[LIBPNG] Update to v1.6.19.
[reactos.git] / reactos / dll / 3rdparty / libpng / png.c
1
2 /* png.c - location for general purpose libpng functions
3 *
4 * Last changed in libpng 1.6.19 [November 12, 2015]
5 * Copyright (c) 1998-2015 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
8 *
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
12 */
13
14 #include "pngpriv.h"
15
16 /* Generate a compiler error if there is an old png.h in the search path. */
17 typedef png_libpng_version_1_6_19 Your_png_h_is_not_version_1_6_19;
18
19 /* Tells libpng that we have already handled the first "num_bytes" bytes
20 * of the PNG file signature. If the PNG data is embedded into another
21 * stream we can set num_bytes = 8 so that libpng will not attempt to read
22 * or write any of the magic bytes before it starts on the IHDR.
23 */
24
25 #ifdef PNG_READ_SUPPORTED
26 void PNGAPI
27 png_set_sig_bytes(png_structrp png_ptr, int num_bytes)
28 {
29 unsigned int nb = (unsigned int)num_bytes;
30
31 png_debug(1, "in png_set_sig_bytes");
32
33 if (png_ptr == NULL)
34 return;
35
36 if (num_bytes < 0)
37 nb = 0;
38
39 if (nb > 8)
40 png_error(png_ptr, "Too many bytes for PNG signature");
41
42 png_ptr->sig_bytes = (png_byte)nb;
43 }
44
45 /* Checks whether the supplied bytes match the PNG signature. We allow
46 * checking less than the full 8-byte signature so that those apps that
47 * already read the first few bytes of a file to determine the file type
48 * can simply check the remaining bytes for extra assurance. Returns
49 * an integer less than, equal to, or greater than zero if sig is found,
50 * respectively, to be less than, to match, or be greater than the correct
51 * PNG signature (this is the same behavior as strcmp, memcmp, etc).
52 */
53 int PNGAPI
54 png_sig_cmp(png_const_bytep sig, png_size_t start, png_size_t num_to_check)
55 {
56 png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
57
58 if (num_to_check > 8)
59 num_to_check = 8;
60
61 else if (num_to_check < 1)
62 return (-1);
63
64 if (start > 7)
65 return (-1);
66
67 if (start + num_to_check > 8)
68 num_to_check = 8 - start;
69
70 return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check)));
71 }
72
73 #endif /* READ */
74
75 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
76 /* Function to allocate memory for zlib */
77 PNG_FUNCTION(voidpf /* PRIVATE */,
78 png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)
79 {
80 png_alloc_size_t num_bytes = size;
81
82 if (png_ptr == NULL)
83 return NULL;
84
85 if (items >= (~(png_alloc_size_t)0)/size)
86 {
87 png_warning (png_voidcast(png_structrp, png_ptr),
88 "Potential overflow in png_zalloc()");
89 return NULL;
90 }
91
92 num_bytes *= items;
93 return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes);
94 }
95
96 /* Function to free memory for zlib */
97 void /* PRIVATE */
98 png_zfree(voidpf png_ptr, voidpf ptr)
99 {
100 png_free(png_voidcast(png_const_structrp,png_ptr), ptr);
101 }
102
103 /* Reset the CRC variable to 32 bits of 1's. Care must be taken
104 * in case CRC is > 32 bits to leave the top bits 0.
105 */
106 void /* PRIVATE */
107 png_reset_crc(png_structrp png_ptr)
108 {
109 /* The cast is safe because the crc is a 32-bit value. */
110 png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0);
111 }
112
113 /* Calculate the CRC over a section of data. We can only pass as
114 * much data to this routine as the largest single buffer size. We
115 * also check that this data will actually be used before going to the
116 * trouble of calculating it.
117 */
118 void /* PRIVATE */
119 png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, png_size_t length)
120 {
121 int need_crc = 1;
122
123 if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
124 {
125 if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
126 (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
127 need_crc = 0;
128 }
129
130 else /* critical */
131 {
132 if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
133 need_crc = 0;
134 }
135
136 /* 'uLong' is defined in zlib.h as unsigned long; this means that on some
137 * systems it is a 64-bit value. crc32, however, returns 32 bits so the
138 * following cast is safe. 'uInt' may be no more than 16 bits, so it is
139 * necessary to perform a loop here.
140 */
141 if (need_crc != 0 && length > 0)
142 {
143 uLong crc = png_ptr->crc; /* Should never issue a warning */
144
145 do
146 {
147 uInt safe_length = (uInt)length;
148 #ifndef __COVERITY__
149 if (safe_length == 0)
150 safe_length = (uInt)-1; /* evil, but safe */
151 #endif
152
153 crc = crc32(crc, ptr, safe_length);
154
155 /* The following should never issue compiler warnings; if they do the
156 * target system has characteristics that will probably violate other
157 * assumptions within the libpng code.
158 */
159 ptr += safe_length;
160 length -= safe_length;
161 }
162 while (length > 0);
163
164 /* And the following is always safe because the crc is only 32 bits. */
165 png_ptr->crc = (png_uint_32)crc;
166 }
167 }
168
169 /* Check a user supplied version number, called from both read and write
170 * functions that create a png_struct.
171 */
172 int
173 png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)
174 {
175 /* Libpng versions 1.0.0 and later are binary compatible if the version
176 * string matches through the second '.'; we must recompile any
177 * applications that use any older library version.
178 */
179
180 if (user_png_ver != NULL)
181 {
182 int i = -1;
183 int found_dots = 0;
184
185 do
186 {
187 i++;
188 if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i])
189 png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
190 if (user_png_ver[i] == '.')
191 found_dots++;
192 } while (found_dots < 2 && user_png_ver[i] != 0 &&
193 PNG_LIBPNG_VER_STRING[i] != 0);
194 }
195
196 else
197 png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
198
199 if ((png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH) != 0)
200 {
201 #ifdef PNG_WARNINGS_SUPPORTED
202 size_t pos = 0;
203 char m[128];
204
205 pos = png_safecat(m, (sizeof m), pos,
206 "Application built with libpng-");
207 pos = png_safecat(m, (sizeof m), pos, user_png_ver);
208 pos = png_safecat(m, (sizeof m), pos, " but running with ");
209 pos = png_safecat(m, (sizeof m), pos, PNG_LIBPNG_VER_STRING);
210 PNG_UNUSED(pos)
211
212 png_warning(png_ptr, m);
213 #endif
214
215 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
216 png_ptr->flags = 0;
217 #endif
218
219 return 0;
220 }
221
222 /* Success return. */
223 return 1;
224 }
225
226 /* Generic function to create a png_struct for either read or write - this
227 * contains the common initialization.
228 */
229 PNG_FUNCTION(png_structp /* PRIVATE */,
230 png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
231 png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
232 png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
233 {
234 png_struct create_struct;
235 # ifdef PNG_SETJMP_SUPPORTED
236 jmp_buf create_jmp_buf;
237 # endif
238
239 /* This temporary stack-allocated structure is used to provide a place to
240 * build enough context to allow the user provided memory allocator (if any)
241 * to be called.
242 */
243 memset(&create_struct, 0, (sizeof create_struct));
244
245 /* Added at libpng-1.2.6 */
246 # ifdef PNG_USER_LIMITS_SUPPORTED
247 create_struct.user_width_max = PNG_USER_WIDTH_MAX;
248 create_struct.user_height_max = PNG_USER_HEIGHT_MAX;
249
250 # ifdef PNG_USER_CHUNK_CACHE_MAX
251 /* Added at libpng-1.2.43 and 1.4.0 */
252 create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
253 # endif
254
255 # ifdef PNG_USER_CHUNK_MALLOC_MAX
256 /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
257 * in png_struct regardless.
258 */
259 create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
260 # endif
261 # endif
262
263 /* The following two API calls simply set fields in png_struct, so it is safe
264 * to do them now even though error handling is not yet set up.
265 */
266 # ifdef PNG_USER_MEM_SUPPORTED
267 png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn);
268 # else
269 PNG_UNUSED(mem_ptr)
270 PNG_UNUSED(malloc_fn)
271 PNG_UNUSED(free_fn)
272 # endif
273
274 /* (*error_fn) can return control to the caller after the error_ptr is set,
275 * this will result in a memory leak unless the error_fn does something
276 * extremely sophisticated. The design lacks merit but is implicit in the
277 * API.
278 */
279 png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn);
280
281 # ifdef PNG_SETJMP_SUPPORTED
282 if (!setjmp(create_jmp_buf))
283 # endif
284 {
285 # ifdef PNG_SETJMP_SUPPORTED
286 /* Temporarily fake out the longjmp information until we have
287 * successfully completed this function. This only works if we have
288 * setjmp() support compiled in, but it is safe - this stuff should
289 * never happen.
290 */
291 create_struct.jmp_buf_ptr = &create_jmp_buf;
292 create_struct.jmp_buf_size = 0; /*stack allocation*/
293 create_struct.longjmp_fn = longjmp;
294 # endif
295 /* Call the general version checker (shared with read and write code):
296 */
297 if (png_user_version_check(&create_struct, user_png_ver) != 0)
298 {
299 png_structrp png_ptr = png_voidcast(png_structrp,
300 png_malloc_warn(&create_struct, (sizeof *png_ptr)));
301
302 if (png_ptr != NULL)
303 {
304 /* png_ptr->zstream holds a back-pointer to the png_struct, so
305 * this can only be done now:
306 */
307 create_struct.zstream.zalloc = png_zalloc;
308 create_struct.zstream.zfree = png_zfree;
309 create_struct.zstream.opaque = png_ptr;
310
311 # ifdef PNG_SETJMP_SUPPORTED
312 /* Eliminate the local error handling: */
313 create_struct.jmp_buf_ptr = NULL;
314 create_struct.jmp_buf_size = 0;
315 create_struct.longjmp_fn = 0;
316 # endif
317
318 *png_ptr = create_struct;
319
320 /* This is the successful return point */
321 return png_ptr;
322 }
323 }
324 }
325
326 /* A longjmp because of a bug in the application storage allocator or a
327 * simple failure to allocate the png_struct.
328 */
329 return NULL;
330 }
331
332 /* Allocate the memory for an info_struct for the application. */
333 PNG_FUNCTION(png_infop,PNGAPI
334 png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED)
335 {
336 png_inforp info_ptr;
337
338 png_debug(1, "in png_create_info_struct");
339
340 if (png_ptr == NULL)
341 return NULL;
342
343 /* Use the internal API that does not (or at least should not) error out, so
344 * that this call always returns ok. The application typically sets up the
345 * error handling *after* creating the info_struct because this is the way it
346 * has always been done in 'example.c'.
347 */
348 info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,
349 (sizeof *info_ptr)));
350
351 if (info_ptr != NULL)
352 memset(info_ptr, 0, (sizeof *info_ptr));
353
354 return info_ptr;
355 }
356
357 /* This function frees the memory associated with a single info struct.
358 * Normally, one would use either png_destroy_read_struct() or
359 * png_destroy_write_struct() to free an info struct, but this may be
360 * useful for some applications. From libpng 1.6.0 this function is also used
361 * internally to implement the png_info release part of the 'struct' destroy
362 * APIs. This ensures that all possible approaches free the same data (all of
363 * it).
364 */
365 void PNGAPI
366 png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)
367 {
368 png_inforp info_ptr = NULL;
369
370 png_debug(1, "in png_destroy_info_struct");
371
372 if (png_ptr == NULL)
373 return;
374
375 if (info_ptr_ptr != NULL)
376 info_ptr = *info_ptr_ptr;
377
378 if (info_ptr != NULL)
379 {
380 /* Do this first in case of an error below; if the app implements its own
381 * memory management this can lead to png_free calling png_error, which
382 * will abort this routine and return control to the app error handler.
383 * An infinite loop may result if it then tries to free the same info
384 * ptr.
385 */
386 *info_ptr_ptr = NULL;
387
388 png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
389 memset(info_ptr, 0, (sizeof *info_ptr));
390 png_free(png_ptr, info_ptr);
391 }
392 }
393
394 /* Initialize the info structure. This is now an internal function (0.89)
395 * and applications using it are urged to use png_create_info_struct()
396 * instead. Use deprecated in 1.6.0, internal use removed (used internally it
397 * is just a memset).
398 *
399 * NOTE: it is almost inconceivable that this API is used because it bypasses
400 * the user-memory mechanism and the user error handling/warning mechanisms in
401 * those cases where it does anything other than a memset.
