--- a/PNGReader.st	Thu May 16 19:32:28 2019 +0200
+++ b/PNGReader.st	Sun May 19 20:18:30 2019 +0200
@@ -1,5 +1,3 @@
-"{ Encoding: utf8 }"
-
 "
  COPYRIGHT (c) 1996 by Claus Gittinger
               All Rights Reserved
@@ -145,6 +143,25 @@
 
 !PNGReader class methodsFor:'testing'!
 
+file:filename hasSpecialChunk:chunkTag
+    "true if there is a special chunk with chunkTag in filename"
+
+    |pngReader hasChunk|
+
+    hasChunk := false.    
+    pngReader := self new.
+    pngReader extractSpecialChunksOnly:true.
+    pngReader 
+        specialChunkHandlerAt:chunkTag 
+        put:[:data | hasChunk := true].
+    filename asFilename readingFileDo:[:inStream |        
+        pngReader fromStream:inStream.
+    ].        
+    ^ hasChunk
+
+    "Created: / 19-05-2019 / 20:15:13 / Claus Gittinger"
+!
+
 isValidImageFile:aFileName
     "return true, if aFileName contains a PNG image"