Merge topic '14426-huge-png' into master

21df2adc Change the default compression level for PNG to 5.

IO/Image/vtkPNGWriter.cxx

@@ -30,7 +30,7 @@ vtkPNGWriter::vtkPNGWriter()
 {
   this->FileLowerLeft = 1;
   this->FileDimensionality = 2;
-  this->CompressionLevel = 0;
+  this->CompressionLevel = 5;
   this->WriteToMemory = 0;
   this->Result = 0;
   this->TempFP = 0;

IO/Image/vtkPNGWriter.h

@@ -45,7 +45,7 @@ public:
   // The range is 0-9, with 0 meaning no compression
   // corresponding to the largest file size, and 9 meaning
   // best compression, corresponding to the smallest file size.
-  // The default is 0.
+  // The default is 5.
   vtkSetClampMacro(CompressionLevel, int, 0, 9);
   vtkGetMacro(CompressionLevel, int);