402 */
403 PNG_FUNCTION(void,PNGAPI
404 png_info_init_3,(png_infopp ptr_ptr, png_size_t png_info_struct_size),
405 PNG_DEPRECATED)
406 {
407 png_inforp info_ptr = *ptr_ptr;
408
409 png_debug(1, "in png_info_init_3");
410
411 if (info_ptr == NULL)
412 return;
413
414 if ((sizeof (png_info)) > png_info_struct_size)
415 {
416 *ptr_ptr = NULL;
417 /* The following line is why this API should not be used: */
418 free(info_ptr);
419 info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
420 (sizeof *info_ptr)));
421 if (info_ptr == NULL)
422 return;
423 *ptr_ptr = info_ptr;
424 }
425
426 /* Set everything to 0 */
427 memset(info_ptr, 0, (sizeof *info_ptr));
428 }
429
430 /* The following API is not called internally */
431 void PNGAPI
432 png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,
433 int freer, png_uint_32 mask)
434 {
435 png_debug(1, "in png_data_freer");
436
437 if (png_ptr == NULL || info_ptr == NULL)
438 return;
439
440 if (freer == PNG_DESTROY_WILL_FREE_DATA)
441 info_ptr->free_me |= mask;
442
443 else if (freer == PNG_USER_WILL_FREE_DATA)
444 info_ptr->free_me &= ~mask;
445
446 else
447 png_error(png_ptr, "Unknown freer parameter in png_data_freer");
448 }
449
450 void PNGAPI
451 png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,
452 int num)
453 {
454 png_debug(1, "in png_free_data");
455
456 if (png_ptr == NULL || info_ptr == NULL)
457 return;
458
459 #ifdef PNG_TEXT_SUPPORTED
460 /* Free text item num or (if num == -1) all text items */
461 if (info_ptr->text != 0 &&
462 ((mask & PNG_FREE_TEXT) & info_ptr->free_me) != 0)
463 {
464 if (num != -1)
465 {
466 png_free(png_ptr, info_ptr->text[num].key);
467 info_ptr->text[num].key = NULL;
468 }
469
470 else
471 {
472 int i;
473
474 for (i = 0; i < info_ptr->num_text; i++)
475 png_free(png_ptr, info_ptr->text[i].key);
476
477 png_free(png_ptr, info_ptr->text);
478 info_ptr->text = NULL;
479 info_ptr->num_text = 0;
480 }
481 }
482 #endif
483
484 #ifdef PNG_tRNS_SUPPORTED
485 /* Free any tRNS entry */
486 if (((mask & PNG_FREE_TRNS) & info_ptr->free_me) != 0)
487 {
488 info_ptr->valid &= ~PNG_INFO_tRNS;
489 png_free(png_ptr, info_ptr->trans_alpha);
490 info_ptr->trans_alpha = NULL;
491 info_ptr->num_trans = 0;
492 }
493 #endif
494
495 #ifdef PNG_sCAL_SUPPORTED
496 /* Free any sCAL entry */
497 if (((mask & PNG_FREE_SCAL) & info_ptr->free_me) != 0)
498 {
499 png_free(png_ptr, info_ptr->scal_s_width);
500 png_free(png_ptr, info_ptr->scal_s_height);
501 info_ptr->scal_s_width = NULL;
502 info_ptr->scal_s_height = NULL;
503 info_ptr->valid &= ~PNG_INFO_sCAL;
504 }
505 #endif
506
507 #ifdef PNG_pCAL_SUPPORTED
508 /* Free any pCAL entry */
509 if (((mask & PNG_FREE_PCAL) & info_ptr->free_me) != 0)
510 {
511 png_free(png_ptr, info_ptr->pcal_purpose);
512 png_free(png_ptr, info_ptr->pcal_units);
513 info_ptr->pcal_purpose = NULL;
514 info_ptr->pcal_units = NULL;
515
516 if (info_ptr->pcal_params != NULL)
517 {
518 int i;
519
520 for (i = 0; i < info_ptr->pcal_nparams; i++)
521 png_free(png_ptr, info_ptr->pcal_params[i]);
522
523 png_free(png_ptr, info_ptr->pcal_params);
524 info_ptr->pcal_params = NULL;
525 }
526 info_ptr->valid &= ~PNG_INFO_pCAL;
527 }
528 #endif
529
530 #ifdef PNG_iCCP_SUPPORTED
531 /* Free any profile entry */
532 if (((mask & PNG_FREE_ICCP) & info_ptr->free_me) != 0)
533 {
534 png_free(png_ptr, info_ptr->iccp_name);
535 png_free(png_ptr, info_ptr->iccp_profile);
536 info_ptr->iccp_name = NULL;
537 info_ptr->iccp_profile = NULL;
538 info_ptr->valid &= ~PNG_INFO_iCCP;
539 }
540 #endif
541
542 #ifdef PNG_sPLT_SUPPORTED
543 /* Free a given sPLT entry, or (if num == -1) all sPLT entries */
544 if (info_ptr->splt_palettes != 0 &&
545 ((mask & PNG_FREE_SPLT) & info_ptr->free_me) != 0)
546 {
547 if (num != -1)
548 {
549 png_free(png_ptr, info_ptr->splt_palettes[num].name);
550 png_free(png_ptr, info_ptr->splt_palettes[num].entries);
551 info_ptr->splt_palettes[num].name = NULL;
552 info_ptr->splt_palettes[num].entries = NULL;
553 }
554
555 else
556 {
557 int i;
558
559 for (i = 0; i < info_ptr->splt_palettes_num; i++)
560 {
561 png_free(png_ptr, info_ptr->splt_palettes[i].name);
562 png_free(png_ptr, info_ptr->splt_palettes[i].entries);
563 }
564
565 png_free(png_ptr, info_ptr->splt_palettes);
566 info_ptr->splt_palettes = NULL;
567 info_ptr->splt_palettes_num = 0;
568 info_ptr->valid &= ~PNG_INFO_sPLT;
569 }
570 }
571 #endif
572
573 #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
574 if (info_ptr->unknown_chunks != 0 &&
575 ((mask & PNG_FREE_UNKN) & info_ptr->free_me) != 0)
576 {
577 if (num != -1)
578 {
579 png_free(png_ptr, info_ptr->unknown_chunks[num].data);
580 info_ptr->unknown_chunks[num].data = NULL;
581 }
582
583 else
584 {
585 int i;
586
587 for (i = 0; i < info_ptr->unknown_chunks_num; i++)
588 png_free(png_ptr, info_ptr->unknown_chunks[i].data);
589
590 png_free(png_ptr, info_ptr->unknown_chunks);
591 info_ptr->unknown_chunks = NULL;
592 info_ptr->unknown_chunks_num = 0;
593 }
594 }
595 #endif
596
597 #ifdef PNG_hIST_SUPPORTED
598 /* Free any hIST entry */
599 if (((mask & PNG_FREE_HIST) & info_ptr->free_me) != 0)
600 {
601 png_free(png_ptr, info_ptr->hist);
602 info_ptr->hist = NULL;
603 info_ptr->valid &= ~PNG_INFO_hIST;
604 }
605 #endif
606
607 /* Free any PLTE entry that was internally allocated */
608 if (((mask & PNG_FREE_PLTE) & info_ptr->free_me) != 0)
609 {
610 png_free(png_ptr, info_ptr->palette);
611 info_ptr->palette = NULL;
612 info_ptr->valid &= ~PNG_INFO_PLTE;
613 info_ptr->num_palette = 0;
614 }
615
616 #ifdef PNG_INFO_IMAGE_SUPPORTED
617 /* Free any image bits attached to the info structure */
618 if (((mask & PNG_FREE_ROWS) & info_ptr->free_me) != 0)
619 {
620 if (info_ptr->row_pointers != 0)
621 {
622 png_uint_32 row;
623 for (row = 0; row < info_ptr->height; row++)
624 png_free(png_ptr, info_ptr->row_pointers[row]);
625
626 png_free(png_ptr, info_ptr->row_pointers);
627 info_ptr->row_pointers = NULL;
628 }
629 info_ptr->valid &= ~PNG_INFO_IDAT;
630 }
631 #endif
632
633 if (num != -1)
634 mask &= ~PNG_FREE_MUL;
635
636 info_ptr->free_me &= ~mask;
637 }
638 #endif /* READ || WRITE */
639
640 /* This function returns a pointer to the io_ptr associated with the user
641 * functions. The application should free any memory associated with this
642 * pointer before png_write_destroy() or png_read_destroy() are called.
643 */
644 png_voidp PNGAPI
645 png_get_io_ptr(png_const_structrp png_ptr)
646 {
647 if (png_ptr == NULL)
648 return (NULL);
649
650 return (png_ptr->io_ptr);
651 }
652
653 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
654 # ifdef PNG_STDIO_SUPPORTED
655 /* Initialize the default input/output functions for the PNG file. If you
656 * use your own read or write routines, you can call either png_set_read_fn()
657 * or png_set_write_fn() instead of png_init_io(). If you have defined
658 * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
659 * function of your own because "FILE *" isn't necessarily available.
660 */
661 void PNGAPI
662 png_init_io(png_structrp png_ptr, png_FILE_p fp)
663 {
664 png_debug(1, "in png_init_io");
665
666 if (png_ptr == NULL)
667 return;
668
669 png_ptr->io_ptr = (png_voidp)fp;
670 }
671 # endif
672
673 # ifdef PNG_SAVE_INT_32_SUPPORTED
674 /* PNG signed integers are saved in 32-bit 2's complement format. ANSI C-90
675 * defines a cast of a signed integer to an unsigned integer either to preserve
676 * the value, if it is positive, or to calculate:
677 *
678 * (UNSIGNED_MAX+1) + integer
679 *
680 * Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
681 * negative integral value is added the result will be an unsigned value
682 * correspnding to the 2's complement representation.
683 */
684 void PNGAPI
685 png_save_int_32(png_bytep buf, png_int_32 i)
686 {
687 png_save_uint_32(buf, i);
688 }
689 # endif
690
691 # ifdef PNG_TIME_RFC1123_SUPPORTED
692 /* Convert the supplied time into an RFC 1123 string suitable for use in
693 * a "Creation Time" or other text-based time string.
694 */
695 int PNGAPI
696 png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
697 {
698 static PNG_CONST char short_months[12][4] =
699 {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
700 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
701
702 if (out == NULL)
703 return 0;
704
705 if (ptime->year > 9999 /* RFC1123 limitation */ ||
706 ptime->month == 0 || ptime->month > 12 ||
707 ptime->day == 0 || ptime->day > 31 ||
708 ptime->hour > 23 || ptime->minute > 59 ||
709 ptime->second > 60)
710 return 0;
711
712 {
713 size_t pos = 0;
714 char number_buf[5]; /* enough for a four-digit year */
715
716 # define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))
717 # define APPEND_NUMBER(format, value)\
718 APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
719 # define APPEND(ch) if (pos < 28) out[pos++] = (ch)
720
721 APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day);
722 APPEND(' ');
723 APPEND_STRING(short_months[(ptime->month - 1)]);
724 APPEND(' ');
725 APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);
726 APPEND(' ');
727 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour);
728 APPEND(':');
729 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute);
730 APPEND(':');
731 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);
732 APPEND_STRING(" +0000"); /* This reliably terminates the buffer */
733 PNG_UNUSED (pos)
734
735 # undef APPEND
736 # undef APPEND_NUMBER
737 # undef APPEND_STRING
738 }
739
740 return 1;
741 }
742
743 # if PNG_LIBPNG_VER < 10700
744 /* To do: remove the following from libpng-1.7 */
745 /* Original API that uses a private buffer in png_struct.
746 * Deprecated because it causes png_struct to carry a spurious temporary
747 * buffer (png_struct::time_buffer), better to have the caller pass this in.
748 */
749 png_const_charp PNGAPI
750 png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)
751 {
752 if (png_ptr != NULL)
753 {
754 /* The only failure above if png_ptr != NULL is from an invalid ptime */
755 if (png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime) == 0)
756 png_warning(png_ptr, "Ignoring invalid time value");
757
758 else
759 return png_ptr->time_buffer;
760 }
761
762 return NULL;
763 }
764 # endif /* LIBPNG_VER < 10700 */
765 # endif /* TIME_RFC1123 */
766
767 #endif /* READ || WRITE */
768
769 png_const_charp PNGAPI
770 png_get_copyright(png_const_structrp png_ptr)
771 {
772 PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
773 #ifdef PNG_STRING_COPYRIGHT
774 return PNG_STRING_COPYRIGHT
775 #else
776 # ifdef __STDC__
777 return PNG_STRING_NEWLINE \
778 "libpng version 1.6.19 - November 12, 2015" PNG_STRING_NEWLINE \
779 "Copyright (c) 1998-2015 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
780 "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
781 "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
782 PNG_STRING_NEWLINE;
783 # else
784 return "libpng version 1.6.19 - November 12, 2015\
785 Copyright (c) 1998-2015 Glenn Randers-Pehrson\
786 Copyright (c) 1996-1997 Andreas Dilger\
787 Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
788 # endif
789 #endif
790 }
791
792 /* The following return the library version as a short string in the
793 * format 1.0.0 through 99.99.99zz. To get the version of *.h files
794 * used with your application, print out PNG_LIBPNG_VER_STRING, which
795 * is defined in png.h.
796 * Note: now there is no difference between png_get_libpng_ver() and
797 * png_get_header_ver(). Due to the version_nn_nn_nn typedef guard,
798 * it is guaranteed that png.c uses the correct version of png.h.
799 */
800 png_const_charp PNGAPI
801 png_get_libpng_ver(png_const_structrp png_ptr)
802 {
803 /* Version of *.c files used when building libpng */
804 return png_get_header_ver(png_ptr);
805 }
806
807 png_const_charp PNGAPI
808 png_get_header_ver(png_const_structrp png_ptr)
809 {
810 /* Version of *.h files used when building libpng */
811 PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
812 return PNG_LIBPNG_VER_STRING;
813 }
814
815 png_const_charp PNGAPI
816 png_get_header_version(png_const_structrp png_ptr)
817 {
818 /* Returns longer string containing both version and date */
819 PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
820 #ifdef __STDC__
821 return PNG_HEADER_VERSION_STRING
822 # ifndef PNG_READ_SUPPORTED
823 " (NO READ SUPPORT)"
824 # endif
825 PNG_STRING_NEWLINE;
826 #else
827 return PNG_HEADER_VERSION_STRING;
828 #endif
829 }
830
831 #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
832 /* NOTE: this routine is not used internally! */
833 /* Build a grayscale palette. Palette is assumed to be 1 << bit_depth
834 * large of png_color. This lets grayscale images be treated as
835 * paletted. Most useful for gamma correction and simplification
836 * of code. This API is not used internally.
