private static Image createBlankThumbnail(final int w,final int h){
  final Canvas canvas=new Canvas(w,h);
  final GraphicsContext gc=canvas.getGraphicsContext2D();
  gc.setFill(Color.WHITE);
  gc.fillRect(0.2,0.2,w - .5,h - .5);
  gc.setFill(Color.BLACK);
  gc.strokeRect(0.2,0.2,w - .5,h - .5);
  gc.strokeLine(0,0,w,h);
  gc.strokeLine(0,h,w,0);
  return canvas.snapshot(null,null);
}

private static Image createBlankThumbnail ( final int w , final int h ) { final Canvas canvas = new Canvas ( w , h ) ; final GraphicsContext gc = canvas . getGraphicsContext2D ( ) ; gc . setFill ( Color . WHITE ) ; gc . fillRect ( 0.2 , 0.2 , w - .5 , h - .5 ) ; gc . setFill ( Color . BLACK ) ; gc . strokeRect ( 0.2 , 0.2 , w - .5 , h - .5 ) ; gc . strokeLine ( 0 , 0 , w , h ) ; gc . strokeLine ( 0 , h , w , 0 ) ; return canvas . snapshot ( null , null ) ; }
create a blank tile with a cross to use as a thumbnail for unloaded page
