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png.c
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png.c
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/* png.c - location for general purpose libpng functions
*
* Last changed in libpng 1.5.11 [June 14, 2012]
* Copyright (c) 1998-2012 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 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_5_11 Your_png_h_is_not_version_1_5_11;
/* 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_structp png_ptr, int num_bytes)
{
png_debug(1, "in png_set_sig_bytes");
if (png_ptr == NULL)
return;
if (num_bytes > 8)
png_error(png_ptr, "Too many bytes for PNG signature");
png_ptr->sig_bytes = (png_byte)(num_bytes < 0 ? 0 : num_bytes);
}
/* 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, png_size_t start, png_size_t num_to_check)
{
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 ((int)(png_memcmp(&sig[start], &png_signature[start], num_to_check)));
}
#endif /* PNG_READ_SUPPORTED */
#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_voidp ptr;
png_structp p=(png_structp)png_ptr;
png_uint_32 save_flags=p->flags;
png_alloc_size_t num_bytes;
if (png_ptr == NULL)
return (NULL);
if (items > PNG_UINT_32_MAX/size)
{
png_warning (p, "Potential overflow in png_zalloc()");
return (NULL);
}
num_bytes = (png_alloc_size_t)items * size;
p->flags|=PNG_FLAG_MALLOC_NULL_MEM_OK;
ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
p->flags=save_flags;
return ((voidpf)ptr);
}
/* Function to free memory for zlib */
void /* PRIVATE */
png_zfree(voidpf png_ptr, voidpf ptr)
{
png_free((png_structp)png_ptr, (png_voidp)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_structp 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_structp png_ptr, png_const_bytep ptr, png_size_t length)
{
int need_crc = 1;
if (PNG_CHUNK_ANCILLIARY(png_ptr->chunk_name))
{
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)
need_crc = 0;
}
/* 'uLong' is defined 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 && length > 0)
{
uLong crc = png_ptr->crc; /* Should never issue a warning */
do
{
uInt safeLength = (uInt)length;
if (safeLength == 0)
safeLength = (uInt)-1; /* evil, but safe */
crc = crc32(crc, ptr, safeLength);
/* 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 += safeLength;
length -= safeLength;
}
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_structp png_ptr, png_const_charp user_png_ver)
{
if (user_png_ver)
{
int i = 0;
do
{
if (user_png_ver[i] != png_libpng_ver[i])
png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
} while (png_libpng_ver[i++]);
}
else
png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)
{
/* Libpng 0.90 and later are binary incompatible with libpng 0.89, so
* we must recompile any applications that use any older library version.
* For versions after libpng 1.0, we will be compatible, so we need
* only check the first digit.
*/
if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0] ||
(user_png_ver[0] == '1' && user_png_ver[2] != png_libpng_ver[2]) ||
(user_png_ver[0] == '0' && user_png_ver[2] < '9'))
{
#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);
png_warning(png_ptr, m);
#endif
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
png_ptr->flags = 0;
#endif
return 0;
}
}
/* Success return. */
return 1;
}
/* Allocate the memory for an info_struct for the application. We don't
* really need the png_ptr, but it could potentially be useful in the
* future. This should be used in favour of malloc(png_sizeof(png_info))
* and png_info_init() so that applications that want to use a shared
* libpng don't have to be recompiled if png_info changes size.
*/
PNG_FUNCTION(png_infop,PNGAPI
png_create_info_struct,(png_structp png_ptr),PNG_ALLOCATED)
{
png_infop info_ptr;
png_debug(1, "in png_create_info_struct");
if (png_ptr == NULL)
return (NULL);
#ifdef PNG_USER_MEM_SUPPORTED
info_ptr = (png_infop)png_create_struct_2(PNG_STRUCT_INFO,
png_ptr->malloc_fn, png_ptr->mem_ptr);
#else
info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO);
#endif
if (info_ptr != NULL)
png_info_init_3(&info_ptr, png_sizeof(png_info));
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.