837 */
838 void PNGAPI
839 png_build_grayscale_palette(int bit_depth, png_colorp palette)
840 {
841 int num_palette;
842 int color_inc;
843 int i;
844 int v;
845
846 png_debug(1, "in png_do_build_grayscale_palette");
847
848 if (palette == NULL)
849 return;
850
851 switch (bit_depth)
852 {
853 case 1:
854 num_palette = 2;
855 color_inc = 0xff;
856 break;
857
858 case 2:
859 num_palette = 4;
860 color_inc = 0x55;
861 break;
862
863 case 4:
864 num_palette = 16;
865 color_inc = 0x11;
866 break;
867
868 case 8:
869 num_palette = 256;
870 color_inc = 1;
871 break;
872
873 default:
874 num_palette = 0;
875 color_inc = 0;
876 break;
877 }
878
879 for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
880 {
881 palette[i].red = (png_byte)(v & 0xff);
882 palette[i].green = (png_byte)(v & 0xff);
883 palette[i].blue = (png_byte)(v & 0xff);
884 }
885 }
886 #endif
887
888 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
889 int PNGAPI
890 png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)
891 {
892 /* Check chunk_name and return "keep" value if it's on the list, else 0 */
893 png_const_bytep p, p_end;
894
895 if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0)
896 return PNG_HANDLE_CHUNK_AS_DEFAULT;
897
898 p_end = png_ptr->chunk_list;
899 p = p_end + png_ptr->num_chunk_list*5; /* beyond end */
900
901 /* The code is the fifth byte after each four byte string. Historically this
902 * code was always searched from the end of the list, this is no longer
903 * necessary because the 'set' routine handles duplicate entries correcty.
904 */
905 do /* num_chunk_list > 0, so at least one */
906 {
907 p -= 5;
908
909 if (memcmp(chunk_name, p, 4) == 0)
910 return p[4];
911 }
912 while (p > p_end);
913
914 /* This means that known chunks should be processed and unknown chunks should
915 * be handled according to the value of png_ptr->unknown_default; this can be
916 * confusing because, as a result, there are two levels of defaulting for
917 * unknown chunks.
918 */
919 return PNG_HANDLE_CHUNK_AS_DEFAULT;
920 }
921
922 #if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
923 defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
924 int /* PRIVATE */
925 png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)
926 {
927 png_byte chunk_string[5];
928
929 PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);
930 return png_handle_as_unknown(png_ptr, chunk_string);
931 }
932 #endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */
933 #endif /* SET_UNKNOWN_CHUNKS */
934
935 #ifdef PNG_READ_SUPPORTED
936 /* This function, added to libpng-1.0.6g, is untested. */
937 int PNGAPI
938 png_reset_zstream(png_structrp png_ptr)
939 {
940 if (png_ptr == NULL)
941 return Z_STREAM_ERROR;
942
943 /* WARNING: this resets the window bits to the maximum! */
944 return (inflateReset(&png_ptr->zstream));
945 }
946 #endif /* READ */
947
948 /* This function was added to libpng-1.0.7 */
949 png_uint_32 PNGAPI
950 png_access_version_number(void)
951 {
952 /* Version of *.c files used when building libpng */
953 return((png_uint_32)PNG_LIBPNG_VER);
954 }
955
956 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
957 /* Ensure that png_ptr->zstream.msg holds some appropriate error message string.
958 * If it doesn't 'ret' is used to set it to something appropriate, even in cases
959 * like Z_OK or Z_STREAM_END where the error code is apparently a success code.
960 */
961 void /* PRIVATE */
962 png_zstream_error(png_structrp png_ptr, int ret)
963 {
964 /* Translate 'ret' into an appropriate error string, priority is given to the
965 * one in zstream if set. This always returns a string, even in cases like
966 * Z_OK or Z_STREAM_END where the error code is a success code.
967 */
968 if (png_ptr->zstream.msg == NULL) switch (ret)
969 {
970 default:
971 case Z_OK:
972 png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code");
973 break;
974
975 case Z_STREAM_END:
976 /* Normal exit */
977 png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream");
978 break;
979
980 case Z_NEED_DICT:
981 /* This means the deflate stream did not have a dictionary; this
982 * indicates a bogus PNG.
983 */
984 png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary");
985 break;
986
987 case Z_ERRNO:
988 /* gz APIs only: should not happen */
989 png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error");
990 break;
991
992 case Z_STREAM_ERROR:
993 /* internal libpng error */
994 png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib");
995 break;
996
997 case Z_DATA_ERROR:
998 png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream");
999 break;
1000
1001 case Z_MEM_ERROR:
1002 png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory");
1003 break;
1004
1005 case Z_BUF_ERROR:
1006 /* End of input or output; not a problem if the caller is doing
1007 * incremental read or write.
1008 */
1009 png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated");
1010 break;
1011
1012 case Z_VERSION_ERROR:
1013 png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version");
1014 break;
1015
1016 case PNG_UNEXPECTED_ZLIB_RETURN:
1017 /* Compile errors here mean that zlib now uses the value co-opted in
1018 * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above
1019 * and change pngpriv.h. Note that this message is "... return",
1020 * whereas the default/Z_OK one is "... return code".
1021 */
1022 png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return");
1023 break;
1024 }
1025 }
1026
1027 /* png_convert_size: a PNGAPI but no longer in png.h, so deleted
1028 * at libpng 1.5.5!
1029 */
1030
1031 /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
1032 #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */
1033 static int
1034 png_colorspace_check_gamma(png_const_structrp png_ptr,
1035 png_colorspacerp colorspace, png_fixed_point gAMA, int from)
1036 /* This is called to check a new gamma value against an existing one. The
1037 * routine returns false if the new gamma value should not be written.
1038 *
1039 * 'from' says where the new gamma value comes from:
1040 *
1041 * 0: the new gamma value is the libpng estimate for an ICC profile
1042 * 1: the new gamma value comes from a gAMA chunk
1043 * 2: the new gamma value comes from an sRGB chunk
1044 */
1045 {
1046 png_fixed_point gtest;
1047
1048 if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
1049 (png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) == 0 ||
1050 png_gamma_significant(gtest) != 0))
1051 {
1052 /* Either this is an sRGB image, in which case the calculated gamma
1053 * approximation should match, or this is an image with a profile and the
1054 * value libpng calculates for the gamma of the profile does not match the
1055 * value recorded in the file. The former, sRGB, case is an error, the
1056 * latter is just a warning.
1057 */
1058 if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)
1059 {
1060 png_chunk_report(png_ptr, "gamma value does not match sRGB",
1061 PNG_CHUNK_ERROR);
1062 /* Do not overwrite an sRGB value */
1063 return from == 2;
1064 }
1065
1066 else /* sRGB tag not involved */
1067 {
1068 png_chunk_report(png_ptr, "gamma value does not match libpng estimate",
1069 PNG_CHUNK_WARNING);
1070 return from == 1;
1071 }
1072 }
1073
1074 return 1;
1075 }
1076
1077 void /* PRIVATE */
1078 png_colorspace_set_gamma(png_const_structrp png_ptr,
1079 png_colorspacerp colorspace, png_fixed_point gAMA)
1080 {
1081 /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
1082 * occur. Since the fixed point representation is asymetrical it is
1083 * possible for 1/gamma to overflow the limit of 21474 and this means the
1084 * gamma value must be at least 5/100000 and hence at most 20000.0. For
1085 * safety the limits here are a little narrower. The values are 0.00016 to
1086 * 6250.0, which are truly ridiculous gamma values (and will produce
1087 * displays that are all black or all white.)
1088 *
1089 * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk
1090 * handling code, which only required the value to be >0.
1091 */
1092 png_const_charp errmsg;
1093
1094 if (gAMA < 16 || gAMA > 625000000)
1095 errmsg = "gamma value out of range";
1096
1097 # ifdef PNG_READ_gAMA_SUPPORTED
1098 /* Allow the application to set the gamma value more than once */
1099 else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
1100 (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
1101 errmsg = "duplicate";
1102 # endif
1103
1104 /* Do nothing if the colorspace is already invalid */
1105 else if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
1106 return;
1107
1108 else
1109 {
1110 if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA,
1111 1/*from gAMA*/) != 0)
1112 {
1113 /* Store this gamma value. */
1114 colorspace->gamma = gAMA;
1115 colorspace->flags |=
1116 (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA);
1117 }
1118
1119 /* At present if the check_gamma test fails the gamma of the colorspace is
1120 * not updated however the colorspace is not invalidated. This
1121 * corresponds to the case where the existing gamma comes from an sRGB
1122 * chunk or profile. An error message has already been output.
1123 */
1124 return;
1125 }
1126
1127 /* Error exit - errmsg has been set. */
1128 colorspace->flags |= PNG_COLORSPACE_INVALID;
1129 png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR);
1130 }
1131
1132 void /* PRIVATE */
1133 png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)
1134 {
1135 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0)
1136 {
1137 /* Everything is invalid */
1138 info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB|
1139 PNG_INFO_iCCP);
1140
1141 # ifdef PNG_COLORSPACE_SUPPORTED
1142 /* Clean up the iCCP profile now if it won't be used. */
1143 png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
1144 # else
1145 PNG_UNUSED(png_ptr)
1146 # endif
1147 }
1148
1149 else
1150 {
1151 # ifdef PNG_COLORSPACE_SUPPORTED
1152 /* Leave the INFO_iCCP flag set if the pngset.c code has already set
1153 * it; this allows a PNG to contain a profile which matches sRGB and
1154 * yet still have that profile retrievable by the application.
1155 */
1156 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0)
1157 info_ptr->valid |= PNG_INFO_sRGB;
1158
1159 else
1160 info_ptr->valid &= ~PNG_INFO_sRGB;
1161
1162 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
1163 info_ptr->valid |= PNG_INFO_cHRM;
1164
1165 else
1166 info_ptr->valid &= ~PNG_INFO_cHRM;
1167 # endif
1168
1169 if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0)
1170 info_ptr->valid |= PNG_INFO_gAMA;
1171
1172 else
1173 info_ptr->valid &= ~PNG_INFO_gAMA;
1174 }
1175 }
1176
1177 #ifdef PNG_READ_SUPPORTED
1178 void /* PRIVATE */
1179 png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)
1180 {
1181 if (info_ptr == NULL) /* reduce code size; check here not in the caller */
1182 return;
1183
1184 info_ptr->colorspace = png_ptr->colorspace;
1185 png_colorspace_sync_info(png_ptr, info_ptr);
1186 }
1187 #endif
1188 #endif /* GAMMA */
1189
1190 #ifdef PNG_COLORSPACE_SUPPORTED
1191 /* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
1192 * cHRM, as opposed to using chromaticities. These internal APIs return
1193 * non-zero on a parameter error. The X, Y and Z values are required to be
1194 * positive and less than 1.0.
1195 */
1196 static int
1197 png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)
1198 {
1199 png_int_32 d, dwhite, whiteX, whiteY;
1200
1201 d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;
1202 if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d) == 0)
1203 return 1;
1204 if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d) == 0)
1205 return 1;
1206 dwhite = d;
1207 whiteX = XYZ->red_X;
1208 whiteY = XYZ->red_Y;
1209
1210 d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;
1211 if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d) == 0)
1212 return 1;
1213 if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d) == 0)
1214 return 1;
1215 dwhite += d;
1216 whiteX += XYZ->green_X;
1217 whiteY += XYZ->green_Y;
1218
1219 d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;
1220 if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d) == 0)
1221 return 1;
1222 if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d) == 0)
1223 return 1;
1224 dwhite += d;
1225 whiteX += XYZ->blue_X;
1226 whiteY += XYZ->blue_Y;
1227
1228 /* The reference white is simply the sum of the end-point (X,Y,Z) vectors,
1229 * thus:
1230 */
1231 if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) == 0)
1232 return 1;
1233 if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0)
1234 return 1;
1235
1236 return 0;
1237 }
1238
1239 static int
1240 png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)
1241 {
1242 png_fixed_point red_inverse, green_inverse, blue_scale;
1243 png_fixed_point left, right, denominator;
1244
1245 /* Check xy and, implicitly, z. Note that wide gamut color spaces typically
1246 * have end points with 0 tristimulus values (these are impossible end
1247 * points, but they are used to cover the possible colors). We check
1248 * xy->whitey against 5, not 0, to avoid a possible integer overflow.
1249 */
1250 if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1;
1251 if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1;
1252 if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1;
1253 if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1;
1254 if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1;
1255 if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1;
1256 if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1;
1257 if (xy->whitey < 5 || xy->whitey > PNG_FP_1-xy->whitex) return 1;
1258
1259 /* The reverse calculation is more difficult because the original tristimulus
1260 * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
1261 * derived values were recorded in the cHRM chunk;
1262 * (red,green,blue,white)x(x,y). This loses one degree of freedom and
1263 * therefore an arbitrary ninth value has to be introduced to undo the
1264 * original transformations.
