2 /* png.c - location for general purpose libpng functions
4 * Last changed in libpng 1.6.18 [July 23, 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.)
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
16 /* Generate a compiler error if there is an old png.h in the search path. */
17 typedef png_libpng_version_1_6_18 Your_png_h_is_not_version_1_6_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.
25 #ifdef PNG_READ_SUPPORTED
27 png_set_sig_bytes(png_structrp png_ptr
, int num_bytes
)
29 png_debug(1, "in png_set_sig_bytes");
35 png_error(png_ptr
, "Too many bytes for PNG signature");
37 png_ptr
->sig_bytes
= (png_byte
)((num_bytes
< 0 ? 0 : num_bytes
) & 0xff);
40 /* Checks whether the supplied bytes match the PNG signature. We allow
41 * checking less than the full 8-byte signature so that those apps that
42 * already read the first few bytes of a file to determine the file type
43 * can simply check the remaining bytes for extra assurance. Returns
44 * an integer less than, equal to, or greater than zero if sig is found,
45 * respectively, to be less than, to match, or be greater than the correct
46 * PNG signature (this is the same behavior as strcmp, memcmp, etc).
49 png_sig_cmp(png_const_bytep sig
, png_size_t start
, png_size_t num_to_check
)
51 png_byte png_signature
[8] = {137, 80, 78, 71, 13, 10, 26, 10};
56 else if (num_to_check
< 1)
62 if (start
+ num_to_check
> 8)
63 num_to_check
= 8 - start
;
65 return ((int)(memcmp(&sig
[start
], &png_signature
[start
], num_to_check
)));
70 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
71 /* Function to allocate memory for zlib */
72 PNG_FUNCTION(voidpf
/* PRIVATE */,
73 png_zalloc
,(voidpf png_ptr
, uInt items
, uInt size
),PNG_ALLOCATED
)
75 png_alloc_size_t num_bytes
= size
;
80 if (items
>= (~(png_alloc_size_t
)0)/size
)
82 png_warning (png_voidcast(png_structrp
, png_ptr
),
83 "Potential overflow in png_zalloc()");
88 return png_malloc_warn(png_voidcast(png_structrp
, png_ptr
), num_bytes
);
91 /* Function to free memory for zlib */
93 png_zfree(voidpf png_ptr
, voidpf ptr
)
95 png_free(png_voidcast(png_const_structrp
,png_ptr
), ptr
);
98 /* Reset the CRC variable to 32 bits of 1's. Care must be taken
99 * in case CRC is > 32 bits to leave the top bits 0.
102 png_reset_crc(png_structrp png_ptr
)
104 /* The cast is safe because the crc is a 32-bit value. */
105 png_ptr
->crc
= (png_uint_32
)crc32(0, Z_NULL
, 0);
108 /* Calculate the CRC over a section of data. We can only pass as
109 * much data to this routine as the largest single buffer size. We
110 * also check that this data will actually be used before going to the
111 * trouble of calculating it.
114 png_calculate_crc(png_structrp png_ptr
, png_const_bytep ptr
, png_size_t length
)
118 if (PNG_CHUNK_ANCILLARY(png_ptr
->chunk_name
) != 0)
120 if ((png_ptr
->flags
& PNG_FLAG_CRC_ANCILLARY_MASK
) ==
121 (PNG_FLAG_CRC_ANCILLARY_USE
| PNG_FLAG_CRC_ANCILLARY_NOWARN
))
127 if ((png_ptr
->flags
& PNG_FLAG_CRC_CRITICAL_IGNORE
) != 0)
131 /* 'uLong' is defined in zlib.h as unsigned long; this means that on some
132 * systems it is a 64-bit value. crc32, however, returns 32 bits so the
133 * following cast is safe. 'uInt' may be no more than 16 bits, so it is
134 * necessary to perform a loop here.
136 if (need_crc
!= 0 && length
> 0)
138 uLong crc
= png_ptr
->crc
; /* Should never issue a warning */
142 uInt safe_length
= (uInt
)length
;
144 if (safe_length
== 0)
145 safe_length
= (uInt
)-1; /* evil, but safe */
148 crc
= crc32(crc
, ptr
, safe_length
);
150 /* The following should never issue compiler warnings; if they do the
151 * target system has characteristics that will probably violate other
152 * assumptions within the libpng code.
155 length
-= safe_length
;
159 /* And the following is always safe because the crc is only 32 bits. */
160 png_ptr
->crc
= (png_uint_32
)crc
;
164 /* Check a user supplied version number, called from both read and write
165 * functions that create a png_struct.
168 png_user_version_check(png_structrp png_ptr
, png_const_charp user_png_ver
)
170 /* Libpng versions 1.0.0 and later are binary compatible if the version
171 * string matches through the second '.'; we must recompile any
172 * applications that use any older library version.
175 if (user_png_ver
!= NULL
)
183 if (user_png_ver
[i
] != PNG_LIBPNG_VER_STRING
[i
])
184 png_ptr
->flags
|= PNG_FLAG_LIBRARY_MISMATCH
;
185 if (user_png_ver
[i
] == '.')
187 } while (found_dots
< 2 && user_png_ver
[i
] != 0 &&
188 PNG_LIBPNG_VER_STRING
[i
] != 0);
192 png_ptr
->flags
|= PNG_FLAG_LIBRARY_MISMATCH
;
194 if ((png_ptr
->flags
& PNG_FLAG_LIBRARY_MISMATCH
) != 0)
196 #ifdef PNG_WARNINGS_SUPPORTED
200 pos
= png_safecat(m
, (sizeof m
), pos
,
201 "Application built with libpng-");
202 pos
= png_safecat(m
, (sizeof m
), pos
, user_png_ver
);
203 pos
= png_safecat(m
, (sizeof m
), pos
, " but running with ");
204 pos
= png_safecat(m
, (sizeof m
), pos
, PNG_LIBPNG_VER_STRING
);
207 png_warning(png_ptr
, m
);
210 #ifdef PNG_ERROR_NUMBERS_SUPPORTED
217 /* Success return. */
221 /* Generic function to create a png_struct for either read or write - this
222 * contains the common initialization.
224 PNG_FUNCTION(png_structp
/* PRIVATE */,
225 png_create_png_struct
,(png_const_charp user_png_ver
, png_voidp error_ptr
,
226 png_error_ptr error_fn
, png_error_ptr warn_fn
, png_voidp mem_ptr
,
227 png_malloc_ptr malloc_fn
, png_free_ptr free_fn
),PNG_ALLOCATED
)
229 png_struct create_struct
;
230 # ifdef PNG_SETJMP_SUPPORTED
231 jmp_buf create_jmp_buf
;
234 /* This temporary stack-allocated structure is used to provide a place to
235 * build enough context to allow the user provided memory allocator (if any)
238 memset(&create_struct
, 0, (sizeof create_struct
));
240 /* Added at libpng-1.2.6 */
241 # ifdef PNG_USER_LIMITS_SUPPORTED
242 create_struct
.user_width_max
= PNG_USER_WIDTH_MAX
;
243 create_struct
.user_height_max
= PNG_USER_HEIGHT_MAX
;
245 # ifdef PNG_USER_CHUNK_CACHE_MAX
246 /* Added at libpng-1.2.43 and 1.4.0 */
247 create_struct
.user_chunk_cache_max
= PNG_USER_CHUNK_CACHE_MAX
;
250 # ifdef PNG_USER_CHUNK_MALLOC_MAX
251 /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
252 * in png_struct regardless.
254 create_struct
.user_chunk_malloc_max
= PNG_USER_CHUNK_MALLOC_MAX
;
258 /* The following two API calls simply set fields in png_struct, so it is safe
259 * to do them now even though error handling is not yet set up.
261 # ifdef PNG_USER_MEM_SUPPORTED
262 png_set_mem_fn(&create_struct
, mem_ptr
, malloc_fn
, free_fn
);
265 PNG_UNUSED(malloc_fn
)
269 /* (*error_fn) can return control to the caller after the error_ptr is set,
270 * this will result in a memory leak unless the error_fn does something
271 * extremely sophisticated. The design lacks merit but is implicit in the
274 png_set_error_fn(&create_struct
, error_ptr
, error_fn
, warn_fn
);
276 # ifdef PNG_SETJMP_SUPPORTED
277 if (!setjmp(create_jmp_buf
))
280 # ifdef PNG_SETJMP_SUPPORTED
281 /* Temporarily fake out the longjmp information until we have
282 * successfully completed this function. This only works if we have
283 * setjmp() support compiled in, but it is safe - this stuff should
286 create_struct
.jmp_buf_ptr
= &create_jmp_buf
;
287 create_struct
.jmp_buf_size
= 0; /*stack allocation*/
288 create_struct
.longjmp_fn
= longjmp
;
290 /* Call the general version checker (shared with read and write code):
292 if (png_user_version_check(&create_struct
, user_png_ver
) != 0)
294 png_structrp png_ptr
= png_voidcast(png_structrp
,
295 png_malloc_warn(&create_struct
, (sizeof *png_ptr
)));
299 /* png_ptr->zstream holds a back-pointer to the png_struct, so
300 * this can only be done now:
302 create_struct
.zstream
.zalloc
= png_zalloc
;
303 create_struct
.zstream
.zfree
= png_zfree
;
304 create_struct
.zstream
.opaque
= png_ptr
;
306 # ifdef PNG_SETJMP_SUPPORTED
307 /* Eliminate the local error handling: */
308 create_struct
.jmp_buf_ptr
= NULL
;
309 create_struct
.jmp_buf_size
= 0;
310 create_struct
.longjmp_fn
= 0;
313 *png_ptr
= create_struct
;
315 /* This is the successful return point */
321 /* A longjmp because of a bug in the application storage allocator or a
322 * simple failure to allocate the png_struct.
327 /* Allocate the memory for an info_struct for the application. */
328 PNG_FUNCTION(png_infop
,PNGAPI
329 png_create_info_struct
,(png_const_structrp png_ptr
),PNG_ALLOCATED
)
333 png_debug(1, "in png_create_info_struct");
338 /* Use the internal API that does not (or at least should not) error out, so
339 * that this call always returns ok. The application typically sets up the
340 * error handling *after* creating the info_struct because this is the way it
341 * has always been done in 'example.c'.
343 info_ptr
= png_voidcast(png_inforp
, png_malloc_base(png_ptr
,
344 (sizeof *info_ptr
)));
346 if (info_ptr
!= NULL
)
347 memset(info_ptr
, 0, (sizeof *info_ptr
));
352 /* This function frees the memory associated with a single info struct.
353 * Normally, one would use either png_destroy_read_struct() or
354 * png_destroy_write_struct() to free an info struct, but this may be
355 * useful for some applications. From libpng 1.6.0 this function is also used
356 * internally to implement the png_info release part of the 'struct' destroy
357 * APIs. This ensures that all possible approaches free the same data (all of
361 png_destroy_info_struct(png_const_structrp png_ptr
, png_infopp info_ptr_ptr
)
363 png_inforp info_ptr
= NULL
;
365 png_debug(1, "in png_destroy_info_struct");
370 if (info_ptr_ptr
!= NULL
)
371 info_ptr
= *info_ptr_ptr
;
373 if (info_ptr
!= NULL
)
375 /* Do this first in case of an error below; if the app implements its own
376 * memory management this can lead to png_free calling png_error, which
377 * will abort this routine and return control to the app error handler.
378 * An infinite loop may result if it then tries to free the same info
381 *info_ptr_ptr
= NULL
;
383 png_free_data(png_ptr
, info_ptr
, PNG_FREE_ALL
, -1);
384 memset(info_ptr
, 0, (sizeof *info_ptr
));
385 png_free(png_ptr
, info_ptr
);
389 /* Initialize the info structure. This is now an internal function (0.89)
390 * and applications using it are urged to use png_create_info_struct()
391 * instead. Use deprecated in 1.6.0, internal use removed (used internally it
394 * NOTE: it is almost inconceivable that this API is used because it bypasses
395 * the user-memory mechanism and the user error handling/warning mechanisms in
396 * those cases where it does anything other than a memset.
398 PNG_FUNCTION(void,PNGAPI
399 png_info_init_3
,(png_infopp ptr_ptr
, png_size_t png_info_struct_size
),
402 png_inforp info_ptr
= *ptr_ptr
;
404 png_debug(1, "in png_info_init_3");
406 if (info_ptr
== NULL
)
409 if ((sizeof (png_info
)) > png_info_struct_size
)
412 /* The following line is why this API should not be used: */
414 info_ptr
= png_voidcast(png_inforp
, png_malloc_base(NULL
,
415 (sizeof *info_ptr
)));
419 /* Set everything to 0 */
420 memset(info_ptr
, 0, (sizeof *info_ptr
));
423 /* The following API is not called internally */
425 png_data_freer(png_const_structrp png_ptr
, png_inforp info_ptr
,
426 int freer
, png_uint_32 mask
)
428 png_debug(1, "in png_data_freer");
430 if (png_ptr
== NULL
|| info_ptr
== NULL
)
433 if (freer
== PNG_DESTROY_WILL_FREE_DATA
)
434 info_ptr
->free_me
|= mask
;
436 else if (freer
== PNG_USER_WILL_FREE_DATA
)
437 info_ptr
->free_me
&= ~mask
;
440 png_error(png_ptr
, "Unknown freer parameter in png_data_freer");
444 png_free_data(png_const_structrp png_ptr
, png_inforp info_ptr
, png_uint_32 mask
,
447 png_debug(1, "in png_free_data");
449 if (png_ptr
== NULL
|| info_ptr
== NULL
)
452 #ifdef PNG_TEXT_SUPPORTED
453 /* Free text item num or (if num == -1) all text items */
454 if (info_ptr
->text
!= 0 &&
455 ((mask
& PNG_FREE_TEXT
) & info_ptr
->free_me
) != 0)
459 png_free(png_ptr
, info_ptr
->text
[num
].key
);
460 info_ptr
->text
[num
].key
= NULL
;
467 for (i
= 0; i
< info_ptr
->num_text
; i
++)
468 png_free(png_ptr
, info_ptr
->text
[i
].key
);
470 png_free(png_ptr
, info_ptr
->text
);
471 info_ptr
->text
= NULL
;
472 info_ptr
->num_text
= 0;
477 #ifdef PNG_tRNS_SUPPORTED
478 /* Free any tRNS entry */
479 if (((mask
& PNG_FREE_TRNS
) & info_ptr
->free_me
) != 0)
481 info_ptr
->valid
&= ~PNG_INFO_tRNS
;
482 png_free(png_ptr
, info_ptr
->trans_alpha
);
483 info_ptr
->trans_alpha
= NULL
;
484 info_ptr
->num_trans
= 0;
488 #ifdef PNG_sCAL_SUPPORTED
489 /* Free any sCAL entry */
490 if (((mask
& PNG_FREE_SCAL
) & info_ptr
->free_me
) != 0)
492 png_free(png_ptr
, info_ptr
->scal_s_width
);
493 png_free(png_ptr
, info_ptr
->scal_s_height
);
494 info_ptr
->scal_s_width
= NULL
;
495 info_ptr
->scal_s_height
= NULL
;
496 info_ptr
->valid
&= ~PNG_INFO_sCAL
;
500 #ifdef PNG_pCAL_SUPPORTED
501 /* Free any pCAL entry */
502 if (((mask
& PNG_FREE_PCAL
) & info_ptr
->free_me
) != 0)
504 png_free(png_ptr
, info_ptr
->pcal_purpose
);
505 png_free(png_ptr
, info_ptr
->pcal_units
);
506 info_ptr
->pcal_purpose
= NULL
;
507 info_ptr
->pcal_units
= NULL
;
509 if (info_ptr
->pcal_params
!= NULL
)
513 for (i
= 0; i
< info_ptr
->pcal_nparams
; i
++)
514 png_free(png_ptr
, info_ptr
->pcal_params
[i
]);
516 png_free(png_ptr
, info_ptr
->pcal_params
);
517 info_ptr
->pcal_params
= NULL
;
519 info_ptr
->valid
&= ~PNG_INFO_pCAL
;
523 #ifdef PNG_iCCP_SUPPORTED
524 /* Free any profile entry */
525 if (((mask
& PNG_FREE_ICCP
) & info_ptr
->free_me
) != 0)
527 png_free(png_ptr
, info_ptr
->iccp_name
);
528 png_free(png_ptr
, info_ptr
->iccp_profile
);
529 info_ptr
->iccp_name
= NULL
;
530 info_ptr
->iccp_profile
= NULL
;
531 info_ptr
->valid
&= ~PNG_INFO_iCCP
;
535 #ifdef PNG_sPLT_SUPPORTED
536 /* Free a given sPLT entry, or (if num == -1) all sPLT entries */
537 if (info_ptr
->splt_palettes
!= 0 &&
538 ((mask
& PNG_FREE_SPLT
) & info_ptr
->free_me
) != 0)
542 png_free(png_ptr
, info_ptr
->splt_palettes
[num
].name
);
543 png_free(png_ptr
, info_ptr
->splt_palettes
[num
].entries
);
544 info_ptr
->splt_palettes
[num
].name
= NULL
;
545 info_ptr
->splt_palettes
[num
].entries
= NULL
;
552 for (i
= 0; i
< info_ptr
->splt_palettes_num
; i
++)
554 png_free(png_ptr
, info_ptr
->splt_palettes
[i
].name
);
555 png_free(png_ptr
, info_ptr
->splt_palettes
[i
].entries
);
558 png_free(png_ptr
, info_ptr
->splt_palettes
);
559 info_ptr
->splt_palettes
= NULL
;
560 info_ptr
->splt_palettes_num
= 0;
561 info_ptr
->valid
&= ~PNG_INFO_sPLT
;
566 #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
567 if (info_ptr
->unknown_chunks
!= 0 &&
568 ((mask
& PNG_FREE_UNKN
) & info_ptr
->free_me
) != 0)
572 png_free(png_ptr
, info_ptr
->unknown_chunks
[num
].data
);
573 info_ptr
->unknown_chunks
[num
].data
= NULL
;
580 for (i
= 0; i
< info_ptr
->unknown_chunks_num
; i
++)
581 png_free(png_ptr
, info_ptr
->unknown_chunks
[i
].data
);
583 png_free(png_ptr
, info_ptr
->unknown_chunks
);
584 info_ptr
->unknown_chunks
= NULL
;
585 info_ptr
->unknown_chunks_num
= 0;
590 #ifdef PNG_hIST_SUPPORTED
591 /* Free any hIST entry */
592 if (((mask
& PNG_FREE_HIST
) & info_ptr
->free_me
) != 0)
594 png_free(png_ptr
, info_ptr
->hist
);
595 info_ptr
->hist
= NULL
;
596 info_ptr
->valid
&= ~PNG_INFO_hIST
;
600 /* Free any PLTE entry that was internally allocated */
601 if (((mask
& PNG_FREE_PLTE
) & info_ptr
->free_me
) != 0)
603 png_free(png_ptr
, info_ptr
->palette
);
604 info_ptr
->palette
= NULL
;
605 info_ptr
->valid
&= ~PNG_INFO_PLTE
;
606 info_ptr
->num_palette
= 0;
609 #ifdef PNG_INFO_IMAGE_SUPPORTED
610 /* Free any image bits attached to the info structure */
611 if (((mask
& PNG_FREE_ROWS
) & info_ptr
->free_me
) != 0)
613 if (info_ptr
->row_pointers
!= 0)
616 for (row
= 0; row
< info_ptr
->height
; row
++)
617 png_free(png_ptr
, info_ptr
->row_pointers
[row
]);
619 png_free(png_ptr
, info_ptr
->row_pointers
);
620 info_ptr
->row_pointers
= NULL
;
622 info_ptr
->valid
&= ~PNG_INFO_IDAT
;
627 mask
&= ~PNG_FREE_MUL
;
629 info_ptr
->free_me
&= ~mask
;
631 #endif /* READ || WRITE */
633 /* This function returns a pointer to the io_ptr associated with the user
634 * functions. The application should free any memory associated with this
635 * pointer before png_write_destroy() or png_read_destroy() are called.
