$image_over->Read("over.gif");
     $image_under->Read("under.jpg");

     $image_over->Transparent("white"); # Set the transp. color
     $image_under->Composite(
	  compose => 'Over',
	  opacity => 50, # Doesn't seem to work with 'Over'
	  x => 20,
	  y => 25,
	  image => $image_over,
        ) ;
     $image_under->Write("Composite.jpg");