1265 *
1266 * Think of the original end-points as points in (X,Y,Z) space. The
1267 * chromaticity values (c) have the property:
1268 *
1269 * C
1270 * c = ---------
1271 * X + Y + Z
1272 *
1273 * For each c (x,y,z) from the corresponding original C (X,Y,Z). Thus the
1274 * three chromaticity values (x,y,z) for each end-point obey the
1275 * relationship:
1276 *
1277 * x + y + z = 1
1278 *
1279 * This describes the plane in (X,Y,Z) space that intersects each axis at the
1280 * value 1.0; call this the chromaticity plane. Thus the chromaticity
1281 * calculation has scaled each end-point so that it is on the x+y+z=1 plane
1282 * and chromaticity is the intersection of the vector from the origin to the
1283 * (X,Y,Z) value with the chromaticity plane.
1284 *
1285 * To fully invert the chromaticity calculation we would need the three
1286 * end-point scale factors, (red-scale, green-scale, blue-scale), but these
1287 * were not recorded. Instead we calculated the reference white (X,Y,Z) and
1288 * recorded the chromaticity of this. The reference white (X,Y,Z) would have
1289 * given all three of the scale factors since:
1290 *
1291 * color-C = color-c * color-scale
1292 * white-C = red-C + green-C + blue-C
1293 * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
1294 *
1295 * But cHRM records only white-x and white-y, so we have lost the white scale
1296 * factor:
1297 *
1298 * white-C = white-c*white-scale
1299 *
1300 * To handle this the inverse transformation makes an arbitrary assumption
1301 * about white-scale:
1302 *
1303 * Assume: white-Y = 1.0
1304 * Hence: white-scale = 1/white-y
1305 * Or: red-Y + green-Y + blue-Y = 1.0
1306 *
1307 * Notice the last statement of the assumption gives an equation in three of
1308 * the nine values we want to calculate. 8 more equations come from the
1309 * above routine as summarised at the top above (the chromaticity
1310 * calculation):
1311 *
1312 * Given: color-x = color-X / (color-X + color-Y + color-Z)
1313 * Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0
1314 *
1315 * This is 9 simultaneous equations in the 9 variables "color-C" and can be
1316 * solved by Cramer's rule. Cramer's rule requires calculating 10 9x9 matrix
1317 * determinants, however this is not as bad as it seems because only 28 of
1318 * the total of 90 terms in the various matrices are non-zero. Nevertheless
1319 * Cramer's rule is notoriously numerically unstable because the determinant
1320 * calculation involves the difference of large, but similar, numbers. It is
1321 * difficult to be sure that the calculation is stable for real world values
1322 * and it is certain that it becomes unstable where the end points are close
1323 * together.
1324 *
1325 * So this code uses the perhaps slightly less optimal but more
1326 * understandable and totally obvious approach of calculating color-scale.
1327 *
1328 * This algorithm depends on the precision in white-scale and that is
1329 * (1/white-y), so we can immediately see that as white-y approaches 0 the
1330 * accuracy inherent in the cHRM chunk drops off substantially.
1331 *
1332 * libpng arithmetic: a simple inversion of the above equations
1333 * ------------------------------------------------------------
1334 *
1335 * white_scale = 1/white-y
1336 * white-X = white-x * white-scale
1337 * white-Y = 1.0
1338 * white-Z = (1 - white-x - white-y) * white_scale
1339 *
1340 * white-C = red-C + green-C + blue-C
1341 * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
1342 *
1343 * This gives us three equations in (red-scale,green-scale,blue-scale) where
1344 * all the coefficients are now known:
1345 *
1346 * red-x*red-scale + green-x*green-scale + blue-x*blue-scale
1347 * = white-x/white-y
1348 * red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
1349 * red-z*red-scale + green-z*green-scale + blue-z*blue-scale
1350 * = (1 - white-x - white-y)/white-y
1351 *
1352 * In the last equation color-z is (1 - color-x - color-y) so we can add all
1353 * three equations together to get an alternative third:
1354 *
1355 * red-scale + green-scale + blue-scale = 1/white-y = white-scale
1356 *
1357 * So now we have a Cramer's rule solution where the determinants are just
1358 * 3x3 - far more tractible. Unfortunately 3x3 determinants still involve
1359 * multiplication of three coefficients so we can't guarantee to avoid
1360 * overflow in the libpng fixed point representation. Using Cramer's rule in
1361 * floating point is probably a good choice here, but it's not an option for
1362 * fixed point. Instead proceed to simplify the first two equations by
1363 * eliminating what is likely to be the largest value, blue-scale:
1364 *
1365 * blue-scale = white-scale - red-scale - green-scale
1366 *
1367 * Hence:
1368 *
1369 * (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =
1370 * (white-x - blue-x)*white-scale
1371 *
1372 * (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =
1373 * 1 - blue-y*white-scale
1374 *
1375 * And now we can trivially solve for (red-scale,green-scale):
1376 *
1377 * green-scale =
1378 * (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale
1379 * -----------------------------------------------------------
1380 * green-x - blue-x
1381 *
1382 * red-scale =
1383 * 1 - blue-y*white-scale - (green-y - blue-y) * green-scale
1384 * ---------------------------------------------------------
1385 * red-y - blue-y
1386 *
1387 * Hence:
1388 *
1389 * red-scale =
1390 * ( (green-x - blue-x) * (white-y - blue-y) -
1391 * (green-y - blue-y) * (white-x - blue-x) ) / white-y
1392 * -------------------------------------------------------------------------
1393 * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
1394 *
1395 * green-scale =
1396 * ( (red-y - blue-y) * (white-x - blue-x) -
1397 * (red-x - blue-x) * (white-y - blue-y) ) / white-y
1398 * -------------------------------------------------------------------------
1399 * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
1400 *
1401 * Accuracy:
1402 * The input values have 5 decimal digits of accuracy. The values are all in
1403 * the range 0 < value < 1, so simple products are in the same range but may
1404 * need up to 10 decimal digits to preserve the original precision and avoid
1405 * underflow. Because we are using a 32-bit signed representation we cannot
1406 * match this; the best is a little over 9 decimal digits, less than 10.
1407 *
1408 * The approach used here is to preserve the maximum precision within the
1409 * signed representation. Because the red-scale calculation above uses the
1410 * difference between two products of values that must be in the range -1..+1
1411 * it is sufficient to divide the product by 7; ceil(100,000/32767*2). The
1412 * factor is irrelevant in the calculation because it is applied to both
1413 * numerator and denominator.
1414 *
1415 * Note that the values of the differences of the products of the
1416 * chromaticities in the above equations tend to be small, for example for
1417 * the sRGB chromaticities they are:
1418 *
1419 * red numerator: -0.04751
1420 * green numerator: -0.08788
1421 * denominator: -0.2241 (without white-y multiplication)
1422 *
1423 * The resultant Y coefficients from the chromaticities of some widely used
1424 * color space definitions are (to 15 decimal places):
1425 *
1426 * sRGB
1427 * 0.212639005871510 0.715168678767756 0.072192315360734
1428 * Kodak ProPhoto
1429 * 0.288071128229293 0.711843217810102 0.000085653960605
1430 * Adobe RGB
1431 * 0.297344975250536 0.627363566255466 0.075291458493998
1432 * Adobe Wide Gamut RGB
1433 * 0.258728243040113 0.724682314948566 0.016589442011321
1434 */
1435 /* By the argument, above overflow should be impossible here. The return
1436 * value of 2 indicates an internal error to the caller.
1437 */
1438 if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7) == 0)
1439 return 2;
1440 if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7) == 0)
1441 return 2;
1442 denominator = left - right;
1443
1444 /* Now find the red numerator. */
1445 if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7) == 0)
1446 return 2;
1447 if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7) == 0)
1448 return 2;
1449
1450 /* Overflow is possible here and it indicates an extreme set of PNG cHRM
1451 * chunk values. This calculation actually returns the reciprocal of the
1452 * scale value because this allows us to delay the multiplication of white-y
1453 * into the denominator, which tends to produce a small number.
1454 */
1455 if (png_muldiv(&red_inverse, xy->whitey, denominator, left-right) == 0 ||
1456 red_inverse <= xy->whitey /* r+g+b scales = white scale */)
1457 return 1;
1458
1459 /* Similarly for green_inverse: */
1460 if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7) == 0)
1461 return 2;
1462 if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7) == 0)
1463 return 2;
1464 if (png_muldiv(&green_inverse, xy->whitey, denominator, left-right) == 0 ||
1465 green_inverse <= xy->whitey)
1466 return 1;
1467
1468 /* And the blue scale, the checks above guarantee this can't overflow but it
1469 * can still produce 0 for extreme cHRM values.
1470 */
1471 blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) -
1472 png_reciprocal(green_inverse);
1473 if (blue_scale <= 0)
1474 return 1;
1475
1476
1477 /* And fill in the png_XYZ: */
1478 if (png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse) == 0)
1479 return 1;
1480 if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) == 0)
1481 return 1;
1482 if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
1483 red_inverse) == 0)
1484 return 1;
1485
1486 if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) == 0)
1487 return 1;
1488 if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) == 0)
1489 return 1;
1490 if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
1491 green_inverse) == 0)
1492 return 1;
1493
1494 if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) == 0)
1495 return 1;
1496 if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0)
1497 return 1;
1498 if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
1499 PNG_FP_1) == 0)
1500 return 1;
1501
1502 return 0; /*success*/
1503 }
1504
1505 static int
1506 png_XYZ_normalize(png_XYZ *XYZ)
1507 {
1508 png_int_32 Y;
1509
1510 if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||
1511 XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||
1512 XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)
1513 return 1;
1514
1515 /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.
1516 * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
1517 * relying on addition of two positive values producing a negative one is not
1518 * safe.
1519 */
1520 Y = XYZ->red_Y;
1521 if (0x7fffffff - Y < XYZ->green_X)
1522 return 1;
1523 Y += XYZ->green_Y;
1524 if (0x7fffffff - Y < XYZ->blue_X)
1525 return 1;
1526 Y += XYZ->blue_Y;
1527
1528 if (Y != PNG_FP_1)
1529 {
1530 if (png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y) == 0)
1531 return 1;
1532 if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0)
1533 return 1;
1534 if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0)
1535 return 1;
1536
1537 if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0)
1538 return 1;
1539 if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0)
1540 return 1;
1541 if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0)
1542 return 1;
1543
1544 if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0)
1545 return 1;
1546 if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0)
1547 return 1;
1548 if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0)
1549 return 1;
1550 }
1551
1552 return 0;
1553 }
1554
1555 static int
1556 png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta)
1557 {
1558 /* Allow an error of +/-0.01 (absolute value) on each chromaticity */
1559 if (PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) ||
1560 PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) ||
1561 PNG_OUT_OF_RANGE(xy1->redx, xy2->redx, delta) ||
1562 PNG_OUT_OF_RANGE(xy1->redy, xy2->redy, delta) ||
1563 PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) ||
1564 PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) ||
1565 PNG_OUT_OF_RANGE(xy1->bluex, xy2->bluex, delta) ||
1566 PNG_OUT_OF_RANGE(xy1->bluey, xy2->bluey, delta))
1567 return 0;
1568 return 1;
1569 }
1570
1571 /* Added in libpng-1.6.0, a different check for the validity of a set of cHRM
1572 * chunk chromaticities. Earlier checks used to simply look for the overflow
1573 * condition (where the determinant of the matrix to solve for XYZ ends up zero
1574 * because the chromaticity values are not all distinct.) Despite this it is
1575 * theoretically possible to produce chromaticities that are apparently valid
1576 * but that rapidly degrade to invalid, potentially crashing, sets because of
1577 * arithmetic inaccuracies when calculations are performed on them. The new
1578 * check is to round-trip xy -> XYZ -> xy and then check that the result is
1579 * within a small percentage of the original.
1580 */
1581 static int
1582 png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy)
1583 {
1584 int result;
1585 png_xy xy_test;
1586
1587 /* As a side-effect this routine also returns the XYZ endpoints. */
1588 result = png_XYZ_from_xy(XYZ, xy);
1589 if (result != 0)
1590 return result;
1591
1592 result = png_xy_from_XYZ(&xy_test, XYZ);
1593 if (result != 0)
1594 return result;
1595
1596 if (png_colorspace_endpoints_match(xy, &xy_test,
1597 5/*actually, the math is pretty accurate*/) != 0)
1598 return 0;
1599
1600 /* Too much slip */
1601 return 1;
1602 }
1603
1604 /* This is the check going the other way. The XYZ is modified to normalize it
1605 * (another side-effect) and the xy chromaticities are returned.
1606 */
1607 static int
1608 png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ)
1609 {
1610 int result;
1611 png_XYZ XYZtemp;
1612
1613 result = png_XYZ_normalize(XYZ);
1614 if (result != 0)
1615 return result;
1616
1617 result = png_xy_from_XYZ(xy, XYZ);
1618 if (result != 0)
1619 return result;
1620
1621 XYZtemp = *XYZ;
1622 return png_colorspace_check_xy(&XYZtemp, xy);
1623 }
1624
1625 /* Used to check for an endpoint match against sRGB */
1626 static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */
1627 {
1628 /* color x y */
1629 /* red */ 64000, 33000,
1630 /* green */ 30000, 60000,
1631 /* blue */ 15000, 6000,
1632 /* white */ 31270, 32900
1633 };
1634
1635 static int
1636 png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,
1637 png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,
1638 int preferred)
1639 {
1640 if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
1641 return 0;
1642
1643 /* The consistency check is performed on the chromaticities; this factors out
1644 * variations because of the normalization (or not) of the end point Y
1645 * values.
