/* png.c - location for general purpose libpng functions * * Copyright (c) 2018-2025 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_45 Your_png_h_is_not_version_1_6_45;
/* 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)
{ unsignedint nb = (unsignedint)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)
{ staticconst png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10};
/* 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;
}
/* '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);
}
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)
/* Generic function to create a png_struct for either read or write - this * contains the common initialization.
*/
PNG_FUNCTION(png_structp /* PRIVATE */,
png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
{
png_struct create_struct; # ifdef PNG_SETJMP_SUPPORTED
jmp_buf create_jmp_buf; # endif
/* This temporary stack-allocated structure is used to provide a place to * build enough context to allow the user provided memory allocator (if any) * to be called.
*/
memset(&create_struct, 0, (sizeof create_struct));
# ifdef PNG_USER_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;
/* 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;
/* Initialize the info structure. This is now an internal function (0.89) * and applications using it are urged to use png_create_info_struct() * instead. Use deprecated in 1.6.0, internal use removed (used internally it * is just a memset). * * NOTE: it is almost inconceivable that this API is used because it bypasses * the user-memory mechanism and the user error handling/warning mechanisms in * those cases where it does anything other than a memset.
*/
PNG_FUNCTION(void,PNGAPI
png_info_init_3,(png_infopp ptr_ptr, size_t png_info_struct_size),
PNG_DEPRECATED)
{
png_inforp info_ptr = *ptr_ptr;
png_debug(1, "in png_info_init_3");
if (info_ptr == NULL) return;
if ((sizeof (png_info)) > png_info_struct_size)
{
*ptr_ptr = NULL; /* The following line is why this API should not be used: */
free(info_ptr);
info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL,
(sizeof *info_ptr))); if (info_ptr == NULL) return;
*ptr_ptr = info_ptr;
}
/* Set everything to 0 */
memset(info_ptr, 0, (sizeof *info_ptr));
}
void PNGAPI
png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr, int freer, png_uint_32 mask)
{
png_debug(1, "in png_data_freer");
if (png_ptr == NULL || info_ptr == NULL) return;
if (freer == PNG_DESTROY_WILL_FREE_DATA)
info_ptr->free_me |= mask;
else
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);
#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);
}
/* 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;
}
#ifdefined(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 * corresponding to the 2's complement representation.
*/ void PNGAPI
png_save_int_32(png_bytep buf, png_int_32 i)
{
png_save_uint_32(buf, (png_uint_32)i);
} # endif
# ifdef PNG_TIME_RFC1123_SUPPORTED /* Convert the supplied time into an RFC 1123 string suitable for use in * a "Creation Time" or other text-based time string.
*/ int PNGAPI
png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime)
{ staticconstchar short_months[12][4] =
{"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
# 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");
/* 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");
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;
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;
}
#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;
}
#ifdefined(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 */ staticint
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;
}
}
return1;
}
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 */ elseif ((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 */ elseif ((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);
}
# 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;
#ifdef PNG_COLORSPACE_SUPPORTED static png_int_32
png_fp_add(png_int_32 addend0, png_int_32 addend1, int *error)
{ /* Safely add two fixed point values setting an error flag and returning 0.5 * on overflow. * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore * relying on addition of two positive values producing a negative one is not * safe.
*/ if (addend0 > 0)
{ if (0x7fffffff - addend0 >= addend1) return addend0+addend1;
} elseif (addend0 < 0)
{ if (-0x7fffffff - addend0 <= addend1) return addend0+addend1;
} else return addend1;
*error = 1; return PNG_FP_1/2;
}
static png_int_32
png_fp_sub(png_int_32 addend0, png_int_32 addend1, int *error)
{ /* As above but calculate addend0-addend1. */ if (addend1 > 0)
{ if (-0x7fffffff + addend1 <= addend0) return addend0-addend1;
} elseif (addend1 < 0)
{ if (0x7fffffff + addend1 >= addend0) return addend0-addend1;
} else return addend0;
*error = 1; return PNG_FP_1/2;
}
staticint
png_safe_add(png_int_32 *addend0_and_result, png_int_32 addend1,
png_int_32 addend2)
{ /* Safely add three integers. Returns 0 on success, 1 on overflow. Does not * set the result on overflow.
