[LIBPNG]
[reactos.git] / reactos / dll / 3rdparty / libpng / pngread.c
1
2 /* pngread.c - read a PNG file
3 *
4 * Last changed in libpng 1.6.32 [August 24, 2017]
5 * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
8 *
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
12 *
13 * This file contains routines that an application calls directly to
14 * read a PNG file or stream.
15 */
16
17 #include "pngpriv.h"
18 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
19 # include <errno.h>
20 #endif
21
22 #ifdef PNG_READ_SUPPORTED
23
24 /* Create a PNG structure for reading, and allocate any memory needed. */
25 PNG_FUNCTION(png_structp,PNGAPI
26 png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
27 png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
28 {
29 #ifndef PNG_USER_MEM_SUPPORTED
30 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
31 error_fn, warn_fn, NULL, NULL, NULL);
32 #else
33 return png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
34 warn_fn, NULL, NULL, NULL);
35 }
36
37 /* Alternate create PNG structure for reading, and allocate any memory
38 * needed.
39 */
40 PNG_FUNCTION(png_structp,PNGAPI
41 png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
42 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
43 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
44 {
45 png_structp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
46 error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
47 #endif /* USER_MEM */
48
49 if (png_ptr != NULL)
50 {
51 png_ptr->mode = PNG_IS_READ_STRUCT;
52
53 /* Added in libpng-1.6.0; this can be used to detect a read structure if
54 * required (it will be zero in a write structure.)
55 */
56 # ifdef PNG_SEQUENTIAL_READ_SUPPORTED
57 png_ptr->IDAT_read_size = PNG_IDAT_READ_SIZE;
58 # endif
59
60 # ifdef PNG_BENIGN_READ_ERRORS_SUPPORTED
61 png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
62
63 /* In stable builds only warn if an application error can be completely
64 * handled.
65 */
66 # if PNG_RELEASE_BUILD
67 png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
68 # endif
69 # endif
70
71 /* TODO: delay this, it can be done in png_init_io (if the app doesn't
72 * do it itself) avoiding setting the default function if it is not
73 * required.
74 */
75 png_set_read_fn(png_ptr, NULL, NULL);
76 }
77
78 return png_ptr;
79 }
80
81
82 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
83 /* Read the information before the actual image data. This has been
84 * changed in v0.90 to allow reading a file that already has the magic
85 * bytes read from the stream. You can tell libpng how many bytes have
86 * been read from the beginning of the stream (up to the maximum of 8)
87 * via png_set_sig_bytes(), and we will only check the remaining bytes
88 * here. The application can then have access to the signature bytes we
89 * read if it is determined that this isn't a valid PNG file.
90 */
91 void PNGAPI
92 png_read_info(png_structrp png_ptr, png_inforp info_ptr)
93 {
94 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
95 int keep;
96 #endif
97
98 png_debug(1, "in png_read_info");
99
100 if (png_ptr == NULL || info_ptr == NULL)
101 return;
102
103 /* Read and check the PNG file signature. */
104 png_read_sig(png_ptr, info_ptr);
105
106 for (;;)
107 {
108 png_uint_32 length = png_read_chunk_header(png_ptr);
109 png_uint_32 chunk_name = png_ptr->chunk_name;
110
111 /* IDAT logic needs to happen here to simplify getting the two flags
112 * right.
113 */
114 if (chunk_name == png_IDAT)
115 {
116 if ((png_ptr->mode & PNG_HAVE_IHDR) == 0)
117 png_chunk_error(png_ptr, "Missing IHDR before IDAT");
118
119 else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
120 (png_ptr->mode & PNG_HAVE_PLTE) == 0)
121 png_chunk_error(png_ptr, "Missing PLTE before IDAT");
122
123 else if ((png_ptr->mode & PNG_AFTER_IDAT) != 0)
124 png_chunk_benign_error(png_ptr, "Too many IDATs found");
125
126 png_ptr->mode |= PNG_HAVE_IDAT;
127 }
128
129 else if ((png_ptr->mode & PNG_HAVE_IDAT) != 0)
130 {
131 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
132 png_ptr->mode |= PNG_AFTER_IDAT;
133 }
134
135 /* This should be a binary subdivision search or a hash for
136 * matching the chunk name rather than a linear search.
137 */
138 if (chunk_name == png_IHDR)
139 png_handle_IHDR(png_ptr, info_ptr, length);
140
141 else if (chunk_name == png_IEND)
142 png_handle_IEND(png_ptr, info_ptr, length);
143
144 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
145 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
146 {
147 png_handle_unknown(png_ptr, info_ptr, length, keep);
148
149 if (chunk_name == png_PLTE)
150 png_ptr->mode |= PNG_HAVE_PLTE;
151
152 else if (chunk_name == png_IDAT)
153 {
154 png_ptr->idat_size = 0; /* It has been consumed */
155 break;
156 }
157 }
158 #endif
159 else if (chunk_name == png_PLTE)
160 png_handle_PLTE(png_ptr, info_ptr, length);
161
162 else if (chunk_name == png_IDAT)
163 {
164 png_ptr->idat_size = length;
165 break;
166 }
167
168 #ifdef PNG_READ_bKGD_SUPPORTED
169 else if (chunk_name == png_bKGD)
170 png_handle_bKGD(png_ptr, info_ptr, length);
171 #endif
172
173 #ifdef PNG_READ_cHRM_SUPPORTED
174 else if (chunk_name == png_cHRM)
175 png_handle_cHRM(png_ptr, info_ptr, length);
176 #endif
177
178 #ifdef PNG_READ_eXIf_SUPPORTED
179 else if (chunk_name == png_eXIf)
180 png_handle_eXIf(png_ptr, info_ptr, length);
181 #endif
182
183 #ifdef PNG_READ_gAMA_SUPPORTED
184 else if (chunk_name == png_gAMA)
185 png_handle_gAMA(png_ptr, info_ptr, length);
186 #endif
187
188 #ifdef PNG_READ_hIST_SUPPORTED
189 else if (chunk_name == png_hIST)
190 png_handle_hIST(png_ptr, info_ptr, length);
191 #endif
192
193 #ifdef PNG_READ_oFFs_SUPPORTED
194 else if (chunk_name == png_oFFs)
195 png_handle_oFFs(png_ptr, info_ptr, length);
196 #endif
197
198 #ifdef PNG_READ_pCAL_SUPPORTED
199 else if (chunk_name == png_pCAL)
200 png_handle_pCAL(png_ptr, info_ptr, length);
201 #endif
202
203 #ifdef PNG_READ_sCAL_SUPPORTED
204 else if (chunk_name == png_sCAL)
205 png_handle_sCAL(png_ptr, info_ptr, length);
206 #endif
207
208 #ifdef PNG_READ_pHYs_SUPPORTED
209 else if (chunk_name == png_pHYs)
210 png_handle_pHYs(png_ptr, info_ptr, length);
211 #endif
212
213 #ifdef PNG_READ_sBIT_SUPPORTED
214 else if (chunk_name == png_sBIT)
215 png_handle_sBIT(png_ptr, info_ptr, length);
216 #endif
217
218 #ifdef PNG_READ_sRGB_SUPPORTED
219 else if (chunk_name == png_sRGB)
220 png_handle_sRGB(png_ptr, info_ptr, length);
221 #endif
222
223 #ifdef PNG_READ_iCCP_SUPPORTED
224 else if (chunk_name == png_iCCP)
225 png_handle_iCCP(png_ptr, info_ptr, length);
226 #endif
227
228 #ifdef PNG_READ_sPLT_SUPPORTED
229 else if (chunk_name == png_sPLT)
230 png_handle_sPLT(png_ptr, info_ptr, length);
231 #endif
232
233 #ifdef PNG_READ_tEXt_SUPPORTED
234 else if (chunk_name == png_tEXt)
235 png_handle_tEXt(png_ptr, info_ptr, length);
236 #endif
237
238 #ifdef PNG_READ_tIME_SUPPORTED
239 else if (chunk_name == png_tIME)
240 png_handle_tIME(png_ptr, info_ptr, length);
241 #endif
242
243 #ifdef PNG_READ_tRNS_SUPPORTED
244 else if (chunk_name == png_tRNS)
245 png_handle_tRNS(png_ptr, info_ptr, length);
246 #endif
247
248 #ifdef PNG_READ_zTXt_SUPPORTED
249 else if (chunk_name == png_zTXt)
250 png_handle_zTXt(png_ptr, info_ptr, length);
251 #endif
252
253 #ifdef PNG_READ_iTXt_SUPPORTED
254 else if (chunk_name == png_iTXt)
255 png_handle_iTXt(png_ptr, info_ptr, length);
256 #endif
257
258 else
259 png_handle_unknown(png_ptr, info_ptr, length,
260 PNG_HANDLE_CHUNK_AS_DEFAULT);
261 }
262 }
263 #endif /* SEQUENTIAL_READ */
264
265 /* Optional call to update the users info_ptr structure */
266 void PNGAPI
267 png_read_update_info(png_structrp png_ptr, png_inforp info_ptr)
268 {
269 png_debug(1, "in png_read_update_info");
270
271 if (png_ptr != NULL)
272 {
273 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
274 {
275 png_read_start_row(png_ptr);
276
277 # ifdef PNG_READ_TRANSFORMS_SUPPORTED
278 png_read_transform_info(png_ptr, info_ptr);
279 # else
280 PNG_UNUSED(info_ptr)
281 # endif
282 }
283
284 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
285 else
286 png_app_error(png_ptr,
287 "png_read_update_info/png_start_read_image: duplicate call");
288 }
289 }
290
291 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
292 /* Initialize palette, background, etc, after transformations
293 * are set, but before any reading takes place. This allows
294 * the user to obtain a gamma-corrected palette, for example.
295 * If the user doesn't call this, we will do it ourselves.
296 */
297 void PNGAPI
298 png_start_read_image(png_structrp png_ptr)
299 {
300 png_debug(1, "in png_start_read_image");
301
302 if (png_ptr != NULL)
303 {
304 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
305 png_read_start_row(png_ptr);
306
307 /* New in 1.6.0 this avoids the bug of doing the initializations twice */
308 else
309 png_app_error(png_ptr,
310 "png_start_read_image/png_read_update_info: duplicate call");
311 }
312 }
313 #endif /* SEQUENTIAL_READ */
314
315 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
316 #ifdef PNG_MNG_FEATURES_SUPPORTED
317 /* Undoes intrapixel differencing,
318 * NOTE: this is apparently only supported in the 'sequential' reader.
319 */
320 static void
321 png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
322 {
323 png_debug(1, "in png_do_read_intrapixel");
324
325 if (
326 (row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
327 {
328 int bytes_per_pixel;
329 png_uint_32 row_width = row_info->width;
330
331 if (row_info->bit_depth == 8)
332 {
333 png_bytep rp;
334 png_uint_32 i;
335
336 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
337 bytes_per_pixel = 3;
338
339 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
340 bytes_per_pixel = 4;
341
342 else
343 return;
344
345 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
346 {
347 *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
348 *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
349 }
350 }
351 else if (row_info->bit_depth == 16)
352 {
353 png_bytep rp;
354 png_uint_32 i;
355
356 if (row_info->color_type == PNG_COLOR_TYPE_RGB)
357 bytes_per_pixel = 6;
358
359 else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
360 bytes_per_pixel = 8;
361
362 else
363 return;
364
365 for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
366 {
367 png_uint_32 s0 = (png_uint_32)(*(rp ) << 8) | *(rp + 1);
368 png_uint_32 s1 = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
369 png_uint_32 s2 = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
370 png_uint_32 red = (s0 + s1 + 65536) & 0xffff;
371 png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
372 *(rp ) = (png_byte)((red >> 8) & 0xff);
373 *(rp + 1) = (png_byte)(red & 0xff);
374 *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
375 *(rp + 5) = (png_byte)(blue & 0xff);
376 }
377 }
378 }
379 }
380 #endif /* MNG_FEATURES */
381
382 void PNGAPI
383 png_read_row(png_structrp png_ptr, png_bytep row, png_bytep dsp_row)
384 {
385 png_row_info row_info;
386
387 if (png_ptr == NULL)
388 return;
389
390 png_debug2(1, "in png_read_row (row %lu, pass %d)",
391 (unsigned long)png_ptr->row_number, png_ptr->pass);
392
393 /* png_read_start_row sets the information (in particular iwidth) for this
394 * interlace pass.
