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crc32 the png chunks, helper word to concatenate deflated bytes

db4
Doug Coleman 2009-03-04 13:34:28 -06:00
parent 6ee3f802a4
commit 992d1f4d13
1 changed files with 39 additions and 8 deletions
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47
basis/images/png/png.factor
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@ -2,15 +2,18 @@
! See http://factorcode.org/license.txt for BSD license.
USING: accessors constructors images io io.binary io.encodings.ascii
io.encodings.binary io.encodings.string io.files io.files.info kernel
sequences io.streams.limited ;
sequences io.streams.limited fry combinators arrays math
checksums checksums.crc32 ;
IN: images.png
TUPLE: png-image < image chunks ;
TUPLE: png-image < image chunks
width height bit-depth color-type compression-method
filter-method interlace-method uncompressed ;
CONSTRUCTOR: png-image ( -- image )
V{ } clone >>chunks ;
TUPLE: png-chunk length type data crc ;
TUPLE: png-chunk length type data ;
CONSTRUCTOR: png-chunk ( -- png-chunk ) ;
@ -23,19 +26,47 @@ ERROR: bad-png-header header ;
bad-png-header
] unless drop ;
ERROR: bad-checksum ;
: read-png-chunks ( image -- image )
<png-chunk>
4 read be> >>length
4 read ascii decode >>type
dup length>> read >>data
4 read >>crc
4 read be> [ >>length ] [ 4 + ] bi
read dup crc32 checksum-bytes
4 read = [ bad-checksum ] unless
4 cut-slice
[ ascii decode >>type ]
[ B{ } like >>data ] bi*
[ over chunks>> push ]
[ type>> ] bi "IEND" =
[ read-png-chunks ] unless ;
: find-chunk ( image string -- chunk )
[ chunks>> ] dip '[ type>> _ = ] find nip ;
: parse-ihdr-chunk ( image -- image )
dup "IHDR" find-chunk data>> {
[ [ 0 4 ] dip subseq be> >>width ]
[ [ 4 8 ] dip subseq be> >>height ]
[ [ 8 ] dip nth >>bit-depth ]
[ [ 9 ] dip nth >>color-type ]
[ [ 10 ] dip nth >>compression-method ]
[ [ 11 ] dip nth >>filter-method ]
[ [ 12 ] dip nth >>interlace-method ]
} cleave ;
: find-compressed-bytes ( image -- bytes )
chunks>> [ type>> "IDAT" = ] filter
[ data>> ] map concat ;
: fill-image-data ( image -- image )
dup [ width>> ] [ height>> ] bi 2array >>dim ;
: load-png ( path -- image )
[ binary <file-reader> ] [ file-info size>> ] bi stream-throws <limited-stream> [
[ binary <file-reader> ] [ file-info size>> ] bi
stream-throws <limited-stream> [
<png-image>
read-png-header
read-png-chunks
parse-ihdr-chunk
fill-image-data
] with-input-stream ;