsp_row, 1/*display*/);
455 png_read_finish_row(png_ptr);
456 return;
457 }
458 break;
459
460 case 1:
461 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
462 {
463 if (dsp_row != NULL)
464 png_combine_row(png_ptr, dsp_row, 1/*display*/);
465
466 png_read_finish_row(png_ptr);
467 return;
468 }
469 break;
470
471 case 2:
472 if ((png_ptr->row_number & 0x07) != 4)
473 {
474 if (dsp_row != NULL && (png_ptr->row_number & 4))
475 png_combine_row(png_ptr, dsp_row, 1/*display*/);
476
477 png_read_finish_row(png_ptr);
478 return;
479 }
480 break;
481
482 case 3:
483 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
484 {
485 if (dsp_row != NULL)
486 png_combine_row(png_ptr, dsp_row, 1/*display*/);
487
488 png_read_finish_row(png_ptr);
489 return;
490 }
491 break;
492
493 case 4:
494 if ((png_ptr->row_number & 3) != 2)
495 {
496 if (dsp_row != NULL && (png_ptr->row_number & 2))
497 png_combine_row(png_ptr, dsp_row, 1/*display*/);
498
499 png_read_finish_row(png_ptr);
500 return;
501 }
502 break;
503
504 case 5:
505 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
506 {
507 if (dsp_row != NULL)
508 png_combine_row(png_ptr, dsp_row, 1/*display*/);
509
510 png_read_finish_row(png_ptr);
511 return;
512 }
513 break;
514
515 default:
516 case 6:
517 if (!(png_ptr->row_number & 1))
518 {
519 png_read_finish_row(png_ptr);
520 return;
521 }
522 break;
523 }
524 }
525 #endif
526
527 if (!(png_ptr->mode & PNG_HAVE_IDAT))
528 png_error(png_ptr, "Invalid attempt to read row data");
529
530 /* Fill the row with IDAT data: */
531 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
532
533 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
534 {
535 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
536 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
537 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
538 else
539 png_error(png_ptr, "bad adaptive filter value");
540 }
541
542 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
543 * 1.5.6, while the buffer really is this big in current versions of libpng
544 * it may not be in the future, so this was changed just to copy the
545 * interlaced count:
546 */
547 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
548
549 #ifdef PNG_MNG_FEATURES_SUPPORTED
550 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
551 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
552 {
553 /* Intrapixel differencing */
554 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
555 }
556 #endif
557
558 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
559 if (png_ptr->transformations)
560 png_do_read_transformations(png_ptr, &row_info);
561 #endif
562
563 /* The transformed pixel depth should match the depth now in row_info. */
564 if (png_ptr->transformed_pixel_depth == 0)
565 {
566 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
567 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
568 png_error(png_ptr, "sequential row overflow");
569 }
570
571 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
572 png_error(png_ptr, "internal sequential row size calculation error");
573
574 #ifdef PNG_READ_INTERLACING_SUPPORTED
575 /* Blow up interlaced rows to full size */
576 if (png_ptr->interlaced &&
577 (png_ptr->transformations & PNG_INTERLACE))
578 {
579 if (png_ptr->pass < 6)
580 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
581 png_ptr->transformations);
582
583 if (dsp_row != NULL)
584 png_combine_row(png_ptr, dsp_row, 1/*display*/);
585
586 if (row != NULL)
587 png_combine_row(png_ptr, row, 0/*row*/);
588 }
589
590 else
591 #endif
592 {
593 if (row != NULL)
594 png_combine_row(png_ptr, row, -1/*ignored*/);
595
596 if (dsp_row != NULL)
597 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
598 }
599 png_read_finish_row(png_ptr);
600
601 if (png_ptr->read_row_fn != NULL)
602 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
603
604 }
605 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
606
607 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
608 /* Read one or more rows of image data. If the image is interlaced,
609 * and png_set_interlace_handling() has been called, the rows need to
610 * contain the contents of the rows from the previous pass. If the
611 * image has alpha or transparency, and png_handle_alpha()[*] has been
612 * called, the rows contents must be initialized to the contents of the
613 * screen.
614 *
615 * "row" holds the actual image, and pixels are placed in it
616 * as they arrive. If the image is displayed after each pass, it will
617 * appear to "sparkle" in. "display_row" can be used to display a
618 * "chunky" progressive image, with finer detail added as it becomes
619 * available. If you do not want this "chunky" display, you may pass
620 * NULL for display_row. If you do not want the sparkle display, and
621 * you have not called png_handle_alpha(), you may pass NULL for rows.
622 * If you have called png_handle_alpha(), and the image has either an
623 * alpha channel or a transparency chunk, you must provide a buffer for
624 * rows. In this case, you do not have to provide a display_row buffer
625 * also, but you may. If the image is not interlaced, or if you have
626 * not called png_set_interlace_handling(), the display_row buffer will
627 * be ignored, so pass NULL to it.
628 *
629 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
630 */
631
632 void PNGAPI
png_read_rows(png_structrp png_ptr,png_bytepp row,png_bytepp display_row,png_uint_32 num_rows)633 png_read_rows(png_structrp png_ptr, png_bytepp row,
634 png_bytepp display_row, png_uint_32 num_rows)
635 {
636 png_uint_32 i;
637 png_bytepp rp;
638 png_bytepp dp;
639
640 png_debug(1, "in png_read_rows");
641
642 if (png_ptr == NULL)
643 return;
644
645 rp = row;
646 dp = display_row;
647 if (rp != NULL && dp != NULL)
648 for (i = 0; i < num_rows; i++)
649 {
650 png_bytep rptr = *rp++;
651 png_bytep dptr = *dp++;
652
653 png_read_row(png_ptr, rptr, dptr);
654 }
655
656 else if (rp != NULL)
657 for (i = 0; i < num_rows; i++)
658 {
659 png_bytep rptr = *rp;
660 png_read_row(png_ptr, rptr, NULL);
661 rp++;
662 }
663
664 else if (dp != NULL)
665 for (i = 0; i < num_rows; i++)
666 {
667 png_bytep dptr = *dp;
668 png_read_row(png_ptr, NULL, dptr);
669 dp++;
670 }
671 }
672 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
673
674 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
675 /* Read the entire image. If the image has an alpha channel or a tRNS
676 * chunk, and you have called png_handle_alpha()[*], you will need to
677 * initialize the image to the current image that PNG will be overlaying.
678 * We set the num_rows again here, in case it was incorrectly set in
679 * png_read_start_row() by a call to png_read_update_info() or
680 * png_start_read_image() if png_set_interlace_handling() wasn't called
681 * prior to either of these functions like it should have been. You can
682 * only call this function once. If you desire to have an image for
683 * each pass of a interlaced image, use png_read_rows() instead.
684 *
685 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
686 */
687 void PNGAPI
png_read_image(png_structrp png_ptr,png_bytepp image)688 png_read_image(png_structrp png_ptr, png_bytepp image)
689 {
690 png_uint_32 i, image_height;
691 int pass, j;
692 png_bytepp rp;
693
694 png_debug(1, "in png_read_image");
695
696 if (png_ptr == NULL)
697 return;
698
699 #ifdef PNG_READ_INTERLACING_SUPPORTED
700 if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
701 {
702 pass = png_set_interlace_handling(png_ptr);
703 /* And make sure transforms are initialized. */
704 png_start_read_image(png_ptr);
705 }
706 else
707 {
708 if (png_ptr->interlaced && !(png_ptr->transformations & PNG_INTERLACE))
709 {
710 /* Caller called png_start_read_image or png_read_update_info without
711 * first turning on the PNG_INTERLACE transform. We can fix this here,
712 * but the caller should do it!
713 */
714 png_warning(png_ptr, "Interlace handling should be turned on when "
715 "using png_read_image");
716 /* Make sure this is set correctly */
717 png_ptr->num_rows = png_ptr->height;
718 }
719
720 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
721 * the above error case.
722 */
723 pass = png_set_interlace_handling(png_ptr);
724 }
725 #else
726 if (png_ptr->interlaced)
727 png_error(png_ptr,
728 "Cannot read interlaced image -- interlace handler disabled");
729
730 pass = 1;
731 #endif
732
733 image_height=png_ptr->height;
734
735 for (j = 0; j < pass; j++)
736 {
737 rp = image;
738 for (i = 0; i < image_height; i++)
739 {
740 png_read_row(png_ptr, *rp, NULL);
741 rp++;
742 }
743 }
744 }
745 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
746
747 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
748 /* Read the end of the PNG file. Will not read past the end of the
749 * file, will verify the end is accurate, and will read any comments
750 * or time information at the end of the file, if info is not NULL.
751 */
752 void PNGAPI
png_read_end(png_structrp png_ptr,png_inforp info_ptr)753 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
754 {
755 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
756 int keep;
757 #endif
758
759 png_debug(1, "in png_read_end");
760
761 if (png_ptr == NULL)
762 return;
763
764 /* If png_read_end is called in the middle of reading the rows there may
765 * still be pending IDAT data and an owned zstream. Deal with this here.
766 */
767 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
768 if (!png_chunk_unknown_handling(png_ptr, png_IDAT))
769 #endif
770 png_read_finish_IDAT(png_ptr);
771
772 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
773 /* Report invalid palette index; added at libng-1.5.10 */
774 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
775 png_ptr->num_palette_max > png_ptr->num_palette)
776 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
777 #endif
778
779 do
780 {
781 png_uint_32 length = png_read_chunk_header(png_ptr);
782 png_uint_32 chunk_name = png_ptr->chunk_name;
783
784 if (chunk_name == png_IHDR)
785 png_handle_IHDR(png_ptr, info_ptr, length);
786
787 else if (chunk_name == png_IEND)
788 png_handle_IEND(png_ptr, info_ptr, length);
789
790 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
791 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
792 {
793 if (chunk_name == png_IDAT)
794 {
795 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
796 png_benign_error(png_ptr, "Too many IDATs found");
797 }
798 png_handle_unknown(png_ptr, info_ptr, length, keep);
799 if (chunk_name == png_PLTE)
800 png_ptr->mode |= PNG_HAVE_PLTE;
801 }
802 #endif
803
804 else if (chunk_name == png_IDAT)
805 {
806 /* Zero length IDATs are legal after the last IDAT has been
807 * read, but not after other chunks have been read.
808 */
809 if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
810 png_benign_error(png_ptr, "Too many IDATs found");
811
812 png_crc_finish(png_ptr, length);
813 }
814 else if (chunk_name == png_PLTE)
815 png_handle_PLTE(png_ptr, info_ptr, length);
816
817 #ifdef PNG_READ_bKGD_SUPPORTED
818 else if (chunk_name == png_bKGD)
819 png_handle_bKGD(png_ptr, info_ptr, length);
820 #endif
821
822 #ifdef PNG_READ_cHRM_SUPPORTED
823 else if (chunk_name == png_cHRM)
824 png_handle_cHRM(png_ptr, info_ptr, length);
825 #endif
826
827 #ifdef PNG_READ_gAMA_SUPPORTED
828 else if (chunk_name == png_gAMA)
829 png_handle_gAMA(png_ptr, info_ptr, length);
830 #endif
831
832 #ifdef PNG_READ_hIST_SUPPORTED
833 else if (chunk_name == png_hIST)
834 png_handle_hIST(png_ptr, info_ptr, length);
835 #endif
836
837 #ifdef PNG_READ_oFFs_SUPPORTED
838 else if (chunk_name == png_oFFs)
839 png_handle_oFFs(png_ptr, info_ptr, length);
840 #endif
841
842 #ifdef PNG_READ_pCAL_SUPPORTED
843 else if (chunk_name == png_pCAL)
844 png_handle_pCAL(png_ptr, info_ptr, length);
845 #endif
846
847 #ifdef PNG_READ_sCAL_SUPPORTED
848 else if (chunk_name == png_sCAL)
849 png_handle_sCAL(png_ptr, info_ptr, length);
850 #endif
851
852 #ifdef PNG_READ_pHYs_SUPPORTED
853 else if (chunk_name == png_pHYs)
854 png_handle_pHYs(png_ptr, info_ptr, length);
855 #endif
856
857 #ifdef PNG_READ_sBIT_SUPPORTED
858 else if (chunk_name == png_sBIT)
859 png_handle_sBIT(png_ptr, info_ptr, length);
860 #endif
861
862 #ifdef PNG_READ_sRGB_SUPPORTED
863 else if (chunk_name == png_sRGB)
864 png_handle_sRGB(png_ptr, info_ptr, length);
865 #endif
866
867 #ifdef PNG_READ_iCCP_SUPPORTED
868 else if (chunk_name == png_iCCP)
869 png_handle_iCCP(png_ptr, info_ptr, length);
870 #endif
871
872 #ifdef PNG_READ_sPLT_SUPPORTED
873 else if (chunk_name == png_sPLT)
874 png_handle_sPLT(png_ptr, info_ptr, length);
875 #endif
876
877 #ifdef PNG_READ_tEXt_SUPPORTED
878 else if (chunk_name == png_tEXt)
879 png_handle_tEXt(png_ptr, info_ptr, length);
880 #endif
881
882 #ifdef PNG_READ_tIME_SUPPORTED
883 else if (chunk_name == png_tIME)
884 png_handle_tIME(png_ptr, info_ptr, length);
885 #endif
886
887 #ifdef PNG_READ_tRNS_SUPPORTED
888 else if (chunk_name == png_tRNS)
889 png_handle_tRNS(png_ptr, info_ptr, length);
890 #endif
891
892 #ifdef PNG_READ_zTXt_SUPPORTED
893 else if (chunk_name == png_zTXt)
894 png_handle_zTXt(png_ptr, info_ptr, length);
895 #endif
896
897 #ifdef PNG_READ_iTXt_SUPPORTED
898 else if (chunk_name == png_iTXt)
899 png_handle_iTXt(png_ptr, info_ptr, length);
900 #endif
901
902 else
903 png_handle_unknown(png_ptr, info_ptr, length,
904 PNG_HANDLE_CHUNK_AS_DEFAULT);
905 } while (!(png_ptr->mode & PNG_HAVE_IEND));
906 }
907 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
908
909 /* Free all memory used in the read struct */
910 static void
png_read_destroy(png_structrp png_ptr)911 png_read_destroy(png_structrp png_ptr)
912 {
913 png_debug(1, "in png_read_destroy");
914
915 #ifdef PNG_READ_GAMMA_SUPPORTED
916 png_destroy_gamma_table(png_ptr);
917 #endif
918
919 png_free(png_ptr, png_ptr->big_row_buf);
920 png_free(png_ptr, png_ptr->big_prev_row);
921 png_free(png_ptr, png_ptr->read_buffer);
922
923 #ifdef PNG_READ_QUANTIZE_SUPPORTED
924 png_free(png_ptr, png_ptr->palette_lookup);
925 png_free(png_ptr, png_ptr->quantize_index);
926 #endif
927
928 if (png_ptr->free_me & PNG_FREE_PLTE)
929 png_zfree(png_ptr, png_ptr->palette);
930 png_ptr->free_me &= ~PNG_FREE_PLTE;
931
932 #if defined(PNG_tRNS_SUPPORTED) || \
933 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
934 if (png_ptr->free_me & PNG_FREE_TRNS)
935 png_free(png_ptr, png_ptr->trans_alpha);
936 png_ptr->free_me &= ~PNG_FREE_TRNS;
937 #endif
938
939 inflateEnd(&png_ptr->zstream);
940
941 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
942 png_free(png_ptr, png_ptr->save_buffer);
943 #endif
944
945 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) &&\
946 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
947 png_free(png_ptr, png_ptr->unknown_chunk.data);
948 #endif
949
950 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
951 png_free(png_ptr, png_ptr->chunk_list);
952 #endif
953
954 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
955 * callbacks are still set at this point. They are required to complete the
956 * destruction of the png_struct itself.
