JDK14/Java14源码在线阅读
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/* png.c - location for general purpose libpng functions
*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file and, per its terms, should not be removed:
*
* Copyright (c) 2018-2019 Cosmin Truta
* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
* Copyright (c) 1996-1997 Andreas Dilger
* Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
#include "pngpriv.h"
/* Generate a compiler error if there is an old png.h in the search path. */
typedef png_libpng_version_1_6_37 Your_png_h_is_not_version_1_6_37;
#ifdef __GNUC__
/* The version tests may need to be added to, but the problem warning has
* consistently been fixed in GCC versions which obtain wide-spread release.
* The problem is that many versions of GCC rearrange comparison expressions in
* the optimizer in such a way that the results of the comparison will change
* if signed integer overflow occurs. Such comparisons are not permitted in
* ANSI C90, however GCC isn't clever enough to work out that that do not occur
* below in png_ascii_from_fp and png_muldiv, so it produces a warning with
* -Wextra. Unfortunately this is highly dependent on the optimizer and the
* machine architecture so the warning comes and goes unpredictably and is
* impossible to "fix", even were that a good idea.
*/
#if __GNUC__ == 7 && __GNUC_MINOR__ == 1
#define GCC_STRICT_OVERFLOW 1
#endif /* GNU 7.1.x */
#endif /* GNU */
#ifndef GCC_STRICT_OVERFLOW
#define GCC_STRICT_OVERFLOW 0
#endif
/* Tells libpng that we have already handled the first "num_bytes" bytes
* of the PNG file signature. If the PNG data is embedded into another
* stream we can set num_bytes = 8 so that libpng will not attempt to read
* or write any of the magic bytes before it starts on the IHDR.
*/
#ifdef PNG_READ_SUPPORTED
void PNGAPI
png_set_sig_bytes(png_structrp png_ptr, int num_bytes)
{
unsigned int nb = (unsigned int)num_bytes;
png_debug(1, "in png_set_sig_bytes");
if (png_ptr == NULL)
return;
if (num_bytes < 0)
nb = 0;
if (nb > 8)
png_error(png_ptr, "Too many bytes for PNG signature");
png_ptr->sig_bytes = (png_byte)nb;
}
/* Checks whether the supplied bytes match the PNG signature. We allow
* checking less than the full 8-byte signature so that those apps that
* already read the first few bytes of a file to determine the file type
* can simply check the remaining bytes for extra assurance. Returns
* an integer less than, equal to, or greater than zero if sig is found,
* respectively, to be less than, to match, or be greater than the correct
* PNG signature (this is the same behavior as strcmp, memcmp, etc).
*/
int PNGAPI
png_sig_cmp(png_const_bytep sig, size_t start, size_t num_to_check)
{
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 /* READ */
#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
/* Function to allocate memory for zlib */
PNG_FUNCTION(voidpf /* PRIVATE */,
png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)
{
png_alloc_size_t num_bytes = size;
if (png_ptr == NULL)
return NULL;
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, size_t length)
{
int need_crc = 1;
if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0)
{
if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) ==
(PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN))
need_crc = 0;
}
else /* critical */
{
if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0)
need_crc = 0;
}
/* 'uLong' is defined in zlib.h as unsigned long; this means that on some
* systems it is a 64-bit value. crc32, however, returns 32 bits so the
* following cast is safe. 'uInt' may be no more than 16 bits, so it is
* necessary to perform a loop here.
*/
if (need_crc != 0 && length > 0)
{
uLong crc = png_ptr->crc; /* Should never issue a warning */
do
{
uInt safe_length = (uInt)length;
#ifndef __COVERITY__
if (safe_length == 0)
safe_length = (uInt)-1; /* evil, but safe */
#endif
crc = crc32(crc, ptr, safe_length);
/* The following should never issue compiler warnings; if they do the
* target system has characteristics that will probably violate other
* assumptions within the libpng code.
*/
ptr += safe_length;
length -= safe_length;
}
while (length > 0);
/* And the following is always safe because the crc is only 32 bits. */
png_ptr->crc = (png_uint_32)crc;
}
}
/* Check a user supplied version number, called from both read and write
* functions that create a png_struct.
*/
int
png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver)
{
/* Libpng versions 1.0.0 and later are binary compatible if the version
* string matches through the second '.'; we must recompile any
* applications that use any older library version.
*/
if (user_png_ver != NULL)
{
int i = -1;
int found_dots = 0;
do
{
i++;
if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i])
png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
if (user_png_ver[i] == '.')
found_dots++;
} while (found_dots < 2 && user_png_ver[i] != 0 &&
PNG_LIBPNG_VER_STRING[i] != 0);
}
else
png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
if ((png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH) != 0)
{
#ifdef PNG_WARNINGS_SUPPORTED
size_t pos = 0;
char m[128];
pos = png_safecat(m, (sizeof m), pos,
"Application built with libpng-");
pos = png_safecat(m, (sizeof m), pos, user_png_ver);
pos = png_safecat(m, (sizeof m), pos, " but running with ");
pos = png_safecat(m, (sizeof m), pos, PNG_LIBPNG_VER_STRING);
PNG_UNUSED(pos)
png_warning(png_ptr, m);
#endif
#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))
# endif
{
# ifdef PNG_SETJMP_SUPPORTED
/* Temporarily fake out the longjmp information until we have
* successfully completed this function. This only works if we have
* setjmp() support compiled in, but it is safe - this stuff should
* never happen.
*/
create_struct.jmp_buf_ptr = &create_jmp_buf;
create_struct.jmp_buf_size = 0; /*stack allocation*/
create_struct.longjmp_fn = longjmp;
# endif
/* Call the general version checker (shared with read and write code):
*/
if (png_user_version_check(&create_struct, user_png_ver) != 0)
{
png_structrp png_ptr = png_voidcast(png_structrp,
png_malloc_warn(&create_struct, (sizeof *png_ptr)));
if (png_ptr != NULL)
{
/* png_ptr->zstream holds a back-pointer to the png_struct, so
* this can only be done now:
*/
create_struct.zstream.zalloc = png_zalloc;
create_struct.zstream.zfree = png_zfree;
create_struct.zstream.opaque = png_ptr;
# ifdef PNG_SETJMP_SUPPORTED
/* Eliminate the local error handling: */
create_struct.jmp_buf_ptr = NULL;
create_struct.jmp_buf_size = 0;
create_struct.longjmp_fn = 0;
# endif
*png_ptr = create_struct;
/* This is the successful return point */
return png_ptr;
}
}
}
/* A longjmp because of a bug in the application storage allocator or a
* simple failure to allocate the png_struct.
*/
return NULL;
}
/* Allocate the memory for an info_struct for the application. */
PNG_FUNCTION(png_infop,PNGAPI
png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED)
{
png_inforp info_ptr;
png_debug(1, "in png_create_info_struct");
if (png_ptr == NULL)
return NULL;
/* Use the internal API that does not (or at least should not) error out, so
* that this call always returns ok. The application typically sets up the
* error handling *after* creating the info_struct because this is the way it
* has always been done in 'example.c'.
*/
info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr,
(sizeof *info_ptr)));
if (info_ptr != NULL)
memset(info_ptr, 0, (sizeof *info_ptr));
return info_ptr;
}
/* This function frees the memory associated with a single info struct.
* Normally, one would use either png_destroy_read_struct() or
* png_destroy_write_struct() to free an info struct, but this may be
* useful for some applications. From libpng 1.6.0 this function is also used
* internally to implement the png_info release part of the 'struct' destroy
* APIs. This ensures that all possible approaches free the same data (all of
* it).
*/
void PNGAPI
png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr)
{
png_inforp info_ptr = NULL;
png_debug(1, "in png_destroy_info_struct");
if (png_ptr == NULL)
return;
if (info_ptr_ptr != NULL)
info_ptr = *info_ptr_ptr;
if (info_ptr != NULL)
{
/* Do this first in case of an error below; if the app implements its own
* memory management this can lead to png_free calling png_error, which
* will abort this routine and return control to the app error handler.
* An infinite loop may result if it then tries to free the same info
* ptr.
*/
*info_ptr_ptr = NULL;
png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
memset(info_ptr, 0, (sizeof *info_ptr));
png_free(png_ptr, info_ptr);
}
}
/* Initialize the info structure. This is now an internal function (0.89)
* and applications using it are urged to use png_create_info_struct()
* instead. Use deprecated in 1.6.0, internal use removed (used internally it
* is just a memset).
*
* NOTE: it is almost inconceivable that this API is used because it bypasses
* the user-memory mechanism and the user error handling/warning mechanisms in
* those cases where it does anything other than a memset.