*/ int error = 0; int result = png_fp_add(*addend0_and_result,
png_fp_add(addend1, addend2, &error),
&error); if (!error) *addend0_and_result = result; return error;
}
/* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for * cHRM, as opposed to using chromaticities. These internal APIs return * non-zero on a parameter error. The X, Y and Z values are required to be * positive and less than 1.0.
*/ staticint
png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ)
{
png_int_32 d, dred, dgreen, dblue, dwhite, whiteX, whiteY;
/* 'd' in each of the blocks below is just X+Y+Z for each component, * x, y and z are X,Y,Z/(X+Y+Z).
*/
d = XYZ->red_X; if (png_safe_add(&d, XYZ->red_Y, XYZ->red_Z)) return1;
dred = d; if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, dred) == 0) return1; if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, dred) == 0) return1;
d = XYZ->green_X; if (png_safe_add(&d, XYZ->green_Y, XYZ->green_Z)) return1;
dgreen = d; if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, dgreen) == 0) return1; if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, dgreen) == 0) return1;
d = XYZ->blue_X; if (png_safe_add(&d, XYZ->blue_Y, XYZ->blue_Z)) return1;
dblue = d; if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, dblue) == 0) return1; if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, dblue) == 0) return1;
/* The reference white is simply the sum of the end-point (X,Y,Z) vectors so * the fillowing calculates (X+Y+Z) of the reference white (media white, * encoding white) itself:
*/
d = dblue; if (png_safe_add(&d, dred, dgreen)) return1;
dwhite = d;
/* Find the white X,Y values from the sum of the red, green and blue X,Y * values.
*/
d = XYZ->red_X; if (png_safe_add(&d, XYZ->green_X, XYZ->blue_X)) return1;
whiteX = d;
d = XYZ->red_Y; if (png_safe_add(&d, XYZ->green_Y, XYZ->blue_Y)) return1;
whiteY = d;
if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) == 0) return1; if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0) return1;
/* Check xy and, implicitly, z. Note that wide gamut color spaces typically * have end points with 0 tristimulus values (these are impossible end * points, but they are used to cover the possible colors). We check * xy->whitey against 5, not 0, to avoid a possible integer overflow. * * The limits here will *not* accept ACES AP0, where bluey is -7700 * (-0.0770) because the PNG spec itself requires the xy values to be * unsigned. whitey is also required to be 5 or more to avoid overflow. * * Instead the upper limits have been relaxed to accomodate ACES AP1 where * redz ends up as -600 (-0.006). ProPhotoRGB was already "in range." * The new limit accomodates the AP0 and AP1 ranges for z but not AP0 redy.
