code: public static double selectZoomToFitInDisplay( int width , int height ) {
  		Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
  
  		double w = screenSize.getWidth();
  		double h = screenSize.getHeight();
  
  		double scale = Math.max(width/w,height/h);
  		if( scale > 1.0 ) {
  			return 1.0/scale;
  		} else {
  			return 1.0;
  		}
  	}
docs: Figures out what the scale should be to fit the window inside the default display