395 */
396 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
397 png_read_start_row(png_ptr);
398
399 /* 1.5.6: row_info moved out of png_struct to a local here. */
400 row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
401 row_info.color_type = png_ptr->color_type;
402 row_info.bit_depth = png_ptr->bit_depth;
403 row_info.channels = png_ptr->channels;
404 row_info.pixel_depth = png_ptr->pixel_depth;
405 row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);
406
407 #ifdef PNG_WARNINGS_SUPPORTED
408 if (png_ptr->row_number == 0 && png_ptr->pass == 0)
409 {
410 /* Check for transforms that have been set but were defined out */
411 #if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
412 if ((png_ptr->transformations & PNG_INVERT_MONO) != 0)
413 png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
414 #endif
415
416 #if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
417 if ((png_ptr->transformations & PNG_FILLER) != 0)
418 png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
419 #endif
420
421 #if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
422 !defined(PNG_READ_PACKSWAP_SUPPORTED)
423 if ((png_ptr->transformations & PNG_PACKSWAP) != 0)
424 png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
425 #endif
426
427 #if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
428 if ((png_ptr->transformations & PNG_PACK) != 0)
429 png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
430 #endif
431
432 #if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
433 if ((png_ptr->transformations & PNG_SHIFT) != 0)
434 png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
435 #endif
436
437 #if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
438 if ((png_ptr->transformations & PNG_BGR) != 0)
439 png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
440 #endif
441
442 #if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
443 if ((png_ptr->transformations & PNG_SWAP_BYTES) != 0)
444 png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
445 #endif
446 }
447 #endif /* WARNINGS */
448
449 #ifdef PNG_READ_INTERLACING_SUPPORTED
450 /* If interlaced and we do not need a new row, combine row and return.
451 * Notice that the pixels we have from previous rows have been transformed
452 * already; we can only combine like with like (transformed or
453 * untransformed) and, because of the libpng API for interlaced images, this
454 * means we must transform before de-interlacing.
455 */
456 if (png_ptr->interlaced != 0 &&
457 (png_ptr->transformations & PNG_INTERLACE) != 0)
458 {
459 switch (png_ptr->pass)
460 {
461 case 0:
462 if (png_ptr->row_number & 0x07)
463 {
464 if (dsp_row != NULL)
465 png_combine_row(png_ptr, dsp_row, 1/*display*/);
466 png_read_finish_row(png_ptr);
467 return;
468 }
469 break;
470
471 case 1:
472 if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
473 {
474 if (dsp_row != NULL)
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 2:
483 if ((png_ptr->row_number & 0x07) != 4)
484 {
485 if (dsp_row != NULL && (png_ptr->row_number & 4))
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 3:
494 if ((png_ptr->row_number & 3) || png_ptr->width < 3)
495 {
496 if (dsp_row != NULL)
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 4:
505 if ((png_ptr->row_number & 3) != 2)
506 {
507 if (dsp_row != NULL && (png_ptr->row_number & 2))
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 case 5:
516 if ((png_ptr->row_number & 1) || png_ptr->width < 2)
517 {
518 if (dsp_row != NULL)
519 png_combine_row(png_ptr, dsp_row, 1/*display*/);
520
521 png_read_finish_row(png_ptr);
522 return;
523 }
524 break;
525
526 default:
527 case 6:
528 if ((png_ptr->row_number & 1) == 0)
529 {
530 png_read_finish_row(png_ptr);
531 return;
532 }
533 break;
534 }
535 }
536 #endif
537
538 if ((png_ptr->mode & PNG_HAVE_IDAT) == 0)
539 png_error(png_ptr, "Invalid attempt to read row data");
540
541 /* Fill the row with IDAT data: */
542 png_ptr->row_buf[0]=255; /* to force error if no data was found */
543 png_read_IDAT_data(png_ptr, png_ptr->row_buf, row_info.rowbytes + 1);
544
545 if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
546 {
547 if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
548 png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
549 png_ptr->prev_row + 1, png_ptr->row_buf[0]);
550 else
551 png_error(png_ptr, "bad adaptive filter value");
552 }
553
554 /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
555 * 1.5.6, while the buffer really is this big in current versions of libpng
556 * it may not be in the future, so this was changed just to copy the
557 * interlaced count:
558 */
559 memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);
560
561 #ifdef PNG_MNG_FEATURES_SUPPORTED
562 if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
563 (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
564 {
565 /* Intrapixel differencing */
566 png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
567 }
568 #endif
569
570 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
571 if (png_ptr->transformations)
572 png_do_read_transformations(png_ptr, &row_info);
573 #endif
574
575 /* The transformed pixel depth should match the depth now in row_info. */
576 if (png_ptr->transformed_pixel_depth == 0)
577 {
578 png_ptr->transformed_pixel_depth = row_info.pixel_depth;
579 if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
580 png_error(png_ptr, "sequential row overflow");
581 }
582
583 else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
584 png_error(png_ptr, "internal sequential row size calculation error");
585
586 #ifdef PNG_READ_INTERLACING_SUPPORTED
587 /* Expand interlaced rows to full size */
588 if (png_ptr->interlaced != 0 &&
589 (png_ptr->transformations & PNG_INTERLACE) != 0)
590 {
591 if (png_ptr->pass < 6)
592 png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
593 png_ptr->transformations);
594
595 if (dsp_row != NULL)
596 png_combine_row(png_ptr, dsp_row, 1/*display*/);
597
598 if (row != NULL)
599 png_combine_row(png_ptr, row, 0/*row*/);
600 }
601
602 else
603 #endif
604 {
605 if (row != NULL)
606 png_combine_row(png_ptr, row, -1/*ignored*/);
607
608 if (dsp_row != NULL)
609 png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
610 }
611 png_read_finish_row(png_ptr);
612
613 if (png_ptr->read_row_fn != NULL)
614 (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
615
616 }
617 #endif /* SEQUENTIAL_READ */
618
619 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
620 /* Read one or more rows of image data. If the image is interlaced,
621 * and png_set_interlace_handling() has been called, the rows need to
622 * contain the contents of the rows from the previous pass. If the
623 * image has alpha or transparency, and png_handle_alpha()[*] has been
624 * called, the rows contents must be initialized to the contents of the
625 * screen.
626 *
627 * "row" holds the actual image, and pixels are placed in it
628 * as they arrive. If the image is displayed after each pass, it will
629 * appear to "sparkle" in. "display_row" can be used to display a
630 * "chunky" progressive image, with finer detail added as it becomes
631 * available. If you do not want this "chunky" display, you may pass
632 * NULL for display_row. If you do not want the sparkle display, and
633 * you have not called png_handle_alpha(), you may pass NULL for rows.
634 * If you have called png_handle_alpha(), and the image has either an
635 * alpha channel or a transparency chunk, you must provide a buffer for
636 * rows. In this case, you do not have to provide a display_row buffer
637 * also, but you may. If the image is not interlaced, or if you have
638 * not called png_set_interlace_handling(), the display_row buffer will
639 * be ignored, so pass NULL to it.
640 *
641 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
642 */
643
644 void PNGAPI
645 png_read_rows(png_structrp png_ptr, png_bytepp row,
646 png_bytepp display_row, png_uint_32 num_rows)
647 {
648 png_uint_32 i;
649 png_bytepp rp;
650 png_bytepp dp;
651
652 png_debug(1, "in png_read_rows");
653
654 if (png_ptr == NULL)
655 return;
656
657 rp = row;
658 dp = display_row;
659 if (rp != NULL && dp != NULL)
660 for (i = 0; i < num_rows; i++)
661 {
662 png_bytep rptr = *rp++;
663 png_bytep dptr = *dp++;
664
665 png_read_row(png_ptr, rptr, dptr);
666 }
667
668 else if (rp != NULL)
669 for (i = 0; i < num_rows; i++)
670 {
671 png_bytep rptr = *rp;
672 png_read_row(png_ptr, rptr, NULL);
673 rp++;
674 }
675
676 else if (dp != NULL)
677 for (i = 0; i < num_rows; i++)
678 {
679 png_bytep dptr = *dp;
680 png_read_row(png_ptr, NULL, dptr);
681 dp++;
682 }
683 }
684 #endif /* SEQUENTIAL_READ */
685
686 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
687 /* Read the entire image. If the image has an alpha channel or a tRNS
688 * chunk, and you have called png_handle_alpha()[*], you will need to
689 * initialize the image to the current image that PNG will be overlaying.
690 * We set the num_rows again here, in case it was incorrectly set in
691 * png_read_start_row() by a call to png_read_update_info() or
692 * png_start_read_image() if png_set_interlace_handling() wasn't called
693 * prior to either of these functions like it should have been. You can
694 * only call this function once. If you desire to have an image for
695 * each pass of a interlaced image, use png_read_rows() instead.
696 *
697 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
698 */
699 void PNGAPI
700 png_read_image(png_structrp png_ptr, png_bytepp image)
701 {
702 png_uint_32 i, image_height;
703 int pass, j;
704 png_bytepp rp;
705
706 png_debug(1, "in png_read_image");
707
708 if (png_ptr == NULL)
709 return;
710
711 #ifdef PNG_READ_INTERLACING_SUPPORTED
712 if ((png_ptr->flags & PNG_FLAG_ROW_INIT) == 0)
713 {
714 pass = png_set_interlace_handling(png_ptr);
715 /* And make sure transforms are initialized. */
716 png_start_read_image(png_ptr);
717 }
718 else
719 {
720 if (png_ptr->interlaced != 0 &&
721 (png_ptr->transformations & PNG_INTERLACE) == 0)
722 {
723 /* Caller called png_start_read_image or png_read_update_info without
724 * first turning on the PNG_INTERLACE transform. We can fix this here,
725 * but the caller should do it!
726 */
727 png_warning(png_ptr, "Interlace handling should be turned on when "
728 "using png_read_image");
729 /* Make sure this is set correctly */
730 png_ptr->num_rows = png_ptr->height;
731 }
732
733 /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
734 * the above error case.
735 */
736 pass = png_set_interlace_handling(png_ptr);
737 }
738 #else
739 if (png_ptr->interlaced)
740 png_error(png_ptr,
741 "Cannot read interlaced image -- interlace handler disabled");
742
743 pass = 1;
744 #endif
745
746 image_height=png_ptr->height;
747
748 for (j = 0; j < pass; j++)
749 {
750 rp = image;
751 for (i = 0; i < image_height; i++)
752 {
753 png_read_row(png_ptr, *rp, NULL);
754 rp++;
755 }
756 }
757 }
758 #endif /* SEQUENTIAL_READ */
759
760 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
761 /* Read the end of the PNG file. Will not read past the end of the
762 * file, will verify the end is accurate, and will read any comments
763 * or time information at the end of the file, if info is not NULL.
764 */
765 void PNGAPI
766 png_read_end(png_structrp png_ptr, png_inforp info_ptr)
767 {
768 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
769 int keep;
770 #endif
771
772 png_debug(1, "in png_read_end");
773
774 if (png_ptr == NULL)
775 return;
776
777 /* If png_read_end is called in the middle of reading the rows there may
778 * still be pending IDAT data and an owned zstream. Deal with this here.