*/ const png_fixed_point fpLimit = PNG_FP_1+(PNG_FP_1/10); if (xy->redx < 0 || xy->redx > fpLimit) return1; if (xy->redy < 0 || xy->redy > fpLimit-xy->redx) return1; if (xy->greenx < 0 || xy->greenx > fpLimit) return1; if (xy->greeny < 0 || xy->greeny > fpLimit-xy->greenx) return1; if (xy->bluex < 0 || xy->bluex > fpLimit) return1; if (xy->bluey < 0 || xy->bluey > fpLimit-xy->bluex) return1; if (xy->whitex < 0 || xy->whitex > fpLimit) return1; if (xy->whitey < 5 || xy->whitey > fpLimit-xy->whitex) return1;
/* 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. * * In the previous implementation the values were all in the range 0 < value * < 1, so simple products are in the same range but may need up to 10 * decimal digits to preserve the original precision and avoid underflow. * Because we are using a 32-bit signed representation we cannot match this; * the best is a little over 9 decimal digits, less than 10. * * This range has now been extended to allow values up to 1.1, or 110,000 in * fixed point. * * The approach used here is to preserve the maximum precision within the * signed representation. Because the red-scale calculation above uses the * difference between two products of values that must be in the range * -1.1..+1.1 it is sufficient to divide the product by 8; * ceil(121,000/32767*2). The factor is irrelevant in the calculation * because it is applied to both numerator and denominator. * * Note that the values of the differences of the products of the * chromaticities in the above equations tend to be small, for example for * the sRGB chromaticities they are: * * red numerator: -0.04751 * green numerator: -0.08788 * denominator: -0.2241 (without white-y multiplication) * * The resultant Y coefficients from the chromaticities of some widely used * color space definitions are (to 15 decimal places): * * sRGB * 0.212639005871510 0.715168678767756 0.072192315360734 * Kodak ProPhoto * 0.288071128229293 0.711843217810102 0.000085653960605 * Adobe RGB * 0.297344975250536 0.627363566255466 0.075291458493998 * Adobe Wide Gamut RGB * 0.258728243040113 0.724682314948566 0.016589442011321
*/ int error = 0;
/* By the argument above overflow should be impossible here, however the * code now simply returns a failure code. The xy subtracts in the arguments * to png_muldiv are *not* checked for overflow because the checks at the * start guarantee they are in the range 0..110000 and png_fixed_point is a * 32-bit signed number.
*/ if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 8) == 0) return1; if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 8) == 0) return1;
denominator = png_fp_sub(left, right, &error); if (error) return1;
/* Now find the red numerator. */ if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 8) == 0) return1; if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 8) == 0) return1;
/* Overflow is possible here and it indicates an extreme set of PNG cHRM * chunk values. This calculation actually returns the reciprocal of the * scale value because this allows us to delay the multiplication of white-y * into the denominator, which tends to produce a small number.
*/ if (png_muldiv(&red_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) == 0 || error ||
red_inverse <= xy->whitey /* r+g+b scales = white scale */) return1;
/* Similarly for green_inverse: */ if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 8) == 0) return1; if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 8) == 0) return1; if (png_muldiv(&green_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) == 0 || error ||
green_inverse <= xy->whitey) return1;
/* And the blue scale, the checks above guarantee this can't overflow but it * can still produce 0 for extreme cHRM values.
*/
blue_scale = png_fp_sub(png_fp_sub(png_reciprocal(xy->whitey),
png_reciprocal(red_inverse), &error),
png_reciprocal(green_inverse), &error); if (error || blue_scale <= 0) return1;
/* And fill in the png_XYZ. Again the subtracts are safe because of the * checks on the xy values at the start (the subtracts just calculate the * corresponding z values.)
*/ if (png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse) == 0) return1; if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) == 0) return1; if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1,
red_inverse) == 0) return1;
if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) == 0) return1; if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) == 0) return1; if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1,
green_inverse) == 0) return1;
if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) == 0) return1; if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0) return1; if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale,
PNG_FP_1) == 0) return1;
return0; /*success*/
}
staticint
png_XYZ_normalize(png_XYZ *XYZ)
{
png_int_32 Y, Ytemp;
/* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1. */
Ytemp = XYZ->red_Y; if (png_safe_add(&Ytemp, XYZ->green_Y, XYZ->blue_Y)) return1;
Y = Ytemp;
if (Y != PNG_FP_1)
{ if (png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y) == 0) return1; if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0) return1; if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0) return1;
if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0) return1; if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0) return1; if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0) return1;
if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0) return1; if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0) return1; if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0) return1;
}
return0;
}
staticint
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)) return0; return1;
}
/* 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.
*/ staticint
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) return0;
/* Too much slip */ return1;
}
/* This is the check going the other way. The XYZ is modified to normalize it * (another side-effect) and the xy chromaticities are returned.
*/ staticint
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;
/* Used to check for an endpoint match against sRGB */ staticconst 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
};
/* 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"); return0; /* failed */
}
/* Only overwrite with preferred values */ if (preferred == 0) return1; /* ok, but no change */
}
/* 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;
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;
case1: /* 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");
}
/* 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);
return0;
} #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.)
*/ staticconst 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) return0;
/* 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_FROM_sRGB) != 0)
{
png_benign_error(png_ptr, "duplicate sRGB information ignored"); return0;
}
/* 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;
/* Finally record that we have an sRGB profile */
colorspace->flags |=
(PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB);
return1; /* 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)
*/ staticconst png_byte D50_nCIEXYZ[12] =
{ 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d };
/* 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 elseif (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 elseif (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. */ elseif (PNG_SIZE_MAX < profile_length) return png_icc_profile_error(png_ptr, colorspace, name, profile_length, "exceeds system limits"); # endif /* !SET_USER_LIMITS */
return1;
} #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_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)
{ case0x52474220: /* '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;
case0x47524159: /* '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;
/* 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)
{ case0x73636e72: /* 'scnr' */ case0x6d6e7472: /* 'mntr' */ case0x70727472: /* 'prtr' */ case0x73706163: /* 'spac' */ /* All supported */ break;
case0x61627374: /* 'abst' */ /* May not be embedded in an image */ return png_icc_profile_error(png_ptr, colorspace, name, temp, "invalid embedded Abstract ICC profile");
case0x6c696e6b: /* '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");
case0x6e6d636c: /* '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)
{ case0x58595a20: /* 'XYZ ' */ case0x4c616220: /* 'Lab ' */ break;
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");
}
}
return1; /* success, maybe with warnings */
}
#ifdef PNG_sRGB_SUPPORTED #if PNG_sRGB_PROFILE_CHECKS >= 0 /* Information about the known ICC sRGB profiles */ staticconststruct
{
png_uint_32 adler, crc, length;
png_uint_32 md5[4];
png_byte have_md5;
png_byte is_broken;
png_uint_16 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")
/* 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")
staticint
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 unsignedint 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) return0; #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) return1+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.
*/ elseif (png_sRGB_checks[i].have_md5 == 0)
{
png_chunk_report(png_ptr, "out-of-date sRGB profile with no signature",
PNG_CHUNK_WARNING);
}
return1+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
}
}
}
return0; /* 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 */
#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;
/* 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 */
void/* PRIVATE */
png_check_IHDR(png_const_structrp png_ptr,
png_uint_32 width, png_uint_32 height, int bit_depth, int color_type, int interlace_type, int compression_type, int filter_type)
{ int error = 0;
/* Check for width and height valid values */ if (width == 0)
{
png_warning(png_ptr, "Image width is zero in IHDR");
error = 1;
}
if (width > PNG_UINT_31_MAX)
{
png_warning(png_ptr, "Invalid image width in IHDR");
error = 1;
}
/* The bit mask on the first line below must be at least as big as a * png_uint_32. "~7U" is not adequate on 16-bit systems because it will * be an unsigned 16-bit value. Casting to (png_alloc_size_t) makes the * type of the result at least as bit (in bits) as the RHS of the > operator * which also avoids a common warning on 64-bit systems that the comparison * of (png_uint_32) against the constant value on the RHS will always be * false.
*/ if (((width + 7) & ~(png_alloc_size_t)7) >
(((PNG_SIZE_MAX
- 48/* big_row_buf hack */
- 1) /* filter byte */
/ 8) /* 8-byte RGBA pixels */
- 1)) /* extra max_pixel_depth pad */
{ /* The size of the row must be within the limits of this architecture. * Because the read code can perform arbitrary transformations the * maximum size is checked here. Because the code in png_read_start_row * adds extra space "for safety's sake" in several places a conservative * limit is used here. * * NOTE: it would be far better to check the size that is actually used, * but the effect in the real world is minor and the changes are more * extensive, therefore much more dangerous and much more difficult to * write in a way that avoids compiler warnings.
*/
png_warning(png_ptr, "Image width is too large for this architecture");
error = 1;
}
#ifdef PNG_SET_USER_LIMITS_SUPPORTED if (width > png_ptr->user_width_max) #else if (width > PNG_USER_WIDTH_MAX) #endif
{
png_warning(png_ptr, "Image width exceeds user limit in IHDR");
error = 1;
}
if (height == 0)
{
png_warning(png_ptr, "Image height is zero in IHDR");
error = 1;
}
if (height > PNG_UINT_31_MAX)
{
png_warning(png_ptr, "Invalid image height in IHDR");
error = 1;
}
#ifdef PNG_SET_USER_LIMITS_SUPPORTED if (height > png_ptr->user_height_max) #else if (height > PNG_USER_HEIGHT_MAX) #endif
{
png_warning(png_ptr, "Image height exceeds user limit in IHDR");
error = 1;
}
/* Check other values */ if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 &&
bit_depth != 8 && bit_depth != 16)
{
png_warning(png_ptr, "Invalid bit depth in IHDR");
error = 1;
}
if (color_type < 0 || color_type == 1 ||
color_type == 5 || color_type > 6)
{
png_warning(png_ptr, "Invalid color type in IHDR");
error = 1;
}
if (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 ((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");
}
#ifdefined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED) /* ASCII to fp functions */ /* Check an ASCII formatted floating point value, see the more detailed * comments in pngpriv.h
*/ /* The following is used internally to preserve the sticky flags */ #define png_fp_add(state, flags) ((state) |= (flags)) #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY))
int/* PRIVATE */
png_check_fp_number(png_const_charp string, size_t size, int *statep,
size_t *whereami)
{ int state = *statep;
size_t i = *whereami;
while (i < size)
{ int type; /* First find the type of the next character */ switch (string[i])
{ case43: type = PNG_FP_SAW_SIGN; break; case45: type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break; case46: type = PNG_FP_SAW_DOT; break; case48: type = PNG_FP_SAW_DIGIT; break; case49: case50: case51: case52: case53: case54: case55: case56: case57: type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break; case69: case101: 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;
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 */;
#ifdef PNG_sCAL_SUPPORTED # ifdef PNG_FLOATING_POINT_SUPPORTED /* Utility used below - a simple accurate power of ten from an integral * exponent.
*/ staticdouble
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) return0;
recip = 1; power = -power;
}
if (power > 0)
{ /* Decompose power bitwise. */ double mult = 10; do
{ if (power & 1) d *= mult;
mult *= mult;
power >>= 1;
} while (power > 0);
if (recip != 0) d = 1/d;
} /* else power is 0 and d is 1 */
return d;
}
/* Function to format a floating point value in ASCII with a given * precision.
*/ void/* PRIVATE */
png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size, double fp, unsignedint 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.
*/
/* 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;
elseif (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 */
}
/* 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.
*/
{ unsignedint uexp_b10;
if (exp_b10 < 0)
{
*ascii++ = 45; --size; /* '-': PLUS 1 TOTAL 3+precision */
uexp_b10 = 0U-exp_b10;
}
/* 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];
/* Here on buffer too small. */
png_error(png_ptr, "ASCII conversion buffer too small");
} # endif /* FLOATING_POINT */
# ifdef PNG_FIXED_POINT_SUPPORTED /* Function to format a fixed point value in ASCII.
*/ void/* PRIVATE */
png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii,
size_t size, png_fixed_point fp)
{ /* Require space for 10 decimal digits, a decimal point, a minus sign and a * trailing \0, 13 characters:
*/ if (size > 12)
{
png_uint_32 num;
/* Avoid overflow here on the minimum integer. */ if (fp < 0)
{
*ascii++ = 45; num = (png_uint_32)(-fp);
} else
num = (png_uint_32)fp;
if (num <= 0x80000000) /* else overflowed */
{ unsignedint ndigits = 0, first = 16/* flag value */; char digits[10] = {0};
while (num)
{ /* Split the low digit off num: */ unsignedint 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)
{ unsignedint 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 */
#ifdefined(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.