1646 */
1647 if (preferred < 2 &&
1648 (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
1649 {
1650 /* The end points must be reasonably close to any we already have. The
1651 * following allows an error of up to +/-.001
1652 */
1653 if (png_colorspace_endpoints_match(xy, &colorspace->end_points_xy,
1654 100) == 0)
1655 {
1656 colorspace->flags |= PNG_COLORSPACE_INVALID;
1657 png_benign_error(png_ptr, "inconsistent chromaticities");
1658 return 0; /* failed */
1659 }
1660
1661 /* Only overwrite with preferred values */
1662 if (preferred == 0)
1663 return 1; /* ok, but no change */
1664 }
1665
1666 colorspace->end_points_xy = *xy;
1667 colorspace->end_points_XYZ = *XYZ;
1668 colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS;
1669
1670 /* The end points are normally quoted to two decimal digits, so allow +/-0.01
1671 * on this test.
1672 */
1673 if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000) != 0)
1674 colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB;
1675
1676 else
1677 colorspace->flags &= PNG_COLORSPACE_CANCEL(
1678 PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);
1679
1680 return 2; /* ok and changed */
1681 }
1682
1683 int /* PRIVATE */
1684 png_colorspace_set_chromaticities(png_const_structrp png_ptr,
1685 png_colorspacerp colorspace, const png_xy *xy, int preferred)
1686 {
1687 /* We must check the end points to ensure they are reasonable - in the past
1688 * color management systems have crashed as a result of getting bogus
1689 * colorant values, while this isn't the fault of libpng it is the
1690 * responsibility of libpng because PNG carries the bomb and libpng is in a
1691 * position to protect against it.
1692 */
1693 png_XYZ XYZ;
1694
1695 switch (png_colorspace_check_xy(&XYZ, xy))
1696 {
1697 case 0: /* success */
1698 return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,
1699 preferred);
1700
1701 case 1:
1702 /* We can't invert the chromaticities so we can't produce value XYZ
1703 * values. Likely as not a color management system will fail too.
1704 */
1705 colorspace->flags |= PNG_COLORSPACE_INVALID;
1706 png_benign_error(png_ptr, "invalid chromaticities");
1707 break;
1708
1709 default:
1710 /* libpng is broken; this should be a warning but if it happens we
1711 * want error reports so for the moment it is an error.
1712 */
1713 colorspace->flags |= PNG_COLORSPACE_INVALID;
1714 png_error(png_ptr, "internal error checking chromaticities");
1715 }
1716
1717 return 0; /* failed */
1718 }
1719
1720 int /* PRIVATE */
1721 png_colorspace_set_endpoints(png_const_structrp png_ptr,
1722 png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)
1723 {
1724 png_XYZ XYZ = *XYZ_in;
1725 png_xy xy;
1726
1727 switch (png_colorspace_check_XYZ(&xy, &XYZ))
1728 {
1729 case 0:
1730 return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,
1731 preferred);
1732
1733 case 1:
1734 /* End points are invalid. */
1735 colorspace->flags |= PNG_COLORSPACE_INVALID;
1736 png_benign_error(png_ptr, "invalid end points");
1737 break;
1738
1739 default:
1740 colorspace->flags |= PNG_COLORSPACE_INVALID;
1741 png_error(png_ptr, "internal error checking chromaticities");
1742 }
1743
1744 return 0; /* failed */
1745 }
1746
1747 #if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED)
1748 /* Error message generation */
1749 static char
1750 png_icc_tag_char(png_uint_32 byte)
1751 {
1752 byte &= 0xff;
1753 if (byte >= 32 && byte <= 126)
1754 return (char)byte;
1755 else
1756 return '?';
1757 }
1758
1759 static void
1760 png_icc_tag_name(char *name, png_uint_32 tag)
1761 {
1762 name[0] = '\'';
1763 name[1] = png_icc_tag_char(tag >> 24);
1764 name[2] = png_icc_tag_char(tag >> 16);
1765 name[3] = png_icc_tag_char(tag >> 8);
1766 name[4] = png_icc_tag_char(tag );
1767 name[5] = '\'';
1768 }
1769
1770 static int
1771 is_ICC_signature_char(png_alloc_size_t it)
1772 {
1773 return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) ||
1774 (it >= 97 && it <= 122);
1775 }
1776
1777 static int
1778 is_ICC_signature(png_alloc_size_t it)
1779 {
1780 return is_ICC_signature_char(it >> 24) /* checks all the top bits */ &&
1781 is_ICC_signature_char((it >> 16) & 0xff) &&
1782 is_ICC_signature_char((it >> 8) & 0xff) &&
1783 is_ICC_signature_char(it & 0xff);
1784 }
1785
1786 static int
1787 png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace,
1788 png_const_charp name, png_alloc_size_t value, png_const_charp reason)
1789 {
1790 size_t pos;
1791 char message[196]; /* see below for calculation */
1792
1793 if (colorspace != NULL)
1794 colorspace->flags |= PNG_COLORSPACE_INVALID;
1795
1796 pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */
1797 pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */
1798 pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */
1799 if (is_ICC_signature(value) != 0)
1800 {
1801 /* So 'value' is at most 4 bytes and the following cast is safe */
1802 png_icc_tag_name(message+pos, (png_uint_32)value);
1803 pos += 6; /* total +8; less than the else clause */
1804 message[pos++] = ':';
1805 message[pos++] = ' ';
1806 }
1807 # ifdef PNG_WARNINGS_SUPPORTED
1808 else
1809 {
1810 char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/
1811
1812 pos = png_safecat(message, (sizeof message), pos,
1813 png_format_number(number, number+(sizeof number),
1814 PNG_NUMBER_FORMAT_x, value));
1815 pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/
1816 }
1817 # endif
1818 /* The 'reason' is an arbitrary message, allow +79 maximum 195 */
1819 pos = png_safecat(message, (sizeof message), pos, reason);
1820 PNG_UNUSED(pos)
1821
1822 /* This is recoverable, but make it unconditionally an app_error on write to
1823 * avoid writing invalid ICC profiles into PNG files (i.e., we handle them
1824 * on read, with a warning, but on write unless the app turns off
1825 * application errors the PNG won't be written.)
1826 */
1827 png_chunk_report(png_ptr, message,
1828 (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);
1829
1830 return 0;
1831 }
1832 #endif /* sRGB || iCCP */
1833
1834 #ifdef PNG_sRGB_SUPPORTED
1835 int /* PRIVATE */
1836 png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,
1837 int intent)
1838 {
1839 /* sRGB sets known gamma, end points and (from the chunk) intent. */
1840 /* IMPORTANT: these are not necessarily the values found in an ICC profile
1841 * because ICC profiles store values adapted to a D50 environment; it is
1842 * expected that the ICC profile mediaWhitePointTag will be D50; see the
1843 * checks and code elsewhere to understand this better.
1844 *
1845 * These XYZ values, which are accurate to 5dp, produce rgb to gray
1846 * coefficients of (6968,23435,2366), which are reduced (because they add up
1847 * to 32769 not 32768) to (6968,23434,2366). These are the values that
1848 * libpng has traditionally used (and are the best values given the 15bit
1849 * algorithm used by the rgb to gray code.)
1850 */
1851 static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */
1852 {
1853 /* color X Y Z */
1854 /* red */ 41239, 21264, 1933,
1855 /* green */ 35758, 71517, 11919,
1856 /* blue */ 18048, 7219, 95053
1857 };
1858
1859 /* Do nothing if the colorspace is already invalidated. */
1860 if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
1861 return 0;
1862
1863 /* Check the intent, then check for existing settings. It is valid for the
1864 * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must
1865 * be consistent with the correct values. If, however, this function is
1866 * called below because an iCCP chunk matches sRGB then it is quite
1867 * conceivable that an older app recorded incorrect gAMA and cHRM because of
1868 * an incorrect calculation based on the values in the profile - this does
1869 * *not* invalidate the profile (though it still produces an error, which can
1870 * be ignored.)
1871 */
1872 if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)
1873 return png_icc_profile_error(png_ptr, colorspace, "sRGB",
1874 (unsigned)intent, "invalid sRGB rendering intent");
1875
1876 if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&
1877 colorspace->rendering_intent != intent)
1878 return png_icc_profile_error(png_ptr, colorspace, "sRGB",
1879 (unsigned)intent, "inconsistent rendering intents");
1880
1881 if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)
1882 {
1883 png_benign_error(png_ptr, "duplicate sRGB information ignored");
1884 return 0;
1885 }
1886
1887 /* If the standard sRGB cHRM chunk does not match the one from the PNG file
1888 * warn but overwrite the value with the correct one.
1889 */
1890 if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&
1891 !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,
1892 100))
1893 png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",
1894 PNG_CHUNK_ERROR);
1895
1896 /* This check is just done for the error reporting - the routine always
1897 * returns true when the 'from' argument corresponds to sRGB (2).
1898 */
1899 (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,
1900 2/*from sRGB*/);
1901
1902 /* intent: bugs in GCC force 'int' to be used as the parameter type. */
1903 colorspace->rendering_intent = (png_uint_16)intent;
1904 colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT;
1905
1906 /* endpoints */
1907 colorspace->end_points_xy = sRGB_xy;
1908 colorspace->end_points_XYZ = sRGB_XYZ;
1909 colorspace->flags |=
1910 (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);
1911
1912 /* gamma */
1913 colorspace->gamma = PNG_GAMMA_sRGB_INVERSE;
1914 colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA;
1915
1916 /* Finally record that we have an sRGB profile */
1917 colorspace->flags |=
1918 (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);
1919
1920 return 1; /* set */
1921 }
1922 #endif /* sRGB */
1923
1924 #ifdef PNG_iCCP_SUPPORTED
1925 /* Encoded value of D50 as an ICC XYZNumber. From the ICC 2010 spec the value
1926 * is XYZ(0.9642,1.0,0.8249), which scales to:
1927 *
1928 * (63189.8112, 65536, 54060.6464)
1929 */
1930 static const png_byte D50_nCIEXYZ[12] =
1931 { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };
1932
1933 int /* PRIVATE */
1934 png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
1935 png_const_charp name, png_uint_32 profile_length)
1936 {
1937 if (profile_length < 132)
1938 return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
1939 "too short");
1940
1941 return 1;
1942 }
1943
1944 int /* PRIVATE */
1945 png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
1946 png_const_charp name, png_uint_32 profile_length,
1947 png_const_bytep profile/* first 132 bytes only */, int color_type)
1948 {
1949 png_uint_32 temp;
1950
1951 /* Length check; this cannot be ignored in this code because profile_length
1952 * is used later to check the tag table, so even if the profile seems over
1953 * long profile_length from the caller must be correct. The caller can fix
1954 * this up on read or write by just passing in the profile header length.
1955 */
1956 temp = png_get_uint_32(profile);
1957 if (temp != profile_length)
1958 return png_icc_profile_error(png_ptr, colorspace, name, temp,
1959 "length does not match profile");
1960
1961 temp = (png_uint_32) (*(profile+8));
1962 if (temp > 3 && (profile_length & 3))
1963 return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
1964 "invalid length");
1965
1966 temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */
1967 if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */
1968 profile_length < 132+12*temp) /* truncated tag table */
1969 return png_icc_profile_error(png_ptr, colorspace, name, temp,
1970 "tag count too large");
1971
1972 /* The 'intent' must be valid or we can't store it, ICC limits the intent to
1973 * 16 bits.
1974 */
1975 temp = png_get_uint_32(profile+64);
1976 if (temp >= 0xffff) /* The ICC limit */
1977 return png_icc_profile_error(png_ptr, colorspace, name, temp,
1978 "invalid rendering intent");
1979
1980 /* This is just a warning because the profile may be valid in future
1981 * versions.
1982 */
1983 if (temp >= PNG_sRGB_INTENT_LAST)
1984 (void)png_icc_profile_error(png_ptr, NULL, name, temp,
1985 "intent outside defined range");
1986
1987 /* At this point the tag table can't be checked because it hasn't necessarily
1988 * been loaded; however, various header fields can be checked. These checks
1989 * are for values permitted by the PNG spec in an ICC profile; the PNG spec
1990 * restricts the profiles that can be passed in an iCCP chunk (they must be
1991 * appropriate to processing PNG data!)
1992 */
1993
1994 /* Data checks (could be skipped). These checks must be independent of the
1995 * version number; however, the version number doesn't accomodate changes in
1996 * the header fields (just the known tags and the interpretation of the
1997 * data.)
1998 */
1999 temp = png_get_uint_32(profile+36); /* signature 'ascp' */
2000 if (temp != 0x61637370)
2001 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2002 "invalid signature");
2003
2004 /* Currently the PCS illuminant/adopted white point (the computational
2005 * white point) are required to be D50,
2006 * however the profile contains a record of the illuminant so perhaps ICC
2007 * expects to be able to change this in the future (despite the rationale in
2008 * the introduction for using a fixed PCS adopted white.) Consequently the
2009 * following is just a warning.
