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[devel] Use the old scaling method for background if png_set_chop_16() was

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called.
This commit is contained in:
Glenn Randers-Pehrson 2011-06-14 06:30:12 -05:00
parent 550bab03fb
commit 7dffa41643
3 changed files with 17 additions and 0 deletions
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2
ANNOUNCE
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@ -198,6 +198,8 @@ Version 1.5.4beta02 [June 14, 2011]
Added png_set_chop_16() API, to match inaccurate results from previous Added png_set_chop_16() API, to match inaccurate results from previous
libpng versions. libpng versions.
Removed the ACCURATE and LEGACY options (they are no longer useable) Removed the ACCURATE and LEGACY options (they are no longer useable)
Use the old scaling method for background if png_set_chop_16() was
called.
Send comments/corrections/commendations to png-mng-implement at lists.sf.net: Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
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2
CHANGES
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@ -3461,6 +3461,8 @@ Version 1.5.4beta02 [June 14, 2011]
Added png_set_chop_16() API, to match inaccurate results from previous Added png_set_chop_16() API, to match inaccurate results from previous
libpng versions. libpng versions.
Removed the ACCURATE and LEGACY options (they are no longer useable) Removed the ACCURATE and LEGACY options (they are no longer useable)
Use the old scaling method for background if png_set_chop_16() was
called.
Send comments/corrections/commendations to png-mng-implement at lists.sf.net Send comments/corrections/commendations to png-mng-implement at lists.sf.net
(subscription required; visit (subscription required; visit

13
pngrtran.c
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@ -1453,12 +1453,25 @@ png_init_read_transformations(png_structp png_ptr)
* The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
* present, so that case is ok (until do_expand_16 is moved.) * present, so that case is ok (until do_expand_16 is moved.)
*/ */
if (png_ptr->transformations & PNG_CHOP_16_TO_8)
{
# define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16)) # define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))
CHOP(png_ptr->background.red); CHOP(png_ptr->background.red);
CHOP(png_ptr->background.green); CHOP(png_ptr->background.green);
CHOP(png_ptr->background.blue); CHOP(png_ptr->background.blue);
CHOP(png_ptr->background.gray); CHOP(png_ptr->background.gray);
# undef CHOP # undef CHOP
}
else /* Use pre-libpng-1.5.4 inaccurate "ACCURATE" scaling */
{
# define CHOP(x) ((png_uint_16)((2*(png_uint_32)(x) + 257)/514))
CHOP(png_ptr->background.red);
CHOP(png_ptr->background.green);
CHOP(png_ptr->background.blue);
CHOP(png_ptr->background.gray);
# undef CHOP
}
} }
#endif #endif