Java如何设置图片的透明度

@Overridepublic void paint(Graphics g){try {Image bgimage = ImageIO.read(new File("src/image/bgimage.png"));} catch (IOException e) {e.printStackTrace();}AlphaComposite ac = AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.6f);    Graphics2D g2d = (Graphics2D) g;     g2d.setComposite(ac);    g2d.drawImage(bgimage, x, y, width, height, this);}