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factor
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minor refactoring

db4
Doug Coleman 2009-09-26 22:24:14 -05:00
parent 4bc6b302cf
commit 033892dc10
1 changed files with 11 additions and 5 deletions
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16
basis/images/png/png.factor
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@ -82,17 +82,23 @@ ERROR: unimplemented-color-type image ;
: inflate-data ( loading-png -- bytes )
find-compressed-bytes zlib-inflate ;
: png-group-width ( loading-png -- n )
: scale-bit-depth ( loading-png -- n ) bit-depth>> 8 / ; inline
: png-bytes-per-pixel ( loading-png -- n )
dup color-type>> {
{ 2 [ [ bit-depth>> 8 / 3 * ] [ width>> ] bi * 1 + ] }
{ 6 [ [ bit-depth>> 8 / 4 * ] [ width>> ] bi * 1 + ] }
{ 2 [ scale-bit-depth 3 * ] }
{ 6 [ scale-bit-depth 4 * ] }
[ unknown-color-type ]
} case ;
} case ; inline
: png-group-width ( loading-png -- n )
! 1 + is for the filter type, 1 byte preceding each line
[ png-bytes-per-pixel ] [ width>> ] bi * 1 + ;
:: paeth ( a b c -- p )
a b + c - { a b c } [ [ - abs ] keep 2array ] with map
sort-keys first second ;
:: png-unfilter-line ( prev curr filter -- curr' )
prev :> c
prev 3 tail-slice :> b