blob: 087a2787c9f4165ada05190d88d3fcefc2d9f320 [file] [log] [blame]
/* png.c - location for general purpose libpng functions
*
* Last changed in libpng 1.6.9 [February 6, 2014]
* Copyright (c) 1998-2014 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_6_10 Your_png_h_is_not_version_1_6_10;
/* 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)
{
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)(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_alloc_size_t num_bytes = size;
if (png_ptr == NULL)
return NULL;
if (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, png_size_t length)
{
int need_crc = 1;
if (PNG_CHUNK_ANCILLARY(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 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 && length > 0)
{
uLong crc = png_ptr->crc; /* Should never issue a warning */
do
{
uInt safe_length = (uInt)length;
if (safe_length == 0)
safe_length = (uInt)-1; /* evil, but safe */
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)
{
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 and third digits (note that when we reach version
* 1.10 we will need to check the fourth symbol, namely user_png_ver[3]).
*/
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[3] != png_libpng_ver[3])) ||
(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_UNUSED(pos)
png_warning(png_ptr, m);
#endif
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
png_ptr->flags = 0;
#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));
/* Added at libpng-1.2.6 */
# 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
/* Added at libpng-1.2.43 and 1.4.0 */
create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;
# endif
# ifdef PNG_USER_CHUNK_MALLOC_MAX
/* Added at libpng-1.2.43 and 1.4.1, required only for read but exists
* in png_struct regardless.
*/
create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_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))
{
/* 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;
# else
{
# endif
/* Call the general version checker (shared with read and write code):
*/
if (png_user_version_check(&create_struct, user_png_ver))
{
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, png_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)));
*ptr_ptr = info_ptr;
}
/* Set everything to 0 */
memset(info_ptr, 0, (sizeof *info_ptr));
}
/* The following API is not called internally */
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 ((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)
{
unsigned int i;
for (i = 0; i < 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 profile 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 < info_ptr->splt_palettes_num; i++)
png_free_data(png_ptr, info_ptr, PNG_FREE_SPLT, (int)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_STORE_UNKNOWN_CHUNKS_SUPPORTED
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, (int)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_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)
{
if (info_ptr->row_pointers)
{
png_uint_32 row;
for (row = 0; row < 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;
}
#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_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, 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_SAVE_INT_32_SUPPORTED
/* The png_save_int_32 function assumes integers are stored in two's
* complement format. If this isn't the case, then this routine needs to
* be modified to write data in two's complement format. Note that,
* the following works correctly even if png_int_32 has more than 32 bits
* (compare the more complex code required on read for sign extension.)
*/
void PNGAPI
png_save_int_32(png_bytep buf, png_int_32 i)
{
buf[0] = (png_byte)((i >> 24) & 0xff);
buf[1] = (png_byte)((i >> 16) & 0xff);
buf[2] = (png_byte)((i >> 8) & 0xff);
buf[3] = (png_byte)(i & 0xff);
}
#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 PNG_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]; /* 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 */
# 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))
png_warning(png_ptr, "Ignoring invalid time value");
else
return png_ptr->time_buffer;
}
return NULL;
}
# endif
# endif /* PNG_TIME_RFC1123_SUPPORTED */
#endif /* defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) */
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
# ifdef __STDC__
return PNG_STRING_NEWLINE \
"libpng version 1.6.10 - March 6, 2014" PNG_STRING_NEWLINE \
"Copyright (c) 1998-2014 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 1.6.10 - March 6, 2014\
Copyright (c) 1998-2014 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_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;
palette[i].green = (png_byte)v;
palette[i].blue = (png_byte)v;
}
}
#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 correcty.
*/
do /* num_chunk_list > 0, so at least one */
{
p -= 5;
if (!memcmp(chunk_name, p, 4))
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 /* 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)
/* 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;
}
}
/* 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_GAMMA_SUPPORTED /* always set if COLORSPACE */
static int
png_colorspace_check_gamma(png_const_structrp png_ptr,
png_colorspacerp colorspace, png_fixed_point gAMA, int from)
/* This is called to check a new gamma value against an existing one. The
* routine returns false if the new gamma value should not be written.