*/
PNG_FUNCTION(void,PNGAPI
png_info_init_3,(png_infopp ptr_ptr, size_t png_info_struct_size),
PNG_DEPRECATED)
{
png_inforp info_ptr = *ptr_ptr;
png_debug(1, "in png_info_init_3");
if (info_ptr == NULL)
return;
if ((sizeof (png_info)) > png_info_struct_size)
{
*ptr_ptr = NULL;
/* The following line is why this API should not be used: */
free(info_ptr);
info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
(sizeof *info_ptr)));
if (info_ptr == NULL)
return;
*ptr_ptr = info_ptr;
}
/* Set everything to 0 */
memset(info_ptr, 0, (sizeof *info_ptr));
}
/* 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 (info_ptr->text != NULL &&
((mask & PNG_FREE_TEXT) & info_ptr->free_me) != 0)
{
if (num != -1)
{
png_free(png_ptr, info_ptr->text[num].key);
info_ptr->text[num].key = NULL;
}
else
{
int i;
for (i = 0; i < info_ptr->num_text; i++)
png_free(png_ptr, info_ptr->text[i].key);
png_free(png_ptr, info_ptr->text);
info_ptr->text = NULL;
info_ptr->num_text = 0;
info_ptr->max_text = 0;
}
}
#endif
#ifdef PNG_tRNS_SUPPORTED
/* Free any tRNS entry */
if (((mask & PNG_FREE_TRNS) & info_ptr->free_me) != 0)
{
info_ptr->valid &= ~PNG_INFO_tRNS;
png_free(png_ptr, info_ptr->trans_alpha);
info_ptr->trans_alpha = NULL;
info_ptr->num_trans = 0;
}
#endif
#ifdef PNG_sCAL_SUPPORTED
/* Free any sCAL entry */
if (((mask & PNG_FREE_SCAL) & info_ptr->free_me) != 0)
{
png_free(png_ptr, info_ptr->scal_s_width);
png_free(png_ptr, info_ptr->scal_s_height);
info_ptr->scal_s_width = NULL;
info_ptr->scal_s_height = NULL;
info_ptr->valid &= ~PNG_INFO_sCAL;
}
#endif
#ifdef PNG_pCAL_SUPPORTED
/* Free any pCAL entry */
if (((mask & PNG_FREE_PCAL) & info_ptr->free_me) != 0)
{
png_free(png_ptr, info_ptr->pcal_purpose);
png_free(png_ptr, info_ptr->pcal_units);
info_ptr->pcal_purpose = NULL;
info_ptr->pcal_units = NULL;
if (info_ptr->pcal_params != NULL)
{
int i;
for (i = 0; i < info_ptr->pcal_nparams; i++)
png_free(png_ptr, info_ptr->pcal_params[i]);
png_free(png_ptr, info_ptr->pcal_params);
info_ptr->pcal_params = NULL;
}
info_ptr->valid &= ~PNG_INFO_pCAL;
}
#endif
#ifdef PNG_iCCP_SUPPORTED
/* Free any profile entry */
if (((mask & PNG_FREE_ICCP) & info_ptr->free_me) != 0)
{
png_free(png_ptr, info_ptr->iccp_name);
png_free(png_ptr, info_ptr->iccp_profile);
info_ptr->iccp_name = NULL;
info_ptr->iccp_profile = NULL;
info_ptr->valid &= ~PNG_INFO_iCCP;
}
#endif
#ifdef PNG_sPLT_SUPPORTED
/* Free a given sPLT entry, or (if num == -1) all sPLT entries */
if (info_ptr->splt_palettes != NULL &&
((mask & PNG_FREE_SPLT) & info_ptr->free_me) != 0)
{
if (num != -1)
{
png_free(png_ptr, info_ptr->splt_palettes[num].name);
png_free(png_ptr, info_ptr->splt_palettes[num].entries);
info_ptr->splt_palettes[num].name = NULL;
info_ptr->splt_palettes[num].entries = NULL;
}
else
{
int i;
for (i = 0; i < info_ptr->splt_palettes_num; i++)
{
png_free(png_ptr, info_ptr->splt_palettes[i].name);
png_free(png_ptr, info_ptr->splt_palettes[i].entries);
}
png_free(png_ptr, info_ptr->splt_palettes);
info_ptr->splt_palettes = NULL;
info_ptr->splt_palettes_num = 0;
info_ptr->valid &= ~PNG_INFO_sPLT;
}
}
#endif
#ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
if (info_ptr->unknown_chunks != NULL &&
((mask & PNG_FREE_UNKN) & info_ptr->free_me) != 0)
{
if (num != -1)
{
png_free(png_ptr, info_ptr->unknown_chunks[num].data);
info_ptr->unknown_chunks[num].data = NULL;
}
else
{
int i;
for (i = 0; i < info_ptr->unknown_chunks_num; i++)
png_free(png_ptr, info_ptr->unknown_chunks[i].data);
png_free(png_ptr, info_ptr->unknown_chunks);
info_ptr->unknown_chunks = NULL;
info_ptr->unknown_chunks_num = 0;
}
}
#endif
#ifdef PNG_eXIf_SUPPORTED
/* Free any eXIf entry */
if (((mask & PNG_FREE_EXIF) & info_ptr->free_me) != 0)
{
# ifdef PNG_READ_eXIf_SUPPORTED
if (info_ptr->eXIf_buf)
{
png_free(png_ptr, info_ptr->eXIf_buf);
info_ptr->eXIf_buf = NULL;
}
# endif
if (info_ptr->exif)
{
png_free(png_ptr, info_ptr->exif);
info_ptr->exif = NULL;
}
info_ptr->valid &= ~PNG_INFO_eXIf;
}
#endif
#ifdef PNG_hIST_SUPPORTED
/* Free any hIST entry */
if (((mask & PNG_FREE_HIST) & info_ptr->free_me) != 0)
{
png_free(png_ptr, info_ptr->hist);
info_ptr->hist = NULL;
info_ptr->valid &= ~PNG_INFO_hIST;
}
#endif
/* Free any PLTE entry that was internally allocated */
if (((mask & PNG_FREE_PLTE) & info_ptr->free_me) != 0)
{
png_free(png_ptr, info_ptr->palette);
info_ptr->palette = NULL;
info_ptr->valid &= ~PNG_INFO_PLTE;
info_ptr->num_palette = 0;
}
#ifdef PNG_INFO_IMAGE_SUPPORTED
/* Free any image bits attached to the info structure */
if (((mask & PNG_FREE_ROWS) & info_ptr->free_me) != 0)
{
if (info_ptr->row_pointers != NULL)
{
png_uint_32 row;
for (row = 0; row < info_ptr->height; row++)
png_free(png_ptr, info_ptr->row_pointers[row]);
png_free(png_ptr, info_ptr->row_pointers);
info_ptr->row_pointers = NULL;
}
info_ptr->valid &= ~PNG_INFO_IDAT;
}
#endif
if (num != -1)
mask &= ~PNG_FREE_MUL;
info_ptr->free_me &= ~mask;
}
#endif /* READ || WRITE */
/* This function returns a pointer to the io_ptr associated with the user
* functions. The application should free any memory associated with this
* pointer before png_write_destroy() or png_read_destroy() are called.
*/
png_voidp PNGAPI
png_get_io_ptr(png_const_structrp png_ptr)
{
if (png_ptr == NULL)
return (NULL);
return (png_ptr->io_ptr);
}
#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
# ifdef PNG_STDIO_SUPPORTED
/* Initialize the default input/output functions for the PNG file. If you
* use your own read or write routines, you can call either png_set_read_fn()
* or png_set_write_fn() instead of png_init_io(). If you have defined
* PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a
* function of your own because "FILE *" isn't necessarily available.
*/
void PNGAPI
png_init_io(png_structrp png_ptr, 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
/* PNG signed integers are saved in 32-bit 2's complement format. ANSI C-90
* defines a cast of a signed integer to an unsigned integer either to preserve
* the value, if it is positive, or to calculate:
*
* (UNSIGNED_MAX+1) + integer
*
* Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the
* negative integral value is added the result will be an unsigned value
* correspnding to the 2's complement representation.
*/
void PNGAPI
png_save_int_32(png_bytep buf, png_int_32 i)
{
png_save_uint_32(buf, (png_uint_32)i);
}
# endif
# ifdef PNG_TIME_RFC1123_SUPPORTED
/* Convert the supplied time into an RFC 1123 string suitable for use in
* a "Creation Time" or other text-based time string.
*/
int PNGAPI
png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
{
static const char short_months[12][4] =
{"Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
if (out == NULL)
return 0;
if (ptime->year > 9999 /* RFC1123 limitation */ ||
ptime->month == 0 || ptime->month > 12 ||
ptime->day == 0 || ptime->day > 31 ||
ptime->hour > 23 || ptime->minute > 59 ||
ptime->second > 60)
return 0;
{
size_t pos = 0;
char number_buf[5]; /* enough for a four-digit year */
# define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string))
# define APPEND_NUMBER(format, value)\
APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value)))
# define APPEND(ch) if (pos < 28) out[pos++] = (ch)
APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day);
APPEND(' ');
APPEND_STRING(short_months[(ptime->month - 1)]);
APPEND(' ');
APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year);
APPEND(' ');
APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour);
APPEND(':');
APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute);
APPEND(':');
APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second);
APPEND_STRING(" +0000"); /* This reliably terminates the buffer */
PNG_UNUSED (pos)
# undef APPEND
# undef APPEND_NUMBER
# undef APPEND_STRING
}
return 1;
}
# if PNG_LIBPNG_VER < 10700
/* To do: remove the following from libpng-1.7 */
/* Original API that uses a private buffer in png_struct.
* Deprecated because it causes png_struct to carry a spurious temporary
* buffer (png_struct::time_buffer), better to have the caller pass this in.