957 */
958 }
959
960 /* Free all memory used by the read */
961 void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr,png_infopp info_ptr_ptr,png_infopp end_info_ptr_ptr)962 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
963 png_infopp end_info_ptr_ptr)
964 {
965 png_structrp png_ptr = NULL;
966
967 png_debug(1, "in png_destroy_read_struct");
968
969 if (png_ptr_ptr != NULL)
970 png_ptr = *png_ptr_ptr;
971
972 if (png_ptr == NULL)
973 return;
974
975 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
976 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
977 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
978 */
979 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
980 png_destroy_info_struct(png_ptr, info_ptr_ptr);
981
982 *png_ptr_ptr = NULL;
983 png_read_destroy(png_ptr);
984 png_destroy_png_struct(png_ptr);
985 }
986
987 void PNGAPI
png_set_read_status_fn(png_structrp png_ptr,png_read_status_ptr read_row_fn)988 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
989 {
990 if (png_ptr == NULL)
991 return;
992
993 png_ptr->read_row_fn = read_row_fn;
994 }
995
996
997 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
998 #ifdef PNG_INFO_IMAGE_SUPPORTED
999 void PNGAPI
png_read_png(png_structrp png_ptr,png_inforp info_ptr,int transforms,voidp params)1000 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1001 int transforms,
1002 voidp params)
1003 {
1004 int row;
1005
1006 if (png_ptr == NULL || info_ptr == NULL)
1007 return;
1008
1009 /* png_read_info() gives us all of the information from the
1010 * PNG file before the first IDAT (image data chunk).
1011 */
1012 png_read_info(png_ptr, info_ptr);
1013 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1014 png_error(png_ptr, "Image is too high to process with png_read_png()");
1015
1016 /* -------------- image transformations start here ------------------- */
1017
1018 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1019 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1020 */
1021 if (transforms & PNG_TRANSFORM_SCALE_16)
1022 {
1023 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1024 * did in earlier versions, while "scale_16" is now more accurate.
1025 */
1026 png_set_scale_16(png_ptr);
1027 }
1028 #endif
1029
1030 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1031 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1032 * latter by doing SCALE first. This is ok and allows apps not to check for
1033 * which is supported to get the right answer.
1034 */
1035 if (transforms & PNG_TRANSFORM_STRIP_16)
1036 png_set_strip_16(png_ptr);
1037 #endif
1038
1039 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1040 /* Strip alpha bytes from the input data without combining with
1041 * the background (not recommended).
1042 */
1043 if (transforms & PNG_TRANSFORM_STRIP_ALPHA)
1044 png_set_strip_alpha(png_ptr);
1045 #endif
1046
1047 #if defined(PNG_READ_PACK_SUPPORTED) && !defined(PNG_READ_EXPAND_SUPPORTED)
1048 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1049 * byte into separate bytes (useful for paletted and grayscale images).
1050 */
1051 if (transforms & PNG_TRANSFORM_PACKING)
1052 png_set_packing(png_ptr);
1053 #endif
1054
1055 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1056 /* Change the order of packed pixels to least significant bit first
1057 * (not useful if you are using png_set_packing).
1058 */
1059 if (transforms & PNG_TRANSFORM_PACKSWAP)
1060 png_set_packswap(png_ptr);
1061 #endif
1062
1063 #ifdef PNG_READ_EXPAND_SUPPORTED
1064 /* Expand paletted colors into true RGB triplets
1065 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1066 * Expand paletted or RGB images with transparency to full alpha
1067 * channels so the data will be available as RGBA quartets.
1068 */
1069 if (transforms & PNG_TRANSFORM_EXPAND)
1070 if ((png_ptr->bit_depth < 8) ||
1071 (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ||
1072 (info_ptr->valid & PNG_INFO_tRNS))
1073 png_set_expand(png_ptr);
1074 #endif
1075
1076 /* We don't handle background color or gamma transformation or quantizing.
1077 */
1078
1079 #ifdef PNG_READ_INVERT_SUPPORTED
1080 /* Invert monochrome files to have 0 as white and 1 as black
1081 */
1082 if (transforms & PNG_TRANSFORM_INVERT_MONO)
1083 png_set_invert_mono(png_ptr);
1084 #endif
1085
1086 #ifdef PNG_READ_SHIFT_SUPPORTED
1087 /* If you want to shift the pixel values from the range [0,255] or
1088 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1089 * colors were originally in:
1090 */
1091 if ((transforms & PNG_TRANSFORM_SHIFT) && (info_ptr->valid & PNG_INFO_sBIT))
1092 png_set_shift(png_ptr, &info_ptr->sig_bit);
1093 #endif
1094
1095 #ifdef PNG_READ_BGR_SUPPORTED
1096 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1097 if (transforms & PNG_TRANSFORM_BGR)
1098 png_set_bgr(png_ptr);
1099 #endif
1100
1101 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1102 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1103 if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
1104 png_set_swap_alpha(png_ptr);
1105 #endif
1106
1107 #ifdef PNG_READ_SWAP_SUPPORTED
1108 /* Swap bytes of 16-bit files to least significant byte first */
1109 if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
1110 png_set_swap(png_ptr);
1111 #endif
1112
1113 /* Added at libpng-1.2.41 */
1114 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1115 /* Invert the alpha channel from opacity to transparency */
1116 if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
1117 png_set_invert_alpha(png_ptr);
1118 #endif
1119
1120 /* Added at libpng-1.2.41 */
1121 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1122 /* Expand grayscale image to RGB */
1123 if (transforms & PNG_TRANSFORM_GRAY_TO_RGB)
1124 png_set_gray_to_rgb(png_ptr);
1125 #endif
1126
1127 /* Added at libpng-1.5.4 */
1128 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1129 if (transforms & PNG_TRANSFORM_EXPAND_16)
1130 png_set_expand_16(png_ptr);
1131 #endif
1132
1133 /* We don't handle adding filler bytes */
1134
1135 /* We use png_read_image and rely on that for interlace handling, but we also
1136 * call png_read_update_info therefore must turn on interlace handling now:
1137 */
1138 (void)png_set_interlace_handling(png_ptr);
1139
1140 /* Optional call to gamma correct and add the background to the palette
1141 * and update info structure. REQUIRED if you are expecting libpng to
1142 * update the palette for you (i.e., you selected such a transform above).
1143 */
1144 png_read_update_info(png_ptr, info_ptr);
1145
1146 /* -------------- image transformations end here ------------------- */
1147
1148 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1149 if (info_ptr->row_pointers == NULL)
1150 {
1151 png_uint_32 iptr;
1152
1153 info_ptr->row_pointers = (png_bytepp)png_malloc(png_ptr,
1154 info_ptr->height * (sizeof (png_bytep)));
1155 for (iptr=0; iptr<info_ptr->height; iptr++)
1156 info_ptr->row_pointers[iptr] = NULL;
1157
1158 info_ptr->free_me |= PNG_FREE_ROWS;
1159
1160 for (row = 0; row < (int)info_ptr->height; row++)
1161 info_ptr->row_pointers[row] = (png_bytep)png_malloc(png_ptr,
1162 png_get_rowbytes(png_ptr, info_ptr));
1163 }
1164
1165 png_read_image(png_ptr, info_ptr->row_pointers);
1166 info_ptr->valid |= PNG_INFO_IDAT;
1167
1168 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1169 png_read_end(png_ptr, info_ptr);
1170
1171 PNG_UNUSED(transforms) /* Quiet compiler warnings */
1172 PNG_UNUSED(params)
1173
1174 }
1175 #endif /* PNG_INFO_IMAGE_SUPPORTED */
1176 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
1177
1178 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1179 /* SIMPLIFIED READ
1180 *
1181 * This code currently relies on the sequential reader, though it could easily
1182 * be made to work with the progressive one.
1183 */
1184 /* Arguments to png_image_finish_read: */
1185
1186 /* Encoding of PNG data (used by the color-map code) */
1187 # define P_NOTSET 0 /* File encoding not yet known */
1188 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1189 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1190 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1191 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1192
1193 /* Color-map processing: after libpng has run on the PNG image further
1194 * processing may be needed to conver the data to color-map indicies.
1195 */
1196 #define PNG_CMAP_NONE 0
1197 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1198 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1199 #define PNG_CMAP_RGB 3 /* Process RGB data */
1200 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1201
1202 /* The following document where the background is for each processing case. */
1203 #define PNG_CMAP_NONE_BACKGROUND 256
1204 #define PNG_CMAP_GA_BACKGROUND 231
1205 #define PNG_CMAP_TRANS_BACKGROUND 254
1206 #define PNG_CMAP_RGB_BACKGROUND 256
1207 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1208
1209 typedef struct
1210 {
1211 /* Arguments: */
1212 png_imagep image;
1213 png_voidp buffer;
1214 png_int_32 row_stride;
1215 png_voidp colormap;
1216 png_const_colorp background;
1217 /* Local variables: */
1218 png_voidp local_row;
1219 png_voidp first_row;
1220 ptrdiff_t row_bytes; /* step between rows */
1221 int file_encoding; /* E_ values above */
1222 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1223 int colormap_processing; /* PNG_CMAP_ values above */
1224 } png_image_read_control;
1225
1226 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1227 * called, so setting up the jmp_buf is not required. This means that anything
1228 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1229 * instead so that control is returned safely back to this routine.
1230 */
1231 static int
png_image_read_init(png_imagep image)1232 png_image_read_init(png_imagep image)
1233 {
1234 if (image->opaque == NULL)
1235 {
1236 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1237 png_safe_error, png_safe_warning);
1238
1239 /* And set the rest of the structure to NULL to ensure that the various
1240 * fields are consistent.
1241 */
1242 memset(image, 0, (sizeof *image));
1243 image->version = PNG_IMAGE_VERSION;
1244
1245 if (png_ptr != NULL)
1246 {
1247 png_infop info_ptr = png_create_info_struct(png_ptr);
1248
1249 if (info_ptr != NULL)
1250 {
1251 png_controlp control = png_voidcast(png_controlp,
1252 png_malloc_warn(png_ptr, (sizeof *control)));
1253
1254 if (control != NULL)
1255 {
1256 memset(control, 0, (sizeof *control));
1257
1258 control->png_ptr = png_ptr;
1259 control->info_ptr = info_ptr;
1260 control->for_write = 0;
1261
1262 image->opaque = control;
1263 return 1;
1264 }
1265
1266 /* Error clean up */
1267 png_destroy_info_struct(png_ptr, &info_ptr);
1268 }
1269
1270 png_destroy_read_struct(&png_ptr, NULL, NULL);
1271 }
1272
1273 return png_image_error(image, "png_image_read: out of memory");
1274 }
1275
1276 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1277 }
1278
1279 /* Utility to find the base format of a PNG file from a png_struct. */
1280 static png_uint_32
png_image_format(png_structrp png_ptr)1281 png_image_format(png_structrp png_ptr)
1282 {
1283 png_uint_32 format = 0;
1284
1285 if (png_ptr->color_type & PNG_COLOR_MASK_COLOR)
1286 format |= PNG_FORMAT_FLAG_COLOR;
1287
1288 if (png_ptr->color_type & PNG_COLOR_MASK_ALPHA)
1289 format |= PNG_FORMAT_FLAG_ALPHA;
1290
1291 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1292 * sets the png_struct fields; that's all we are interested in here. The
1293 * precise interaction with an app call to png_set_tRNS and PNG file reading
1294 * is unclear.
1295 */
1296 else if (png_ptr->num_trans > 0)
1297 format |= PNG_FORMAT_FLAG_ALPHA;
1298
1299 if (png_ptr->bit_depth == 16)
1300 format |= PNG_FORMAT_FLAG_LINEAR;
1301
1302 if (png_ptr->color_type & PNG_COLOR_MASK_PALETTE)
1303 format |= PNG_FORMAT_FLAG_COLORMAP;
1304
1305 return format;
1306 }
1307
1308 /* Is the given gamma significantly different from sRGB? The test is the same
1309 * one used in pngrtran.c when deciding whether to do gamma correction. The
1310 * arithmetic optimizes the division by using the fact that the inverse of the
1311 * file sRGB gamma is 2.2
1312 */
1313 static int
png_gamma_not_sRGB(png_fixed_point g)1314 png_gamma_not_sRGB(png_fixed_point g)
1315 {
1316 if (g < PNG_FP_1)
1317 {
1318 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1319 if (g == 0)
1320 return 0;
1321
1322 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1323 }
1324
1325 return 1;
1326 }
1327
1328 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1329 * header and fill in all the information. This is executed in a safe context,
1330 * unlike the init routine above.