*
* 'from' says where the new gamma value comes from:
*
* 0: the new gamma value is the libpng estimate for an ICC profile
* 1: the new gamma value comes from a gAMA chunk
* 2: the new gamma value comes from an sRGB chunk
*/
{
png_fixed_point gtest;
if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 &&
(!png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) ||
png_gamma_significant(gtest)))
{
/* Either this is an sRGB image, in which case the calculated gamma
* approximation should match, or this is an image with a profile and the
* value libpng calculates for the gamma of the profile does not match the
* value recorded in the file. The former, sRGB, case is an error, the
* latter is just a warning.
*/
if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2)
{
png_chunk_report(png_ptr, "gamma value does not match sRGB",
PNG_CHUNK_ERROR);
/* Do not overwrite an sRGB value */
return from == 2;
}
else /* sRGB tag not involved */
{
png_chunk_report(png_ptr, "gamma value does not match libpng estimate",
PNG_CHUNK_WARNING);
return from == 1;
}
}
return 1;
}
void /* PRIVATE */
png_colorspace_set_gamma(png_const_structrp png_ptr,
png_colorspacerp colorspace, png_fixed_point gAMA)
{
/* Changed in libpng-1.5.4 to limit the values to ensure overflow can't
* occur. Since the fixed point representation is assymetrical it is
* possible for 1/gamma to overflow the limit of 21474 and this means the
* gamma value must be at least 5/100000 and hence at most 20000.0. For
* safety the limits here are a little narrower. The values are 0.00016 to
* 6250.0, which are truly ridiculous gamma values (and will produce
* displays that are all black or all white.)
*
* In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk
* handling code, which only required the value to be >0.
*/
png_const_charp errmsg;
if (gAMA < 16 || gAMA > 625000000)
errmsg = "gamma value out of range";
# ifdef PNG_READ_gAMA_SUPPORTED
/* Allow the application to set the gamma value more than once */
else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 &&
(colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0)
errmsg = "duplicate";
# endif
/* Do nothing if the colorspace is already invalid */
else if (colorspace->flags & PNG_COLORSPACE_INVALID)
return;
else
{
if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA, 1/*from gAMA*/))
{
/* Store this gamma value. */
colorspace->gamma = gAMA;
colorspace->flags |=
(PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA);
}
/* At present if the check_gamma test fails the gamma of the colorspace is
* not updated however the colorspace is not invalidated. This
* corresponds to the case where the existing gamma comes from an sRGB
* chunk or profile. An error message has already been output.
*/
return;
}
/* Error exit - errmsg has been set. */
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR);
}
void /* PRIVATE */
png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr)
{
if (info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID)
{
/* Everything is invalid */
info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB|
PNG_INFO_iCCP);
# ifdef PNG_COLORSPACE_SUPPORTED
/* Clean up the iCCP profile now if it won't be used. */
png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/);
# else
PNG_UNUSED(png_ptr)
# endif
}
else
{
# ifdef PNG_COLORSPACE_SUPPORTED
/* Leave the INFO_iCCP flag set if the pngset.c code has already set
* it; this allows a PNG to contain a profile which matches sRGB and
* yet still have that profile retrievable by the application.
*/
if (info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB)
info_ptr->valid |= PNG_INFO_sRGB;
else
info_ptr->valid &= ~PNG_INFO_sRGB;
if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS)
info_ptr->valid |= PNG_INFO_cHRM;
else
info_ptr->valid &= ~PNG_INFO_cHRM;
# endif
if (info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA)
info_ptr->valid |= PNG_INFO_gAMA;
else
info_ptr->valid &= ~PNG_INFO_gAMA;
}
}
#ifdef PNG_READ_SUPPORTED
void /* PRIVATE */
png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr)
{
if (info_ptr == NULL) /* reduce code size; check here not in the caller */
return;
info_ptr->colorspace = png_ptr->colorspace;
png_colorspace_sync_info(png_ptr, info_ptr);
}
#endif
#endif
#ifdef PNG_COLORSPACE_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.