638 png_get_io_ptr(png_const_structrp png_ptr
)
643 return (png_ptr
->io_ptr
);
646 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
647 # ifdef PNG_STDIO_SUPPORTED
648 /* Initialize the default input/output functions for the PNG file. If you
649 * use your own read or write routines, you can call either png_set_read_fn()
650 * or png_set_write_fn() instead of png_init_io(). If you have defined
651 * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
652 * function of your own because "FILE *" isn't necessarily available.
655 png_init_io(png_structrp png_ptr
, png_FILE_p fp
)
657 png_debug(1, "in png_init_io");
662 png_ptr
->io_ptr
= (png_voidp
)fp
;
666 # ifdef PNG_SAVE_INT_32_SUPPORTED
667 /* The png_save_int_32 function assumes integers are stored in two's
668 * complement format. If this isn't the case, then this routine needs to
669 * be modified to write data in two's complement format. Note that,
670 * the following works correctly even if png_int_32 has more than 32 bits
671 * (compare the more complex code required on read for sign extension.)
674 png_save_int_32(png_bytep buf
, png_int_32 i
)
676 buf
[0] = (png_byte
)((i
>> 24) & 0xff);
677 buf
[1] = (png_byte
)((i
>> 16) & 0xff);
678 buf
[2] = (png_byte
)((i
>> 8) & 0xff);
679 buf
[3] = (png_byte
)(i
& 0xff);
683 # ifdef PNG_TIME_RFC1123_SUPPORTED
684 /* Convert the supplied time into an RFC 1123 string suitable for use in
685 * a "Creation Time" or other text-based time string.
688 png_convert_to_rfc1123_buffer(char out
[29], png_const_timep ptime
)
690 static PNG_CONST
char short_months
[12][4] =
691 {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
692 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
697 if (ptime
->year
> 9999 /* RFC1123 limitation */ ||
698 ptime
->month
== 0 || ptime
->month
> 12 ||
699 ptime
->day
== 0 || ptime
->day
> 31 ||
700 ptime
->hour
> 23 || ptime
->minute
> 59 ||
706 char number_buf
[5]; /* enough for a four-digit year */
708 # define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))
709 # define APPEND_NUMBER(format, value)\
710 APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
711 # define APPEND(ch) if (pos < 28) out[pos++] = (ch)
713 APPEND_NUMBER(PNG_NUMBER_FORMAT_u
, (unsigned)ptime
->day
);
715 APPEND_STRING(short_months
[(ptime
->month
- 1)]);
717 APPEND_NUMBER(PNG_NUMBER_FORMAT_u
, ptime
->year
);
719 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u
, (unsigned)ptime
->hour
);
721 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u
, (unsigned)ptime
->minute
);
723 APPEND_NUMBER(PNG_NUMBER_FORMAT_02u
, (unsigned)ptime
->second
);
724 APPEND_STRING(" +0000"); /* This reliably terminates the buffer */
727 # undef APPEND_NUMBER
728 # undef APPEND_STRING
734 # if PNG_LIBPNG_VER < 10700
735 /* To do: remove the following from libpng-1.7 */
736 /* Original API that uses a private buffer in png_struct.
737 * Deprecated because it causes png_struct to carry a spurious temporary
738 * buffer (png_struct::time_buffer), better to have the caller pass this in.
740 png_const_charp PNGAPI
741 png_convert_to_rfc1123(png_structrp png_ptr
, png_const_timep ptime
)
745 /* The only failure above if png_ptr != NULL is from an invalid ptime */
746 if (png_convert_to_rfc1123_buffer(png_ptr
->time_buffer
, ptime
) == 0)
747 png_warning(png_ptr
, "Ignoring invalid time value");
750 return png_ptr
->time_buffer
;
755 # endif /* LIBPNG_VER < 10700 */
756 # endif /* TIME_RFC1123 */
758 #endif /* READ || WRITE */
760 png_const_charp PNGAPI
761 png_get_copyright(png_const_structrp png_ptr
)
763 PNG_UNUSED(png_ptr
) /* Silence compiler warning about unused png_ptr */
764 #ifdef PNG_STRING_COPYRIGHT
765 return PNG_STRING_COPYRIGHT
768 return PNG_STRING_NEWLINE \
769 "libpng version 1.6.18 - July 23, 2015" PNG_STRING_NEWLINE \
770 "Copyright (c) 1998-2015 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
771 "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
772 "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
775 return "libpng version 1.6.18 - July 23, 2015\
776 Copyright (c) 1998-2015 Glenn Randers-Pehrson\
777 Copyright (c) 1996-1997 Andreas Dilger\
778 Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
783 /* The following return the library version as a short string in the
784 * format 1.0.0 through 99.99.99zz. To get the version of *.h files
785 * used with your application, print out PNG_LIBPNG_VER_STRING, which
786 * is defined in png.h.
787 * Note: now there is no difference between png_get_libpng_ver() and
788 * png_get_header_ver(). Due to the version_nn_nn_nn typedef guard,
789 * it is guaranteed that png.c uses the correct version of png.h.
791 png_const_charp PNGAPI
792 png_get_libpng_ver(png_const_structrp png_ptr
)
794 /* Version of *.c files used when building libpng */
795 return png_get_header_ver(png_ptr
);
798 png_const_charp PNGAPI
799 png_get_header_ver(png_const_structrp png_ptr
)
801 /* Version of *.h files used when building libpng */
802 PNG_UNUSED(png_ptr
) /* Silence compiler warning about unused png_ptr */
803 return PNG_LIBPNG_VER_STRING
;
806 png_const_charp PNGAPI
807 png_get_header_version(png_const_structrp png_ptr
)
809 /* Returns longer string containing both version and date */
810 PNG_UNUSED(png_ptr
) /* Silence compiler warning about unused png_ptr */
812 return PNG_HEADER_VERSION_STRING
813 # ifndef PNG_READ_SUPPORTED
818 return PNG_HEADER_VERSION_STRING
;
822 #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
823 /* NOTE: this routine is not used internally! */
824 /* Build a grayscale palette. Palette is assumed to be 1 << bit_depth
825 * large of png_color. This lets grayscale images be treated as
826 * paletted. Most useful for gamma correction and simplification
827 * of code. This API is not used internally.
830 png_build_grayscale_palette(int bit_depth
, png_colorp palette
)
837 png_debug(1, "in png_do_build_grayscale_palette");
870 for (i
= 0, v
= 0; i
< num_palette
; i
++, v
+= color_inc
)
872 palette
[i
].red
= (png_byte
)(v
& 0xff);
873 palette
[i
].green
= (png_byte
)(v
& 0xff);
874 palette
[i
].blue
= (png_byte
)(v
& 0xff);
879 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
881 png_handle_as_unknown(png_const_structrp png_ptr
, png_const_bytep chunk_name
)
883 /* Check chunk_name and return "keep" value if it's on the list, else 0 */
884 png_const_bytep p
, p_end
;
886 if (png_ptr
== NULL
|| chunk_name
== NULL
|| png_ptr
->num_chunk_list
== 0)
887 return PNG_HANDLE_CHUNK_AS_DEFAULT
;
889 p_end
= png_ptr
->chunk_list
;
890 p
= p_end
+ png_ptr
->num_chunk_list
*5; /* beyond end */
892 /* The code is the fifth byte after each four byte string. Historically this
893 * code was always searched from the end of the list, this is no longer
894 * necessary because the 'set' routine handles duplicate entries correcty.
896 do /* num_chunk_list > 0, so at least one */
900 if (memcmp(chunk_name
, p
, 4) == 0)
905 /* This means that known chunks should be processed and unknown chunks should
906 * be handled according to the value of png_ptr->unknown_default; this can be
907 * confusing because, as a result, there are two levels of defaulting for
910 return PNG_HANDLE_CHUNK_AS_DEFAULT
;
913 #if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
914 defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
916 png_chunk_unknown_handling(png_const_structrp png_ptr
, png_uint_32 chunk_name
)
918 png_byte chunk_string
[5];
920 PNG_CSTRING_FROM_CHUNK(chunk_string
, chunk_name
);
921 return png_handle_as_unknown(png_ptr
, chunk_string
);
923 #endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */
924 #endif /* SET_UNKNOWN_CHUNKS */
926 #ifdef PNG_READ_SUPPORTED
927 /* This function, added to libpng-1.0.6g, is untested. */
929 png_reset_zstream(png_structrp png_ptr
)
932 return Z_STREAM_ERROR
;
934 /* WARNING: this resets the window bits to the maximum! */
935 return (inflateReset(&png_ptr
->zstream
));
939 /* This function was added to libpng-1.0.7 */
941 png_access_version_number(void)
943 /* Version of *.c files used when building libpng */
944 return((png_uint_32
)PNG_LIBPNG_VER
);
947 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
948 /* Ensure that png_ptr->zstream.msg holds some appropriate error message string.
949 * If it doesn't 'ret' is used to set it to something appropriate, even in cases
950 * like Z_OK or Z_STREAM_END where the error code is apparently a success code.
953 png_zstream_error(png_structrp png_ptr
, int ret
)
955 /* Translate 'ret' into an appropriate error string, priority is given to the
956 * one in zstream if set. This always returns a string, even in cases like
957 * Z_OK or Z_STREAM_END where the error code is a success code.
959 if (png_ptr
->zstream
.msg
== NULL
) switch (ret
)
963 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("unexpected zlib return code");
968 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("unexpected end of LZ stream");
972 /* This means the deflate stream did not have a dictionary; this
973 * indicates a bogus PNG.
975 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("missing LZ dictionary");
979 /* gz APIs only: should not happen */
980 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("zlib IO error");
984 /* internal libpng error */
985 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("bad parameters to zlib");
989 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("damaged LZ stream");
993 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("insufficient memory");
997 /* End of input or output; not a problem if the caller is doing
998 * incremental read or write.
1000 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("truncated");
1003 case Z_VERSION_ERROR
:
1004 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("unsupported zlib version");
1007 case PNG_UNEXPECTED_ZLIB_RETURN
:
1008 /* Compile errors here mean that zlib now uses the value co-opted in
1009 * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above
1010 * and change pngpriv.h. Note that this message is "... return",
1011 * whereas the default/Z_OK one is "... return code".
1013 png_ptr
->zstream
.msg
= PNGZ_MSG_CAST("unexpected zlib return");
1018 /* png_convert_size: a PNGAPI but no longer in png.h, so deleted
1022 /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
1023 #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */
1025 png_colorspace_check_gamma(png_const_structrp png_ptr
,
1026 png_colorspacerp colorspace
, png_fixed_point gAMA
, int from
)
1027 /* This is called to check a new gamma value against an existing one. The
1028 * routine returns false if the new gamma value should not be written.
1030 * 'from' says where the new gamma value comes from:
1032 * 0: the new gamma value is the libpng estimate for an ICC profile
1033 * 1: the new gamma value comes from a gAMA chunk
1034 * 2: the new gamma value comes from an sRGB chunk
1037 png_fixed_point gtest
;
1039 if ((colorspace
->flags
& PNG_COLORSPACE_HAVE_GAMMA
) != 0 &&
1040 (png_muldiv(>est
, colorspace
->gamma
, PNG_FP_1
, gAMA
) == 0 ||
1041 png_gamma_significant(gtest
) != 0))
1043 /* Either this is an sRGB image, in which case the calculated gamma
1044 * approximation should match, or this is an image with a profile and the
1045 * value libpng calculates for the gamma of the profile does not match the
1046 * value recorded in the file. The former, sRGB, case is an error, the
1047 * latter is just a warning.
1049 if ((colorspace
->flags
& PNG_COLORSPACE_FROM_sRGB
) != 0 || from
== 2)
1051 png_chunk_report(png_ptr
, "gamma value does not match sRGB",
1053 /* Do not overwrite an sRGB value */
1057 else /* sRGB tag not involved */
1059 png_chunk_report(png_ptr
, "gamma value does not match libpng estimate",
1069 png_colorspace_set_gamma(png_const_structrp png_ptr
,
1070 png_colorspacerp colorspace
, png_fixed_point gAMA
)
1072 /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
1073 * occur. Since the fixed point representation is asymetrical it is
1074 * possible for 1/gamma to overflow the limit of 21474 and this means the
1075 * gamma value must be at least 5/100000 and hence at most 20000.0. For
1076 * safety the limits here are a little narrower. The values are 0.00016 to
1077 * 6250.0, which are truly ridiculous gamma values (and will produce
1078 * displays that are all black or all white.)
1080 * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk
1081 * handling code, which only required the value to be >0.
1083 png_const_charp errmsg
;
1085 if (gAMA
< 16 || gAMA
> 625000000)
1086 errmsg
= "gamma value out of range";
1088 # ifdef PNG_READ_gAMA_SUPPORTED
1089 /* Allow the application to set the gamma value more than once */
1090 else if ((png_ptr
->mode
& PNG_IS_READ_STRUCT
) != 0 &&
1091 (colorspace
->flags
& PNG_COLORSPACE_FROM_gAMA
) != 0)
1092 errmsg
= "duplicate";
1095 /* Do nothing if the colorspace is already invalid */
1096 else if ((colorspace
->flags
& PNG_COLORSPACE_INVALID
) != 0)
1101 if (png_colorspace_check_gamma(png_ptr
, colorspace
, gAMA
,
1102 1/*from gAMA*/) != 0)
1104 /* Store this gamma value. */
1105 colorspace
->gamma
= gAMA
;
1106 colorspace
->flags
|=
1107 (PNG_COLORSPACE_HAVE_GAMMA
| PNG_COLORSPACE_FROM_gAMA
);
1110 /* At present if the check_gamma test fails the gamma of the colorspace is
1111 * not updated however the colorspace is not invalidated. This
1112 * corresponds to the case where the existing gamma comes from an sRGB
1113 * chunk or profile. An error message has already been output.
1118 /* Error exit - errmsg has been set. */
1119 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1120 png_chunk_report(png_ptr
, errmsg
, PNG_CHUNK_WRITE_ERROR
);
1124 png_colorspace_sync_info(png_const_structrp png_ptr
, png_inforp info_ptr
)
1126 if ((info_ptr
->colorspace
.flags
& PNG_COLORSPACE_INVALID
) != 0)
1128 /* Everything is invalid */
1129 info_ptr
->valid
&= ~(PNG_INFO_gAMA
|PNG_INFO_cHRM
|PNG_INFO_sRGB
|
1132 # ifdef PNG_COLORSPACE_SUPPORTED
1133 /* Clean up the iCCP profile now if it won't be used. */
1134 png_free_data(png_ptr
, info_ptr
, PNG_FREE_ICCP
, -1/*not used*/);
1142 # ifdef PNG_COLORSPACE_SUPPORTED
1143 /* Leave the INFO_iCCP flag set if the pngset.c code has already set
1144 * it; this allows a PNG to contain a profile which matches sRGB and
1145 * yet still have that profile retrievable by the application.
1147 if ((info_ptr
->colorspace
.flags
& PNG_COLORSPACE_MATCHES_sRGB
) != 0)
1148 info_ptr
->valid
|= PNG_INFO_sRGB
;
1151 info_ptr
->valid
&= ~PNG_INFO_sRGB
;
1153 if ((info_ptr
->colorspace
.flags
& PNG_COLORSPACE_HAVE_ENDPOINTS
) != 0)
1154 info_ptr
->valid
|= PNG_INFO_cHRM
;
1157 info_ptr
->valid
&= ~PNG_INFO_cHRM
;
1160 if ((info_ptr
->colorspace
.flags
& PNG_COLORSPACE_HAVE_GAMMA
) != 0)
1161 info_ptr
->valid
|= PNG_INFO_gAMA
;
1164 info_ptr
->valid
&= ~PNG_INFO_gAMA
;
1168 #ifdef PNG_READ_SUPPORTED
1170 png_colorspace_sync(png_const_structrp png_ptr
, png_inforp info_ptr
)
1172 if (info_ptr
== NULL
) /* reduce code size; check here not in the caller */
1175 info_ptr
->colorspace
= png_ptr
->colorspace
;
1176 png_colorspace_sync_info(png_ptr
, info_ptr
);
1181 #ifdef PNG_COLORSPACE_SUPPORTED
1182 /* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
1183 * cHRM, as opposed to using chromaticities. These internal APIs return
1184 * non-zero on a parameter error. The X, Y and Z values are required to be
1185 * positive and less than 1.0.
