crc32 the png chunks, helper word to concatenate deflated bytes

diff --git a/basis/images/png/png.factor b/basis/images/png/png.factor
index 0965a13ad66605fecc6d1934b50c131c9125581c..b02736297773efdc9428fe46c850f1976b5ec378 100755 (executable)
--- a/basis/images/png/png.factor
+++ b/basis/images/png/png.factor
@@ -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 ;