*/ 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; return1;
} 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; return1;
} #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; return1;
}
} #endif
}
}
#ifdefined(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"); return0;
} #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
return0; /* 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
return0; /* 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
return0; /* 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.
*/ staticconst 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
#if0 /* 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(unsignedint x)
{ unsignedint 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)
{ unsignedint 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;
/* 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.
*/ staticconst 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. */ #if0 for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"} 1144937.64284865548751208448 1045180.98734845585101160448 945303.31936980687359311872 845364.65110595323018870784 745395.35850361789624614912 645410.72259715102037508096 545418.40724413220722311168 445422.25021786898173001728 345424.17186732298419044352 245425.13273269940811464704 145425.61317555035558641664 045425.85339951654943850496 #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 */ return0;
}
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(unsignedint 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(unsignedint 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, unsignedint 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 */ return0; #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.
*/ staticvoid
png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable, unsignedint shift, png_fixed_point gamma_val)
{ /* Various values derived from 'shift': */ unsignedint 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 unsignedint max = (1U << (16U - shift)) - 1U; unsignedint max_by_2 = 1U << (15U - shift); unsignedint 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.
*/ unsignedint 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. */ unsignedint j;
/* NOTE: this function expects the *inverse* of the overall gamma transformation * required.
*/ staticvoid
png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable, unsignedint shift, png_fixed_point gamma_val)
{ unsignedint num = 1U << (8U - shift); unsignedint max = (1U << (16U - shift))-1U; unsignedint 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;
/* 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.
*/ staticvoid
png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable,
png_fixed_point gamma_val)
{ unsignedint 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);
/* 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 */
#ifdef PNG_16BIT_SUPPORTED if (png_ptr->gamma_16_from_1 != NULL)
{ int i; int istop = (1 << (8 - png_ptr->gamma_shift)); for (i = 0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_from_1[i]);
}
png_free(png_ptr, png_ptr->gamma_16_from_1);
png_ptr->gamma_16_from_1 = NULL;
} if (png_ptr->gamma_16_to_1 != NULL)
{ int i; int istop = (1 << (8 - png_ptr->gamma_shift)); for (i = 0; i < istop; i++)
{
png_free(png_ptr, png_ptr->gamma_16_to_1[i]);
}
png_free(png_ptr, png_ptr->gamma_16_to_1);
png_ptr->gamma_16_to_1 = NULL;
} #endif/* 16BIT */ #endif/* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
}
/* We build the 8- or 16-bit gamma tables here. Note that for 16-bit * tables, we don't make a full table if we are reducing to 8-bit in * the future. Note also how the gamma_16 tables are segmented so that * we don't need to allocate > 64K chunks for a full 16-bit table.
*/ void/* PRIVATE */
png_build_gamma_table(png_structrp png_ptr, int bit_depth)
{
png_debug(1, "in png_build_gamma_table");
/* Remove any existing table; this copes with multiple calls to * png_read_update_info. The warning is because building the gamma tables * multiple times is a performance hit - it's harmless but the ability to * call png_read_update_info() multiple times is new in 1.5.6 so it seems * sensible to warn if the app introduces such a hit.