*/
static int
png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)
{
png_int_32 d, dwhite, whiteX, whiteY;
d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z;
if (!png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d)) return 1;
if (!png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d)) return 1;
dwhite = d;
whiteX = XYZ->red_X;
whiteY = XYZ->red_Y;
d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z;
if (!png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d)) return 1;
if (!png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d)) return 1;
dwhite += d;
whiteX += XYZ->green_X;
whiteY += XYZ->green_Y;
d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z;
if (!png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d)) return 1;
if (!png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d)) return 1;
dwhite += d;
whiteX += XYZ->blue_X;
whiteY += XYZ->blue_Y;
/* The reference white is simply the sum 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;
}
static int
png_XYZ_from_xy(png_XYZ *XYZ, const 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:
*
* 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 tractible. 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. The values are 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.
*
* 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
* it is sufficient to divide the product by 7; ceil(100,000/32767*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
*/
/* By the argument, above overflow should be impossible here. The return
* value of 2 indicates an internal error to the caller.
*/
if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7))
return 2;
if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7))
return 2;
denominator = left - right;
/* Now find the red numerator. */
if (!png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7))
return 2;
if (!png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7))
return 2;
/* 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, left-right) ||
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, 7))
return 2;
if (!png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7))
return 2;
if (!png_muldiv(&green_inverse, xy->whitey, denominator, left-right) ||
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_reciprocal(xy->whitey) - png_reciprocal(red_inverse) -
png_reciprocal(green_inverse);
if (blue_scale <= 0) return 1;
/* And fill in the png_XYZ: */
if (!png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse)) return 1;
if (!png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse)) return 1;
if (!png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
red_inverse))
return 1;
if (!png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse))
return 1;
if (!png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse))
return 1;
if (!png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
green_inverse))
return 1;
if (!png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1)) return 1;
if (!png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1)) return 1;
if (!png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
PNG_FP_1))
return 1;
return 0; /*success*/
}
static int
png_XYZ_normalize(png_XYZ *XYZ)
{
png_int_32 Y;
if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 ||
XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 ||
XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0)
return 1;
/* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1.
* IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore
* relying on addition of two positive values producing a negative one is not
* safe.
*/
Y = XYZ->red_Y;
if (0x7fffffff - Y < XYZ->green_X) return 1;
Y += XYZ->green_Y;
if (0x7fffffff - Y < XYZ->blue_X) return 1;
Y += XYZ->blue_Y;
if (Y != PNG_FP_1)
{
if (!png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y)) return 1;
if (!png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y)) return 1;
}
return 0;
}
static int
png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta)
{
/* Allow an error of +/-0.01 (absolute value) on each chromaticity */
return !(PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) ||
PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) ||
PNG_OUT_OF_RANGE(xy1->redx, xy2->redx, delta) ||
PNG_OUT_OF_RANGE(xy1->redy, xy2->redy, delta) ||
PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) ||
PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) ||
PNG_OUT_OF_RANGE(xy1->bluex, xy2->bluex, delta) ||
PNG_OUT_OF_RANGE(xy1->bluey, xy2->bluey, delta));
}
/* Added in libpng-1.6.0, a different check for the validity of a set of cHRM
* chunk chromaticities. Earlier checks used to simply look for the overflow
* condition (where the determinant of the matrix to solve for XYZ ends up zero
* because the chromaticity values are not all distinct.) Despite this it is
* theoretically possible to produce chromaticities that are apparently valid
* but that rapidly degrade to invalid, potentially crashing, sets because of
* arithmetic inaccuracies when calculations are performed on them. The new
* check is to round-trip xy -> XYZ -> xy and then check that the result is
* within a small percentage of the original.
*/
static int
png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy)
{
int result;
png_xy xy_test;
/* As a side-effect this routine also returns the XYZ endpoints. */
result = png_XYZ_from_xy(XYZ, xy);
if (result) return result;
result = png_xy_from_XYZ(&xy_test, XYZ);
if (result) return result;
if (png_colorspace_endpoints_match(xy, &xy_test,
5/*actually, the math is pretty accurate*/))
return 0;
/* Too much slip */
return 1;
}
/* This is the check going the other way. The XYZ is modified to normalize it
* (another side-effect) and the xy chromaticities are returned.