2010 */
2011 if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0)
2012 (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/,
2013 "PCS illuminant is not D50");
2014
2015 /* The PNG spec requires this:
2016 * "If the iCCP chunk is present, the image samples conform to the colour
2017 * space represented by the embedded ICC profile as defined by the
2018 * International Color Consortium [ICC]. The colour space of the ICC profile
2019 * shall be an RGB colour space for colour images (PNG colour types 2, 3, and
2020 * 6), or a greyscale colour space for greyscale images (PNG colour types 0
2021 * and 4)."
2022 *
2023 * This checking code ensures the embedded profile (on either read or write)
2024 * conforms to the specification requirements. Notice that an ICC 'gray'
2025 * color-space profile contains the information to transform the monochrome
2026 * data to XYZ or L*a*b (according to which PCS the profile uses) and this
2027 * should be used in preference to the standard libpng K channel replication
2028 * into R, G and B channels.
2029 *
2030 * Previously it was suggested that an RGB profile on grayscale data could be
2031 * handled. However it it is clear that using an RGB profile in this context
2032 * must be an error - there is no specification of what it means. Thus it is
2033 * almost certainly more correct to ignore the profile.
2034 */
2035 temp = png_get_uint_32(profile+16); /* data colour space field */
2036 switch (temp)
2037 {
2038 case 0x52474220: /* 'RGB ' */
2039 if ((color_type & PNG_COLOR_MASK_COLOR) == 0)
2040 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2041 "RGB color space not permitted on grayscale PNG");
2042 break;
2043
2044 case 0x47524159: /* 'GRAY' */
2045 if ((color_type & PNG_COLOR_MASK_COLOR) != 0)
2046 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2047 "Gray color space not permitted on RGB PNG");
2048 break;
2049
2050 default:
2051 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2052 "invalid ICC profile color space");
2053 }
2054
2055 /* It is up to the application to check that the profile class matches the
2056 * application requirements; the spec provides no guidance, but it's pretty
2057 * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer
2058 * ('prtr') or 'spac' (for generic color spaces). Issue a warning in these
2059 * cases. Issue an error for device link or abstract profiles - these don't
2060 * contain the records necessary to transform the color-space to anything
2061 * other than the target device (and not even that for an abstract profile).
2062 * Profiles of these classes may not be embedded in images.
2063 */
2064 temp = png_get_uint_32(profile+12); /* profile/device class */
2065 switch (temp)
2066 {
2067 case 0x73636e72: /* 'scnr' */
2068 case 0x6d6e7472: /* 'mntr' */
2069 case 0x70727472: /* 'prtr' */
2070 case 0x73706163: /* 'spac' */
2071 /* All supported */
2072 break;
2073
2074 case 0x61627374: /* 'abst' */
2075 /* May not be embedded in an image */
2076 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2077 "invalid embedded Abstract ICC profile");
2078
2079 case 0x6c696e6b: /* 'link' */
2080 /* DeviceLink profiles cannot be interpreted in a non-device specific
2081 * fashion, if an app uses the AToB0Tag in the profile the results are
2082 * undefined unless the result is sent to the intended device,
2083 * therefore a DeviceLink profile should not be found embedded in a
2084 * PNG.
2085 */
2086 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2087 "unexpected DeviceLink ICC profile class");
2088
2089 case 0x6e6d636c: /* 'nmcl' */
2090 /* A NamedColor profile is also device specific, however it doesn't
2091 * contain an AToB0 tag that is open to misinterpretation. Almost
2092 * certainly it will fail the tests below.
2093 */
2094 (void)png_icc_profile_error(png_ptr, NULL, name, temp,
2095 "unexpected NamedColor ICC profile class");
2096 break;
2097
2098 default:
2099 /* To allow for future enhancements to the profile accept unrecognized
2100 * profile classes with a warning, these then hit the test below on the
2101 * tag content to ensure they are backward compatible with one of the
2102 * understood profiles.
2103 */
2104 (void)png_icc_profile_error(png_ptr, NULL, name, temp,
2105 "unrecognized ICC profile class");
2106 break;
2107 }
2108
2109 /* For any profile other than a device link one the PCS must be encoded
2110 * either in XYZ or Lab.
2111 */
2112 temp = png_get_uint_32(profile+20);
2113 switch (temp)
2114 {
2115 case 0x58595a20: /* 'XYZ ' */
2116 case 0x4c616220: /* 'Lab ' */
2117 break;
2118
2119 default:
2120 return png_icc_profile_error(png_ptr, colorspace, name, temp,
2121 "unexpected ICC PCS encoding");
2122 }
2123
2124 return 1;
2125 }
2126
2127 int /* PRIVATE */
2128 png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
2129 png_const_charp name, png_uint_32 profile_length,
2130 png_const_bytep profile /* header plus whole tag table */)
2131 {
2132 png_uint_32 tag_count = png_get_uint_32(profile+128);
2133 png_uint_32 itag;
2134 png_const_bytep tag = profile+132; /* The first tag */
2135
2136 /* First scan all the tags in the table and add bits to the icc_info value
2137 * (temporarily in 'tags').
2138 */
2139 for (itag=0; itag < tag_count; ++itag, tag += 12)
2140 {
2141 png_uint_32 tag_id = png_get_uint_32(tag+0);
2142 png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */
2143 png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */
2144
2145 /* The ICC specification does not exclude zero length tags, therefore the
2146 * start might actually be anywhere if there is no data, but this would be
2147 * a clear abuse of the intent of the standard so the start is checked for
2148 * being in range. All defined tag types have an 8 byte header - a 4 byte
2149 * type signature then 0.
2150 */
2151 if ((tag_start & 3) != 0)
2152 {
2153 /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is
2154 * only a warning here because libpng does not care about the
2155 * alignment.
2156 */
2157 (void)png_icc_profile_error(png_ptr, NULL, name, tag_id,
2158 "ICC profile tag start not a multiple of 4");
2159 }
2160
2161 /* This is a hard error; potentially it can cause read outside the
2162 * profile.
2163 */
2164 if (tag_start > profile_length || tag_length > profile_length - tag_start)
2165 return png_icc_profile_error(png_ptr, colorspace, name, tag_id,
2166 "ICC profile tag outside profile");
2167 }
2168
2169 return 1; /* success, maybe with warnings */
2170 }
2171
2172 #ifdef PNG_sRGB_SUPPORTED
2173 #if PNG_sRGB_PROFILE_CHECKS >= 0
2174 /* Information about the known ICC sRGB profiles */
2175 static const struct
2176 {
2177 png_uint_32 adler, crc, length;
2178 png_uint_32 md5[4];
2179 png_byte have_md5;
2180 png_byte is_broken;
2181 png_uint_16 intent;
2182
2183 # define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)
2184 # define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\
2185 { adler, crc, length, md5, broke, intent },
2186
2187 } png_sRGB_checks[] =
2188 {
2189 /* This data comes from contrib/tools/checksum-icc run on downloads of
2190 * all four ICC sRGB profiles from www.color.org.
2191 */
2192 /* adler32, crc32, MD5[4], intent, date, length, file-name */
2193 PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,
2194 PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
2195 "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
2196
2197 /* ICC sRGB v2 perceptual no black-compensation: */
2198 PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
2199 PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
2200 "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
2201
2202 PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
2203 PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
2204 "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
2205
2206 /* ICC sRGB v4 perceptual */
2207 PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
2208 PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
2209 "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
2210
2211 /* The following profiles have no known MD5 checksum. If there is a match
2212 * on the (empty) MD5 the other fields are used to attempt a match and
2213 * a warning is produced. The first two of these profiles have a 'cprt' tag
2214 * which suggests that they were also made by Hewlett Packard.
2215 */
2216 PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
2217 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
2218 "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
2219
2220 /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not
2221 * match the D50 PCS illuminant in the header (it is in fact the D65 values,
2222 * so the white point is recorded as the un-adapted value.) The profiles
2223 * below only differ in one byte - the intent - and are basically the same as
2224 * the previous profile except for the mediaWhitePointTag error and a missing
2225 * chromaticAdaptationTag.
2226 */
2227 PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
2228 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
2229 "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")
2230
2231 PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,
2232 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
2233 "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
2234 };
2235
2236 static int
2237 png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
2238 png_const_bytep profile, uLong adler)
2239 {
2240 /* The quick check is to verify just the MD5 signature and trust the
2241 * rest of the data. Because the profile has already been verified for
2242 * correctness this is safe. png_colorspace_set_sRGB will check the 'intent'
2243 * field too, so if the profile has been edited with an intent not defined
2244 * by sRGB (but maybe defined by a later ICC specification) the read of
2245 * the profile will fail at that point.
2246 */
2247
2248 png_uint_32 length = 0;
2249 png_uint_32 intent = 0x10000; /* invalid */
2250 #if PNG_sRGB_PROFILE_CHECKS > 1
2251 uLong crc = 0; /* the value for 0 length data */
2252 #endif
2253 unsigned int i;
2254
2255 #ifdef PNG_SET_OPTION_SUPPORTED
2256 /* First see if PNG_SKIP_sRGB_CHECK_PROFILE has been set to "on" */
2257 if (((png_ptr->options >> PNG_SKIP_sRGB_CHECK_PROFILE) & 3) ==
2258 PNG_OPTION_ON)
2259 return 0;
2260 #endif
2261
2262 for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)
2263 {
2264 if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&
2265 png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&
2266 png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&
2267 png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])
2268 {
2269 /* This may be one of the old HP profiles without an MD5, in that
2270 * case we can only use the length and Adler32 (note that these
2271 * are not used by default if there is an MD5!)
2272 */
2273 # if PNG_sRGB_PROFILE_CHECKS == 0
2274 if (png_sRGB_checks[i].have_md5 != 0)
2275 return 1+png_sRGB_checks[i].is_broken;
2276 # endif
2277
2278 /* Profile is unsigned or more checks have been configured in. */
2279 if (length == 0)
2280 {
2281 length = png_get_uint_32(profile);
2282 intent = png_get_uint_32(profile+64);
2283 }
2284
2285 /* Length *and* intent must match */
2286 if (length == (png_uint_32) png_sRGB_checks[i].length &&
2287 intent == (png_uint_32) png_sRGB_checks[i].intent)
2288 {
2289 /* Now calculate the adler32 if not done already. */
2290 if (adler == 0)
2291 {
2292 adler = adler32(0, NULL, 0);
2293 adler = adler32(adler, profile, length);
2294 }
2295
2296 if (adler == png_sRGB_checks[i].adler)
2297 {
2298 /* These basic checks suggest that the data has not been
2299 * modified, but if the check level is more than 1 perform
2300 * our own crc32 checksum on the data.
2301 */
2302 # if PNG_sRGB_PROFILE_CHECKS > 1
2303 if (crc == 0)
2304 {
2305 crc = crc32(0, NULL, 0);
2306 crc = crc32(crc, profile, length);
2307 }
2308
2309 /* So this check must pass for the 'return' below to happen.
2310 */
2311 if (crc == png_sRGB_checks[i].crc)
2312 # endif
2313 {
2314 if (png_sRGB_checks[i].is_broken != 0)
2315 {
2316 /* These profiles are known to have bad data that may cause
2317 * problems if they are used, therefore attempt to
2318 * discourage their use, skip the 'have_md5' warning below,
2319 * which is made irrelevant by this error.
2320 */
2321 png_chunk_report(png_ptr, "known incorrect sRGB profile",
2322 PNG_CHUNK_ERROR);
2323 }
2324
2325 /* Warn that this being done; this isn't even an error since
2326 * the profile is perfectly valid, but it would be nice if
2327 * people used the up-to-date ones.
2328 */
2329 else if (png_sRGB_checks[i].have_md5 == 0)
2330 {
2331 png_chunk_report(png_ptr,
2332 "out-of-date sRGB profile with no signature",
2333 PNG_CHUNK_WARNING);
2334 }
2335
2336 return 1+png_sRGB_checks[i].is_broken;
2337 }
2338 }
2339
2340 # if PNG_sRGB_PROFILE_CHECKS > 0
2341 /* The signature matched, but the profile had been changed in some
2342 * way. This probably indicates a data error or uninformed hacking.
2343 * Fall through to "no match".
2344 */
2345 png_chunk_report(png_ptr,
2346 "Not recognizing known sRGB profile that has been edited",
2347 PNG_CHUNK_WARNING);
2348 break;
2349 # endif
2350 }
2351 }
2352 }
2353
2354 return 0; /* no match */
2355 }
2356 #endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */
2357
2358 void /* PRIVATE */
2359 png_icc_set_sRGB(png_const_structrp png_ptr,
2360 png_colorspacerp colorspace, png_const_bytep profile, uLong adler)
2361 {
2362 /* Is this profile one of the known ICC sRGB profiles? If it is, just set
2363 * the sRGB information.
