--- IO/vtkPNGWriter.h.orig	2011-03-16 12:18:56.000000000 +0100
+++ IO/vtkPNGWriter.h	2011-03-16 15:29:25.000000000 +0100
@@ -51,12 +51,21 @@
   virtual void SetResult(vtkUnsignedCharArray*);
   vtkGetObjectMacro(Result, vtkUnsignedCharArray);
 
+  // Description:
+  // Set/Get the zlib compression level.
+  // The range is 0-6, with 0 meaning no compression
+  // and largest image size, and 6 meaning compression
+  // and smaller image size. The default is 3.
+  vtkSetClampMacro(CompressionLevel, int, 0, 9);
+  vtkGetMacro(CompressionLevel, int);
+
 protected:
   vtkPNGWriter();
   ~vtkPNGWriter();
   
   void WriteSlice(vtkImageData *data);
   unsigned int WriteToMemory;
+  int CompressionLevel;
   vtkUnsignedCharArray *Result;
   FILE *TempFP;
   
--- IO/vtkPNGWriter.cxx.orig	2011-03-16 12:18:51.000000000 +0100
+++ IO/vtkPNGWriter.cxx	2011-03-16 15:38:31.000000000 +0100
@@ -29,6 +29,7 @@
   this->FileLowerLeft = 1;
   this->FileDimensionality = 2;
   this->WriteToMemory = 0;
+  this->CompressionLevel = 0;
   this->Result = 0;
   this->TempFP = 0;
 }
@@ -185,6 +186,8 @@
     vtkErrorMacro(<<"Unable to write PNG file!");
     return;
     }
+
+  png_set_compression_level(png_ptr, CompressionLevel);
   
   png_infop info_ptr = png_create_info_struct(png_ptr);
   if (!info_ptr)