*/
static int
png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ)
{
int result;
png_XYZ XYZtemp;
result = png_XYZ_normalize(XYZ);
if (result) return result;
result = png_xy_from_XYZ(xy, XYZ);
if (result) return result;
XYZtemp = *XYZ;
return png_colorspace_check_xy(&XYZtemp, xy);
}
/* Used to check for an endpoint match against sRGB */
static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */
{
/* color x y */
/* red */ 64000, 33000,
/* green */ 30000, 60000,
/* blue */ 15000, 6000,
/* white */ 31270, 32900
};
static int
png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr,
png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ,
int preferred)
{
if (colorspace->flags & PNG_COLORSPACE_INVALID)
return 0;
/* The consistency check is performed on the chromaticities; this factors out
* variations because of the normalization (or not) of the end point Y
* values.
*/
if (preferred < 2 && (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS))
{
/* The end points must be reasonably close to any we already have. The
* following allows an error of up to +/-.001
*/
if (!png_colorspace_endpoints_match(xy, &colorspace->end_points_xy, 100))
{
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_benign_error(png_ptr, "inconsistent chromaticities");
return 0; /* failed */
}
/* Only overwrite with preferred values */
if (!preferred)
return 1; /* ok, but no change */
}
colorspace->end_points_xy = *xy;
colorspace->end_points_XYZ = *XYZ;
colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS;
/* The end points are normally quoted to two decimal digits, so allow +/-0.01
* on this test.
*/
if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000))
colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB;
else
colorspace->flags &= PNG_COLORSPACE_CANCEL(
PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);
return 2; /* ok and changed */
}
int /* PRIVATE */
png_colorspace_set_chromaticities(png_const_structrp png_ptr,
png_colorspacerp colorspace, const png_xy *xy, int preferred)
{
/* We must check the end points to ensure they are reasonable - in the past
* color management systems have crashed as a result of getting bogus
* colorant values, while this isn't the fault of libpng it is the
* responsibility of libpng because PNG carries the bomb and libpng is in a
* position to protect against it.
*/
png_XYZ XYZ;
switch (png_colorspace_check_xy(&XYZ, xy))
{
case 0: /* success */
return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ,
preferred);
case 1:
/* We can't invert the chromaticities so we can't produce value XYZ
* values. Likely as not a color management system will fail too.
*/
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_benign_error(png_ptr, "invalid chromaticities");
break;
default:
/* libpng is broken; this should be a warning but if it happens we
* want error reports so for the moment it is an error.
*/
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_error(png_ptr, "internal error checking chromaticities");
break;
}
return 0; /* failed */
}
int /* PRIVATE */
png_colorspace_set_endpoints(png_const_structrp png_ptr,
png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred)
{
png_XYZ XYZ = *XYZ_in;
png_xy xy;
switch (png_colorspace_check_XYZ(&xy, &XYZ))
{
case 0:
return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ,
preferred);
case 1:
/* End points are invalid. */
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_benign_error(png_ptr, "invalid end points");
break;
default:
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_error(png_ptr, "internal error checking chromaticities");
break;
}
return 0; /* failed */
}
#if defined(PNG_sRGB_SUPPORTED) || defined(PNG_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_colorspacerp colorspace,
png_const_charp name, png_alloc_size_t value, png_const_charp reason)
{
size_t pos;
char message[196]; /* see below for calculation */
if (colorspace != NULL)
colorspace->flags |= PNG_COLORSPACE_INVALID;
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))
{
/* 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)
/* This is recoverable, but make it unconditionally an app_error on write to
* avoid writing invalid ICC profiles into PNG files. (I.e. we handle them
* on read, with a warning, but on write unless the app turns off
* application errors the PNG won't be written.)
*/
png_chunk_report(png_ptr, message,
(colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR);
return 0;
}
#endif /* sRGB || iCCP */
#ifdef PNG_sRGB_SUPPORTED
int /* PRIVATE */
png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace,
int intent)
{
/* sRGB sets known gamma, end points and (from the chunk) intent. */
/* IMPORTANT: these are not necessarily the values found in an ICC profile
* because ICC profiles store values adapted to a D50 environment; it is
* expected that the ICC profile mediaWhitePointTag will be D50, see the
* checks and code elsewhere to understand this better.