2364 */
2365 #if PNG_sRGB_PROFILE_CHECKS >= 0
2366 if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler) != 0)
2367 #endif
2368 (void)png_colorspace_set_sRGB(png_ptr, colorspace,
2369 (int)/*already checked*/png_get_uint_32(profile+64));
2370 }
2371 #endif /* sRGB */
2372
2373 int /* PRIVATE */
2374 png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,
2375 png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,
2376 int color_type)
2377 {
2378 if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0)
2379 return 0;
2380
2381 if (png_icc_check_length(png_ptr, colorspace, name, profile_length) != 0 &&
2382 png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,
2383 color_type) != 0 &&
2384 png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
2385 profile) != 0)
2386 {
2387 # ifdef PNG_sRGB_SUPPORTED
2388 /* If no sRGB support, don't try storing sRGB information */
2389 png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
2390 # endif
2391 return 1;
2392 }
2393
2394 /* Failure case */
2395 return 0;
2396 }
2397 #endif /* iCCP */
2398
2399 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2400 void /* PRIVATE */
2401 png_colorspace_set_rgb_coefficients(png_structrp png_ptr)
2402 {
2403 /* Set the rgb_to_gray coefficients from the colorspace. */
2404 if (png_ptr->rgb_to_gray_coefficients_set == 0 &&
2405 (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
2406 {
2407 /* png_set_background has not been called, get the coefficients from the Y
2408 * values of the colorspace colorants.
2409 */
2410 png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y;
2411 png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y;
2412 png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y;
2413 png_fixed_point total = r+g+b;
2414
2415 if (total > 0 &&
2416 r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 &&
2417 g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 &&
2418 b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 &&
2419 r+g+b <= 32769)
2420 {
2421 /* We allow 0 coefficients here. r+g+b may be 32769 if two or
2422 * all of the coefficients were rounded up. Handle this by
2423 * reducing the *largest* coefficient by 1; this matches the
2424 * approach used for the default coefficients in pngrtran.c
2425 */
2426 int add = 0;
2427
2428 if (r+g+b > 32768)
2429 add = -1;
2430 else if (r+g+b < 32768)
2431 add = 1;
2432
2433 if (add != 0)
2434 {
2435 if (g >= r && g >= b)
2436 g += add;
2437 else if (r >= g && r >= b)
2438 r += add;
2439 else
2440 b += add;
2441 }
2442
2443 /* Check for an internal error. */
2444 if (r+g+b != 32768)
2445 png_error(png_ptr,
2446 "internal error handling cHRM coefficients");
2447
2448 else
2449 {
2450 png_ptr->rgb_to_gray_red_coeff = (png_uint_16)r;
2451 png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;
2452 }
2453 }
2454
2455 /* This is a png_error at present even though it could be ignored -
2456 * it should never happen, but it is important that if it does, the
2457 * bug is fixed.
2458 */
2459 else
2460 png_error(png_ptr, "internal error handling cHRM->XYZ");
2461 }
2462 }
2463 #endif /* READ_RGB_TO_GRAY */
2464
2465 #endif /* COLORSPACE */
2466
2467 #ifdef __GNUC__
2468 /* This exists solely to work round a warning from GNU C. */
2469 static int /* PRIVATE */
2470 png_gt(size_t a, size_t b)
2471 {
2472 return a > b;
2473 }
2474 #else
2475 # define png_gt(a,b) ((a) > (b))
2476 #endif
2477
2478 void /* PRIVATE */
2479 png_check_IHDR(png_const_structrp png_ptr,
2480 png_uint_32 width, png_uint_32 height, int bit_depth,
2481 int color_type, int interlace_type, int compression_type,
2482 int filter_type)
2483 {
2484 int error = 0;
2485
2486 /* Check for width and height valid values */
2487 if (width == 0)
2488 {
2489 png_warning(png_ptr, "Image width is zero in IHDR");
2490 error = 1;
2491 }
2492
2493 if (width > PNG_UINT_31_MAX)
2494 {
2495 png_warning(png_ptr, "Invalid image width in IHDR");
2496 error = 1;
2497 }
2498
2499 if (png_gt(((width + 7) & (~7)),
2500 ((PNG_SIZE_MAX
2501 - 48 /* big_row_buf hack */
2502 - 1) /* filter byte */
2503 / 8) /* 8-byte RGBA pixels */
2504 - 1)) /* extra max_pixel_depth pad */
2505 {
2506 /* The size of the row must be within the limits of this architecture.
2507 * Because the read code can perform arbitrary transformations the
2508 * maximum size is checked here. Because the code in png_read_start_row
2509 * adds extra space "for safety's sake" in several places a conservative
2510 * limit is used here.
2511 *
2512 * NOTE: it would be far better to check the size that is actually used,
2513 * but the effect in the real world is minor and the changes are more
2514 * extensive, therefore much more dangerous and much more difficult to
2515 * write in a way that avoids compiler warnings.
2516 */
2517 png_warning(png_ptr, "Image width is too large for this architecture");
2518 error = 1;
2519 }
2520
2521 #ifdef PNG_SET_USER_LIMITS_SUPPORTED
2522 if (width > png_ptr->user_width_max)
2523 #else
2524 if (width > PNG_USER_WIDTH_MAX)
2525 #endif
2526 {
2527 png_warning(png_ptr, "Image width exceeds user limit in IHDR");
2528 error = 1;
2529 }
2530
2531 if (height == 0)
2532 {
2533 png_warning(png_ptr, "Image height is zero in IHDR");
2534 error = 1;
2535 }
2536
2537 if (height > PNG_UINT_31_MAX)
2538 {
2539 png_warning(png_ptr, "Invalid image height in IHDR");
2540 error = 1;
2541 }
2542
2543 #ifdef PNG_SET_USER_LIMITS_SUPPORTED
2544 if (height > png_ptr->user_height_max)
2545 #else
2546 if (height > PNG_USER_HEIGHT_MAX)
2547 #endif
2548 {
2549 png_warning(png_ptr, "Image height exceeds user limit in IHDR");
2550 error = 1;
2551 }
2552
2553 /* Check other values */
2554 if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&
2555 bit_depth != 8 && bit_depth != 16)
2556 {
2557 png_warning(png_ptr, "Invalid bit depth in IHDR");
2558 error = 1;
2559 }
2560
2561 if (color_type < 0 || color_type == 1 ||
2562 color_type == 5 || color_type > 6)
2563 {
2564 png_warning(png_ptr, "Invalid color type in IHDR");
2565 error = 1;
2566 }
2567
2568 if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||
2569 ((color_type == PNG_COLOR_TYPE_RGB ||
2570 color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||
2571 color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))
2572 {
2573 png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");
2574 error = 1;
2575 }
2576
2577 if (interlace_type >= PNG_INTERLACE_LAST)
2578 {
2579 png_warning(png_ptr, "Unknown interlace method in IHDR");
2580 error = 1;
2581 }
2582
2583 if (compression_type != PNG_COMPRESSION_TYPE_BASE)
2584 {
2585 png_warning(png_ptr, "Unknown compression method in IHDR");
2586 error = 1;
2587 }
2588
2589 #ifdef PNG_MNG_FEATURES_SUPPORTED
2590 /* Accept filter_method 64 (intrapixel differencing) only if
2591 * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
2592 * 2. Libpng did not read a PNG signature (this filter_method is only
2593 * used in PNG datastreams that are embedded in MNG datastreams) and
2594 * 3. The application called png_permit_mng_features with a mask that
2595 * included PNG_FLAG_MNG_FILTER_64 and
2596 * 4. The filter_method is 64 and
2597 * 5. The color_type is RGB or RGBA
2598 */
2599 if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 &&
2600 png_ptr->mng_features_permitted != 0)
2601 png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
2602
2603 if (filter_type != PNG_FILTER_TYPE_BASE)
2604 {
2605 if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
2606 (filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&
2607 ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
2608 (color_type == PNG_COLOR_TYPE_RGB ||
2609 color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
2610 {
2611 png_warning(png_ptr, "Unknown filter method in IHDR");
2612 error = 1;
2613 }
2614
2615 if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0)
2616 {
2617 png_warning(png_ptr, "Invalid filter method in IHDR");
2618 error = 1;
2619 }
2620 }
2621
2622 #else
2623 if (filter_type != PNG_FILTER_TYPE_BASE)
2624 {
2625 png_warning(png_ptr, "Unknown filter method in IHDR");
2626 error = 1;
2627 }
2628 #endif
2629
2630 if (error == 1)
2631 png_error(png_ptr, "Invalid IHDR data");
2632 }
2633
2634 #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
2635 /* ASCII to fp functions */
2636 /* Check an ASCII formated floating point value, see the more detailed
2637 * comments in pngpriv.h
2638 */
2639 /* The following is used internally to preserve the sticky flags */
2640 #define png_fp_add(state, flags) ((state) |= (flags))
2641 #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
2642
2643 int /* PRIVATE */
2644 png_check_fp_number(png_const_charp string, png_size_t size, int *statep,
2645 png_size_tp whereami)
2646 {
2647 int state = *statep;
2648 png_size_t i = *whereami;
2649
2650 while (i < size)
2651 {
2652 int type;
2653 /* First find the type of the next character */
2654 switch (string[i])
2655 {
2656 case 43: type = PNG_FP_SAW_SIGN; break;
2657 case 45: type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;
2658 case 46: type = PNG_FP_SAW_DOT; break;
2659 case 48: type = PNG_FP_SAW_DIGIT; break;
2660 case 49: case 50: case 51: case 52:
2661 case 53: case 54: case 55: case 56:
2662 case 57: type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;
2663 case 69:
2664 case 101: type = PNG_FP_SAW_E; break;
2665 default: goto PNG_FP_End;
2666 }
2667
2668 /* Now deal with this type according to the current
2669 * state, the type is arranged to not overlap the
2670 * bits of the PNG_FP_STATE.
2671 */
2672 switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
2673 {
2674 case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
2675 if ((state & PNG_FP_SAW_ANY) != 0)
2676 goto PNG_FP_End; /* not a part of the number */
2677
2678 png_fp_add(state, type);
2679 break;
2680
2681 case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
2682 /* Ok as trailer, ok as lead of fraction. */
2683 if ((state & PNG_FP_SAW_DOT) != 0) /* two dots */
2684 goto PNG_FP_End;
2685
2686 else if ((state & PNG_FP_SAW_DIGIT) != 0) /* trailing dot? */
2687 png_fp_add(state, type);
2688
2689 else
2690 png_fp_set(state, PNG_FP_FRACTION | type);
2691
2692 break;
2693
2694 case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
2695 if ((state & PNG_FP_SAW_DOT) != 0) /* delayed fraction */
2696 png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);
2697
2698 png_fp_add(state, type | PNG_FP_WAS_VALID);
2699
2700 break;
2701
2702 case PNG_FP_INTEGER + PNG_FP_SAW_E:
2703 if ((state & PNG_FP_SAW_DIGIT) == 0)
2704 goto PNG_FP_End;
2705
2706 png_fp_set(state, PNG_FP_EXPONENT);
2707
2708 break;
2709
2710 /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
2711 goto PNG_FP_End; ** no sign in fraction */
2712
2713 /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
2714 goto PNG_FP_End; ** Because SAW_DOT is always set */
2715
2716 case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
2717 png_fp_add(state, type | PNG_FP_WAS_VALID);
2718 break;
2719
2720 case PNG_FP_FRACTION + PNG_FP_SAW_E:
2721 /* This is correct because the trailing '.' on an
2722 * integer is handled above - so we can only get here
2723 * with the sequence ".E" (with no preceding digits).
2724 */
2725 if ((state & PNG_FP_SAW_DIGIT) == 0)
2726 goto PNG_FP_End;
2727
2728 png_fp_set(state, PNG_FP_EXPONENT);
2729
2730 break;
2731
2732 case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
2733 if ((state & PNG_FP_SAW_ANY) != 0)
2734 goto PNG_FP_End; /* not a part of the number */
2735
2736 png_fp_add(state, PNG_FP_SAW_SIGN);
2737
2738 break;
2739
2740 /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
2741 goto PNG_FP_End; */
2742
2743 case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
2744 png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);
2745
2746 break;
2747
2748 /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
2749 goto PNG_FP_End; */
2750
2751 default: goto PNG_FP_End; /* I.e. break 2 */
2752 }
2753
2754 /* The character seems ok, continue. */
2755 ++i;
2756 }
2757
2758 PNG_FP_End:
2759 /* Here at the end, update the state and return the correct
2760 * return code.
2761 */
2762 *statep = state;
2763 *whereami = i;
2764
2765 return (state & PNG_FP_SAW_DIGIT) != 0;
2766 }
2767
2768
2769 /* The same but for a complete string. */
2770 int
2771 png_check_fp_string(png_const_charp string, png_size_t size)
2772 {
2773 int state=0;
2774 png_size_t char_index=0;
2775
2776 if (png_check_fp_number(string, size, &state, &char_index) != 0 &&
2777 (char_index == size || string[char_index] == 0))
2778 return state /* must be non-zero - see above */;
2779
2780 return 0; /* i.e. fail */
2781 }
2782 #endif /* pCAL || sCAL */
2783
2784 #ifdef PNG_sCAL_SUPPORTED
2785 # ifdef PNG_FLOATING_POINT_SUPPORTED
2786 /* Utility used below - a simple accurate power of ten from an integral
2787 * exponent.
2788 */
2789 static double
2790 png_pow10(int power)
2791 {
2792 int recip = 0;
2793 double d = 1;
2794
2795 /* Handle negative exponent with a reciprocal at the end because
2796 * 10 is exact whereas .1 is inexact in base 2
2797 */
2798 if (power < 0)
2799 {
2800 if (power < DBL_MIN_10_EXP) return 0;
2801 recip = 1, power = -power;
2802 }
2803
2804 if (power > 0)
2805 {
2806 /* Decompose power bitwise. */
2807 double mult = 10;
2808 do
2809 {
2810 if (power & 1) d *= mult;
2811 mult *= mult;
2812 power >>= 1;
2813 }
2814 while (power > 0);
2815
2816 if (recip != 0) d = 1/d;
2817 }
2818 /* else power is 0 and d is 1 */
2819
2820 return d;
2821 }
2822
2823 /* Function to format a floating point value in ASCII with a given
2824 * precision.