*/
void PNGAPI
png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
{
png_infop 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)
{
png_info_destroy(png_ptr, info_ptr);
#ifdef PNG_USER_MEM_SUPPORTED
png_destroy_struct_2((png_voidp)info_ptr, png_ptr->free_fn,
png_ptr->mem_ptr);
#else
png_destroy_struct((png_voidp)info_ptr);
#endif
*info_ptr_ptr = NULL;
}
}
/* 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.
*/
void PNGAPI
png_info_init_3(png_infopp ptr_ptr, png_size_t png_info_struct_size)
{
png_infop info_ptr = *ptr_ptr;
png_debug(1, "in png_info_init_3");
if (info_ptr == NULL)
return;
if (png_sizeof(png_info) > png_info_struct_size)
{
png_destroy_struct(info_ptr);
info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO);
*ptr_ptr = info_ptr;
}
/* Set everything to 0 */
png_memset(info_ptr, 0, png_sizeof(png_info));
}
void PNGAPI
png_data_freer(png_structp png_ptr, png_infop 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_warning(png_ptr,
"Unknown freer parameter in png_data_freer");
}
void PNGAPI
png_free_data(png_structp png_ptr, png_infop 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 ((mask & PNG_FREE_TEXT) & info_ptr->free_me)
{
if (num != -1)
{
if (info_ptr->text && info_ptr->text[num].key)
{
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_data(png_ptr, info_ptr, PNG_FREE_TEXT, i);
png_free(png_ptr, info_ptr->text);
info_ptr->text = NULL;
info_ptr->num_text=0;
}
}
#endif
#ifdef PNG_tRNS_SUPPORTED
/* Free any tRNS entry */
if ((mask & PNG_FREE_TRNS) & info_ptr->free_me)
{
png_free(png_ptr, info_ptr->trans_alpha);
info_ptr->trans_alpha = NULL;
info_ptr->valid &= ~PNG_INFO_tRNS;
}
#endif
#ifdef PNG_sCAL_SUPPORTED
/* Free any sCAL entry */
if ((mask & PNG_FREE_SCAL) & info_ptr->free_me)
{
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)
{
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 < (int)info_ptr->pcal_nparams; i++)
{
png_free(png_ptr, info_ptr->pcal_params[i]);
info_ptr->pcal_params[i] = NULL;
}
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 iCCP entry */
if ((mask & PNG_FREE_ICCP) & info_ptr->free_me)
{
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 ((mask & PNG_FREE_SPLT) & info_ptr->free_me)
{
if (num != -1)
{
if (info_ptr->splt_palettes)
{
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
{
if (info_ptr->splt_palettes_num)
{
int i;
for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, i);
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_UNKNOWN_CHUNKS_SUPPORTED
if (png_ptr->unknown_chunk.data)
{
png_free(png_ptr, png_ptr->unknown_chunk.data);
png_ptr->unknown_chunk.data = NULL;
}
if ((mask & PNG_FREE_UNKN) & info_ptr->free_me)
{
if (num != -1)
{
if (info_ptr->unknown_chunks)
{
png_free(png_ptr, info_ptr->unknown_chunks[num].data);
info_ptr->unknown_chunks[num].data = NULL;
}
}
else
{
int i;
if (info_ptr->unknown_chunks_num)
{
for (i = 0; i < info_ptr->unknown_chunks_num; i++)
png_free_data(png_ptr, info_ptr, PNG_FREE_UNKN, i);
png_free(png_ptr, info_ptr->unknown_chunks);
info_ptr->unknown_chunks = NULL;
info_ptr->unknown_chunks_num = 0;
}
}
}
#endif
#ifdef PNG_hIST_SUPPORTED
/* Free any hIST entry */
if ((mask & PNG_FREE_HIST) & info_ptr->free_me)
{
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)
{
png_zfree(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)
{
if (info_ptr->row_pointers)
{
int row;
for (row = 0; row < (int)info_ptr->height; row++)
{
png_free(png_ptr, info_ptr->row_pointers[row]);
info_ptr->row_pointers[row] = NULL;
}
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;
}
/* This is an internal routine to free any memory that the info struct is
* pointing to before re-using it or freeing the struct itself. Recall
* that png_free() checks for NULL pointers for us.
