--- a/Depth4Image.st	Sun Mar 02 14:59:31 2014 +0100
+++ b/Depth4Image.st	Sun Mar 02 14:59:34 2014 +0100
@@ -80,16 +80,18 @@
      byteIndex "{ Class: SmallInteger }"
      byte      "{ Class: SmallInteger }" |
 
+    pixelFunction notNil ifTrue:[^ pixelFunction value:x value:y].
+
     lineIndex := (self bytesPerRow * y) + 1.
     byteIndex := lineIndex + (x // 2).
 
     "left pixel in high bits"
     byteIndex > bytes size ifTrue:[
-	^ 0
+        ^ 0
     ].
     byte := bytes at:byteIndex.
     x even ifTrue:[
-	^ (byte bitShift:-4) bitAnd:16rF.
+        ^ (byte bitShift:-4) bitAnd:16rF.
     ].
     ^ byte bitAnd:16rF.
 
@@ -1047,9 +1049,10 @@
 !Depth4Image class methodsFor:'documentation'!
 
 version
-    ^ '$Header: /cvs/stx/stx/libview/Depth4Image.st,v 1.52 2013-05-21 20:50:48 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libview/Depth4Image.st,v 1.53 2014-03-02 13:59:34 cg Exp $'
 !
 
 version_CVS
-    ^ '$Header: /cvs/stx/stx/libview/Depth4Image.st,v 1.52 2013-05-21 20:50:48 cg Exp $'
+    ^ '$Header: /cvs/stx/stx/libview/Depth4Image.st,v 1.53 2014-03-02 13:59:34 cg Exp $'
 ! !
+