1331 */
1332 static int
png_image_read_header(png_voidp argument)1333 png_image_read_header(png_voidp argument)
1334 {
1335 png_imagep image = png_voidcast(png_imagep, argument);
1336 png_structrp png_ptr = image->opaque->png_ptr;
1337 png_inforp info_ptr = image->opaque->info_ptr;
1338
1339 png_set_benign_errors(png_ptr, 1/*warn*/);
1340 png_read_info(png_ptr, info_ptr);
1341
1342 /* Do this the fast way; just read directly out of png_struct. */
1343 image->width = png_ptr->width;
1344 image->height = png_ptr->height;
1345
1346 {
1347 png_uint_32 format = png_image_format(png_ptr);
1348
1349 image->format = format;
1350
1351 #ifdef PNG_COLORSPACE_SUPPORTED
1352 /* Does the colorspace match sRGB? If there is no color endpoint
1353 * (colorant) information assume yes, otherwise require the
1354 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1355 * colorspace has been determined to be invalid ignore it.
1356 */
1357 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1358 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1359 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1360 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1361 #endif
1362 }
1363
1364 /* We need the maximum number of entries regardless of the format the
1365 * application sets here.
1366 */
1367 {
1368 png_uint_32 cmap_entries;
1369
1370 switch (png_ptr->color_type)
1371 {
1372 case PNG_COLOR_TYPE_GRAY:
1373 cmap_entries = 1U << png_ptr->bit_depth;
1374 break;
1375
1376 case PNG_COLOR_TYPE_PALETTE:
1377 cmap_entries = png_ptr->num_palette;
1378 break;
1379
1380 default:
1381 cmap_entries = 256;
1382 break;
1383 }
1384
1385 if (cmap_entries > 256)
1386 cmap_entries = 256;
1387
1388 image->colormap_entries = cmap_entries;
1389 }
1390
1391 return 1;
1392 }
1393
1394 #ifdef PNG_STDIO_SUPPORTED
1395 int PNGAPI
png_image_begin_read_from_stdio(png_imagep image,FILE * file)1396 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1397 {
1398 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1399 {
1400 if (file != NULL)
1401 {
1402 if (png_image_read_init(image))
1403 {
1404 /* This is slightly evil, but png_init_io doesn't do anything other
1405 * than this and we haven't changed the standard IO functions so
1406 * this saves a 'safe' function.
1407 */
1408 image->opaque->png_ptr->io_ptr = file;
1409 return png_safe_execute(image, png_image_read_header, image);
1410 }
1411 }
1412
1413 else
1414 return png_image_error(image,
1415 "png_image_begin_read_from_stdio: invalid argument");
1416 }
1417
1418 else if (image != NULL)
1419 return png_image_error(image,
1420 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1421
1422 return 0;
1423 }
1424
1425 int PNGAPI
png_image_begin_read_from_file(png_imagep image,const char * file_name)1426 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1427 {
1428 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1429 {
1430 if (file_name != NULL)
1431 {
1432 FILE *fp = fopen(file_name, "rb");
1433
1434 if (fp != NULL)
1435 {
1436 if (png_image_read_init(image))
1437 {
1438 image->opaque->png_ptr->io_ptr = fp;
1439 image->opaque->owned_file = 1;
1440 return png_safe_execute(image, png_image_read_header, image);
1441 }
1442
1443 /* Clean up: just the opened file. */
1444 (void)fclose(fp);
1445 }
1446
1447 else
1448 return png_image_error(image, strerror(errno));
1449 }
1450
1451 else
1452 return png_image_error(image,
1453 "png_image_begin_read_from_file: invalid argument");
1454 }
1455
1456 else if (image != NULL)
1457 return png_image_error(image,
1458 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1459
1460 return 0;
1461 }
1462 #endif /* PNG_STDIO_SUPPORTED */
1463
1464 static void PNGCBAPI
png_image_memory_read(png_structp png_ptr,png_bytep out,png_size_t need)1465 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1466 {
1467 if (png_ptr != NULL)
1468 {
1469 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1470 if (image != NULL)
1471 {
1472 png_controlp cp = image->opaque;
1473 if (cp != NULL)
1474 {
1475 png_const_bytep memory = cp->memory;
1476 png_size_t size = cp->size;
1477
1478 if (memory != NULL && size >= need)
1479 {
1480 memcpy(out, memory, need);
1481 cp->memory = memory + need;
1482 cp->size = size - need;
1483 return;
1484 }
1485
1486 png_error(png_ptr, "read beyond end of data");
1487 }
1488 }
1489
1490 png_error(png_ptr, "invalid memory read");
1491 }
1492 }
1493
png_image_begin_read_from_memory(png_imagep image,png_const_voidp memory,png_size_t size)1494 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1495 png_const_voidp memory, png_size_t size)
1496 {
1497 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1498 {
1499 if (memory != NULL && size > 0)
1500 {
1501 if (png_image_read_init(image))
1502 {
1503 /* Now set the IO functions to read from the memory buffer and
1504 * store it into io_ptr. Again do this in-place to avoid calling a
1505 * libpng function that requires error handling.
1506 */
1507 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1508 image->opaque->size = size;
1509 image->opaque->png_ptr->io_ptr = image;
1510 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1511
1512 return png_safe_execute(image, png_image_read_header, image);
1513 }
1514 }
1515
1516 else
1517 return png_image_error(image,
1518 "png_image_begin_read_from_memory: invalid argument");
1519 }
1520
1521 else if (image != NULL)
1522 return png_image_error(image,
1523 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1524
1525 return 0;
1526 }
1527
1528 /* Utility function to skip chunks that are not used by the simplified image
1529 * read functions and an appropriate macro to call it.
1530 */
1531 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1532 static void
png_image_skip_unused_chunks(png_structrp png_ptr)1533 png_image_skip_unused_chunks(png_structrp png_ptr)
1534 {
1535 /* Prepare the reader to ignore all recognized chunks whose data will not
1536 * be used, i.e., all chunks recognized by libpng except for those
1537 * involved in basic image reading:
1538 *
1539 * IHDR, PLTE, IDAT, IEND
1540 *
1541 * Or image data handling:
1542 *
1543 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1544 *
1545 * This provides a small performance improvement and eliminates any
1546 * potential vulnerability to security problems in the unused chunks.
1547 *
1548 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1549 * too. This allows the simplified API to be compiled without iCCP support,
1550 * however if the support is there the chunk is still checked to detect
1551 * errors (which are unfortunately quite common.)
1552 */
1553 {
1554 static PNG_CONST png_byte chunks_to_process[] = {
1555 98, 75, 71, 68, '\0', /* bKGD */
1556 99, 72, 82, 77, '\0', /* cHRM */
1557 103, 65, 77, 65, '\0', /* gAMA */
1558 # ifdef PNG_READ_iCCP_SUPPORTED
1559 105, 67, 67, 80, '\0', /* iCCP */
1560 # endif
1561 115, 66, 73, 84, '\0', /* sBIT */
1562 115, 82, 71, 66, '\0', /* sRGB */
1563 };
1564
1565 /* Ignore unknown chunks and all other chunks except for the
1566 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1567 */
1568 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1569 NULL, -1);
1570
1571 /* But do not ignore image data handling chunks */
1572 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1573 chunks_to_process, (sizeof chunks_to_process)/5);
1574 }
1575 }
1576
1577 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1578 #else
1579 # define PNG_SKIP_CHUNKS(p) ((void)0)
1580 #endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */
1581
1582 /* The following macro gives the exact rounded answer for all values in the
1583 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1584 * the correct numbers 0..5
1585 */
1586 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1587
1588 /* Utility functions to make particular color-maps */
1589 static void
set_file_encoding(png_image_read_control * display)1590 set_file_encoding(png_image_read_control *display)
1591 {
1592 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1593 if (png_gamma_significant(g))
1594 {
1595 if (png_gamma_not_sRGB(g))
1596 {
1597 display->file_encoding = P_FILE;
1598 display->gamma_to_linear = png_reciprocal(g);
1599 }
1600
1601 else
1602 display->file_encoding = P_sRGB;
1603 }
1604
1605 else
1606 display->file_encoding = P_LINEAR8;
1607 }
1608
1609 static unsigned int
decode_gamma(png_image_read_control * display,png_uint_32 value,int encoding)1610 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1611 {
1612 if (encoding == P_FILE) /* double check */
1613 encoding = display->file_encoding;
1614
1615 if (encoding == P_NOTSET) /* must be the file encoding */
1616 {
1617 set_file_encoding(display);
1618 encoding = display->file_encoding;
1619 }
1620
1621 switch (encoding)
1622 {
1623 case P_FILE:
1624 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1625 break;
1626
1627 case P_sRGB:
1628 value = png_sRGB_table[value];
1629 break;
1630
1631 case P_LINEAR:
1632 break;
1633
1634 case P_LINEAR8:
1635 value *= 257;
1636 break;
1637
1638 default:
1639 png_error(display->image->opaque->png_ptr,
1640 "unexpected encoding (internal error)");
1641 break;
1642 }
1643
1644 return value;
1645 }
1646
1647 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)1648 png_colormap_compose(png_image_read_control *display,
1649 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1650 png_uint_32 background, int encoding)
1651 {
1652 /* The file value is composed on the background, the background has the given
1653 * encoding and so does the result, the file is encoded with P_FILE and the
1654 * file and alpha are 8-bit values. The (output) encoding will always be
1655 * P_LINEAR or P_sRGB.
1656 */
1657 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1658 png_uint_32 b = decode_gamma(display, background, encoding);
1659
1660 /* The alpha is always an 8-bit value (it comes from the palette), the value
1661 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1662 */
1663 f = f * alpha + b * (255-alpha);
1664
1665 if (encoding == P_LINEAR)
1666 {
1667 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1668 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1669 */
1670 f *= 257; /* Now scaled by 65535 */
1671 f += f >> 16;
1672 f = (f+32768) >> 16;
1673 }
1674
1675 else /* P_sRGB */
1676 f = PNG_sRGB_FROM_LINEAR(f);
1677
1678 return f;
1679 }
1680
1681 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1682 * be 8-bit.
1683 */
1684 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)1685 png_create_colormap_entry(png_image_read_control *display,
1686 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1687 png_uint_32 alpha, int encoding)
1688 {
1689 png_imagep image = display->image;
1690 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) ?
1691 P_LINEAR : P_sRGB;
1692 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1693 (red != green || green != blue);
1694
1695 if (ip > 255)
1696 png_error(image->opaque->png_ptr, "color-map index out of range");
1697
1698 /* Update the cache with whether the file gamma is significantly different
1699 * from sRGB.
1700 */
1701 if (encoding == P_FILE)
1702 {
1703 if (display->file_encoding == P_NOTSET)
1704 set_file_encoding(display);
1705
1706 /* Note that the cached value may be P_FILE too, but if it is then the
1707 * gamma_to_linear member has been set.
1708 */
1709 encoding = display->file_encoding;
1710 }
1711
1712 if (encoding == P_FILE)
1713 {
1714 png_fixed_point g = display->gamma_to_linear;
1715
1716 red = png_gamma_16bit_correct(red*257, g);
1717 green = png_gamma_16bit_correct(green*257, g);
1718 blue = png_gamma_16bit_correct(blue*257, g);
1719
1720 if (convert_to_Y || output_encoding == P_LINEAR)
1721 {
1722 alpha *= 257;
1723 encoding = P_LINEAR;
1724 }
1725
1726 else
1727 {
1728 red = PNG_sRGB_FROM_LINEAR(red * 255);
1729 green = PNG_sRGB_FROM_LINEAR(green * 255);
1730 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1731 encoding = P_sRGB;
1732 }
1733 }
1734
1735 else if (encoding == P_LINEAR8)
1736 {
1737 /* This encoding occurs quite frequently in test cases because PngSuite
1738 * includes a gAMA 1.0 chunk with most images.
1739 */
1740 red *= 257;
1741 green *= 257;
1742 blue *= 257;
1743 alpha *= 257;
1744 encoding = P_LINEAR;
1745 }
1746
1747 else if (encoding == P_sRGB && (convert_to_Y || output_encoding == P_LINEAR))
1748 {
1749 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1750 * linear.
1751 */
1752 red = png_sRGB_table[red];
1753 green = png_sRGB_table[green];
1754 blue = png_sRGB_table[blue];
1755 alpha *= 257;
1756 encoding = P_LINEAR;
1757 }
1758
1759 /* This is set if the color isn't gray but the output is. */
1760 if (encoding == P_LINEAR)
1761 {
1762 if (convert_to_Y)
1763 {
1764 /* NOTE: these values are copied from png_do_rgb_to_gray */
1765 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1766 (png_uint_32)2366 * blue;
1767
1768 if (output_encoding == P_LINEAR)
1769 y = (y + 16384) >> 15;
1770
1771 else
1772 {
1773 /* y is scaled by 32768, we need it scaled by 255: */
1774 y = (y + 128) >> 8;
1775 y *= 255;
1776 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1777 encoding = P_sRGB;
1778 }
1779
1780 blue = red = green = y;
1781 }
1782
1783 else if (output_encoding == P_sRGB)
1784 {
1785 red = PNG_sRGB_FROM_LINEAR(red * 255);
1786 green = PNG_sRGB_FROM_LINEAR(green * 255);
1787 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1788 alpha = PNG_DIV257(alpha);
1789 encoding = P_sRGB;
1790 }
1791 }
1792
1793 if (encoding != output_encoding)
1794 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1795
1796 /* Store the value. */
1797 {
1798 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1799 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1800 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1801 # else
1802 # define afirst 0
1803 # endif
1804 # ifdef PNG_FORMAT_BGR_SUPPORTED
1805 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) ? 2 : 0;
1806 # else
1807 # define bgr 0
1808 # endif
1809
1810 if (output_encoding == P_LINEAR)
1811 {
1812 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1813
1814 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1815
1816 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1817 * value, if less than 65535 (this is, effectively, composite on black
1818 * if the alpha channel is removed.)
1819 */
1820 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1821 {
1822 case 4:
1823 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1824 /* FALL THROUGH */
1825
1826 case 3:
1827 if (alpha < 65535)
1828 {
1829 if (alpha > 0)
1830 {
1831 blue = (blue * alpha + 32767U)/65535U;
1832 green = (green * alpha + 32767U)/65535U;
1833 red = (red * alpha + 32767U)/65535U;
1834 }
1835
1836 else
1837 red = green = blue = 0;
1838 }
1839 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1840 entry[afirst + 1] = (png_uint_16)green;
1841 entry[afirst + bgr] = (png_uint_16)red;
1842 break;
1843
1844 case 2:
1845 entry[1 ^ afirst] = (png_uint_16)alpha;
1846 /* FALL THROUGH */
1847
1848 case 1:
1849 if (alpha < 65535)
1850 {
1851 if (alpha > 0)
1852 green = (green * alpha + 32767U)/65535U;
1853
1854 else
1855 green = 0;
1856 }
1857 entry[afirst] = (png_uint_16)green;
1858 break;
1859
1860 default:
1861 break;
1862 }
1863 }
1864
1865 else /* output encoding is P_sRGB */
1866 {
1867 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1868
1869 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1870
1871 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1872 {
1873 case 4:
1874 entry[afirst ? 0 : 3] = (png_byte)alpha;
1875 case 3:
1876 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1877 entry[afirst + 1] = (png_byte)green;
1878 entry[afirst + bgr] = (png_byte)red;
1879 break;
1880
1881 case 2:
1882 entry[1 ^ afirst] = (png_byte)alpha;
1883 case 1:
1884 entry[afirst] = (png_byte)green;
1885 break;
1886
1887 default:
1888 break;
1889 }
1890 }
1891
1892 # ifdef afirst
1893 # undef afirst
1894 # endif
1895 # ifdef bgr
1896 # undef bgr
1897 # endif
1898 }
1899 }
1900
1901 static int
make_gray_file_colormap(png_image_read_control * display)1902 make_gray_file_colormap(png_image_read_control *display)
1903 {
1904 unsigned int i;
1905
1906 for (i=0; i<256; ++i)
1907 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1908
1909 return i;
1910 }
1911
1912 static int
make_gray_colormap(png_image_read_control * display)1913 make_gray_colormap(png_image_read_control *display)
1914 {
1915 unsigned int i;
1916
1917 for (i=0; i<256; ++i)
1918 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
1919
1920 return i;
1921 }
1922 #define PNG_GRAY_COLORMAP_ENTRIES 256
1923
1924 static int
make_ga_colormap(png_image_read_control * display)1925 make_ga_colormap(png_image_read_control *display)
1926 {
1927 unsigned int i, a;
1928
1929 /* Alpha is retained, the output will be a color-map with entries
1930 * selected by six levels of alpha. One transparent entry, 6 gray
1931 * levels for all the intermediate alpha values, leaving 230 entries
1932 * for the opaque grays. The color-map entries are the six values
1933 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
1934 * relevant entry.
1935 *
1936 * if (alpha > 229) // opaque
1937 * {
1938 * // The 231 entries are selected to make the math below work:
1939 * base = 0;
1940 * entry = (231 * gray + 128) >> 8;
1941 * }
1942 * else if (alpha < 26) // transparent
1943 * {
1944 * base = 231;
1945 * entry = 0;
1946 * }
1947 * else // partially opaque
1948 * {
1949 * base = 226 + 6 * PNG_DIV51(alpha);
1950 * entry = PNG_DIV51(gray);
1951 * }
1952 */
1953 i = 0;
1954 while (i < 231)
1955 {
1956 unsigned int gray = (i * 256 + 115) / 231;
1957 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
1958 }
1959
1960 /* 255 is used here for the component values for consistency with the code
1961 * that undoes premultiplication in pngwrite.c.
1962 */
1963 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
1964
1965 for (a=1; a<5; ++a)
1966 {
1967 unsigned int g;
1968
1969 for (g=0; g<6; ++g)
1970 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
1971 P_sRGB);
1972 }
1973
1974 return i;
1975 }
1976
1977 #define PNG_GA_COLORMAP_ENTRIES 256
1978
1979 static int
make_rgb_colormap(png_image_read_control * display)1980 make_rgb_colormap(png_image_read_control *display)
1981 {
1982 unsigned int i, r;
1983
1984 /* Build a 6x6x6 opaque RGB cube */
1985 for (i=r=0; r<6; ++r)
1986 {
1987 unsigned int g;
1988
1989 for (g=0; g<6; ++g)
1990 {
1991 unsigned int b;
1992
1993 for (b=0; b<6; ++b)
1994 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
1995 P_sRGB);
1996 }
1997 }
1998
1999 return i;
2000 }
2001
2002 #define PNG_RGB_COLORMAP_ENTRIES 216
2003
2004 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2005 #define PNG_RGB_INDEX(r,g,b) \
2006 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2007
2008 static int
png_image_read_colormap(png_voidp argument)2009 png_image_read_colormap(png_voidp argument)
2010 {
2011 png_image_read_control *display =
2012 png_voidcast(png_image_read_control*, argument);
2013 const png_imagep image = display->image;
2014
2015 const png_structrp png_ptr = image->opaque->png_ptr;
2016 const png_uint_32 output_format = image->format;
2017 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) ?
2018 P_LINEAR : P_sRGB;
2019
2020 unsigned int cmap_entries;
2021 unsigned int output_processing; /* Output processing option */
2022 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2023
2024 /* Background information; the background color and the index of this color
2025 * in the color-map if it exists (else 256).
2026 */
2027 unsigned int background_index = 256;
2028 png_uint_32 back_r, back_g, back_b;
2029
2030 /* Flags to accumulate things that need to be done to the input. */
2031 int expand_tRNS = 0;
2032
2033 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2034 * very difficult to do, the results look awful, and it is difficult to see
2035 * what possible use it is because the application can't control the
2036 * color-map.
2037 */
2038 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2039 png_ptr->num_trans > 0) /* alpha in input */ &&
2040 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2041 {
2042 if (output_encoding == P_LINEAR) /* compose on black */
2043 back_b = back_g = back_r = 0;
2044
2045 else if (display->background == NULL /* no way to remove it */)
2046 png_error(png_ptr,
2047 "a background color must be supplied to remove alpha/transparency");
2048
2049 /* Get a copy of the background color (this avoids repeating the checks
2050 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2051 * output format.
2052 */
2053 else
2054 {
2055 back_g = display->background->green;
2056 if (output_format & PNG_FORMAT_FLAG_COLOR)
2057 {
2058 back_r = display->background->red;
2059 back_b = display->background->blue;
2060 }
2061 else
2062 back_b = back_r = back_g;
2063 }
2064 }
2065
2066 else if (output_encoding == P_LINEAR)
2067 back_b = back_r = back_g = 65535;
2068
2069 else
2070 back_b = back_r = back_g = 255;
2071
2072 /* Default the input file gamma if required - this is necessary because
2073 * libpng assumes that if no gamma information is present the data is in the
2074 * output format, but the simplified API deduces the gamma from the input
2075 * format.
2076 */
2077 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2078 {
2079 /* Do this directly, not using the png_colorspace functions, to ensure
2080 * that it happens even if the colorspace is invalid (though probably if
2081 * it is the setting will be ignored) Note that the same thing can be
2082 * achieved at the application interface with png_set_gAMA.
2083 */
2084 if (png_ptr->bit_depth == 16 &&
2085 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2086 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2087
2088 else
2089 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2090
2091 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2092 }
2093
2094 /* Decide what to do based on the PNG color type of the input data. The
2095 * utility function png_create_colormap_entry deals with most aspects of the
2096 * output transformations; this code works out how to produce bytes of
2097 * color-map entries from the original format.
2098 */
2099 switch (png_ptr->color_type)
2100 {
2101 case PNG_COLOR_TYPE_GRAY:
2102 if (png_ptr->bit_depth <= 8)
2103 {
2104 /* There at most 256 colors in the output, regardless of
2105 * transparency.
2106 */
2107 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2108
2109 cmap_entries = 1U << png_ptr->bit_depth;
2110 if (cmap_entries > image->colormap_entries)
2111 png_error(png_ptr, "gray[8] color-map: too few entries");
2112
2113 step = 255 / (cmap_entries - 1);
2114 output_processing = PNG_CMAP_NONE;
2115
2116 /* If there is a tRNS chunk then this either selects a transparent
2117 * value or, if the output has no alpha, the background color.
2118 */
2119 if (png_ptr->num_trans > 0)
2120 {
2121 trans = png_ptr->trans_color.gray;
2122
2123 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2124 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2125 }
2126
2127 /* png_create_colormap_entry just takes an RGBA and writes the
2128 * corresponding color-map entry using the format from 'image',
2129 * including the required conversion to sRGB or linear as
2130 * appropriate. The input values are always either sRGB (if the
2131 * gamma correction flag is 0) or 0..255 scaled file encoded values
2132 * (if the function must gamma correct them).
2133 */
2134 for (i=val=0; i<cmap_entries; ++i, val += step)
2135 {
2136 /* 'i' is a file value. While this will result in duplicated
2137 * entries for 8-bit non-sRGB encoded files it is necessary to
2138 * have non-gamma corrected values to do tRNS handling.
2139 */
2140 if (i != trans)
2141 png_create_colormap_entry(display, i, val, val, val, 255,
2142 P_FILE/*8-bit with file gamma*/);
2143
2144 /* Else this entry is transparent. The colors don't matter if
2145 * there is an alpha channel (back_alpha == 0), but it does no
2146 * harm to pass them in; the values are not set above so this
2147 * passes in white.
2148 *
2149 * NOTE: this preserves the full precision of the application
2150 * supplied background color when it is used.
2151 */
2152 else
2153 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2154 back_alpha, output_encoding);
2155 }
2156
2157 /* We need libpng to preserve the original encoding. */
2158 data_encoding = P_FILE;
2159
2160 /* The rows from libpng, while technically gray values, are now also
2161 * color-map indicies; however, they may need to be expanded to 1
2162 * byte per pixel. This is what png_set_packing does (i.e., it
2163 * unpacks the bit values into bytes.)
2164 */
2165 if (png_ptr->bit_depth < 8)
2166 png_set_packing(png_ptr);
2167 }
2168
2169 else /* bit depth is 16 */
2170 {
2171 /* The 16-bit input values can be converted directly to 8-bit gamma
2172 * encoded values; however, if a tRNS chunk is present 257 color-map
2173 * entries are required. This means that the extra entry requires
2174 * special processing; add an alpha channel, sacrifice gray level
2175 * 254 and convert transparent (alpha==0) entries to that.
2176 *
2177 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2178 * same time to minimize quality loss. If a tRNS chunk is present
2179 * this means libpng must handle it too; otherwise it is impossible
2180 * to do the exact match on the 16-bit value.
2181 *
2182 * If the output has no alpha channel *and* the background color is
2183 * gray then it is possible to let libpng handle the substitution by
2184 * ensuring that the corresponding gray level matches the background
2185 * color exactly.
2186 */
2187 data_encoding = P_sRGB;
2188
2189 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2190 png_error(png_ptr, "gray[16] color-map: too few entries");
2191
2192 cmap_entries = make_gray_colormap(display);
2193
2194 if (png_ptr->num_trans > 0)
2195 {
2196 unsigned int back_alpha;
2197
2198 if (output_format & PNG_FORMAT_FLAG_ALPHA)
2199 back_alpha = 0;
2200
2201 else
2202 {
2203 if (back_r == back_g && back_g == back_b)
2204 {
2205 /* Background is gray; no special processing will be
2206 * required.
2207 */
2208 png_color_16 c;
2209 png_uint_32 gray = back_g;
2210
2211 if (output_encoding == P_LINEAR)
2212 {
2213 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2214
2215 /* And make sure the corresponding palette entry
2216 * matches.
2217 */
2218 png_create_colormap_entry(display, gray, back_g, back_g,
2219 back_g, 65535, P_LINEAR);
2220 }
2221
2222 /* The background passed to libpng, however, must be the
2223 * sRGB value.
2224 */
2225 c.index = 0; /*unused*/
2226 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2227
2228 /* NOTE: does this work without expanding tRNS to alpha?
2229 * It should be the color->gray case below apparently
2230 * doesn't.
2231 */
2232 png_set_background_fixed(png_ptr, &c,
2233 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2234 0/*gamma: not used*/);
2235
2236 output_processing = PNG_CMAP_NONE;
2237 break;
2238 }
2239
2240 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2241 }
2242
2243 /* output_processing means that the libpng-processed row will be
2244 * 8-bit GA and it has to be processing to single byte color-map
2245 * values. Entry 254 is replaced by either a completely
2246 * transparent entry or by the background color at full
2247 * precision (and the background color is not a simple gray leve
2248 * in this case.)
2249 */
2250 expand_tRNS = 1;
2251 output_processing = PNG_CMAP_TRANS;
2252 background_index = 254;
2253
2254 /* And set (overwrite) color-map entry 254 to the actual
2255 * background color at full precision.
2256 */
2257 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2258 back_alpha, output_encoding);
2259 }
2260
2261 else
2262 output_processing = PNG_CMAP_NONE;
2263 }
2264 break;
2265
2266 case PNG_COLOR_TYPE_GRAY_ALPHA:
2267 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2268 * of 65536 combinations. If, however, the alpha channel is to be
2269 * removed there are only 256 possibilities if the background is gray.
2270 * (Otherwise there is a subset of the 65536 possibilities defined by
2271 * the triangle between black, white and the background color.)
2272 *
2273 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2274 * worry about tRNS matching - tRNS is ignored if there is an alpha
2275 * channel.
2276 */
2277 data_encoding = P_sRGB;
2278
2279 if (output_format & PNG_FORMAT_FLAG_ALPHA)
2280 {
2281 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2282 png_error(png_ptr, "gray+alpha color-map: too few entries");
2283
2284 cmap_entries = make_ga_colormap(display);
2285
2286 background_index = PNG_CMAP_GA_BACKGROUND;
2287 output_processing = PNG_CMAP_GA;
2288 }
2289
2290 else /* alpha is removed */
2291 {
2292 /* Alpha must be removed as the PNG data is processed when the
2293 * background is a color because the G and A channels are
2294 * independent and the vector addition (non-parallel vectors) is a
2295 * 2-D problem.
2296 *
2297 * This can be reduced to the same algorithm as above by making a
2298 * colormap containing gray levels (for the opaque grays), a
2299 * background entry (for a transparent pixel) and a set of four six
2300 * level color values, one set for each intermediate alpha value.
2301 * See the comments in make_ga_colormap for how this works in the
2302 * per-pixel processing.
2303 *
2304 * If the background is gray, however, we only need a 256 entry gray
2305 * level color map. It is sufficient to make the entry generated
2306 * for the background color be exactly the color specified.
2307 */
2308 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2309 (back_r == back_g && back_g == back_b))
2310 {
2311 /* Background is gray; no special processing will be required. */
2312 png_color_16 c;
2313 png_uint_32 gray = back_g;
2314
2315 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2316 png_error(png_ptr, "gray-alpha color-map: too few entries");
2317
2318 cmap_entries = make_gray_colormap(display);
2319
2320 if (output_encoding == P_LINEAR)
2321 {
2322 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2323
2324 /* And make sure the corresponding palette entry matches. */
2325 png_create_colormap_entry(display, gray, back_g, back_g,
2326 back_g, 65535, P_LINEAR);
2327 }
2328
2329 /* The background passed to libpng, however, must be the sRGB
2330 * value.
2331 */
2332 c.index = 0; /*unused*/
2333 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2334
2335 png_set_background_fixed(png_ptr, &c,
2336 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2337 0/*gamma: not used*/);
2338
2339 output_processing = PNG_CMAP_NONE;
2340 }
2341
2342 else
2343 {
2344 png_uint_32 i, a;
2345
2346 /* This is the same as png_make_ga_colormap, above, except that
2347 * the entries are all opaque.
2348 */
2349 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2350 png_error(png_ptr, "ga-alpha color-map: too few entries");
2351
2352 i = 0;
2353 while (i < 231)
2354 {
2355 png_uint_32 gray = (i * 256 + 115) / 231;
2356 png_create_colormap_entry(display, i++, gray, gray, gray,
2357 255, P_sRGB);
2358 }
2359
2360 /* NOTE: this preserves the full precision of the application
2361 * background color.
2362 */
2363 background_index = i;
2364 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2365 output_encoding == P_LINEAR ? 65535U : 255U, output_encoding);
2366
2367 /* For non-opaque input composite on the sRGB background - this
2368 * requires inverting the encoding for each component. The input
2369 * is still converted to the sRGB encoding because this is a
2370 * reasonable approximate to the logarithmic curve of human
2371 * visual sensitivity, at least over the narrow range which PNG
2372 * represents. Consequently 'G' is always sRGB encoded, while
2373 * 'A' is linear. We need the linear background colors.
2374 */
2375 if (output_encoding == P_sRGB) /* else already linear */
2376 {
2377 /* This may produce a value not exactly matching the
2378 * background, but that's ok because these numbers are only
2379 * used when alpha != 0
2380 */
2381 back_r = png_sRGB_table[back_r];
2382 back_g = png_sRGB_table[back_g];
2383 back_b = png_sRGB_table[back_b];
2384 }
2385
2386 for (a=1; a<5; ++a)
2387 {
2388 unsigned int g;
2389
2390 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2391 * by an 8-bit alpha value (0..255).
2392 */
2393 png_uint_32 alpha = 51 * a;
2394 png_uint_32 back_rx = (255-alpha) * back_r;
2395 png_uint_32 back_gx = (255-alpha) * back_g;
2396 png_uint_32 back_bx = (255-alpha) * back_b;
2397
2398 for (g=0; g<6; ++g)
2399 {
2400 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2401
2402 png_create_colormap_entry(display, i++,
2403 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2404 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2405 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2406 }
2407 }
2408
2409 cmap_entries = i;
2410 output_processing = PNG_CMAP_GA;
2411 }
2412 }
2413 break;
2414
2415 case PNG_COLOR_TYPE_RGB:
2416 case PNG_COLOR_TYPE_RGB_ALPHA:
2417 /* Exclude the case where the output is gray; we can always handle this
2418 * with the cases above.
2419 */
2420 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2421 {
2422 /* The color-map will be grayscale, so we may as well convert the
2423 * input RGB values to a simple grayscale and use the grayscale
2424 * code above.
2425 *
2426 * NOTE: calling this apparently damages the recognition of the
2427 * transparent color in background color handling; call
2428 * png_set_tRNS_to_alpha before png_set_background_fixed.
2429 */
2430 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2431 -1);
2432 data_encoding = P_sRGB;
2433
2434 /* The output will now be one or two 8-bit gray or gray+alpha
2435 * channels. The more complex case arises when the input has alpha.
2436 */
2437 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2438 png_ptr->num_trans > 0) &&
2439 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2440 {
2441 /* Both input and output have an alpha channel, so no background
2442 * processing is required; just map the GA bytes to the right
2443 * color-map entry.
2444 */
2445 expand_tRNS = 1;
2446
2447 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2448 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2449
2450 cmap_entries = make_ga_colormap(display);
2451 background_index = PNG_CMAP_GA_BACKGROUND;
2452 output_processing = PNG_CMAP_GA;
2453 }
2454
2455 else
2456 {
2457 /* Either the input or the output has no alpha channel, so there
2458 * will be no non-opaque pixels in the color-map; it will just be
2459 * grayscale.
2460 */
2461 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2462 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2463
2464 /* Ideally this code would use libpng to do the gamma correction,
2465 * but if an input alpha channel is to be removed we will hit the
2466 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2467 * correction bug). Fix this by dropping the gamma correction in
2468 * this case and doing it in the palette; this will result in
2469 * duplicate palette entries, but that's better than the
2470 * alternative of double gamma correction.
2471 */
2472 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2473 png_ptr->num_trans > 0) &&
2474 png_gamma_not_sRGB(png_ptr->colorspace.gamma))
2475 {
2476 cmap_entries = make_gray_file_colormap(display);
2477 data_encoding = P_FILE;
2478 }
2479
2480 else
2481 cmap_entries = make_gray_colormap(display);
2482
2483 /* But if the input has alpha or transparency it must be removed
2484 */
2485 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2486 png_ptr->num_trans > 0)
2487 {
2488 png_color_16 c;
2489 png_uint_32 gray = back_g;
2490
2491 /* We need to ensure that the application background exists in
2492 * the colormap and that completely transparent pixels map to
2493 * it. Achieve this simply by ensuring that the entry
2494 * selected for the background really is the background color.
2495 */
2496 if (data_encoding == P_FILE) /* from the fixup above */
2497 {
2498 /* The app supplied a gray which is in output_encoding, we
2499 * need to convert it to a value of the input (P_FILE)
2500 * encoding then set this palette entry to the required
2501 * output encoding.
2502 */
2503 if (output_encoding == P_sRGB)
2504 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2505
2506 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2507 png_ptr->colorspace.gamma)); /* now P_FILE */
2508
2509 /* And make sure the corresponding palette entry contains
2510 * exactly the required sRGB value.
2511 */
2512 png_create_colormap_entry(display, gray, back_g, back_g,
2513 back_g, 0/*unused*/, output_encoding);
2514 }
2515
2516 else if (output_encoding == P_LINEAR)
2517 {
2518 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2519
2520 /* And make sure the corresponding palette entry matches.
2521 */
2522 png_create_colormap_entry(display, gray, back_g, back_g,
2523 back_g, 0/*unused*/, P_LINEAR);
2524 }
2525
2526 /* The background passed to libpng, however, must be the
2527 * output (normally sRGB) value.
2528 */
2529 c.index = 0; /*unused*/
2530 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2531
2532 /* NOTE: the following is apparently a bug in libpng. Without
2533 * it the transparent color recognition in
2534 * png_set_background_fixed seems to go wrong.
2535 */
2536 expand_tRNS = 1;
2537 png_set_background_fixed(png_ptr, &c,
2538 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2539 0/*gamma: not used*/);
2540 }
2541
2542 output_processing = PNG_CMAP_NONE;
2543 }
2544 }
2545
2546 else /* output is color */
2547 {
2548 /* We could use png_quantize here so long as there is no transparent
2549 * color or alpha; png_quantize ignores alpha. Easier overall just
2550 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2551 * Consequently we always want libpng to produce sRGB data.
2552 */
2553 data_encoding = P_sRGB;
2554
2555 /* Is there any transparency or alpha? */
2556 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2557 png_ptr->num_trans > 0)
2558 {
2559 /* Is there alpha in the output too? If so all four channels are
2560 * processed into a special RGB cube with alpha support.
2561 */
2562 if (output_format & PNG_FORMAT_FLAG_ALPHA)
2563 {
2564 png_uint_32 r;
2565
2566 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2567 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2568
2569 cmap_entries = make_rgb_colormap(display);
2570
2571 /* Add a transparent entry. */
2572 png_create_colormap_entry(display, cmap_entries, 255, 255,
2573 255, 0, P_sRGB);
2574
2575 /* This is stored as the background index for the processing
2576 * algorithm.
2577 */
2578 background_index = cmap_entries++;
2579
2580 /* Add 27 r,g,b entries each with alpha 0.5. */
2581 for (r=0; r<256; r = (r << 1) | 0x7f)
2582 {
2583 png_uint_32 g;
2584
2585 for (g=0; g<256; g = (g << 1) | 0x7f)
2586 {
2587 png_uint_32 b;
2588
2589 /* This generates components with the values 0, 127 and
2590 * 255
2591 */
2592 for (b=0; b<256; b = (b << 1) | 0x7f)
2593 png_create_colormap_entry(display, cmap_entries++,
2594 r, g, b, 128, P_sRGB);
2595 }
2596 }
2597
2598 expand_tRNS = 1;
2599 output_processing = PNG_CMAP_RGB_ALPHA;
2600 }
2601
2602 else
2603 {
2604 /* Alpha/transparency must be removed. The background must
2605 * exist in the color map (achieved by setting adding it after
2606 * the 666 color-map). If the standard processing code will
2607 * pick up this entry automatically that's all that is
2608 * required; libpng can be called to do the background
2609 * processing.
2610 */
2611 unsigned int sample_size =
2612 PNG_IMAGE_SAMPLE_SIZE(output_format);
2613 png_uint_32 r, g, b; /* sRGB background */
2614
2615 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2616 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2617
2618 cmap_entries = make_rgb_colormap(display);
2619
2620 png_create_colormap_entry(display, cmap_entries, back_r,
2621 back_g, back_b, 0/*unused*/, output_encoding);
2622
2623 if (output_encoding == P_LINEAR)
2624 {
2625 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2626 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2627 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2628 }
2629
2630 else
2631 {
2632 r = back_r;
2633 g = back_g;
2634 b = back_g;
2635 }
2636
2637 /* Compare the newly-created color-map entry with the one the
2638 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2639 * match, add the new one and set this as the background
2640 * index.
2641 */
2642 if (memcmp((png_const_bytep)display->colormap +
2643 sample_size * cmap_entries,
2644 (png_const_bytep)display->colormap +
2645 sample_size * PNG_RGB_INDEX(r,g,b),
2646 sample_size) != 0)
2647 {
2648 /* The background color must be added. */
2649 background_index = cmap_entries++;
2650
2651 /* Add 27 r,g,b entries each with created by composing with
2652 * the background at alpha 0.5.
2653 */
2654 for (r=0; r<256; r = (r << 1) | 0x7f)
2655 {
2656 for (g=0; g<256; g = (g << 1) | 0x7f)
2657 {
2658 /* This generates components with the values 0, 127
2659 * and 255
2660 */
2661 for (b=0; b<256; b = (b << 1) | 0x7f)
2662 png_create_colormap_entry(display, cmap_entries++,
2663 png_colormap_compose(display, r, P_sRGB, 128,
2664 back_r, output_encoding),
2665 png_colormap_compose(display, g, P_sRGB, 128,
2666 back_g, output_encoding),
2667 png_colormap_compose(display, b, P_sRGB, 128,
2668 back_b, output_encoding),
2669 0/*unused*/, output_encoding);
2670 }
2671 }
2672
2673 expand_tRNS = 1;
2674 output_processing = PNG_CMAP_RGB_ALPHA;
2675 }
2676
2677 else /* background color is in the standard color-map */
2678 {
2679 png_color_16 c;
2680
2681 c.index = 0; /*unused*/
2682 c.red = (png_uint_16)back_r;
2683 c.gray = c.green = (png_uint_16)back_g;
2684 c.blue = (png_uint_16)back_b;
2685
2686 png_set_background_fixed(png_ptr, &c,
2687 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2688 0/*gamma: not used*/);
2689
2690 output_processing = PNG_CMAP_RGB;
2691 }
2692 }
2693 }
2694
2695 else /* no alpha or transparency in the input */
2696 {
2697 /* Alpha in the output is irrelevant, simply map the opaque input
2698 * pixels to the 6x6x6 color-map.
2699 */
2700 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2701 png_error(png_ptr, "rgb color-map: too few entries");
2702
2703 cmap_entries = make_rgb_colormap(display);
2704 output_processing = PNG_CMAP_RGB;
2705 }
2706 }
2707 break;
2708
2709 case PNG_COLOR_TYPE_PALETTE:
2710 /* It's already got a color-map. It may be necessary to eliminate the
2711 * tRNS entries though.
2712 */
2713 {
2714 unsigned int num_trans = png_ptr->num_trans;
2715 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2716 png_const_colorp colormap = png_ptr->palette;
2717 const int do_background = trans != NULL &&
2718 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2719 unsigned int i;
2720
2721 /* Just in case: */
2722 if (trans == NULL)
2723 num_trans = 0;
2724
2725 output_processing = PNG_CMAP_NONE;
2726 data_encoding = P_FILE; /* Don't change from color-map indicies */
2727 cmap_entries = png_ptr->num_palette;
2728 if (cmap_entries > 256)
2729 cmap_entries = 256;
2730
2731 if (cmap_entries > image->colormap_entries)
2732 png_error(png_ptr, "palette color-map: too few entries");
2733
2734 for (i=0; i < cmap_entries; ++i)
2735 {
2736 if (do_background && i < num_trans && trans[i] < 255)
2737 {
2738 if (trans[i] == 0)
2739 png_create_colormap_entry(display, i, back_r, back_g,
2740 back_b, 0, output_encoding);
2741
2742 else
2743 {
2744 /* Must compose the PNG file color in the color-map entry
2745 * on the sRGB color in 'back'.
2746 */
2747 png_create_colormap_entry(display, i,
2748 png_colormap_compose(display, colormap[i].red, P_FILE,
2749 trans[i], back_r, output_encoding),
2750 png_colormap_compose(display, colormap[i].green, P_FILE,
2751 trans[i], back_g, output_encoding),
2752 png_colormap_compose(display, colormap[i].blue, P_FILE,
2753 trans[i], back_b, output_encoding),
2754 output_encoding == P_LINEAR ? trans[i] * 257U :
2755 trans[i],
2756 output_encoding);
2757 }
2758 }
2759
2760 else
2761 png_create_colormap_entry(display, i, colormap[i].red,
2762 colormap[i].green, colormap[i].blue,
2763 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2764 }
2765
2766 /* The PNG data may have indicies packed in fewer than 8 bits, it
2767 * must be expanded if so.
2768 */
2769 if (png_ptr->bit_depth < 8)
2770 png_set_packing(png_ptr);
2771 }
2772 break;
2773
2774 default:
2775 png_error(png_ptr, "invalid PNG color type");
2776 /*NOT REACHED*/
2777 break;
2778 }
2779
2780 /* Now deal with the output processing */
2781 if (expand_tRNS && png_ptr->num_trans > 0 &&
2782 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2783 png_set_tRNS_to_alpha(png_ptr);
2784
2785 switch (data_encoding)
2786 {
2787 default:
2788 png_error(png_ptr, "bad data option (internal error)");
2789 break;
2790
2791 case P_sRGB:
2792 /* Change to 8-bit sRGB */
2793 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2794 /* FALL THROUGH */
2795
2796 case P_FILE:
2797 if (png_ptr->bit_depth > 8)
2798 png_set_scale_16(png_ptr);
2799 break;
2800 }
2801
2802 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2803 png_error(png_ptr, "color map overflow (BAD internal error)");
2804
2805 image->colormap_entries = cmap_entries;
2806
2807 /* Double check using the recorded background index */
2808 switch (output_processing)
2809 {
2810 case PNG_CMAP_NONE:
2811 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2812 goto bad_background;
2813 break;
2814
2815 case PNG_CMAP_GA:
2816 if (background_index != PNG_CMAP_GA_BACKGROUND)
2817 goto bad_background;
2818 break;
2819
2820 case PNG_CMAP_TRANS:
2821 if (background_index >= cmap_entries ||
2822 background_index != PNG_CMAP_TRANS_BACKGROUND)
2823 goto bad_background;
2824 break;
2825
2826 case PNG_CMAP_RGB:
2827 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2828 goto bad_background;
2829 break;
2830
2831 case PNG_CMAP_RGB_ALPHA:
2832 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2833 goto bad_background;
2834 break;
2835
2836 default:
2837 png_error(png_ptr, "bad processing option (internal error)");
2838
2839 bad_background:
2840 png_error(png_ptr, "bad background index (internal error)");
2841 }
2842
2843 display->colormap_processing = output_processing;
2844
2845 return 1/*ok*/;
2846 }
2847
2848 /* The final part of the color-map read called from png_image_finish_read. */
2849 static int
png_image_read_and_map(png_voidp argument)2850 png_image_read_and_map(png_voidp argument)
2851 {
2852 png_image_read_control *display = png_voidcast(png_image_read_control*,
2853 argument);
2854 png_imagep image = display->image;
2855 png_structrp png_ptr = image->opaque->png_ptr;
2856 int passes;
2857
2858 /* Called when the libpng data must be transformed into the color-mapped
2859 * form. There is a local row buffer in display->local and this routine must
2860 * do the interlace handling.
2861 */
2862 switch (png_ptr->interlaced)
2863 {
2864 case PNG_INTERLACE_NONE:
2865 passes = 1;
2866 break;
2867
2868 case PNG_INTERLACE_ADAM7:
2869 passes = PNG_INTERLACE_ADAM7_PASSES;
2870 break;
2871
2872 default:
2873 png_error(png_ptr, "unknown interlace type");
2874 }
2875
2876 {
2877 png_uint_32 height = image->height;
2878 png_uint_32 width = image->width;
2879 int proc = display->colormap_processing;
2880 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2881 ptrdiff_t step_row = display->row_bytes;
2882 int pass;
2883
2884 for (pass = 0; pass < passes; ++pass)
2885 {
2886 unsigned int startx, stepx, stepy;
2887 png_uint_32 y;
2888
2889 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2890 {
2891 /* The row may be empty for a short image: */
2892 if (PNG_PASS_COLS(width, pass) == 0)
2893 continue;
2894
2895 startx = PNG_PASS_START_COL(pass);
2896 stepx = PNG_PASS_COL_OFFSET(pass);
2897 y = PNG_PASS_START_ROW(pass);
2898 stepy = PNG_PASS_ROW_OFFSET(pass);
2899 }
2900
2901 else
2902 {
2903 y = 0;
2904 startx = 0;
2905 stepx = stepy = 1;
2906 }
2907
2908 for (; y<height; y += stepy)
2909 {
2910 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
2911 png_bytep outrow = first_row + y * step_row;
2912 png_const_bytep end_row = outrow + width;
2913
2914 /* Read read the libpng data into the temporary buffer. */
2915 png_read_row(png_ptr, inrow, NULL);
2916
2917 /* Now process the row according to the processing option, note
2918 * that the caller verifies that the format of the libpng output
2919 * data is as required.
2920 */
2921 outrow += startx;
2922 switch (proc)
2923 {
2924 case PNG_CMAP_GA:
2925 for (; outrow < end_row; outrow += stepx)
2926 {
2927 /* The data is always in the PNG order */
2928 unsigned int gray = *inrow++;
2929 unsigned int alpha = *inrow++;
2930 unsigned int entry;
2931
2932 /* NOTE: this code is copied as a comment in
2933 * make_ga_colormap above. Please update the
2934 * comment if you change this code!
2935 */
2936 if (alpha > 229) /* opaque */
2937 {
2938 entry = (231 * gray + 128) >> 8;
2939 }
2940 else if (alpha < 26) /* transparent */
2941 {
2942 entry = 231;
2943 }
2944 else /* partially opaque */
2945 {
2946 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
2947 }
2948
2949 *outrow = (png_byte)entry;
2950 }
2951 break;
2952
2953 case PNG_CMAP_TRANS:
2954 for (; outrow < end_row; outrow += stepx)
2955 {
2956 png_byte gray = *inrow++;
2957 png_byte alpha = *inrow++;
2958
2959 if (alpha == 0)
2960 *outrow = PNG_CMAP_TRANS_BACKGROUND;
2961
2962 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
2963 *outrow = gray;
2964
2965 else
2966 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
2967 }
2968 break;
2969
2970 case PNG_CMAP_RGB:
2971 for (; outrow < end_row; outrow += stepx)
2972 {
2973 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
2974 inrow += 3;
2975 }
2976 break;
2977
2978 case PNG_CMAP_RGB_ALPHA:
2979 for (; outrow < end_row; outrow += stepx)
2980 {
2981 unsigned int alpha = inrow[3];
2982
2983 /* Because the alpha entries only hold alpha==0.5 values
2984 * split the processing at alpha==0.25 (64) and 0.75
2985 * (196).
2986 */
2987
2988 if (alpha >= 196)
2989 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
2990 inrow[2]);
2991
2992 else if (alpha < 64)
2993 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
2994
2995 else
2996 {
2997 /* Likewise there are three entries for each of r, g
2998 * and b. We could select the entry by popcount on
2999 * the top two bits on those architectures that
3000 * support it, this is what the code below does,
3001 * crudely.
3002 */
3003 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3004
3005 /* Here are how the values map:
3006 *
3007 * 0x00 .. 0x3f -> 0
3008 * 0x40 .. 0xbf -> 1
3009 * 0xc0 .. 0xff -> 2
3010 *
3011 * So, as above with the explicit alpha checks, the
3012 * breakpoints are at 64 and 196.
3013 */
3014 if (inrow[0] & 0x80) back_i += 9; /* red */
3015 if (inrow[0] & 0x40) back_i += 9;
3016 if (inrow[0] & 0x80) back_i += 3; /* green */
3017 if (inrow[0] & 0x40) back_i += 3;
3018 if (inrow[0] & 0x80) back_i += 1; /* blue */
3019 if (inrow[0] & 0x40) back_i += 1;
3020
3021 *outrow = (png_byte)back_i;
3022 }
3023
3024 inrow += 4;
3025 }
3026 break;
3027
3028 default:
3029 break;
3030 }
3031 }
3032 }
3033 }
3034
3035 return 1;
3036 }
3037
3038 static int
png_image_read_colormapped(png_voidp argument)3039 png_image_read_colormapped(png_voidp argument)
3040 {
3041 png_image_read_control *display = png_voidcast(png_image_read_control*,
3042 argument);
3043 png_imagep image = display->image;
3044 png_controlp control = image->opaque;
3045 png_structrp png_ptr = control->png_ptr;
3046 png_inforp info_ptr = control->info_ptr;
3047
3048 int passes = 0; /* As a flag */
3049
3050 PNG_SKIP_CHUNKS(png_ptr);
3051
3052 /* Update the 'info' structure and make sure the result is as required; first
3053 * make sure to turn on the interlace handling if it will be required
3054 * (because it can't be turned on *after* the call to png_read_update_info!)
3055 */
3056 if (display->colormap_processing == PNG_CMAP_NONE)
3057 passes = png_set_interlace_handling(png_ptr);
3058
3059 png_read_update_info(png_ptr, info_ptr);
3060
3061 /* The expected output can be deduced from the colormap_processing option. */
3062 switch (display->colormap_processing)
3063 {
3064 case PNG_CMAP_NONE:
3065 /* Output must be one channel and one byte per pixel, the output
3066 * encoding can be anything.
3067 */
3068 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3069 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3070 info_ptr->bit_depth == 8)
3071 break;
3072
3073 goto bad_output;
3074
3075 case PNG_CMAP_TRANS:
3076 case PNG_CMAP_GA:
3077 /* Output must be two channels and the 'G' one must be sRGB, the latter
3078 * can be checked with an exact number because it should have been set
3079 * to this number above!
3080 */
3081 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3082 info_ptr->bit_depth == 8 &&
3083 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3084 image->colormap_entries == 256)
3085 break;
3086
3087 goto bad_output;
3088
3089 case PNG_CMAP_RGB:
3090 /* Output must be 8-bit sRGB encoded RGB */
3091 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3092 info_ptr->bit_depth == 8 &&
3093 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3094 image->colormap_entries == 216)
3095 break;
3096
3097 goto bad_output;
3098
3099 case PNG_CMAP_RGB_ALPHA:
3100 /* Output must be 8-bit sRGB encoded RGBA */
3101 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3102 info_ptr->bit_depth == 8 &&
3103 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3104 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3105 break;
3106
3107 /* goto bad_output; */
3108 /* FALL THROUGH */
3109
3110 default:
3111 bad_output:
3112 png_error(png_ptr, "bad color-map processing (internal error)");
3113 }
3114
3115 /* Now read the rows. Do this here if it is possible to read directly into
3116 * the output buffer, otherwise allocate a local row buffer of the maximum
3117 * size libpng requires and call the relevant processing routine safely.
3118 */
3119 {
3120 png_voidp first_row = display->buffer;
3121 ptrdiff_t row_bytes = display->row_stride;
3122
3123 /* The following expression is designed to work correctly whether it gives
3124 * a signed or an unsigned result.
3125 */
3126 if (row_bytes < 0)
3127 {
3128 char *ptr = png_voidcast(char*, first_row);
3129 ptr += (image->height-1) * (-row_bytes);
3130 first_row = png_voidcast(png_voidp, ptr);
3131 }
3132
3133 display->first_row = first_row;
3134 display->row_bytes = row_bytes;
3135 }
3136
3137 if (passes == 0)
3138 {
3139 int result;
3140 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3141
3142 display->local_row = row;
3143 result = png_safe_execute(image, png_image_read_and_map, display);
3144 display->local_row = NULL;
3145 png_free(png_ptr, row);
3146
3147 return result;
3148 }
3149
3150 else
3151 {
3152 png_alloc_size_t row_bytes = display->row_bytes;
3153
3154 while (--passes >= 0)
3155 {
3156 png_uint_32 y = image->height;
3157 png_bytep row = png_voidcast(png_bytep, display->first_row);
3158
3159 while (y-- > 0)
3160 {
3161 png_read_row(png_ptr, row, NULL);
3162 row += row_bytes;
3163 }
3164 }
3165
3166 return 1;
3167 }
3168 }
3169
3170 /* Just the row reading part of png_image_read. */
3171 static int
png_image_read_composite(png_voidp argument)3172 png_image_read_composite(png_voidp argument)
3173 {
3174 png_image_read_control *display = png_voidcast(png_image_read_control*,
3175 argument);
3176 png_imagep image = display->image;
3177 png_structrp png_ptr = image->opaque->png_ptr;
3178 int passes;
3179
3180 switch (png_ptr->interlaced)
3181 {
3182 case PNG_INTERLACE_NONE:
3183 passes = 1;
3184 break;
3185
3186 case PNG_INTERLACE_ADAM7:
3187 passes = PNG_INTERLACE_ADAM7_PASSES;
3188 break;
3189
3190 default:
3191 png_error(png_ptr, "unknown interlace type");
3192 }
3193
3194 {
3195 png_uint_32 height = image->height;
3196 png_uint_32 width = image->width;
3197 ptrdiff_t step_row = display->row_bytes;
3198 unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
3199 int pass;
3200
3201 for (pass = 0; pass < passes; ++pass)
3202 {
3203 unsigned int startx, stepx, stepy;
3204 png_uint_32 y;
3205
3206 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3207 {
3208 /* The row may be empty for a short image: */
3209 if (PNG_PASS_COLS(width, pass) == 0)
3210 continue;
3211
3212 startx = PNG_PASS_START_COL(pass) * channels;
3213 stepx = PNG_PASS_COL_OFFSET(pass) * channels;
3214 y = PNG_PASS_START_ROW(pass);
3215 stepy = PNG_PASS_ROW_OFFSET(pass);
3216 }
3217
3218 else
3219 {
3220 y = 0;
3221 startx = 0;
3222 stepx = channels;
3223 stepy = 1;
3224 }
3225
3226 for (; y<height; y += stepy)
3227 {
3228 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
3229 png_bytep outrow;
3230 png_const_bytep end_row;
3231
3232 /* Read the row, which is packed: */
3233 png_read_row(png_ptr, inrow, NULL);
3234
3235 outrow = png_voidcast(png_bytep, display->first_row);
3236 outrow += y * step_row;
3237 end_row = outrow + width * channels;
3238
3239 /* Now do the composition on each pixel in this row. */
3240 outrow += startx;
3241 for (; outrow < end_row; outrow += stepx)
3242 {
3243 png_byte alpha = inrow[channels];
3244
3245 if (alpha > 0) /* else no change to the output */
3246 {
3247 unsigned int c;
3248
3249 for (c=0; c<channels; ++c)
3250 {
3251 png_uint_32 component = inrow[c];
3252
3253 if (alpha < 255) /* else just use component */
3254 {
3255 /* This is PNG_OPTIMIZED_ALPHA, the component value
3256 * is a linear 8-bit value. Combine this with the
3257 * current outrow[c] value which is sRGB encoded.
3258 * Arithmetic here is 16-bits to preserve the output
3259 * values correctly.
3260 */
3261 component *= 257*255; /* =65535 */
3262 component += (255-alpha)*png_sRGB_table[outrow[c]];
3263
3264 /* So 'component' is scaled by 255*65535 and is
3265 * therefore appropriate for the sRGB to linear
3266 * conversion table.
3267 */
3268 component = PNG_sRGB_FROM_LINEAR(component);
3269 }
3270
3271 outrow[c] = (png_byte)component;
3272 }
3273 }
3274
3275 inrow += channels+1; /* components and alpha channel */
3276 }
3277 }
3278 }
3279 }
3280
3281 return 1;
3282 }
3283
3284 /* The do_local_background case; called when all the following transforms are to
3285 * be done:
3286 *
3287 * PNG_RGB_TO_GRAY
3288 * PNG_COMPOSITE
3289 * PNG_GAMMA
3290 *
3291 * This is a work-round for the fact that both the PNG_RGB_TO_GRAY and
3292 * PNG_COMPOSITE code performs gamma correction, so we get double gamma
3293 * correction. The fix-up is to prevent the PNG_COMPOSITE operation happening
3294 * inside libpng, so this routine sees an 8 or 16-bit gray+alpha row and handles
3295 * the removal or pre-multiplication of the alpha channel.
3296 */
3297 static int
png_image_read_background(png_voidp argument)3298 png_image_read_background(png_voidp argument)
3299 {
3300 png_image_read_control *display = png_voidcast(png_image_read_control*,
3301 argument);
3302 png_imagep image = display->image;
3303 png_structrp png_ptr = image->opaque->png_ptr;
3304 png_inforp info_ptr = image->opaque->info_ptr;
3305 png_uint_32 height = image->height;
3306 png_uint_32 width = image->width;
3307 int pass, passes;
3308
3309 /* Double check the convoluted logic below. We expect to get here with
3310 * libpng doing rgb to gray and gamma correction but background processing
3311 * left to the png_image_read_background function. The rows libpng produce
3312 * might be 8 or 16-bit but should always have two channels; gray plus alpha.
3313 */
3314 if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
3315 png_error(png_ptr, "lost rgb to gray");
3316
3317 if ((png_ptr->transformations & PNG_COMPOSE) != 0)
3318 png_error(png_ptr, "unexpected compose");
3319
3320 if (png_get_channels(png_ptr, info_ptr) != 2)
3321 png_error(png_ptr, "lost/gained channels");
3322
3323 /* Expect the 8-bit case to always remove the alpha channel */
3324 if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
3325 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
3326 png_error(png_ptr, "unexpected 8-bit transformation");
3327
3328 switch (png_ptr->interlaced)
3329 {
3330 case PNG_INTERLACE_NONE:
3331 passes = 1;
3332 break;
3333
3334 case PNG_INTERLACE_ADAM7:
3335 passes = PNG_INTERLACE_ADAM7_PASSES;
3336 break;
3337
3338 default:
3339 png_error(png_ptr, "unknown interlace type");
3340 }
3341
3342 /* Use direct access to info_ptr here because otherwise the simplified API
3343 * would require PNG_EASY_ACCESS_SUPPORTED (just for this.) Note this is
3344 * checking the value after libpng expansions, not the original value in the
3345 * PNG.
3346 */
3347 switch (info_ptr->bit_depth)
3348 {
3349 default:
3350 png_error(png_ptr, "unexpected bit depth");
3351 break;
3352
3353 case 8:
3354 /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
3355 * to be removed by composing on a background: either the row if
3356 * display->background is NULL or display->background->green if not.
3357 * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
3358 */
3359 {
3360 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
3361 ptrdiff_t step_row = display->row_bytes;
3362
3363 for (pass = 0; pass < passes; ++pass)
3364 {
3365 png_bytep row = png_voidcast(png_bytep,
3366 display->first_row);
3367 unsigned int startx, stepx, stepy;
3368 png_uint_32 y;
3369
3370 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3371 {
3372 /* The row may be empty for a short image: */
3373 if (PNG_PASS_COLS(width, pass) == 0)
3374 continue;
3375
3376 startx = PNG_PASS_START_COL(pass);
3377 stepx = PNG_PASS_COL_OFFSET(pass);
3378 y = PNG_PASS_START_ROW(pass);
3379 stepy = PNG_PASS_ROW_OFFSET(pass);
3380 }
3381
3382 else
3383 {
3384 y = 0;
3385 startx = 0;
3386 stepx = stepy = 1;
3387 }
3388
3389 if (display->background == NULL)
3390 {
3391 for (; y<height; y += stepy)
3392 {
3393 png_bytep inrow = png_voidcast(png_bytep,
3394 display->local_row);
3395 png_bytep outrow = first_row + y * step_row;
3396 png_const_bytep end_row = outrow + width;
3397
3398 /* Read the row, which is packed: */
3399 png_read_row(png_ptr, inrow, NULL);
3400
3401 /* Now do the composition on each pixel in this row. */
3402 outrow += startx;
3403 for (; outrow < end_row; outrow += stepx)
3404 {
3405 png_byte alpha = inrow[1];
3406
3407 if (alpha > 0) /* else no change to the output */
3408 {
3409 png_uint_32 component = inrow[0];
3410
3411 if (alpha < 255) /* else just use component */
3412 {
3413 /* Since PNG_OPTIMIZED_ALPHA was not set it is
3414 * necessary to invert the sRGB transfer
3415 * function and multiply the alpha out.
3416 */
3417 component = png_sRGB_table[component] * alpha;
3418 component += png_sRGB_table[outrow[0]] *
3419 (255-alpha);
3420 component = PNG_sRGB_FROM_LINEAR(component);
3421 }
3422
3423 outrow[0] = (png_byte)component;
3424 }
3425
3426 inrow += 2; /* gray and alpha channel */
3427 }
3428 }
3429 }
3430
3431 else /* constant background value */
3432 {
3433 png_byte background8 = display->background->green;
3434 png_uint_16 background = png_sRGB_table[background8];
3435
3436 for (; y<height; y += stepy)
3437 {
3438 png_bytep inrow = png_voidcast(png_bytep,
3439 display->local_row);
3440 png_bytep outrow = first_row + y * step_row;
3441 png_const_bytep end_row = outrow + width;
3442
3443 /* Read the row, which is packed: */
3444 png_read_row(png_ptr, inrow, NULL);
3445
3446 /* Now do the composition on each pixel in this row. */
3447 outrow += startx;
3448 for (; outrow < end_row; outrow += stepx)
3449 {
3450 png_byte alpha = inrow[1];
3451
3452 if (alpha > 0) /* else use background */
3453 {
3454 png_uint_32 component = inrow[0];
3455
3456 if (alpha < 255) /* else just use component */
3457 {
3458 component = png_sRGB_table[component] * alpha;
3459 component += background * (255-alpha);
3460 component = PNG_sRGB_FROM_LINEAR(component);
3461 }
3462
3463 outrow[0] = (png_byte)component;
3464 }
3465
3466 else
3467 outrow[0] = background8;
3468
3469 inrow += 2; /* gray and alpha channel */
3470 }
3471
3472 row += display->row_bytes;
3473 }
3474 }
3475 }
3476 }
3477 break;
3478
3479 case 16:
3480 /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
3481 * still be done and, maybe, the alpha channel removed. This code also
3482 * handles the alpha-first option.
3483 */
3484 {
3485 png_uint_16p first_row = png_voidcast(png_uint_16p,
3486 display->first_row);
3487 /* The division by two is safe because the caller passed in a
3488 * stride which was multiplied by 2 (below) to get row_bytes.
3489 */
3490 ptrdiff_t step_row = display->row_bytes / 2;
3491 int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
3492 unsigned int outchannels = 1+preserve_alpha;
3493 int swap_alpha = 0;
3494
3495 # ifdef PNG_SIMPLIFIED_READ_AFIRST_SUPPORTED
3496 if (preserve_alpha && (image->format & PNG_FORMAT_FLAG_AFIRST))
3497 swap_alpha = 1;
3498 # endif
3499
3500 for (pass = 0; pass < passes; ++pass)
3501 {
3502 unsigned int startx, stepx, stepy;
3503 png_uint_32 y;
3504
3505 /* The 'x' start and step are adjusted to output components here.
3506 */
3507 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
3508 {
3509 /* The row may be empty for a short image: */
3510 if (PNG_PASS_COLS(width, pass) == 0)
3511 continue;
3512
3513 startx = PNG_PASS_START_COL(pass) * outchannels;
3514 stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
3515 y = PNG_PASS_START_ROW(pass);
3516 stepy = PNG_PASS_ROW_OFFSET(pass);
3517 }
3518
3519 else
3520 {
3521 y = 0;
3522 startx = 0;
3523 stepx = outchannels;
3524 stepy = 1;
3525 }
3526
3527 for (; y<height; y += stepy)
3528 {
3529 png_const_uint_16p inrow;
3530 png_uint_16p outrow = first_row + y*step_row;
3531 png_uint_16p end_row = outrow + width * outchannels;
3532
3533 /* Read the row, which is packed: */
3534 png_read_row(png_ptr, png_voidcast(png_bytep,
3535 display->local_row), NULL);
3536 inrow = png_voidcast(png_const_uint_16p, display->local_row);
3537
3538 /* Now do the pre-multiplication on each pixel in this row.
3539 */
3540 outrow += startx;
3541 for (; outrow < end_row; outrow += stepx)
3542 {
3543 png_uint_32 component = inrow[0];
3544 png_uint_16 alpha = inrow[1];
3545
3546 if (alpha > 0) /* else 0 */
3547 {
3548 if (alpha < 65535) /* else just use component */
3549 {
3550 component *= alpha;
3551 component += 32767;
3552 component /= 65535;
3553 }
3554 }
3555
3556 else
3557 component = 0;
3558
3559 outrow[swap_alpha] = (png_uint_16)component;
3560 if (preserve_alpha)
3561 outrow[1 ^ swap_alpha] = alpha;
3562
3563 inrow += 2; /* components and alpha channel */
3564 }
3565 }
3566 }
3567 }
3568 break;
3569 }
3570
3571 return 1;
3572 }
3573
3574 /* The guts of png_image_finish_read as a png_safe_execute callback. */
3575 static int
png_image_read_direct(png_voidp argument)3576 png_image_read_direct(png_voidp argument)
3577 {
3578 png_image_read_control *display = png_voidcast(png_image_read_control*,
3579 argument);
3580 png_imagep image = display->image;
3581 png_structrp png_ptr = image->opaque->png_ptr;
3582 png_inforp info_ptr = image->opaque->info_ptr;
3583
3584 png_uint_32 format = image->format;
3585 int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
3586 int do_local_compose = 0;
3587 int do_local_background = 0; /* to avoid double gamma correction bug */
3588 int passes = 0;
3589
3590 /* Add transforms to ensure the correct output format is produced then check
3591 * that the required implementation support is there. Always expand; always
3592 * need 8 bits minimum, no palette and expanded tRNS.
3593 */
3594 png_set_expand(png_ptr);
3595
3596 /* Now check the format to see if it was modified. */
3597 {
3598 png_uint_32 base_format = png_image_format(png_ptr) &
3599 ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
3600 png_uint_32 change = format ^ base_format;
3601 png_fixed_point output_gamma;
3602 int mode; /* alpha mode */
3603
3604 /* Do this first so that we have a record if rgb to gray is happening. */
3605 if (change & PNG_FORMAT_FLAG_COLOR)
3606 {
3607 /* gray<->color transformation required. */
3608 if (format & PNG_FORMAT_FLAG_COLOR)
3609 png_set_gray_to_rgb(png_ptr);
3610
3611 else
3612 {
3613 /* libpng can't do both rgb to gray and
3614 * background/pre-multiplication if there is also significant gamma
3615 * correction, because both operations require linear colors and
3616 * the code only supports one transform doing the gamma correction.
3617 * Handle this by doing the pre-multiplication or background
3618 * operation in this code, if necessary.
3619 *
3620 * TODO: fix this by rewriting pngrtran.c (!)
3621 *
3622 * For the moment (given that fixing this in pngrtran.c is an
3623 * enormous change) 'do_local_background' is used to indicate that
3624 * the problem exists.