*/
void /* PRIVATE */
png_info_destroy(png_structp png_ptr, png_infop info_ptr)
{
png_debug(1, "in png_info_destroy");
png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
if (png_ptr->num_chunk_list)
{
png_free(png_ptr, png_ptr->chunk_list);
png_ptr->chunk_list = NULL;
png_ptr->num_chunk_list = 0;
}
#endif
png_info_init_3(&info_ptr, png_sizeof(png_info));
}
#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
/* 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_structp 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_structp png_ptr, png_FILE_p fp)
{
png_debug(1, "in png_init_io");
if (png_ptr == NULL)
return;
png_ptr->io_ptr = (png_voidp)fp;
}
# 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.
*/
png_const_charp PNGAPI
png_convert_to_rfc1123(png_structp png_ptr, png_const_timep ptime)
{
static PNG_CONST char short_months[12][4] =
{"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
if (png_ptr == NULL)
return (NULL);
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)
{
png_warning(png_ptr, "Ignoring invalid time value");
return (NULL);
}
{
size_t pos = 0;
char number_buf[5]; /* enough for a four-digit year */
# define APPEND_STRING(string)\
pos = png_safecat(png_ptr->time_buffer, sizeof png_ptr->time_buffer,\
pos, (string))
# define APPEND_NUMBER(format, value)\
APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
# define APPEND(ch)\
if (pos < (sizeof png_ptr->time_buffer)-1)\
png_ptr->time_buffer[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 */
# undef APPEND
# undef APPEND_NUMBER
# undef APPEND_STRING
}
return png_ptr->time_buffer;
}
# endif /* PNG_TIME_RFC1123_SUPPORTED */
#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
png_const_charp PNGAPI
png_get_copyright(png_const_structp png_ptr)
{
PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
#ifdef PNG_STRING_COPYRIGHT
return PNG_STRING_COPYRIGHT
#else
# ifdef __STDC__
return PNG_STRING_NEWLINE \
"libpng version 1.5.11 - June 14, 2012" PNG_STRING_NEWLINE \
"Copyright (c) 1998-2012 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;
# else
return "libpng version 1.5.11 - June 14, 2012\
Copyright (c) 1998-2012 Glenn Randers-Pehrson\
Copyright (c) 1996-1997 Andreas Dilger\
Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
# endif
#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_structp 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_structp 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_structp 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_HANDLE_AS_UNKNOWN_SUPPORTED
int PNGAPI
png_handle_as_unknown(png_structp 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, so it should continue
* to do so in case there are duplicated entries.
*/
do /* num_chunk_list > 0, so at least one */
{
p -= 5;
if (!png_memcmp(chunk_name, p, 4))
return p[4];
}
while (p > p_end);
return PNG_HANDLE_CHUNK_AS_DEFAULT;
}
int /* PRIVATE */
png_chunk_unknown_handling(png_structp 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
#ifdef PNG_READ_SUPPORTED
/* This function, added to libpng-1.0.6g, is untested. */
int PNGAPI
png_reset_zstream(png_structp png_ptr)
{
if (png_ptr == NULL)
return Z_STREAM_ERROR;
return (inflateReset(&png_ptr->zstream));
}
#endif /* PNG_READ_SUPPORTED */
/* 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)
/* png_convert_size: a PNGAPI but no longer in png.h, so deleted
* at libpng 1.5.5!
*/
/* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */
# ifdef PNG_CHECK_cHRM_SUPPORTED
int /* PRIVATE */
png_check_cHRM_fixed(png_structp png_ptr,
png_fixed_point white_x, png_fixed_point white_y, png_fixed_point red_x,
png_fixed_point red_y, png_fixed_point green_x, png_fixed_point green_y,
png_fixed_point blue_x, png_fixed_point blue_y)
{
int ret = 1;
unsigned long xy_hi,xy_lo,yx_hi,yx_lo;
png_debug(1, "in function png_check_cHRM_fixed");
if (png_ptr == NULL)
return 0;
/* (x,y,z) values are first limited to 0..100000 (PNG_FP_1), the white
* y must also be greater than 0. To test for the upper limit calculate
* (PNG_FP_1-y) - x must be <= to this for z to be >= 0 (and the expression
* cannot overflow.) At this point we know x and y are >= 0 and (x+y) is
* <= PNG_FP_1. The previous test on PNG_MAX_UINT_31 is removed because it
* pointless (and it produces compiler warnings!)
