code: public static void clear(Image img) {
          Graphics g = img.getGraphics();
          
          try {
              if (g instanceof Graphics2D) {
                  ((Graphics2D) g).setComposite(AlphaComposite.Clear);
              } else {
                  g.setColor(new Color(0, 0, 0, 0));
              }
              
              g.fillRect(0, 0, img.getWidth(null), img.getHeight(null));
          } finally {
              g.dispose();
          }
      }
docs: Clears the data from the image.
  
  @param img
  the image to erase