--- a/PNGReader.st	Fri Jul 31 14:14:55 2009 +0200
+++ b/PNGReader.st	Fri Jul 31 15:06:56 2009 +0200
@@ -12,9 +12,9 @@
 "{ Package: 'stx:libview2' }"
 
 ImageReader subclass:#PNGReader
-	instanceVariableNames:'colorType depth compressionMethod filterMethod interlaceMode
-		redBytes greenBytes blueBytes bytesPerScanline globalDataChunk
-		thisScanline prevScanline'
+	instanceVariableNames:'colorType bitsPerChannel depth compressionMethod filterMethod
+		interlaceMode redBytes greenBytes blueBytes bytesPerScanline
+		globalDataChunk thisScanline prevScanline'
 	classVariableNames:''
 	poolDictionaries:''
 	category:'Graphics-Images-Readers'
@@ -62,7 +62,7 @@
 
     PNGReader fromFile:'C:\Users\cg\Desktop\croquet\cobalt-base-current-build-20090210\cobalt-base-current-build-20090210\content\models\textures\checkerboard.png'
     PNGReader fromFile:'C:\Dokumente und Einstellungen\cg\Desktop\misc\PNGs\Delete.png'
-
+    PNGReader fromFile:'\\exeptn\unsaved\pd_stuff\PNGs\Delete.png'
 "
 ! !
 
@@ -175,7 +175,7 @@
 processIHDRChunkLen:len
     "header chunk - currently unhandled"
 
-    |bitsPerChannel interlaceMethod palette image bitsPerPixel rowSize|
+    |interlaceMethod palette image bitsPerPixel rowSize|
 
 self halt.        
     width := inStream nextLongMSB:true.   "/ 1..4
@@ -198,7 +198,7 @@
                        palette: (colorType = 0 
                                         ifTrue: [self grayColorsFor: depth] 
                                         ifFalse: [palette := self class defaultPalette])].
-    bitsPerPixel := (BPP at: colorType + 1) at: bitsPerChannel highBit.
+    "/ bitsPerPixel := (BPP at: colorType + 1) at: bitsPerChannel highBit.
     bytesPerScanline := (width * bitsPerPixel + 7) // 8.
     rowSize := image width * image depth + 31 >> 5
 !
@@ -335,15 +335,71 @@
     ]
 !
 
+filterPaeth: count
+    "Select one of (the pixel to the left, the pixel above and the pixel to above left) to
+    predict the value of this pixel"
+
+    | delta |
+
+    delta _ self bitsPerPixel // 8 max: 1.
+    1 to: delta do: [ :i |
+        thisScanline at: i put:
+            (((thisScanline at: i) + (prevScanline at: i)) bitAnd: 255)].
+    delta+1 to: count do: [ :i |
+        thisScanline
+            at: i
+            put: (((thisScanline at: i) + (self
+                paethPredictLeft: (thisScanline at: i-delta)
+                above: (prevScanline at: i)
+                aboveLeft: (prevScanline at: i-delta)))
+                    bitAnd: 255)]
+!
+
 filterScanline:filterType count:count
     self 
         perform:(#(filterNone: filterHorizontal: filterVertical: filterAverage: filterPaeth:)
                     at:filterType+1)
         with:count
+!
+
+filterVertical: count
+    "Use the pixel above as a predictor"
+
+    1 to: count do: [ :i |
+        thisScanline at: i put: (((thisScanline at: i) +
+                                 (prevScanline at: i)) bitAnd: 255) 
+    ]
+!
+
+paethPredictLeft: a above: b aboveLeft: c
+    "Predicts the value of a pixel based on nearby pixels, based on Paeth (GG II, 1991)"
+
+    | pa pb pc |
+
+    pa := b > c ifTrue: [b - c] ifFalse: [c - b].
+    pb := a > c ifTrue: [a - c] ifFalse: [c - a].
+    pc := a + b - c - c.
+    pc < 0 ifTrue: [
+        pc := pc * -1
+    ].
+    ((pa <= pb) and: [pa <= pc]) ifTrue: [^ a].
+    (pb <= pc) ifTrue: [^ b].
+    ^ c
 ! !
 
 !PNGReader methodsFor:'private-reading'!
 
+copyPixelsRGBA: y
+    "Handle non-interlaced RGBA color modes (colorType = 6)"
+
+    |bpr i|
+
+    bpr := self bytesPerRow.
+    i := y * bpr.
+
+    data replaceFrom:1+i to:(i+bpr-1) with:thisScanline startingAt:1.
+!
+
 getChunk
     |len type crc|
 
@@ -501,6 +557,8 @@
         
     [self getChunk] whileTrue.
 
+    data := ByteArray new:(self bytesPerRow * height).
+
     globalDataChunk notNil ifTrue:[
         self processGlobalIDATChunk
     ].
@@ -603,7 +661,7 @@
 !PNGReader class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libview2/PNGReader.st,v 1.14 2009-07-31 12:14:55 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libview2/PNGReader.st,v 1.15 2009-07-31 13:06:56 cg Exp $'
 ! !
 
 PNGReader initialize!