1188 png_xy_from_XYZ(png_xy
*xy
, const png_XYZ
*XYZ
)
1190 png_int_32 d
, dwhite
, whiteX
, whiteY
;
1192 d
= XYZ
->red_X
+ XYZ
->red_Y
+ XYZ
->red_Z
;
1193 if (png_muldiv(&xy
->redx
, XYZ
->red_X
, PNG_FP_1
, d
) == 0)
1195 if (png_muldiv(&xy
->redy
, XYZ
->red_Y
, PNG_FP_1
, d
) == 0)
1198 whiteX
= XYZ
->red_X
;
1199 whiteY
= XYZ
->red_Y
;
1201 d
= XYZ
->green_X
+ XYZ
->green_Y
+ XYZ
->green_Z
;
1202 if (png_muldiv(&xy
->greenx
, XYZ
->green_X
, PNG_FP_1
, d
) == 0)
1204 if (png_muldiv(&xy
->greeny
, XYZ
->green_Y
, PNG_FP_1
, d
) == 0)
1207 whiteX
+= XYZ
->green_X
;
1208 whiteY
+= XYZ
->green_Y
;
1210 d
= XYZ
->blue_X
+ XYZ
->blue_Y
+ XYZ
->blue_Z
;
1211 if (png_muldiv(&xy
->bluex
, XYZ
->blue_X
, PNG_FP_1
, d
) == 0)
1213 if (png_muldiv(&xy
->bluey
, XYZ
->blue_Y
, PNG_FP_1
, d
) == 0)
1216 whiteX
+= XYZ
->blue_X
;
1217 whiteY
+= XYZ
->blue_Y
;
1219 /* The reference white is simply the sum of the end-point (X,Y,Z) vectors,
1222 if (png_muldiv(&xy
->whitex
, whiteX
, PNG_FP_1
, dwhite
) == 0)
1224 if (png_muldiv(&xy
->whitey
, whiteY
, PNG_FP_1
, dwhite
) == 0)
1231 png_XYZ_from_xy(png_XYZ
*XYZ
, const png_xy
*xy
)
1233 png_fixed_point red_inverse
, green_inverse
, blue_scale
;
1234 png_fixed_point left
, right
, denominator
;
1236 /* Check xy and, implicitly, z. Note that wide gamut color spaces typically
1237 * have end points with 0 tristimulus values (these are impossible end
1238 * points, but they are used to cover the possible colors). We check
1239 * xy->whitey against 5, not 0, to avoid a possible integer overflow.
1241 if (xy
->redx
< 0 || xy
->redx
> PNG_FP_1
) return 1;
1242 if (xy
->redy
< 0 || xy
->redy
> PNG_FP_1
-xy
->redx
) return 1;
1243 if (xy
->greenx
< 0 || xy
->greenx
> PNG_FP_1
) return 1;
1244 if (xy
->greeny
< 0 || xy
->greeny
> PNG_FP_1
-xy
->greenx
) return 1;
1245 if (xy
->bluex
< 0 || xy
->bluex
> PNG_FP_1
) return 1;
1246 if (xy
->bluey
< 0 || xy
->bluey
> PNG_FP_1
-xy
->bluex
) return 1;
1247 if (xy
->whitex
< 0 || xy
->whitex
> PNG_FP_1
) return 1;
1248 if (xy
->whitey
< 5 || xy
->whitey
> PNG_FP_1
-xy
->whitex
) return 1;
1250 /* The reverse calculation is more difficult because the original tristimulus
1251 * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
1252 * derived values were recorded in the cHRM chunk;
1253 * (red,green,blue,white)x(x,y). This loses one degree of freedom and
1254 * therefore an arbitrary ninth value has to be introduced to undo the
1255 * original transformations.
1257 * Think of the original end-points as points in (X,Y,Z) space. The
1258 * chromaticity values (c) have the property:
1264 * For each c (x,y,z) from the corresponding original C (X,Y,Z). Thus the
1265 * three chromaticity values (x,y,z) for each end-point obey the
1270 * This describes the plane in (X,Y,Z) space that intersects each axis at the
1271 * value 1.0; call this the chromaticity plane. Thus the chromaticity
1272 * calculation has scaled each end-point so that it is on the x+y+z=1 plane
1273 * and chromaticity is the intersection of the vector from the origin to the
1274 * (X,Y,Z) value with the chromaticity plane.
1276 * To fully invert the chromaticity calculation we would need the three
1277 * end-point scale factors, (red-scale, green-scale, blue-scale), but these
1278 * were not recorded. Instead we calculated the reference white (X,Y,Z) and
1279 * recorded the chromaticity of this. The reference white (X,Y,Z) would have
1280 * given all three of the scale factors since:
1282 * color-C = color-c * color-scale
1283 * white-C = red-C + green-C + blue-C
1284 * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
1286 * But cHRM records only white-x and white-y, so we have lost the white scale
1289 * white-C = white-c*white-scale
1291 * To handle this the inverse transformation makes an arbitrary assumption
1292 * about white-scale:
1294 * Assume: white-Y = 1.0
1295 * Hence: white-scale = 1/white-y
1296 * Or: red-Y + green-Y + blue-Y = 1.0
1298 * Notice the last statement of the assumption gives an equation in three of
1299 * the nine values we want to calculate. 8 more equations come from the
1300 * above routine as summarised at the top above (the chromaticity
1303 * Given: color-x = color-X / (color-X + color-Y + color-Z)
1304 * Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0
1306 * This is 9 simultaneous equations in the 9 variables "color-C" and can be
1307 * solved by Cramer's rule. Cramer's rule requires calculating 10 9x9 matrix
1308 * determinants, however this is not as bad as it seems because only 28 of
1309 * the total of 90 terms in the various matrices are non-zero. Nevertheless
1310 * Cramer's rule is notoriously numerically unstable because the determinant
1311 * calculation involves the difference of large, but similar, numbers. It is
1312 * difficult to be sure that the calculation is stable for real world values
1313 * and it is certain that it becomes unstable where the end points are close
1316 * So this code uses the perhaps slightly less optimal but more
1317 * understandable and totally obvious approach of calculating color-scale.
1319 * This algorithm depends on the precision in white-scale and that is
1320 * (1/white-y), so we can immediately see that as white-y approaches 0 the
1321 * accuracy inherent in the cHRM chunk drops off substantially.
1323 * libpng arithmetic: a simple inversion of the above equations
1324 * ------------------------------------------------------------
1326 * white_scale = 1/white-y
1327 * white-X = white-x * white-scale
1329 * white-Z = (1 - white-x - white-y) * white_scale
1331 * white-C = red-C + green-C + blue-C
1332 * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
1334 * This gives us three equations in (red-scale,green-scale,blue-scale) where
1335 * all the coefficients are now known:
1337 * red-x*red-scale + green-x*green-scale + blue-x*blue-scale
1339 * red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
1340 * red-z*red-scale + green-z*green-scale + blue-z*blue-scale
1341 * = (1 - white-x - white-y)/white-y
1343 * In the last equation color-z is (1 - color-x - color-y) so we can add all
1344 * three equations together to get an alternative third:
1346 * red-scale + green-scale + blue-scale = 1/white-y = white-scale
1348 * So now we have a Cramer's rule solution where the determinants are just
1349 * 3x3 - far more tractible. Unfortunately 3x3 determinants still involve
1350 * multiplication of three coefficients so we can't guarantee to avoid
1351 * overflow in the libpng fixed point representation. Using Cramer's rule in
1352 * floating point is probably a good choice here, but it's not an option for
1353 * fixed point. Instead proceed to simplify the first two equations by
1354 * eliminating what is likely to be the largest value, blue-scale:
1356 * blue-scale = white-scale - red-scale - green-scale
1360 * (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =
1361 * (white-x - blue-x)*white-scale
1363 * (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =
1364 * 1 - blue-y*white-scale
1366 * And now we can trivially solve for (red-scale,green-scale):
1369 * (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale
1370 * -----------------------------------------------------------
1374 * 1 - blue-y*white-scale - (green-y - blue-y) * green-scale
1375 * ---------------------------------------------------------
1381 * ( (green-x - blue-x) * (white-y - blue-y) -
1382 * (green-y - blue-y) * (white-x - blue-x) ) / white-y
1383 * -------------------------------------------------------------------------
1384 * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
1387 * ( (red-y - blue-y) * (white-x - blue-x) -
1388 * (red-x - blue-x) * (white-y - blue-y) ) / white-y
1389 * -------------------------------------------------------------------------
1390 * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
1393 * The input values have 5 decimal digits of accuracy. The values are all in
1394 * the range 0 < value < 1, so simple products are in the same range but may
1395 * need up to 10 decimal digits to preserve the original precision and avoid
1396 * underflow. Because we are using a 32-bit signed representation we cannot
1397 * match this; the best is a little over 9 decimal digits, less than 10.
1399 * The approach used here is to preserve the maximum precision within the
1400 * signed representation. Because the red-scale calculation above uses the
1401 * difference between two products of values that must be in the range -1..+1
1402 * it is sufficient to divide the product by 7; ceil(100,000/32767*2). The
1403 * factor is irrelevant in the calculation because it is applied to both
1404 * numerator and denominator.
1406 * Note that the values of the differences of the products of the
1407 * chromaticities in the above equations tend to be small, for example for
1408 * the sRGB chromaticities they are:
1410 * red numerator: -0.04751
1411 * green numerator: -0.08788
1412 * denominator: -0.2241 (without white-y multiplication)
1414 * The resultant Y coefficients from the chromaticities of some widely used
1415 * color space definitions are (to 15 decimal places):
1418 * 0.212639005871510 0.715168678767756 0.072192315360734
1420 * 0.288071128229293 0.711843217810102 0.000085653960605
1422 * 0.297344975250536 0.627363566255466 0.075291458493998
1423 * Adobe Wide Gamut RGB
1424 * 0.258728243040113 0.724682314948566 0.016589442011321
1426 /* By the argument, above overflow should be impossible here. The return
1427 * value of 2 indicates an internal error to the caller.
1429 if (png_muldiv(&left
, xy
->greenx
-xy
->bluex
, xy
->redy
- xy
->bluey
, 7) == 0)
1431 if (png_muldiv(&right
, xy
->greeny
-xy
->bluey
, xy
->redx
- xy
->bluex
, 7) == 0)
1433 denominator
= left
- right
;
1435 /* Now find the red numerator. */
1436 if (png_muldiv(&left
, xy
->greenx
-xy
->bluex
, xy
->whitey
-xy
->bluey
, 7) == 0)
1438 if (png_muldiv(&right
, xy
->greeny
-xy
->bluey
, xy
->whitex
-xy
->bluex
, 7) == 0)
1441 /* Overflow is possible here and it indicates an extreme set of PNG cHRM
1442 * chunk values. This calculation actually returns the reciprocal of the
1443 * scale value because this allows us to delay the multiplication of white-y
1444 * into the denominator, which tends to produce a small number.
1446 if (png_muldiv(&red_inverse
, xy
->whitey
, denominator
, left
-right
) == 0 ||
1447 red_inverse
<= xy
->whitey
/* r+g+b scales = white scale */)
1450 /* Similarly for green_inverse: */
1451 if (png_muldiv(&left
, xy
->redy
-xy
->bluey
, xy
->whitex
-xy
->bluex
, 7) == 0)
1453 if (png_muldiv(&right
, xy
->redx
-xy
->bluex
, xy
->whitey
-xy
->bluey
, 7) == 0)
1455 if (png_muldiv(&green_inverse
, xy
->whitey
, denominator
, left
-right
) == 0 ||
1456 green_inverse
<= xy
->whitey
)
1459 /* And the blue scale, the checks above guarantee this can't overflow but it
1460 * can still produce 0 for extreme cHRM values.
1462 blue_scale
= png_reciprocal(xy
->whitey
) - png_reciprocal(red_inverse
) -
1463 png_reciprocal(green_inverse
);
1464 if (blue_scale
<= 0)
1468 /* And fill in the png_XYZ: */
1469 if (png_muldiv(&XYZ
->red_X
, xy
->redx
, PNG_FP_1
, red_inverse
) == 0)
1471 if (png_muldiv(&XYZ
->red_Y
, xy
->redy
, PNG_FP_1
, red_inverse
) == 0)
1473 if (png_muldiv(&XYZ
->red_Z
, PNG_FP_1
- xy
->redx
- xy
->redy
, PNG_FP_1
,
1477 if (png_muldiv(&XYZ
->green_X
, xy
->greenx
, PNG_FP_1
, green_inverse
) == 0)
1479 if (png_muldiv(&XYZ
->green_Y
, xy
->greeny
, PNG_FP_1
, green_inverse
) == 0)
1481 if (png_muldiv(&XYZ
->green_Z
, PNG_FP_1
- xy
->greenx
- xy
->greeny
, PNG_FP_1
,
1482 green_inverse
) == 0)
1485 if (png_muldiv(&XYZ
->blue_X
, xy
->bluex
, blue_scale
, PNG_FP_1
) == 0)
1487 if (png_muldiv(&XYZ
->blue_Y
, xy
->bluey
, blue_scale
, PNG_FP_1
) == 0)
1489 if (png_muldiv(&XYZ
->blue_Z
, PNG_FP_1
- xy
->bluex
- xy
->bluey
, blue_scale
,
1493 return 0; /*success*/
1497 png_XYZ_normalize(png_XYZ
*XYZ
)
1501 if (XYZ
->red_Y
< 0 || XYZ
->green_Y
< 0 || XYZ
->blue_Y
< 0 ||
1502 XYZ
->red_X
< 0 || XYZ
->green_X
< 0 || XYZ
->blue_X
< 0 ||
1503 XYZ
->red_Z
< 0 || XYZ
->green_Z
< 0 || XYZ
->blue_Z
< 0)
1506 /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.
1507 * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
1508 * relying on addition of two positive values producing a negative one is not
1512 if (0x7fffffff - Y
< XYZ
->green_X
)
1515 if (0x7fffffff - Y
< XYZ
->blue_X
)
1521 if (png_muldiv(&XYZ
->red_X
, XYZ
->red_X
, PNG_FP_1
, Y
) == 0)
1523 if (png_muldiv(&XYZ
->red_Y
, XYZ
->red_Y
, PNG_FP_1
, Y
) == 0)
1525 if (png_muldiv(&XYZ
->red_Z
, XYZ
->red_Z
, PNG_FP_1
, Y
) == 0)
1528 if (png_muldiv(&XYZ
->green_X
, XYZ
->green_X
, PNG_FP_1
, Y
) == 0)
1530 if (png_muldiv(&XYZ
->green_Y
, XYZ
->green_Y
, PNG_FP_1
, Y
) == 0)
1532 if (png_muldiv(&XYZ
->green_Z
, XYZ
->green_Z
, PNG_FP_1
, Y
) == 0)
1535 if (png_muldiv(&XYZ
->blue_X
, XYZ
->blue_X
, PNG_FP_1
, Y
) == 0)
1537 if (png_muldiv(&XYZ
->blue_Y
, XYZ
->blue_Y
, PNG_FP_1
, Y
) == 0)
1539 if (png_muldiv(&XYZ
->blue_Z
, XYZ
->blue_Z
, PNG_FP_1
, Y
) == 0)
1547 png_colorspace_endpoints_match(const png_xy
*xy1
, const png_xy
*xy2
, int delta
)
1549 /* Allow an error of +/-0.01 (absolute value) on each chromaticity */
1550 if (PNG_OUT_OF_RANGE(xy1
->whitex
, xy2
->whitex
,delta
) ||
1551 PNG_OUT_OF_RANGE(xy1
->whitey
, xy2
->whitey
,delta
) ||
1552 PNG_OUT_OF_RANGE(xy1
->redx
, xy2
->redx
, delta
) ||
1553 PNG_OUT_OF_RANGE(xy1
->redy
, xy2
->redy
, delta
) ||
1554 PNG_OUT_OF_RANGE(xy1
->greenx
, xy2
->greenx
,delta
) ||
1555 PNG_OUT_OF_RANGE(xy1
->greeny
, xy2
->greeny
,delta
) ||
1556 PNG_OUT_OF_RANGE(xy1
->bluex
, xy2
->bluex
, delta
) ||
1557 PNG_OUT_OF_RANGE(xy1
->bluey
, xy2
->bluey
, delta
))
1562 /* Added in libpng-1.6.0, a different check for the validity of a set of cHRM
1563 * chunk chromaticities. Earlier checks used to simply look for the overflow
1564 * condition (where the determinant of the matrix to solve for XYZ ends up zero
1565 * because the chromaticity values are not all distinct.) Despite this it is
1566 * theoretically possible to produce chromaticities that are apparently valid
1567 * but that rapidly degrade to invalid, potentially crashing, sets because of
1568 * arithmetic inaccuracies when calculations are performed on them. The new
1569 * check is to round-trip xy -> XYZ -> xy and then check that the result is
1570 * within a small percentage of the original.
1573 png_colorspace_check_xy(png_XYZ
*XYZ
, const png_xy
*xy
)
1578 /* As a side-effect this routine also returns the XYZ endpoints. */
1579 result
= png_XYZ_from_xy(XYZ
, xy
);
1583 result
= png_xy_from_XYZ(&xy_test
, XYZ
);
1587 if (png_colorspace_endpoints_match(xy
, &xy_test
,
1588 5/*actually, the math is pretty accurate*/) != 0)
1595 /* This is the check going the other way. The XYZ is modified to normalize it
1596 * (another side-effect) and the xy chromaticities are returned.
