/* png.c - location for general purpose libpng functions
*
* Copyright (c) 2018-2026 Cosmin Truta
* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
* Copyright (c) 1996-1997 Andreas Dilger
* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
#include "pngpriv.h"
/* Generate a compiler error if there is an old png.h in the search path. */
typedef png_libpng_version_1_6_58 Your_png_h_is_not_version_1_6_58;
/* Sanity check the chunks definitions - PNG_KNOWN_CHUNKS from pngpriv.h and the
* corresponding macro definitions. This causes a compile time failure if
* something is wrong but generates no code.
*
* (1) The first check is that the PNG_CHUNK(cHNK, index) 'index' values must
* increment from 0 to the last value.
*/
#define PNG_CHUNK(cHNK, index) != (index) || ((index)+
1)
#if 0 PNG_KNOWN_CHUNKS <
0
# error PNG_KNOWN_CHUNKS chunk definitions are
not in order
#endif
#undef PNG_CHUNK
/* (2) The chunk name macros, png_cHNK, must all be valid and defined. Since
* this is a preprocessor test undefined pp-tokens come out as zero and will
* fail this test.
*/
#define PNG_CHUNK(cHNK, index) !PNG_CHUNK_NAME_VALID(png_
## cHNK) ||
#if PNG_KNOWN_CHUNKS
0
# error png_cHNK
not defined for some known cHNK
#endif
#undef PNG_CHUNK
/* Tells libpng that we have already handled the first "num_bytes" bytes
* of the PNG file signature. If the PNG data is embedded into another
* stream we can set num_bytes = 8 so that libpng will not attempt to read
* or write any of the magic bytes before it starts on the IHDR.
*/
#ifdef PNG_READ_SUPPORTED
void PNGAPI
png_set_sig_bytes(png_structrp png_ptr,
int num_bytes)
{
unsigned int nb = (
unsigned int)num_bytes;
png_debug(
1,
"in png_set_sig_bytes");
if (png_ptr == NULL)
return;
if (num_bytes <
0)
nb =
0;
if (nb >
8)
png_error(png_ptr,
"Too many bytes for PNG signature");
png_ptr->sig_bytes = (png_byte)nb;
}
/* Checks whether the supplied bytes match the PNG signature. We allow
* checking less than the full 8-byte signature so that those apps that
* already read the first few bytes of a file to determine the file type
* can simply check the remaining bytes for extra assurance. Returns
* an integer less than, equal to, or greater than zero if sig is found,
* respectively, to be less than, to match, or be greater than the correct
* PNG signature (this is the same behavior as strcmp, memcmp, etc).
*/
int PNGAPI
png_sig_cmp(png_const_bytep sig, size_t start, size_t num_to_check)
{
static const png_byte png_signature[
8] = {
137,
80,
78,
71,
13,
10,
26,
10};
if (num_to_check >
8)
num_to_check =
8;
else if (num_to_check <
1)
return -
1;
if (start >
7)
return -
1;
if (start + num_to_check >
8)
num_to_check =
8 - start;
return memcmp(&sig[start], &png_signature[start], num_to_check);
}
#endif /* READ */
#if defined(PNG_READ_SUPPORTED) ||
defined(PNG_WRITE_SUPPORTED)
/* Function to allocate memory for zlib */
PNG_FUNCTION(voidpf
/* PRIVATE */,
png_zalloc,(voidpf png_ptr, uInt items, uInt size),
PNG_ALLOCATED)
{
png_alloc_size_t num_bytes = size;
if (png_ptr == NULL)
return NULL;
/* This check against overflow is vestigial, dating back from
* the old times when png_zalloc used to be an exported function.
* We're still keeping it here for now, as an extra-cautious
* prevention against programming errors inside zlib, although it
* should rather be a debug-time assertion instead.
*/
if (size !=
0 && items >= (~(png_alloc_size_t)
0) / size)
{
png_warning(png_voidcast(png_structrp, png_ptr),
"Potential overflow in png_zalloc()");
return NULL;
}
num_bytes *= items;
return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes);
}
/* Function to free memory for zlib */
void /* PRIVATE */
png_zfree(voidpf png_ptr, voidpf ptr)
{
png_free(png_voidcast(png_const_structrp,png_ptr), ptr);
}
/* Reset the CRC variable to 32 bits of 1's. Care must be taken
* in case CRC is > 32 bits to leave the top bits 0.
*/
void /* PRIVATE */
png_reset_crc(png_structrp png_ptr)
{
/* The cast is safe because the crc is a 32-bit value. */
png_ptr->crc = (png_uint_32)crc32(
0, Z_NULL,
0);
}
/* Calculate the CRC over a section of data. We can only pass as
* much data to this routine as the largest single buffer size. We
* also check that this data will actually be used before going to the
* trouble of calculating it.
*/
void /* PRIVATE */
png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, size_t length)
{
int need_crc =
1;
if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) !=
0)
{
if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
(PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
need_crc =
0;
}
else /* critical */
{
if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) !=
0)
need_crc =
0;
}
/* 'uLong' is defined in zlib.h as unsigned long; this means that on some
* systems it is a 64-bit value. crc32, however, returns 32 bits so the
* following cast is safe. 'uInt' may be no more than 16 bits, so it is
* necessary to perform a loop here.
*/
if (need_crc !=
0 && length >
0)
{
uLong crc = png_ptr->crc;
/* Should never issue a warning */
do
{
uInt safe_length = (uInt)length;
#ifndef __COVERITY__
if (safe_length ==
0)
safe_length = (uInt)-
1;
/* evil, but safe */
#endif
crc = crc32(crc, ptr, safe_length);
/* The following should never issue compiler warnings; if they do the
* target system has characteristics that will probably violate other
* assumptions within the libpng code.
*/
ptr += safe_length;
length -= safe_length;
}
while (length >
0);
/* And the following is always safe because the crc is only 32 bits. */
png_ptr->crc = (png_uint_32)crc;
}
}
/* Check a user supplied version number, called from both read and write
* functions that create a png_struct.
*/
int
png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)
{
/* Libpng versions 1.0.0 and later are binary compatible if the version
* string matches through the second '.'; we must recompile any
* applications that use any older library version.
*/
if (user_png_ver != NULL)
{
int i = -
1;
int found_dots =
0;
do
{
i++;
if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i])
png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
if (user_png_ver[i] ==
'.')
found_dots++;
}
while (found_dots <
2 && user_png_ver[i] !=
0 &&
PNG_LIBPNG_VER_STRING[i] !=
0);
}
else
png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
if ((png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH) !=
0)
{
#ifdef PNG_WARNINGS_SUPPORTED
size_t pos =
0;
char m[
128];
pos = png_safecat(m, (
sizeof m), pos,
"Application built with libpng-");
pos = png_safecat(m, (
sizeof m), pos, user_png_ver);
pos = png_safecat(m, (
sizeof m), pos,
" but running with ");
pos = png_safecat(m, (
sizeof m), pos, PNG_LIBPNG_VER_STRING);
PNG_UNUSED(pos)
png_warning(png_ptr, m);
#endif
return 0;
}
/* Success return. */
return 1;
}
/* Generic function to create a png_struct for either read or write - this
* contains the common initialization.
*/
PNG_FUNCTION(png_structp
/* PRIVATE */,
png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
png_malloc_ptr malloc_fn, png_free_ptr free_fn),
PNG_ALLOCATED)
{
png_struct create_struct;
# ifdef PNG_SETJMP_SUPPORTED
jmp_buf create_jmp_buf;
# endif
/* This temporary stack-allocated structure is used to provide a place to
* build enough context to allow the user provided memory allocator (if any)
* to be called.
*/
memset(&create_struct,
0, (
sizeof create_struct));
# ifdef PNG_USER_LIMITS_SUPPORTED
create_struct.user_width_max = PNG_USER_WIDTH_MAX;
create_struct.user_height_max = PNG_USER_HEIGHT_MAX;
# ifdef PNG_USER_CHUNK_CACHE_MAX
create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
# endif
# if PNG_USER_CHUNK_MALLOC_MAX >
0 /* default to compile-time limit */
create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
/* No compile-time limit, so initialize to the system limit: */
# elif
defined PNG_MAX_MALLOC_64K
/* legacy system limit */
create_struct.user_chunk_malloc_max =
65536U;
# else /* modern system limit SIZE_MAX (C99) */
create_struct.user_chunk_malloc_max = PNG_SIZE_MAX;
# endif
# endif
/* The following two API calls simply set fields in png_struct, so it is safe
* to do them now even though error handling is not yet set up.
*/
# ifdef PNG_USER_MEM_SUPPORTED
png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn);
# else
PNG_UNUSED(mem_ptr)
PNG_UNUSED(malloc_fn)
PNG_UNUSED(free_fn)
# endif
/* (*error_fn) can return control to the caller after the error_ptr is set,
* this will result in a memory leak unless the error_fn does something
* extremely sophisticated. The design lacks merit but is implicit in the
* API.
*/
png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn);
# ifdef PNG_SETJMP_SUPPORTED
if (!setjmp(create_jmp_buf))
# endif
{
# ifdef PNG_SETJMP_SUPPORTED
/* Temporarily fake out the longjmp information until we have
* successfully completed this function. This only works if we have
* setjmp() support compiled in, but it is safe - this stuff should
* never happen.
*/
create_struct.jmp_buf_ptr = &create_jmp_buf;
create_struct.jmp_buf_size =
0;
/*stack allocation*/
create_struct.longjmp_fn = longjmp;
# endif
/* Call the general version checker (shared with read and write code):
*/
if (png_user_version_check(&create_struct, user_png_ver) !=
0)
{
png_structrp png_ptr = png_voidcast(png_structrp,
png_malloc_warn(&create_struct, (
sizeof *png_ptr)));
if (png_ptr != NULL)
{
/* png_ptr->zstream holds a back-pointer to the png_struct, so
* this can only be done now:
*/
create_struct.zstream.zalloc = png_zalloc;
create_struct.zstream.zfree = png_zfree;
create_struct.zstream.opaque = png_ptr;
# ifdef PNG_SETJMP_SUPPORTED
/* Eliminate the local error handling: */
create_struct.jmp_buf_ptr = NULL;
create_struct.jmp_buf_size =
0;
create_struct.longjmp_fn =
0;
# endif
*png_ptr = create_struct;
/* This is the successful return point */
return png_ptr;
}
}
}
/* A longjmp because of a bug in the application storage allocator or a
* simple failure to allocate the png_struct.
*/
return NULL;
}
/* Allocate the memory for an info_struct for the application. */
PNG_FUNCTION(png_infop,PNGAPI
png_create_info_struct,(png_const_structrp png_ptr),
PNG_ALLOCATED)
{
png_inforp info_ptr;
png_debug(
1,
"in png_create_info_struct");
if (png_ptr == NULL)
return NULL;
/* Use the internal API that does not (or at least should not) error out, so
* that this call always returns ok. The application typically sets up the
* error handling *after* creating the info_struct because this is the way it
* has always been done in 'example.c'.
*/
info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,
(
sizeof *info_ptr)));
if (info_ptr != NULL)
memset(info_ptr,
0, (
sizeof *info_ptr));
return info_ptr;
}
/* This function frees the memory associated with a single info struct.
* Normally, one would use either png_destroy_read_struct() or
* png_destroy_write_struct() to free an info struct, but this may be
* useful for some applications. From libpng 1.6.0 this function is also used
* internally to implement the png_info release part of the 'struct' destroy
* APIs. This ensures that all possible approaches free the same data (all of
* it).
*/
void PNGAPI
png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)
{
png_inforp info_ptr = NULL;
png_debug(
1,
"in png_destroy_info_struct");
if (png_ptr == NULL)
return;
if (info_ptr_ptr != NULL)
info_ptr = *info_ptr_ptr;
if (info_ptr != NULL)
{
/* Do this first in case of an error below; if the app implements its own
* memory management this can lead to png_free calling png_error, which
* will abort this routine and return control to the app error handler.
* An infinite loop may result if it then tries to free the same info
* ptr.
*/
*info_ptr_ptr = NULL;
png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -
1);
memset(info_ptr,
0, (
sizeof *info_ptr));
png_free(png_ptr, info_ptr);
}
}
/* Initialize the info structure. This is now an internal function (0.89)
* and applications using it are urged to use png_create_info_struct()
* instead. Use deprecated in 1.6.0, internal use removed (used internally it
* is just a memset).
*
* NOTE: it is almost inconceivable that this API is used because it bypasses
* the user-memory mechanism and the user error handling/warning mechanisms in
* those cases where it does anything other than a memset.
*/
PNG_FUNCTION(
void,PNGAPI
png_info_init_3,(png_infopp ptr_ptr, size_t png_info_struct_size),
PNG_DEPRECATED)
{
png_inforp info_ptr = *ptr_ptr;
png_debug(
1,
"in png_info_init_3");
if (info_ptr == NULL)
return;
if ((
sizeof (png_info)) > png_info_struct_size)
{
*ptr_ptr = NULL;
/* The following line is why this API should not be used: */
free(info_ptr);
info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
(
sizeof *info_ptr)));
if (info_ptr == NULL)
return;
*ptr_ptr = info_ptr;
}
/* Set everything to 0 */
memset(info_ptr,
0, (
sizeof *info_ptr));
}
void PNGAPI
png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr,
int freer, png_uint_32 mask)
{
png_debug(
1,
"in png_data_freer");
if (png_ptr == NULL || info_ptr == NULL)
return;
if (freer == PNG_DESTROY_WILL_FREE_DATA)
info_ptr->free_me |= mask;
else if (freer == PNG_USER_WILL_FREE_DATA)
info_ptr->free_me &= ~mask;
else
png_error(png_ptr,
"Unknown freer parameter in png_data_freer");
}
void PNGAPI
png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask,
int num)
{
png_debug(
1,
"in png_free_data");
if (png_ptr == NULL || info_ptr == NULL)
return;
#ifdef PNG_TEXT_SUPPORTED
/* Free text item num or (if num == -1) all text items */
if (info_ptr->text != NULL &&
((mask & PNG_FREE_TEXT) & info_ptr->free_me) !=
0)
{
if (num != -
1)
{
png_free(png_ptr, info_ptr->text[num].key);
info_ptr->text[num].key = NULL;
}
else
{
int i;
for (i =
0; i < info_ptr->num_text; i++)
png_free(png_ptr, info_ptr->text[i].key);
png_free(png_ptr, info_ptr->text);
info_ptr->text = NULL;
info_ptr->num_text =
0;
info_ptr->max_text =
0;
}
}
#endif
#ifdef PNG_tRNS_SUPPORTED
/* Free any tRNS entry */
if (((mask & PNG_FREE_TRNS) & info_ptr->free_me) !=
0)
{
info_ptr->valid &= ~PNG_INFO_tRNS;
png_free(png_ptr, info_ptr->trans_alpha);
info_ptr->trans_alpha = NULL;
info_ptr->num_trans =
0;
}
#endif
#ifdef PNG_sCAL_SUPPORTED
/* Free any sCAL entry */
if (((mask & PNG_FREE_SCAL) & info_ptr->free_me) !=
0)
{
png_free(png_ptr, info_ptr->scal_s_width);
png_free(png_ptr, info_ptr->scal_s_height);
info_ptr->scal_s_width = NULL;
info_ptr->scal_s_height = NULL;
info_ptr->valid &= ~PNG_INFO_sCAL;
}
#endif
#ifdef PNG_pCAL_SUPPORTED
/* Free any pCAL entry */
if (((mask & PNG_FREE_PCAL) & info_ptr->free_me) !=
0)
{
png_free(png_ptr, info_ptr->pcal_purpose);
png_free(png_ptr, info_ptr->pcal_units);
info_ptr->pcal_purpose = NULL;
info_ptr->pcal_units = NULL;
if (info_ptr->pcal_params != NULL)
{
int i;
for (i =
0; i < info_ptr->pcal_nparams; i++)
png_free(png_ptr, info_ptr->pcal_params[i]);
png_free(png_ptr, info_ptr->pcal_params);
info_ptr->pcal_params = NULL;
}
info_ptr->valid &= ~PNG_INFO_pCAL;
}
#endif
#ifdef PNG_iCCP_SUPPORTED
/* Free any profile entry */
if (((mask & PNG_FREE_ICCP) & info_ptr->free_me) !=
0)
{
png_free(png_ptr, info_ptr->iccp_name);
png_free(png_ptr, info_ptr->iccp_profile);
info_ptr->iccp_name = NULL;
info_ptr->iccp_profile = NULL;
info_ptr->valid &= ~PNG_INFO_iCCP;
}
#endif
#ifdef PNG_sPLT_SUPPORTED
/* Free a given sPLT entry, or (if num == -1) all sPLT entries */
if (info_ptr->splt_palettes != NULL &&
((mask & PNG_FREE_SPLT) & info_ptr->free_me) !=
0)
{
if (num != -
1)
{
png_free(png_ptr, info_ptr->splt_palettes[num].name);
png_free(png_ptr, info_ptr->splt_palettes[num].entries);
info_ptr->splt_palettes[num].name = NULL;
info_ptr->splt_palettes[num].entries = NULL;
}
else
{
int i;
for (i =
0; i < info_ptr->splt_palettes_num; i++)
{
png_free(png_ptr, info_ptr->splt_palettes[i].name);
png_free(png_ptr, info_ptr->splt_palettes[i].entries);
}
png_free(png_ptr, info_ptr->splt_palettes);
info_ptr->splt_palettes = NULL;
info_ptr->splt_palettes_num =
0;
info_ptr->valid &= ~PNG_INFO_sPLT;
}
}
#endif
#ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
if (info_ptr->unknown_chunks != NULL &&
((mask & PNG_FREE_UNKN) & info_ptr->free_me) !=
0)
{
if (num != -
1)
{
png_free(png_ptr, info_ptr->unknown_chunks[num].data);
info_ptr->unknown_chunks[num].data = NULL;
}
else
{
int i;
for (i =
0; i < info_ptr->unknown_chunks_num; i++)
png_free(png_ptr, info_ptr->unknown_chunks[i].data);
png_free(png_ptr, info_ptr->unknown_chunks);
info_ptr->unknown_chunks = NULL;
info_ptr->unknown_chunks_num =
0;
}
}
#endif
#ifdef PNG_eXIf_SUPPORTED
/* Free any eXIf entry */
if (((mask & PNG_FREE_EXIF) & info_ptr->free_me) !=
0)
{
if (info_ptr->exif)
{
png_free(png_ptr, info_ptr->exif);
info_ptr->exif = NULL;
}
info_ptr->valid &= ~PNG_INFO_eXIf;
}
#endif
#ifdef PNG_hIST_SUPPORTED
/* Free any hIST entry */
if (((mask & PNG_FREE_HIST) & info_ptr->free_me) !=
0)
{
png_free(png_ptr, info_ptr->hist);
info_ptr->hist = NULL;
info_ptr->valid &= ~PNG_INFO_hIST;
}
#endif
/* Free any PLTE entry that was internally allocated */
if (((mask & PNG_FREE_PLTE) & info_ptr->free_me) !=
0)
{
png_free(png_ptr, info_ptr->palette);
info_ptr->palette = NULL;
info_ptr->valid &= ~PNG_INFO_PLTE;
info_ptr->num_palette =
0;
}
#ifdef PNG_INFO_IMAGE_SUPPORTED
/* Free any image bits attached to the info structure */
if (((mask & PNG_FREE_ROWS) & info_ptr->free_me) !=
0)
{
if (info_ptr->row_pointers != NULL)
{
png_uint_32 row;
for (row =
0; row < info_ptr->height; row++)
png_free(png_ptr, info_ptr->row_pointers[row]);
png_free(png_ptr, info_ptr->row_pointers);
info_ptr->row_pointers = NULL;
}
info_ptr->valid &= ~PNG_INFO_IDAT;
}
#endif
if (num != -
1)
mask &= ~PNG_FREE_MUL;
info_ptr->free_me &= ~mask;
}
#endif /* READ || WRITE */
/* This function returns a pointer to the io_ptr associated with the user
* functions. The application should free any memory associated with this
* pointer before png_write_destroy() or png_read_destroy() are called.
*/
png_voidp PNGAPI
png_get_io_ptr(png_const_structrp png_ptr)
{
if (png_ptr == NULL)
return NULL;
return png_ptr->io_ptr;
}
#if defined(PNG_READ_SUPPORTED) ||
defined(PNG_WRITE_SUPPORTED)
# ifdef PNG_STDIO_SUPPORTED
/* Initialize the default input/output functions for the PNG file. If you
* use your own read or write routines, you can call either png_set_read_fn()
* or png_set_write_fn() instead of png_init_io(). If you have defined
* PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
* function of your own because "FILE *" isn't necessarily available.
*/
void PNGAPI
png_init_io(png_structrp png_ptr, FILE *fp)
{
png_debug(
1,
"in png_init_io");
if (png_ptr == NULL)
return;
png_ptr->io_ptr = (png_voidp)fp;
}
# endif
# ifdef PNG_SAVE_INT_32_SUPPORTED
/* PNG signed integers are saved in 32-bit 2's complement format. ANSI C-90
* defines a cast of a signed integer to an unsigned integer either to preserve
* the value, if it is positive, or to calculate:
*
* (UNSIGNED_MAX+1) + integer
*
* Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
* negative integral value is added the result will be an unsigned value
* corresponding to the 2's complement representation.
*/
void PNGAPI
png_save_int_32(png_bytep buf, png_int_32 i)
{
png_save_uint_32(buf, (png_uint_32)i);
}
# endif
# ifdef PNG_TIME_RFC1123_SUPPORTED
/* Convert the supplied time into an RFC 1123 string suitable for use in
* a "Creation Time" or other text-based time string.
*/
int PNGAPI
png_convert_to_rfc1123_buffer(
char out[
29], png_const_timep ptime)
{
static const char short_months[
12][
4] =
{
"Jan",
"Feb",
"Mar",
"Apr",
"May",
"Jun",
"Jul",
"Aug",
"Sep",
"Oct",
"Nov",
"Dec"};
if (out == NULL)
return 0;
if (ptime->year >
9999 /* RFC1123 limitation */ ||
ptime->month ==
0 || ptime->month >
12 ||
ptime->day ==
0 || ptime->day >
31 ||
ptime->hour >
23 || ptime->minute >
59 ||
ptime->second >
60)
return 0;
{
size_t pos =
0;
char number_buf[
5] = {
0,
0,
0,
0,
0};
/* enough for a four-digit year */
# define APPEND_STRING(string) pos = png_safecat(out,
29, pos, (string))
# define APPEND_NUMBER(format, value)\
APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
# define APPEND(ch)
if (pos <
28) out[pos++] = (ch)
APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (
unsigned)ptime->day);
APPEND(
' ');
APPEND_STRING(short_months[(ptime->month -
1)]);
APPEND(
' ');
APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);
APPEND(
' ');
APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (
unsigned)ptime->hour);
APPEND(
':');
APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (
unsigned)ptime->minute);
APPEND(
':');
APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (
unsigned)ptime->second);
APPEND_STRING(
" +0000");
/* This reliably terminates the buffer */
PNG_UNUSED (pos)
# undef APPEND
# undef APPEND_NUMBER
# undef APPEND_STRING
}
return 1;
}
# if PNG_LIBPNG_VER <
10700
/* To do: remove the following from libpng-1.7 */
/* Original API that uses a private buffer in png_struct.
* Deprecated because it causes png_struct to carry a spurious temporary
* buffer (png_struct::time_buffer), better to have the caller pass this in.
*/
png_const_charp PNGAPI
png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)
{
if (png_ptr != NULL)
{
/* The only failure above if png_ptr != NULL is from an invalid ptime */
if (png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime) ==
0)
png_warning(png_ptr,
"Ignoring invalid time value");
else
return png_ptr->time_buffer;
}
return NULL;
}
# endif
/* LIBPNG_VER < 10700 */
# endif
/* TIME_RFC1123 */
#endif /* READ || WRITE */
png_const_charp PNGAPI
png_get_copyright(png_const_structrp png_ptr)
{
PNG_UNUSED(png_ptr)
/* Silence compiler warning about unused png_ptr */
#ifdef PNG_STRING_COPYRIGHT
return PNG_STRING_COPYRIGHT
#else
return PNG_STRING_NEWLINE \
"libpng version 1.6.58" PNG_STRING_NEWLINE \
"Copyright (c) 2018-2026 Cosmin Truta" PNG_STRING_NEWLINE \
"Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson" \
PNG_STRING_NEWLINE \
"Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
"Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
PNG_STRING_NEWLINE;
#endif
}
/* The following return the library version as a short string in the
* format 1.0.0 through 99.99.99zz. To get the version of *.h files
* used with your application, print out PNG_LIBPNG_VER_STRING, which
* is defined in png.h.
* Note: now there is no difference between png_get_libpng_ver() and
* png_get_header_ver(). Due to the version_nn_nn_nn typedef guard,
* it is guaranteed that png.c uses the correct version of png.h.
*/
png_const_charp PNGAPI
png_get_libpng_ver(png_const_structrp png_ptr)
{
/* Version of *.c files used when building libpng */
return png_get_header_ver(png_ptr);
}
png_const_charp PNGAPI
png_get_header_ver(png_const_structrp png_ptr)
{
/* Version of *.h files used when building libpng */
PNG_UNUSED(png_ptr)
/* Silence compiler warning about unused png_ptr */
return PNG_LIBPNG_VER_STRING;
}
png_const_charp PNGAPI
png_get_header_version(png_const_structrp png_ptr)
{
/* Returns longer string containing both version and date */
PNG_UNUSED(png_ptr)
/* Silence compiler warning about unused png_ptr */
#ifdef __STDC__
return PNG_HEADER_VERSION_STRING
# ifndef PNG_READ_SUPPORTED
" (NO READ SUPPORT)"
# endif
PNG_STRING_NEWLINE;
#else
return PNG_HEADER_VERSION_STRING;
#endif
}
#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
/* NOTE: this routine is not used internally! */
/* Build a grayscale palette. Palette is assumed to be 1 << bit_depth
* large of png_color. This lets grayscale images be treated as
* paletted. Most useful for gamma correction and simplification
* of code. This API is not used internally.
*/
void PNGAPI
png_build_grayscale_palette(
int bit_depth, png_colorp palette)
{
int num_palette;
int color_inc;
int i;
int v;
png_debug(
1,
"in png_do_build_grayscale_palette");
if (palette == NULL)
return;
switch (bit_depth)
{
case 1:
num_palette =
2;
color_inc =
0xff;
break;
case 2:
num_palette =
4;
color_inc =
0x55;
break;
case 4:
num_palette =
16;
color_inc =
0x11;
break;
case 8:
num_palette =
256;
color_inc =
1;
break;
default:
num_palette =
0;
color_inc =
0;
break;
}
for (i =
0, v =
0; i < num_palette; i++, v += color_inc)
{
palette[i].red = (png_byte)(v &
0xff);
palette[i].green = (png_byte)(v &
0xff);
palette[i].blue = (png_byte)(v &
0xff);
}
}
#endif
#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
int PNGAPI
png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)
{
/* Check chunk_name and return "keep" value if it's on the list, else 0 */
png_const_bytep p, p_end;
if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list ==
0)
return PNG_HANDLE_CHUNK_AS_DEFAULT;
p_end = png_ptr->chunk_list;
p = p_end + png_ptr->num_chunk_list*
5;
/* beyond end */
/* The code is the fifth byte after each four byte string. Historically this
* code was always searched from the end of the list, this is no longer
* necessary because the 'set' routine handles duplicate entries correctly.
*/
do /* num_chunk_list > 0, so at least one */
{
p -=
5;
if (memcmp(chunk_name, p,
4) ==
0)
return p[
4];
}
while (p > p_end);
/* This means that known chunks should be processed and unknown chunks should
* be handled according to the value of png_ptr->unknown_default; this can be
* confusing because, as a result, there are two levels of defaulting for
* unknown chunks.
*/
return PNG_HANDLE_CHUNK_AS_DEFAULT;
}
#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
int /* PRIVATE */
png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)
{
png_byte chunk_string[
5];
PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);
return png_handle_as_unknown(png_ptr, chunk_string);
}
#endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */
#endif /* SET_UNKNOWN_CHUNKS */
#ifdef PNG_READ_SUPPORTED
/* This function, added to libpng-1.0.6g, is untested. */
int PNGAPI
png_reset_zstream(png_structrp png_ptr)
{
if (png_ptr == NULL)
return Z_STREAM_ERROR;
/* WARNING: this resets the window bits to the maximum! */
return inflateReset(&png_ptr->zstream);
}
#endif /* READ */
/* This function was added to libpng-1.0.7 */
png_uint_32 PNGAPI
png_access_version_number(
void)
{
/* Version of *.c files used when building libpng */
return (png_uint_32)PNG_LIBPNG_VER;
}
#if defined(PNG_READ_SUPPORTED) ||
defined(PNG_WRITE_SUPPORTED)
/* Ensure that png_ptr->zstream.msg holds some appropriate error message string.
* If it doesn't 'ret' is used to set it to something appropriate, even in cases
* like Z_OK or Z_STREAM_END where the error code is apparently a success code.
*/
void /* PRIVATE */
png_zstream_error(png_structrp png_ptr,
int ret)
{
/* Translate 'ret' into an appropriate error string, priority is given to the
* one in zstream if set. This always returns a string, even in cases like
* Z_OK or Z_STREAM_END where the error code is a success code.
*/
if (png_ptr->zstream.msg == NULL)
switch (ret)
{
default:
case Z_OK:
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"unexpected zlib return code");
break;
case Z_STREAM_END:
/* Normal exit */
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"unexpected end of LZ stream");
break;
case Z_NEED_DICT:
/* This means the deflate stream did not have a dictionary; this
* indicates a bogus PNG.
*/
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"missing LZ dictionary");
break;
case Z_ERRNO:
/* gz APIs only: should not happen */
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"zlib IO error");
break;
case Z_STREAM_ERROR:
/* internal libpng error */
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"bad parameters to zlib");
break;
case Z_DATA_ERROR:
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"damaged LZ stream");
break;
case Z_MEM_ERROR:
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"insufficient memory");
break;
case Z_BUF_ERROR:
/* End of input or output; not a problem if the caller is doing
* incremental read or write.
*/
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"truncated");
break;
case Z_VERSION_ERROR:
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"unsupported zlib version");
break;
case PNG_UNEXPECTED_ZLIB_RETURN:
/* Compile errors here mean that zlib now uses the value co-opted in
* pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above
* and change pngpriv.h. Note that this message is "... return",
* whereas the default/Z_OK one is "... return code".
*/
png_ptr->zstream.msg = PNGZ_MSG_CAST(
"unexpected zlib return");
break;
}
}
#ifdef PNG_COLORSPACE_SUPPORTED
static png_int_32
png_fp_add(png_int_32 addend0, png_int_32 addend1,
int *error)
{
/* Safely add two fixed point values setting an error flag and returning 0.5
* on overflow.
* IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
* relying on addition of two positive values producing a negative one is not
* safe.
*/
if (addend0 >
0)
{
if (
0x7fffffff - addend0 >= addend1)
return addend0+addend1;
}
else if (addend0 <
0)
{
if (-
0x7fffffff - addend0 <= addend1)
return addend0+addend1;
}
else
return addend1;
*error =
1;
return PNG_FP_1/
2;
}
static png_int_32
png_fp_sub(png_int_32 addend0, png_int_32 addend1,
int *error)
{
/* As above but calculate addend0-addend1. */
if (addend1 >
0)
{
if (-
0x7fffffff + addend1 <= addend0)
return addend0-addend1;
}
else if (addend1 <
0)
{
if (
0x7fffffff + addend1 >= addend0)
return addend0-addend1;
}
else
return addend0;
*error =
1;
return PNG_FP_1/
2;
}
static int
png_safe_add(png_int_32 *addend0_and_result, png_int_32 addend1,
png_int_32 addend2)
{
/* Safely add three integers. Returns 0 on success, 1 on overflow. Does not
* set the result on overflow.
*/
int error =
0;
int result = png_fp_add(*addend0_and_result,
png_fp_add(addend1, addend2, &error),
&error);
if (!error) *addend0_and_result = result;
return error;
}
/* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for
* cHRM, as opposed to using chromaticities. These internal APIs return
* non-zero on a parameter error. The X, Y and Z values are required to be
* positive and less than 1.0.
*/
int /* PRIVATE */
png_xy_from_XYZ(png_xy *xy,
const png_XYZ *XYZ)
{
/* NOTE: returns 0 on success, 1 means error. */
png_int_32 d, dred, dgreen, dblue, dwhite, whiteX, whiteY;
/* 'd' in each of the blocks below is just X+Y+Z for each component,
* x, y and z are X,Y,Z/(X+Y+Z).
*/
d = XYZ->red_X;
if (png_safe_add(&d, XYZ->red_Y, XYZ->red_Z))
return 1;
dred = d;
if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, dred) ==
0)
return 1;
if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, dred) ==
0)
return 1;
d = XYZ->green_X;
if (png_safe_add(&d, XYZ->green_Y, XYZ->green_Z))
return 1;
dgreen = d;
if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, dgreen) ==
0)
return 1;
if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, dgreen) ==
0)
return 1;
d = XYZ->blue_X;
if (png_safe_add(&d, XYZ->blue_Y, XYZ->blue_Z))
return 1;
dblue = d;
if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, dblue) ==
0)
return 1;
if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, dblue) ==
0)
return 1;
/* The reference white is simply the sum of the end-point (X,Y,Z) vectors so
* the following calculates (X+Y+Z) of the reference white (media white,
* encoding white) itself:
*/
d = dblue;
if (png_safe_add(&d, dred, dgreen))
return 1;
dwhite = d;
/* Find the white X,Y values from the sum of the red, green and blue X,Y
* values.
*/
d = XYZ->red_X;
if (png_safe_add(&d, XYZ->green_X, XYZ->blue_X))
return 1;
whiteX = d;
d = XYZ->red_Y;
if (png_safe_add(&d, XYZ->green_Y, XYZ->blue_Y))
return 1;
whiteY = d;
if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) ==
0)
return 1;
if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) ==
0)
return 1;
return 0;
}
int /* PRIVATE */
png_XYZ_from_xy(png_XYZ *XYZ,
const png_xy *xy)
{
/* NOTE: returns 0 on success, 1 means error. */
png_fixed_point red_inverse, green_inverse, blue_scale;
png_fixed_point left, right, denominator;
/* Check xy and, implicitly, z. Note that wide gamut color spaces typically
* have end points with 0 tristimulus values (these are impossible end
* points, but they are used to cover the possible colors). We check
* xy->whitey against 5, not 0, to avoid a possible integer overflow.
*
* The limits here will *not* accept ACES AP0, where bluey is -7700
* (-0.0770) because the PNG spec itself requires the xy values to be
* unsigned. whitey is also required to be 5 or more to avoid overflow.
*
* Instead the upper limits have been relaxed to accommodate ACES AP1 where
* redz ends up as -600 (-0.006). ProPhotoRGB was already "in range."
* The new limit accommodates the AP0 and AP1 ranges for z but not AP0 redy.
*/
const png_fixed_point fpLimit = PNG_FP_1+(PNG_FP_1/
10);
if (xy->redx <
0 || xy->redx > fpLimit)
return 1;
if (xy->redy <
0 || xy->redy > fpLimit-xy->redx)
return 1;
if (xy->greenx <
0 || xy->greenx > fpLimit)
return 1;
if (xy->greeny <
0 || xy->greeny > fpLimit-xy->greenx)
return 1;
if (xy->bluex <
0 || xy->bluex > fpLimit)
return 1;
if (xy->bluey <
0 || xy->bluey > fpLimit-xy->bluex)
return 1;
if (xy->whitex <
0 || xy->whitex > fpLimit)
return 1;
if (xy->whitey <
5 || xy->whitey > fpLimit-xy->whitex)
return 1;
/* The reverse calculation is more difficult because the original tristimulus
* value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8
* derived values were recorded in the cHRM chunk;
* (red,green,blue,white)x(x,y). This loses one degree of freedom and
* therefore an arbitrary ninth value has to be introduced to undo the
* original transformations.
*
* Think of the original end-points as points in (X,Y,Z) space. The
* chromaticity values (c) have the property:
*
* C
* c = ---------
* X + Y + Z
*
* For each c (x,y,z) from the corresponding original C (X,Y,Z). Thus the
* three chromaticity values (x,y,z) for each end-point obey the
* relationship:
*
* x + y + z = 1
*
* This describes the plane in (X,Y,Z) space that intersects each axis at the
* value 1.0; call this the chromaticity plane. Thus the chromaticity
* calculation has scaled each end-point so that it is on the x+y+z=1 plane
* and chromaticity is the intersection of the vector from the origin to the
* (X,Y,Z) value with the chromaticity plane.
*
* To fully invert the chromaticity calculation we would need the three
* end-point scale factors, (red-scale, green-scale, blue-scale), but these
* were not recorded. Instead we calculated the reference white (X,Y,Z) and
* recorded the chromaticity of this. The reference white (X,Y,Z) would have
* given all three of the scale factors since:
*
* color-C = color-c * color-scale
* white-C = red-C + green-C + blue-C
* = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
*
* But cHRM records only white-x and white-y, so we have lost the white scale
* factor:
*
* white-C = white-c*white-scale
*
* To handle this the inverse transformation makes an arbitrary assumption
* about white-scale:
*
* Assume: white-Y = 1.0
* Hence: white-scale = 1/white-y
* Or: red-Y + green-Y + blue-Y = 1.0
*
* Notice the last statement of the assumption gives an equation in three of
* the nine values we want to calculate. 8 more equations come from the
* above routine as summarised at the top above (the chromaticity
* calculation):
*
* Given: color-x = color-X / (color-X + color-Y + color-Z)
* Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0
*
* This is 9 simultaneous equations in the 9 variables "color-C" and can be
* solved by Cramer's rule. Cramer's rule requires calculating 10 9x9 matrix
* determinants, however this is not as bad as it seems because only 28 of
* the total of 90 terms in the various matrices are non-zero. Nevertheless
* Cramer's rule is notoriously numerically unstable because the determinant
* calculation involves the difference of large, but similar, numbers. It is
* difficult to be sure that the calculation is stable for real world values
* and it is certain that it becomes unstable where the end points are close
* together.
*
* So this code uses the perhaps slightly less optimal but more
* understandable and totally obvious approach of calculating color-scale.
*
* This algorithm depends on the precision in white-scale and that is
* (1/white-y), so we can immediately see that as white-y approaches 0 the
* accuracy inherent in the cHRM chunk drops off substantially.
*
* libpng arithmetic: a simple inversion of the above equations
* ------------------------------------------------------------
*
* white_scale = 1/white-y
* white-X = white-x * white-scale
* white-Y = 1.0
* white-Z = (1 - white-x - white-y) * white_scale
*
* white-C = red-C + green-C + blue-C
* = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
*
* This gives us three equations in (red-scale,green-scale,blue-scale) where
* all the coefficients are now known:
*
* red-x*red-scale + green-x*green-scale + blue-x*blue-scale
* = white-x/white-y
* red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
* red-z*red-scale + green-z*green-scale + blue-z*blue-scale
* = (1 - white-x - white-y)/white-y
*
* In the last equation color-z is (1 - color-x - color-y) so we can add all
* three equations together to get an alternative third:
*
* red-scale + green-scale + blue-scale = 1/white-y = white-scale
*
* So now we have a Cramer's rule solution where the determinants are just
* 3x3 - far more tractable. Unfortunately 3x3 determinants still involve
* multiplication of three coefficients so we can't guarantee to avoid
* overflow in the libpng fixed point representation. Using Cramer's rule in
* floating point is probably a good choice here, but it's not an option for
* fixed point. Instead proceed to simplify the first two equations by
* eliminating what is likely to be the largest value, blue-scale:
*
* blue-scale = white-scale - red-scale - green-scale
*
* Hence:
*
* (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale =
* (white-x - blue-x)*white-scale
*
* (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale =
* 1 - blue-y*white-scale
*
* And now we can trivially solve for (red-scale,green-scale):
*
* green-scale =
* (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale
* -----------------------------------------------------------
* green-x - blue-x
*
* red-scale =
* 1 - blue-y*white-scale - (green-y - blue-y) * green-scale
* ---------------------------------------------------------
* red-y - blue-y
*
* Hence:
*
* red-scale =
* ( (green-x - blue-x) * (white-y - blue-y) -
* (green-y - blue-y) * (white-x - blue-x) ) / white-y
* -------------------------------------------------------------------------
* (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
*
* green-scale =
* ( (red-y - blue-y) * (white-x - blue-x) -
* (red-x - blue-x) * (white-y - blue-y) ) / white-y
* -------------------------------------------------------------------------
* (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x)
*
* Accuracy:
* The input values have 5 decimal digits of accuracy.
*
* In the previous implementation the values were all in the range 0 < value
* < 1, so simple products are in the same range but may need up to 10
* decimal digits to preserve the original precision and avoid underflow.
* Because we are using a 32-bit signed representation we cannot match this;
* the best is a little over 9 decimal digits, less than 10.
*
* This range has now been extended to allow values up to 1.1, or 110,000 in
* fixed point.
*
* The approach used here is to preserve the maximum precision within the
* signed representation. Because the red-scale calculation above uses the
* difference between two products of values that must be in the range
* -1.1..+1.1 it is sufficient to divide the product by 8;
* ceil(121,000/32767*2). The factor is irrelevant in the calculation
* because it is applied to both numerator and denominator.
*
* Note that the values of the differences of the products of the
* chromaticities in the above equations tend to be small, for example for
* the sRGB chromaticities they are:
*
* red numerator: -0.04751
* green numerator: -0.08788
* denominator: -0.2241 (without white-y multiplication)
*
* The resultant Y coefficients from the chromaticities of some widely used
* color space definitions are (to 15 decimal places):
*
* sRGB
* 0.212639005871510 0.715168678767756 0.072192315360734
* Kodak ProPhoto
* 0.288071128229293 0.711843217810102 0.000085653960605
* Adobe RGB
* 0.297344975250536 0.627363566255466 0.075291458493998
* Adobe Wide Gamut RGB
* 0.258728243040113 0.724682314948566 0.016589442011321
*/
{
int error =
0;
/* By the argument above overflow should be impossible here, however the
* code now simply returns a failure code. The xy subtracts in the
* arguments to png_muldiv are *not* checked for overflow because the
* checks at the start guarantee they are in the range 0..110000 and
* png_fixed_point is a 32-bit signed number.
*/
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey,
8) ==
0)
return 1;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex,
8) ==
0)
return 1;
denominator = png_fp_sub(left, right, &error);
if (error)
return 1;
/* Now find the red numerator. */
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey,
8) ==
0)
return 1;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex,
8) ==
0)
return 1;
/* Overflow is possible here and it indicates an extreme set of PNG cHRM
* chunk values. This calculation actually returns the reciprocal of the
* scale value because this allows us to delay the multiplication of
* white-y into the denominator, which tends to produce a small number.
*/
if (png_muldiv(&red_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) ==
0 || error ||
red_inverse <= xy->whitey
/* r+g+b scales = white scale */)
return 1;
/* Similarly for green_inverse: */
if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex,
8) ==
0)
return 1;
if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey,
8) ==
0)
return 1;
if (png_muldiv(&green_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) ==
0 || error ||
green_inverse <= xy->whitey)
return 1;
/* And the blue scale, the checks above guarantee this can't overflow but
* it can still produce 0 for extreme cHRM values.
*/
blue_scale = png_fp_sub(png_fp_sub(png_reciprocal(xy->whitey),
png_reciprocal(red_inverse), &error),
png_reciprocal(green_inverse), &error);
if (error || blue_scale <=
0)
return 1;
}
/* And fill in the png_XYZ. Again the subtracts are safe because of the
* checks on the xy values at the start (the subtracts just calculate the
* corresponding z values.)
*/
if (png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse) ==
0)
return 1;
if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) ==
0)
return 1;
if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
red_inverse) ==
0)
return 1;
if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) ==
0)
return 1;
if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) ==
0)
return 1;
if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
green_inverse) ==
0)
return 1;
if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) ==
0)
return 1;
if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) ==
0)
return 1;
if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
PNG_FP_1) ==
0)
return 1;
return 0;
/*success*/
}
#endif /* COLORSPACE */
#ifdef PNG_READ_iCCP_SUPPORTED
/* Error message generation */
static char
png_icc_tag_char(png_uint_32 byte)
{
byte &=
0xff;
if (byte >=
32 && byte <=
126)
return (
char)byte;
else
return '?';
}
static void
png_icc_tag_name(
char *name, png_uint_32 tag)
{
name[
0] =
'\'';
name[
1] = png_icc_tag_char(tag >>
24);
name[
2] = png_icc_tag_char(tag >>
16);
name[
3] = png_icc_tag_char(tag >>
8);
name[
4] = png_icc_tag_char(tag );
name[
5] =
'\'';
}
static int
is_ICC_signature_char(png_alloc_size_t it)
{
return it ==
32 || (it >=
48 && it <=
57) || (it >=
65 && it <=
90) ||
(it >=
97 && it <=
122);
}
static int
is_ICC_signature(png_alloc_size_t it)
{
return is_ICC_signature_char(it >>
24)
/* checks all the top bits */ &&
is_ICC_signature_char((it >>
16) &
0xff) &&
is_ICC_signature_char((it >>
8) &
0xff) &&
is_ICC_signature_char(it &
0xff);
}
static int
png_icc_profile_error(png_const_structrp png_ptr, png_const_charp name,
png_alloc_size_t value, png_const_charp reason)
{
size_t pos;
char message[
196];
/* see below for calculation */
pos = png_safecat(message, (
sizeof message),
0,
"profile '");
/* 9 chars */
pos = png_safecat(message, pos+
79, pos, name);
/* Truncate to 79 chars */
pos = png_safecat(message, (
sizeof message), pos,
"': ");
/* +2 = 90 */
if (is_ICC_signature(value) !=
0)
{
/* So 'value' is at most 4 bytes and the following cast is safe */
png_icc_tag_name(message+pos, (png_uint_32)value);
pos +=
6;
/* total +8; less than the else clause */
message[pos++] =
':';
message[pos++] =
' ';
}
# ifdef PNG_WARNINGS_SUPPORTED
else
{
char number[PNG_NUMBER_BUFFER_SIZE];
/* +24 = 114 */
pos = png_safecat(message, (
sizeof message), pos,
png_format_number(number, number+(
sizeof number),
PNG_NUMBER_FORMAT_x, value));
pos = png_safecat(message, (
sizeof message), pos,
"h: ");
/* +2 = 116 */
}
# endif
/* The 'reason' is an arbitrary message, allow +79 maximum 195 */
pos = png_safecat(message, (
sizeof message), pos, reason);
PNG_UNUSED(pos)
png_chunk_benign_error(png_ptr, message);
return 0;
}
/* Encoded value of D50 as an ICC XYZNumber. From the ICC 2010 spec the value
* is XYZ(0.9642,1.0,0.8249), which scales to:
*
* (63189.8112, 65536, 54060.6464)
*/
static const png_byte D50_nCIEXYZ[
12] =
{
0x00,
0x00,
0xf6,
0xd6,
0x00,
0x01,
0x00,
0x00,
0x00,
0x00,
0xd3,
0x2d };
static int /* bool */
icc_check_length(png_const_structrp png_ptr, png_const_charp name,
png_uint_32 profile_length)
{
if (profile_length <
132)
return png_icc_profile_error(png_ptr, name, profile_length,
"too short");
return 1;
}
int /* PRIVATE */
png_icc_check_length(png_const_structrp png_ptr, png_const_charp name,
png_uint_32 profile_length)
{
if (!icc_check_length(png_ptr, name, profile_length))
return 0;
/* This needs to be here because the 'normal' check is in
* png_decompress_chunk, yet this happens after the attempt to
* png_malloc_base the required data. We only need this on read; on write
* the caller supplies the profile buffer so libpng doesn't allocate it. See
* the call to icc_check_length below (the write case).