3625 */
3626 if (base_format & PNG_FORMAT_FLAG_ALPHA)
3627 do_local_background = 1/*maybe*/;
3628
3629 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
3630 PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
3631 }
3632
3633 change &= ~PNG_FORMAT_FLAG_COLOR;
3634 }
3635
3636 /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
3637 */
3638 {
3639 png_fixed_point input_gamma_default;
3640
3641 if ((base_format & PNG_FORMAT_FLAG_LINEAR) &&
3642 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
3643 input_gamma_default = PNG_GAMMA_LINEAR;
3644 else
3645 input_gamma_default = PNG_DEFAULT_sRGB;
3646
3647 /* Call png_set_alpha_mode to set the default for the input gamma; the
3648 * output gamma is set by a second call below.
3649 */
3650 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
3651 }
3652
3653 if (linear)
3654 {
3655 /* If there *is* an alpha channel in the input it must be multiplied
3656 * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
3657 */
3658 if (base_format & PNG_FORMAT_FLAG_ALPHA)
3659 mode = PNG_ALPHA_STANDARD; /* associated alpha */
3660
3661 else
3662 mode = PNG_ALPHA_PNG;
3663
3664 output_gamma = PNG_GAMMA_LINEAR;
3665 }
3666
3667 else
3668 {
3669 mode = PNG_ALPHA_PNG;
3670 output_gamma = PNG_DEFAULT_sRGB;
3671 }
3672
3673 /* If 'do_local_background' is set check for the presence of gamma
3674 * correction; this is part of the work-round for the libpng bug
3675 * described above.
3676 *
3677 * TODO: fix libpng and remove this.
3678 */
3679 if (do_local_background)
3680 {
3681 png_fixed_point gtest;
3682
3683 /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
3684 * gamma correction, the screen gamma hasn't been set on png_struct
3685 * yet; it's set below. png_struct::gamma, however, is set to the
3686 * final value.
3687 */
3688 if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
3689 PNG_FP_1) && !png_gamma_significant(gtest))
3690 do_local_background = 0;
3691
3692 else if (mode == PNG_ALPHA_STANDARD)
3693 {
3694 do_local_background = 2/*required*/;
3695 mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
3696 }
3697
3698 /* else leave as 1 for the checks below */
3699 }
3700
3701 /* If the bit-depth changes then handle that here. */
3702 if (change & PNG_FORMAT_FLAG_LINEAR)
3703 {
3704 if (linear /*16-bit output*/)
3705 png_set_expand_16(png_ptr);
3706
3707 else /* 8-bit output */
3708 png_set_scale_16(png_ptr);
3709
3710 change &= ~PNG_FORMAT_FLAG_LINEAR;
3711 }
3712
3713 /* Now the background/alpha channel changes. */
3714 if (change & PNG_FORMAT_FLAG_ALPHA)
3715 {
3716 /* Removing an alpha channel requires composition for the 8-bit
3717 * formats; for the 16-bit it is already done, above, by the
3718 * pre-multiplication and the channel just needs to be stripped.
3719 */
3720 if (base_format & PNG_FORMAT_FLAG_ALPHA)
3721 {
3722 /* If RGB->gray is happening the alpha channel must be left and the
3723 * operation completed locally.
3724 *
3725 * TODO: fix libpng and remove this.
3726 */
3727 if (do_local_background)
3728 do_local_background = 2/*required*/;
3729
3730 /* 16-bit output: just remove the channel */
3731 else if (linear) /* compose on black (well, pre-multiply) */
3732 png_set_strip_alpha(png_ptr);
3733
3734 /* 8-bit output: do an appropriate compose */
3735 else if (display->background != NULL)
3736 {
3737 png_color_16 c;
3738
3739 c.index = 0; /*unused*/
3740 c.red = display->background->red;
3741 c.green = display->background->green;
3742 c.blue = display->background->blue;
3743 c.gray = display->background->green;
3744
3745 /* This is always an 8-bit sRGB value, using the 'green' channel
3746 * for gray is much better than calculating the luminance here;
3747 * we can get off-by-one errors in that calculation relative to
3748 * the app expectations and that will show up in transparent
3749 * pixels.
3750 */
3751 png_set_background_fixed(png_ptr, &c,
3752 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
3753 0/*gamma: not used*/);
3754 }
3755
3756 else /* compose on row: implemented below. */
3757 {
3758 do_local_compose = 1;
3759 /* This leaves the alpha channel in the output, so it has to be
3760 * removed by the code below. Set the encoding to the 'OPTIMIZE'
3761 * one so the code only has to hack on the pixels that require
3762 * composition.
3763 */
3764 mode = PNG_ALPHA_OPTIMIZED;
3765 }
3766 }
3767
3768 else /* output needs an alpha channel */
3769 {
3770 /* This is tricky because it happens before the swap operation has
3771 * been accomplished; however, the swap does *not* swap the added
3772 * alpha channel (weird API), so it must be added in the correct
3773 * place.
3774 */
3775 png_uint_32 filler; /* opaque filler */
3776 int where;
3777
3778 if (linear)
3779 filler = 65535;
3780
3781 else
3782 filler = 255;
3783
3784 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3785 if (format & PNG_FORMAT_FLAG_AFIRST)
3786 {
3787 where = PNG_FILLER_BEFORE;
3788 change &= ~PNG_FORMAT_FLAG_AFIRST;
3789 }
3790
3791 else
3792 # endif
3793 where = PNG_FILLER_AFTER;
3794
3795 png_set_add_alpha(png_ptr, filler, where);
3796 }
3797
3798 /* This stops the (irrelevant) call to swap_alpha below. */
3799 change &= ~PNG_FORMAT_FLAG_ALPHA;
3800 }
3801
3802 /* Now set the alpha mode correctly; this is always done, even if there is
3803 * no alpha channel in either the input or the output because it correctly
3804 * sets the output gamma.
3805 */
3806 png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
3807
3808 # ifdef PNG_FORMAT_BGR_SUPPORTED
3809 if (change & PNG_FORMAT_FLAG_BGR)
3810 {
3811 /* Check only the output format; PNG is never BGR; don't do this if
3812 * the output is gray, but fix up the 'format' value in that case.
3813 */
3814 if (format & PNG_FORMAT_FLAG_COLOR)
3815 png_set_bgr(png_ptr);
3816
3817 else
3818 format &= ~PNG_FORMAT_FLAG_BGR;
3819
3820 change &= ~PNG_FORMAT_FLAG_BGR;
3821 }
3822 # endif
3823
3824 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3825 if (change & PNG_FORMAT_FLAG_AFIRST)
3826 {
3827 /* Only relevant if there is an alpha channel - it's particularly
3828 * important to handle this correctly because do_local_compose may
3829 * be set above and then libpng will keep the alpha channel for this
3830 * code to remove.
3831 */
3832 if (format & PNG_FORMAT_FLAG_ALPHA)
3833 {
3834 /* Disable this if doing a local background,
3835 * TODO: remove this when local background is no longer required.
3836 */
3837 if (do_local_background != 2)
3838 png_set_swap_alpha(png_ptr);
3839 }
3840
3841 else
3842 format &= ~PNG_FORMAT_FLAG_AFIRST;
3843
3844 change &= ~PNG_FORMAT_FLAG_AFIRST;
3845 }
3846 # endif
3847
3848 /* If the *output* is 16-bit then we need to check for a byte-swap on this
3849 * architecture.
3850 */
3851 if (linear)
3852 {
3853 PNG_CONST png_uint_16 le = 0x0001;
3854
3855 if (*(png_const_bytep)&le)
3856 png_set_swap(png_ptr);
3857 }
3858
3859 /* If change is not now 0 some transformation is missing - error out. */
3860 if (change)
3861 png_error(png_ptr, "png_read_image: unsupported transformation");
3862 }
3863
3864 PNG_SKIP_CHUNKS(png_ptr);
3865
3866 /* Update the 'info' structure and make sure the result is as required; first
3867 * make sure to turn on the interlace handling if it will be required
3868 * (because it can't be turned on *after* the call to png_read_update_info!)
3869 *
3870 * TODO: remove the do_local_background fixup below.
3871 */
3872 if (!do_local_compose && do_local_background != 2)
3873 passes = png_set_interlace_handling(png_ptr);
3874
3875 png_read_update_info(png_ptr, info_ptr);
3876
3877 {
3878 png_uint_32 info_format = 0;
3879
3880 if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
3881 info_format |= PNG_FORMAT_FLAG_COLOR;
3882
3883 if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
3884 {
3885 /* do_local_compose removes this channel below. */
3886 if (!do_local_compose)
3887 {
3888 /* do_local_background does the same if required. */
3889 if (do_local_background != 2 ||
3890 (format & PNG_FORMAT_FLAG_ALPHA) != 0)
3891 info_format |= PNG_FORMAT_FLAG_ALPHA;
3892 }
3893 }
3894
3895 else if (do_local_compose) /* internal error */
3896 png_error(png_ptr, "png_image_read: alpha channel lost");
3897
3898 if (info_ptr->bit_depth == 16)
3899 info_format |= PNG_FORMAT_FLAG_LINEAR;
3900
3901 # ifdef PNG_FORMAT_BGR_SUPPORTED
3902 if (png_ptr->transformations & PNG_BGR)
3903 info_format |= PNG_FORMAT_FLAG_BGR;
3904 # endif
3905
3906 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
3907 if (do_local_background == 2)
3908 {
3909 if (format & PNG_FORMAT_FLAG_AFIRST)
3910 info_format |= PNG_FORMAT_FLAG_AFIRST;
3911 }
3912
3913 if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
3914 ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
3915 (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
3916 {
3917 if (do_local_background == 2)
3918 png_error(png_ptr, "unexpected alpha swap transformation");
3919
3920 info_format |= PNG_FORMAT_FLAG_AFIRST;
3921 }
3922 # endif
3923
3924 /* This is actually an internal error. */
3925 if (info_format != format)
3926 png_error(png_ptr, "png_read_image: invalid transformations");
3927 }
3928
3929 /* Now read the rows. If do_local_compose is set then it is necessary to use
3930 * a local row buffer. The output will be GA, RGBA or BGRA and must be
3931 * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
3932 * display acts as a flag.
3933 */
3934 {
3935 png_voidp first_row = display->buffer;
3936 ptrdiff_t row_bytes = display->row_stride;
3937
3938 if (linear)
3939 row_bytes *= 2;
3940
3941 /* The following expression is designed to work correctly whether it gives
3942 * a signed or an unsigned result.
3943 */
3944 if (row_bytes < 0)
3945 {
3946 char *ptr = png_voidcast(char*, first_row);
3947 ptr += (image->height-1) * (-row_bytes);
3948 first_row = png_voidcast(png_voidp, ptr);
3949 }
3950
3951 display->first_row = first_row;
3952 display->row_bytes = row_bytes;
3953 }
3954
3955 if (do_local_compose)
3956 {
3957 int result;
3958 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3959
3960 display->local_row = row;
3961 result = png_safe_execute(image, png_image_read_composite, display);
3962 display->local_row = NULL;
3963 png_free(png_ptr, row);
3964
3965 return result;
3966 }
3967
3968 else if (do_local_background == 2)
3969 {
3970 int result;
3971 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3972
3973 display->local_row = row;
3974 result = png_safe_execute(image, png_image_read_background, display);
3975 display->local_row = NULL;
3976 png_free(png_ptr, row);
3977
3978 return result;
3979 }
3980
3981 else
3982 {
3983 png_alloc_size_t row_bytes = display->row_bytes;
3984
3985 while (--passes >= 0)
3986 {
3987 png_uint_32 y = image->height;
3988 png_bytep row = png_voidcast(png_bytep, display->first_row);
3989
3990 while (y-- > 0)
3991 {
3992 png_read_row(png_ptr, row, NULL);
3993 row += row_bytes;
3994 }
3995 }
3996
3997 return 1;
3998 }
3999 }
4000
4001 int PNGAPI
png_image_finish_read(png_imagep image,png_const_colorp background,void * buffer,png_int_32 row_stride,void * colormap)4002 png_image_finish_read(png_imagep image, png_const_colorp background,
4003 void *buffer, png_int_32 row_stride, void *colormap)
4004 {
4005 if (image != NULL && image->version == PNG_IMAGE_VERSION)
4006 {
4007 png_uint_32 check;
4008
4009 if (row_stride == 0)
4010 row_stride = PNG_IMAGE_ROW_STRIDE(*image);
4011
4012 if (row_stride < 0)
4013 check = -row_stride;
4014
4015 else
4016 check = row_stride;
4017
4018 if (image->opaque != NULL && buffer != NULL &&
4019 check >= PNG_IMAGE_ROW_STRIDE(*image))
4020 {
4021 if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
4022 (image->colormap_entries > 0 && colormap != NULL))
4023 {
4024 int result;
4025 png_image_read_control display;
4026
4027 memset(&display, 0, (sizeof display));
4028 display.image = image;
4029 display.buffer = buffer;
4030 display.row_stride = row_stride;
4031 display.colormap = colormap;
4032 display.background = background;
4033 display.local_row = NULL;
4034
4035 /* Choose the correct 'end' routine; for the color-map case all the
4036 * setup has already been done.
4037 */
4038 if (image->format & PNG_FORMAT_FLAG_COLORMAP)
4039 result =
4040 png_safe_execute(image, png_image_read_colormap, &display) &&
4041 png_safe_execute(image, png_image_read_colormapped, &display);
4042
4043 else
4044 result =
4045 png_safe_execute(image, png_image_read_direct, &display);
4046
4047 png_image_free(image);
4048 return result;
4049 }
4050
4051 else
4052 return png_image_error(image,
4053 "png_image_finish_read[color-map]: no color-map");
4054 }
4055
4056 else
4057 return png_image_error(image,
4058 "png_image_finish_read: invalid argument");
4059 }
4060
4061 else if (image != NULL)
4062 return png_image_error(image,
4063 "png_image_finish_read: damaged PNG_IMAGE_VERSION");
4064
4065 return 0;
4066 }
4067
4068 #endif /* PNG_SIMPLIFIED_READ_SUPPORTED */
4069 #endif /* PNG_READ_SUPPORTED */
4070