779 */
780 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
781 if (png_chunk_unknown_handling(png_ptr, png_IDAT) == 0)
782 #endif
783 png_read_finish_IDAT(png_ptr);
784
785 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
786 /* Report invalid palette index; added at libng-1.5.10 */
787 if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
788 png_ptr->num_palette_max > png_ptr->num_palette)
789 png_benign_error(png_ptr, "Read palette index exceeding num_palette");
790 #endif
791
792 do
793 {
794 png_uint_32 length = png_read_chunk_header(png_ptr);
795 png_uint_32 chunk_name = png_ptr->chunk_name;
796
797 if (chunk_name != png_IDAT)
798 png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;
799
800 if (chunk_name == png_IEND)
801 png_handle_IEND(png_ptr, info_ptr, length);
802
803 else if (chunk_name == png_IHDR)
804 png_handle_IHDR(png_ptr, info_ptr, length);
805
806 else if (info_ptr == NULL)
807 png_crc_finish(png_ptr, length);
808
809 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
810 else if ((keep = png_chunk_unknown_handling(png_ptr, chunk_name)) != 0)
811 {
812 if (chunk_name == png_IDAT)
813 {
814 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
815 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
816 png_benign_error(png_ptr, ".Too many IDATs found");
817 }
818 png_handle_unknown(png_ptr, info_ptr, length, keep);
819 if (chunk_name == png_PLTE)
820 png_ptr->mode |= PNG_HAVE_PLTE;
821 }
822 #endif
823
824 else if (chunk_name == png_IDAT)
825 {
826 /* Zero length IDATs are legal after the last IDAT has been
827 * read, but not after other chunks have been read. 1.6 does not
828 * always read all the deflate data; specifically it cannot be relied
829 * upon to read the Adler32 at the end. If it doesn't ignore IDAT
830 * chunks which are longer than zero as well:
831 */
832 if ((length > 0 && !(png_ptr->flags & PNG_FLAG_ZSTREAM_ENDED))
833 || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT) != 0)
834 png_benign_error(png_ptr, "..Too many IDATs found");
835
836 png_crc_finish(png_ptr, length);
837 }
838 else if (chunk_name == png_PLTE)
839 png_handle_PLTE(png_ptr, info_ptr, length);
840
841 #ifdef PNG_READ_bKGD_SUPPORTED
842 else if (chunk_name == png_bKGD)
843 png_handle_bKGD(png_ptr, info_ptr, length);
844 #endif
845
846 #ifdef PNG_READ_cHRM_SUPPORTED
847 else if (chunk_name == png_cHRM)
848 png_handle_cHRM(png_ptr, info_ptr, length);
849 #endif
850
851 #ifdef PNG_READ_eXIf_SUPPORTED
852 else if (chunk_name == png_eXIf)
853 png_handle_eXIf(png_ptr, info_ptr, length);
854 #endif
855
856 #ifdef PNG_READ_gAMA_SUPPORTED
857 else if (chunk_name == png_gAMA)
858 png_handle_gAMA(png_ptr, info_ptr, length);
859 #endif
860
861 #ifdef PNG_READ_hIST_SUPPORTED
862 else if (chunk_name == png_hIST)
863 png_handle_hIST(png_ptr, info_ptr, length);
864 #endif
865
866 #ifdef PNG_READ_oFFs_SUPPORTED
867 else if (chunk_name == png_oFFs)
868 png_handle_oFFs(png_ptr, info_ptr, length);
869 #endif
870
871 #ifdef PNG_READ_pCAL_SUPPORTED
872 else if (chunk_name == png_pCAL)
873 png_handle_pCAL(png_ptr, info_ptr, length);
874 #endif
875
876 #ifdef PNG_READ_sCAL_SUPPORTED
877 else if (chunk_name == png_sCAL)
878 png_handle_sCAL(png_ptr, info_ptr, length);
879 #endif
880
881 #ifdef PNG_READ_pHYs_SUPPORTED
882 else if (chunk_name == png_pHYs)
883 png_handle_pHYs(png_ptr, info_ptr, length);
884 #endif
885
886 #ifdef PNG_READ_sBIT_SUPPORTED
887 else if (chunk_name == png_sBIT)
888 png_handle_sBIT(png_ptr, info_ptr, length);
889 #endif
890
891 #ifdef PNG_READ_sRGB_SUPPORTED
892 else if (chunk_name == png_sRGB)
893 png_handle_sRGB(png_ptr, info_ptr, length);
894 #endif
895
896 #ifdef PNG_READ_iCCP_SUPPORTED
897 else if (chunk_name == png_iCCP)
898 png_handle_iCCP(png_ptr, info_ptr, length);
899 #endif
900
901 #ifdef PNG_READ_sPLT_SUPPORTED
902 else if (chunk_name == png_sPLT)
903 png_handle_sPLT(png_ptr, info_ptr, length);
904 #endif
905
906 #ifdef PNG_READ_tEXt_SUPPORTED
907 else if (chunk_name == png_tEXt)
908 png_handle_tEXt(png_ptr, info_ptr, length);
909 #endif
910
911 #ifdef PNG_READ_tIME_SUPPORTED
912 else if (chunk_name == png_tIME)
913 png_handle_tIME(png_ptr, info_ptr, length);
914 #endif
915
916 #ifdef PNG_READ_tRNS_SUPPORTED
917 else if (chunk_name == png_tRNS)
918 png_handle_tRNS(png_ptr, info_ptr, length);
919 #endif
920
921 #ifdef PNG_READ_zTXt_SUPPORTED
922 else if (chunk_name == png_zTXt)
923 png_handle_zTXt(png_ptr, info_ptr, length);
924 #endif
925
926 #ifdef PNG_READ_iTXt_SUPPORTED
927 else if (chunk_name == png_iTXt)
928 png_handle_iTXt(png_ptr, info_ptr, length);
929 #endif
930
931 else
932 png_handle_unknown(png_ptr, info_ptr, length,
933 PNG_HANDLE_CHUNK_AS_DEFAULT);
934 } while ((png_ptr->mode & PNG_HAVE_IEND) == 0);
935 }
936 #endif /* SEQUENTIAL_READ */
937
938 /* Free all memory used in the read struct */
939 static void
940 png_read_destroy(png_structrp png_ptr)
941 {
942 png_debug(1, "in png_read_destroy");
943
944 #ifdef PNG_READ_GAMMA_SUPPORTED
945 png_destroy_gamma_table(png_ptr);
946 #endif
947
948 png_free(png_ptr, png_ptr->big_row_buf);
949 png_ptr->big_row_buf = NULL;
950 png_free(png_ptr, png_ptr->big_prev_row);
951 png_ptr->big_prev_row = NULL;
952 png_free(png_ptr, png_ptr->read_buffer);
953 png_ptr->read_buffer = NULL;
954
955 #ifdef PNG_READ_QUANTIZE_SUPPORTED
956 png_free(png_ptr, png_ptr->palette_lookup);
957 png_ptr->palette_lookup = NULL;
958 png_free(png_ptr, png_ptr->quantize_index);
959 png_ptr->quantize_index = NULL;
960 #endif
961
962 if ((png_ptr->free_me & PNG_FREE_PLTE) != 0)
963 {
964 png_zfree(png_ptr, png_ptr->palette);
965 png_ptr->palette = NULL;
966 }
967 png_ptr->free_me &= ~PNG_FREE_PLTE;
968
969 #if defined(PNG_tRNS_SUPPORTED) || \
970 defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
971 if ((png_ptr->free_me & PNG_FREE_TRNS) != 0)
972 {
973 png_free(png_ptr, png_ptr->trans_alpha);
974 png_ptr->trans_alpha = NULL;
975 }
976 png_ptr->free_me &= ~PNG_FREE_TRNS;
977 #endif
978
979 inflateEnd(&png_ptr->zstream);
980
981 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
982 png_free(png_ptr, png_ptr->save_buffer);
983 png_ptr->save_buffer = NULL;
984 #endif
985
986 #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) && \
987 defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED)
988 png_free(png_ptr, png_ptr->unknown_chunk.data);
989 png_ptr->unknown_chunk.data = NULL;
990 #endif
991
992 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
993 png_free(png_ptr, png_ptr->chunk_list);
994 png_ptr->chunk_list = NULL;
995 #endif
996
997 /* NOTE: the 'setjmp' buffer may still be allocated and the memory and error
998 * callbacks are still set at this point. They are required to complete the
999 * destruction of the png_struct itself.
1000 */
1001 }
1002
1003 /* Free all memory used by the read */
1004 void PNGAPI
1005 png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
1006 png_infopp end_info_ptr_ptr)
1007 {
1008 png_structrp png_ptr = NULL;
1009
1010 png_debug(1, "in png_destroy_read_struct");
1011
1012 if (png_ptr_ptr != NULL)
1013 png_ptr = *png_ptr_ptr;
1014
1015 if (png_ptr == NULL)
1016 return;
1017
1018 /* libpng 1.6.0: use the API to destroy info structs to ensure consistent
1019 * behavior. Prior to 1.6.0 libpng did extra 'info' destruction in this API.
1020 * The extra was, apparently, unnecessary yet this hides memory leak bugs.
1021 */
1022 png_destroy_info_struct(png_ptr, end_info_ptr_ptr);
1023 png_destroy_info_struct(png_ptr, info_ptr_ptr);
1024
1025 *png_ptr_ptr = NULL;
1026 png_read_destroy(png_ptr);
1027 png_destroy_png_struct(png_ptr);
1028 }
1029
1030 void PNGAPI
1031 png_set_read_status_fn(png_structrp png_ptr, png_read_status_ptr read_row_fn)
1032 {
1033 if (png_ptr == NULL)
1034 return;
1035
1036 png_ptr->read_row_fn = read_row_fn;
1037 }
1038
1039
1040 #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
1041 #ifdef PNG_INFO_IMAGE_SUPPORTED
1042 void PNGAPI
1043 png_read_png(png_structrp png_ptr, png_inforp info_ptr,
1044 int transforms, voidp params)
1045 {
1046 if (png_ptr == NULL || info_ptr == NULL)
1047 return;
1048
1049 /* png_read_info() gives us all of the information from the
1050 * PNG file before the first IDAT (image data chunk).
1051 */
1052 png_read_info(png_ptr, info_ptr);
1053 if (info_ptr->height > PNG_UINT_32_MAX/(sizeof (png_bytep)))
1054 png_error(png_ptr, "Image is too high to process with png_read_png()");
1055
1056 /* -------------- image transformations start here ------------------- */
1057 /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
1058 * is not implemented. This will only happen in de-configured (non-default)
1059 * libpng builds. The results can be unexpected - png_read_png may return
1060 * short or mal-formed rows because the transform is skipped.
1061 */
1062
1063 /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
1064 */
1065 if ((transforms & PNG_TRANSFORM_SCALE_16) != 0)
1066 /* Added at libpng-1.5.4. "strip_16" produces the same result that it
1067 * did in earlier versions, while "scale_16" is now more accurate.
1068 */
1069 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1070 png_set_scale_16(png_ptr);
1071 #else
1072 png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
1073 #endif
1074
1075 /* If both SCALE and STRIP are required pngrtran will effectively cancel the
1076 * latter by doing SCALE first. This is ok and allows apps not to check for
1077 * which is supported to get the right answer.
1078 */
1079 if ((transforms & PNG_TRANSFORM_STRIP_16) != 0)
1080 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1081 png_set_strip_16(png_ptr);
1082 #else
1083 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
1084 #endif
1085
1086 /* Strip alpha bytes from the input data without combining with
1087 * the background (not recommended).
1088 */
1089 if ((transforms & PNG_TRANSFORM_STRIP_ALPHA) != 0)
1090 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1091 png_set_strip_alpha(png_ptr);
1092 #else
1093 png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
1094 #endif
1095
1096 /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
1097 * byte into separate bytes (useful for paletted and grayscale images).
1098 */
1099 if ((transforms & PNG_TRANSFORM_PACKING) != 0)
1100 #ifdef PNG_READ_PACK_SUPPORTED
1101 png_set_packing(png_ptr);
1102 #else
1103 png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
1104 #endif
1105
1106 /* Change the order of packed pixels to least significant bit first
1107 * (not useful if you are using png_set_packing).
1108 */
1109 if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
1110 #ifdef PNG_READ_PACKSWAP_SUPPORTED
1111 png_set_packswap(png_ptr);
1112 #else
1113 png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
1114 #endif
1115
1116 /* Expand paletted colors into true RGB triplets
1117 * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
1118 * Expand paletted or RGB images with transparency to full alpha
1119 * channels so the data will be available as RGBA quartets.
1120 */
1121 if ((transforms & PNG_TRANSFORM_EXPAND) != 0)
1122 #ifdef PNG_READ_EXPAND_SUPPORTED
1123 png_set_expand(png_ptr);
1124 #else
1125 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
1126 #endif
1127
1128 /* We don't handle background color or gamma transformation or quantizing.
1129 */
1130
1131 /* Invert monochrome files to have 0 as white and 1 as black
1132 */
1133 if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
1134 #ifdef PNG_READ_INVERT_SUPPORTED
1135 png_set_invert_mono(png_ptr);
1136 #else
1137 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
1138 #endif
1139
1140 /* If you want to shift the pixel values from the range [0,255] or
1141 * [0,65535] to the original [0,7] or [0,31], or whatever range the
1142 * colors were originally in:
1143 */
1144 if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
1145 #ifdef PNG_READ_SHIFT_SUPPORTED
1146 if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
1147 png_set_shift(png_ptr, &info_ptr->sig_bit);
1148 #else
1149 png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
1150 #endif
1151
1152 /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
1153 if ((transforms & PNG_TRANSFORM_BGR) != 0)
1154 #ifdef PNG_READ_BGR_SUPPORTED
1155 png_set_bgr(png_ptr);
1156 #else
1157 png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
1158 #endif
1159
1160 /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
1161 if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
1162 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
1163 png_set_swap_alpha(png_ptr);
1164 #else
1165 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
1166 #endif
1167
1168 /* Swap bytes of 16-bit files to least significant byte first */
1169 if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
1170 #ifdef PNG_READ_SWAP_SUPPORTED
1171 png_set_swap(png_ptr);
1172 #else
1173 png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
1174 #endif
1175
1176 /* Added at libpng-1.2.41 */
1177 /* Invert the alpha channel from opacity to transparency */
1178 if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
1179 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1180 png_set_invert_alpha(png_ptr);
1181 #else
1182 png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
1183 #endif
1184
1185 /* Added at libpng-1.2.41 */
1186 /* Expand grayscale image to RGB */
1187 if ((transforms & PNG_TRANSFORM_GRAY_TO_RGB) != 0)
1188 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1189 png_set_gray_to_rgb(png_ptr);
1190 #else
1191 png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
1192 #endif
1193
1194 /* Added at libpng-1.5.4 */
1195 if ((transforms & PNG_TRANSFORM_EXPAND_16) != 0)
1196 #ifdef PNG_READ_EXPAND_16_SUPPORTED
1197 png_set_expand_16(png_ptr);
1198 #else
1199 png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
1200 #endif
1201
1202 /* We don't handle adding filler bytes */
1203
1204 /* We use png_read_image and rely on that for interlace handling, but we also
1205 * call png_read_update_info therefore must turn on interlace handling now:
1206 */
1207 (void)png_set_interlace_handling(png_ptr);
1208
1209 /* Optional call to gamma correct and add the background to the palette
1210 * and update info structure. REQUIRED if you are expecting libpng to
1211 * update the palette for you (i.e., you selected such a transform above).
