--- a/PNGReader.st	Thu Aug 31 15:29:24 2017 +0200
+++ b/PNGReader.st	Thu Aug 31 17:30:19 2017 +0200
@@ -1413,6 +1413,7 @@
     outStream binary.
 
     byteOrder := #msb.
+    
     width := image width.
     height := image height.
     photometric := image photometric.
@@ -1440,6 +1441,7 @@
     self writeEndChunk
 
     "Modified: / 23-08-2017 / 16:25:00 / cg"
+    "Modified (format): / 31-08-2017 / 17:26:28 / cg"
 ! !
 
 !PNGReader methodsFor:'writing-private'!
@@ -1487,6 +1489,9 @@
 !PNGReader methodsFor:'writing-private chunks'!
 
 determineColorTypeAndHasMask
+    "sets colorType as side effect;
+     returns boolean if a mask is present"
+     
     ((photometric == #whiteIs0) or:[ (photometric == #blackIs0)]) ifTrue:[
         colorType := ColorTypeGray.
         ^ (samplesPerPixel > 1)
@@ -1507,6 +1512,7 @@
     ^ false.
 
     "Created: / 11-04-2017 / 12:39:30 / cg"
+    "Modified (comment): / 31-08-2017 / 17:24:31 / cg"
 !
 
 writeChunk:chunkTypeChars size:len with:aBlock
@@ -1550,16 +1556,17 @@
         writeChunk: 'IHDR'
         size: (4+4+5)
         with:[ 
-            self writeLong:width.
-            self writeLong:height.
-            outStream nextPut: 8.  "Assume that all colors are 24bit"     "/ depth
+            outStream nextPutInt32:width MSB:true.   
+            outStream nextPutInt32:height MSB:true.   
+            "Assume that all colors are 24bit"     
+            outStream nextPut:(depth == 1 ifTrue:[1] ifFalse:[8]).  "/ depth  
             outStream nextPut: colorType.  
             outStream nextPut: 0.  "Compression"
             outStream nextPut: 0.  "Filter method"
             outStream nextPut: 0   "Non-interlaced"
         ]
 
-    "Modified: / 11-04-2017 / 12:40:53 / cg"
+    "Modified: / 31-08-2017 / 17:28:19 / cg"
 !
 
 writeImageDataChunk