*/
if (profile_length > png_chunk_max(png_ptr))
return png_icc_profile_error(png_ptr, name, profile_length,
"profile too long");
return 1;
}
int /* PRIVATE */
png_icc_check_header(png_const_structrp png_ptr, png_const_charp name,
png_uint_32 profile_length,
png_const_bytep profile
/* first 132 bytes only */, int color_type)
{
png_uint_32 temp;
/* Length check; this cannot be ignored in this code because profile_length
* is used later to check the tag table, so even if the profile seems over
* long profile_length from the caller must be correct. The caller can fix
* this up on read or write by just passing in the profile header length.
*/
temp = png_get_uint_32(profile);
if (temp != profile_length)
return png_icc_profile_error(png_ptr, name, temp,
"length does not match profile");
temp = (png_uint_32) (*(profile+
8));
if (temp >
3 && (profile_length &
3))
return png_icc_profile_error(png_ptr, name, profile_length,
"invalid length");
temp = png_get_uint_32(profile+
128);
/* tag count: 12 bytes/tag */
if (temp >
357913930 ||
/* (2^32-4-132)/12: maximum possible tag count */
profile_length <
132+
12*temp)
/* truncated tag table */
return png_icc_profile_error(png_ptr, name, temp,
"tag count too large");
/* The 'intent' must be valid or we can't store it, ICC limits the intent to
* 16 bits.
*/
temp = png_get_uint_32(profile+
64);
if (temp >=
0xffff)
/* The ICC limit */
return png_icc_profile_error(png_ptr, name, temp,
"invalid rendering intent");
/* This is just a warning because the profile may be valid in future
* versions.
*/
if (temp >= PNG_sRGB_INTENT_LAST)
(
void)png_icc_profile_error(png_ptr, name, temp,
"intent outside defined range");
/* At this point the tag table can't be checked because it hasn't necessarily
* been loaded; however, various header fields can be checked. These checks
* are for values permitted by the PNG spec in an ICC profile; the PNG spec
* restricts the profiles that can be passed in an iCCP chunk (they must be
* appropriate to processing PNG data!)
*/
/* Data checks (could be skipped). These checks must be independent of the
* version number; however, the version number doesn't accommodate changes in
* the header fields (just the known tags and the interpretation of the
* data.)
*/
temp = png_get_uint_32(profile+
36);
/* signature 'ascp' */
if (temp !=
0x61637370)
return png_icc_profile_error(png_ptr, name, temp,
"invalid signature");
/* Currently the PCS illuminant/adopted white point (the computational
* white point) are required to be D50,
* however the profile contains a record of the illuminant so perhaps ICC
* expects to be able to change this in the future (despite the rationale in
* the introduction for using a fixed PCS adopted white.) Consequently the
* following is just a warning.
*/
if (memcmp(profile+
68, D50_nCIEXYZ,
12) !=
0)
(
void)png_icc_profile_error(png_ptr, name,
0/*no tag value*/,
"PCS illuminant is not D50");
/* The PNG spec requires this:
* "If the iCCP chunk is present, the image samples conform to the colour
* space represented by the embedded ICC profile as defined by the
* International Color Consortium [ICC]. The colour space of the ICC profile
* shall be an RGB colour space for colour images (PNG colour types 2, 3, and
* 6), or a greyscale colour space for greyscale images (PNG colour types 0
* and 4)."
*
* This checking code ensures the embedded profile (on either read or write)
* conforms to the specification requirements. Notice that an ICC 'gray'
* color-space profile contains the information to transform the monochrome
* data to XYZ or L*a*b (according to which PCS the profile uses) and this
* should be used in preference to the standard libpng K channel replication
* into R, G and B channels.
*
* Previously it was suggested that an RGB profile on grayscale data could be
* handled. However it is clear that using an RGB profile in this context
* must be an error - there is no specification of what it means. Thus it is
* almost certainly more correct to ignore the profile.
*/
temp = png_get_uint_32(profile+
16);
/* data colour space field */
switch (temp)
{
case 0x52474220:
/* 'RGB ' */
if ((color_type & PNG_COLOR_MASK_COLOR) ==
0)
return png_icc_profile_error(png_ptr, name, temp,
"RGB color space not permitted on grayscale PNG");
break;
case 0x47524159:
/* 'GRAY' */
if ((color_type & PNG_COLOR_MASK_COLOR) !=
0)
return png_icc_profile_error(png_ptr, name, temp,
"Gray color space not permitted on RGB PNG");
break;
default:
return png_icc_profile_error(png_ptr, name, temp,
"invalid ICC profile color space");
}
/* It is up to the application to check that the profile class matches the
* application requirements; the spec provides no guidance, but it's pretty
* weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer
* ('prtr') or 'spac' (for generic color spaces). Issue a warning in these
* cases. Issue an error for device link or abstract profiles - these don't
* contain the records necessary to transform the color-space to anything
* other than the target device (and not even that for an abstract profile).
* Profiles of these classes may not be embedded in images.
*/
temp = png_get_uint_32(profile+
12);
/* profile/device class */
switch (temp)
{
case 0x73636e72:
/* 'scnr' */
case 0x6d6e7472:
/* 'mntr' */
case 0x70727472:
/* 'prtr' */
case 0x73706163:
/* 'spac' */
/* All supported */
break;
case 0x61627374:
/* 'abst' */
/* May not be embedded in an image */
return png_icc_profile_error(png_ptr, name, temp,
"invalid embedded Abstract ICC profile");
case 0x6c696e6b:
/* 'link' */
/* DeviceLink profiles cannot be interpreted in a non-device specific
* fashion, if an app uses the AToB0Tag in the profile the results are
* undefined unless the result is sent to the intended device,
* therefore a DeviceLink profile should not be found embedded in a
* PNG.
*/
return png_icc_profile_error(png_ptr, name, temp,
"unexpected DeviceLink ICC profile class");
case 0x6e6d636c:
/* 'nmcl' */
/* A NamedColor profile is also device specific, however it doesn't
* contain an AToB0 tag that is open to misinterpretation. Almost
* certainly it will fail the tests below.
*/
(
void)png_icc_profile_error(png_ptr, name, temp,
"unexpected NamedColor ICC profile class");
break;
default:
/* To allow for future enhancements to the profile accept unrecognized
* profile classes with a warning, these then hit the test below on the
* tag content to ensure they are backward compatible with one of the
* understood profiles.
*/
(
void)png_icc_profile_error(png_ptr, name, temp,
"unrecognized ICC profile class");
break;
}
/* For any profile other than a device link one the PCS must be encoded
* either in XYZ or Lab.
*/
temp = png_get_uint_32(profile+
20);
switch (temp)
{
case 0x58595a20:
/* 'XYZ ' */
case 0x4c616220:
/* 'Lab ' */
break;
default:
return png_icc_profile_error(png_ptr, name, temp,
"unexpected ICC PCS encoding");
}
return 1;
}
int /* PRIVATE */
png_icc_check_tag_table(png_const_structrp png_ptr, png_const_charp name,
png_uint_32 profile_length,
png_const_bytep profile
/* header plus whole tag table */)
{
png_uint_32 tag_count = png_get_uint_32(profile+
128);
png_uint_32 itag;
png_const_bytep tag = profile+
132;
/* The first tag */
/* First scan all the tags in the table and add bits to the icc_info value
* (temporarily in 'tags').
*/
for (itag=
0; itag < tag_count; ++itag, tag +=
12)
{
png_uint_32 tag_id = png_get_uint_32(tag+
0);
png_uint_32 tag_start = png_get_uint_32(tag+
4);
/* must be aligned */
png_uint_32 tag_length = png_get_uint_32(tag+
8);
/* not padded */
/* The ICC specification does not exclude zero length tags, therefore the
* start might actually be anywhere if there is no data, but this would be
* a clear abuse of the intent of the standard so the start is checked for
* being in range. All defined tag types have an 8 byte header - a 4 byte
* type signature then 0.
*/
/* This is a hard error; potentially it can cause read outside the
* profile.
*/
if (tag_start > profile_length || tag_length > profile_length - tag_start)
return png_icc_profile_error(png_ptr, name, tag_id,
"ICC profile tag outside profile");
if ((tag_start &
3) !=
0)
{
/* CNHP730S.icc shipped with Microsoft Windows 64 violates this; it is
* only a warning here because libpng does not care about the
* alignment.
*/
(
void)png_icc_profile_error(png_ptr, name, tag_id,
"ICC profile tag start not a multiple of 4");
}
}
return 1;
/* success, maybe with warnings */
}
#endif /* READ_iCCP */
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
#if (
defined PNG_READ_mDCV_SUPPORTED) || (
defined PNG_READ_cHRM_SUPPORTED)
static int
have_chromaticities(png_const_structrp png_ptr)
{
/* Handle new PNGv3 chunks and the precedence rules to determine whether
* png_struct::chromaticities must be processed. Only required for RGB to
* gray.
*
* mDCV: this is the mastering colour space and it is independent of the
* encoding so it needs to be used regardless of the encoded space.
*
* cICP: first in priority but not yet implemented - the chromaticities come
* from the 'primaries'.
*
* iCCP: not supported by libpng (so ignored)
*
* sRGB: the defaults match sRGB
*
* cHRM: calculate the coefficients
*/
# ifdef PNG_READ_mDCV_SUPPORTED
if (png_has_chunk(png_ptr, mDCV))
return 1;
# define check_chromaticities
1
# endif
/*mDCV*/
# ifdef PNG_READ_sRGB_SUPPORTED
if (png_has_chunk(png_ptr, sRGB))
return 0;
# endif
/*sRGB*/
# ifdef PNG_READ_cHRM_SUPPORTED
if (png_has_chunk(png_ptr, cHRM))
return 1;
# define check_chromaticities
1
# endif
/*cHRM*/
return 0;
/* sRGB defaults */
}
#endif /* READ_mDCV || READ_cHRM */
void /* PRIVATE */
png_set_rgb_coefficients(png_structrp png_ptr)
{
/* Set the rgb_to_gray coefficients from the colorspace if available. Note
* that '_set' means that png_rgb_to_gray was called **and** it successfully
* set up the coefficients.
*/
if (png_ptr->rgb_to_gray_coefficients_set ==
0)
{
# if check_chromaticities
png_XYZ xyz;
if (have_chromaticities(png_ptr) &&
png_XYZ_from_xy(&xyz, &png_ptr->chromaticities) ==
0)
{
/* png_set_rgb_to_gray has not set the coefficients, get them from the
* Y * values of the colorspace colorants.
*/
png_fixed_point r = xyz.red_Y;
png_fixed_point g = xyz.green_Y;
png_fixed_point b = xyz.blue_Y;
png_fixed_point total = r+g+b;
if (total >
0 &&
r >=
0 && png_muldiv(&r, r,
32768, total) && r >=
0 && r <=
32768 &&
g >=
0 && png_muldiv(&g, g,
32768, total) && g >=
0 && g <=
32768 &&
b >=
0 && png_muldiv(&b, b,
32768, total) && b >=
0 && b <=
32768 &&
r+g+b <=
32769)
{
/* We allow 0 coefficients here. r+g+b may be 32769 if two or
* all of the coefficients were rounded up. Handle this by
* reducing the *largest* coefficient by 1; this matches the
* approach used for the default coefficients in pngrtran.c
*/
int add =
0;
if (r+g+b >
32768)
add = -
1;
else if (r+g+b <
32768)
add =
1;
if (add !=
0)
{
if (g >= r && g >= b)
g += add;
else if (r >= g && r >= b)
r += add;
else
b += add;
}
/* Check for an internal error. */
if (r+g+b !=
32768)
png_error(png_ptr,
"internal error handling cHRM coefficients");
else
{
png_ptr->rgb_to_gray_red_coeff = (png_uint_16)r;
png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g;
}
}
}
else
# endif
/* check_chromaticities */
{
/* Use the historical REC 709 (etc) values: */
png_ptr->rgb_to_gray_red_coeff =
6968;
png_ptr->rgb_to_gray_green_coeff =
23434;
/* png_ptr->rgb_to_gray_blue_coeff = 2366; */
}
}
}
#endif /* READ_RGB_TO_GRAY */
void /* PRIVATE */
png_check_IHDR(png_const_structrp png_ptr,
png_uint_32 width, png_uint_32 height,
int bit_depth,
int color_type,
int interlace_type,
int compression_type,
int filter_type)
{
int error =
0;
/* Check for width and height valid values */
if (width ==
0)
{
png_warning(png_ptr,
"Image width is zero in IHDR");
error =
1;
}
if (width > PNG_UINT_31_MAX)
{
png_warning(png_ptr,
"Invalid image width in IHDR");
error =
1;
}
/* The bit mask on the first line below must be at least as big as a
* png_uint_32. "~7U" is not adequate on 16-bit systems because it will
* be an unsigned 16-bit value. Casting to (png_alloc_size_t) makes the
* type of the result at least as bit (in bits) as the RHS of the > operator
* which also avoids a common warning on 64-bit systems that the comparison
* of (png_uint_32) against the constant value on the RHS will always be
* false.
*/
if (((width +
7) & ~(png_alloc_size_t)
7) >
(((PNG_SIZE_MAX
-
48 /* big_row_buf hack */
-
1)
/* filter byte */
/
8)
/* 8-byte RGBA pixels */
-
1))
/* extra max_pixel_depth pad */
{
/* The size of the row must be within the limits of this architecture.
* Because the read code can perform arbitrary transformations the
* maximum size is checked here. Because the code in png_read_start_row
* adds extra space "for safety's sake" in several places a conservative
* limit is used here.
*
* NOTE: it would be far better to check the size that is actually used,
* but the effect in the real world is minor and the changes are more
* extensive, therefore much more dangerous and much more difficult to
* write in a way that avoids compiler warnings.