1212 */
1213 png_read_update_info(png_ptr, info_ptr);
1214
1215 /* -------------- image transformations end here ------------------- */
1216
1217 png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
1218 if (info_ptr->row_pointers == NULL)
1219 {
1220 png_uint_32 iptr;
1221
1222 info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
1223 info_ptr->height * (sizeof (png_bytep))));
1224
1225 for (iptr=0; iptr<info_ptr->height; iptr++)
1226 info_ptr->row_pointers[iptr] = NULL;
1227
1228 info_ptr->free_me |= PNG_FREE_ROWS;
1229
1230 for (iptr = 0; iptr < info_ptr->height; iptr++)
1231 info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
1232 png_malloc(png_ptr, info_ptr->rowbytes));
1233 }
1234
1235 png_read_image(png_ptr, info_ptr->row_pointers);
1236 info_ptr->valid |= PNG_INFO_IDAT;
1237
1238 /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
1239 png_read_end(png_ptr, info_ptr);
1240
1241 PNG_UNUSED(params)
1242 }
1243 #endif /* INFO_IMAGE */
1244 #endif /* SEQUENTIAL_READ */
1245
1246 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
1247 /* SIMPLIFIED READ
1248 *
1249 * This code currently relies on the sequential reader, though it could easily
1250 * be made to work with the progressive one.
1251 */
1252 /* Arguments to png_image_finish_read: */
1253
1254 /* Encoding of PNG data (used by the color-map code) */
1255 # define P_NOTSET 0 /* File encoding not yet known */
1256 # define P_sRGB 1 /* 8-bit encoded to sRGB gamma */
1257 # define P_LINEAR 2 /* 16-bit linear: not encoded, NOT pre-multiplied! */
1258 # define P_FILE 3 /* 8-bit encoded to file gamma, not sRGB or linear */
1259 # define P_LINEAR8 4 /* 8-bit linear: only from a file value */
1260
1261 /* Color-map processing: after libpng has run on the PNG image further
1262 * processing may be needed to convert the data to color-map indices.
1263 */
1264 #define PNG_CMAP_NONE 0
1265 #define PNG_CMAP_GA 1 /* Process GA data to a color-map with alpha */
1266 #define PNG_CMAP_TRANS 2 /* Process GA data to a background index */
1267 #define PNG_CMAP_RGB 3 /* Process RGB data */
1268 #define PNG_CMAP_RGB_ALPHA 4 /* Process RGBA data */
1269
1270 /* The following document where the background is for each processing case. */
1271 #define PNG_CMAP_NONE_BACKGROUND 256
1272 #define PNG_CMAP_GA_BACKGROUND 231
1273 #define PNG_CMAP_TRANS_BACKGROUND 254
1274 #define PNG_CMAP_RGB_BACKGROUND 256
1275 #define PNG_CMAP_RGB_ALPHA_BACKGROUND 216
1276
1277 typedef struct
1278 {
1279 /* Arguments: */
1280 png_imagep image;
1281 png_voidp buffer;
1282 png_int_32 row_stride;
1283 png_voidp colormap;
1284 png_const_colorp background;
1285 /* Local variables: */
1286 png_voidp local_row;
1287 png_voidp first_row;
1288 ptrdiff_t row_bytes; /* step between rows */
1289 int file_encoding; /* E_ values above */
1290 png_fixed_point gamma_to_linear; /* For P_FILE, reciprocal of gamma */
1291 int colormap_processing; /* PNG_CMAP_ values above */
1292 } png_image_read_control;
1293
1294 /* Do all the *safe* initialization - 'safe' means that png_error won't be
1295 * called, so setting up the jmp_buf is not required. This means that anything
1296 * called from here must *not* call png_malloc - it has to call png_malloc_warn
1297 * instead so that control is returned safely back to this routine.
1298 */
1299 static int
1300 png_image_read_init(png_imagep image)
1301 {
1302 if (image->opaque == NULL)
1303 {
1304 png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, image,
1305 png_safe_error, png_safe_warning);
1306
1307 /* And set the rest of the structure to NULL to ensure that the various
1308 * fields are consistent.
1309 */
1310 memset(image, 0, (sizeof *image));
1311 image->version = PNG_IMAGE_VERSION;
1312
1313 if (png_ptr != NULL)
1314 {
1315 png_infop info_ptr = png_create_info_struct(png_ptr);
1316
1317 if (info_ptr != NULL)
1318 {
1319 png_controlp control = png_voidcast(png_controlp,
1320 png_malloc_warn(png_ptr, (sizeof *control)));
1321
1322 if (control != NULL)
1323 {
1324 memset(control, 0, (sizeof *control));
1325
1326 control->png_ptr = png_ptr;
1327 control->info_ptr = info_ptr;
1328 control->for_write = 0;
1329
1330 image->opaque = control;
1331 return 1;
1332 }
1333
1334 /* Error clean up */
1335 png_destroy_info_struct(png_ptr, &info_ptr);
1336 }
1337
1338 png_destroy_read_struct(&png_ptr, NULL, NULL);
1339 }
1340
1341 return png_image_error(image, "png_image_read: out of memory");
1342 }
1343
1344 return png_image_error(image, "png_image_read: opaque pointer not NULL");
1345 }
1346
1347 /* Utility to find the base format of a PNG file from a png_struct. */
1348 static png_uint_32
1349 png_image_format(png_structrp png_ptr)
1350 {
1351 png_uint_32 format = 0;
1352
1353 if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0)
1354 format |= PNG_FORMAT_FLAG_COLOR;
1355
1356 if ((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0)
1357 format |= PNG_FORMAT_FLAG_ALPHA;
1358
1359 /* Use png_ptr here, not info_ptr, because by examination png_handle_tRNS
1360 * sets the png_struct fields; that's all we are interested in here. The
1361 * precise interaction with an app call to png_set_tRNS and PNG file reading
1362 * is unclear.
1363 */
1364 else if (png_ptr->num_trans > 0)
1365 format |= PNG_FORMAT_FLAG_ALPHA;
1366
1367 if (png_ptr->bit_depth == 16)
1368 format |= PNG_FORMAT_FLAG_LINEAR;
1369
1370 if ((png_ptr->color_type & PNG_COLOR_MASK_PALETTE) != 0)
1371 format |= PNG_FORMAT_FLAG_COLORMAP;
1372
1373 return format;
1374 }
1375
1376 /* Is the given gamma significantly different from sRGB? The test is the same
1377 * one used in pngrtran.c when deciding whether to do gamma correction. The
1378 * arithmetic optimizes the division by using the fact that the inverse of the
1379 * file sRGB gamma is 2.2
1380 */
1381 static int
1382 png_gamma_not_sRGB(png_fixed_point g)
1383 {
1384 if (g < PNG_FP_1)
1385 {
1386 /* An uninitialized gamma is assumed to be sRGB for the simplified API. */
1387 if (g == 0)
1388 return 0;
1389
1390 return png_gamma_significant((g * 11 + 2)/5 /* i.e. *2.2, rounded */);
1391 }
1392
1393 return 1;
1394 }
1395
1396 /* Do the main body of a 'png_image_begin_read' function; read the PNG file
1397 * header and fill in all the information. This is executed in a safe context,
1398 * unlike the init routine above.
1399 */
1400 static int
1401 png_image_read_header(png_voidp argument)
1402 {
1403 png_imagep image = png_voidcast(png_imagep, argument);
1404 png_structrp png_ptr = image->opaque->png_ptr;
1405 png_inforp info_ptr = image->opaque->info_ptr;
1406
1407 #ifdef PNG_BENIGN_ERRORS_SUPPORTED
1408 png_set_benign_errors(png_ptr, 1/*warn*/);
1409 #endif
1410 png_read_info(png_ptr, info_ptr);
1411
1412 /* Do this the fast way; just read directly out of png_struct. */
1413 image->width = png_ptr->width;
1414 image->height = png_ptr->height;
1415
1416 {
1417 png_uint_32 format = png_image_format(png_ptr);
1418
1419 image->format = format;
1420
1421 #ifdef PNG_COLORSPACE_SUPPORTED
1422 /* Does the colorspace match sRGB? If there is no color endpoint
1423 * (colorant) information assume yes, otherwise require the
1424 * 'ENDPOINTS_MATCHP_sRGB' colorspace flag to have been set. If the
1425 * colorspace has been determined to be invalid ignore it.
1426 */
1427 if ((format & PNG_FORMAT_FLAG_COLOR) != 0 && ((png_ptr->colorspace.flags
1428 & (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB|
1429 PNG_COLORSPACE_INVALID)) == PNG_COLORSPACE_HAVE_ENDPOINTS))
1430 image->flags |= PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB;
1431 #endif
1432 }
1433
1434 /* We need the maximum number of entries regardless of the format the
1435 * application sets here.
1436 */
1437 {
1438 png_uint_32 cmap_entries;
1439
1440 switch (png_ptr->color_type)
1441 {
1442 case PNG_COLOR_TYPE_GRAY:
1443 cmap_entries = 1U << png_ptr->bit_depth;
1444 break;
1445
1446 case PNG_COLOR_TYPE_PALETTE:
1447 cmap_entries = (png_uint_32)png_ptr->num_palette;
1448 break;
1449
1450 default:
1451 cmap_entries = 256;
1452 break;
1453 }
1454
1455 if (cmap_entries > 256)
1456 cmap_entries = 256;
1457
1458 image->colormap_entries = cmap_entries;
1459 }
1460
1461 return 1;
1462 }
1463
1464 #ifdef PNG_STDIO_SUPPORTED
1465 int PNGAPI
1466 png_image_begin_read_from_stdio(png_imagep image, FILE* file)
1467 {
1468 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1469 {
1470 if (file != NULL)
1471 {
1472 if (png_image_read_init(image) != 0)
1473 {
1474 /* This is slightly evil, but png_init_io doesn't do anything other
1475 * than this and we haven't changed the standard IO functions so
1476 * this saves a 'safe' function.
1477 */
1478 image->opaque->png_ptr->io_ptr = file;
1479 return png_safe_execute(image, png_image_read_header, image);
1480 }
1481 }
1482
1483 else
1484 return png_image_error(image,
1485 "png_image_begin_read_from_stdio: invalid argument");
1486 }
1487
1488 else if (image != NULL)
1489 return png_image_error(image,
1490 "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
1491
1492 return 0;
1493 }
1494
1495 int PNGAPI
1496 png_image_begin_read_from_file(png_imagep image, const char *file_name)
1497 {
1498 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1499 {
1500 if (file_name != NULL)
1501 {
1502 FILE *fp = fopen(file_name, "rb");
1503
1504 if (fp != NULL)
1505 {
1506 if (png_image_read_init(image) != 0)
1507 {
1508 image->opaque->png_ptr->io_ptr = fp;
1509 image->opaque->owned_file = 1;
1510 return png_safe_execute(image, png_image_read_header, image);
1511 }
1512
1513 /* Clean up: just the opened file. */
1514 (void)fclose(fp);
1515 }
1516
1517 else
1518 return png_image_error(image, strerror(errno));
1519 }
1520
1521 else
1522 return png_image_error(image,
1523 "png_image_begin_read_from_file: invalid argument");
1524 }
1525
1526 else if (image != NULL)
1527 return png_image_error(image,
1528 "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
1529
1530 return 0;
1531 }
1532 #endif /* STDIO */
1533
1534 static void PNGCBAPI
1535 png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
1536 {
1537 if (png_ptr != NULL)
1538 {
1539 png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
1540 if (image != NULL)
1541 {
1542 png_controlp cp = image->opaque;
1543 if (cp != NULL)
1544 {
1545 png_const_bytep memory = cp->memory;
1546 png_size_t size = cp->size;
1547
1548 if (memory != NULL && size >= need)
1549 {
1550 memcpy(out, memory, need);
1551 cp->memory = memory + need;
1552 cp->size = size - need;
1553 return;
1554 }
1555
1556 png_error(png_ptr, "read beyond end of data");
1557 }
1558 }
1559
1560 png_error(png_ptr, "invalid memory read");
1561 }
1562 }
1563
1564 int PNGAPI png_image_begin_read_from_memory(png_imagep image,
1565 png_const_voidp memory, png_size_t size)
1566 {
1567 if (image != NULL && image->version == PNG_IMAGE_VERSION)
1568 {
1569 if (memory != NULL && size > 0)
1570 {
1571 if (png_image_read_init(image) != 0)
1572 {
1573 /* Now set the IO functions to read from the memory buffer and
1574 * store it into io_ptr. Again do this in-place to avoid calling a
1575 * libpng function that requires error handling.
1576 */
1577 image->opaque->memory = png_voidcast(png_const_bytep, memory);
1578 image->opaque->size = size;
1579 image->opaque->png_ptr->io_ptr = image;
1580 image->opaque->png_ptr->read_data_fn = png_image_memory_read;
1581
1582 return png_safe_execute(image, png_image_read_header, image);
1583 }
1584 }
1585
1586 else
1587 return png_image_error(image,
1588 "png_image_begin_read_from_memory: invalid argument");
1589 }
1590
1591 else if (image != NULL)
1592 return png_image_error(image,
1593 "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
1594
1595 return 0;
1596 }
1597
1598 /* Utility function to skip chunks that are not used by the simplified image
1599 * read functions and an appropriate macro to call it.
1600 */
1601 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
1602 static void
1603 png_image_skip_unused_chunks(png_structrp png_ptr)
1604 {
1605 /* Prepare the reader to ignore all recognized chunks whose data will not
1606 * be used, i.e., all chunks recognized by libpng except for those
1607 * involved in basic image reading:
1608 *
1609 * IHDR, PLTE, IDAT, IEND
1610 *
1611 * Or image data handling:
1612 *
1613 * tRNS, bKGD, gAMA, cHRM, sRGB, [iCCP] and sBIT.
1614 *
1615 * This provides a small performance improvement and eliminates any
1616 * potential vulnerability to security problems in the unused chunks.
1617 *
1618 * At present the iCCP chunk data isn't used, so iCCP chunk can be ignored
1619 * too. This allows the simplified API to be compiled without iCCP support,
1620 * however if the support is there the chunk is still checked to detect
1621 * errors (which are unfortunately quite common.)
1622 */
1623 {
1624 static PNG_CONST png_byte chunks_to_process[] = {
1625 98, 75, 71, 68, '\0', /* bKGD */
1626 99, 72, 82, 77, '\0', /* cHRM */
1627 103, 65, 77, 65, '\0', /* gAMA */
1628 # ifdef PNG_READ_iCCP_SUPPORTED
1629 105, 67, 67, 80, '\0', /* iCCP */
1630 # endif
1631 115, 66, 73, 84, '\0', /* sBIT */
1632 115, 82, 71, 66, '\0', /* sRGB */
1633 };
1634
1635 /* Ignore unknown chunks and all other chunks except for the
1636 * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
1637 */
1638 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
1639 NULL, -1);
1640
1641 /* But do not ignore image data handling chunks */
1642 png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
1643 chunks_to_process, (int)/*SAFE*/(sizeof chunks_to_process)/5);
1644 }
1645 }
1646
1647 # define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
1648 #else
1649 # define PNG_SKIP_CHUNKS(p) ((void)0)
1650 #endif /* HANDLE_AS_UNKNOWN */
1651
1652 /* The following macro gives the exact rounded answer for all values in the
1653 * range 0..255 (it actually divides by 51.2, but the rounding still generates
1654 * the correct numbers 0..5
1655 */
1656 #define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
1657
1658 /* Utility functions to make particular color-maps */
1659 static void
1660 set_file_encoding(png_image_read_control *display)
1661 {
1662 png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
1663 if (png_gamma_significant(g) != 0)
1664 {
1665 if (png_gamma_not_sRGB(g) != 0)
1666 {
1667 display->file_encoding = P_FILE;
1668 display->gamma_to_linear = png_reciprocal(g);
1669 }
1670
1671 else
1672 display->file_encoding = P_sRGB;
1673 }
1674
1675 else
1676 display->file_encoding = P_LINEAR8;
1677 }
1678
1679 static unsigned int
1680 decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
1681 {
1682 if (encoding == P_FILE) /* double check */
1683 encoding = display->file_encoding;
1684
1685 if (encoding == P_NOTSET) /* must be the file encoding */
1686 {
1687 set_file_encoding(display);
1688 encoding = display->file_encoding;
1689 }
1690
1691 switch (encoding)
1692 {
1693 case P_FILE:
1694 value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
1695 break;
1696
1697 case P_sRGB:
1698 value = png_sRGB_table[value];
1699 break;
1700
1701 case P_LINEAR:
1702 break;
1703
1704 case P_LINEAR8:
1705 value *= 257;
1706 break;
1707
1708 #ifdef __GNUC__
1709 default:
1710 png_error(display->image->opaque->png_ptr,
1711 "unexpected encoding (internal error)");
1712 #endif
1713 }
1714
1715 return value;
1716 }
1717
1718 static png_uint_32
1719 png_colormap_compose(png_image_read_control *display,
1720 png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
1721 png_uint_32 background, int encoding)
1722 {
1723 /* The file value is composed on the background, the background has the given
1724 * encoding and so does the result, the file is encoded with P_FILE and the
1725 * file and alpha are 8-bit values. The (output) encoding will always be
1726 * P_LINEAR or P_sRGB.
1727 */
1728 png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
1729 png_uint_32 b = decode_gamma(display, background, encoding);
1730
1731 /* The alpha is always an 8-bit value (it comes from the palette), the value
1732 * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
1733 */
1734 f = f * alpha + b * (255-alpha);
1735
1736 if (encoding == P_LINEAR)
1737 {
1738 /* Scale to 65535; divide by 255, approximately (in fact this is extremely
1739 * accurate, it divides by 255.00000005937181414556, with no overflow.)
1740 */
1741 f *= 257; /* Now scaled by 65535 */
1742 f += f >> 16;
1743 f = (f+32768) >> 16;
1744 }
1745
1746 else /* P_sRGB */
1747 f = PNG_sRGB_FROM_LINEAR(f);
1748
1749 return f;
1750 }
1751
1752 /* NOTE: P_LINEAR values to this routine must be 16-bit, but P_FILE values must
1753 * be 8-bit.
1754 */
1755 static void
1756 png_create_colormap_entry(png_image_read_control *display,
1757 png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
1758 png_uint_32 alpha, int encoding)
1759 {
1760 png_imagep image = display->image;
1761 const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
1762 P_LINEAR : P_sRGB;
1763 const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
1764 (red != green || green != blue);
1765
1766 if (ip > 255)
1767 png_error(image->opaque->png_ptr, "color-map index out of range");
1768
1769 /* Update the cache with whether the file gamma is significantly different
1770 * from sRGB.
1771 */
1772 if (encoding == P_FILE)
1773 {
1774 if (display->file_encoding == P_NOTSET)
1775 set_file_encoding(display);
1776
1777 /* Note that the cached value may be P_FILE too, but if it is then the
1778 * gamma_to_linear member has been set.
1779 */
1780 encoding = display->file_encoding;
1781 }
1782
1783 if (encoding == P_FILE)
1784 {
1785 png_fixed_point g = display->gamma_to_linear;
1786
1787 red = png_gamma_16bit_correct(red*257, g);
1788 green = png_gamma_16bit_correct(green*257, g);
1789 blue = png_gamma_16bit_correct(blue*257, g);
1790
1791 if (convert_to_Y != 0 || output_encoding == P_LINEAR)
1792 {
1793 alpha *= 257;
1794 encoding = P_LINEAR;
1795 }
1796
1797 else
1798 {
1799 red = PNG_sRGB_FROM_LINEAR(red * 255);
1800 green = PNG_sRGB_FROM_LINEAR(green * 255);
1801 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1802 encoding = P_sRGB;
1803 }
1804 }
1805
1806 else if (encoding == P_LINEAR8)
1807 {
1808 /* This encoding occurs quite frequently in test cases because PngSuite
1809 * includes a gAMA 1.0 chunk with most images.
1810 */
1811 red *= 257;
1812 green *= 257;
1813 blue *= 257;
1814 alpha *= 257;
1815 encoding = P_LINEAR;
1816 }
1817
1818 else if (encoding == P_sRGB &&
1819 (convert_to_Y != 0 || output_encoding == P_LINEAR))
1820 {
1821 /* The values are 8-bit sRGB values, but must be converted to 16-bit
1822 * linear.
1823 */
1824 red = png_sRGB_table[red];
1825 green = png_sRGB_table[green];
1826 blue = png_sRGB_table[blue];
1827 alpha *= 257;
1828 encoding = P_LINEAR;
1829 }
1830
1831 /* This is set if the color isn't gray but the output is. */
1832 if (encoding == P_LINEAR)
1833 {
1834 if (convert_to_Y != 0)
1835 {
1836 /* NOTE: these values are copied from png_do_rgb_to_gray */
1837 png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
1838 (png_uint_32)2366 * blue;
1839
1840 if (output_encoding == P_LINEAR)
1841 y = (y + 16384) >> 15;
1842
1843 else
1844 {
1845 /* y is scaled by 32768, we need it scaled by 255: */
1846 y = (y + 128) >> 8;
1847 y *= 255;
1848 y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
1849 alpha = PNG_DIV257(alpha);
1850 encoding = P_sRGB;
1851 }
1852
1853 blue = red = green = y;
1854 }
1855
1856 else if (output_encoding == P_sRGB)
1857 {
1858 red = PNG_sRGB_FROM_LINEAR(red * 255);
1859 green = PNG_sRGB_FROM_LINEAR(green * 255);
1860 blue = PNG_sRGB_FROM_LINEAR(blue * 255);
1861 alpha = PNG_DIV257(alpha);
1862 encoding = P_sRGB;
1863 }
1864 }
1865
1866 if (encoding != output_encoding)
1867 png_error(image->opaque->png_ptr, "bad encoding (internal error)");
1868
1869 /* Store the value. */
1870 {
1871 # ifdef PNG_FORMAT_AFIRST_SUPPORTED
1872 const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
1873 (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
1874 # else
1875 # define afirst 0
1876 # endif
1877 # ifdef PNG_FORMAT_BGR_SUPPORTED
1878 const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
1879 # else
1880 # define bgr 0
1881 # endif
1882
1883 if (output_encoding == P_LINEAR)
1884 {
1885 png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
1886
1887 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1888
1889 /* The linear 16-bit values must be pre-multiplied by the alpha channel
1890 * value, if less than 65535 (this is, effectively, composite on black
1891 * if the alpha channel is removed.)
1892 */
1893 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1894 {
1895 case 4:
1896 entry[afirst ? 0 : 3] = (png_uint_16)alpha;
1897 /* FALLTHROUGH */
1898
1899 case 3:
1900 if (alpha < 65535)
1901 {
1902 if (alpha > 0)
1903 {
1904 blue = (blue * alpha + 32767U)/65535U;
1905 green = (green * alpha + 32767U)/65535U;
1906 red = (red * alpha + 32767U)/65535U;
1907 }
1908
1909 else
1910 red = green = blue = 0;
1911 }
1912 entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
1913 entry[afirst + 1] = (png_uint_16)green;
1914 entry[afirst + bgr] = (png_uint_16)red;
1915 break;
1916
1917 case 2:
1918 entry[1 ^ afirst] = (png_uint_16)alpha;
1919 /* FALLTHROUGH */
1920
1921 case 1:
1922 if (alpha < 65535)
1923 {
1924 if (alpha > 0)
1925 green = (green * alpha + 32767U)/65535U;
1926
1927 else
1928 green = 0;
1929 }
1930 entry[afirst] = (png_uint_16)green;
1931 break;
1932
1933 default:
1934 break;
1935 }
1936 }
1937
1938 else /* output encoding is P_sRGB */
1939 {
1940 png_bytep entry = png_voidcast(png_bytep, display->colormap);
1941
1942 entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
1943
1944 switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
1945 {
1946 case 4:
1947 entry[afirst ? 0 : 3] = (png_byte)alpha;
1948 /* FALLTHROUGH */
1949 case 3:
1950 entry[afirst + (2 ^ bgr)] = (png_byte)blue;
1951 entry[afirst + 1] = (png_byte)green;
1952 entry[afirst + bgr] = (png_byte)red;
1953 break;
1954
1955 case 2:
1956 entry[1 ^ afirst] = (png_byte)alpha;
1957 /* FALLTHROUGH */
1958 case 1:
1959 entry[afirst] = (png_byte)green;
1960 break;
1961
1962 default:
1963 break;
1964 }
1965 }
1966
1967 # ifdef afirst
1968 # undef afirst
1969 # endif
1970 # ifdef bgr
1971 # undef bgr
1972 # endif
1973 }
1974 }
1975
1976 static int
1977 make_gray_file_colormap(png_image_read_control *display)
1978 {
1979 unsigned int i;
1980
1981 for (i=0; i<256; ++i)
1982 png_create_colormap_entry(display, i, i, i, i, 255, P_FILE);
1983
1984 return (int)i;
1985 }
1986
1987 static int
1988 make_gray_colormap(png_image_read_control *display)
1989 {
1990 unsigned int i;
1991
1992 for (i=0; i<256; ++i)
1993 png_create_colormap_entry(display, i, i, i, i, 255, P_sRGB);
1994
1995 return (int)i;
1996 }
1997 #define PNG_GRAY_COLORMAP_ENTRIES 256
1998
1999 static int
2000 make_ga_colormap(png_image_read_control *display)
2001 {
2002 unsigned int i, a;
2003
2004 /* Alpha is retained, the output will be a color-map with entries
2005 * selected by six levels of alpha. One transparent entry, 6 gray
2006 * levels for all the intermediate alpha values, leaving 230 entries
2007 * for the opaque grays. The color-map entries are the six values
2008 * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
2009 * relevant entry.
2010 *
2011 * if (alpha > 229) // opaque
2012 * {
2013 * // The 231 entries are selected to make the math below work:
2014 * base = 0;
2015 * entry = (231 * gray + 128) >> 8;
2016 * }
2017 * else if (alpha < 26) // transparent
2018 * {
2019 * base = 231;
2020 * entry = 0;
2021 * }
2022 * else // partially opaque
2023 * {
2024 * base = 226 + 6 * PNG_DIV51(alpha);
2025 * entry = PNG_DIV51(gray);
2026 * }
2027 */
2028 i = 0;
2029 while (i < 231)
2030 {
2031 unsigned int gray = (i * 256 + 115) / 231;
2032 png_create_colormap_entry(display, i++, gray, gray, gray, 255, P_sRGB);
2033 }
2034
2035 /* 255 is used here for the component values for consistency with the code
2036 * that undoes premultiplication in pngwrite.c.