*
* These XYZ values, which are accurate to 5dp, produce rgb to gray
* coefficients of (6968,23435,2366), which are reduced (because they add up
* to 32769 not 32768) to (6968,23434,2366). These are the values that
* libpng has traditionally used (and are the best values given the 15bit
* algorithm used by the rgb to gray code.)
*/
static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */
{
/* color X Y Z */
/* red */ 41239, 21264, 1933,
/* green */ 35758, 71517, 11919,
/* blue */ 18048, 7219, 95053
};
/* Do nothing if the colorspace is already invalidated. */
if (colorspace->flags & PNG_COLORSPACE_INVALID)
return 0;
/* Check the intent, then check for existing settings. It is valid for the
* PNG file to have cHRM or gAMA chunks along with sRGB, but the values must
* be consistent with the correct values. If, however, this function is
* called below because an iCCP chunk matches sRGB then it is quite
* conceivable that an older app recorded incorrect gAMA and cHRM because of
* an incorrect calculation based on the values in the profile - this does
* *not* invalidate the profile (though it still produces an error, which can
* be ignored.)
*/
if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST)
return png_icc_profile_error(png_ptr, colorspace, "sRGB",
(unsigned)intent, "invalid sRGB rendering intent");
if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 &&
colorspace->rendering_intent != intent)
return png_icc_profile_error(png_ptr, colorspace, "sRGB",
(unsigned)intent, "inconsistent rendering intents");
if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0)
{
png_benign_error(png_ptr, "duplicate sRGB information ignored");
return 0;
}
/* If the standard sRGB cHRM chunk does not match the one from the PNG file
* warn but overwrite the value with the correct one.
*/
if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 &&
!png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy,
100))
png_chunk_report(png_ptr, "cHRM chunk does not match sRGB",
PNG_CHUNK_ERROR);
/* This check is just done for the error reporting - the routine always
* returns true when the 'from' argument corresponds to sRGB (2).
*/
(void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE,
2/*from sRGB*/);
/* intent: bugs in GCC force 'int' to be used as the parameter type. */
colorspace->rendering_intent = (png_uint_16)intent;
colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT;
/* endpoints */
colorspace->end_points_xy = sRGB_xy;
colorspace->end_points_XYZ = sRGB_XYZ;
colorspace->flags |=
(PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB);
/* gamma */
colorspace->gamma = PNG_GAMMA_sRGB_INVERSE;
colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA;
/* Finally record that we have an sRGB profile */
colorspace->flags |=
(PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);
return 1; /* set */
}
#endif /* sRGB */
#ifdef PNG_iCCP_SUPPORTED
/* 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 };
int /* PRIVATE */
png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
png_const_charp name, png_uint_32 profile_length)
{
if (profile_length < 132)
return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
"too short");
if (profile_length & 3)
return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
"invalid length");
return 1;
}
int /* PRIVATE */
png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace,
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, colorspace, name, temp,
"length does not match profile");
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, colorspace, 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, colorspace, 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, NULL, 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 accomodate 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, colorspace, 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, NULL, 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 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))
return png_icc_profile_error(png_ptr, colorspace, name, temp,
"RGB color space not permitted on grayscale PNG");
break;
case 0x47524159: /* 'GRAY' */
if (color_type & PNG_COLOR_MASK_COLOR)
return png_icc_profile_error(png_ptr, colorspace, name, temp,
"Gray color space not permitted on RGB PNG");
break;
default:
return png_icc_profile_error(png_ptr, colorspace, 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, colorspace, name, temp,
"invalid embedded Abstract ICC profile");
case 0x6C696E6B: /* 'link' */
/* DeviceLink profiles cannnot 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, colorspace, 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 misintrepretation. Almost
* certainly it will fail the tests below.
*/
(void)png_icc_profile_error(png_ptr, NULL, 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, NULL, 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, colorspace, name, temp,
"unexpected ICC PCS encoding");
}
return 1;
}
int /* PRIVATE */
png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
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.
*/
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, NULL, name, tag_id,
"ICC profile tag start not a multiple of 4");
}
/* 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, colorspace, name, tag_id,
"ICC profile tag outside profile");
}
return 1; /* success, maybe with warnings */
}
#ifdef PNG_sRGB_SUPPORTED
/* Information about the known ICC sRGB profiles */
static const struct
{
png_uint_32 adler, crc, length;
png_uint_32 md5[4];
png_byte have_md5;
png_byte is_broken;
png_uint_16 intent;
# define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)
# define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\
{ adler, crc, length, md5, broke, intent },
} png_sRGB_checks[] =
{
/* This data comes from contrib/tools/checksum-icc run on downloads of
* all four ICC sRGB profiles from www.color.org.
*/
/* adler32, crc32, MD5[4], intent, date, length, file-name */
PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9,
PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0,
"2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
/* ICC sRGB v2 perceptual no black-compensation: */
PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0,
"2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0,
"2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
/* ICC sRGB v4 perceptual */
PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0,
"2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
/* The following profiles have no known MD5 checksum. If there is a match
* on the (empty) MD5 the other fields are used to attempt a match and
* a warning is produced. The first two of these profiles have a 'cprt' tag
* which suggests that they were also made by Hewlett Packard.
*/
PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0,
"2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
/* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not
* match the D50 PCS illuminant in the header (it is in fact the D65 values,
* so the white point is recorded as the un-adapted value.) The profiles
* below only differ in one byte - the intent - and are basically the same as
* the previous profile except for the mediaWhitePointTag error and a missing
* chromaticAdaptationTag.
*/
PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/,
"1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual")
PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d,
PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/,
"1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative")
};
static int
png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
png_const_bytep profile, uLong adler)
{
/* The quick check is to verify just the MD5 signature and trust the
* rest of the data. Because the profile has already been verified for
* correctness this is safe. png_colorspace_set_sRGB will check the 'intent'
* field too, so if the profile has been edited with an intent not defined
* by sRGB (but maybe defined by a later ICC specification) the read of
* the profile will fail at that point.
*/
png_uint_32 length = 0;
png_uint_32 intent = 0x10000; /* invalid */
#if PNG_sRGB_PROFILE_CHECKS > 1
uLong crc = 0; /* the value for 0 length data */
#endif
unsigned int i;
for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)
{
if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&
png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&
png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&
png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])
{
/* This may be one of the old HP profiles without an MD5, in that
* case we can only use the length and Adler32 (note that these
* are not used by default if there is an MD5!)
*/
# if PNG_sRGB_PROFILE_CHECKS == 0
if (png_sRGB_checks[i].have_md5)
return 1+png_sRGB_checks[i].is_broken;
# endif
/* Profile is unsigned or more checks have been configured in. */
if (length == 0)
{
length = png_get_uint_32(profile);
intent = png_get_uint_32(profile+64);
}
/* Length *and* intent must match */
if (length == png_sRGB_checks[i].length &&
intent == png_sRGB_checks[i].intent)
{
/* Now calculate the adler32 if not done already. */
if (adler == 0)
{
adler = adler32(0, NULL, 0);
adler = adler32(adler, profile, length);
}
if (adler == png_sRGB_checks[i].adler)
{
/* These basic checks suggest that the data has not been
* modified, but if the check level is more than 1 perform
* our own crc32 checksum on the data.
*/
# if PNG_sRGB_PROFILE_CHECKS > 1
if (crc == 0)
{
crc = crc32(0, NULL, 0);
crc = crc32(crc, profile, length);
}
/* So this check must pass for the 'return' below to happen.
*/
if (crc == png_sRGB_checks[i].crc)
# endif
{
if (png_sRGB_checks[i].is_broken)
{
/* These profiles are known to have bad data that may cause
* problems if they are used, therefore attempt to
* discourage their use, skip the 'have_md5' warning below,
* which is made irrelevant by this error.
*/
png_chunk_report(png_ptr, "known incorrect sRGB profile",
PNG_CHUNK_ERROR);
}
/* Warn that this being done; this isn't even an error since
* the profile is perfectly valid, but it would be nice if
* people used the up-to-date ones.
*/
else if (!png_sRGB_checks[i].have_md5)
{
png_chunk_report(png_ptr,
"out-of-date sRGB profile with no signature",
PNG_CHUNK_WARNING);
}
return 1+png_sRGB_checks[i].is_broken;
}
}
}
# if PNG_sRGB_PROFILE_CHECKS > 0
/* The signature matched, but the profile had been changed in some
* way. This probably indicates a data error or uninformed hacking.
* Fall through to "no match".
*/
png_chunk_report(png_ptr,
"Not recognizing known sRGB profile that has been edited",
PNG_CHUNK_WARNING);
break;
# endif
}
}
return 0; /* no match */
}
#endif
#ifdef PNG_sRGB_SUPPORTED
void /* PRIVATE */
png_icc_set_sRGB(png_const_structrp png_ptr,
png_colorspacerp colorspace, png_const_bytep profile, uLong adler)
{
/* Is this profile one of the known ICC sRGB profiles? If it is, just set
* the sRGB information.
*/
if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler))
(void)png_colorspace_set_sRGB(png_ptr, colorspace,
(int)/*already checked*/png_get_uint_32(profile+64));
}
#endif /* PNG_READ_sRGB_SUPPORTED */
int /* PRIVATE */
png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,
png_const_charp name, png_uint_32 profile_length, png_const_bytep profile,
int color_type)
{
if (colorspace->flags & PNG_COLORSPACE_INVALID)
return 0;
if (png_icc_check_length(png_ptr, colorspace, name, profile_length) &&
png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,
color_type) &&
png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
profile))
{
# ifdef PNG_sRGB_SUPPORTED
/* If no sRGB support, don't try storing sRGB information */
png_icc_set_sRGB(png_ptr, colorspace, profile, 0);
# endif
return 1;
}
/* Failure case */
return 0;
}
#endif /* iCCP */
#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
void /* PRIVATE */
png_colorspace_set_rgb_coefficients(png_structrp png_ptr)
{
/* Set the rgb_to_gray coefficients from the colorspace. */
if (!png_ptr->rgb_to_gray_coefficients_set &&
(png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
{
/* png_set_background has not been called, get the coefficients from the Y
* values of the colorspace colorants.
*/
png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y;
png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y;
png_fixed_point b = png_ptr->colorspace.end_points_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;
}
}
/* This is a png_error at present even though it could be ignored -
* it should never happen, but it is important that if it does, the
* bug is fixed.
*/
else
png_error(png_ptr, "internal error handling cHRM->XYZ");
}
}
#endif
#endif /* COLORSPACE */
#ifdef __GNUC__
/* This exists solely to work round a warning from GNU C. */
static int /* PRIVATE */
png_gt(size_t a, size_t b)
{
return a > b;
}
#else
# define png_gt(a,b) ((a) > (b))
#endif
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;
}
else if (width > PNG_UINT_31_MAX)
{
png_warning(png_ptr, "Invalid image width in IHDR");
error = 1;
}
else if (png_gt(width,
(PNG_SIZE_MAX >> 3) /* 8-byte RGBA pixels */
- 48 /* big_row_buf hack */
- 1 /* filter byte */
- 7*8 /* rounding width to multiple of 8 pix */
- 8)) /* 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
else if (width > png_ptr->user_width_max)
# else
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;
}
# 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;
}
if (height > PNG_UINT_31_MAX)
{
png_warning(png_ptr, "Invalid image height 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) &&
png_ptr->mng_features_permitted)
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) &&
(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)
{
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 formated 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, png_size_t size, int *statep,
png_size_tp whereami)
{
int state = *statep;
png_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)
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) /* two dots */
goto PNG_FP_End;
else if (state & PNG_FP_SAW_DIGIT) /* 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) /* 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)
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, png_size_t size)
{
int state=0;
png_size_t char_index=0;
if (png_check_fp_number(string, size, &state, &char_index) &&
(char_index == size || string[char_index] == 0))
return state /* must be non-zero - see above */;
return 0; /* i.e. fail */
}
#endif /* pCAL or 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) 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, png_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.
*/
{
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 = -exp_b10; /* PLUS 2 digits: TOTAL 3 */
exp_b10 = 0; /* Dot added below before first output. */
}