public javafx.scene.image.Image erase(int depth) {
		byte clear[] = new byte[256];
   	  	for (int i=0; i<256; i++) {
   		  clear[i] = (byte)((i<depth)?i:255);
   	  	}
   	  	ByteLookupTable blut=new ByteLookupTable(0, clear);  
   	   	LookupOp lop = new LookupOp(blut, null);  
   	   	lop.filter(originalImage,modifiedImage);
   	   	return SwingFXUtils.toFXImage(modifiedImage, null); // don't use null if have performance issue
   	   	//return SwingFXUtils.toFXImage(originalImage, null); // don't use null if have performance issue
	}