2037 */
2038 png_create_colormap_entry(display, i++, 255, 255, 255, 0, P_sRGB);
2039
2040 for (a=1; a<5; ++a)
2041 {
2042 unsigned int g;
2043
2044 for (g=0; g<6; ++g)
2045 png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
2046 P_sRGB);
2047 }
2048
2049 return (int)i;
2050 }
2051
2052 #define PNG_GA_COLORMAP_ENTRIES 256
2053
2054 static int
2055 make_rgb_colormap(png_image_read_control *display)
2056 {
2057 unsigned int i, r;
2058
2059 /* Build a 6x6x6 opaque RGB cube */
2060 for (i=r=0; r<6; ++r)
2061 {
2062 unsigned int g;
2063
2064 for (g=0; g<6; ++g)
2065 {
2066 unsigned int b;
2067
2068 for (b=0; b<6; ++b)
2069 png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
2070 P_sRGB);
2071 }
2072 }
2073
2074 return (int)i;
2075 }
2076
2077 #define PNG_RGB_COLORMAP_ENTRIES 216
2078
2079 /* Return a palette index to the above palette given three 8-bit sRGB values. */
2080 #define PNG_RGB_INDEX(r,g,b) \
2081 ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
2082
2083 static int
2084 png_image_read_colormap(png_voidp argument)
2085 {
2086 png_image_read_control *display =
2087 png_voidcast(png_image_read_control*, argument);
2088 const png_imagep image = display->image;
2089
2090 const png_structrp png_ptr = image->opaque->png_ptr;
2091 const png_uint_32 output_format = image->format;
2092 const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
2093 P_LINEAR : P_sRGB;
2094
2095 unsigned int cmap_entries;
2096 unsigned int output_processing; /* Output processing option */
2097 unsigned int data_encoding = P_NOTSET; /* Encoding libpng must produce */
2098
2099 /* Background information; the background color and the index of this color
2100 * in the color-map if it exists (else 256).
2101 */
2102 unsigned int background_index = 256;
2103 png_uint_32 back_r, back_g, back_b;
2104
2105 /* Flags to accumulate things that need to be done to the input. */
2106 int expand_tRNS = 0;
2107
2108 /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
2109 * very difficult to do, the results look awful, and it is difficult to see
2110 * what possible use it is because the application can't control the
2111 * color-map.
2112 */
2113 if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
2114 png_ptr->num_trans > 0) /* alpha in input */ &&
2115 ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
2116 {
2117 if (output_encoding == P_LINEAR) /* compose on black */
2118 back_b = back_g = back_r = 0;
2119
2120 else if (display->background == NULL /* no way to remove it */)
2121 png_error(png_ptr,
2122 "background color must be supplied to remove alpha/transparency");
2123
2124 /* Get a copy of the background color (this avoids repeating the checks
2125 * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
2126 * output format.
2127 */
2128 else
2129 {
2130 back_g = display->background->green;
2131 if ((output_format & PNG_FORMAT_FLAG_COLOR) != 0)
2132 {
2133 back_r = display->background->red;
2134 back_b = display->background->blue;
2135 }
2136 else
2137 back_b = back_r = back_g;
2138 }
2139 }
2140
2141 else if (output_encoding == P_LINEAR)
2142 back_b = back_r = back_g = 65535;
2143
2144 else
2145 back_b = back_r = back_g = 255;
2146
2147 /* Default the input file gamma if required - this is necessary because
2148 * libpng assumes that if no gamma information is present the data is in the
2149 * output format, but the simplified API deduces the gamma from the input
2150 * format.
2151 */
2152 if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
2153 {
2154 /* Do this directly, not using the png_colorspace functions, to ensure
2155 * that it happens even if the colorspace is invalid (though probably if
2156 * it is the setting will be ignored) Note that the same thing can be
2157 * achieved at the application interface with png_set_gAMA.
2158 */
2159 if (png_ptr->bit_depth == 16 &&
2160 (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
2161 png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
2162
2163 else
2164 png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
2165
2166 png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
2167 }
2168
2169 /* Decide what to do based on the PNG color type of the input data. The
2170 * utility function png_create_colormap_entry deals with most aspects of the
2171 * output transformations; this code works out how to produce bytes of
2172 * color-map entries from the original format.
2173 */
2174 switch (png_ptr->color_type)
2175 {
2176 case PNG_COLOR_TYPE_GRAY:
2177 if (png_ptr->bit_depth <= 8)
2178 {
2179 /* There at most 256 colors in the output, regardless of
2180 * transparency.
2181 */
2182 unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
2183
2184 cmap_entries = 1U << png_ptr->bit_depth;
2185 if (cmap_entries > image->colormap_entries)
2186 png_error(png_ptr, "gray[8] color-map: too few entries");
2187
2188 step = 255 / (cmap_entries - 1);
2189 output_processing = PNG_CMAP_NONE;
2190
2191 /* If there is a tRNS chunk then this either selects a transparent
2192 * value or, if the output has no alpha, the background color.
2193 */
2194 if (png_ptr->num_trans > 0)
2195 {
2196 trans = png_ptr->trans_color.gray;
2197
2198 if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
2199 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2200 }
2201
2202 /* png_create_colormap_entry just takes an RGBA and writes the
2203 * corresponding color-map entry using the format from 'image',
2204 * including the required conversion to sRGB or linear as
2205 * appropriate. The input values are always either sRGB (if the
2206 * gamma correction flag is 0) or 0..255 scaled file encoded values
2207 * (if the function must gamma correct them).
2208 */
2209 for (i=val=0; i<cmap_entries; ++i, val += step)
2210 {
2211 /* 'i' is a file value. While this will result in duplicated
2212 * entries for 8-bit non-sRGB encoded files it is necessary to
2213 * have non-gamma corrected values to do tRNS handling.
2214 */
2215 if (i != trans)
2216 png_create_colormap_entry(display, i, val, val, val, 255,
2217 P_FILE/*8-bit with file gamma*/);
2218
2219 /* Else this entry is transparent. The colors don't matter if
2220 * there is an alpha channel (back_alpha == 0), but it does no
2221 * harm to pass them in; the values are not set above so this
2222 * passes in white.
2223 *
2224 * NOTE: this preserves the full precision of the application
2225 * supplied background color when it is used.
2226 */
2227 else
2228 png_create_colormap_entry(display, i, back_r, back_g, back_b,
2229 back_alpha, output_encoding);
2230 }
2231
2232 /* We need libpng to preserve the original encoding. */
2233 data_encoding = P_FILE;
2234
2235 /* The rows from libpng, while technically gray values, are now also
2236 * color-map indices; however, they may need to be expanded to 1
2237 * byte per pixel. This is what png_set_packing does (i.e., it
2238 * unpacks the bit values into bytes.)
2239 */
2240 if (png_ptr->bit_depth < 8)
2241 png_set_packing(png_ptr);
2242 }
2243
2244 else /* bit depth is 16 */
2245 {
2246 /* The 16-bit input values can be converted directly to 8-bit gamma
2247 * encoded values; however, if a tRNS chunk is present 257 color-map
2248 * entries are required. This means that the extra entry requires
2249 * special processing; add an alpha channel, sacrifice gray level
2250 * 254 and convert transparent (alpha==0) entries to that.
2251 *
2252 * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
2253 * same time to minimize quality loss. If a tRNS chunk is present
2254 * this means libpng must handle it too; otherwise it is impossible
2255 * to do the exact match on the 16-bit value.
2256 *
2257 * If the output has no alpha channel *and* the background color is
2258 * gray then it is possible to let libpng handle the substitution by
2259 * ensuring that the corresponding gray level matches the background
2260 * color exactly.
2261 */
2262 data_encoding = P_sRGB;
2263
2264 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2265 png_error(png_ptr, "gray[16] color-map: too few entries");
2266
2267 cmap_entries = (unsigned int)make_gray_colormap(display);
2268
2269 if (png_ptr->num_trans > 0)
2270 {
2271 unsigned int back_alpha;
2272
2273 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2274 back_alpha = 0;
2275
2276 else
2277 {
2278 if (back_r == back_g && back_g == back_b)
2279 {
2280 /* Background is gray; no special processing will be
2281 * required.
2282 */
2283 png_color_16 c;
2284 png_uint_32 gray = back_g;
2285
2286 if (output_encoding == P_LINEAR)
2287 {
2288 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2289
2290 /* And make sure the corresponding palette entry
2291 * matches.
2292 */
2293 png_create_colormap_entry(display, gray, back_g, back_g,
2294 back_g, 65535, P_LINEAR);
2295 }
2296
2297 /* The background passed to libpng, however, must be the
2298 * sRGB value.
2299 */
2300 c.index = 0; /*unused*/
2301 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2302
2303 /* NOTE: does this work without expanding tRNS to alpha?
2304 * It should be the color->gray case below apparently
2305 * doesn't.
2306 */
2307 png_set_background_fixed(png_ptr, &c,
2308 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2309 0/*gamma: not used*/);
2310
2311 output_processing = PNG_CMAP_NONE;
2312 break;
2313 }
2314 #ifdef __COVERITY__
2315 /* Coverity claims that output_encoding cannot be 2 (P_LINEAR)
2316 * here.
2317 */
2318 back_alpha = 255;
2319 #else
2320 back_alpha = output_encoding == P_LINEAR ? 65535 : 255;
2321 #endif
2322 }
2323
2324 /* output_processing means that the libpng-processed row will be
2325 * 8-bit GA and it has to be processing to single byte color-map
2326 * values. Entry 254 is replaced by either a completely
2327 * transparent entry or by the background color at full
2328 * precision (and the background color is not a simple gray
2329 * level in this case.)
2330 */
2331 expand_tRNS = 1;
2332 output_processing = PNG_CMAP_TRANS;
2333 background_index = 254;
2334
2335 /* And set (overwrite) color-map entry 254 to the actual
2336 * background color at full precision.
2337 */
2338 png_create_colormap_entry(display, 254, back_r, back_g, back_b,
2339 back_alpha, output_encoding);
2340 }
2341
2342 else
2343 output_processing = PNG_CMAP_NONE;
2344 }
2345 break;
2346
2347 case PNG_COLOR_TYPE_GRAY_ALPHA:
2348 /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
2349 * of 65536 combinations. If, however, the alpha channel is to be
2350 * removed there are only 256 possibilities if the background is gray.
2351 * (Otherwise there is a subset of the 65536 possibilities defined by
2352 * the triangle between black, white and the background color.)
2353 *
2354 * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
2355 * worry about tRNS matching - tRNS is ignored if there is an alpha
2356 * channel.
2357 */
2358 data_encoding = P_sRGB;
2359
2360 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2361 {
2362 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2363 png_error(png_ptr, "gray+alpha color-map: too few entries");
2364
2365 cmap_entries = (unsigned int)make_ga_colormap(display);
2366
2367 background_index = PNG_CMAP_GA_BACKGROUND;
2368 output_processing = PNG_CMAP_GA;
2369 }
2370
2371 else /* alpha is removed */
2372 {
2373 /* Alpha must be removed as the PNG data is processed when the
2374 * background is a color because the G and A channels are
2375 * independent and the vector addition (non-parallel vectors) is a
2376 * 2-D problem.
2377 *
2378 * This can be reduced to the same algorithm as above by making a
2379 * colormap containing gray levels (for the opaque grays), a
2380 * background entry (for a transparent pixel) and a set of four six
2381 * level color values, one set for each intermediate alpha value.
2382 * See the comments in make_ga_colormap for how this works in the
2383 * per-pixel processing.
2384 *
2385 * If the background is gray, however, we only need a 256 entry gray
2386 * level color map. It is sufficient to make the entry generated
2387 * for the background color be exactly the color specified.
2388 */
2389 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
2390 (back_r == back_g && back_g == back_b))
2391 {
2392 /* Background is gray; no special processing will be required. */
2393 png_color_16 c;
2394 png_uint_32 gray = back_g;
2395
2396 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2397 png_error(png_ptr, "gray-alpha color-map: too few entries");
2398
2399 cmap_entries = (unsigned int)make_gray_colormap(display);
2400
2401 if (output_encoding == P_LINEAR)
2402 {
2403 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2404
2405 /* And make sure the corresponding palette entry matches. */
2406 png_create_colormap_entry(display, gray, back_g, back_g,
2407 back_g, 65535, P_LINEAR);
2408 }
2409
2410 /* The background passed to libpng, however, must be the sRGB
2411 * value.
2412 */
2413 c.index = 0; /*unused*/
2414 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2415
2416 png_set_background_fixed(png_ptr, &c,
2417 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2418 0/*gamma: not used*/);
2419
2420 output_processing = PNG_CMAP_NONE;
2421 }
2422
2423 else
2424 {
2425 png_uint_32 i, a;
2426
2427 /* This is the same as png_make_ga_colormap, above, except that
2428 * the entries are all opaque.
2429 */
2430 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2431 png_error(png_ptr, "ga-alpha color-map: too few entries");
2432
2433 i = 0;
2434 while (i < 231)
2435 {
2436 png_uint_32 gray = (i * 256 + 115) / 231;
2437 png_create_colormap_entry(display, i++, gray, gray, gray,
2438 255, P_sRGB);
2439 }
2440
2441 /* NOTE: this preserves the full precision of the application
2442 * background color.
2443 */
2444 background_index = i;
2445 png_create_colormap_entry(display, i++, back_r, back_g, back_b,
2446 #ifdef __COVERITY__
2447 /* Coverity claims that output_encoding
2448 * cannot be 2 (P_LINEAR) here.