*/
png_warning(png_ptr,
"Image width is too large for this architecture");
error =
1;
}
#ifdef PNG_SET_USER_LIMITS_SUPPORTED
if (width > png_ptr->user_width_max)
#else
if (width > PNG_USER_WIDTH_MAX)
#endif
{
png_warning(png_ptr,
"Image width exceeds user limit in IHDR");
error =
1;
}
if (height ==
0)
{
png_warning(png_ptr,
"Image height is zero in IHDR");
error =
1;
}
if (height > PNG_UINT_31_MAX)
{
png_warning(png_ptr,
"Invalid image height in IHDR");
error =
1;
}
#ifdef PNG_SET_USER_LIMITS_SUPPORTED
if (height > png_ptr->user_height_max)
#else
if (height > PNG_USER_HEIGHT_MAX)
#endif
{
png_warning(png_ptr,
"Image height exceeds user limit in IHDR");
error =
1;
}
/* Check other values */
if (bit_depth !=
1 && bit_depth !=
2 && bit_depth !=
4 &&
bit_depth !=
8 && bit_depth !=
16)
{
png_warning(png_ptr,
"Invalid bit depth in IHDR");
error =
1;
}
if (color_type <
0 || color_type ==
1 ||
color_type ==
5 || color_type >
6)
{
png_warning(png_ptr,
"Invalid color type in IHDR");
error =
1;
}
if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth >
8) ||
((color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth <
8))
{
png_warning(png_ptr,
"Invalid color type/bit depth combination in IHDR");
error =
1;
}
if (interlace_type >= PNG_INTERLACE_LAST)
{
png_warning(png_ptr,
"Unknown interlace method in IHDR");
error =
1;
}
if (compression_type != PNG_COMPRESSION_TYPE_BASE)
{
png_warning(png_ptr,
"Unknown compression method in IHDR");
error =
1;
}
#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Accept filter_method 64 (intrapixel differencing) only if
* 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
* 2. Libpng did not read a PNG signature (this filter_method is only
* used in PNG datastreams that are embedded in MNG datastreams) and
* 3. The application called png_permit_mng_features with a mask that
* included PNG_FLAG_MNG_FILTER_64 and
* 4. The filter_method is 64 and
* 5. The color_type is RGB or RGBA
*/
if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) !=
0 &&
png_ptr->mng_features_permitted !=
0)
png_warning(png_ptr,
"MNG features are not allowed in a PNG datastream");
if (filter_type != PNG_FILTER_TYPE_BASE)
{
if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) !=
0 &&
(filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&
((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) ==
0) &&
(color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
{
png_warning(png_ptr,
"Unknown filter method in IHDR");
error =
1;
}
if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) !=
0)
{
png_warning(png_ptr,
"Invalid filter method in IHDR");
error =
1;
}
}
#else
if (filter_type != PNG_FILTER_TYPE_BASE)
{
png_warning(png_ptr,
"Unknown filter method in IHDR");
error =
1;
}
#endif
if (error ==
1)
png_error(png_ptr,
"Invalid IHDR data");
}
#if defined(PNG_sCAL_SUPPORTED) ||
defined(PNG_pCAL_SUPPORTED)
/* ASCII to fp functions */
/* Check an ASCII formatted floating point value, see the more detailed
* comments in pngpriv.h
*/
/* The following is used internally to preserve the sticky flags */
#define png_fp_add(state, flags) ((state) |= (flags))
#define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
int /* PRIVATE */
png_check_fp_number(png_const_charp string, size_t size,
int *statep,
size_t *whereami)
{
int state = *statep;
size_t i = *whereami;
while (i < size)
{
int type;
/* First find the type of the next character */
switch (string[i])
{
case 43: type = PNG_FP_SAW_SIGN;
break;
case 45: type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE;
break;
case 46: type = PNG_FP_SAW_DOT;
break;
case 48: type = PNG_FP_SAW_DIGIT;
break;
case 49:
case 50:
case 51:
case 52:
case 53:
case 54:
case 55:
case 56:
case 57: type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO;
break;
case 69:
case 101: type = PNG_FP_SAW_E;
break;
default:
goto PNG_FP_End;
}
/* Now deal with this type according to the current
* state, the type is arranged to not overlap the
* bits of the PNG_FP_STATE.
*/
switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
{
case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
if ((state & PNG_FP_SAW_ANY) !=
0)
goto PNG_FP_End;
/* not a part of the number */
png_fp_add(state, type);
break;
case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
/* Ok as trailer, ok as lead of fraction. */
if ((state & PNG_FP_SAW_DOT) !=
0)
/* two dots */
goto PNG_FP_End;
else if ((state & PNG_FP_SAW_DIGIT) !=
0)
/* trailing dot? */
png_fp_add(state, type);
else
png_fp_set(state, PNG_FP_FRACTION | type);
break;
case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
if ((state & PNG_FP_SAW_DOT) !=
0)
/* delayed fraction */
png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);
png_fp_add(state, type | PNG_FP_WAS_VALID);
break;
case PNG_FP_INTEGER + PNG_FP_SAW_E:
if ((state & PNG_FP_SAW_DIGIT) ==
0)
goto PNG_FP_End;
png_fp_set(state, PNG_FP_EXPONENT);
break;
/* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
goto PNG_FP_End; ** no sign in fraction */
/* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
goto PNG_FP_End; ** Because SAW_DOT is always set */
case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
png_fp_add(state, type | PNG_FP_WAS_VALID);
break;
case PNG_FP_FRACTION + PNG_FP_SAW_E:
/* This is correct because the trailing '.' on an
* integer is handled above - so we can only get here
* with the sequence ".E" (with no preceding digits).
*/
if ((state & PNG_FP_SAW_DIGIT) ==
0)
goto PNG_FP_End;
png_fp_set(state, PNG_FP_EXPONENT);
break;
case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
if ((state & PNG_FP_SAW_ANY) !=
0)
goto PNG_FP_End;
/* not a part of the number */
png_fp_add(state, PNG_FP_SAW_SIGN);
break;
/* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
goto PNG_FP_End; */
case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);
break;
/* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
goto PNG_FP_End; */
default:
goto PNG_FP_End;
/* I.e. break 2 */
}
/* The character seems ok, continue. */
++i;
}
PNG_FP_End:
/* Here at the end, update the state and return the correct
* return code.
*/
*statep = state;
*whereami = i;
return (state & PNG_FP_SAW_DIGIT) !=
0;
}
/* The same but for a complete string. */
int
png_check_fp_string(png_const_charp string, size_t size)
{
int state =
0;
size_t char_index =
0;
if (png_check_fp_number(string, size, &state, &char_index) !=
0 &&
(char_index == size || string[char_index] ==
0))
return state
/* must be non-zero - see above */;
return 0;
/* i.e. fail */
}
#endif /* pCAL || sCAL */
#ifdef PNG_sCAL_SUPPORTED
# ifdef PNG_FLOATING_POINT_SUPPORTED
/* Utility used below - a simple accurate power of ten from an integral
* exponent.
*/
static double
png_pow10(
int power)
{
int recip =
0;
double d =
1;
/* Handle negative exponent with a reciprocal at the end because
* 10 is exact whereas .1 is inexact in base 2
*/
if (power <
0)
{
if (power < DBL_MIN_10_EXP)
return 0;
recip =
1; power = -power;
}
if (power >
0)
{
/* Decompose power bitwise. */
double mult =
10;
do
{
if (power &
1) d *= mult;
mult *= mult;
power >>=
1;
}
while (power >
0);
if (recip !=
0) d =
1/d;
}
/* else power is 0 and d is 1 */
return d;
}
/* Function to format a floating point value in ASCII with a given
* precision.
*/
void /* PRIVATE */
png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size,
double fp,
unsigned int precision)
{
/* We use standard functions from math.h, but not printf because
* that would require stdio. The caller must supply a buffer of
* sufficient size or we will png_error. The tests on size and
* the space in ascii[] consumed are indicated below.
*/
if (precision <
1)
precision = DBL_DIG;
/* Enforce the limit of the implementation precision too. */
if (precision > DBL_DIG+
1)
precision = DBL_DIG+
1;
/* Basic sanity checks */
if (size >= precision+
5)
/* See the requirements below. */
{
if (fp <
0)
{
fp = -fp;
*ascii++ =
45;
/* '-' PLUS 1 TOTAL 1 */
--size;
}
if (fp >= DBL_MIN && fp <= DBL_MAX)
{
int exp_b10;
/* A base 10 exponent */
double base;
/* 10^exp_b10 */
/* First extract a base 10 exponent of the number,
* the calculation below rounds down when converting
* from base 2 to base 10 (multiply by log10(2) -
* 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
* be increased. Note that the arithmetic shift
* performs a floor() unlike C arithmetic - using a
* C multiply would break the following for negative
* exponents.
*/
(
void)frexp(fp, &exp_b10);
/* exponent to base 2 */
exp_b10 = (exp_b10 *
77) >>
8;
/* <= exponent to base 10 */
/* Avoid underflow here. */
base = png_pow10(exp_b10);
/* May underflow */
while (base < DBL_MIN || base < fp)
{
/* And this may overflow. */
double test = png_pow10(exp_b10+
1);
if (test <= DBL_MAX)
{
++exp_b10; base = test;
}
else
break;
}
/* Normalize fp and correct exp_b10, after this fp is in the
* range [.1,1) and exp_b10 is both the exponent and the digit
* *before* which the decimal point should be inserted
* (starting with 0 for the first digit). Note that this
* works even if 10^exp_b10 is out of range because of the
* test on DBL_MAX above.
*/
fp /= base;
while (fp >=
1)
{
fp /=
10; ++exp_b10;
}
/* Because of the code above fp may, at this point, be
* less than .1, this is ok because the code below can
* handle the leading zeros this generates, so no attempt
* is made to correct that here.
*/
{
unsigned int czero, clead, cdigits;
char exponent[
10];
/* Allow up to two leading zeros - this will not lengthen
* the number compared to using E-n.
*/
if (exp_b10 <
0 && exp_b10 > -
3)
/* PLUS 3 TOTAL 4 */
{
czero =
0U-exp_b10;
/* PLUS 2 digits: TOTAL 3 */
exp_b10 =
0;
/* Dot added below before first output. */
}
else
czero =
0;
/* No zeros to add */
/* Generate the digit list, stripping trailing zeros and
* inserting a '.' before a digit if the exponent is 0.
*/
clead = czero;
/* Count of leading zeros */
cdigits =
0;
/* Count of digits in list. */
do
{
double d;
fp *=
10;
/* Use modf here, not floor and subtract, so that
* the separation is done in one step. At the end
* of the loop don't break the number into parts so
* that the final digit is rounded.
*/
if (cdigits+czero+
1 < precision+clead)
fp = modf(fp, &d);
else
{
d = floor(fp + .
5);
if (d >
9)
{
/* Rounding up to 10, handle that here. */
if (czero >
0)
{
--czero; d =
1;
if (cdigits ==
0) --clead;
}
else
{
while (cdigits >
0 && d >
9)
{
int ch = *--ascii;
if (exp_b10 != (-
1))
++exp_b10;
else if (ch ==
46)
{
ch = *--ascii; ++size;
/* Advance exp_b10 to '1', so that the
* decimal point happens after the
* previous digit.
*/
exp_b10 =
1;
}
--cdigits;
d = ch -
47;
/* I.e. 1+(ch-48) */
}
/* Did we reach the beginning? If so adjust the
* exponent but take into account the leading
* decimal point.
*/
if (d >
9)
/* cdigits == 0 */
{
if (exp_b10 == (-
1))
{
/* Leading decimal point (plus zeros?), if
* we lose the decimal point here it must
* be reentered below.
*/
int ch = *--ascii;
if (ch ==
46)
{
++size; exp_b10 =
1;
}
/* Else lost a leading zero, so 'exp_b10' is
* still ok at (-1)
*/
}
else
++exp_b10;
/* In all cases we output a '1' */
d =
1;
}
}
}
fp =
0;
/* Guarantees termination below. */
}
if (d ==
0)
{
++czero;
if (cdigits ==
0) ++clead;
}
else
{
/* Included embedded zeros in the digit count. */
cdigits += czero - clead;
clead =
0;
while (czero >
0)
{
/* exp_b10 == (-1) means we just output the decimal
* place - after the DP don't adjust 'exp_b10' any
* more!
*/
if (exp_b10 != (-
1))
{
if (exp_b10 ==
0)
{
*ascii++ =
46; --size;
}
/* PLUS
1: TOTAL
4 */
--exp_b10;
}
*ascii++ =
48; --czero;
}
if (exp_b10 != (-
1))
{
if (exp_b10 ==
0)
{
*ascii++ =
46; --size; /* counted above */
}
--exp_b10;
}
*ascii++ = (char)(
48 + (int)d); ++cdigits;
}
}
while (cdigits+czero < precision+clead && fp > DBL_MIN);
/* The total output count (max) is now
4+precision */
/* Check for an exponent, if we don't need one we are
* done and just need to terminate the string. At this
* point, exp_b10==(-
1) is effectively a flag: it got
* to '-
1' because of the decrement, after outputting
* the decimal point above. (The exponent required is
* *not* -
1.)
*/
if (exp_b10 >= (-
1) && exp_b10 <=
2)
{
/* The following only happens if we didn't output the
* leading zeros above for negative exponent, so this
* doesn't add to the digit requirement. Note that the
* two zeros here can only be output if the two leading
* zeros were *not* output, so this doesn't increase
* the output count.
*/
while (exp_b10-- >
0) *ascii++ =
48;
*ascii =
0;
/* Total buffer requirement (including the '\
0') is
*
5+precision - see check at the start.
*/
return;
}
/* Here if an exponent is required, adjust size for
* the digits we output but did not count. The total
* digit output here so far is at most
1+precision - no
* decimal point and no leading or trailing zeros have
* been output.
*/
size -= cdigits;
*ascii++ =
69; --size; /* 'E': PLUS
1 TOTAL
2+precision */
/* The following use of an unsigned temporary avoids ambiguities in
* the signed arithmetic on exp_b10 and permits GCC at least to do
* better optimization.
*/
{
unsigned int uexp_b10;
if (exp_b10 <
0)
{
*ascii++ =
45; --size; /* '-': PLUS
1 TOTAL
3+precision */
uexp_b10 =
0U-exp_b10;
}
else
uexp_b10 =
0U+exp_b10;
cdigits =
0;
while (uexp_b10 >
0)
{
exponent[cdigits++] = (char)(
48 + uexp_b10 %
10);
uexp_b10 /=
10;
}
}
/* Need another size check here for the exponent digits, so
* this need not be considered above.
*/
if (size > cdigits)
{
while (cdigits >
0) *ascii++ = exponent[--cdigits];
*ascii =
0;
return;
}
}
}
else if (!(fp >= DBL_MIN))
{
*ascii++ =
48; /* '
0' */
*ascii =
0;
return;
}
else
{
*ascii++ =
105; /* 'i' */
*ascii++ =
110; /* 'n' */
*ascii++ =
102; /* 'f' */
*ascii =
0;
return;
}
}
/* Here on buffer too small. */
png_error(png_ptr, "ASCII conversion buffer too small");
}
# endif /* FLOATING_POINT */
# ifdef PNG_FIXED_POINT_SUPPORTED
/* Function to format a fixed point value in ASCII.
*/
void /* PRIVATE */
png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
size_t size, png_fixed_point fp)
{
/* Require space for
10 decimal digits, a decimal point, a minus sign and a
* trailing \
0,
13 characters:
*/
if (size >
12)
{
png_uint_32 num;
/* Avoid overflow here on the minimum integer. */
if (fp <
0)
{
*ascii++ =
45; num = (png_uint_32)(-fp);
}
else
num = (png_uint_32)fp;
if (num <=
0x80000000) /* else overflowed */
{
unsigned int ndigits =
0, first =
16 /* flag value */;
char digits[
10] = {
0};
while (num)
{
/* Split the low digit off num: */
unsigned int tmp = num/
10;
num -= tmp*
10;
digits[ndigits++] = (char)(
48 + num);
/* Record the first non-zero digit, note that this is a number
* starting at
1, it's not actually the array index.
*/
if (first ==
16 && num >
0)
first = ndigits;
num = tmp;
}
if (ndigits >
0)
{
while (ndigits >
5) *ascii++ = digits[--ndigits];
/* The remaining digits are fractional digits, ndigits is '
5' or
* smaller at this point. It is certainly not zero. Check for a
* non-zero fractional digit:
*/
if (first <=
5)
{
unsigned int i;
*ascii++ =
46; /* decimal point */
/* ndigits may be <
5 for small numbers, output leading zeros
* then ndigits digits to first:
*/
i =
5;
while (ndigits < i)
{
*ascii++ =
48; --i;
}
while (ndigits >= first) *ascii++ = digits[--ndigits];
/* Don't output the trailing zeros! */
}
}
else
*ascii++ =
48;
/* And null terminate the string: */
*ascii =
0;
return;
}
}
/* Here on buffer too small. */
png_error(png_ptr, "ASCII conversion buffer too small");
}
# endif /* FIXED_POINT */
#endif /* SCAL */
#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
!defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
(defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
(defined(PNG_sCAL_SUPPORTED) && \
defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
png_fixed_point
png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
{
double r = floor(
100000 * fp + .
5);
if (r >
2147483647. || r < -
2147483648.)
png_fixed_error(png_ptr, text);
# ifndef PNG_ERROR_TEXT_SUPPORTED
PNG_UNUSED(text)
# endif
return (png_fixed_point)r;
}
#endif
#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
!defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
(defined(PNG_cLLI_SUPPORTED) || defined(PNG_mDCV_SUPPORTED))
png_uint_32
png_fixed_ITU(png_const_structrp png_ptr, double fp, png_const_charp text)
{
double r = floor(
10000 * fp + .
5);
if (r >
2147483647. || r <
0)
png_fixed_error(png_ptr, text);
# ifndef PNG_ERROR_TEXT_SUPPORTED
PNG_UNUSED(text)
# endif
return (png_uint_32)r;
}
#endif
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\
defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
/* muldiv functions */
/* This API takes signed arguments and rounds the result to the nearest
* integer (or, for a fixed point number - the standard argument - to
* the nearest .
00001). Overflow and divide by zero are signalled in
* the result, a boolean - true on success, false on overflow.
*/
int /* PRIVATE */
png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
png_int_32 divisor)
{
/* Return a * times / divisor, rounded. */
if (divisor !=
0)
{
if (a ==
0 || times ==
0)
{
*res =
0;
return
1;
}
else
{
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
double r = a;
r *= times;
r /= divisor;
r = floor(r+.
5);
/* A png_fixed_point is a
32-bit integer. */
if (r <=
2147483647. && r >= -
2147483648.)
{
*res = (png_fixed_point)r;
return
1;
}
#else
int negative =
0;
png_uint_32 A, T, D;
png_uint_32 s16, s32, s00;
if (a <
0)
negative =
1, A = -a;
else
A = a;
if (times <
0)
negative = !negative, T = -times;
else
T = times;
if (divisor <
0)
negative = !negative, D = -divisor;
else
D = divisor;
/* Following can't overflow because the arguments only
* have
31 bits each, however the result may be
32 bits.
*/
s16 = (A >>
16) * (T &
0xffff) +
(A &
0xffff) * (T >>
16);
/* Can't overflow because the a*times bit is only
30
* bits at most.
*/
s32 = (A >>
16) * (T >>
16) + (s16 >>
16);
s00 = (A &
0xffff) * (T &
0xffff);
s16 = (s16 &
0xffff) <<
16;
s00 += s16;
if (s00 < s16)
++s32; /* carry */
if (s32 < D) /* else overflow */
{
/* s32.s00 is now the
64-bit product, do a standard
* division, we know that s32 < D, so the maximum
* required shift is
31.
*/
int bitshift =
32;
png_fixed_point result =
0; /* NOTE: signed */
while (--bitshift >=
0)
{
png_uint_32 d32, d00;
if (bitshift >
0)
d32 = D >> (
32-bitshift), d00 = D << bitshift;
else
d32 =
0, d00 = D;
if (s32 > d32)
{
if (s00 < d00) --s32; /* carry */
s32 -= d32, s00 -= d00, result +=
1<<bitshift;
}
else
if (s32 == d32 && s00 >= d00)
s32 =
0, s00 -= d00, result +=
1<<bitshift;
}
/* Handle the rounding. */
if (s00 >= (D >>
1))
++result;
if (negative !=
0)
result = -result;
/* Check for overflow. */
if ((negative !=
0 && result <=
0) ||
(negative ==
0 && result >=
0))
{
*res = result;
return
1;
}
}
#endif
}
}
return
0;
}
/* Calculate a reciprocal, return
0 on div-by-zero or overflow. */
png_fixed_point
png_reciprocal(png_fixed_point a)
{
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
double r = floor(
1E10/a+.
5);
if (r <=
2147483647. && r >= -
2147483648.)
return (png_fixed_point)r;
#else
png_fixed_point res;
if (png_muldiv(&res,
100000,
100000, a) !=
0)
return res;
#endif
return
0; /* error/overflow */
}
#endif /* READ_GAMMA || COLORSPACE || INCH_CONVERSIONS || READ_pHYS */
#ifdef PNG_READ_GAMMA_SUPPORTED
/* This is the shared test on whether a gamma value is 'significant' - whether
* it is worth doing gamma correction.
*/
int /* PRIVATE */
png_gamma_significant(png_fixed_point gamma_val)
{
/* sRGB:
1/
2.
2 ==
0.
4545(
45)
* AdobeRGB:
1/(
2+
51/
256) ~=
0.
45471 5dp
*
* So the correction from AdobeRGB to sRGB (output) is:
*
*
2.
2/(
2+
51/
256) ==
1.
00035524
*
* I.e. vanishingly small (<
4E-
4) but still detectable in
16-bit linear (+/-
*
23). Note that the Adobe choice seems to be something intended to give an
* exact number with
8 binary fractional digits - it is the closest to
2.
2
* that is possible a base
2 .
8p representation.
*/
return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED ||
gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED;
}
#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* A local convenience routine. */
static png_fixed_point
png_product2(png_fixed_point a, png_fixed_point b)
{
/* The required result is a * b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED /* Should now be unused */
double r = a *
1E-
5;
r *= b;
r = floor(r+.
5);
if (r <=
2147483647. && r >= -
2147483648.)
return (png_fixed_point)r;
#else
png_fixed_point res;
if (png_muldiv(&res, a, b,
100000) !=
0)
return res;
#endif
return
0; /* overflow */
}
#endif /* FLOATING_ARITHMETIC */
png_fixed_point
png_reciprocal2(png_fixed_point a, png_fixed_point b)
{
/* The required result is
1/a *
1/b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
if (a !=
0 && b !=
0)
{
double r =
1E15/a;
r /= b;
r = floor(r+.
5);
if (r <=
2147483647. && r >= -
2147483648.)
return (png_fixed_point)r;
}
#else
/* This may overflow because the range of png_fixed_point isn't symmetric,
* but this API is only used for the product of file and screen gamma so it
* doesn't matter that the smallest number it can produce is
1/
21474, not
*
1/
100000
*/
png_fixed_point res = png_product2(a, b);
if (res !=
0)
return png_reciprocal(res);
#endif
return
0; /* overflow */
}
#endif /* READ_GAMMA */
#ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */
#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* Fixed point gamma.
*
* The code to calculate the tables used below can be found in the shell script
* contrib/tools/intgamma.sh
*
* To calculate gamma this code implements fast log() and exp() calls using only
* fixed point arithmetic. This code has sufficient precision for either
8-bit
* or
16-bit sample values.
*
* The tables used here were calculated using simple 'bc' programs, but C double
* precision floating point arithmetic would work fine.
*
*
8-bit log table
* This is a table of -log(value/
255)/log(
2) for 'value' in the range
128 to
*
255, so it's the base
2 logarithm of a normalized
8-bit floating point
* mantissa. The numbers are
32-bit fractions.
*/
static const png_uint_32
png_8bit_l2[
128] =
{
4270715492U,
4222494797U,
4174646467U,
4127164793U,
4080044201U,
4033279239U,
3986864580U,
3940795015U,
3895065449U,
3849670902U,
3804606499U,
3759867474U,
3715449162U,
3671346997U,
3627556511U,
3584073329U,
3540893168U,
3498011834U,
3455425220U,
3413129301U,
3371120137U,
3329393864U,
3287946700U,
3246774933U,
3205874930U,
3165243125U,
3124876025U,
3084770202U,
3044922296U,
3005329011U,
2965987113U,
2926893432U,
2888044853U,
2849438323U,
2811070844U,
2772939474U,
2735041326U,
2697373562U,
2659933400U,
2622718104U,
2585724991U,
2548951424U,
2512394810U,
2476052606U,
2439922311U,
2404001468U,
2368287663U,
2332778523U,
2297471715U,
2262364947U,
2227455964U,
2192742551U,
2158222529U,
2123893754U,
2089754119U,
2055801552U,
2022034013U,
1988449497U,
1955046031U,
1921821672U,
1888774511U,
1855902668U,
1823204291U,
1790677560U,
1758320682U,
1726131893U,
1694109454U,
1662251657U,
1630556815U,
1599023271U,
1567649391U,
1536433567U,
1505374214U,
1474469770U,
1443718700U,
1413119487U,
1382670639U,
1352370686U,
1322218179U,
1292211689U,
1262349810U,
1232631153U,
1203054352U,
1173618059U,
1144320946U,
1115161701U,
1086139034U,
1057251672U,
1028498358U,
999877854U,
971388940U,
943030410U,
914801076U,
886699767U,
858725327U,
830876614U,
803152505U,
775551890U,
748073672U,
720716771U,
693480120U,
666362667U,
639363374U,
612481215U,
585715177U,
559064263U,
532527486U,
506103872U,
479792461U,
453592303U,
427502463U,
401522014U,
375650043U,
349885648U,
324227938U,
298676034U,
273229066U,
247886176U,
222646516U,
197509248U,
172473545U,
147538590U,
122703574U,
97967701U,
73330182U,
48790236U,
24347096U,
0U
#if
0
/* The following are the values for
16-bit tables - these work fine for the
*
8-bit conversions but produce very slightly larger errors in the
16-bit
* log (about
1.
2 as opposed to
0.
7 absolute error in the final value). To
* use these all the shifts below must be adjusted appropriately.
*/
65166,
64430,
63700,
62976,
62257,
61543,
60835,
60132,
59434,
58741,
58054,
57371,
56693,
56020,
55352,
54689,
54030,
53375,
52726,
52080,
51439,
50803,
50170,
49542,
48918,
48298,
47682,
47070,
46462,
45858,
45257,
44661,
44068,
43479,
42894,
42312,
41733,
41159,
40587,
40020,
39455,
38894,
38336,
37782,
37230,
36682,
36137,
35595,
35057,
34521,
33988,
33459,
32932,
32408,
31887,
31369,
30854,
30341,
29832,
29325,
28820,
28319,
27820,
27324,
26830,
26339,
25850,
25364,
24880,
24399,
23920,
23444,
22970,
22499,
22029,
21562,
21098,
20636,
20175,
19718,
19262,
18808,
18357,
17908,
17461,
17016,
16573,
16132,
15694,
15257,
14822,
14390,
13959,
13530,
13103,
12678,
12255,
11834,
11415,
10997,
10582,
10168,
9756,
9346,
8937,
8531,
8126,
7723,
7321,
6921,
6523,
6127,
5732,
5339,
4947,
4557,
4169,
3782,
3397,
3014,
2632,
2251,
1872,
1495,
1119,
744,
372
#endif
};
static png_int_32
png_log8bit(unsigned int x)
{
unsigned int lg2 =
0;
/* Each time 'x' is multiplied by
2,
1 must be subtracted off the final log,
* because the log is actually negate that means adding
1. The final
* returned value thus has the range
0 (for
255 input) to
7.
994 (for
1
* input), return -
1 for the overflow (log
0) case, - so the result is
* always at most
19 bits.
*/
if ((x &=
0xff) ==
0)
return -
1;
if ((x &
0xf0) ==
0)
lg2 =
4, x <<=
4;
if ((x &
0xc0) ==
0)
lg2 +=
2, x <<=
2;
if ((x &
0x80) ==
0)
lg2 +=
1, x <<=
1;
/* result is at most
19 bits, so this cast is safe: */
return (png_int_32)((lg2 <<
16) + ((png_8bit_l2[x-
128]+
32768)>>
16));
}
/* The above gives exact (to
16 binary places) log2 values for
8-bit images,
* for
16-bit images we use the most significant
8 bits of the
16-bit value to
* get an approximation then multiply the approximation by a correction factor
* determined by the remaining up to
8 bits. This requires an additional step
* in the
16-bit case.
*
* We want log2(value/
65535), we have log2(v'/
255), where:
*
* value = v' *
256 + v''
* = v' * f
*
* So f is value/v', which is equal to (
256+v''/v') since v' is in the range
128
* to
255 and v'' is in the range
0 to
255 f will be in the range
256 to less
* than
258. The final factor also needs to correct for the fact that our
8-bit
* value is scaled by
255, whereas the
16-bit values must be scaled by
65535.
*
* This gives a final formula using a calculated value 'x' which is value/v' and
* scaling by
65536 to match the above table:
*
* log2(x/
257) *
65536
*
* Since these numbers are so close to '
1' we can use simple linear
* interpolation between the two end values
256/
257 (result -
368.
61) and
258/
257
* (result
367.
179). The values used below are scaled by a further
64 to give
*
16-bit precision in the interpolation:
*
* Start (
256): -
23591
* Zero (
257):
0
* End (
258):
23499
*/
#ifdef PNG_16BIT_SUPPORTED
static png_int_32
png_log16bit(png_uint_32 x)
{
unsigned int lg2 =
0;
/* As above, but now the input has
16 bits. */
if ((x &=
0xffff) ==
0)
return -
1;
if ((x &
0xff00) ==
0)
lg2 =
8, x <<=
8;
if ((x &
0xf000) ==
0)
lg2 +=
4, x <<=
4;
if ((x &
0xc000) ==
0)
lg2 +=
2, x <<=
2;
if ((x &
0x8000) ==
0)
lg2 +=
1, x <<=
1;
/* Calculate the base logarithm from the top
8 bits as a
28-bit fractional
* value.
*/
lg2 <<=
28;
lg2 += (png_8bit_l2[(x>>
8)-
128]+
8) >>
4;
/* Now we need to interpolate the factor, this requires a division by the top
*
8 bits. Do this with maximum precision.
*/
x = ((x <<
16) + (x >>
9)) / (x >>
8);
/* Since we divided by the top
8 bits of 'x' there will be a '
1' at
1<<
24,
* the value at
1<<
16 (ignoring this) will be
0 or
1; this gives us exactly
*
16 bits to interpolate to get the low bits of the result. Round the
* answer. Note that the end point values are scaled by
64 to retain overall
* precision and that 'lg2' is current scaled by an extra
12 bits, so adjust
* the overall scaling by
6-
12. Round at every step.
*/
x -=
1U <<
24;
if (x <=
65536U) /* <= '
257' */
lg2 += ((
23591U * (
65536U-x)) + (
1U << (
16+
6-
12-
1))) >> (
16+
6-
12);
else
lg2 -= ((
23499U * (x-
65536U)) + (
1U << (
16+
6-
12-
1))) >> (
16+
6-
12);
/* Safe, because the result can't have more than
20 bits: */
return (png_int_32)((lg2 +
2048) >>
12);
}
#endif /*
16BIT */
/* The 'exp()' case must invert the above, taking a
20-bit fixed point
* logarithmic value and returning a
16 or
8-bit number as appropriate. In
* each case only the low
16 bits are relevant - the fraction - since the
* integer bits (the top
4) simply determine a shift.
*
* The worst case is the
16-bit distinction between
65535 and
65534. This
* requires perhaps spurious accuracy in the decoding of the logarithm to
* distinguish log2(
65535/
65534.
5) -
10^-
5 or
17 bits. There is little chance
* of getting this accuracy in practice.
*
* To deal with this the following exp() function works out the exponent of the
* fractional part of the logarithm by using an accurate
32-bit value from the
* top four fractional bits then multiplying in the remaining bits.
*/
static const png_uint_32
png_32bit_exp[
16] =
{
/* NOTE: the first entry is deliberately set to the maximum
32-bit value. */
4294967295U,
4112874773U,
3938502376U,
3771522796U,
3611622603U,
3458501653U,
3311872529U,
3171459999U,
3037000500U,
2908241642U,
2784941738U,
2666869345U,
2553802834U,
2445529972U,
2341847524U,
2242560872U
};
/* Adjustment table; provided to explain the numbers in the code below. */
#if
0
for (i=
11;i>=
0;--i){ print i, " ", (
1 - e(-(
2^i)/
65536*l(
2))) *
2^(
32-i), "\n"}
11 44937.
64284865548751208448
10 45180.
98734845585101160448
9 45303.
31936980687359311872
8 45364.
65110595323018870784
7 45395.
35850361789624614912
6 45410.
72259715102037508096
5 45418.
40724413220722311168
4 45422.
25021786898173001728
3 45424.
17186732298419044352
2 45425.
13273269940811464704
1 45425.
61317555035558641664
0 45425.
85339951654943850496
#endif
static png_uint_32
png_exp(png_fixed_point x)
{
if (x >
0 && x <=
0xfffff) /* Else overflow or zero (underflow) */
{
/* Obtain a
4-bit approximation */
png_uint_32 e = png_32bit_exp[(x >>
12) &
0x0f];
/* Incorporate the low
12 bits - these decrease the returned value by
* multiplying by a number less than
1 if the bit is set. The multiplier
* is determined by the above table and the shift. Notice that the values
* converge on
45426 and this is used to allow linear interpolation of the
* low bits.
*/
if (x &
0x800)
e -= (((e >>
16) *
44938U) +
16U) >>
5;
if (x &
0x400)
e -= (((e >>
16) *
45181U) +
32U) >>
6;
if (x &
0x200)
e -= (((e >>
16) *
45303U) +
64U) >>
7;
if (x &
0x100)
e -= (((e >>
16) *
45365U) +
128U) >>
8;
if (x &
0x080)
e -= (((e >>
16) *
45395U) +
256U) >>
9;
if (x &
0x040)
e -= (((e >>
16) *
45410U) +
512U) >>
10;
/* And handle the low
6 bits in a single block. */
e -= (((e >>
16) *
355U * (x &
0x3fU)) +
256U) >>
9;
/* Handle the upper bits of x. */
e >>= x >>
16;
return e;
}
/* Check for overflow */
if (x <=
0)
return png_32bit_exp[
0];
/* Else underflow */
return
0;
}
static png_byte
png_exp8bit(png_fixed_point lg2)
{
/* Get a
32-bit value: */
png_uint_32 x = png_exp(lg2);
/* Convert the
32-bit value to
0..
255 by multiplying by
256-
1. Note that the
* second, rounding, step can't overflow because of the first, subtraction,
* step.
*/
x -= x >>
8;
return (png_byte)(((x +
0x7fffffU) >>
24) &
0xff);
}
#ifdef PNG_16BIT_SUPPORTED
static png_uint_16
png_exp16bit(png_fixed_point lg2)
{
/* Get a
32-bit value: */
png_uint_32 x = png_exp(lg2);
/* Convert the
32-bit value to
0..
65535 by multiplying by
65536-
1: */
x -= x >>
16;
return (png_uint_16)((x +
32767U) >>
16);
}
#endif /*
16BIT */
#endif /* FLOATING_ARITHMETIC */
png_byte
png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val)
{
if (value >
0 && value <
255)
{
# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* 'value' is unsigned, ANSI-C90 requires the compiler to correctly
* convert this to a floating point value. This includes values that
* would overflow if 'value' were to be converted to 'int'.
*
* Apparently GCC, however, does an intermediate conversion to (int)
* on some (ARM) but not all (x86) platforms, possibly because of
* hardware FP limitations. (E.g. if the hardware conversion always
* assumes the integer register contains a signed value.) This results
* in ANSI-C undefined behavior for large values.
*
* Other implementations on the same machine might actually be ANSI-C90
* conformant and therefore compile spurious extra code for the large
* values.
*
* We can be reasonably sure that an unsigned to float conversion
* won't be faster than an int to float one. Therefore this code
* assumes responsibility for the undefined behavior, which it knows
* can't happen because of the check above.
*
* Note the argument to this routine is an (unsigned int) because, on
*
16-bit platforms, it is assigned a value which might be out of
* range for an (int); that would result in undefined behavior in the
* caller if the *argument* ('value') were to be declared (int).
*/
double r = floor(
255*pow((int)/*SAFE*/value/
255.,gamma_val*.
00001)+.
5);
return (png_byte)r;
# else
png_int_32 lg2 = png_log8bit(value);
png_fixed_point res;
if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) !=
0)
return png_exp8bit(res);
/* Overflow. */
value =
0;
# endif
}
return (png_byte)(value &
0xff);
}
#ifdef PNG_16BIT_SUPPORTED
png_uint_16
png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val)
{
if (value >
0 && value <
65535)
{
# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* The same (unsigned int)->(double) constraints apply here as above,
* however in this case the (unsigned int) to (int) conversion can
* overflow on an ANSI-C90 compliant system so the cast needs to ensure
* that this is not possible.
*/
double r = floor(
65535*pow((png_int_32)value/
65535.,
gamma_val*.
00001)+.
5);
return (png_uint_16)r;
# else
png_int_32 lg2 = png_log16bit(value);
png_fixed_point res;
if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) !=
0)
return png_exp16bit(res);
/* Overflow. */
value =
0;
# endif
}
return (png_uint_16)value;
}
#endif /*
16BIT */
/* This does the right thing based on the bit_depth field of the
* png_struct, interpreting values as
8-bit or
16-bit. While the result
* is nominally a
16-bit value if bit depth is
8 then the result is
*
8-bit (as are the arguments.)
*/
png_uint_16 /* PRIVATE */
png_gamma_correct(png_structrp png_ptr, unsigned int value,
png_fixed_point gamma_val)
{
if (png_ptr->bit_depth ==
8)
return png_gamma_8bit_correct(value, gamma_val);
#ifdef PNG_16BIT_SUPPORTED
else
return png_gamma_16bit_correct(value, gamma_val);
#else
/* should not reach this */
return
0;
#endif /*
16BIT */
}
#ifdef PNG_16BIT_SUPPORTED
/* Internal function to build a single
16-bit table - the table consists of
* 'num'
256 entry subtables, where 'num' is determined by 'shift' - the amount
* to shift the input values right (or
16-number_of_signifiant_bits).
*
* The caller is responsible for ensuring that the table gets cleaned up on
* png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument
* should be somewhere that will be cleaned.
*/
static void
png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
unsigned int shift, png_fixed_point gamma_val)
{
/* Various values derived from 'shift': */
unsigned int num =
1U << (
8U - shift);
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* CSE the division and work round wacky GCC warnings (see the comments
* in png_gamma_8bit_correct for where these come from.)
*/
double fmax =
1.
0 / (((png_int_32)
1 << (
16U - shift)) -
1);
#endif
unsigned int max = (
1U << (
16U - shift)) -
1U;
unsigned int max_by_2 =
1U << (
15U - shift);
unsigned int i;
png_uint_16pp table = *ptable =
(png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
for (i =
0; i < num; i++)
{
png_uint_16p sub_table = table[i] =
(png_uint_16p)png_malloc(png_ptr,
256 * (sizeof (png_uint_16)));
/* The 'threshold' test is repeated here because it can arise for one of
* the
16-bit tables even if the others don't hit it.
*/
if (png_gamma_significant(gamma_val) !=
0)
{
/* The old code would overflow at the end and this would cause the
* 'pow' function to return a result >
1, resulting in an
* arithmetic error. This code follows the spec exactly; ig is
* the recovered input sample, it always has
8-
16 bits.
*
* We want input *
65535/max, rounded, the arithmetic fits in
32
* bits (unsigned) so long as max <=
32767.
*/
unsigned int j;
for (j =
0; j <
256; j++)
{
png_uint_32 ig = (j << (
8-shift)) + i;
# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* Inline the 'max' scaling operation: */
/* See png_gamma_8bit_correct for why the cast to (int) is
* required here.
*/
double d = floor(
65535.*pow(ig*fmax, gamma_val*.
00001)+.
5);
sub_table[j] = (png_uint_16)d;
# else
if (shift !=
0)
ig = (ig *
65535U + max_by_2)/max;
sub_table[j] = png_gamma_16bit_correct(ig, gamma_val);
# endif
}
}
else
{
/* We must still build a table, but do it the fast way. */
unsigned int j;
for (j =
0; j <
256; j++)
{
png_uint_32 ig = (j << (
8-shift)) + i;
if (shift !=
0)
ig = (ig *
65535U + max_by_2)/max;
sub_table[j] = (png_uint_16)ig;
}
}
}
}
/* NOTE: this function expects the *inverse* of the overall gamma transformation
* required.
*/
static void
png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
unsigned int shift, png_fixed_point gamma_val)
{
unsigned int num =
1U << (
8U - shift);
unsigned int max = (
1U << (
16U - shift))-
1U;
unsigned int i;
png_uint_32 last;
png_uint_16pp table = *ptable =
(png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
/* 'num' is the number of tables and also the number of low bits of low
* bits of the input
16-bit value used to select a table. Each table is
* itself indexed by the high
8 bits of the value.
*/
for (i =
0; i < num; i++)
table[i] = (png_uint_16p)png_malloc(png_ptr,
256 * (sizeof (png_uint_16)));
/* 'gamma_val' is set to the reciprocal of the value calculated above, so
* pow(out,g) is an *input* value. 'last' is the last input value set.
*
* In the loop 'i' is used to find output values. Since the output is
*
8-bit there are only
256 possible values. The tables are set up to
* select the closest possible output value for each input by finding
* the input value at the boundary between each pair of output values
* and filling the table up to that boundary with the lower output
* value.
*
* The boundary values are
0.
5,
1.
5..
253.
5,
254.
5. Since these are
9-bit
* values the code below uses a
16-bit value in i; the values start at
*
128.
5 (for
0.
5) and step by
257, for a total of
254 values (the last
* entries are filled with
255). Start i at
128 and fill all 'last'
* table entries <= 'max'
*/
last =
0;
for (i =
0; i <
255; ++i) /*
8-bit output value */
{
/* Find the corresponding maximum input value */
png_uint_16 out = (png_uint_16)(i *
257U); /*
16-bit output value */
/* Find the boundary value in
16 bits: */
png_uint_32 bound = png_gamma_16bit_correct(out+
128U, gamma_val);
/* Adjust (round) to (
16-shift) bits: */
bound = (bound * max +
32768U)/
65535U +
1U;
while (last < bound)
{
table[last & (
0xffU >> shift)][last >> (
8U - shift)] = out;
last++;
}
}
/* And fill in the final entries. */
while (last < (num <<
8))
{
table[last & (
0xff >> shift)][last >> (
8U - shift)] =
65535U;
last++;
}
}
#endif /*
16BIT */
/* Build a single
8-bit table: same as the
16-bit case but much simpler (and
* typically much faster). Note that libpng currently does no sBIT processing
* (apparently contrary to the spec) so a
256-entry table is always generated.
*/
static void
png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
png_fixed_point gamma_val)
{
unsigned int i;
png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr,
256);
if (png_gamma_significant(gamma_val) !=
0)
for (i=
0; i<
256; i++)
table[i] = png_gamma_8bit_correct(i, gamma_val);
else
for (i=
0; i<
256; ++i)
table[i] = (png_byte)(i &
0xff);
}
/* Used from png_read_destroy and below to release the memory used by the gamma
* tables.
*/
void /* PRIVATE */
png_destroy_gamma_table(png_structrp png_ptr)
{
png_free(png_ptr, png_ptr->gamma_table);
png_ptr->gamma_table = NULL;
#ifdef PNG_16BIT_SUPPORTED
if (png_ptr->gamma_16_table != NULL)
{
int i;
int istop = (
1 << (
8 - png_ptr->gamma_shift));
for (i =
0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_table[i]);
}
png_free(png_ptr, png_ptr->gamma_16_table);
png_ptr->gamma_16_table = NULL;
}
#endif /*
16BIT */
#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
png_free(png_ptr, png_ptr->gamma_from_1);
png_ptr->gamma_from_1 = NULL;
png_free(png_ptr, png_ptr->gamma_to_1);
png_ptr->gamma_to_1 = NULL;
#ifdef PNG_16BIT_SUPPORTED
if (png_ptr->gamma_16_from_1 != NULL)
{
int i;
int istop = (
1 << (
8 - png_ptr->gamma_shift));
for (i =
0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_from_1[i]);
}
png_free(png_ptr, png_ptr->gamma_16_from_1);
png_ptr->gamma_16_from_1 = NULL;
}
if (png_ptr->gamma_16_to_1 != NULL)
{
int i;
int istop = (
1 << (
8 - png_ptr->gamma_shift));
for (i =
0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_to_1[i]);
}
png_free(png_ptr, png_ptr->gamma_16_to_1);
png_ptr->gamma_16_to_1 = NULL;
}
#endif /*
16BIT */
#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
}
/* We build the
8- or
16-bit gamma tables here. Note that for
16-bit
* tables, we don't make a full table if we are reducing to
8-bit in
* the future. Note also how the gamma_16 tables are segmented so that
* we don't need to allocate >
64K chunks for a full
16-bit table.
*
* TODO: move this to pngrtran.c and make it static. Better yet create
* pngcolor.c and put all the PNG_COLORSPACE stuff in there.
*/
#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
# define GAMMA_TRANSFORMS
1 /* #ifdef CSE */
#else
# define GAMMA_TRANSFORMS
0
#endif
void /* PRIVATE */
png_build_gamma_table(png_structrp png_ptr, int bit_depth)
{
png_fixed_point file_gamma, screen_gamma;
png_fixed_point correction;
# if GAMMA_TRANSFORMS
png_fixed_point file_to_linear, linear_to_screen;
# endif
png_debug(
1, "in png_build_gamma_table");
/* Remove any existing table; this copes with multiple calls to
* png_read_update_info. The warning is because building the gamma tables
* multiple times is a performance hit - it's harmless but the ability to
* call png_read_update_info() multiple times is new in
1.
5.
6 so it seems
* sensible to warn if the app introduces such a hit.
*/
if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)
{
png_warning(png_ptr, "gamma table being rebuilt");
png_destroy_gamma_table(png_ptr);
}
/* The following fields are set, finally, in png_init_read_transformations.
* If file_gamma is
0 (unset) nothing can be done otherwise if screen_gamma
* is
0 (unset) there is no gamma correction but to/from linear is possible.
*/
file_gamma = png_ptr->file_gamma;
screen_gamma = png_ptr->screen_gamma;
# if GAMMA_TRANSFORMS
file_to_linear = png_reciprocal(file_gamma);
# endif
if (screen_gamma >
0)
{
# if GAMMA_TRANSFORMS
linear_to_screen = png_reciprocal(screen_gamma);
# endif
correction = png_reciprocal2(screen_gamma, file_gamma);
}
else /* screen gamma unknown */
{
# if GAMMA_TRANSFORMS
linear_to_screen = file_gamma;
# endif
correction = PNG_FP_1;
}
if (bit_depth <=
8)
{
png_build_8bit_table(png_ptr, &png_ptr->gamma_table, correction);
#if GAMMA_TRANSFORMS
if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) !=
0)
{
png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1, file_to_linear);
png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1,
linear_to_screen);
}
#endif /* GAMMA_TRANSFORMS */
}
#ifdef PNG_16BIT_SUPPORTED
else
{
png_byte shift, sig_bit;
if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) !=
0)
{
sig_bit = png_ptr->sig_bit.red;
if (png_ptr->sig_bit.green > sig_bit)
sig_bit = png_ptr->sig_bit.green;
if (png_ptr->sig_bit.blue > sig_bit)
sig_bit = png_ptr->sig_bit.blue;
}
else
sig_bit = png_ptr->sig_bit.gray;
/*
16-bit gamma code uses this equation:
*
* ov = table[(iv &
0xff) >> gamma_shift][iv >>
8]
*
* Where 'iv' is the input color value and 'ov' is the output value -
* pow(iv, gamma).
*
* Thus the gamma table consists of up to
256 256-entry tables. The table
* is selected by the (
8-gamma_shift) most significant of the low
8 bits
* of the color value then indexed by the upper
8 bits:
*
* table[low bits][high
8 bits]
*
* So the table 'n' corresponds to all those 'iv' of:
*
* <all high
8-bit values><n << gamma_shift>..<(n+
1 << gamma_shift)-
1>
*
*/
if (sig_bit >
0 && sig_bit <
16U)
/* shift == insignificant bits */
shift = (png_byte)((
16U - sig_bit) &
0xff);
else
shift =
0; /* keep all
16 bits */
if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) !=
0)
{
/* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively
* the significant bits in the *input* when the output will
* eventually be
8 bits. By default it is
11.
*/
if (shift < (
16U - PNG_MAX_GAMMA_8))
shift = (
16U - PNG_MAX_GAMMA_8);
}
if (shift >
8U)
shift =
8U; /* Guarantees at least one table! */
png_ptr->gamma_shift = shift;
/* NOTE: prior to
1.
5.
4 this test used to include PNG_BACKGROUND (now
* PNG_COMPOSE). This effectively smashed the background calculation for
*
16-bit output because the
8-bit table assumes the result will be
* reduced to
8 bits.
*/
if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) !=
0)
png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
png_reciprocal(correction));
else
png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift,
correction);
# if GAMMA_TRANSFORMS
if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) !=
0)
{
png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift,
file_to_linear);
/* Notice that the '
16 from
1' table should be full precision, however
* the lookup on this table still uses gamma_shift, so it can't be.
* TODO: fix this.
*/
png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,
linear_to_screen);
}
#endif /* GAMMA_TRANSFORMS */
}
#endif /*
16BIT */
}
#endif /* READ_GAMMA */
/* HARDWARE OR SOFTWARE OPTION SUPPORT */
#ifdef PNG_SET_OPTION_SUPPORTED
int PNGAPI
png_set_option(png_structrp png_ptr, int option, int onoff)
{
if (png_ptr != NULL && option >=
0 && option < PNG_OPTION_NEXT &&
(option &
1) ==
0)
{
png_uint_32 mask =
3U << option;
png_uint_32 setting = (
2U + (onoff !=
0)) << option;
png_uint_32 current = png_ptr->options;
png_ptr->options = (png_uint_32)((current & ~mask) | setting);
return (int)(current & mask) >> option;
}
return PNG_OPTION_INVALID;
}
#endif
/* sRGB support */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
/* sRGB conversion tables; these are machine generated with the code in
* contrib/tools/makesRGB.c. The actual sRGB transfer curve defined in the
* specification (see the article at
https://en.wikipedia.org/wiki/SRGB)
* is used, not the gamma=
1/
2.
2 approximation use elsewhere in libpng.
* The sRGB to linear table is exact (to the nearest
16-bit linear fraction).
* The inverse (linear to sRGB) table has accuracies as follows:
*
* For all possible (
255*
65535+
1) input values:
*
* error: -
0.
515566 -
0.
625971,
79441 (
0.
475369%) of readings inexact
*
* For the input values corresponding to the
65536 16-bit values:
*
* error: -
0.
513727 -
0.
607759,
308 (
0.
469978%) of readings inexact
*
* In all cases the inexact readings are only off by one.
*/
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
/* The convert-to-sRGB table is only currently required for read. */
const png_uint_16 png_sRGB_table[
256] =
{
0,
20,
40,
60,
80,
99,
119,
139,
159,
179,
199,
219,
241,
264,
288,
313,
340,
367,
396,
427,
458,
491,
526,
562,
599,
637,
677,
718,
761,
805,
851,
898,
947,
997,
1048,
1101,
1156,
1212,
1270,
1330,
1391,
1453,
1517,
1583,
1651,
1720,
1790,
1863,
1937,
2013,
2090,
2170,
2250,
2333,
2418,
2504,
2592,
2681,
2773,
2866,
2961,
3058,
3157,
3258,
3360,
3464,
3570,
3678,
3788,
3900,
4014,
4129,
4247,
4366,
4488,
4611,
4736,
4864,
4993,
5124,
5257,
5392,
5530,
5669,
5810,
5953,
6099,
6246,
6395,
6547,
6700,
6856,
7014,
7174,
7335,
7500,
7666,
7834,
8004,
8177,
8352,
8528,
8708,
8889,
9072,
9258,
9445,
9635,
9828,
10022,
10219,
10417,
10619,
10822,
11028,
11235,
11446,
11658,
11873,
12090,
12309,
12530,
12754,
12980,
13209,
13440,
13673,
13909,
14146,
14387,
14629,
14874,
15122,
15371,
15623,
15878,
16135,
16394,
16656,
16920,
17187,
17456,
17727,
18001,
18277,
18556,
18837,
19121,
19407,
19696,
19987,
20281,
20577,
20876,
21177,
21481,
21787,
22096,
22407,
22721,
23038,
23357,
23678,
24002,
24329,
24658,
24990,
25325,
25662,
26001,
26344,
26688,
27036,
27386,
27739,
28094,
28452,
28813,
29176,
29542,
29911,
30282,
30656,
31033,
31412,
31794,
32179,
32567,
32957,
33350,
33745,
34143,
34544,
34948,
35355,
35764,
36176,
36591,
37008,
37429,
37852,
38278,
38706,
39138,
39572,
40009,
40449,
40891,
41337,
41785,
42236,
42690,
43147,
43606,
44069,
44534,
45002,
45473,
45947,
46423,
46903,
47385,
47871,
48359,
48850,
49344,
49841,
50341,
50844,
51349,
51858,
52369,
52884,
53401,
53921,
54445,
54971,
55500,
56032,
56567,
57105,
57646,
58190,
58737,
59287,
59840,
60396,
60955,
61517,
62082,
62650,
63221,
63795,
64372,
64952,
65535
};
#endif /* SIMPLIFIED_READ */
/* The base/delta tables are required for both read and write (but currently
* only the simplified versions.)
*/
const png_uint_16 png_sRGB_base[
512] =
{
128,
1782,
3383,
4644,
5675,
6564,
7357,
8074,
8732,
9346,
9921,
10463,
10977,
11466,
11935,
12384,
12816,
13233,
13634,
14024,
14402,
14769,
15125,
15473,
15812,
16142,
16466,
16781,
17090,
17393,
17690,
17981,
18266,
18546,
18822,
19093,
19359,
19621,
19879,
20133,
20383,
20630,
20873,
21113,
21349,
21583,
21813,
22041,
22265,
22487,
22707,
22923,
23138,
23350,
23559,
23767,
23972,
24175,
24376,
24575,
24772,
24967,
25160,
25352,
25542,
25730,
25916,
26101,
26284,
26465,
26645,
26823,
27000,
27176,
27350,
27523,
27695,
27865,
28034,
28201,
28368,
28533,
28697,
28860,
29021,
29182,
29341,
29500,
29657,
29813,
29969,
30123,
30276,
30429,
30580,
30730,
30880,
31028,
31176,
31323,
31469,
31614,
31758,
31902,
32045,
32186,
32327,
32468,
32607,
32746,
32884,
33021,
33158,
33294,
33429,
33564,
33697,
33831,
33963,
34095,
34226,
34357,
34486,
34616,
34744,
34873,
35000,
35127,
35253,
35379,
35504,
35629,
35753,
35876,
35999,
36122,
36244,
36365,
36486,
36606,
36726,
36845,
36964,
37083,
37201,
37318,
37435,
37551,
37668,
37783,
37898,
38013,
38127,
38241,
38354,
38467,
38580,
38692,
38803,
38915,
39026,
39136,
39246,
39356,
39465,
39574,
39682,
39790,
39898,
40005,
40112,
40219,
40325,
40431,
40537,
40642,
40747,
40851,
40955,
41059,
41163,
41266,
41369,
41471,
41573,
41675,
41777,
41878,
41979,
42079,
42179,
42279,
42379,
42478,
42577,
42676,
42775,
42873,
42971,
43068,
43165,
43262,
43359,
43456,
43552,
43648,
43743,
43839,
43934,
44028,
44123,
44217,
44311,
44405,
44499,
44592,
44685,
44778,
44870,
44962,
45054,
45146,
45238,
45329,
45420,
45511,
45601,
45692,
45782,
45872,
45961,
46051,
46140,
46229,
46318,
46406,
46494,
46583,
46670,
46758,
46846,
46933,
47020,
47107,
47193,
47280,
47366,
47452,
47538,
47623,
47709,
47794,
47879,
47964,
48048,
48133,
48217,
48301,
48385,
48468,
48552,
48635,
48718,
48801,
48884,
48966,
49048,
49131,
49213,
49294,
49376,
49458,
49539,
49620,
49701,
49782,
49862,
49943,
50023,
50103,
50183,
50263,
50342,
50422,
50501,
50580,
50659,
50738,
50816,
50895,
50973,
51051,
51129,
51207,
51285,
51362,
51439,
51517,
51594,
51671,
51747,
51824,
51900,
51977,
52053,
52129,
52205,
52280,
52356,
52432,
52507,
52582,
52657,
52732,
52807,
52881,
52956,
53030,
53104,
53178,
53252,
53326,
53400,
53473,
53546,
53620,
53693,
53766,
53839,
53911,
53984,
54056,
54129,
54201,
54273,
54345,
54417,
54489,
54560,
54632,
54703,
54774,
54845,
54916,
54987,
55058,
55129,
55199,
55269,
55340,
55410,
55480,
55550,
55620,
55689,
55759,
55828,
55898,
55967,
56036,
56105,
56174,
56243,
56311,
56380,
56448,
56517,
56585,
56653,
56721,
56789,
56857,
56924,
56992,
57059,
57127,
57194,
57261,
57328,
57395,
57462,
57529,
57595,
57662,
57728,
57795,
57861,
57927,
57993,
58059,
58125,
58191,
58256,
58322,
58387,
58453,
58518,
58583,
58648,
58713,
58778,
58843,
58908,
58972,
59037,
59101,
59165,
59230,
59294,
59358,
59422,
59486,
59549,
59613,
59677,
59740,
59804,
59867,
59930,
59993,
60056,
60119,
60182,
60245,
60308,
60370,
60433,
60495,
60558,
60620,
60682,
60744,
60806,
60868,
60930,
60992,
61054,
61115,
61177,
61238,
61300,
61361,
61422,
61483,
61544,
61605,
61666,
61727,
61788,
61848,
61909,
61969,
62030,
62090,
62150,
62211,
62271,
62331,
62391,
62450,
62510,
62570,
62630,
62689,
62749,
62808,
62867,
62927,
62986,
63045,
63104,
63163,
63222,
63281,
63340,
63398,
63457,
63515,
63574,
63632,
63691,
63749,
63807,
63865,
63923,
63981,
64039,
64097,
64155,
64212,
64270,
64328,
64385,
64443,
64500,
64557,
64614,
64672,
64729,
64786,
64843,
64900,
64956,
65013,
65070,
65126,
65183,
65239,
65296,
65352,
65409,
65465
};
const png_byte png_sRGB_delta[
512] =
{
207,
201,
158,
129,
113,
100,
90,
82,
77,
72,
68,
64,
61,
59,
56,
54,
52,
50,
49,
47,
46,
45,
43,
42,
41,
40,
39,
39,
38,
37,
36,
36,
35,
34,
34,
33,
33,
32,
32,
31,
31,
30,
30,
30,
29,
29,
28,
28,
28,
27,
27,
27,
27,
26,
26,
26,
25,
25,
25,
25,
24,
24,
24,
24,
23,
23,
23,
23,
23,
22,
22,
22,
22,
22,
22,
21,
21,
21,
21,
21,
21,
20,
20,
20,
20,
20,
20,
20,
20,
19,
19,
19,
19,
19,
19,
19,
19,
18,
18,
18,
18,
18,
18,
18,
18,
18,
18,
17,
17,
17,
17,
17,
17,
17,
17,
17,
17,
17,
16,
16,
16,
16,
16,
16,
16,
16,
16,
16,
16,
16,
16,
16,
15,
15,
15,
15,
15,
15,
15,
15,
15,
15,
15,
15,
15,
15,
15,
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12,
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11,
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7,
7,
7,
7,
7,
7,
7,
7,
7,
7,
7,
7
};
#endif /* SIMPLIFIED READ/WRITE sRGB support */
/* SIMPLIFIED READ/WRITE SUPPORT */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
static int
png_image_free_function(png_voidp argument)
{
png_imagep image = png_voidcast(png_imagep, argument);
png_controlp cp = image->opaque;
png_control c;
/* Double check that we have a png_ptr - it should be impossible to get here
* without one.
*/
if (cp->png_ptr == NULL)
return
0;
/* First free any data held in the control structure. */
# ifdef PNG_STDIO_SUPPORTED
if (cp->owned_file !=
0)
{
FILE *fp = png_voidcast(FILE *, cp->png_ptr->io_ptr);
cp->owned_file =
0;
/* Ignore errors here. */
if (fp != NULL)
{
cp->png_ptr->io_ptr = NULL;
(void)fclose(fp);
}
}
# endif
/* Copy the control structure so that the original, allocated, version can be
* safely freed. Notice that a png_error here stops the remainder of the
* cleanup, but this is probably fine because that would indicate bad memory
* problems anyway.
*/
c = *cp;
image->opaque = &c;
png_free(c.png_ptr, cp);
/* Then the structures, calling the correct API. */
if (c.for_write !=
0)
{
# ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
png_destroy_write_struct(&c.png_ptr, &c.info_ptr);
# else
png_error(c.png_ptr, "simplified write not supported");
# endif
}
else
{
# ifdef PNG_SIMPLIFIED_READ_SUPPORTED
png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL);
# else
png_error(c.png_ptr, "simplified read not supported");
# endif
}
/* Success. */
return
1;
}
void PNGAPI
png_image_free(png_imagep image)
{
/* Safely call the real function, but only if doing so is safe at this point
* (if not inside an error handling context). Otherwise assume
* png_safe_execute will call this API after the return.
*/
if (image != NULL && image->opaque != NULL &&
image->opaque->error_buf == NULL)
{
png_image_free_function(image);
image->opaque = NULL;
}
}
int /* PRIVATE */
png_image_error(png_imagep image, png_const_charp error_message)
{
/* Utility to log an error. */
png_safecat(image->message, (sizeof image->message),
0, error_message);
image->warning_or_error |= PNG_IMAGE_ERROR;
png_image_free(image);
return
0;
}
#endif /* SIMPLIFIED READ/WRITE */
#endif /* READ || WRITE */