*/
png_const_charp PNGAPI
png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime)
{
if (png_ptr != NULL)
{
/* The only failure above if png_ptr != NULL is from an invalid ptime */
if (png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime) == 0)
png_warning(png_ptr, "Ignoring invalid time value");
else
return png_ptr->time_buffer;
}
return NULL;
}
# endif /* LIBPNG_VER < 10700 */
# endif /* TIME_RFC1123 */
#endif /* READ || WRITE */
png_const_charp PNGAPI
png_get_copyright(png_const_structrp png_ptr)
{
PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
#ifdef PNG_STRING_COPYRIGHT
return PNG_STRING_COPYRIGHT
#else
return PNG_STRING_NEWLINE \
"libpng version 1.6.37" PNG_STRING_NEWLINE \
"Copyright (c) 2018-2019 Cosmin Truta" PNG_STRING_NEWLINE \
"Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson" \
PNG_STRING_NEWLINE \
"Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
"Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
PNG_STRING_NEWLINE;
#endif
}
/* The following return the library version as a short string in the
* format 1.0.0 through 99.99.99zz. To get the version of *.h files
* used with your application, print out PNG_LIBPNG_VER_STRING, which
* is defined in png.h.
* Note: now there is no difference between png_get_libpng_ver() and
* png_get_header_ver(). Due to the version_nn_nn_nn typedef guard,
* it is guaranteed that png.c uses the correct version of png.h.
*/
png_const_charp PNGAPI
png_get_libpng_ver(png_const_structrp png_ptr)
{
/* Version of *.c files used when building libpng */
return png_get_header_ver(png_ptr);
}
png_const_charp PNGAPI
png_get_header_ver(png_const_structrp png_ptr)
{
/* Version of *.h files used when building libpng */
PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
return PNG_LIBPNG_VER_STRING;
}
png_const_charp PNGAPI
png_get_header_version(png_const_structrp png_ptr)
{
/* Returns longer string containing both version and date */
PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */
#ifdef __STDC__
return PNG_HEADER_VERSION_STRING
# ifndef PNG_READ_SUPPORTED
" (NO READ SUPPORT)"
# endif
PNG_STRING_NEWLINE;
#else
return PNG_HEADER_VERSION_STRING;
#endif
}
#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
/* NOTE: this routine is not used internally! */
/* Build a grayscale palette. Palette is assumed to be 1 << bit_depth
* large of png_color. This lets grayscale images be treated as
* paletted. Most useful for gamma correction and simplification
* of code. This API is not used internally.
*/
void PNGAPI
png_build_grayscale_palette(int bit_depth, png_colorp palette)
{
int num_palette;
int color_inc;
int i;
int v;
png_debug(1, "in png_do_build_grayscale_palette");
if (palette == NULL)
return;
switch (bit_depth)
{
case 1:
num_palette = 2;
color_inc = 0xff;
break;
case 2:
num_palette = 4;
color_inc = 0x55;
break;
case 4:
num_palette = 16;
color_inc = 0x11;
break;
case 8:
num_palette = 256;
color_inc = 1;
break;
default:
num_palette = 0;
color_inc = 0;
break;
}
for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
{
palette[i].red = (png_byte)(v & 0xff);
palette[i].green = (png_byte)(v & 0xff);
palette[i].blue = (png_byte)(v & 0xff);
}
}
#endif
#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
int PNGAPI
png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name)
{
/* Check chunk_name and return "keep" value if it's on the list, else 0 */
png_const_bytep p, p_end;
if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0)
return PNG_HANDLE_CHUNK_AS_DEFAULT;
p_end = png_ptr->chunk_list;
p = p_end + png_ptr->num_chunk_list*5; /* beyond end */
/* The code is the fifth byte after each four byte string. Historically this
* code was always searched from the end of the list, this is no longer
* necessary because the 'set' routine handles duplicate entries correctly.
*/
do /* num_chunk_list > 0, so at least one */
{
p -= 5;
if (memcmp(chunk_name, p, 4) == 0)
return p[4];
}
while (p > p_end);
/* This means that known chunks should be processed and unknown chunks should
* be handled according to the value of png_ptr->unknown_default; this can be
* confusing because, as a result, there are two levels of defaulting for
* unknown chunks.
*/
return PNG_HANDLE_CHUNK_AS_DEFAULT;
}
#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
int /* PRIVATE */
png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name)
{
png_byte chunk_string[5];
PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name);
return png_handle_as_unknown(png_ptr, chunk_string);
}
#endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */
#endif /* SET_UNKNOWN_CHUNKS */
#ifdef PNG_READ_SUPPORTED
/* This function, added to libpng-1.0.6g, is untested. */
int PNGAPI
png_reset_zstream(png_structrp png_ptr)
{
if (png_ptr == NULL)
return Z_STREAM_ERROR;
/* WARNING: this resets the window bits to the maximum! */
return (inflateReset(&png_ptr->zstream));
}
#endif /* READ */
/* This function was added to libpng-1.0.7 */
png_uint_32 PNGAPI
png_access_version_number(void)
{
/* Version of *.c files used when building libpng */
return((png_uint_32)PNG_LIBPNG_VER);
}
#if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
/* Ensure that png_ptr->zstream.msg holds some appropriate error message string.
* If it doesn't 'ret' is used to set it to something appropriate, even in cases
* like Z_OK or Z_STREAM_END where the error code is apparently a success code.
*/
void /* PRIVATE */
png_zstream_error(png_structrp png_ptr, int ret)
{
/* Translate 'ret' into an appropriate error string, priority is given to the
* one in zstream if set. This always returns a string, even in cases like
* Z_OK or Z_STREAM_END where the error code is a success code.
*/
if (png_ptr->zstream.msg == NULL) switch (ret)
{
default:
case Z_OK:
png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code");
break;
case Z_STREAM_END:
/* Normal exit */
png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream");
break;
case Z_NEED_DICT:
/* This means the deflate stream did not have a dictionary; this
* indicates a bogus PNG.
*/
png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary");
break;
case Z_ERRNO:
/* gz APIs only: should not happen */
png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error");
break;
case Z_STREAM_ERROR:
/* internal libpng error */
png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib");
break;
case Z_DATA_ERROR:
png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream");
break;
case Z_MEM_ERROR:
png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory");
break;
case Z_BUF_ERROR:
/* End of input or output; not a problem if the caller is doing
* incremental read or write.
*/
png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated");
break;
case Z_VERSION_ERROR:
png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version");
break;
case PNG_UNEXPECTED_ZLIB_RETURN:
/* Compile errors here mean that zlib now uses the value co-opted in
* pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above
* and change pngpriv.h. Note that this message is "... return",
* whereas the default/Z_OK one is "... return code".
*/
png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return");
break;
}
}
/* 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(>est, colorspace->gamma, PNG_FP_1, gAMA) == 0 ||
png_gamma_significant(gtest) != 0))
{
/* 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 asymmetrical 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) != 0)
return;
else
{
if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA,
1/*from gAMA*/) != 0)
{
/* 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) != 0)
{
/* 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) != 0)
info_ptr->valid |= PNG_INFO_sRGB;
else
info_ptr->valid &= ~PNG_INFO_sRGB;
if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0)
info_ptr->valid |= PNG_INFO_cHRM;
else
info_ptr->valid &= ~PNG_INFO_cHRM;
# endif
if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0)
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 /* GAMMA */
#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) == 0)
return 1;
if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d) == 0)
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) == 0)
return 1;
if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d) == 0)
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) == 0)
return 1;
if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d) == 0)
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) == 0)
return 1;
if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0)
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). We check
* xy->whitey against 5, not 0, to avoid a possible integer overflow.
*/
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 < 5 || 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 inversion of the above equations
* ------------------------------------------------------------
*
* white_scale = 1/white-y
* white-X = white-x * white-scale
* white-Y = 1.0
* white-Z = (1 - white-x - white-y) * white_scale
*
* white-C = red-C + green-C + blue-C
* = red-c*red-scale + green-c*green-scale + blue-c*blue-scale
*
* This gives us three equations in (red-scale,green-scale,blue-scale) where
* all the coefficients are now known:
*
* red-x*red-scale + green-x*green-scale + blue-x*blue-scale
* = white-x/white-y
* red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1
* red-z*red-scale + green-z*green-scale + blue-z*blue-scale
* = (1 - white-x - white-y)/white-y
*
* In the last equation color-z is (1 - color-x - color-y) so we can add all
* three equations together to get an alternative third:
*
* red-scale + green-scale + blue-scale = 1/white-y = white-scale
*
* So now we have a Cramer's rule solution where the determinants are just
* 3x3 - far more 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) == 0)
return 2;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7) == 0)
return 2;
denominator = left - right;
/* Now find the red numerator. */
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7) == 0)
return 2;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7) == 0)
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) == 0 ||
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) == 0)
return 2;
if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7) == 0)
return 2;
if (png_muldiv(&green_inverse, xy->whitey, denominator, left-right) == 0 ||
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) == 0)
return 1;
if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) == 0)
return 1;
if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
red_inverse) == 0)
return 1;
if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) == 0)
return 1;
if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) == 0)
return 1;
if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
green_inverse) == 0)
return 1;
if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) == 0)
return 1;
if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0)
return 1;
if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
PNG_FP_1) == 0)
return 1;
return 0; /*success*/
}
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) == 0)
return 1;
if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0)
return 1;
if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0)
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 */
if (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))
return 0;
return 1;
}
/* 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 != 0)
return result;
result = png_xy_from_XYZ(&xy_test, XYZ);
if (result != 0)
return result;
if (png_colorspace_endpoints_match(xy, &xy_test,
5/*actually, the math is pretty accurate*/) != 0)
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 != 0)
return result;
result = png_xy_from_XYZ(xy, XYZ);
if (result != 0)
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) != 0)
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) != 0)
{
/* 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) == 0)
{
colorspace->flags |= PNG_COLORSPACE_INVALID;
png_benign_error(png_ptr, "inconsistent chromaticities");
return 0; /* failed */
}
/* Only overwrite with preferred values */
if (preferred == 0)
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) != 0)
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");
}
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");
}
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) != 0)
{
/* So 'value' is at most 4 bytes and the following cast is safe */
png_icc_tag_name(message+pos, (png_uint_32)value);
pos += 6; /* total +8; less than the else clause */
message[pos++] = ':';
message[pos++] = ' ';
}
# ifdef PNG_WARNINGS_SUPPORTED
else
{
char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/
pos = png_safecat(message, (sizeof message), pos,
png_format_number(number, number+(sizeof number),
PNG_NUMBER_FORMAT_x, value));
pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/
}
# endif
/* The 'reason' is an arbitrary message, allow +79 maximum 195 */
pos = png_safecat(message, (sizeof message), pos, reason);
PNG_UNUSED(pos)
/* 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) != 0)
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",
(png_alloc_size_t)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",
(png_alloc_size_t)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 };
static int /* bool */
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");
return 1;
}
#ifdef PNG_READ_iCCP_SUPPORTED
int /* PRIVATE */
png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace,
png_const_charp name, png_uint_32 profile_length)
{
if (!icc_check_length(png_ptr, colorspace, name, profile_length))
return 0;
/* This needs to be here because the 'normal' check is in
* png_decompress_chunk, yet this happens after the attempt to
* png_malloc_base the required data. We only need this on read; on write
* the caller supplies the profile buffer so libpng doesn't allocate it. See
* the call to icc_check_length below (the write case).