2449 */ 255U,
2450 #else
2451 output_encoding == P_LINEAR ? 65535U : 255U,
2452 #endif
2453 output_encoding);
2454
2455 /* For non-opaque input composite on the sRGB background - this
2456 * requires inverting the encoding for each component. The input
2457 * is still converted to the sRGB encoding because this is a
2458 * reasonable approximate to the logarithmic curve of human
2459 * visual sensitivity, at least over the narrow range which PNG
2460 * represents. Consequently 'G' is always sRGB encoded, while
2461 * 'A' is linear. We need the linear background colors.
2462 */
2463 if (output_encoding == P_sRGB) /* else already linear */
2464 {
2465 /* This may produce a value not exactly matching the
2466 * background, but that's ok because these numbers are only
2467 * used when alpha != 0
2468 */
2469 back_r = png_sRGB_table[back_r];
2470 back_g = png_sRGB_table[back_g];
2471 back_b = png_sRGB_table[back_b];
2472 }
2473
2474 for (a=1; a<5; ++a)
2475 {
2476 unsigned int g;
2477
2478 /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
2479 * by an 8-bit alpha value (0..255).
2480 */
2481 png_uint_32 alpha = 51 * a;
2482 png_uint_32 back_rx = (255-alpha) * back_r;
2483 png_uint_32 back_gx = (255-alpha) * back_g;
2484 png_uint_32 back_bx = (255-alpha) * back_b;
2485
2486 for (g=0; g<6; ++g)
2487 {
2488 png_uint_32 gray = png_sRGB_table[g*51] * alpha;
2489
2490 png_create_colormap_entry(display, i++,
2491 PNG_sRGB_FROM_LINEAR(gray + back_rx),
2492 PNG_sRGB_FROM_LINEAR(gray + back_gx),
2493 PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, P_sRGB);
2494 }
2495 }
2496
2497 cmap_entries = i;
2498 output_processing = PNG_CMAP_GA;
2499 }
2500 }
2501 break;
2502
2503 case PNG_COLOR_TYPE_RGB:
2504 case PNG_COLOR_TYPE_RGB_ALPHA:
2505 /* Exclude the case where the output is gray; we can always handle this
2506 * with the cases above.
2507 */
2508 if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
2509 {
2510 /* The color-map will be grayscale, so we may as well convert the
2511 * input RGB values to a simple grayscale and use the grayscale
2512 * code above.
2513 *
2514 * NOTE: calling this apparently damages the recognition of the
2515 * transparent color in background color handling; call
2516 * png_set_tRNS_to_alpha before png_set_background_fixed.
2517 */
2518 png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
2519 -1);
2520 data_encoding = P_sRGB;
2521
2522 /* The output will now be one or two 8-bit gray or gray+alpha
2523 * channels. The more complex case arises when the input has alpha.
2524 */
2525 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2526 png_ptr->num_trans > 0) &&
2527 (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2528 {
2529 /* Both input and output have an alpha channel, so no background
2530 * processing is required; just map the GA bytes to the right
2531 * color-map entry.
2532 */
2533 expand_tRNS = 1;
2534
2535 if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
2536 png_error(png_ptr, "rgb[ga] color-map: too few entries");
2537
2538 cmap_entries = (unsigned int)make_ga_colormap(display);
2539 background_index = PNG_CMAP_GA_BACKGROUND;
2540 output_processing = PNG_CMAP_GA;
2541 }
2542
2543 else
2544 {
2545 /* Either the input or the output has no alpha channel, so there
2546 * will be no non-opaque pixels in the color-map; it will just be
2547 * grayscale.
2548 */
2549 if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
2550 png_error(png_ptr, "rgb[gray] color-map: too few entries");
2551
2552 /* Ideally this code would use libpng to do the gamma correction,
2553 * but if an input alpha channel is to be removed we will hit the
2554 * libpng bug in gamma+compose+rgb-to-gray (the double gamma
2555 * correction bug). Fix this by dropping the gamma correction in
2556 * this case and doing it in the palette; this will result in
2557 * duplicate palette entries, but that's better than the
2558 * alternative of double gamma correction.
2559 */
2560 if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2561 png_ptr->num_trans > 0) &&
2562 png_gamma_not_sRGB(png_ptr->colorspace.gamma) != 0)
2563 {
2564 cmap_entries = (unsigned int)make_gray_file_colormap(display);
2565 data_encoding = P_FILE;
2566 }
2567
2568 else
2569 cmap_entries = (unsigned int)make_gray_colormap(display);
2570
2571 /* But if the input has alpha or transparency it must be removed
2572 */
2573 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2574 png_ptr->num_trans > 0)
2575 {
2576 png_color_16 c;
2577 png_uint_32 gray = back_g;
2578
2579 /* We need to ensure that the application background exists in
2580 * the colormap and that completely transparent pixels map to
2581 * it. Achieve this simply by ensuring that the entry
2582 * selected for the background really is the background color.
2583 */
2584 if (data_encoding == P_FILE) /* from the fixup above */
2585 {
2586 /* The app supplied a gray which is in output_encoding, we
2587 * need to convert it to a value of the input (P_FILE)
2588 * encoding then set this palette entry to the required
2589 * output encoding.
2590 */
2591 if (output_encoding == P_sRGB)
2592 gray = png_sRGB_table[gray]; /* now P_LINEAR */
2593
2594 gray = PNG_DIV257(png_gamma_16bit_correct(gray,
2595 png_ptr->colorspace.gamma)); /* now P_FILE */
2596
2597 /* And make sure the corresponding palette entry contains
2598 * exactly the required sRGB value.
2599 */
2600 png_create_colormap_entry(display, gray, back_g, back_g,
2601 back_g, 0/*unused*/, output_encoding);
2602 }
2603
2604 else if (output_encoding == P_LINEAR)
2605 {
2606 gray = PNG_sRGB_FROM_LINEAR(gray * 255);
2607
2608 /* And make sure the corresponding palette entry matches.
2609 */
2610 png_create_colormap_entry(display, gray, back_g, back_g,
2611 back_g, 0/*unused*/, P_LINEAR);
2612 }
2613
2614 /* The background passed to libpng, however, must be the
2615 * output (normally sRGB) value.
2616 */
2617 c.index = 0; /*unused*/
2618 c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
2619
2620 /* NOTE: the following is apparently a bug in libpng. Without
2621 * it the transparent color recognition in
2622 * png_set_background_fixed seems to go wrong.
2623 */
2624 expand_tRNS = 1;
2625 png_set_background_fixed(png_ptr, &c,
2626 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2627 0/*gamma: not used*/);
2628 }
2629
2630 output_processing = PNG_CMAP_NONE;
2631 }
2632 }
2633
2634 else /* output is color */
2635 {
2636 /* We could use png_quantize here so long as there is no transparent
2637 * color or alpha; png_quantize ignores alpha. Easier overall just
2638 * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
2639 * Consequently we always want libpng to produce sRGB data.
2640 */
2641 data_encoding = P_sRGB;
2642
2643 /* Is there any transparency or alpha? */
2644 if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
2645 png_ptr->num_trans > 0)
2646 {
2647 /* Is there alpha in the output too? If so all four channels are
2648 * processed into a special RGB cube with alpha support.
2649 */
2650 if ((output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
2651 {
2652 png_uint_32 r;
2653
2654 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2655 png_error(png_ptr, "rgb+alpha color-map: too few entries");
2656
2657 cmap_entries = (unsigned int)make_rgb_colormap(display);
2658
2659 /* Add a transparent entry. */
2660 png_create_colormap_entry(display, cmap_entries, 255, 255,
2661 255, 0, P_sRGB);
2662
2663 /* This is stored as the background index for the processing
2664 * algorithm.
2665 */
2666 background_index = cmap_entries++;
2667
2668 /* Add 27 r,g,b entries each with alpha 0.5. */
2669 for (r=0; r<256; r = (r << 1) | 0x7f)
2670 {
2671 png_uint_32 g;
2672
2673 for (g=0; g<256; g = (g << 1) | 0x7f)
2674 {
2675 png_uint_32 b;
2676
2677 /* This generates components with the values 0, 127 and
2678 * 255
2679 */
2680 for (b=0; b<256; b = (b << 1) | 0x7f)
2681 png_create_colormap_entry(display, cmap_entries++,
2682 r, g, b, 128, P_sRGB);
2683 }
2684 }
2685
2686 expand_tRNS = 1;
2687 output_processing = PNG_CMAP_RGB_ALPHA;
2688 }
2689
2690 else
2691 {
2692 /* Alpha/transparency must be removed. The background must
2693 * exist in the color map (achieved by setting adding it after
2694 * the 666 color-map). If the standard processing code will
2695 * pick up this entry automatically that's all that is
2696 * required; libpng can be called to do the background
2697 * processing.
2698 */
2699 unsigned int sample_size =
2700 PNG_IMAGE_SAMPLE_SIZE(output_format);
2701 png_uint_32 r, g, b; /* sRGB background */
2702
2703 if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
2704 png_error(png_ptr, "rgb-alpha color-map: too few entries");
2705
2706 cmap_entries = (unsigned int)make_rgb_colormap(display);
2707
2708 png_create_colormap_entry(display, cmap_entries, back_r,
2709 back_g, back_b, 0/*unused*/, output_encoding);
2710
2711 if (output_encoding == P_LINEAR)
2712 {
2713 r = PNG_sRGB_FROM_LINEAR(back_r * 255);
2714 g = PNG_sRGB_FROM_LINEAR(back_g * 255);
2715 b = PNG_sRGB_FROM_LINEAR(back_b * 255);
2716 }
2717
2718 else
2719 {
2720 r = back_r;
2721 g = back_g;
2722 b = back_g;
2723 }
2724
2725 /* Compare the newly-created color-map entry with the one the
2726 * PNG_CMAP_RGB algorithm will use. If the two entries don't
2727 * match, add the new one and set this as the background
2728 * index.
2729 */
2730 if (memcmp((png_const_bytep)display->colormap +
2731 sample_size * cmap_entries,
2732 (png_const_bytep)display->colormap +
2733 sample_size * PNG_RGB_INDEX(r,g,b),
2734 sample_size) != 0)
2735 {
2736 /* The background color must be added. */
2737 background_index = cmap_entries++;
2738
2739 /* Add 27 r,g,b entries each with created by composing with
2740 * the background at alpha 0.5.
2741 */
2742 for (r=0; r<256; r = (r << 1) | 0x7f)
2743 {
2744 for (g=0; g<256; g = (g << 1) | 0x7f)
2745 {
2746 /* This generates components with the values 0, 127
2747 * and 255
2748 */
2749 for (b=0; b<256; b = (b << 1) | 0x7f)
2750 png_create_colormap_entry(display, cmap_entries++,
2751 png_colormap_compose(display, r, P_sRGB, 128,
2752 back_r, output_encoding),
2753 png_colormap_compose(display, g, P_sRGB, 128,
2754 back_g, output_encoding),
2755 png_colormap_compose(display, b, P_sRGB, 128,
2756 back_b, output_encoding),
2757 0/*unused*/, output_encoding);
2758 }
2759 }
2760
2761 expand_tRNS = 1;
2762 output_processing = PNG_CMAP_RGB_ALPHA;
2763 }
2764
2765 else /* background color is in the standard color-map */
2766 {
2767 png_color_16 c;
2768
2769 c.index = 0; /*unused*/
2770 c.red = (png_uint_16)back_r;
2771 c.gray = c.green = (png_uint_16)back_g;
2772 c.blue = (png_uint_16)back_b;
2773
2774 png_set_background_fixed(png_ptr, &c,
2775 PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
2776 0/*gamma: not used*/);
2777
2778 output_processing = PNG_CMAP_RGB;
2779 }
2780 }
2781 }
2782
2783 else /* no alpha or transparency in the input */
2784 {
2785 /* Alpha in the output is irrelevant, simply map the opaque input
2786 * pixels to the 6x6x6 color-map.
2787 */
2788 if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
2789 png_error(png_ptr, "rgb color-map: too few entries");
2790
2791 cmap_entries = (unsigned int)make_rgb_colormap(display);
2792 output_processing = PNG_CMAP_RGB;
2793 }
2794 }
2795 break;
2796
2797 case PNG_COLOR_TYPE_PALETTE:
2798 /* It's already got a color-map. It may be necessary to eliminate the
2799 * tRNS entries though.
2800 */
2801 {
2802 unsigned int num_trans = png_ptr->num_trans;
2803 png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
2804 png_const_colorp colormap = png_ptr->palette;
2805 const int do_background = trans != NULL &&
2806 (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
2807 unsigned int i;
2808
2809 /* Just in case: */
2810 if (trans == NULL)
2811 num_trans = 0;
2812
2813 output_processing = PNG_CMAP_NONE;
2814 data_encoding = P_FILE; /* Don't change from color-map indices */
2815 cmap_entries = (unsigned int)png_ptr->num_palette;
2816 if (cmap_entries > 256)
2817 cmap_entries = 256;
2818
2819 if (cmap_entries > (unsigned int)image->colormap_entries)
2820 png_error(png_ptr, "palette color-map: too few entries");
2821
2822 for (i=0; i < cmap_entries; ++i)
2823 {
2824 if (do_background != 0 && i < num_trans && trans[i] < 255)
2825 {
2826 if (trans[i] == 0)
2827 png_create_colormap_entry(display, i, back_r, back_g,
2828 back_b, 0, output_encoding);
2829
2830 else
2831 {
2832 /* Must compose the PNG file color in the color-map entry
2833 * on the sRGB color in 'back'.
