java swing的背景图片按比例缩放

import java.awt.*;import java.awt.image.BufferedImage;import javax.swing.Icon;import javax.swing.ImageIcon;import javax.swing.JFrame;import javax.swing.JLabel;public class ScaleIcon implements Icon {    private BufferedImage i = null;    private Icon icon = null;    public ScaleIcon(Icon icon) {        this.icon = icon;    }    @Override    public int getIconHeight() {        return icon.getIconHeight();    }    @Override    public int getIconWidth() {        return icon.getIconWidth();    }    public void paintIcon(Component c, Graphics g, int x, int y) {        float wid = c.getWidth();        float hei = c.getHeight();        int iconWid = icon.getIconWidth();        int iconHei = icon.getIconHeight();        Graphics2D g2d = (Graphics2D) g;        g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);        g2d.scale(wid / iconWid, hei / iconHei);        icon.paintIcon(c, g2d, 0, 0);    }    public static void main(String[] args) {        ScaleIcon icon = new ScaleIcon(new ImageIcon(ClassLoader.getSystemResource("img/main.jpg")));        JLabel label = new JLabel(icon);        JFrame frame = new JFrame();        frame.getContentPane().add(label, BorderLayout.CENTER);//                frame.getContentPane().add(new JButton("click"),BorderLayout.NORTH);        frame.setSize(800, 600);        frame.setLocationRelativeTo(null);        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        frame.setVisible(true);    }}