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[libpng16] Recognize known sRGB ICC profiles while reading; prefer writing the

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iCCP profile over writing the sRGB chunk, controlled by the
    PNG_sRGB_PROFILE_CHECKS option.
This commit is contained in:
John Bowler
2012-03-28 23:36:12 -05:00
committed by Glenn Randers-Pehrson
parent 23a30f8583
commit 921648a997
10 changed files with 347 additions and 160 deletions
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198
png.c
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@@ -747,13 +747,13 @@ png_get_copyright(png_const_structrp png_ptr)
#else
# ifdef __STDC__
return PNG_STRING_NEWLINE \
"libpng version 1.6.0beta20 - March 21, 2012" PNG_STRING_NEWLINE \
"libpng version 1.6.0beta20 - March 29, 2012" PNG_STRING_NEWLINE \
"Copyright (c) 1998-2012 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
"Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
"Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
PNG_STRING_NEWLINE;
# else
return "libpng version 1.6.0beta20 - March 21, 2012\
return "libpng version 1.6.0beta20 - March 29, 2012\
Copyright (c) 1998-2012 Glenn Randers-Pehrson\
Copyright (c) 1996-1997 Andreas Dilger\
Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -1974,17 +1974,192 @@ png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace,
return 1;
}
void /* PRIVATE */
#ifdef PNG_sRGB_SUPPORTED
/* Information about the known ICC sRGB profiles */
static const struct
{
png_uint_32 adler, crc, length;
png_uint_32 md5[4];
png_uint_16 have_md5;
png_uint_16 intent;
# define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0)
# define PNG_ICC_CHECKSUM(adler, crc, md5, intent, date, length, fname)\
{ adler, crc, length, md5, 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,
"2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc")
/* ICC sRGB v2 perceptual no black-compensation: */
PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21,
PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1,
"2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc")
PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae,
PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0,
"2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc")
/* ICC sRGB v4 perceptual */
PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812,
PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0,
"2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc")
/* The following profiles have no known MD5 checksum, if there is a match
* on the (empty) MD5 the other fields are used to attempt a match and
* a warning is produced. The first two of these profiles have a 'cprt' tag
* which suggests that they were also made by Hewlett Packard.
*/
PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce,
PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1,
"2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc")
PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552,
PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0,
"1998/02/09 06:49:00", 3144, "sRGB Profile.icc")
PNG_ICC_CHECKSUM(0x0398f3fcUL, 0xf29e526dUL,
PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0,
"unknown", 3144, "HP-Microsoft sRGB v2 perceptual")
};
static int
png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr,
png_const_bytep profile, uLong adler)
{
/* The quick check is to verify just the MD5 signature and trust to 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 editted with an intent not defined
* by sRGB (but maybe defined by a later ICC specification) the read of
* the profile will fail at that point.
*/
png_uint_32 length = 0;
png_uint_32 intent = 0x10000; /* invalid */
#if PNG_sRGB_PROFILE_CHECKS > 1
uLong crc = 0; /* the value for 0 length data */
#endif
unsigned int i;
for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i)
{
if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] &&
png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] &&
png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] &&
png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3])
{
/* This may be one of the old HP profiles without an MD5, in that
* case we can only use the length and Adler32 (note that these
* are not used by default if there is an MD5!)
*/
# if PNG_sRGB_PROFILE_CHECKS == 0
if (png_sRGB_checks[i].have_md5)
return 1;
# endif
/* Profile is unsigned or more checks have been configured in. */
if (length == 0)
{
length = png_get_uint_32(profile);
intent = png_get_uint_32(profile+64);
}
/* Length *and* intent must match */
if (length == png_sRGB_checks[i].length &&
intent == png_sRGB_checks[i].intent)
{
/* Now calculate the alder32 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
{
/* 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.
*/
if (!png_sRGB_checks[i].have_md5)
{
# ifdef PNG_READ_SUPPORTED
if (png_ptr->mode & PNG_IS_READ_STRUCT)
png_chunk_warning(png_ptr,
"out-of-date sRGB profile with no signature");
else
# endif
png_app_warning(png_ptr,
"out-of-date sRGB profile with no signature");
}
return 1;
}
}
}
# if PNG_sRGB_PROFILE_CHECKS > 0
/* The signature matched, but the profile had been changed in some
* way. This is an apparent violation of the ICC terms of use and,
* anyway, the rejection may be unexpected.
*/
if (png_sRGB_checks[i].have_md5)
png_benign_error(png_ptr,
"copyright violation: edited ICC profile ignored");
# endif
}
}
return 0; /* no match */
}
#endif
int /* PRIVATE */
png_icc_set_gAMA_and_cHRM(png_const_structrp png_ptr,
png_colorspacerp colorspace, png_const_charp name, png_const_bytep profile,
int preferred)
uLong adler, int preferred)
{
/* TODO: implement this! */
PNG_UNUSED(png_ptr)
PNG_UNUSED(colorspace)
PNG_UNUSED(name)
PNG_UNUSED(profile)
PNG_UNUSED(preferred)
# ifdef PNG_sRGB_SUPPORTED
/* 1) 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))
return png_colorspace_set_sRGB(png_ptr, colorspace,
(int)/*already checked*/png_get_uint_32(profile+64), preferred);
else
# endif
/* 2) Attempt to extract the gAMA and cHRM information from non-sRGB
* profiles.
*/
{
/* TODO: implement this! */
PNG_UNUSED(name) /* NYI */
return 1;
}
}
int /* PRIVATE */
@@ -2000,7 +2175,8 @@ png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace,
&& png_icc_check_tag_table(png_ptr, colorspace, name, profile_length,
profile))
{
png_icc_set_gAMA_and_cHRM(png_ptr, colorspace, name, profile, preferred);
png_icc_set_gAMA_and_cHRM(png_ptr, colorspace, name, profile, 0,
preferred);
return 1;
}