2834 */
2835 png_create_colormap_entry(display, i,
2836 png_colormap_compose(display, colormap[i].red,
2837 P_FILE, trans[i], back_r, output_encoding),
2838 png_colormap_compose(display, colormap[i].green,
2839 P_FILE, trans[i], back_g, output_encoding),
2840 png_colormap_compose(display, colormap[i].blue,
2841 P_FILE, trans[i], back_b, output_encoding),
2842 output_encoding == P_LINEAR ? trans[i] * 257U :
2843 trans[i],
2844 output_encoding);
2845 }
2846 }
2847
2848 else
2849 png_create_colormap_entry(display, i, colormap[i].red,
2850 colormap[i].green, colormap[i].blue,
2851 i < num_trans ? trans[i] : 255U, P_FILE/*8-bit*/);
2852 }
2853
2854 /* The PNG data may have indices packed in fewer than 8 bits, it
2855 * must be expanded if so.
2856 */
2857 if (png_ptr->bit_depth < 8)
2858 png_set_packing(png_ptr);
2859 }
2860 break;
2861
2862 default:
2863 png_error(png_ptr, "invalid PNG color type");
2864 /*NOT REACHED*/
2865 }
2866
2867 /* Now deal with the output processing */
2868 if (expand_tRNS != 0 && png_ptr->num_trans > 0 &&
2869 (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
2870 png_set_tRNS_to_alpha(png_ptr);
2871
2872 switch (data_encoding)
2873 {
2874 case P_sRGB:
2875 /* Change to 8-bit sRGB */
2876 png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
2877 /* FALLTHROUGH */
2878
2879 case P_FILE:
2880 if (png_ptr->bit_depth > 8)
2881 png_set_scale_16(png_ptr);
2882 break;
2883
2884 #ifdef __GNUC__
2885 default:
2886 png_error(png_ptr, "bad data option (internal error)");
2887 #endif
2888 }
2889
2890 if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
2891 png_error(png_ptr, "color map overflow (BAD internal error)");
2892
2893 image->colormap_entries = cmap_entries;
2894
2895 /* Double check using the recorded background index */
2896 switch (output_processing)
2897 {
2898 case PNG_CMAP_NONE:
2899 if (background_index != PNG_CMAP_NONE_BACKGROUND)
2900 goto bad_background;
2901 break;
2902
2903 case PNG_CMAP_GA:
2904 if (background_index != PNG_CMAP_GA_BACKGROUND)
2905 goto bad_background;
2906 break;
2907
2908 case PNG_CMAP_TRANS:
2909 if (background_index >= cmap_entries ||
2910 background_index != PNG_CMAP_TRANS_BACKGROUND)
2911 goto bad_background;
2912 break;
2913
2914 case PNG_CMAP_RGB:
2915 if (background_index != PNG_CMAP_RGB_BACKGROUND)
2916 goto bad_background;
2917 break;
2918
2919 case PNG_CMAP_RGB_ALPHA:
2920 if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
2921 goto bad_background;
2922 break;
2923
2924 default:
2925 png_error(png_ptr, "bad processing option (internal error)");
2926
2927 bad_background:
2928 png_error(png_ptr, "bad background index (internal error)");
2929 }
2930
2931 display->colormap_processing = (int)output_processing;
2932
2933 return 1/*ok*/;
2934 }
2935
2936 /* The final part of the color-map read called from png_image_finish_read. */
2937 static int
2938 png_image_read_and_map(png_voidp argument)
2939 {
2940 png_image_read_control *display = png_voidcast(png_image_read_control*,
2941 argument);
2942 png_imagep image = display->image;
2943 png_structrp png_ptr = image->opaque->png_ptr;
2944 int passes;
2945
2946 /* Called when the libpng data must be transformed into the color-mapped
2947 * form. There is a local row buffer in display->local and this routine must
2948 * do the interlace handling.
2949 */
2950 switch (png_ptr->interlaced)
2951 {
2952 case PNG_INTERLACE_NONE:
2953 passes = 1;
2954 break;
2955
2956 case PNG_INTERLACE_ADAM7:
2957 passes = PNG_INTERLACE_ADAM7_PASSES;
2958 break;
2959
2960 default:
2961 png_error(png_ptr, "unknown interlace type");
2962 }
2963
2964 {
2965 png_uint_32 height = image->height;
2966 png_uint_32 width = image->width;
2967 int proc = display->colormap_processing;
2968 png_bytep first_row = png_voidcast(png_bytep, display->first_row);
2969 ptrdiff_t step_row = display->row_bytes;
2970 int pass;
2971
2972 for (pass = 0; pass < passes; ++pass)
2973 {
2974 unsigned int startx, stepx, stepy;
2975 png_uint_32 y;
2976
2977 if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
2978 {
2979 /* The row may be empty for a short image: */
2980 if (PNG_PASS_COLS(width, pass) == 0)
2981 continue;
2982
2983 startx = PNG_PASS_START_COL(pass);
2984 stepx = PNG_PASS_COL_OFFSET(pass);
2985 y = PNG_PASS_START_ROW(pass);
2986 stepy = PNG_PASS_ROW_OFFSET(pass);
2987 }
2988
2989 else
2990 {
2991 y = 0;
2992 startx = 0;
2993 stepx = stepy = 1;
2994 }
2995
2996 for (; y<height; y += stepy)
2997 {
2998 png_bytep inrow = png_voidcast(png_bytep, display->local_row);
2999 png_bytep outrow = first_row + y * step_row;
3000 png_const_bytep end_row = outrow + width;
3001
3002 /* Read read the libpng data into the temporary buffer. */
3003 png_read_row(png_ptr, inrow, NULL);
3004
3005 /* Now process the row according to the processing option, note
3006 * that the caller verifies that the format of the libpng output
3007 * data is as required.
3008 */
3009 outrow += startx;
3010 switch (proc)
3011 {
3012 case PNG_CMAP_GA:
3013 for (; outrow < end_row; outrow += stepx)
3014 {
3015 /* The data is always in the PNG order */
3016 unsigned int gray = *inrow++;
3017 unsigned int alpha = *inrow++;
3018 unsigned int entry;
3019
3020 /* NOTE: this code is copied as a comment in
3021 * make_ga_colormap above. Please update the
3022 * comment if you change this code!
3023 */
3024 if (alpha > 229) /* opaque */
3025 {
3026 entry = (231 * gray + 128) >> 8;
3027 }
3028 else if (alpha < 26) /* transparent */
3029 {
3030 entry = 231;
3031 }
3032 else /* partially opaque */
3033 {
3034 entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
3035 }
3036
3037 *outrow = (png_byte)entry;
3038 }
3039 break;
3040
3041 case PNG_CMAP_TRANS:
3042 for (; outrow < end_row; outrow += stepx)
3043 {
3044 png_byte gray = *inrow++;
3045 png_byte alpha = *inrow++;
3046
3047 if (alpha == 0)
3048 *outrow = PNG_CMAP_TRANS_BACKGROUND;
3049
3050 else if (gray != PNG_CMAP_TRANS_BACKGROUND)
3051 *outrow = gray;
3052
3053 else
3054 *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
3055 }
3056 break;
3057
3058 case PNG_CMAP_RGB:
3059 for (; outrow < end_row; outrow += stepx)
3060 {
3061 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
3062 inrow += 3;
3063 }
3064 break;
3065
3066 case PNG_CMAP_RGB_ALPHA:
3067 for (; outrow < end_row; outrow += stepx)
3068 {
3069 unsigned int alpha = inrow[3];
3070
3071 /* Because the alpha entries only hold alpha==0.5 values
3072 * split the processing at alpha==0.25 (64) and 0.75
3073 * (196).
3074 */
3075
3076 if (alpha >= 196)
3077 *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
3078 inrow[2]);
3079
3080 else if (alpha < 64)
3081 *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
3082
3083 else
3084 {
3085 /* Likewise there are three entries for each of r, g
3086 * and b. We could select the entry by popcount on
3087 * the top two bits on those architectures that
3088 * support it, this is what the code below does,
3089 * crudely.
3090 */
3091 unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
3092
3093 /* Here are how the values map:
3094 *
3095 * 0x00 .. 0x3f -> 0
3096 * 0x40 .. 0xbf -> 1
3097 * 0xc0 .. 0xff -> 2
3098 *
3099 * So, as above with the explicit alpha checks, the
3100 * breakpoints are at 64 and 196.
3101 */
3102 if (inrow[0] & 0x80) back_i += 9; /* red */
3103 if (inrow[0] & 0x40) back_i += 9;
3104 if (inrow[0] & 0x80) back_i += 3; /* green */
3105 if (inrow[0] & 0x40) back_i += 3;
3106 if (inrow[0] & 0x80) back_i += 1; /* blue */
3107 if (inrow[0] & 0x40) back_i += 1;
3108
3109 *outrow = (png_byte)back_i;
3110 }
3111
3112 inrow += 4;
3113 }
3114 break;
3115
3116 default:
3117 break;
3118 }
3119 }
3120 }
3121 }
3122
3123 return 1;
3124 }
3125
3126 static int
3127 png_image_read_colormapped(png_voidp argument)
3128 {
3129 png_image_read_control *display = png_voidcast(png_image_read_control*,
3130 argument);
3131 png_imagep image = display->image;
3132 png_controlp control = image->opaque;
3133 png_structrp png_ptr = control->png_ptr;
3134 png_inforp info_ptr = control->info_ptr;
3135
3136 int passes = 0; /* As a flag */
3137
3138 PNG_SKIP_CHUNKS(png_ptr);
3139
3140 /* Update the 'info' structure and make sure the result is as required; first
3141 * make sure to turn on the interlace handling if it will be required
3142 * (because it can't be turned on *after* the call to png_read_update_info!)
3143 */
3144 if (display->colormap_processing == PNG_CMAP_NONE)
3145 passes = png_set_interlace_handling(png_ptr);
3146
3147 png_read_update_info(png_ptr, info_ptr);
3148
3149 /* The expected output can be deduced from the colormap_processing option. */
3150 switch (display->colormap_processing)
3151 {
3152 case PNG_CMAP_NONE:
3153 /* Output must be one channel and one byte per pixel, the output
3154 * encoding can be anything.
3155 */
3156 if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
3157 info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
3158 info_ptr->bit_depth == 8)
3159 break;
3160
3161 goto bad_output;
3162
3163 case PNG_CMAP_TRANS:
3164 case PNG_CMAP_GA:
3165 /* Output must be two channels and the 'G' one must be sRGB, the latter
3166 * can be checked with an exact number because it should have been set
3167 * to this number above!
3168 */
3169 if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
3170 info_ptr->bit_depth == 8 &&
3171 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3172 image->colormap_entries == 256)
3173 break;
3174
3175 goto bad_output;
3176
3177 case PNG_CMAP_RGB:
3178 /* Output must be 8-bit sRGB encoded RGB */
3179 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
3180 info_ptr->bit_depth == 8 &&
3181 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3182 image->colormap_entries == 216)
3183 break;
3184
3185 goto bad_output;
3186
3187 case PNG_CMAP_RGB_ALPHA:
3188 /* Output must be 8-bit sRGB encoded RGBA */
3189 if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
3190 info_ptr->bit_depth == 8 &&
3191 png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
3192 image->colormap_entries == 244 /* 216 + 1 + 27 */)
3193 break;
3194
3195 goto bad_output;
3196
3197 default:
3198 bad_output:
3199 png_error(png_ptr, "bad color-map processing (internal error)");
3200 }
3201
3202 /* Now read the rows. Do this here if it is possible to read directly into
3203 * the output buffer, otherwise allocate a local row buffer of the maximum
3204 * size libpng requires and call the relevant processing routine safely.
3205 */
3206 {
3207 png_voidp first_row = display->buffer;
3208 ptrdiff_t row_bytes = display->row_stride;
3209
3210 /* The following expression is designed to work correctly whether it gives
3211 * a signed or an unsigned result.
3212 */
3213 if (row_bytes < 0)
3214 {
3215 char *ptr = png_voidcast(char*, first_row);
3216 ptr += (image->height-1) * (-row_bytes);
3217 first_row = png_voidcast(png_voidp, ptr);
3218 }
3219
3220 display->first_row = first_row;
3221 display->row_bytes = row_bytes;
3222 }
3223
3224 if (passes == 0)
3225 {
3226 int result;
3227 png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
3228
3229 display->local_row = row;
3230 result = png_safe_execute(image, png_image_read_and_map, display);
3231 display->local_row = NULL;
3232 png_free(png_ptr, row);
3233
3234 return result;
3235 }
3236
3237 else
3238 {
3239 png_alloc_size_t row_bytes = (png_alloc_size_t)display->row_bytes;
3240
3241 while (--passes >= 0)
3242 {
3243 png_uint_32 y = image->height;
3244 png_bytep row = png_voidcast(png_bytep, display->first_row)