*/
# ifdef PNG_SET_USER_LIMITS_SUPPORTED
else if (png_ptr->user_chunk_malloc_max > 0 &&
png_ptr->user_chunk_malloc_max < profile_length)
return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
"exceeds application limits");
# elif PNG_USER_CHUNK_MALLOC_MAX > 0
else if (PNG_USER_CHUNK_MALLOC_MAX < profile_length)
return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
"exceeds libpng limits");
# else /* !SET_USER_LIMITS */
/* This will get compiled out on all 32-bit and better systems. */
else if (PNG_SIZE_MAX < profile_length)
return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
"exceeds system limits");
# endif /* !SET_USER_LIMITS */
return 1;
}
#endif /* READ_iCCP */
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_uint_32) (*(profile+8));
if (temp > 3 && (profile_length & 3))
return png_icc_profile_error(png_ptr, colorspace, name, profile_length,
"invalid length");
temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */
if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */
profile_length < 132+12*temp) /* truncated tag table */
return png_icc_profile_error(png_ptr, 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 accommodate changes in
* the header fields (just the known tags and the interpretation of the
* data.)
*/
temp = png_get_uint_32(profile+36); /* signature 'ascp' */
if (temp != 0x61637370)
return png_icc_profile_error(png_ptr, 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) == 0)
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) != 0)
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 cannot be interpreted in a non-device specific
* fashion, if an app uses the AToB0Tag in the profile the results are
* undefined unless the result is sent to the intended device,
* therefore a DeviceLink profile should not be found embedded in a
* PNG.
*/
return png_icc_profile_error(png_ptr, 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 misinterpretation. 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.
*/
/* 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");
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");
}
}
return 1; /* success, maybe with warnings */
}
#ifdef PNG_sRGB_SUPPORTED
#if PNG_sRGB_PROFILE_CHECKS >= 0
/* 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;
#ifdef PNG_SET_OPTION_SUPPORTED
/* First see if PNG_SKIP_sRGB_CHECK_PROFILE has been set to "on" */
if (((png_ptr->options >> PNG_SKIP_sRGB_CHECK_PROFILE) & 3) ==
PNG_OPTION_ON)
return 0;
#endif
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 != 0)
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_uint_32) png_sRGB_checks[i].length &&
intent == (png_uint_32) 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 != 0)
{
/* 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 == 0)
{
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 */
}
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) != 0)
(void)png_colorspace_set_sRGB(png_ptr, colorspace,
(int)/*already checked*/png_get_uint_32(profile+64));
}
#endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */
#endif /* sRGB */
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) != 0)
return 0;
if (icc_check_length(png_ptr, colorspace, name, profile_length) != 0 &&
png_icc_check_header(png_ptr, colorspace, name, profile_length, profile,
color_type) != 0 &&
png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
profile) != 0)
{
# if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0
/* 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 == 0 &&
(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 /* READ_RGB_TO_GRAY */
#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;
}
if (width > PNG_UINT_31_MAX)
{
png_warning(png_ptr, "Invalid image width in IHDR");
error = 1;
}
if (png_gt(((width + 7) & (~7U)),
((PNG_SIZE_MAX
- 48 /* big_row_buf hack */
- 1) /* filter byte */
/ 8) /* 8-byte RGBA pixels */
- 1)) /* extra max_pixel_depth pad */
{
/* The size of the row must be within the limits of this architecture.
* Because the read code can perform arbitrary transformations the
* maximum size is checked here. Because the code in png_read_start_row
* adds extra space "for safety's sake" in several places a conservative
* limit is used here.
*
* NOTE: it would be far better to check the size that is actually used,
* but the effect in the real world is minor and the changes are more
* extensive, therefore much more dangerous and much more difficult to
* write in a way that avoids compiler warnings.
*/
png_warning(png_ptr, "Image width is too large for this architecture");
error = 1;
}
#ifdef PNG_SET_USER_LIMITS_SUPPORTED
if (width > png_ptr->user_width_max)
#else
if (width > PNG_USER_WIDTH_MAX)
#endif
{
png_warning(png_ptr, "Image width exceeds user limit in IHDR");
error = 1;
}
if (height == 0)
{
png_warning(png_ptr, "Image height is zero in IHDR");
error = 1;
}
if (height > PNG_UINT_31_MAX)
{
png_warning(png_ptr, "Invalid image height in IHDR");
error = 1;
}
#ifdef PNG_SET_USER_LIMITS_SUPPORTED
if (height > png_ptr->user_height_max)
#else
if (height > PNG_USER_HEIGHT_MAX)
#endif
{
png_warning(png_ptr, "Image height exceeds user limit in IHDR");
error = 1;
}
/* Check other values */
if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&
bit_depth != 8 && bit_depth != 16)
{
png_warning(png_ptr, "Invalid bit depth in IHDR");
error = 1;
}
if (color_type < 0 || color_type == 1 ||
color_type == 5 || color_type > 6)
{
png_warning(png_ptr, "Invalid color type in IHDR");
error = 1;
}
if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) ||
((color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_GRAY_ALPHA ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8))
{
png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR");
error = 1;
}
if (interlace_type >= PNG_INTERLACE_LAST)
{
png_warning(png_ptr, "Unknown interlace method in IHDR");
error = 1;
}
if (compression_type != PNG_COMPRESSION_TYPE_BASE)
{
png_warning(png_ptr, "Unknown compression method in IHDR");
error = 1;
}
#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Accept filter_method 64 (intrapixel differencing) only if
* 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
* 2. Libpng did not read a PNG signature (this filter_method is only
* used in PNG datastreams that are embedded in MNG datastreams) and
* 3. The application called png_permit_mng_features with a mask that
* included PNG_FLAG_MNG_FILTER_64 and
* 4. The filter_method is 64 and
* 5. The color_type is RGB or RGBA
*/
if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 &&
png_ptr->mng_features_permitted != 0)
png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
if (filter_type != PNG_FILTER_TYPE_BASE)
{
if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 &&
(filter_type == PNG_INTRAPIXEL_DIFFERENCING) &&
((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) &&
(color_type == PNG_COLOR_TYPE_RGB ||
color_type == PNG_COLOR_TYPE_RGB_ALPHA)))
{
png_warning(png_ptr, "Unknown filter method in IHDR");
error = 1;
}
if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0)
{
png_warning(png_ptr, "Invalid filter method in IHDR");
error = 1;
}
}
#else
if (filter_type != PNG_FILTER_TYPE_BASE)
{
png_warning(png_ptr, "Unknown filter method in IHDR");
error = 1;
}
#endif
if (error == 1)
png_error(png_ptr, "Invalid IHDR data");
}
#if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
/* ASCII to fp functions */
/* Check an ASCII formatted floating point value, see the more detailed
* comments in pngpriv.h
*/
/* The following is used internally to preserve the sticky flags */
#define png_fp_add(state, flags) ((state) |= (flags))
#define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
int /* PRIVATE */
png_check_fp_number(png_const_charp string, size_t size, int *statep,
png_size_tp whereami)
{
int state = *statep;
size_t i = *whereami;
while (i < size)
{
int type;
/* First find the type of the next character */
switch (string[i])
{
case 43: type = PNG_FP_SAW_SIGN; break;
case 45: type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break;
case 46: type = PNG_FP_SAW_DOT; break;
case 48: type = PNG_FP_SAW_DIGIT; break;
case 49: case 50: case 51: case 52:
case 53: case 54: case 55: case 56:
case 57: type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break;
case 69:
case 101: type = PNG_FP_SAW_E; break;
default: goto PNG_FP_End;
}
/* Now deal with this type according to the current
* state, the type is arranged to not overlap the
* bits of the PNG_FP_STATE.