1599 png_colorspace_check_XYZ(png_xy
*xy
, png_XYZ
*XYZ
)
1604 result
= png_XYZ_normalize(XYZ
);
1608 result
= png_xy_from_XYZ(xy
, XYZ
);
1613 return png_colorspace_check_xy(&XYZtemp
, xy
);
1616 /* Used to check for an endpoint match against sRGB */
1617 static const png_xy sRGB_xy
= /* From ITU-R BT.709-3 */
1620 /* red */ 64000, 33000,
1621 /* green */ 30000, 60000,
1622 /* blue */ 15000, 6000,
1623 /* white */ 31270, 32900
1627 png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr
,
1628 png_colorspacerp colorspace
, const png_xy
*xy
, const png_XYZ
*XYZ
,
1631 if ((colorspace
->flags
& PNG_COLORSPACE_INVALID
) != 0)
1634 /* The consistency check is performed on the chromaticities; this factors out
1635 * variations because of the normalization (or not) of the end point Y
1638 if (preferred
< 2 &&
1639 (colorspace
->flags
& PNG_COLORSPACE_HAVE_ENDPOINTS
) != 0)
1641 /* The end points must be reasonably close to any we already have. The
1642 * following allows an error of up to +/-.001
1644 if (png_colorspace_endpoints_match(xy
, &colorspace
->end_points_xy
,
1647 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1648 png_benign_error(png_ptr
, "inconsistent chromaticities");
1649 return 0; /* failed */
1652 /* Only overwrite with preferred values */
1654 return 1; /* ok, but no change */
1657 colorspace
->end_points_xy
= *xy
;
1658 colorspace
->end_points_XYZ
= *XYZ
;
1659 colorspace
->flags
|= PNG_COLORSPACE_HAVE_ENDPOINTS
;
1661 /* The end points are normally quoted to two decimal digits, so allow +/-0.01
1664 if (png_colorspace_endpoints_match(xy
, &sRGB_xy
, 1000) != 0)
1665 colorspace
->flags
|= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB
;
1668 colorspace
->flags
&= PNG_COLORSPACE_CANCEL(
1669 PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB
);
1671 return 2; /* ok and changed */
1675 png_colorspace_set_chromaticities(png_const_structrp png_ptr
,
1676 png_colorspacerp colorspace
, const png_xy
*xy
, int preferred
)
1678 /* We must check the end points to ensure they are reasonable - in the past
1679 * color management systems have crashed as a result of getting bogus
1680 * colorant values, while this isn't the fault of libpng it is the
1681 * responsibility of libpng because PNG carries the bomb and libpng is in a
1682 * position to protect against it.
1686 switch (png_colorspace_check_xy(&XYZ
, xy
))
1688 case 0: /* success */
1689 return png_colorspace_set_xy_and_XYZ(png_ptr
, colorspace
, xy
, &XYZ
,
1693 /* We can't invert the chromaticities so we can't produce value XYZ
1694 * values. Likely as not a color management system will fail too.
1696 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1697 png_benign_error(png_ptr
, "invalid chromaticities");
1701 /* libpng is broken; this should be a warning but if it happens we
1702 * want error reports so for the moment it is an error.
1704 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1705 png_error(png_ptr
, "internal error checking chromaticities");
1709 return 0; /* failed */
1713 png_colorspace_set_endpoints(png_const_structrp png_ptr
,
1714 png_colorspacerp colorspace
, const png_XYZ
*XYZ_in
, int preferred
)
1716 png_XYZ XYZ
= *XYZ_in
;
1719 switch (png_colorspace_check_XYZ(&xy
, &XYZ
))
1722 return png_colorspace_set_xy_and_XYZ(png_ptr
, colorspace
, &xy
, &XYZ
,
1726 /* End points are invalid. */
1727 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1728 png_benign_error(png_ptr
, "invalid end points");
1732 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1733 png_error(png_ptr
, "internal error checking chromaticities");
1737 return 0; /* failed */
1740 #if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED)
1741 /* Error message generation */
1743 png_icc_tag_char(png_uint_32 byte
)
1746 if (byte
>= 32 && byte
<= 126)
1753 png_icc_tag_name(char *name
, png_uint_32 tag
)
1756 name
[1] = png_icc_tag_char(tag
>> 24);
1757 name
[2] = png_icc_tag_char(tag
>> 16);
1758 name
[3] = png_icc_tag_char(tag
>> 8);
1759 name
[4] = png_icc_tag_char(tag
);
1764 is_ICC_signature_char(png_alloc_size_t it
)
1766 return it
== 32 || (it
>= 48 && it
<= 57) || (it
>= 65 && it
<= 90) ||
1767 (it
>= 97 && it
<= 122);
1771 is_ICC_signature(png_alloc_size_t it
)
1773 return is_ICC_signature_char(it
>> 24) /* checks all the top bits */ &&
1774 is_ICC_signature_char((it
>> 16) & 0xff) &&
1775 is_ICC_signature_char((it
>> 8) & 0xff) &&
1776 is_ICC_signature_char(it
& 0xff);
1780 png_icc_profile_error(png_const_structrp png_ptr
, png_colorspacerp colorspace
,
1781 png_const_charp name
, png_alloc_size_t value
, png_const_charp reason
)
1784 char message
[196]; /* see below for calculation */
1786 if (colorspace
!= NULL
)
1787 colorspace
->flags
|= PNG_COLORSPACE_INVALID
;
1789 pos
= png_safecat(message
, (sizeof message
), 0, "profile '"); /* 9 chars */
1790 pos
= png_safecat(message
, pos
+79, pos
, name
); /* Truncate to 79 chars */
1791 pos
= png_safecat(message
, (sizeof message
), pos
, "': "); /* +2 = 90 */
1792 if (is_ICC_signature(value
) != 0)
1794 /* So 'value' is at most 4 bytes and the following cast is safe */
1795 png_icc_tag_name(message
+pos
, (png_uint_32
)value
);
1796 pos
+= 6; /* total +8; less than the else clause */
1797 message
[pos
++] = ':';
1798 message
[pos
++] = ' ';
1800 # ifdef PNG_WARNINGS_SUPPORTED
1803 char number
[PNG_NUMBER_BUFFER_SIZE
]; /* +24 = 114*/
1805 pos
= png_safecat(message
, (sizeof message
), pos
,
1806 png_format_number(number
, number
+(sizeof number
),
1807 PNG_NUMBER_FORMAT_x
, value
));
1808 pos
= png_safecat(message
, (sizeof message
), pos
, "h: "); /*+2 = 116*/
1811 /* The 'reason' is an arbitrary message, allow +79 maximum 195 */
1812 pos
= png_safecat(message
, (sizeof message
), pos
, reason
);
1815 /* This is recoverable, but make it unconditionally an app_error on write to
1816 * avoid writing invalid ICC profiles into PNG files (i.e., we handle them
1817 * on read, with a warning, but on write unless the app turns off
1818 * application errors the PNG won't be written.)
1820 png_chunk_report(png_ptr
, message
,
1821 (colorspace
!= NULL
) ? PNG_CHUNK_ERROR
: PNG_CHUNK_WRITE_ERROR
);
1825 #endif /* sRGB || iCCP */
1827 #ifdef PNG_sRGB_SUPPORTED
1829 png_colorspace_set_sRGB(png_const_structrp png_ptr
, png_colorspacerp colorspace
,
1832 /* sRGB sets known gamma, end points and (from the chunk) intent. */
1833 /* IMPORTANT: these are not necessarily the values found in an ICC profile
1834 * because ICC profiles store values adapted to a D50 environment; it is
1835 * expected that the ICC profile mediaWhitePointTag will be D50; see the
1836 * checks and code elsewhere to understand this better.
1838 * These XYZ values, which are accurate to 5dp, produce rgb to gray
1839 * coefficients of (6968,23435,2366), which are reduced (because they add up
1840 * to 32769 not 32768) to (6968,23434,2366). These are the values that
1841 * libpng has traditionally used (and are the best values given the 15bit
1842 * algorithm used by the rgb to gray code.)
1844 static const png_XYZ sRGB_XYZ
= /* D65 XYZ (*not* the D50 adapted values!) */
1847 /* red */ 41239, 21264, 1933,
1848 /* green */ 35758, 71517, 11919,
1849 /* blue */ 18048, 7219, 95053
1852 /* Do nothing if the colorspace is already invalidated. */
1853 if ((colorspace
->flags
& PNG_COLORSPACE_INVALID
) != 0)
1856 /* Check the intent, then check for existing settings. It is valid for the
1857 * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must
1858 * be consistent with the correct values. If, however, this function is
1859 * called below because an iCCP chunk matches sRGB then it is quite
1860 * conceivable that an older app recorded incorrect gAMA and cHRM because of
1861 * an incorrect calculation based on the values in the profile - this does
1862 * *not* invalidate the profile (though it still produces an error, which can
1865 if (intent
< 0 || intent
>= PNG_sRGB_INTENT_LAST
)
1866 return png_icc_profile_error(png_ptr
, colorspace
, "sRGB",
1867 (unsigned)intent
, "invalid sRGB rendering intent");
1869 if ((colorspace
->flags
& PNG_COLORSPACE_HAVE_INTENT
) != 0 &&
1870 colorspace
->rendering_intent
!= intent
)
1871 return png_icc_profile_error(png_ptr
, colorspace
, "sRGB",
1872 (unsigned)intent
, "inconsistent rendering intents");
1874 if ((colorspace
->flags
& PNG_COLORSPACE_FROM_sRGB
) != 0)
1876 png_benign_error(png_ptr
, "duplicate sRGB information ignored");
1880 /* If the standard sRGB cHRM chunk does not match the one from the PNG file
1881 * warn but overwrite the value with the correct one.
1883 if ((colorspace
->flags
& PNG_COLORSPACE_HAVE_ENDPOINTS
) != 0 &&
1884 !png_colorspace_endpoints_match(&sRGB_xy
, &colorspace
->end_points_xy
,
1886 png_chunk_report(png_ptr
, "cHRM chunk does not match sRGB",
1889 /* This check is just done for the error reporting - the routine always
1890 * returns true when the 'from' argument corresponds to sRGB (2).
1892 (void)png_colorspace_check_gamma(png_ptr
, colorspace
, PNG_GAMMA_sRGB_INVERSE
,
1895 /* intent: bugs in GCC force 'int' to be used as the parameter type. */
1896 colorspace
->rendering_intent
= (png_uint_16
)intent
;
1897 colorspace
->flags
|= PNG_COLORSPACE_HAVE_INTENT
;
1900 colorspace
->end_points_xy
= sRGB_xy
;
1901 colorspace
->end_points_XYZ
= sRGB_XYZ
;
1902 colorspace
->flags
|=
1903 (PNG_COLORSPACE_HAVE_ENDPOINTS
|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB
);
1906 colorspace
->gamma
= PNG_GAMMA_sRGB_INVERSE
;
1907 colorspace
->flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
1909 /* Finally record that we have an sRGB profile */
1910 colorspace
->flags
|=
1911 (PNG_COLORSPACE_MATCHES_sRGB
|PNG_COLORSPACE_FROM_sRGB
);
1917 #ifdef PNG_iCCP_SUPPORTED
1918 /* Encoded value of D50 as an ICC XYZNumber. From the ICC 2010 spec the value
1919 * is XYZ(0.9642,1.0,0.8249), which scales to:
1921 * (63189.8112, 65536, 54060.6464)
1923 static const png_byte D50_nCIEXYZ
[12] =
1924 { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };
1927 png_icc_check_length(png_const_structrp png_ptr
, png_colorspacerp colorspace
,
1928 png_const_charp name
, png_uint_32 profile_length
)
1930 if (profile_length
< 132)
1931 return png_icc_profile_error(png_ptr
, colorspace
, name
, profile_length
,
1938 png_icc_check_header(png_const_structrp png_ptr
, png_colorspacerp colorspace
,
1939 png_const_charp name
, png_uint_32 profile_length
,
1940 png_const_bytep profile
/* first 132 bytes only */, int color_type
)
1944 /* Length check; this cannot be ignored in this code because profile_length
1945 * is used later to check the tag table, so even if the profile seems over
1946 * long profile_length from the caller must be correct. The caller can fix
1947 * this up on read or write by just passing in the profile header length.
1949 temp
= png_get_uint_32(profile
);
1950 if (temp
!= profile_length
)
1951 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
1952 "length does not match profile");
1954 temp
= (png_uint_32
) (*(profile
+8));
1955 if (temp
> 3 && (profile_length
& 3))
1956 return png_icc_profile_error(png_ptr
, colorspace
, name
, profile_length
,
1959 temp
= png_get_uint_32(profile
+128); /* tag count: 12 bytes/tag */
1960 if (temp
> 357913930 || /* (2^32-4-132)/12: maximum possible tag count */
1961 profile_length
< 132+12*temp
) /* truncated tag table */
1962 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
1963 "tag count too large");
1965 /* The 'intent' must be valid or we can't store it, ICC limits the intent to
1968 temp
= png_get_uint_32(profile
+64);
1969 if (temp
>= 0xffff) /* The ICC limit */
1970 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
1971 "invalid rendering intent");
1973 /* This is just a warning because the profile may be valid in future
1976 if (temp
>= PNG_sRGB_INTENT_LAST
)
1977 (void)png_icc_profile_error(png_ptr
, NULL
, name
, temp
,
1978 "intent outside defined range");
1980 /* At this point the tag table can't be checked because it hasn't necessarily
1981 * been loaded; however, various header fields can be checked. These checks
1982 * are for values permitted by the PNG spec in an ICC profile; the PNG spec
1983 * restricts the profiles that can be passed in an iCCP chunk (they must be
1984 * appropriate to processing PNG data!)
1987 /* Data checks (could be skipped). These checks must be independent of the
1988 * version number; however, the version number doesn't accomodate changes in
1989 * the header fields (just the known tags and the interpretation of the
1992 temp
= png_get_uint_32(profile
+36); /* signature 'ascp' */
1993 if (temp
!= 0x61637370)
1994 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
1995 "invalid signature");
1997 /* Currently the PCS illuminant/adopted white point (the computational
1998 * white point) are required to be D50,
1999 * however the profile contains a record of the illuminant so perhaps ICC
2000 * expects to be able to change this in the future (despite the rationale in
2001 * the introduction for using a fixed PCS adopted white.) Consequently the
2002 * following is just a warning.
2004 if (memcmp(profile
+68, D50_nCIEXYZ
, 12) != 0)
2005 (void)png_icc_profile_error(png_ptr
, NULL
, name
, 0/*no tag value*/,
2006 "PCS illuminant is not D50");
2008 /* The PNG spec requires this:
2009 * "If the iCCP chunk is present, the image samples conform to the colour
2010 * space represented by the embedded ICC profile as defined by the
2011 * International Color Consortium [ICC]. The colour space of the ICC profile
2012 * shall be an RGB colour space for colour images (PNG colour types 2, 3, and
2013 * 6), or a greyscale colour space for greyscale images (PNG colour types 0
2016 * This checking code ensures the embedded profile (on either read or write)
2017 * conforms to the specification requirements. Notice that an ICC 'gray'
2018 * color-space profile contains the information to transform the monochrome
2019 * data to XYZ or L*a*b (according to which PCS the profile uses) and this
2020 * should be used in preference to the standard libpng K channel replication
2021 * into R, G and B channels.
2023 * Previously it was suggested that an RGB profile on grayscale data could be
2024 * handled. However it it is clear that using an RGB profile in this context
2025 * must be an error - there is no specification of what it means. Thus it is
2026 * almost certainly more correct to ignore the profile.
2028 temp
= png_get_uint_32(profile
+16); /* data colour space field */
2031 case 0x52474220: /* 'RGB ' */
2032 if ((color_type
& PNG_COLOR_MASK_COLOR
) == 0)
2033 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
2034 "RGB color space not permitted on grayscale PNG");
2037 case 0x47524159: /* 'GRAY' */
2038 if ((color_type
& PNG_COLOR_MASK_COLOR
) != 0)
2039 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
2040 "Gray color space not permitted on RGB PNG");
2044 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
2045 "invalid ICC profile color space");
2048 /* It is up to the application to check that the profile class matches the
2049 * application requirements; the spec provides no guidance, but it's pretty
2050 * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer
2051 * ('prtr') or 'spac' (for generic color spaces). Issue a warning in these
2052 * cases. Issue an error for device link or abstract profiles - these don't
2053 * contain the records necessary to transform the color-space to anything
2054 * other than the target device (and not even that for an abstract profile).
2055 * Profiles of these classes may not be embedded in images.
2057 temp
= png_get_uint_32(profile
+12); /* profile/device class */
2060 case 0x73636E72: /* 'scnr' */
2061 case 0x6D6E7472: /* 'mntr' */
2062 case 0x70727472: /* 'prtr' */
2063 case 0x73706163: /* 'spac' */
2067 case 0x61627374: /* 'abst' */
2068 /* May not be embedded in an image */
2069 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
2070 "invalid embedded Abstract ICC profile");
2072 case 0x6C696E6B: /* 'link' */
2073 /* DeviceLink profiles cannot be interpreted in a non-device specific
2074 * fashion, if an app uses the AToB0Tag in the profile the results are
2075 * undefined unless the result is sent to the intended device,
2076 * therefore a DeviceLink profile should not be found embedded in a
2079 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
2080 "unexpected DeviceLink ICC profile class");
2082 case 0x6E6D636C: /* 'nmcl' */
2083 /* A NamedColor profile is also device specific, however it doesn't
2084 * contain an AToB0 tag that is open to misinterpretation. Almost
2085 * certainly it will fail the tests below.
2087 (void)png_icc_profile_error(png_ptr
, NULL
, name
, temp
,
2088 "unexpected NamedColor ICC profile class");
2092 /* To allow for future enhancements to the profile accept unrecognized
2093 * profile classes with a warning, these then hit the test below on the
2094 * tag content to ensure they are backward compatible with one of the
2095 * understood profiles.
2097 (void)png_icc_profile_error(png_ptr
, NULL
, name
, temp
,
2098 "unrecognized ICC profile class");
2102 /* For any profile other than a device link one the PCS must be encoded
2103 * either in XYZ or Lab.
2105 temp
= png_get_uint_32(profile
+20);
2108 case 0x58595A20: /* 'XYZ ' */
2109 case 0x4C616220: /* 'Lab ' */
2113 return png_icc_profile_error(png_ptr
, colorspace
, name
, temp
,
2114 "unexpected ICC PCS encoding");
2121 png_icc_check_tag_table(png_const_structrp png_ptr
, png_colorspacerp colorspace
,
2122 png_const_charp name
, png_uint_32 profile_length
,
2123 png_const_bytep profile
/* header plus whole tag table */)
2125 png_uint_32 tag_count
= png_get_uint_32(profile
+128);
2127 png_const_bytep tag
= profile
+132; /* The first tag */
2129 /* First scan all the tags in the table and add bits to the icc_info value
2130 * (temporarily in 'tags').
2132 for (itag
=0; itag
< tag_count
; ++itag
, tag
+= 12)
2134 png_uint_32 tag_id
= png_get_uint_32(tag
+0);
2135 png_uint_32 tag_start
= png_get_uint_32(tag
+4); /* must be aligned */
2136 png_uint_32 tag_length
= png_get_uint_32(tag
+8);/* not padded */
2138 /* The ICC specification does not exclude zero length tags, therefore the
2139 * start might actually be anywhere if there is no data, but this would be
2140 * a clear abuse of the intent of the standard so the start is checked for
2141 * being in range. All defined tag types have an 8 byte header - a 4 byte
2142 * type signature then 0.
2144 if ((tag_start
& 3) != 0)
2146 /* CNHP730S.icc shipped with Microsoft Windows 64 violates this, it is
2147 * only a warning here because libpng does not care about the
2150 (void)png_icc_profile_error(png_ptr
, NULL
, name
, tag_id
,
2151 "ICC profile tag start not a multiple of 4");
2154 /* This is a hard error; potentially it can cause read outside the
2157 if (tag_start
> profile_length
|| tag_length
> profile_length
- tag_start
)
2158 return png_icc_profile_error(png_ptr
, colorspace
, name
, tag_id
,
2159 "ICC profile tag outside profile");
2162 return 1; /* success, maybe with warnings */
2165 #ifdef PNG_sRGB_SUPPORTED
2166 #if PNG_sRGB_PROFILE_CHECKS >= 0
2167 /* Information about the known ICC sRGB profiles */
2170 png_uint_32 adler
, crc
, length
;
2176 # define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)
2177 # define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\
2178 { adler, crc, length, md5, broke, intent },
2180 } png_sRGB_checks
[] =
2182 /* This data comes from contrib/tools/checksum-icc run on downloads of
2183 * all four ICC sRGB profiles from www.color.org.
2185 /* adler32, crc32, MD5[4], intent, date, length, file-name */
2186 PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,
2187 PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
2188 "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
2190 /* ICC sRGB v2 perceptual no black-compensation: */
2191 PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
2192 PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
2193 "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
2195 PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
2196 PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
2197 "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
2199 /* ICC sRGB v4 perceptual */
2200 PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
2201 PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
2202 "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
2204 /* The following profiles have no known MD5 checksum. If there is a match
2205 * on the (empty) MD5 the other fields are used to attempt a match and
2206 * a warning is produced. The first two of these profiles have a 'cprt' tag
2207 * which suggests that they were also made by Hewlett Packard.
2209 PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
2210 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
2211 "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
2213 /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not
2214 * match the D50 PCS illuminant in the header (it is in fact the D65 values,
2215 * so the white point is recorded as the un-adapted value.) The profiles
2216 * below only differ in one byte - the intent - and are basically the same as
2217 * the previous profile except for the mediaWhitePointTag error and a missing
2218 * chromaticAdaptationTag.
2220 PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
2221 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
2222 "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")
2224 PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,
2225 PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
2226 "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
2230 png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr
,
2231 png_const_bytep profile
, uLong adler
)
2233 /* The quick check is to verify just the MD5 signature and trust the
2234 * rest of the data. Because the profile has already been verified for
2235 * correctness this is safe. png_colorspace_set_sRGB will check the 'intent'
2236 * field too, so if the profile has been edited with an intent not defined
2237 * by sRGB (but maybe defined by a later ICC specification) the read of
2238 * the profile will fail at that point.
2241 png_uint_32 length
= 0;
2242 png_uint_32 intent
= 0x10000; /* invalid */
2243 #if PNG_sRGB_PROFILE_CHECKS > 1
2244 uLong crc
= 0; /* the value for 0 length data */
2248 #ifdef PNG_SET_OPTION_SUPPORTED
2249 /* First see if PNG_SKIP_sRGB_CHECK_PROFILE has been set to "on" */
2250 if (((png_ptr
->options
>> PNG_SKIP_sRGB_CHECK_PROFILE
) & 3) ==
2255 for (i
=0; i
< (sizeof png_sRGB_checks
) / (sizeof png_sRGB_checks
[0]); ++i
)
2257 if (png_get_uint_32(profile
+84) == png_sRGB_checks
[i
].md5
[0] &&
2258 png_get_uint_32(profile
+88) == png_sRGB_checks
[i
].md5
[1] &&
2259 png_get_uint_32(profile
+92) == png_sRGB_checks
[i
].md5
[2] &&
2260 png_get_uint_32(profile
+96) == png_sRGB_checks
[i
].md5
[3])
2262 /* This may be one of the old HP profiles without an MD5, in that
2263 * case we can only use the length and Adler32 (note that these
2264 * are not used by default if there is an MD5!)
2266 # if PNG_sRGB_PROFILE_CHECKS == 0
2267 if (png_sRGB_checks
[i
].have_md5
!= 0)
2268 return 1+png_sRGB_checks
[i
].is_broken
;
2271 /* Profile is unsigned or more checks have been configured in. */
2274 length
= png_get_uint_32(profile
);
2275 intent
= png_get_uint_32(profile
+64);
2278 /* Length *and* intent must match */
2279 if (length
== png_sRGB_checks
[i
].length
&&
2280 intent
== (png_uint_32
) png_sRGB_checks
[i
].intent
)
2282 /* Now calculate the adler32 if not done already. */
2285 adler
= adler32(0, NULL
, 0);
2286 adler
= adler32(adler
, profile
, length
);
2289 if (adler
== png_sRGB_checks
[i
].adler
)
2291 /* These basic checks suggest that the data has not been
2292 * modified, but if the check level is more than 1 perform
2293 * our own crc32 checksum on the data.
2295 # if PNG_sRGB_PROFILE_CHECKS > 1
2298 crc
= crc32(0, NULL
, 0);
2299 crc
= crc32(crc
, profile
, length
);
2302 /* So this check must pass for the 'return' below to happen.
2304 if (crc
== png_sRGB_checks
[i
].crc
)
2307 if (png_sRGB_checks
[i
].is_broken
!= 0)
2309 /* These profiles are known to have bad data that may cause
2310 * problems if they are used, therefore attempt to
2311 * discourage their use, skip the 'have_md5' warning below,
2312 * which is made irrelevant by this error.
2314 png_chunk_report(png_ptr
, "known incorrect sRGB profile",
2318 /* Warn that this being done; this isn't even an error since
2319 * the profile is perfectly valid, but it would be nice if
2320 * people used the up-to-date ones.
2322 else if (png_sRGB_checks
[i
].have_md5
== 0)
2324 png_chunk_report(png_ptr
,
2325 "out-of-date sRGB profile with no signature",
2329 return 1+png_sRGB_checks
[i
].is_broken
;
2333 # if PNG_sRGB_PROFILE_CHECKS > 0
2334 /* The signature matched, but the profile had been changed in some
2335 * way. This probably indicates a data error or uninformed hacking.
2336 * Fall through to "no match".
2338 png_chunk_report(png_ptr
,
2339 "Not recognizing known sRGB profile that has been edited",
2347 return 0; /* no match */
2349 #endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */
2352 png_icc_set_sRGB(png_const_structrp png_ptr
,
2353 png_colorspacerp colorspace
, png_const_bytep profile
, uLong adler
)
2355 /* Is this profile one of the known ICC sRGB profiles? If it is, just set
2356 * the sRGB information.
2358 #if PNG_sRGB_PROFILE_CHECKS >= 0
2359 if (png_compare_ICC_profile_with_sRGB(png_ptr
, profile
, adler
) != 0)
2361 (void)png_colorspace_set_sRGB(png_ptr
, colorspace
,
2362 (int)/*already checked*/png_get_uint_32(profile
+64));
2367 png_colorspace_set_ICC(png_const_structrp png_ptr
, png_colorspacerp colorspace
,
2368 png_const_charp name
, png_uint_32 profile_length
, png_const_bytep profile
,
2371 if ((colorspace
->flags
& PNG_COLORSPACE_INVALID
) != 0)
2374 if (png_icc_check_length(png_ptr
, colorspace
, name
, profile_length
) != 0 &&
2375 png_icc_check_header(png_ptr
, colorspace
, name
, profile_length
, profile
,
2377 png_icc_check_tag_table(png_ptr
, colorspace
, name
, profile_length
,
2380 # ifdef PNG_sRGB_SUPPORTED
2381 /* If no sRGB support, don't try storing sRGB information */
2382 png_icc_set_sRGB(png_ptr
, colorspace
, profile
, 0);
2392 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2394 png_colorspace_set_rgb_coefficients(png_structrp png_ptr
)
2396 /* Set the rgb_to_gray coefficients from the colorspace. */
2397 if (png_ptr
->rgb_to_gray_coefficients_set
== 0 &&
2398 (png_ptr
->colorspace
.flags
& PNG_COLORSPACE_HAVE_ENDPOINTS
) != 0)
2400 /* png_set_background has not been called, get the coefficients from the Y
2401 * values of the colorspace colorants.
2403 png_fixed_point r
= png_ptr
->colorspace
.end_points_XYZ
.red_Y
;
2404 png_fixed_point g
= png_ptr
->colorspace
.end_points_XYZ
.green_Y
;
2405 png_fixed_point b
= png_ptr
->colorspace
.end_points_XYZ
.blue_Y
;
2406 png_fixed_point total
= r
+g
+b
;
2409 r
>= 0 && png_muldiv(&r
, r
, 32768, total
) && r
>= 0 && r
<= 32768 &&
2410 g
>= 0 && png_muldiv(&g
, g
, 32768, total
) && g
>= 0 && g
<= 32768 &&
2411 b
>= 0 && png_muldiv(&b
, b
, 32768, total
) && b
>= 0 && b
<= 32768 &&
2414 /* We allow 0 coefficients here. r+g+b may be 32769 if two or
2415 * all of the coefficients were rounded up. Handle this by
2416 * reducing the *largest* coefficient by 1; this matches the
2417 * approach used for the default coefficients in pngrtran.c
2423 else if (r
+g
+b
< 32768)
2428 if (g
>= r
&& g
>= b
)
2430 else if (r
>= g
&& r
>= b
)
2436 /* Check for an internal error. */
2439 "internal error handling cHRM coefficients");
2443 png_ptr
->rgb_to_gray_red_coeff
= (png_uint_16
)r
;
2444 png_ptr
->rgb_to_gray_green_coeff
= (png_uint_16
)g
;
2448 /* This is a png_error at present even though it could be ignored -
2449 * it should never happen, but it is important that if it does, the
2453 png_error(png_ptr
, "internal error handling cHRM->XYZ");
2456 #endif /* READ_RGB_TO_GRAY */
2458 #endif /* COLORSPACE */
2461 /* This exists solely to work round a warning from GNU C. */
2462 static int /* PRIVATE */
2463 png_gt(size_t a
, size_t b
)
2468 # define png_gt(a,b) ((a) > (b))
2472 png_check_IHDR(png_const_structrp png_ptr
,
2473 png_uint_32 width
, png_uint_32 height
, int bit_depth
,
2474 int color_type
, int interlace_type
, int compression_type
,
2479 /* Check for width and height valid values */
2482 png_warning(png_ptr
, "Image width is zero in IHDR");
2486 if (width
> PNG_UINT_31_MAX
)
2488 png_warning(png_ptr
, "Invalid image width in IHDR");
2492 if (png_gt(((width
+ 7) & (~7)),
2494 - 48 /* big_row_buf hack */
2495 - 1) /* filter byte */
2496 / 8) /* 8-byte RGBA pixels */
2497 - 1)) /* extra max_pixel_depth pad */
2499 /* The size of the row must be within the limits of this architecture.
2500 * Because the read code can perform arbitrary transformations the
2501 * maximum size is checked here. Because the code in png_read_start_row
2502 * adds extra space "for safety's sake" in several places a conservative
2503 * limit is used here.
2505 * NOTE: it would be far better to check the size that is actually used,
2506 * but the effect in the real world is minor and the changes are more
2507 * extensive, therefore much more dangerous and much more difficult to
2508 * write in a way that avoids compiler warnings.
2510 png_warning(png_ptr
, "Image width is too large for this architecture");
2514 #ifdef PNG_SET_USER_LIMITS_SUPPORTED
2515 if (width
> png_ptr
->user_width_max
)
2517 if (width
> PNG_USER_WIDTH_MAX
)
2520 png_warning(png_ptr
, "Image width exceeds user limit in IHDR");
2526 png_warning(png_ptr
, "Image height is zero in IHDR");
2530 if (height
> PNG_UINT_31_MAX
)
2532 png_warning(png_ptr
, "Invalid image height in IHDR");
2536 #ifdef PNG_SET_USER_LIMITS_SUPPORTED
2537 if (height
> png_ptr
->user_height_max
)
2539 if (height
> PNG_USER_HEIGHT_MAX
)
2542 png_warning(png_ptr
, "Image height exceeds user limit in IHDR");
2546 /* Check other values */
2547 if (bit_depth
!= 1 && bit_depth
!= 2 && bit_depth
!= 4 &&
2548 bit_depth
!= 8 && bit_depth
!= 16)
2550 png_warning(png_ptr
, "Invalid bit depth in IHDR");
2554 if (color_type
< 0 || color_type
== 1 ||
2555 color_type
== 5 || color_type
> 6)
2557 png_warning(png_ptr
, "Invalid color type in IHDR");
2561 if (((color_type
== PNG_COLOR_TYPE_PALETTE
) && bit_depth
> 8) ||
2562 ((color_type
== PNG_COLOR_TYPE_RGB
||
2563 color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
||
2564 color_type
== PNG_COLOR_TYPE_RGB_ALPHA
) && bit_depth
< 8))
2566 png_warning(png_ptr
, "Invalid color type/bit depth combination in IHDR");
2570 if (interlace_type
>= PNG_INTERLACE_LAST
)
2572 png_warning(png_ptr
, "Unknown interlace method in IHDR");
2576 if (compression_type
!= PNG_COMPRESSION_TYPE_BASE
)
2578 png_warning(png_ptr
, "Unknown compression method in IHDR");
2582 #ifdef PNG_MNG_FEATURES_SUPPORTED
2583 /* Accept filter_method 64 (intrapixel differencing) only if
2584 * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
2585 * 2. Libpng did not read a PNG signature (this filter_method is only
2586 * used in PNG datastreams that are embedded in MNG datastreams) and
2587 * 3. The application called png_permit_mng_features with a mask that
2588 * included PNG_FLAG_MNG_FILTER_64 and
2589 * 4. The filter_method is 64 and
2590 * 5. The color_type is RGB or RGBA
2592 if ((png_ptr
->mode
& PNG_HAVE_PNG_SIGNATURE
) != 0 &&
2593 png_ptr
->mng_features_permitted
!= 0)
2594 png_warning(png_ptr
, "MNG features are not allowed in a PNG datastream");
2596 if (filter_type
!= PNG_FILTER_TYPE_BASE
)
2598 if (!((png_ptr
->mng_features_permitted
& PNG_FLAG_MNG_FILTER_64
) != 0 &&
2599 (filter_type
== PNG_INTRAPIXEL_DIFFERENCING
) &&
2600 ((png_ptr
->mode
& PNG_HAVE_PNG_SIGNATURE
) == 0) &&
2601 (color_type
== PNG_COLOR_TYPE_RGB
||
2602 color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)))
2604 png_warning(png_ptr
, "Unknown filter method in IHDR");
2608 if ((png_ptr
->mode
& PNG_HAVE_PNG_SIGNATURE
) != 0)
2610 png_warning(png_ptr
, "Invalid filter method in IHDR");
2616 if (filter_type
!= PNG_FILTER_TYPE_BASE
)
2618 png_warning(png_ptr
, "Unknown filter method in IHDR");
2624 png_error(png_ptr
, "Invalid IHDR data");
2627 #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
2628 /* ASCII to fp functions */
2629 /* Check an ASCII formated floating point value, see the more detailed
2630 * comments in pngpriv.h
2632 /* The following is used internally to preserve the sticky flags */
2633 #define png_fp_add(state, flags) ((state) |= (flags))
2634 #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
2637 png_check_fp_number(png_const_charp string
, png_size_t size
, int *statep
,
2638 png_size_tp whereami
)
2640 int state
= *statep
;
2641 png_size_t i
= *whereami
;
2646 /* First find the type of the next character */
2649 case 43: type
= PNG_FP_SAW_SIGN
; break;
2650 case 45: type
= PNG_FP_SAW_SIGN
+ PNG_FP_NEGATIVE
; break;
2651 case 46: type
= PNG_FP_SAW_DOT
; break;
2652 case 48: type
= PNG_FP_SAW_DIGIT
; break;
2653 case 49: case 50: case 51: case 52:
2654 case 53: case 54: case 55: case 56:
2655 case 57: type
= PNG_FP_SAW_DIGIT
+ PNG_FP_NONZERO
; break;
2657 case 101: type
= PNG_FP_SAW_E
; break;
2658 default: goto PNG_FP_End
;
2661 /* Now deal with this type according to the current
2662 * state, the type is arranged to not overlap the
2663 * bits of the PNG_FP_STATE.
2665 switch ((state
& PNG_FP_STATE
) + (type
& PNG_FP_SAW_ANY
))
2667 case PNG_FP_INTEGER
+ PNG_FP_SAW_SIGN
:
2668 if ((state
& PNG_FP_SAW_ANY
) != 0)
2669 goto PNG_FP_End
; /* not a part of the number */
2671 png_fp_add(state
, type
);
2674 case PNG_FP_INTEGER
+ PNG_FP_SAW_DOT
:
2675 /* Ok as trailer, ok as lead of fraction. */
2676 if ((state
& PNG_FP_SAW_DOT
) != 0) /* two dots */
2679 else if ((state
& PNG_FP_SAW_DIGIT
) != 0) /* trailing dot? */
2680 png_fp_add(state
, type
);
2683 png_fp_set(state
, PNG_FP_FRACTION
| type
);
2687 case PNG_FP_INTEGER
+ PNG_FP_SAW_DIGIT
:
2688 if ((state
& PNG_FP_SAW_DOT
) != 0) /* delayed fraction */
2689 png_fp_set(state
, PNG_FP_FRACTION
| PNG_FP_SAW_DOT
);
2691 png_fp_add(state
, type
| PNG_FP_WAS_VALID
);
2695 case PNG_FP_INTEGER
+ PNG_FP_SAW_E
:
2696 if ((state
& PNG_FP_SAW_DIGIT
) == 0)
2699 png_fp_set(state
, PNG_FP_EXPONENT
);
2703 /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
2704 goto PNG_FP_End; ** no sign in fraction */
2706 /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
2707 goto PNG_FP_End; ** Because SAW_DOT is always set */
2709 case PNG_FP_FRACTION
+ PNG_FP_SAW_DIGIT
:
2710 png_fp_add(state
, type
| PNG_FP_WAS_VALID
);
2713 case PNG_FP_FRACTION
+ PNG_FP_SAW_E
:
2714 /* This is correct because the trailing '.' on an
2715 * integer is handled above - so we can only get here
2716 * with the sequence ".E" (with no preceding digits).
2718 if ((state
& PNG_FP_SAW_DIGIT
) == 0)
2721 png_fp_set(state
, PNG_FP_EXPONENT
);
2725 case PNG_FP_EXPONENT
+ PNG_FP_SAW_SIGN
:
2726 if ((state
& PNG_FP_SAW_ANY
) != 0)
2727 goto PNG_FP_End
; /* not a part of the number */
2729 png_fp_add(state
, PNG_FP_SAW_SIGN
);
2733 /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
2736 case PNG_FP_EXPONENT
+ PNG_FP_SAW_DIGIT
:
2737 png_fp_add(state
, PNG_FP_SAW_DIGIT
| PNG_FP_WAS_VALID
);
2741 /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
2744 default: goto PNG_FP_End
; /* I.e. break 2 */
2747 /* The character seems ok, continue. */
2752 /* Here at the end, update the state and return the correct
2758 return (state
& PNG_FP_SAW_DIGIT
) != 0;
2762 /* The same but for a complete string. */
2764 png_check_fp_string(png_const_charp string
, png_size_t size
)
2767 png_size_t char_index
=0;
2769 if (png_check_fp_number(string
, size
, &state
, &char_index
) != 0 &&
2770 (char_index
== size
|| string
[char_index
] == 0))
2771 return state
/* must be non-zero - see above */;
2773 return 0; /* i.e. fail */
2775 #endif /* pCAL || sCAL */
2777 #ifdef PNG_sCAL_SUPPORTED
2778 # ifdef PNG_FLOATING_POINT_SUPPORTED
2779 /* Utility used below - a simple accurate power of ten from an integral
2783 png_pow10(int power
)
2788 /* Handle negative exponent with a reciprocal at the end because
2789 * 10 is exact whereas .1 is inexact in base 2
2793 if (power
< DBL_MIN_10_EXP
) return 0;
2794 recip
= 1, power
= -power
;
2799 /* Decompose power bitwise. */
2803 if (power
& 1) d
*= mult
;
2809 if (recip
!= 0) d
= 1/d
;
2811 /* else power is 0 and d is 1 */
2816 /* Function to format a floating point value in ASCII with a given
2820 png_ascii_from_fp(png_const_structrp png_ptr
, png_charp ascii
, png_size_t size
,
2821 double fp
, unsigned int precision
)
2823 /* We use standard functions from math.h, but not printf because
2824 * that would require stdio. The caller must supply a buffer of
2825 * sufficient size or we will png_error. The tests on size and
2826 * the space in ascii[] consumed are indicated below.
2829 precision
= DBL_DIG
;
2831 /* Enforce the limit of the implementation precision too. */
2832 if (precision
> DBL_DIG
+1)
2833 precision
= DBL_DIG
+1;
2835 /* Basic sanity checks */
2836 if (size
>= precision
+5) /* See the requirements below. */
2841 *ascii
++ = 45; /* '-' PLUS 1 TOTAL 1 */
2845 if (fp
>= DBL_MIN
&& fp
<= DBL_MAX
)
2847 int exp_b10
; /* A base 10 exponent */
2848 double base
; /* 10^exp_b10 */
2850 /* First extract a base 10 exponent of the number,
2851 * the calculation below rounds down when converting
2852 * from base 2 to base 10 (multiply by log10(2) -
2853 * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
2854 * be increased. Note that the arithmetic shift
2855 * performs a floor() unlike C arithmetic - using a
2856 * C multiply would break the following for negative
2859 (void)frexp(fp
, &exp_b10
); /* exponent to base 2 */
2861 exp_b10
= (exp_b10
* 77) >> 8; /* <= exponent to base 10 */
2863 /* Avoid underflow here. */
2864 base
= png_pow10(exp_b10
); /* May underflow */
2866 while (base
< DBL_MIN
|| base
< fp
)
2868 /* And this may overflow. */
2869 double test
= png_pow10(exp_b10
+1);
2871 if (test
<= DBL_MAX
)
2872 ++exp_b10
, base
= test
;
2878 /* Normalize fp and correct exp_b10, after this fp is in the
2879 * range [.1,1) and exp_b10 is both the exponent and the digit
2880 * *before* which the decimal point should be inserted
2881 * (starting with 0 for the first digit). Note that this
2882 * works even if 10^exp_b10 is out of range because of the
2883 * test on DBL_MAX above.
2886 while (fp
>= 1) fp
/= 10, ++exp_b10
;
2888 /* Because of the code above fp may, at this point, be
2889 * less than .1, this is ok because the code below can
2890 * handle the leading zeros this generates, so no attempt
2891 * is made to correct that here.
2895 unsigned int czero
, clead
, cdigits
;
2898 /* Allow up to two leading zeros - this will not lengthen
2899 * the number compared to using E-n.
2901 if (exp_b10
< 0 && exp_b10
> -3) /* PLUS 3 TOTAL 4 */
2903 czero
= -exp_b10
; /* PLUS 2 digits: TOTAL 3 */
2904 exp_b10
= 0; /* Dot added below before first output. */
2907 czero
= 0; /* No zeros to add */
2909 /* Generate the digit list, stripping trailing zeros and
2910 * inserting a '.' before a digit if the exponent is 0.
2912 clead
= czero
; /* Count of leading zeros */
2913 cdigits
= 0; /* Count of digits in list. */
2920 /* Use modf here, not floor and subtract, so that
2921 * the separation is done in one step. At the end
2922 * of the loop don't break the number into parts so
2923 * that the final digit is rounded.
2925 if (cdigits
+czero
+1 < precision
+clead
)
2934 /* Rounding up to 10, handle that here. */
2938 if (cdigits
== 0) --clead
;
2942 while (cdigits
> 0 && d
> 9)
2946 if (exp_b10
!= (-1))
2951 ch
= *--ascii
, ++size
;
2952 /* Advance exp_b10 to '1', so that the
2953 * decimal point happens after the
2960 d
= ch
- 47; /* I.e. 1+(ch-48) */
2963 /* Did we reach the beginning? If so adjust the
2964 * exponent but take into account the leading
2967 if (d
> 9) /* cdigits == 0 */
2969 if (exp_b10
== (-1))
2971 /* Leading decimal point (plus zeros?), if
2972 * we lose the decimal point here it must
2973 * be reentered below.
2978 ++size
, exp_b10
= 1;
2980 /* Else lost a leading zero, so 'exp_b10' is
2987 /* In all cases we output a '1' */
2992 fp
= 0; /* Guarantees termination below. */
2998 if (cdigits
== 0) ++clead
;
3002 /* Included embedded zeros in the digit count. */
3003 cdigits
+= czero
- clead
;
3008 /* exp_b10 == (-1) means we just output the decimal
3009 * place - after the DP don't adjust 'exp_b10' any
3012 if (exp_b10
!= (-1))
3014 if (exp_b10
== 0) *ascii
++ = 46, --size
;
3015 /* PLUS 1: TOTAL 4 */
3018 *ascii
++ = 48, --czero
;
3021 if (exp_b10
!= (-1))
3024 *ascii
++ = 46, --size
; /* counted above */
3028 *ascii
++ = (char)(48 + (int)d
), ++cdigits
;
3031 while (cdigits
+czero
< precision
+clead
&& fp
> DBL_MIN
);
3033 /* The total output count (max) is now 4+precision */
3035 /* Check for an exponent, if we don't need one we are
3036 * done and just need to terminate the string. At
3037 * this point exp_b10==(-1) is effectively if flag - it got
3038 * to '-1' because of the decrement after outputting
3039 * the decimal point above (the exponent required is
3042 if (exp_b10
>= (-1) && exp_b10
<= 2)
3044 /* The following only happens if we didn't output the
3045 * leading zeros above for negative exponent, so this
3046 * doesn't add to the digit requirement. Note that the
3047 * two zeros here can only be output if the two leading
3048 * zeros were *not* output, so this doesn't increase
3051 while (--exp_b10
>= 0) *ascii
++ = 48;
3055 /* Total buffer requirement (including the '\0') is
3056 * 5+precision - see check at the start.
3061 /* Here if an exponent is required, adjust size for
3062 * the digits we output but did not count. The total
3063 * digit output here so far is at most 1+precision - no
3064 * decimal point and no leading or trailing zeros have
3069 *ascii
++ = 69, --size
; /* 'E': PLUS 1 TOTAL 2+precision */
3071 /* The following use of an unsigned temporary avoids ambiguities in
3072 * the signed arithmetic on exp_b10 and permits GCC at least to do
3073 * better optimization.
3076 unsigned int uexp_b10
;
3080 *ascii
++ = 45, --size
; /* '-': PLUS 1 TOTAL 3+precision */
3081 uexp_b10
= -exp_b10
;
3089 while (uexp_b10
> 0)
3091 exponent
[cdigits
++] = (char)(48 + uexp_b10
% 10);
3096 /* Need another size check here for the exponent digits, so
3097 * this need not be considered above.
3101 while (cdigits
> 0) *ascii
++ = exponent
[--cdigits
];
3109 else if (!(fp
>= DBL_MIN
))
3111 *ascii
++ = 48; /* '0' */
3117 *ascii
++ = 105; /* 'i' */
3118 *ascii
++ = 110; /* 'n' */
3119 *ascii
++ = 102; /* 'f' */
3125 /* Here on buffer too small. */
3126 png_error(png_ptr
, "ASCII conversion buffer too small");
3129 # endif /* FLOATING_POINT */
3131 # ifdef PNG_FIXED_POINT_SUPPORTED
3132 /* Function to format a fixed point value in ASCII.
3135 png_ascii_from_fixed(png_const_structrp png_ptr
, png_charp ascii
,
3136 png_size_t size
, png_fixed_point fp
)
3138 /* Require space for 10 decimal digits, a decimal point, a minus sign and a
3139 * trailing \0, 13 characters:
3145 /* Avoid overflow here on the minimum integer. */
3147 *ascii
++ = 45, --size
, num
= -fp
;
3151 if (num
<= 0x80000000) /* else overflowed */
3153 unsigned int ndigits
= 0, first
= 16 /* flag value */;
3158 /* Split the low digit off num: */
3159 unsigned int tmp
= num
/10;
3161 digits
[ndigits
++] = (char)(48 + num
);
3162 /* Record the first non-zero digit, note that this is a number
3163 * starting at 1, it's not actually the array index.
3165 if (first
== 16 && num
> 0)
3172 while (ndigits
> 5) *ascii
++ = digits
[--ndigits
];
3173 /* The remaining digits are fractional digits, ndigits is '5' or
3174 * smaller at this point. It is certainly not zero. Check for a
3175 * non-zero fractional digit:
3180 *ascii
++ = 46; /* decimal point */
3181 /* ndigits may be <5 for small numbers, output leading zeros
3182 * then ndigits digits to first:
3185 while (ndigits
< i
) *ascii
++ = 48, --i
;
3186 while (ndigits
>= first
) *ascii
++ = digits
[--ndigits
];
3187 /* Don't output the trailing zeros! */
3193 /* And null terminate the string: */
3199 /* Here on buffer too small. */
3200 png_error(png_ptr
, "ASCII conversion buffer too small");
3202 # endif /* FIXED_POINT */
3205 #if defined(PNG_FLOATING_POINT_SUPPORTED) && \
3206 !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
3207 (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
3208 defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
3209 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
3210 (defined(PNG_sCAL_SUPPORTED) && \
3211 defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
3213 png_fixed(png_const_structrp png_ptr
, double fp
, png_const_charp text
)
3215 double r
= floor(100000 * fp
+ .5);
3217 if (r
> 2147483647. || r
< -2147483648.)
3218 png_fixed_error(png_ptr
, text
);
3220 # ifndef PNG_ERROR_TEXT_SUPPORTED
3224 return (png_fixed_point
)r
;
3228 #if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\
3229 defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
3230 /* muldiv functions */
3231 /* This API takes signed arguments and rounds the result to the nearest
3232 * integer (or, for a fixed point number - the standard argument - to
3233 * the nearest .00001). Overflow and divide by zero are signalled in
3234 * the result, a boolean - true on success, false on overflow.
3237 png_muldiv(png_fixed_point_p res
, png_fixed_point a
, png_int_32 times
,
3240 /* Return a * times / divisor, rounded. */
3243 if (a
== 0 || times
== 0)
3250 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3256 /* A png_fixed_point is a 32-bit integer. */
3257 if (r
<= 2147483647. && r
>= -2147483648.)
3259 *res
= (png_fixed_point
)r
;
3264 png_uint_32 A
, T
, D
;
3265 png_uint_32 s16
, s32
, s00
;
3268 negative
= 1, A
= -a
;
3273 negative
= !negative
, T
= -times
;
3278 negative
= !negative
, D
= -divisor
;
3282 /* Following can't overflow because the arguments only
3283 * have 31 bits each, however the result may be 32 bits.
3285 s16
= (A
>> 16) * (T
& 0xffff) +
3286 (A
& 0xffff) * (T
>> 16);
3287 /* Can't overflow because the a*times bit is only 30
3290 s32
= (A
>> 16) * (T
>> 16) + (s16
>> 16);
3291 s00
= (A
& 0xffff) * (T
& 0xffff);
3293 s16
= (s16
& 0xffff) << 16;
3299 if (s32
< D
) /* else overflow */
3301 /* s32.s00 is now the 64-bit product, do a standard
3302 * division, we know that s32 < D, so the maximum
3303 * required shift is 31.
3306 png_fixed_point result
= 0; /* NOTE: signed */
3308 while (--bitshift
>= 0)
3310 png_uint_32 d32
, d00
;
3313 d32
= D
>> (32-bitshift
), d00
= D
<< bitshift
;
3320 if (s00
< d00
) --s32
; /* carry */
3321 s32
-= d32
, s00
-= d00
, result
+= 1<<bitshift
;
3325 if (s32
== d32
&& s00
>= d00
)
3326 s32
= 0, s00
-= d00
, result
+= 1<<bitshift
;
3329 /* Handle the rounding. */
3330 if (s00
>= (D
>> 1))
3336 /* Check for overflow. */
3337 if ((negative
!= 0 && result
<= 0) ||
3338 (negative
== 0 && result
>= 0))
3350 #endif /* READ_GAMMA || INCH_CONVERSIONS */
3352 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
3353 /* The following is for when the caller doesn't much care about the
3357 png_muldiv_warn(png_const_structrp png_ptr
, png_fixed_point a
, png_int_32 times
,
3360 png_fixed_point result
;
3362 if (png_muldiv(&result
, a
, times
, divisor
) != 0)
3365 png_warning(png_ptr
, "fixed point overflow ignored");
3370 #ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */
3371 /* Calculate a reciprocal, return 0 on div-by-zero or overflow. */
3373 png_reciprocal(png_fixed_point a
)
3375 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3376 double r
= floor(1E10
/a
+.5);
3378 if (r
<= 2147483647. && r
>= -2147483648.)
3379 return (png_fixed_point
)r
;
3381 png_fixed_point res
;
3383 if (png_muldiv(&res
, 100000, 100000, a
) != 0)
3387 return 0; /* error/overflow */
3390 /* This is the shared test on whether a gamma value is 'significant' - whether
3391 * it is worth doing gamma correction.
3394 png_gamma_significant(png_fixed_point gamma_val
)
3396 return gamma_val
< PNG_FP_1
- PNG_GAMMA_THRESHOLD_FIXED
||
3397 gamma_val
> PNG_FP_1
+ PNG_GAMMA_THRESHOLD_FIXED
;
3401 #ifdef PNG_READ_GAMMA_SUPPORTED
3402 #ifdef PNG_16BIT_SUPPORTED
3403 /* A local convenience routine. */
3404 static png_fixed_point
3405 png_product2(png_fixed_point a
, png_fixed_point b
)
3407 /* The required result is 1/a * 1/b; the following preserves accuracy. */
3408 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3409 double r
= a
* 1E-5;
3413 if (r
<= 2147483647. && r
>= -2147483648.)
3414 return (png_fixed_point
)r
;
3416 png_fixed_point res
;
3418 if (png_muldiv(&res
, a
, b
, 100000) != 0)
3422 return 0; /* overflow */
3426 /* The inverse of the above. */
3428 png_reciprocal2(png_fixed_point a
, png_fixed_point b
)
3430 /* The required result is 1/a * 1/b; the following preserves accuracy. */
3431 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3432 if (a
!= 0 && b
!= 0)
3438 if (r
<= 2147483647. && r
>= -2147483648.)
3439 return (png_fixed_point
)r
;
3442 /* This may overflow because the range of png_fixed_point isn't symmetric,
3443 * but this API is only used for the product of file and screen gamma so it
3444 * doesn't matter that the smallest number it can produce is 1/21474, not
3447 png_fixed_point res
= png_product2(a
, b
);
3450 return png_reciprocal(res
);
3453 return 0; /* overflow */
3455 #endif /* READ_GAMMA */
3457 #ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */
3458 #ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
3459 /* Fixed point gamma.
3461 * The code to calculate the tables used below can be found in the shell script
3462 * contrib/tools/intgamma.sh
3464 * To calculate gamma this code implements fast log() and exp() calls using only
3465 * fixed point arithmetic. This code has sufficient precision for either 8-bit
3466 * or 16-bit sample values.
3468 * The tables used here were calculated using simple 'bc' programs, but C double
3469 * precision floating point arithmetic would work fine.
3472 * This is a table of -log(value/255)/log(2) for 'value' in the range 128 to
3473 * 255, so it's the base 2 logarithm of a normalized 8-bit floating point
3474 * mantissa. The numbers are 32-bit fractions.
3476 static const png_uint_32
3479 4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U,
3480 3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U,
3481 3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U,
3482 3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U,
3483 3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U,
3484 2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U,
3485 2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U,
3486 2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U,
3487 2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U,
3488 2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U,
3489 1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U,
3490 1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U,
3491 1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U,
3492 1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U,
3493 1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U,
3494 971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U,
3495 803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U,
3496 639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U,
3497 479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U,
3498 324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U,
3499 172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U,
3503 /* The following are the values for 16-bit tables - these work fine for the
3504 * 8-bit conversions but produce very slightly larger errors in the 16-bit
3505 * log (about 1.2 as opposed to 0.7 absolute error in the final value). To
3506 * use these all the shifts below must be adjusted appropriately.
3508 65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054,
3509 57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803,
3510 50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068,
3511 43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782,
3512 37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887,
3513 31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339,
3514 25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098,
3515 20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132,
3516 15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415,
3517 10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523,
3518 6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495,
3524 png_log8bit(unsigned int x
)
3526 unsigned int lg2
= 0;
3527 /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log,
3528 * because the log is actually negate that means adding 1. The final
3529 * returned value thus has the range 0 (for 255 input) to 7.994 (for 1
3530 * input), return -1 for the overflow (log 0) case, - so the result is
3531 * always at most 19 bits.
3533 if ((x
&= 0xff) == 0)
3536 if ((x
& 0xf0) == 0)
3539 if ((x
& 0xc0) == 0)
3542 if ((x
& 0x80) == 0)
3545 /* result is at most 19 bits, so this cast is safe: */
3546 return (png_int_32
)((lg2
<< 16) + ((png_8bit_l2
[x
-128]+32768)>>16));
3549 /* The above gives exact (to 16 binary places) log2 values for 8-bit images,
3550 * for 16-bit images we use the most significant 8 bits of the 16-bit value to
3551 * get an approximation then multiply the approximation by a correction factor
3552 * determined by the remaining up to 8 bits. This requires an additional step
3553 * in the 16-bit case.
3555 * We want log2(value/65535), we have log2(v'/255), where:
3557 * value = v' * 256 + v''
3560 * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128
3561 * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less
3562 * than 258. The final factor also needs to correct for the fact that our 8-bit
3563 * value is scaled by 255, whereas the 16-bit values must be scaled by 65535.
3565 * This gives a final formula using a calculated value 'x' which is value/v' and
3566 * scaling by 65536 to match the above table:
3568 * log2(x/257) * 65536
3570 * Since these numbers are so close to '1' we can use simple linear
3571 * interpolation between the two end values 256/257 (result -368.61) and 258/257
3572 * (result 367.179). The values used below are scaled by a further 64 to give
3573 * 16-bit precision in the interpolation:
3575 * Start (256): -23591
3579 #ifdef PNG_16BIT_SUPPORTED
3581 png_log16bit(png_uint_32 x
)
3583 unsigned int lg2
= 0;
3585 /* As above, but now the input has 16 bits. */
3586 if ((x
&= 0xffff) == 0)
3589 if ((x
& 0xff00) == 0)
3592 if ((x
& 0xf000) == 0)
3595 if ((x
& 0xc000) == 0)
3598 if ((x
& 0x8000) == 0)
3601 /* Calculate the base logarithm from the top 8 bits as a 28-bit fractional
3605 lg2
+= (png_8bit_l2
[(x
>>8)-128]+8) >> 4;
3607 /* Now we need to interpolate the factor, this requires a division by the top
3608 * 8 bits. Do this with maximum precision.
3610 x
= ((x
<< 16) + (x
>> 9)) / (x
>> 8);
3612 /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24,
3613 * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly
3614 * 16 bits to interpolate to get the low bits of the result. Round the
3615 * answer. Note that the end point values are scaled by 64 to retain overall
3616 * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust
3617 * the overall scaling by 6-12. Round at every step.
3621 if (x
<= 65536U) /* <= '257' */
3622 lg2
+= ((23591U * (65536U-x
)) + (1U << (16+6-12-1))) >> (16+6-12);
3625 lg2
-= ((23499U * (x
-65536U)) + (1U << (16+6-12-1))) >> (16+6-12);
3627 /* Safe, because the result can't have more than 20 bits: */
3628 return (png_int_32
)((lg2
+ 2048) >> 12);
3632 /* The 'exp()' case must invert the above, taking a 20-bit fixed point
3633 * logarithmic value and returning a 16 or 8-bit number as appropriate. In
3634 * each case only the low 16 bits are relevant - the fraction - since the
3635 * integer bits (the top 4) simply determine a shift.
3637 * The worst case is the 16-bit distinction between 65535 and 65534. This
3638 * requires perhaps spurious accuracy in the decoding of the logarithm to
3639 * distinguish log2(65535/65534.5) - 10^-5 or 17 bits. There is little chance
3640 * of getting this accuracy in practice.
3642 * To deal with this the following exp() function works out the exponent of the
3643 * frational part of the logarithm by using an accurate 32-bit value from the
3644 * top four fractional bits then multiplying in the remaining bits.
3646 static const png_uint_32
3649 /* NOTE: the first entry is deliberately set to the maximum 32-bit value. */
3650 4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U,
3651 3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U,
3652 2553802834U, 2445529972U, 2341847524U, 2242560872U
3655 /* Adjustment table; provided to explain the numbers in the code below. */
3657 for (i
=11;i
>=0;--i
){ print i
, " ", (1 - e(-(2^i
)/65536*l(2))) * 2^(32-i
), "\n"}
3658 11 44937.64284865548751208448
3659 10 45180.98734845585101160448
3660 9 45303.31936980687359311872
3661 8 45364.65110595323018870784
3662 7 45395.35850361789624614912
3663 6 45410.72259715102037508096
3664 5 45418.40724413220722311168
3665 4 45422.25021786898173001728
3666 3 45424.17186732298419044352
3667 2 45425.13273269940811464704
3668 1 45425.61317555035558641664
3669 0 45425.85339951654943850496
3673 png_exp(png_fixed_point x
)
3675 if (x
> 0 && x
<= 0xfffff) /* Else overflow or zero (underflow) */
3677 /* Obtain a 4-bit approximation */
3678 png_uint_32 e
= png_32bit_exp
[(x
>> 12) & 0xf];
3680 /* Incorporate the low 12 bits - these decrease the returned value by
3681 * multiplying by a number less than 1 if the bit is set. The multiplier
3682 * is determined by the above table and the shift. Notice that the values
3683 * converge on 45426 and this is used to allow linear interpolation of the
3687 e
-= (((e
>> 16) * 44938U) + 16U) >> 5;
3690 e
-= (((e
>> 16) * 45181U) + 32U) >> 6;
3693 e
-= (((e
>> 16) * 45303U) + 64U) >> 7;
3696 e
-= (((e
>> 16) * 45365U) + 128U) >> 8;
3699 e
-= (((e
>> 16) * 45395U) + 256U) >> 9;
3702 e
-= (((e
>> 16) * 45410U) + 512U) >> 10;
3704 /* And handle the low 6 bits in a single block. */
3705 e
-= (((e
>> 16) * 355U * (x
& 0x3fU
)) + 256U) >> 9;
3707 /* Handle the upper bits of x. */
3712 /* Check for overflow */
3714 return png_32bit_exp
[0];
3716 /* Else underflow */
3721 png_exp8bit(png_fixed_point lg2
)
3723 /* Get a 32-bit value: */
3724 png_uint_32 x
= png_exp(lg2
);
3726 /* Convert the 32-bit value to 0..255 by multiplying by 256-1. Note that the
3727 * second, rounding, step can't overflow because of the first, subtraction,
3731 return (png_byte
)(((x
+ 0x7fffffU
) >> 24) & 0xff);
3734 #ifdef PNG_16BIT_SUPPORTED
3736 png_exp16bit(png_fixed_point lg2
)
3738 /* Get a 32-bit value: */
3739 png_uint_32 x
= png_exp(lg2
);
3741 /* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */
3743 return (png_uint_16
)((x
+ 32767U) >> 16);
3746 #endif /* FLOATING_ARITHMETIC */
3749 png_gamma_8bit_correct(unsigned int value
, png_fixed_point gamma_val
)
3751 if (value
> 0 && value
< 255)
3753 # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3754 /* 'value' is unsigned, ANSI-C90 requires the compiler to correctly
3755 * convert this to a floating point value. This includes values that
3756 * would overflow if 'value' were to be converted to 'int'.
3758 * Apparently GCC, however, does an intermediate conversion to (int)
3759 * on some (ARM) but not all (x86) platforms, possibly because of
3760 * hardware FP limitations. (E.g. if the hardware conversion always
3761 * assumes the integer register contains a signed value.) This results
3762 * in ANSI-C undefined behavior for large values.
3764 * Other implementations on the same machine might actually be ANSI-C90
3765 * conformant and therefore compile spurious extra code for the large
3768 * We can be reasonably sure that an unsigned to float conversion
3769 * won't be faster than an int to float one. Therefore this code
3770 * assumes responsibility for the undefined behavior, which it knows
3771 * can't happen because of the check above.
3773 * Note the argument to this routine is an (unsigned int) because, on
3774 * 16-bit platforms, it is assigned a value which might be out of
3775 * range for an (int); that would result in undefined behavior in the
3776 * caller if the *argument* ('value') were to be declared (int).
3778 double r
= floor(255*pow((int)/*SAFE*/value
/255.,gamma_val
*.00001)+.5);
3781 png_int_32 lg2
= png_log8bit(value
);
3782 png_fixed_point res
;
3784 if (png_muldiv(&res
, gamma_val
, lg2
, PNG_FP_1
) != 0)
3785 return png_exp8bit(res
);
3792 return (png_byte
)(value
& 0xff);
3795 #ifdef PNG_16BIT_SUPPORTED
3797 png_gamma_16bit_correct(unsigned int value
, png_fixed_point gamma_val
)
3799 if (value
> 0 && value
< 65535)
3801 # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3802 /* The same (unsigned int)->(double) constraints apply here as above,
3803 * however in this case the (unsigned int) to (int) conversion can
3804 * overflow on an ANSI-C90 compliant system so the cast needs to ensure
3805 * that this is not possible.
3807 double r
= floor(65535*pow((png_int_32
)value
/65535.,
3808 gamma_val
*.00001)+.5);
3809 return (png_uint_16
)r
;
3811 png_int_32 lg2
= png_log16bit(value
);
3812 png_fixed_point res
;
3814 if (png_muldiv(&res
, gamma_val
, lg2
, PNG_FP_1
) != 0)
3815 return png_exp16bit(res
);
3822 return (png_uint_16
)value
;
3826 /* This does the right thing based on the bit_depth field of the
3827 * png_struct, interpreting values as 8-bit or 16-bit. While the result
3828 * is nominally a 16-bit value if bit depth is 8 then the result is
3829 * 8-bit (as are the arguments.)
3831 png_uint_16
/* PRIVATE */
3832 png_gamma_correct(png_structrp png_ptr
, unsigned int value
,
3833 png_fixed_point gamma_val
)
3835 if (png_ptr
->bit_depth
== 8)
3836 return png_gamma_8bit_correct(value
, gamma_val
);
3838 #ifdef PNG_16BIT_SUPPORTED
3840 return png_gamma_16bit_correct(value
, gamma_val
);
3842 /* should not reach this */
3847 #ifdef PNG_16BIT_SUPPORTED
3848 /* Internal function to build a single 16-bit table - the table consists of
3849 * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount
3850 * to shift the input values right (or 16-number_of_signifiant_bits).
3852 * The caller is responsible for ensuring that the table gets cleaned up on
3853 * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument
3854 * should be somewhere that will be cleaned.
3857 png_build_16bit_table(png_structrp png_ptr
, png_uint_16pp
*ptable
,
3858 PNG_CONST
unsigned int shift
, PNG_CONST png_fixed_point gamma_val
)
3860 /* Various values derived from 'shift': */
3861 PNG_CONST
unsigned int num
= 1U << (8U - shift
);
3862 #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3863 /* CSE the division and work round wacky GCC warnings (see the comments
3864 * in png_gamma_8bit_correct for where these come from.)
3866 PNG_CONST
double fmax
= 1./(((png_int_32
)1 << (16U - shift
))-1);
3868 PNG_CONST
unsigned int max
= (1U << (16U - shift
))-1U;
3869 PNG_CONST
unsigned int max_by_2
= 1U << (15U-shift
);
3872 png_uint_16pp table
= *ptable
=
3873 (png_uint_16pp
)png_calloc(png_ptr
, num
* (sizeof (png_uint_16p
)));
3875 for (i
= 0; i
< num
; i
++)
3877 png_uint_16p sub_table
= table
[i
] =
3878 (png_uint_16p
)png_malloc(png_ptr
, 256 * (sizeof (png_uint_16
)));
3880 /* The 'threshold' test is repeated here because it can arise for one of
3881 * the 16-bit tables even if the others don't hit it.
3883 if (png_gamma_significant(gamma_val
) != 0)
3885 /* The old code would overflow at the end and this would cause the
3886 * 'pow' function to return a result >1, resulting in an
3887 * arithmetic error. This code follows the spec exactly; ig is
3888 * the recovered input sample, it always has 8-16 bits.
3890 * We want input * 65535/max, rounded, the arithmetic fits in 32
3891 * bits (unsigned) so long as max <= 32767.
3894 for (j
= 0; j
< 256; j
++)
3896 png_uint_32 ig
= (j
<< (8-shift
)) + i
;
3897 # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
3898 /* Inline the 'max' scaling operation: */
3899 /* See png_gamma_8bit_correct for why the cast to (int) is
3902 double d
= floor(65535.*pow(ig
*fmax
, gamma_val
*.00001)+.5);
3903 sub_table
[j
] = (png_uint_16
)d
;
3906 ig
= (ig
* 65535U + max_by_2
)/max
;
3908 sub_table
[j
] = png_gamma_16bit_correct(ig
, gamma_val
);
3914 /* We must still build a table, but do it the fast way. */
3917 for (j
= 0; j
< 256; j
++)
3919 png_uint_32 ig
= (j
<< (8-shift
)) + i
;
3922 ig
= (ig
* 65535U + max_by_2
)/max
;
3924 sub_table
[j
] = (png_uint_16
)ig
;
3930 /* NOTE: this function expects the *inverse* of the overall gamma transformation
3934 png_build_16to8_table(png_structrp png_ptr
, png_uint_16pp
*ptable
,
3935 PNG_CONST
unsigned int shift
, PNG_CONST png_fixed_point gamma_val
)
3937 PNG_CONST
unsigned int num
= 1U << (8U - shift
);
3938 PNG_CONST
unsigned int max
= (1U << (16U - shift
))-1U;
3942 png_uint_16pp table
= *ptable
=
3943 (png_uint_16pp
)png_calloc(png_ptr
, num
* (sizeof (png_uint_16p
)));
3945 /* 'num' is the number of tables and also the number of low bits of low
3946 * bits of the input 16-bit value used to select a table. Each table is
3947 * itself indexed by the high 8 bits of the value.
3949 for (i
= 0; i
< num
; i
++)
3950 table
[i
] = (png_uint_16p
)png_malloc(png_ptr
,
3951 256 * (sizeof (png_uint_16
)));
3953 /* 'gamma_val' is set to the reciprocal of the value calculated above, so
3954 * pow(out,g) is an *input* value. 'last' is the last input value set.
3956 * In the loop 'i' is used to find output values. Since the output is
3957 * 8-bit there are only 256 possible values. The tables are set up to
3958 * select the closest possible output value for each input by finding
3959 * the input value at the boundary between each pair of output values
3960 * and filling the table up to that boundary with the lower output
3963 * The boundary values are 0.5,1.5..253.5,254.5. Since these are 9-bit
3964 * values the code below uses a 16-bit value in i; the values start at
3965 * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last
3966 * entries are filled with 255). Start i at 128 and fill all 'last'
3967 * table entries <= 'max'
3970 for (i
= 0; i
< 255; ++i
) /* 8-bit output value */
3972 /* Find the corresponding maximum input value */
3973 png_uint_16 out
= (png_uint_16
)(i
* 257U); /* 16-bit output value */
3975 /* Find the boundary value in 16 bits: */
3976 png_uint_32 bound
= png_gamma_16bit_correct(out
+128U, gamma_val
);
3978 /* Adjust (round) to (16-shift) bits: */
3979 bound
= (bound
* max
+ 32768U)/65535U + 1U;
3981 while (last
< bound
)
3983 table
[last
& (0xffU
>> shift
)][last
>> (8U - shift
)] = out
;
3988 /* And fill in the final entries. */
3989 while (last
< (num
<< 8))
3991 table
[last
& (0xff >> shift
)][last
>> (8U - shift
)] = 65535U;
3997 /* Build a single 8-bit table: same as the 16-bit case but much simpler (and
3998 * typically much faster). Note that libpng currently does no sBIT processing
3999 * (apparently contrary to the spec) so a 256-entry table is always generated.
4002 png_build_8bit_table(png_structrp png_ptr
, png_bytepp ptable
,
4003 PNG_CONST png_fixed_point gamma_val
)
4006 png_bytep table
= *ptable
= (png_bytep
)png_malloc(png_ptr
, 256);
4008 if (png_gamma_significant(gamma_val
) != 0)
4009 for (i
=0; i
<256; i
++)
4010 table
[i
] = png_gamma_8bit_correct(i
, gamma_val
);
4013 for (i
=0; i
<256; ++i
)
4014 table
[i
] = (png_byte
)(i
& 0xff);
4017 /* Used from png_read_destroy and below to release the memory used by the gamma
4021 png_destroy_gamma_table(png_structrp png_ptr
)
4023 png_free(png_ptr
, png_ptr
->gamma_table
);
4024 png_ptr
->gamma_table
= NULL
;
4026 #ifdef PNG_16BIT_SUPPORTED
4027 if (png_ptr
->gamma_16_table
!= NULL
)
4030 int istop
= (1 << (8 - png_ptr
->gamma_shift
));
4031 for (i
= 0; i
< istop
; i
++)
4033 png_free(png_ptr
, png_ptr
->gamma_16_table
[i
]);
4035 png_free(png_ptr
, png_ptr
->gamma_16_table
);
4036 png_ptr
->gamma_16_table
= NULL
;
4040 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
4041 defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
4042 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
4043 png_free(png_ptr
, png_ptr
->gamma_from_1
);
4044 png_ptr
->gamma_from_1
= NULL
;
4045 png_free(png_ptr
, png_ptr
->gamma_to_1
);
4046 png_ptr
->gamma_to_1
= NULL
;
4048 #ifdef PNG_16BIT_SUPPORTED
4049 if (png_ptr
->gamma_16_from_1
!= NULL
)
4052 int istop
= (1 << (8 - png_ptr
->gamma_shift
));
4053 for (i
= 0; i
< istop
; i
++)
4055 png_free(png_ptr
, png_ptr
->gamma_16_from_1
[i
]);
4057 png_free(png_ptr
, png_ptr
->gamma_16_from_1
);
4058 png_ptr
->gamma_16_from_1
= NULL
;
4060 if (png_ptr
->gamma_16_to_1
!= NULL
)
4063 int istop
= (1 << (8 - png_ptr
->gamma_shift
));
4064 for (i
= 0; i
< istop
; i
++)
4066 png_free(png_ptr
, png_ptr
->gamma_16_to_1
[i
]);
4068 png_free(png_ptr
, png_ptr
->gamma_16_to_1
);
4069 png_ptr
->gamma_16_to_1
= NULL
;
4072 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
4075 /* We build the 8- or 16-bit gamma tables here. Note that for 16-bit
4076 * tables, we don't make a full table if we are reducing to 8-bit in
4077 * the future. Note also how the gamma_16 tables are segmented so that
4078 * we don't need to allocate > 64K chunks for a full 16-bit table.
4081 png_build_gamma_table(png_structrp png_ptr
, int bit_depth
)
4083 png_debug(1, "in png_build_gamma_table");
4085 /* Remove any existing table; this copes with multiple calls to
4086 * png_read_update_info. The warning is because building the gamma tables
4087 * multiple times is a performance hit - it's harmless but the ability to call
4088 * png_read_update_info() multiple times is new in 1.5.6 so it seems sensible
4089 * to warn if the app introduces such a hit.
4091 if (png_ptr
->gamma_table
!= NULL
|| png_ptr
->gamma_16_table
!= NULL
)
4093 png_warning(png_ptr
, "gamma table being rebuilt");
4094 png_destroy_gamma_table(png_ptr
);
4099 png_build_8bit_table(png_ptr
, &png_ptr
->gamma_table
,
4100 png_ptr
->screen_gamma
> 0 ? png_reciprocal2(png_ptr
->colorspace
.gamma
,
4101 png_ptr
->screen_gamma
) : PNG_FP_1
);
4103 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
4104 defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
4105 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
4106 if ((png_ptr
->transformations
& (PNG_COMPOSE
| PNG_RGB_TO_GRAY
)) != 0)
4108 png_build_8bit_table(png_ptr
, &png_ptr
->gamma_to_1
,
4109 png_reciprocal(png_ptr
->colorspace
.gamma
));
4111 png_build_8bit_table(png_ptr
, &png_ptr
->gamma_from_1
,
4112 png_ptr
->screen_gamma
> 0 ? png_reciprocal(png_ptr
->screen_gamma
) :
4113 png_ptr
->colorspace
.gamma
/* Probably doing rgb_to_gray */);
4115 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
4117 #ifdef PNG_16BIT_SUPPORTED
4120 png_byte shift
, sig_bit
;
4122 if ((png_ptr
->color_type
& PNG_COLOR_MASK_COLOR
) != 0)
4124 sig_bit
= png_ptr
->sig_bit
.red
;
4126 if (png_ptr
->sig_bit
.green
> sig_bit
)
4127 sig_bit
= png_ptr
->sig_bit
.green
;
4129 if (png_ptr
->sig_bit
.blue
> sig_bit
)
4130 sig_bit
= png_ptr
->sig_bit
.blue
;
4133 sig_bit
= png_ptr
->sig_bit
.gray
;
4135 /* 16-bit gamma code uses this equation:
4137 * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8]
4139 * Where 'iv' is the input color value and 'ov' is the output value -
4142 * Thus the gamma table consists of up to 256 256-entry tables. The table
4143 * is selected by the (8-gamma_shift) most significant of the low 8 bits of
4144 * the color value then indexed by the upper 8 bits:
4146 * table[low bits][high 8 bits]
4148 * So the table 'n' corresponds to all those 'iv' of:
4150 * <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1>
4153 if (sig_bit
> 0 && sig_bit
< 16U)
4154 /* shift == insignificant bits */
4155 shift
= (png_byte
)((16U - sig_bit
) & 0xff);
4158 shift
= 0; /* keep all 16 bits */
4160 if ((png_ptr
->transformations
& (PNG_16_TO_8
| PNG_SCALE_16_TO_8
)) != 0)
4162 /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
4163 * the significant bits in the *input* when the output will
4164 * eventually be 8 bits. By default it is 11.
4166 if (shift
< (16U - PNG_MAX_GAMMA_8
))
4167 shift
= (16U - PNG_MAX_GAMMA_8
);
4171 shift
= 8U; /* Guarantees at least one table! */
4173 png_ptr
->gamma_shift
= shift
;
4175 /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now
4176 * PNG_COMPOSE). This effectively smashed the background calculation for
4177 * 16-bit output because the 8-bit table assumes the result will be reduced
4180 if ((png_ptr
->transformations
& (PNG_16_TO_8
| PNG_SCALE_16_TO_8
)) != 0)
4181 png_build_16to8_table(png_ptr
, &png_ptr
->gamma_16_table
, shift
,
4182 png_ptr
->screen_gamma
> 0 ? png_product2(png_ptr
->colorspace
.gamma
,
4183 png_ptr
->screen_gamma
) : PNG_FP_1
);
4186 png_build_16bit_table(png_ptr
, &png_ptr
->gamma_16_table
, shift
,
4187 png_ptr
->screen_gamma
> 0 ? png_reciprocal2(png_ptr
->colorspace
.gamma
,
4188 png_ptr
->screen_gamma
) : PNG_FP_1
);
4190 #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
4191 defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
4192 defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
4193 if ((png_ptr
->transformations
& (PNG_COMPOSE
| PNG_RGB_TO_GRAY
)) != 0)
4195 png_build_16bit_table(png_ptr
, &png_ptr
->gamma_16_to_1
, shift
,
4196 png_reciprocal(png_ptr
->colorspace
.gamma
));
4198 /* Notice that the '16 from 1' table should be full precision, however
4199 * the lookup on this table still uses gamma_shift, so it can't be.
4202 png_build_16bit_table(png_ptr
, &png_ptr
->gamma_16_from_1
, shift
,
4203 png_ptr
->screen_gamma
> 0 ? png_reciprocal(png_ptr
->screen_gamma
) :
4204 png_ptr
->colorspace
.gamma
/* Probably doing rgb_to_gray */);
4206 #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
4210 #endif /* READ_GAMMA */
4212 /* HARDWARE OR SOFTWARE OPTION SUPPORT */
4213 #ifdef PNG_SET_OPTION_SUPPORTED
4215 png_set_option(png_structrp png_ptr
, int option
, int onoff
)
4217 if (png_ptr
!= NULL
&& option
>= 0 && option
< PNG_OPTION_NEXT
&&
4220 int mask
= 3 << option
;
4221 int setting
= (2 + (onoff
!= 0)) << option
;
4222 int current
= png_ptr
->options
;
4224 png_ptr
->options
= (png_byte
)(((current
& ~mask
) | setting
) & 0xff);
4226 return (current
& mask
) >> option
;
4229 return PNG_OPTION_INVALID
;
4234 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
4235 defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
4236 /* sRGB conversion tables; these are machine generated with the code in
4237 * contrib/tools/makesRGB.c. The actual sRGB transfer curve defined in the
4238 * specification (see the article at http://en.wikipedia.org/wiki/SRGB)
4239 * is used, not the gamma=1/2.2 approximation use elsewhere in libpng.
4240 * The sRGB to linear table is exact (to the nearest 16-bit linear fraction).
4241 * The inverse (linear to sRGB) table has accuracies as follows:
4243 * For all possible (255*65535+1) input values:
4245 * error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact
4247 * For the input values corresponding to the 65536 16-bit values:
4249 * error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact
4251 * In all cases the inexact readings are only off by one.
4254 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
4255 /* The convert-to-sRGB table is only currently required for read. */
4256 const png_uint_16 png_sRGB_table
[256] =
4258 0,20,40,60,80,99,119,139,
4259 159,179,199,219,241,264,288,313,
4260 340,367,396,427,458,491,526,562,
4261 599,637,677,718,761,805,851,898,
4262 947,997,1048,1101,1156,1212,1270,1330,
4263 1391,1453,1517,1583,1651,1720,1790,1863,
4264 1937,2013,2090,2170,2250,2333,2418,2504,
4265 2592,2681,2773,2866,2961,3058,3157,3258,
4266 3360,3464,3570,3678,3788,3900,4014,4129,
4267 4247,4366,4488,4611,4736,4864,4993,5124,
4268 5257,5392,5530,5669,5810,5953,6099,6246,
4269 6395,6547,6700,6856,7014,7174,7335,7500,
4270 7666,7834,8004,8177,8352,8528,8708,8889,
4271 9072,9258,9445,9635,9828,10022,10219,10417,
4272 10619,10822,11028,11235,11446,11658,11873,12090,
4273 12309,12530,12754,12980,13209,13440,13673,13909,
4274 14146,14387,14629,14874,15122,15371,15623,15878,
4275 16135,16394,16656,16920,17187,17456,17727,18001,
4276 18277,18556,18837,19121,19407,19696,19987,20281,
4277 20577,20876,21177,21481,21787,22096,22407,22721,
4278 23038,23357,23678,24002,24329,24658,24990,25325,
4279 25662,26001,26344,26688,27036,27386,27739,28094,
4280 28452,28813,29176,29542,29911,30282,30656,31033,
4281 31412,31794,32179,32567,32957,33350,33745,34143,
4282 34544,34948,35355,35764,36176,36591,37008,37429,
4283 37852,38278,38706,39138,39572,40009,40449,40891,
4284 41337,41785,42236,42690,43147,43606,44069,44534,
4285 45002,45473,45947,46423,46903,47385,47871,48359,
4286 48850,49344,49841,50341,50844,51349,51858,52369,
4287 52884,53401,53921,54445,54971,55500,56032,56567,
4288 57105,57646,58190,58737,59287,59840,60396,60955,
4289 61517,62082,62650,63221,63795,64372,64952,65535
4291 #endif /* SIMPLIFIED_READ */
4293 /* The base/delta tables are required for both read and write (but currently
4294 * only the simplified versions.)
4296 const png_uint_16 png_sRGB_base
[512] =
4298 128,1782,3383,4644,5675,6564,7357,8074,
4299 8732,9346,9921,10463,10977,11466,11935,12384,
4300 12816,13233,13634,14024,14402,14769,15125,15473,
4301 15812,16142,16466,16781,17090,17393,17690,17981,
4302 18266,18546,18822,19093,19359,19621,19879,20133,
4303 20383,20630,20873,21113,21349,21583,21813,22041,
4304 22265,22487,22707,22923,23138,23350,23559,23767,
4305 23972,24175,24376,24575,24772,24967,25160,25352,
4306 25542,25730,25916,26101,26284,26465,26645,26823,
4307 27000,27176,27350,27523,27695,27865,28034,28201,
4308 28368,28533,28697,28860,29021,29182,29341,29500,
4309 29657,29813,29969,30123,30276,30429,30580,30730,
4310 30880,31028,31176,31323,31469,31614,31758,31902,
4311 32045,32186,32327,32468,32607,32746,32884,33021,
4312 33158,33294,33429,33564,33697,33831,33963,34095,
4313 34226,34357,34486,34616,34744,34873,35000,35127,
4314 35253,35379,35504,35629,35753,35876,35999,36122,
4315 36244,36365,36486,36606,36726,36845,36964,37083,
4316 37201,37318,37435,37551,37668,37783,37898,38013,
4317 38127,38241,38354,38467,38580,38692,38803,38915,
4318 39026,39136,39246,39356,39465,39574,39682,39790,
4319 39898,40005,40112,40219,40325,40431,40537,40642,
4320 40747,40851,40955,41059,41163,41266,41369,41471,
4321 41573,41675,41777,41878,41979,42079,42179,42279,
4322 42379,42478,42577,42676,42775,42873,42971,43068,
4323 43165,43262,43359,43456,43552,43648,43743,43839,
4324 43934,44028,44123,44217,44311,44405,44499,44592,
4325 44685,44778,44870,44962,45054,45146,45238,45329,
4326 45420,45511,45601,45692,45782,45872,45961,46051,
4327 46140,46229,46318,46406,46494,46583,46670,46758,
4328 46846,46933,47020,47107,47193,47280,47366,47452,
4329 47538,47623,47709,47794,47879,47964,48048,48133,
4330 48217,48301,48385,48468,48552,48635,48718,48801,
4331 48884,48966,49048,49131,49213,49294,49376,49458,
4332 49539,49620,49701,49782,49862,49943,50023,50103,
4333 50183,50263,50342,50422,50501,50580,50659,50738,
4334 50816,50895,50973,51051,51129,51207,51285,51362,
4335 51439,51517,51594,51671,51747,51824,51900,51977,
4336 52053,52129,52205,52280,52356,52432,52507,52582,
4337 52657,52732,52807,52881,52956,53030,53104,53178,
4338 53252,53326,53400,53473,53546,53620,53693,53766,
4339 53839,53911,53984,54056,54129,54201,54273,54345,
4340 54417,54489,54560,54632,54703,54774,54845,54916,
4341 54987,55058,55129,55199,55269,55340,55410,55480,
4342 55550,55620,55689,55759,55828,55898,55967,56036,
4343 56105,56174,56243,56311,56380,56448,56517,56585,
4344 56653,56721,56789,56857,56924,56992,57059,57127,
4345 57194,57261,57328,57395,57462,57529,57595,57662,
4346 57728,57795,57861,57927,57993,58059,58125,58191,
4347 58256,58322,58387,58453,58518,58583,58648,58713,
4348 58778,58843,58908,58972,59037,59101,59165,59230,
4349 59294,59358,59422,59486,59549,59613,59677,59740,
4350 59804,59867,59930,59993,60056,60119,60182,60245,
4351 60308,60370,60433,60495,60558,60620,60682,60744,
4352 60806,60868,60930,60992,61054,61115,61177,61238,
4353 61300,61361,61422,61483,61544,61605,61666,61727,
4354 61788,61848,61909,61969,62030,62090,62150,62211,
4355 62271,62331,62391,62450,62510,62570,62630,62689,
4356 62749,62808,62867,62927,62986,63045,63104,63163,
4357 63222,63281,63340,63398,63457,63515,63574,63632,
4358 63691,63749,63807,63865,63923,63981,64039,64097,
4359 64155,64212,64270,64328,64385,64443,64500,64557,
4360 64614,64672,64729,64786,64843,64900,64956,65013,
4361 65070,65126,65183,65239,65296,65352,65409,65465
4364 const png_byte png_sRGB_delta
[512] =
4366 207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54,
4367 52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36,
4368 35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28,
4369 28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24,
4370 23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21,
4371 21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19,
4372 19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17,
4373 17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16,
4374 16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15,
4375 15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14,
4376 14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13,
4377 13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12,
4378 12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,
4379 12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11,
4380 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
4381 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
4382 11,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
4383 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
4384 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
4385 10,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
4386 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
4387 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
4388 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,
4389 9,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
4390 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
4391 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
4392 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
4393 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,
4394 8,8,8,8,8,8,8,8,8,7,7,7,7,7,7,7,
4395 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
4396 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
4397 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
4399 #endif /* SIMPLIFIED READ/WRITE sRGB support */
4401 /* SIMPLIFIED READ/WRITE SUPPORT */
4402 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
4403 defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
4405 png_image_free_function(png_voidp argument
)
4407 png_imagep image
= png_voidcast(png_imagep
, argument
);
4408 png_controlp cp
= image
->opaque
;
4411 /* Double check that we have a png_ptr - it should be impossible to get here
4414 if (cp
->png_ptr
== NULL
)
4417 /* First free any data held in the control structure. */
4418 # ifdef PNG_STDIO_SUPPORTED
4419 if (cp
->owned_file
!= 0)
4421 FILE *fp
= png_voidcast(FILE*, cp
->png_ptr
->io_ptr
);
4424 /* Ignore errors here. */
4427 cp
->png_ptr
->io_ptr
= NULL
;
4433 /* Copy the control structure so that the original, allocated, version can be
4434 * safely freed. Notice that a png_error here stops the remainder of the
4435 * cleanup, but this is probably fine because that would indicate bad memory
4440 png_free(c
.png_ptr
, cp
);
4442 /* Then the structures, calling the correct API. */
4443 if (c
.for_write
!= 0)
4445 # ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
4446 png_destroy_write_struct(&c
.png_ptr
, &c
.info_ptr
);
4448 png_error(c
.png_ptr
, "simplified write not supported");
4453 # ifdef PNG_SIMPLIFIED_READ_SUPPORTED
4454 png_destroy_read_struct(&c
.png_ptr
, &c
.info_ptr
, NULL
);
4456 png_error(c
.png_ptr
, "simplified read not supported");
4465 png_image_free(png_imagep image
)
4467 /* Safely call the real function, but only if doing so is safe at this point
4468 * (if not inside an error handling context). Otherwise assume
4469 * png_safe_execute will call this API after the return.
4471 if (image
!= NULL
&& image
->opaque
!= NULL
&&
4472 image
->opaque
->error_buf
== NULL
)
4474 /* Ignore errors here: */
4475 (void)png_safe_execute(image
, png_image_free_function
, image
);
4476 image
->opaque
= NULL
;
4481 png_image_error(png_imagep image
, png_const_charp error_message
)
4483 /* Utility to log an error. */
4484 png_safecat(image
->message
, (sizeof image
->message
), 0, error_message
);
4485 image
->warning_or_error
|= PNG_IMAGE_ERROR
;
4486 png_image_free(image
);
4490 #endif /* SIMPLIFIED READ/WRITE */
4491 #endif /* READ || WRITE */