2825 */
2826 void /* PRIVATE */
2827 png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, png_size_t size,
2828 double fp, unsigned int precision)
2829 {
2830 /* We use standard functions from math.h, but not printf because
2831 * that would require stdio. The caller must supply a buffer of
2832 * sufficient size or we will png_error. The tests on size and
2833 * the space in ascii[] consumed are indicated below.
2834 */
2835 if (precision < 1)
2836 precision = DBL_DIG;
2837
2838 /* Enforce the limit of the implementation precision too. */
2839 if (precision > DBL_DIG+1)
2840 precision = DBL_DIG+1;
2841
2842 /* Basic sanity checks */
2843 if (size >= precision+5) /* See the requirements below. */
2844 {
2845 if (fp < 0)
2846 {
2847 fp = -fp;
2848 *ascii++ = 45; /* '-' PLUS 1 TOTAL 1 */
2849 --size;
2850 }
2851
2852 if (fp >= DBL_MIN && fp <= DBL_MAX)
2853 {
2854 int exp_b10; /* A base 10 exponent */
2855 double base; /* 10^exp_b10 */
2856
2857 /* First extract a base 10 exponent of the number,
2858 * the calculation below rounds down when converting
2859 * from base 2 to base 10 (multiply by log10(2) -
2860 * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
2861 * be increased. Note that the arithmetic shift
2862 * performs a floor() unlike C arithmetic - using a
2863 * C multiply would break the following for negative
2864 * exponents.
2865 */
2866 (void)frexp(fp, &exp_b10); /* exponent to base 2 */
2867
2868 exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */
2869
2870 /* Avoid underflow here. */
2871 base = png_pow10(exp_b10); /* May underflow */
2872
2873 while (base < DBL_MIN || base < fp)
2874 {
2875 /* And this may overflow. */
2876 double test = png_pow10(exp_b10+1);
2877
2878 if (test <= DBL_MAX)
2879 ++exp_b10, base = test;
2880
2881 else
2882 break;
2883 }
2884
2885 /* Normalize fp and correct exp_b10, after this fp is in the
2886 * range [.1,1) and exp_b10 is both the exponent and the digit
2887 * *before* which the decimal point should be inserted
2888 * (starting with 0 for the first digit). Note that this
2889 * works even if 10^exp_b10 is out of range because of the
2890 * test on DBL_MAX above.
2891 */
2892 fp /= base;
2893 while (fp >= 1) fp /= 10, ++exp_b10;
2894
2895 /* Because of the code above fp may, at this point, be
2896 * less than .1, this is ok because the code below can
2897 * handle the leading zeros this generates, so no attempt
2898 * is made to correct that here.
2899 */
2900
2901 {
2902 unsigned int czero, clead, cdigits;
2903 char exponent[10];
2904
2905 /* Allow up to two leading zeros - this will not lengthen
2906 * the number compared to using E-n.
2907 */
2908 if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */
2909 {
2910 czero = -exp_b10; /* PLUS 2 digits: TOTAL 3 */
2911 exp_b10 = 0; /* Dot added below before first output. */
2912 }
2913 else
2914 czero = 0; /* No zeros to add */
2915
2916 /* Generate the digit list, stripping trailing zeros and
2917 * inserting a '.' before a digit if the exponent is 0.
2918 */
2919 clead = czero; /* Count of leading zeros */
2920 cdigits = 0; /* Count of digits in list. */
2921
2922 do
2923 {
2924 double d;
2925
2926 fp *= 10;
2927 /* Use modf here, not floor and subtract, so that
2928 * the separation is done in one step. At the end
2929 * of the loop don't break the number into parts so
2930 * that the final digit is rounded.
2931 */
2932 if (cdigits+czero+1 < precision+clead)
2933 fp = modf(fp, &d);
2934
2935 else
2936 {
2937 d = floor(fp + .5);
2938
2939 if (d > 9)
2940 {
2941 /* Rounding up to 10, handle that here. */
2942 if (czero > 0)
2943 {
2944 --czero, d = 1;
2945 if (cdigits == 0) --clead;
2946 }
2947 else
2948 {
2949 while (cdigits > 0 && d > 9)
2950 {
2951 int ch = *--ascii;
2952
2953 if (exp_b10 != (-1))
2954 ++exp_b10;
2955
2956 else if (ch == 46)
2957 {
2958 ch = *--ascii, ++size;
2959 /* Advance exp_b10 to '1', so that the
2960 * decimal point happens after the
2961 * previous digit.
2962 */
2963 exp_b10 = 1;
2964 }
2965
2966 --cdigits;
2967 d = ch - 47; /* I.e. 1+(ch-48) */
2968 }
2969
2970 /* Did we reach the beginning? If so adjust the
2971 * exponent but take into account the leading
2972 * decimal point.
2973 */
2974 if (d > 9) /* cdigits == 0 */
2975 {
2976 if (exp_b10 == (-1))
2977 {
2978 /* Leading decimal point (plus zeros?), if
2979 * we lose the decimal point here it must
2980 * be reentered below.
2981 */
2982 int ch = *--ascii;
2983
2984 if (ch == 46)
2985 ++size, exp_b10 = 1;
2986
2987 /* Else lost a leading zero, so 'exp_b10' is
2988 * still ok at (-1)
2989 */
2990 }
2991 else
2992 ++exp_b10;
2993
2994 /* In all cases we output a '1' */
2995 d = 1;
2996 }
2997 }
2998 }
2999 fp = 0; /* Guarantees termination below. */
3000 }
3001
3002 if (d == 0)
3003 {
3004 ++czero;
3005 if (cdigits == 0) ++clead;
3006 }
3007 else
3008 {
3009 /* Included embedded zeros in the digit count. */
3010 cdigits += czero - clead;
3011 clead = 0;
3012
3013 while (czero > 0)
3014 {
3015 /* exp_b10 == (-1) means we just output the decimal
3016 * place - after the DP don't adjust 'exp_b10' any
3017 * more!
3018 */
3019 if (exp_b10 != (-1))
3020 {
3021 if (exp_b10 == 0) *ascii++ = 46, --size;
3022 /* PLUS 1: TOTAL 4 */
3023 --exp_b10;
3024 }
3025 *ascii++ = 48, --czero;
3026 }
3027
3028 if (exp_b10 != (-1))
3029 {
3030 if (exp_b10 == 0)
3031 *ascii++ = 46, --size; /* counted above */
3032
3033 --exp_b10;
3034 }
3035 *ascii++ = (char)(48 + (int)d), ++cdigits;
3036 }
3037 }
3038 while (cdigits+czero < precision+clead && fp > DBL_MIN);
3039
3040 /* The total output count (max) is now 4+precision */
3041
3042 /* Check for an exponent, if we don't need one we are
3043 * done and just need to terminate the string. At
3044 * this point exp_b10==(-1) is effectively if flag - it got
3045 * to '-1' because of the decrement after outputting
3046 * the decimal point above (the exponent required is
3047 * *not* -1!)
3048 */
3049 if (exp_b10 >= (-1) && exp_b10 <= 2)
3050 {
3051 /* The following only happens if we didn't output the
3052 * leading zeros above for negative exponent, so this
3053 * doesn't add to the digit requirement. Note that the
3054 * two zeros here can only be output if the two leading
3055 * zeros were *not* output, so this doesn't increase
3056 * the output count.
3057 */
3058 while (--exp_b10 >= 0) *ascii++ = 48;
3059
3060 *ascii = 0;
3061
3062 /* Total buffer requirement (including the '\0') is
3063 * 5+precision - see check at the start.
3064 */
3065 return;
3066 }
3067
3068 /* Here if an exponent is required, adjust size for
3069 * the digits we output but did not count. The total
3070 * digit output here so far is at most 1+precision - no
3071 * decimal point and no leading or trailing zeros have
3072 * been output.
3073 */
3074 size -= cdigits;
3075
3076 *ascii++ = 69, --size; /* 'E': PLUS 1 TOTAL 2+precision */
3077
3078 /* The following use of an unsigned temporary avoids ambiguities in
3079 * the signed arithmetic on exp_b10 and permits GCC at least to do
3080 * better optimization.
3081 */
3082 {
3083 unsigned int uexp_b10;
3084
3085 if (exp_b10 < 0)
3086 {
3087 *ascii++ = 45, --size; /* '-': PLUS 1 TOTAL 3+precision */
3088 uexp_b10 = -exp_b10;
3089 }
3090
3091 else
3092 uexp_b10 = exp_b10;
3093
3094 cdigits = 0;
3095
3096 while (uexp_b10 > 0)
3097 {
3098 exponent[cdigits++] = (char)(48 + uexp_b10 % 10);
3099 uexp_b10 /= 10;
3100 }
3101 }
3102
3103 /* Need another size check here for the exponent digits, so
3104 * this need not be considered above.
3105 */
3106 if (size > cdigits)
3107 {
3108 while (cdigits > 0) *ascii++ = exponent[--cdigits];
3109
3110 *ascii = 0;
3111
3112 return;
3113 }
3114 }
3115 }
3116 else if (!(fp >= DBL_MIN))
3117 {
3118 *ascii++ = 48; /* '0' */
3119 *ascii = 0;
3120 return;
3121 }
3122 else
3123 {
3124 *ascii++ = 105; /* 'i' */
3125 *ascii++ = 110; /* 'n' */
3126 *ascii++ = 102; /* 'f' */
3127 *ascii = 0;
3128 return;
3129 }
3130 }
3131
3132 /* Here on buffer too small. */
3133 png_error(png_ptr, "ASCII conversion buffer too small");
3134 }
3135
3136 # endif /* FLOATING_POINT */
3137
3138 # ifdef PNG_FIXED_POINT_SUPPORTED
3139 /* Function to format a fixed point value in ASCII.
3140 */
3141 void /* PRIVATE */
3142 png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
3143 png_size_t size, png_fixed_point fp)
3144 {
3145 /* Require space for 10 decimal digits, a decimal point, a minus sign and a
3146 * trailing \0, 13 characters:
3147 */
3148 if (size > 12)
3149 {
3150 png_uint_32 num;
3151
3152 /* Avoid overflow here on the minimum integer. */
3153 if (fp < 0)
3154 *ascii++ = 45, num = -fp;
3155 else
3156 num = fp;
3157
3158 if (num <= 0x80000000) /* else overflowed */
3159 {
3160 unsigned int ndigits = 0, first = 16 /* flag value */;
3161 char digits[10];
3162
3163 while (num)
3164 {
3165 /* Split the low digit off num: */
3166 unsigned int tmp = num/10;
3167 num -= tmp*10;
3168 digits[ndigits++] = (char)(48 + num);
3169 /* Record the first non-zero digit, note that this is a number
3170 * starting at 1, it's not actually the array index.
3171 */
3172 if (first == 16 && num > 0)
3173 first = ndigits;
3174 num = tmp;
3175 }
3176
3177 if (ndigits > 0)
3178 {
3179 while (ndigits > 5) *ascii++ = digits[--ndigits];
3180 /* The remaining digits are fractional digits, ndigits is '5' or
3181 * smaller at this point. It is certainly not zero. Check for a
3182 * non-zero fractional digit:
3183 */
3184 if (first <= 5)
3185 {
3186 unsigned int i;
3187 *ascii++ = 46; /* decimal point */
3188 /* ndigits may be <5 for small numbers, output leading zeros
3189 * then ndigits digits to first:
3190 */
3191 i = 5;
3192 while (ndigits < i) *ascii++ = 48, --i;
3193 while (ndigits >= first) *ascii++ = digits[--ndigits];
3194 /* Don't output the trailing zeros! */
3195 }
3196 }
3197 else
3198 *ascii++ = 48;
3199
3200 /* And null terminate the string: */
3201 *ascii = 0;
3202 return;
3203 }
3204 }
3205
3206 /* Here on buffer too small. */
3207 png_error(png_ptr, "ASCII conversion buffer too small");
3208 }
3209 # endif /* FIXED_POINT */
3210 #endif /* SCAL */
3211
3212 #if defined(PNG_FLOATING_POINT_SUPPORTED) && \
3213 !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
3214 (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
3215 defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
3216 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
3217 (defined(PNG_sCAL_SUPPORTED) && \
3218 defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
3219 png_fixed_point
3220 png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
3221 {
3222 double r = floor(100000 * fp + .5);
3223
3224 if (r > 2147483647. || r < -2147483648.)
3225 png_fixed_error(png_ptr, text);
3226
3227 # ifndef PNG_ERROR_TEXT_SUPPORTED
3228 PNG_UNUSED(text)
3229 # endif
3230
3231 return (png_fixed_point)r;
3232 }
3233 #endif
3234
3235 #if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\
3236 defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
3237 /* muldiv functions */
3238 /* This API takes signed arguments and rounds the result to the nearest
3239 * integer (or, for a fixed point number - the standard argument - to
3240 * the nearest .00001). Overflow and divide by zero are signalled in
3241 * the result, a boolean - true on success, false on overflow.
3242 */
3243 int
3244 png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
3245 png_int_32 divisor)
3246 {
3247 /* Return a * times / divisor, rounded. */
3248 if (divisor != 0)