*/
switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY))
{
case PNG_FP_INTEGER + PNG_FP_SAW_SIGN:
if ((state & PNG_FP_SAW_ANY) != 0)
goto PNG_FP_End; /* not a part of the number */
png_fp_add(state, type);
break;
case PNG_FP_INTEGER + PNG_FP_SAW_DOT:
/* Ok as trailer, ok as lead of fraction. */
if ((state & PNG_FP_SAW_DOT) != 0) /* two dots */
goto PNG_FP_End;
else if ((state & PNG_FP_SAW_DIGIT) != 0) /* trailing dot? */
png_fp_add(state, type);
else
png_fp_set(state, PNG_FP_FRACTION | type);
break;
case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT:
if ((state & PNG_FP_SAW_DOT) != 0) /* delayed fraction */
png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT);
png_fp_add(state, type | PNG_FP_WAS_VALID);
break;
case PNG_FP_INTEGER + PNG_FP_SAW_E:
if ((state & PNG_FP_SAW_DIGIT) == 0)
goto PNG_FP_End;
png_fp_set(state, PNG_FP_EXPONENT);
break;
/* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN:
goto PNG_FP_End; ** no sign in fraction */
/* case PNG_FP_FRACTION + PNG_FP_SAW_DOT:
goto PNG_FP_End; ** Because SAW_DOT is always set */
case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT:
png_fp_add(state, type | PNG_FP_WAS_VALID);
break;
case PNG_FP_FRACTION + PNG_FP_SAW_E:
/* This is correct because the trailing '.' on an
* integer is handled above - so we can only get here
* with the sequence ".E" (with no preceding digits).
*/
if ((state & PNG_FP_SAW_DIGIT) == 0)
goto PNG_FP_End;
png_fp_set(state, PNG_FP_EXPONENT);
break;
case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN:
if ((state & PNG_FP_SAW_ANY) != 0)
goto PNG_FP_End; /* not a part of the number */
png_fp_add(state, PNG_FP_SAW_SIGN);
break;
/* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT:
goto PNG_FP_End; */
case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT:
png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID);
break;
/* case PNG_FP_EXPONEXT + PNG_FP_SAW_E:
goto PNG_FP_End; */
default: goto PNG_FP_End; /* I.e. break 2 */
}
/* The character seems ok, continue. */
++i;
}
PNG_FP_End:
/* Here at the end, update the state and return the correct
* return code.
*/
*statep = state;
*whereami = i;
return (state & PNG_FP_SAW_DIGIT) != 0;
}
/* The same but for a complete string. */
int
png_check_fp_string(png_const_charp string, size_t size)
{
int state=0;
size_t char_index=0;
if (png_check_fp_number(string, size, &state, &char_index) != 0 &&
(char_index == size || string[char_index] == 0))
return state /* must be non-zero - see above */;
return 0; /* i.e. fail */
}
#endif /* pCAL || sCAL */
#ifdef PNG_sCAL_SUPPORTED
# ifdef PNG_FLOATING_POINT_SUPPORTED
/* Utility used below - a simple accurate power of ten from an integral
* exponent.
*/
static double
png_pow10(int power)
{
int recip = 0;
double d = 1;
/* Handle negative exponent with a reciprocal at the end because
* 10 is exact whereas .1 is inexact in base 2
*/
if (power < 0)
{
if (power < DBL_MIN_10_EXP) return 0;
recip = 1; power = -power;
}
if (power > 0)
{
/* Decompose power bitwise. */
double mult = 10;
do
{
if (power & 1) d *= mult;
mult *= mult;
power >>= 1;
}
while (power > 0);
if (recip != 0) d = 1/d;
}
/* else power is 0 and d is 1 */
return d;
}
/* Function to format a floating point value in ASCII with a given
* precision.
*/
#if GCC_STRICT_OVERFLOW
#pragma GCC diagnostic push
/* The problem arises below with exp_b10, which can never overflow because it
* comes, originally, from frexp and is therefore limited to a range which is
* typically +/-710 (log2(DBL_MAX)/log2(DBL_MIN)).
*/
#pragma GCC diagnostic warning "-Wstrict-overflow=2"
#endif /* GCC_STRICT_OVERFLOW */
void /* PRIVATE */
png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size,
double fp, unsigned int precision)
{
/* We use standard functions from math.h, but not printf because
* that would require stdio. The caller must supply a buffer of
* sufficient size or we will png_error. The tests on size and
* the space in ascii[] consumed are indicated below.
*/
if (precision < 1)
precision = DBL_DIG;
/* Enforce the limit of the implementation precision too. */
if (precision > DBL_DIG+1)
precision = DBL_DIG+1;
/* Basic sanity checks */
if (size >= precision+5) /* See the requirements below. */
{
if (fp < 0)
{
fp = -fp;
*ascii++ = 45; /* '-' PLUS 1 TOTAL 1 */
--size;
}
if (fp >= DBL_MIN && fp <= DBL_MAX)
{
int exp_b10; /* A base 10 exponent */
double base; /* 10^exp_b10 */
/* First extract a base 10 exponent of the number,
* the calculation below rounds down when converting
* from base 2 to base 10 (multiply by log10(2) -
* 0.3010, but 77/256 is 0.3008, so exp_b10 needs to
* be increased. Note that the arithmetic shift
* performs a floor() unlike C arithmetic - using a
* C multiply would break the following for negative
* exponents.
*/
(void)frexp(fp, &exp_b10); /* exponent to base 2 */
exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */
/* Avoid underflow here. */
base = png_pow10(exp_b10); /* May underflow */
while (base < DBL_MIN || base < fp)
{
/* And this may overflow. */
double test = png_pow10(exp_b10+1);
if (test <= DBL_MAX)
{
++exp_b10; base = test;
}
else
break;
}
/* Normalize fp and correct exp_b10, after this fp is in the
* range [.1,1) and exp_b10 is both the exponent and the digit
* *before* which the decimal point should be inserted
* (starting with 0 for the first digit). Note that this
* works even if 10^exp_b10 is out of range because of the
* test on DBL_MAX above.
*/
fp /= base;
while (fp >= 1)
{
fp /= 10; ++exp_b10;
}
/* Because of the code above fp may, at this point, be
* less than .1, this is ok because the code below can
* handle the leading zeros this generates, so no attempt
* is made to correct that here.
*/
{
unsigned int czero, clead, cdigits;
char exponent[10];
/* Allow up to two leading zeros - this will not lengthen
* the number compared to using E-n.
*/
if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */
{
czero = 0U-exp_b10; /* PLUS 2 digits: TOTAL 3 */
exp_b10 = 0; /* Dot added below before first output. */
}
else
czero = 0; /* No zeros to add */
/* Generate the digit list, stripping trailing zeros and
* inserting a '.' before a digit if the exponent is 0.
*/
clead = czero; /* Count of leading zeros */
cdigits = 0; /* Count of digits in list. */
do
{
double d;
fp *= 10;
/* Use modf here, not floor and subtract, so that
* the separation is done in one step. At the end
* of the loop don't break the number into parts so
* that the final digit is rounded.
*/
if (cdigits+czero+1 < precision+clead)
fp = modf(fp, &d);
else
{
d = floor(fp + .5);
if (d > 9)
{
/* Rounding up to 10, handle that here. */
if (czero > 0)
{
--czero; d = 1;
if (cdigits == 0) --clead;
}
else
{
while (cdigits > 0 && d > 9)
{
int ch = *--ascii;
if (exp_b10 != (-1))
++exp_b10;
else if (ch == 46)
{
ch = *--ascii; ++size;
/* Advance exp_b10 to '1', so that the
* decimal point happens after the
* previous digit.
*/
exp_b10 = 1;
}
--cdigits;
d = ch - 47; /* I.e. 1+(ch-48) */
}
/* Did we reach the beginning? If so adjust the
* exponent but take into account the leading
* decimal point.
*/
if (d > 9) /* cdigits == 0 */
{
if (exp_b10 == (-1))
{
/* Leading decimal point (plus zeros?), if
* we lose the decimal point here it must
* be reentered below.
*/
int ch = *--ascii;
if (ch == 46)
{
++size; exp_b10 = 1;
}
/* Else lost a leading zero, so 'exp_b10' is
* still ok at (-1)
*/
}
else
++exp_b10;
/* In all cases we output a '1' */
d = 1;
}
}
}
fp = 0; /* Guarantees termination below. */
}
if (d == 0)
{
++czero;
if (cdigits == 0) ++clead;
}
else
{
/* Included embedded zeros in the digit count. */
cdigits += czero - clead;
clead = 0;
while (czero > 0)
{
/* exp_b10 == (-1) means we just output the decimal
* place - after the DP don't adjust 'exp_b10' any
* more!
*/
if (exp_b10 != (-1))
{
if (exp_b10 == 0)
{
*ascii++ = 46; --size;
}
/* PLUS 1: TOTAL 4 */
--exp_b10;
}
*ascii++ = 48; --czero;
}
if (exp_b10 != (-1))
{
if (exp_b10 == 0)
{
*ascii++ = 46; --size; /* counted above */
}
--exp_b10;
}
*ascii++ = (char)(48 + (int)d); ++cdigits;
}
}
while (cdigits+czero < precision+clead && fp > DBL_MIN);
/* The total output count (max) is now 4+precision */
/* Check for an exponent, if we don't need one we are
* done and just need to terminate the string. At this
* point, exp_b10==(-1) is effectively a flag: it got
* to '-1' because of the decrement, after outputting
* the decimal point above. (The exponent required is
* *not* -1.)
*/
if (exp_b10 >= (-1) && exp_b10 <= 2)
{
/* The following only happens if we didn't output the
* leading zeros above for negative exponent, so this
* doesn't add to the digit requirement. Note that the
* two zeros here can only be output if the two leading
* zeros were *not* output, so this doesn't increase
* the output count.
*/
while (exp_b10-- > 0) *ascii++ = 48;
*ascii = 0;
/* Total buffer requirement (including the '\0') is
* 5+precision - see check at the start.
*/
return;
}
/* Here if an exponent is required, adjust size for
* the digits we output but did not count. The total
* digit output here so far is at most 1+precision - no
* decimal point and no leading or trailing zeros have
* been output.
*/
size -= cdigits;
*ascii++ = 69; --size; /* 'E': PLUS 1 TOTAL 2+precision */
/* The following use of an unsigned temporary avoids ambiguities in
* the signed arithmetic on exp_b10 and permits GCC at least to do
* better optimization.
*/
{
unsigned int uexp_b10;
if (exp_b10 < 0)
{
*ascii++ = 45; --size; /* '-': PLUS 1 TOTAL 3+precision */
uexp_b10 = 0U-exp_b10;
}
else
uexp_b10 = 0U+exp_b10;
cdigits = 0;
while (uexp_b10 > 0)
{
exponent[cdigits++] = (char)(48 + uexp_b10 % 10);
uexp_b10 /= 10;
}
}
/* Need another size check here for the exponent digits, so
* this need not be considered above.
*/
if (size > cdigits)
{
while (cdigits > 0) *ascii++ = exponent[--cdigits];
*ascii = 0;
return;
}
}
}
else if (!(fp >= DBL_MIN))
{
*ascii++ = 48; /* '0' */
*ascii = 0;
return;
}
else
{
*ascii++ = 105; /* 'i' */
*ascii++ = 110; /* 'n' */
*ascii++ = 102; /* 'f' */
*ascii = 0;
return;
}
}
/* Here on buffer too small. */
png_error(png_ptr, "ASCII conversion buffer too small");
}
#if GCC_STRICT_OVERFLOW
#pragma GCC diagnostic pop
#endif /* GCC_STRICT_OVERFLOW */
# endif /* FLOATING_POINT */
# ifdef PNG_FIXED_POINT_SUPPORTED
/* Function to format a fixed point value in ASCII.
*/
void /* PRIVATE */
png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
size_t size, png_fixed_point fp)
{
/* Require space for 10 decimal digits, a decimal point, a minus sign and a
* trailing \0, 13 characters:
*/
if (size > 12)
{
png_uint_32 num;
/* Avoid overflow here on the minimum integer. */
if (fp < 0)
{
*ascii++ = 45; num = (png_uint_32)(-fp);
}
else
num = (png_uint_32)fp;
if (num <= 0x80000000) /* else overflowed */
{
unsigned int ndigits = 0, first = 16 /* flag value */;
char digits[10];
while (num)
{
/* Split the low digit off num: */
unsigned int tmp = num/10;
num -= tmp*10;
digits[ndigits++] = (char)(48 + num);
/* Record the first non-zero digit, note that this is a number
* starting at 1, it's not actually the array index.
*/
if (first == 16 && num > 0)
first = ndigits;
num = tmp;
}
if (ndigits > 0)
{
while (ndigits > 5) *ascii++ = digits[--ndigits];
/* The remaining digits are fractional digits, ndigits is '5' or
* smaller at this point. It is certainly not zero. Check for a
* non-zero fractional digit:
*/
if (first <= 5)
{
unsigned int i;
*ascii++ = 46; /* decimal point */
/* ndigits may be <5 for small numbers, output leading zeros
* then ndigits digits to first:
*/
i = 5;
while (ndigits < i)
{
*ascii++ = 48; --i;
}
while (ndigits >= first) *ascii++ = digits[--ndigits];
/* Don't output the trailing zeros! */
}
}
else
*ascii++ = 48;
/* And null terminate the string: */
*ascii = 0;
return;
}
}
/* Here on buffer too small. */
png_error(png_ptr, "ASCII conversion buffer too small");
}
# endif /* FIXED_POINT */
#endif /* SCAL */
#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
!defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
(defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
(defined(PNG_sCAL_SUPPORTED) && \
defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
png_fixed_point
png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
{
double r = floor(100000 * fp + .5);
if (r > 2147483647. || r < -2147483648.)
png_fixed_error(png_ptr, text);
# ifndef PNG_ERROR_TEXT_SUPPORTED
PNG_UNUSED(text)
# endif
return (png_fixed_point)r;
}
#endif
#if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\
defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED)
/* muldiv functions */
/* This API takes signed arguments and rounds the result to the nearest
* integer (or, for a fixed point number - the standard argument - to
* the nearest .00001). Overflow and divide by zero are signalled in
* the result, a boolean - true on success, false on overflow.
*/
#if GCC_STRICT_OVERFLOW /* from above */
/* It is not obvious which comparison below gets optimized in such a way that
* signed overflow would change the result; looking through the code does not
* reveal any tests which have the form GCC complains about, so presumably the
* optimizer is moving an add or subtract into the 'if' somewhere.
*/
#pragma GCC diagnostic push
#pragma GCC diagnostic warning "-Wstrict-overflow=2"
#endif /* GCC_STRICT_OVERFLOW */
int
png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
png_int_32 divisor)
{
/* Return a * times / divisor, rounded. */
if (divisor != 0)
{
if (a == 0 || times == 0)
{
*res = 0;
return 1;
}
else
{
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
double r = a;
r *= times;
r /= divisor;
r = floor(r+.5);
/* A png_fixed_point is a 32-bit integer. */
if (r <= 2147483647. && r >= -2147483648.)
{
*res = (png_fixed_point)r;
return 1;
}
#else
int negative = 0;
png_uint_32 A, T, D;
png_uint_32 s16, s32, s00;
if (a < 0)
negative = 1, A = -a;
else
A = a;
if (times < 0)
negative = !negative, T = -times;
else
T = times;
if (divisor < 0)
negative = !negative, D = -divisor;
else
D = divisor;
/* Following can't overflow because the arguments only
* have 31 bits each, however the result may be 32 bits.
*/
s16 = (A >> 16) * (T & 0xffff) +
(A & 0xffff) * (T >> 16);
/* Can't overflow because the a*times bit is only 30
* bits at most.
*/
s32 = (A >> 16) * (T >> 16) + (s16 >> 16);
s00 = (A & 0xffff) * (T & 0xffff);
s16 = (s16 & 0xffff) << 16;
s00 += s16;
if (s00 < s16)
++s32; /* carry */
if (s32 < D) /* else overflow */
{
/* s32.s00 is now the 64-bit product, do a standard
* division, we know that s32 < D, so the maximum
* required shift is 31.
*/
int bitshift = 32;
png_fixed_point result = 0; /* NOTE: signed */
while (--bitshift >= 0)
{
png_uint_32 d32, d00;
if (bitshift > 0)
d32 = D >> (32-bitshift), d00 = D << bitshift;
else
d32 = 0, d00 = D;
if (s32 > d32)
{
if (s00 < d00) --s32; /* carry */
s32 -= d32, s00 -= d00, result += 1<<bitshift;
}
else
if (s32 == d32 && s00 >= d00)
s32 = 0, s00 -= d00, result += 1<<bitshift;
}
/* Handle the rounding. */
if (s00 >= (D >> 1))
++result;
if (negative != 0)
result = -result;
/* Check for overflow. */
if ((negative != 0 && result <= 0) ||
(negative == 0 && result >= 0))
{
*res = result;
return 1;
}
}
#endif
}
}
return 0;
}
#if GCC_STRICT_OVERFLOW
#pragma GCC diagnostic pop
#endif /* GCC_STRICT_OVERFLOW */
#endif /* READ_GAMMA || INCH_CONVERSIONS */
#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
/* The following is for when the caller doesn't much care about the
* result.
*/
png_fixed_point
png_muldiv_warn(png_const_structrp png_ptr, png_fixed_point a, png_int_32 times,
png_int_32 divisor)
{
png_fixed_point result;
if (png_muldiv(&result, a, times, divisor) != 0)
return result;
png_warning(png_ptr, "fixed point overflow ignored");
return 0;
}
#endif
#ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */
/* Calculate a reciprocal, return 0 on div-by-zero or overflow. */
png_fixed_point
png_reciprocal(png_fixed_point a)
{
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
double r = floor(1E10/a+.5);
if (r <= 2147483647. && r >= -2147483648.)
return (png_fixed_point)r;
#else
png_fixed_point res;
if (png_muldiv(&res, 100000, 100000, a) != 0)
return res;
#endif
return 0; /* error/overflow */
}
/* This is the shared test on whether a gamma value is 'significant' - whether
* it is worth doing gamma correction.
*/
int /* PRIVATE */
png_gamma_significant(png_fixed_point gamma_val)
{
return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED ||
gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED;
}
#endif
#ifdef PNG_READ_GAMMA_SUPPORTED
#ifdef PNG_16BIT_SUPPORTED
/* A local convenience routine. */
static png_fixed_point
png_product2(png_fixed_point a, png_fixed_point b)
{
/* The required result is 1/a * 1/b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
double r = a * 1E-5;
r *= b;
r = floor(r+.5);
if (r <= 2147483647. && r >= -2147483648.)
return (png_fixed_point)r;
#else
png_fixed_point res;
if (png_muldiv(&res, a, b, 100000) != 0)
return res;
#endif
return 0; /* overflow */
}
#endif /* 16BIT */
/* The inverse of the above. */
png_fixed_point
png_reciprocal2(png_fixed_point a, png_fixed_point b)
{
/* The required result is 1/a * 1/b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
if (a != 0 && b != 0)
{
double r = 1E15/a;
r /= b;
r = floor(r+.5);
if (r <= 2147483647. && r >= -2147483648.)
return (png_fixed_point)r;
}
#else
/* This may overflow because the range of png_fixed_point isn't symmetric,
* but this API is only used for the product of file and screen gamma so it
* doesn't matter that the smallest number it can produce is 1/21474, not
* 1/100000
*/
png_fixed_point res = png_product2(a, b);
if (res != 0)
return png_reciprocal(res);
#endif
return 0; /* overflow */
}
#endif /* READ_GAMMA */
#ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */
#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* Fixed point gamma.
*
* The code to calculate the tables used below can be found in the shell script
* contrib/tools/intgamma.sh
*
* To calculate gamma this code implements fast log() and exp() calls using only
* fixed point arithmetic. This code has sufficient precision for either 8-bit
* or 16-bit sample values.
*
* The tables used here were calculated using simple 'bc' programs, but C double
* precision floating point arithmetic would work fine.
*
* 8-bit log table
* This is a table of -log(value/255)/log(2) for 'value' in the range 128 to
* 255, so it's the base 2 logarithm of a normalized 8-bit floating point
* mantissa. The numbers are 32-bit fractions.
*/
static const png_uint_32
png_8bit_l2[128] =
{
4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U,
3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U,
3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U,
3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U,
3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U,
2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U,
2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U,
2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U,
2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U,
2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U,
1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U,
1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U,
1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U,
1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U,
1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U,
971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U,
803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U,
639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U,
479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U,
324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U,
172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U,
24347096U, 0U
#if 0
/* The following are the values for 16-bit tables - these work fine for the
* 8-bit conversions but produce very slightly larger errors in the 16-bit
* log (about 1.2 as opposed to 0.7 absolute error in the final value). To
* use these all the shifts below must be adjusted appropriately.
*/
65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054,
57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803,
50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068,
43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782,
37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887,
31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339,
25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098,
20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132,
15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415,
10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523,
6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495,
1119, 744, 372
#endif
};
static png_int_32
png_log8bit(unsigned int x)
{
unsigned int lg2 = 0;
/* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log,
* because the log is actually negate that means adding 1. The final
* returned value thus has the range 0 (for 255 input) to 7.994 (for 1
* input), return -1 for the overflow (log 0) case, - so the result is
* always at most 19 bits.
*/
if ((x &= 0xff) == 0)
return -1;
if ((x & 0xf0) == 0)
lg2 = 4, x <<= 4;
if ((x & 0xc0) == 0)
lg2 += 2, x <<= 2;
if ((x & 0x80) == 0)
lg2 += 1, x <<= 1;
/* result is at most 19 bits, so this cast is safe: */
return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16));
}
/* The above gives exact (to 16 binary places) log2 values for 8-bit images,
* for 16-bit images we use the most significant 8 bits of the 16-bit value to
* get an approximation then multiply the approximation by a correction factor
* determined by the remaining up to 8 bits. This requires an additional step
* in the 16-bit case.
*
* We want log2(value/65535), we have log2(v'/255), where:
*
* value = v' * 256 + v''
* = v' * f
*
* So f is value/v', which is equal to (256+v''/v') since v' is in the range 128
* to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less
* than 258. The final factor also needs to correct for the fact that our 8-bit
* value is scaled by 255, whereas the 16-bit values must be scaled by 65535.
*
* This gives a final formula using a calculated value 'x' which is value/v' and
* scaling by 65536 to match the above table:
*
* log2(x/257) * 65536
*
* Since these numbers are so close to '1' we can use simple linear
* interpolation between the two end values 256/257 (result -368.61) and 258/257
* (result 367.179). The values used below are scaled by a further 64 to give
* 16-bit precision in the interpolation:
*
* Start (256): -23591
* Zero (257): 0
* End (258): 23499
*/
#ifdef PNG_16BIT_SUPPORTED
static png_int_32
png_log16bit(png_uint_32 x)
{
unsigned int lg2 = 0;
/* As above, but now the input has 16 bits. */
if ((x &= 0xffff) == 0)
return -1;
if ((x & 0xff00) == 0)
lg2 = 8, x <<= 8;
if ((x & 0xf000) == 0)
lg2 += 4, x <<= 4;
if ((x & 0xc000) == 0)
lg2 += 2, x <<= 2;
if ((x & 0x8000) == 0)
lg2 += 1, x <<= 1;
/* Calculate the base logarithm from the top 8 bits as a 28-bit fractional
* value.
*/
lg2 <<= 28;
lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4;
/* Now we need to interpolate the factor, this requires a division by the top
* 8 bits. Do this with maximum precision.
*/
x = ((x << 16) + (x >> 9)) / (x >> 8);
/* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24,
* the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly
* 16 bits to interpolate to get the low bits of the result. Round the
* answer. Note that the end point values are scaled by 64 to retain overall
* precision and that 'lg2' is current scaled by an extra 12 bits, so adjust
* the overall scaling by 6-12. Round at every step.
*/
x -= 1U << 24;
if (x <= 65536U) /* <= '257' */
lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12);
else
lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12);
/* Safe, because the result can't have more than 20 bits: */
return (png_int_32)((lg2 + 2048) >> 12);
}
#endif /* 16BIT */
/* The 'exp()' case must invert the above, taking a 20-bit fixed point
* logarithmic value and returning a 16 or 8-bit number as appropriate. In
* each case only the low 16 bits are relevant - the fraction - since the
* integer bits (the top 4) simply determine a shift.
*
* The worst case is the 16-bit distinction between 65535 and 65534. This
* requires perhaps spurious accuracy in the decoding of the logarithm to
* distinguish log2(65535/65534.5) - 10^-5 or 17 bits. There is little chance
* of getting this accuracy in practice.
*
* To deal with this the following exp() function works out the exponent of the
* fractional part of the logarithm by using an accurate 32-bit value from the
* top four fractional bits then multiplying in the remaining bits.
*/
static const png_uint_32
png_32bit_exp[16] =
{
/* NOTE: the first entry is deliberately set to the maximum 32-bit value. */
4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U,
3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U,
2553802834U, 2445529972U, 2341847524U, 2242560872U
};
/* Adjustment table; provided to explain the numbers in the code below. */
#if 0
for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"}
11 44937.64284865548751208448
10 45180.98734845585101160448
9 45303.31936980687359311872
8 45364.65110595323018870784
7 45395.35850361789624614912
6 45410.72259715102037508096
5 45418.40724413220722311168
4 45422.25021786898173001728
3 45424.17186732298419044352
2 45425.13273269940811464704
1 45425.61317555035558641664
0 45425.85339951654943850496
#endif
static png_uint_32
png_exp(png_fixed_point x)
{
if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */
{
/* Obtain a 4-bit approximation */
png_uint_32 e = png_32bit_exp[(x >> 12) & 0x0f];
/* Incorporate the low 12 bits - these decrease the returned value by
* multiplying by a number less than 1 if the bit is set. The multiplier
* is determined by the above table and the shift. Notice that the values
* converge on 45426 and this is used to allow linear interpolation of the
* low bits.
*/
if (x & 0x800)
e -= (((e >> 16) * 44938U) + 16U) >> 5;
if (x & 0x400)
e -= (((e >> 16) * 45181U) + 32U) >> 6;
if (x & 0x200)
e -= (((e >> 16) * 45303U) + 64U) >> 7;
if (x & 0x100)
e -= (((e >> 16) * 45365U) + 128U) >> 8;
if (x & 0x080)
e -= (((e >> 16) * 45395U) + 256U) >> 9;
if (x & 0x040)
e -= (((e >> 16) * 45410U) + 512U) >> 10;
/* And handle the low 6 bits in a single block. */
e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9;
/* Handle the upper bits of x. */
e >>= x >> 16;
return e;
}
/* Check for overflow */
if (x <= 0)
return png_32bit_exp[0];
/* Else underflow */
return 0;
}
static png_byte
png_exp8bit(png_fixed_point lg2)
{
/* Get a 32-bit value: */
png_uint_32 x = png_exp(lg2);
/* Convert the 32-bit value to 0..255 by multiplying by 256-1. Note that the
* second, rounding, step can't overflow because of the first, subtraction,
* step.
*/
x -= x >> 8;
return (png_byte)(((x + 0x7fffffU) >> 24) & 0xff);
}
#ifdef PNG_16BIT_SUPPORTED
static png_uint_16
png_exp16bit(png_fixed_point lg2)
{
/* Get a 32-bit value: */
png_uint_32 x = png_exp(lg2);
/* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */
x -= x >> 16;
return (png_uint_16)((x + 32767U) >> 16);
}
#endif /* 16BIT */
#endif /* FLOATING_ARITHMETIC */
png_byte
png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val)
{
if (value > 0 && value < 255)
{
# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* 'value' is unsigned, ANSI-C90 requires the compiler to correctly
* convert this to a floating point value. This includes values that
* would overflow if 'value' were to be converted to 'int'.
*
* Apparently GCC, however, does an intermediate conversion to (int)
* on some (ARM) but not all (x86) platforms, possibly because of
* hardware FP limitations. (E.g. if the hardware conversion always
* assumes the integer register contains a signed value.) This results
* in ANSI-C undefined behavior for large values.
*
* Other implementations on the same machine might actually be ANSI-C90
* conformant and therefore compile spurious extra code for the large
* values.
*
* We can be reasonably sure that an unsigned to float conversion
* won't be faster than an int to float one. Therefore this code
* assumes responsibility for the undefined behavior, which it knows
* can't happen because of the check above.
*
* Note the argument to this routine is an (unsigned int) because, on
* 16-bit platforms, it is assigned a value which might be out of
* range for an (int); that would result in undefined behavior in the
* caller if the *argument* ('value') were to be declared (int).
*/
double r = floor(255*pow((int)/*SAFE*/value/255.,gamma_val*.00001)+.5);
return (png_byte)r;
# else
png_int_32 lg2 = png_log8bit(value);
png_fixed_point res;
if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0)
return png_exp8bit(res);
/* Overflow. */
value = 0;
# endif
}
return (png_byte)(value & 0xff);
}
#ifdef PNG_16BIT_SUPPORTED
png_uint_16
png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val)
{
if (value > 0 && value < 65535)
{
# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* The same (unsigned int)->(double) constraints apply here as above,
* however in this case the (unsigned int) to (int) conversion can
* overflow on an ANSI-C90 compliant system so the cast needs to ensure
* that this is not possible.
*/
double r = floor(65535*pow((png_int_32)value/65535.,
gamma_val*.00001)+.5);
return (png_uint_16)r;
# else
png_int_32 lg2 = png_log16bit(value);
png_fixed_point res;
if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0)
return png_exp16bit(res);
/* Overflow. */
value = 0;
# endif
}
return (png_uint_16)value;
}
#endif /* 16BIT */
/* This does the right thing based on the bit_depth field of the
* png_struct, interpreting values as 8-bit or 16-bit. While the result
* is nominally a 16-bit value if bit depth is 8 then the result is
* 8-bit (as are the arguments.)
*/
png_uint_16 /* PRIVATE */
png_gamma_correct(png_structrp png_ptr, unsigned int value,
png_fixed_point gamma_val)
{
if (png_ptr->bit_depth == 8)
return png_gamma_8bit_correct(value, gamma_val);
#ifdef PNG_16BIT_SUPPORTED
else
return png_gamma_16bit_correct(value, gamma_val);
#else
/* should not reach this */
return 0;
#endif /* 16BIT */
}
#ifdef PNG_16BIT_SUPPORTED
/* Internal function to build a single 16-bit table - the table consists of
* 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount
* to shift the input values right (or 16-number_of_signifiant_bits).
*
* The caller is responsible for ensuring that the table gets cleaned up on
* png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument
* should be somewhere that will be cleaned.
*/
static void
png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable,
unsigned int shift, png_fixed_point gamma_val)
{
/* Various values derived from 'shift': */
unsigned int num = 1U << (8U - shift);
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* CSE the division and work round wacky GCC warnings (see the comments
* in png_gamma_8bit_correct for where these come from.)
*/
double fmax = 1.0 / (((png_int_32)1 << (16U - shift)) - 1);
#endif
unsigned int max = (1U << (16U - shift)) - 1U;
unsigned int max_by_2 = 1U << (15U - shift);
unsigned int i;
png_uint_16pp table = *ptable =
(png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
for (i = 0; i < num; i++)
{
png_uint_16p sub_table = table[i] =
(png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16)));
/* The 'threshold' test is repeated here because it can arise for one of
* the 16-bit tables even if the others don't hit it.
*/
if (png_gamma_significant(gamma_val) != 0)
{
/* The old code would overflow at the end and this would cause the
* 'pow' function to return a result >1, resulting in an
* arithmetic error. This code follows the spec exactly; ig is
* the recovered input sample, it always has 8-16 bits.
*
* We want input * 65535/max, rounded, the arithmetic fits in 32
* bits (unsigned) so long as max <= 32767.
*/
unsigned int j;
for (j = 0; j < 256; j++)
{
png_uint_32 ig = (j << (8-shift)) + i;
# ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* Inline the 'max' scaling operation: */
/* See png_gamma_8bit_correct for why the cast to (int) is
* required here.
*/
double d = floor(65535.*pow(ig*fmax, gamma_val*.00001)+.5);
sub_table[j] = (png_uint_16)d;
# else
if (shift != 0)
ig = (ig * 65535U + max_by_2)/max;
sub_table[j] = png_gamma_16bit_correct(ig, gamma_val);
# endif
}
}
else
{
/* We must still build a table, but do it the fast way. */
unsigned int j;
for (j = 0; j < 256; j++)
{
png_uint_32 ig = (j << (8-shift)) + i;
if (shift != 0)
ig = (ig * 65535U + max_by_2)/max;
sub_table[j] = (png_uint_16)ig;
}
}
}
}
/* NOTE: this function expects the *inverse* of the overall gamma transformation
* required.
*/
static void
png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable,
unsigned int shift, png_fixed_point gamma_val)
{
unsigned int num = 1U << (8U - shift);
unsigned int max = (1U << (16U - shift))-1U;
unsigned int i;
png_uint_32 last;
png_uint_16pp table = *ptable =
(png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p)));
/* 'num' is the number of tables and also the number of low bits of low
* bits of the input 16-bit value used to select a table. Each table is
* itself indexed by the high 8 bits of the value.
*/
for (i = 0; i < num; i++)
table[i] = (png_uint_16p)png_malloc(png_ptr,
256 * (sizeof (png_uint_16)));
/* 'gamma_val' is set to the reciprocal of the value calculated above, so
* pow(out,g) is an *input* value. 'last' is the last input value set.
*
* In the loop 'i' is used to find output values. Since the output is
* 8-bit there are only 256 possible values. The tables are set up to
* select the closest possible output value for each input by finding
* the input value at the boundary between each pair of output values
* and filling the table up to that boundary with the lower output
* value.
*
* The boundary values are 0.5,1.5..253.5,254.5. Since these are 9-bit
* values the code below uses a 16-bit value in i; the values start at
* 128.5 (for 0.5) and step by 257, for a total of 254 values (the last
* entries are filled with 255). Start i at 128 and fill all 'last'
* table entries <= 'max'
*/
last = 0;
for (i = 0; i < 255; ++i) /* 8-bit output value */
{
/* Find the corresponding maximum input value */
png_uint_16 out = (png_uint_16)(i * 257U); /* 16-bit output value */
/* Find the boundary value in 16 bits: */
png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val);
/* Adjust (round) to (16-shift) bits: */
bound = (bound * max + 32768U)/65535U + 1U;
while (last < bound)
{
table[last & (0xffU >> shift)][last >> (8U - shift)] = out;
last++;
}
}
/* And fill in the final entries. */
while (last < (num << 8))
{
table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U;
last++;
}
}
#endif /* 16BIT */
/* Build a single 8-bit table: same as the 16-bit case but much simpler (and
* typically much faster). Note that libpng currently does no sBIT processing
* (apparently contrary to the spec) so a 256-entry table is always generated.
*/
static void
png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
png_fixed_point gamma_val)
{
unsigned int i;
png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256);
if (png_gamma_significant(gamma_val) != 0)
for (i=0; i<256; i++)
table[i] = png_gamma_8bit_correct(i, gamma_val);
else
for (i=0; i<256; ++i)
table[i] = (png_byte)(i & 0xff);
}
/* Used from png_read_destroy and below to release the memory used by the gamma
* tables.
*/
void /* PRIVATE */
png_destroy_gamma_table(png_structrp png_ptr)
{
png_free(png_ptr, png_ptr->gamma_table);
png_ptr->gamma_table = NULL;
#ifdef PNG_16BIT_SUPPORTED
if (png_ptr->gamma_16_table != NULL)
{
int i;
int istop = (1 << (8 - png_ptr->gamma_shift));
for (i = 0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_table[i]);
}
png_free(png_ptr, png_ptr->gamma_16_table);
png_ptr->gamma_16_table = NULL;
}
#endif /* 16BIT */
#if defined(PNG_READ_BACKGROUND_SUPPORTED) || \
defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \
defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
png_free(png_ptr, png_ptr->gamma_from_1);
png_ptr->gamma_from_1 = NULL;
png_free(png_ptr, png_ptr->gamma_to_1);
png_ptr->gamma_to_1 = NULL;
#ifdef PNG_16BIT_SUPPORTED
if (png_ptr->gamma_16_from_1 != NULL)
{
int i;
int istop = (1 << (8 - png_ptr->gamma_shift));
for (i = 0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_from_1[i]);
}
png_free(png_ptr, png_ptr->gamma_16_from_1);
png_ptr->gamma_16_from_1 = NULL;
}
if (png_ptr->gamma_16_to_1 != NULL)
{
int i;
int istop = (1 << (8 - png_ptr->gamma_shift));
for (i = 0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_to_1[i]);
}
png_free(png_ptr, png_ptr->gamma_16_to_1);
png_ptr->gamma_16_to_1 = NULL;
}
#endif /* 16BIT */
#endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
}
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