*/ if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL)
{
png_warning(png_ptr, "gamma table being rebuilt");
png_destroy_gamma_table(png_ptr);
}
/* 16-bit gamma code uses this equation: * * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8] * * Where 'iv' is the input color value and 'ov' is the output value - * pow(iv, gamma). * * Thus the gamma table consists of up to 256 256-entry tables. The table * is selected by the (8-gamma_shift) most significant of the low 8 bits * of the color value then indexed by the upper 8 bits: * * table[low bits][high 8 bits] * * So the table 'n' corresponds to all those 'iv' of: * * <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1> *
*/ if (sig_bit > 0 && sig_bit < 16U) /* shift == insignificant bits */
shift = (png_byte)((16U - sig_bit) & 0xff);
else
shift = 0; /* keep all 16 bits */
if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
{ /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively * the significant bits in the *input* when the output will * eventually be 8 bits. By default it is 11.
*/ if (shift < (16U - PNG_MAX_GAMMA_8))
shift = (16U - PNG_MAX_GAMMA_8);
}
if (shift > 8U)
shift = 8U; /* Guarantees at least one table! */
png_ptr->gamma_shift = shift;
/* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now * PNG_COMPOSE). This effectively smashed the background calculation for * 16-bit output because the 8-bit table assumes the result will be * reduced to 8 bits.
*/ if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0)
png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift,
png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma,
png_ptr->screen_gamma) : PNG_FP_1);
/* Notice that the '16 from 1' table should be full precision, however * the lookup on this table still uses gamma_shift, so it can't be. * TODO: fix this.
*/
png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift,
png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) :
png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */);
} #endif/* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */
} #endif/* 16BIT */
} #endif/* READ_GAMMA */
/* HARDWARE OR SOFTWARE OPTION SUPPORT */ #ifdef PNG_SET_OPTION_SUPPORTED int PNGAPI
png_set_option(png_structrp png_ptr, int option, int onoff)
{ if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT &&
(option & 1) == 0)
{
png_uint_32 mask = 3U << option;
png_uint_32 setting = (2U + (onoff != 0)) << option;
png_uint_32 current = png_ptr->options;
/* sRGB support */ #ifdefined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\ defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) /* sRGB conversion tables; these are machine generated with the code in * contrib/tools/makesRGB.c. The actual sRGB transfer curve defined in the * specification (see the article at https://en.wikipedia.org/wiki/SRGB) * is used, not the gamma=1/2.2 approximation use elsewhere in libpng. * The sRGB to linear table is exact (to the nearest 16-bit linear fraction). * The inverse (linear to sRGB) table has accuracies as follows: * * For all possible (255*65535+1) input values: * * error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact * * For the input values corresponding to the 65536 16-bit values: * * error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact * * In all cases the inexact readings are only off by one.
*/
/* Double check that we have a png_ptr - it should be impossible to get here * without one.
*/ if (cp->png_ptr == NULL) return0;
/* First free any data held in the control structure. */ # ifdef PNG_STDIO_SUPPORTED if (cp->owned_file != 0)
{
FILE *fp = png_voidcast(FILE*, cp->png_ptr->io_ptr);
cp->owned_file = 0;
/* Copy the control structure so that the original, allocated, version can be * safely freed. Notice that a png_error here stops the remainder of the * cleanup, but this is probably fine because that would indicate bad memory * problems anyway.
*/
c = *cp;
image->opaque = &c;
png_free(c.png_ptr, cp);
/* Then the structures, calling the correct API. */ if (c.for_write != 0)
{ # ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
png_destroy_write_struct(&c.png_ptr, &c.info_ptr); # else
png_error(c.png_ptr, "simplified write not supported"); # endif
} else
{ # ifdef PNG_SIMPLIFIED_READ_SUPPORTED
png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL); # else
png_error(c.png_ptr, "simplified read not supported"); # endif
}
/* Success. */ return1;
}
void PNGAPI
png_image_free(png_imagep image)
{ /* Safely call the real function, but only if doing so is safe at this point * (if not inside an error handling context). Otherwise assume * png_safe_execute will call this API after the return.
*/ if (image != NULL && image->opaque != NULL &&
image->opaque->error_buf == NULL)
{
png_image_free_function(image);
image->opaque = NULL;
}
}
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