*/
if (white_x < 0 || white_y <= 0 ||
red_x < 0 || red_y < 0 ||
green_x < 0 || green_y < 0 ||
blue_x < 0 || blue_y < 0)
{
png_warning(png_ptr,
"Ignoring attempt to set negative chromaticity value");
ret = 0;
}
/* And (x+y) must be <= PNG_FP_1 (so z is >= 0) */
if (white_x > PNG_FP_1 - white_y)
{
png_warning(png_ptr, "Invalid cHRM white point");
ret = 0;
}
if (red_x > PNG_FP_1 - red_y)
{
png_warning(png_ptr, "Invalid cHRM red point");
ret = 0;
}
if (green_x > PNG_FP_1 - green_y)
{
png_warning(png_ptr, "Invalid cHRM green point");
ret = 0;
}
if (blue_x > PNG_FP_1 - blue_y)
{
png_warning(png_ptr, "Invalid cHRM blue point");
ret = 0;
}
png_64bit_product(green_x - red_x, blue_y - red_y, &xy_hi, &xy_lo);
png_64bit_product(green_y - red_y, blue_x - red_x, &yx_hi, &yx_lo);
if (xy_hi == yx_hi && xy_lo == yx_lo)
{
png_warning(png_ptr,
"Ignoring attempt to set cHRM RGB triangle with zero area");
ret = 0;
}
return ret;
}
# endif /* PNG_CHECK_cHRM_SUPPORTED */
#ifdef PNG_cHRM_SUPPORTED
/* 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 png_xy_from_XYZ(png_xy *xy, png_XYZ XYZ)
{
png_int_32 d, dwhite, whiteX, whiteY;
d = XYZ.redX + XYZ.redY + XYZ.redZ;
if (!png_muldiv(&xy->redx, XYZ.redX, PNG_FP_1, d)) return 1;
if (!png_muldiv(&xy->redy, XYZ.redY, PNG_FP_1, d)) return 1;
dwhite = d;
whiteX = XYZ.redX;
whiteY = XYZ.redY;
d = XYZ.greenX + XYZ.greenY + XYZ.greenZ;
if (!png_muldiv(&xy->greenx, XYZ.greenX, PNG_FP_1, d)) return 1;
if (!png_muldiv(&xy->greeny, XYZ.greenY, PNG_FP_1, d)) return 1;
dwhite += d;
whiteX += XYZ.greenX;
whiteY += XYZ.greenY;
d = XYZ.blueX + XYZ.blueY + XYZ.blueZ;
if (!png_muldiv(&xy->bluex, XYZ.blueX, PNG_FP_1, d)) return 1;
if (!png_muldiv(&xy->bluey, XYZ.blueY, PNG_FP_1, d)) return 1;
dwhite += d;
whiteX += XYZ.blueX;
whiteY += XYZ.blueY;
/* The reference white is simply the same of the end-point (X,Y,Z) vectors,
* thus:
*/
if (!png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite)) return 1;
if (!png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite)) return 1;
return 0;
}
int png_XYZ_from_xy(png_XYZ *XYZ, png_xy xy)
{
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.)
*/
if (xy.redx < 0 || xy.redx > PNG_FP_1) return 1;
if (xy.redy < 0 || xy.redy > PNG_FP_1-xy.redx) return 1;
if (xy.greenx < 0 || xy.greenx > PNG_FP_1) return 1;
if (xy.greeny < 0 || xy.greeny > PNG_FP_1-xy.greenx) return 1;
if (xy.bluex < 0 || xy.bluex > PNG_FP_1) return 1;
if (xy.bluey < 0 || xy.bluey > PNG_FP_1-xy.bluex) return 1;
if (xy.whitex < 0 || xy.whitex > PNG_FP_1) return 1;
if (xy.whitey < 0 || xy.whitey > PNG_FP_1-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 invertion 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: