Swing で画像を徐々に回転させるにはどうすればよいですか?

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;

import javax.swing.JPanel;
import javax.swing.Timer;

public class RotateImagePanel extends JPanel implements ActionListener {

    private Image image;
    private AffineTransform transform;
    private double angle;
    private Timer timer;

    public RotateImagePanel(Image image) {
        this.image = image;
        transform = new AffineTransform();
        angle = 0;
        timer = new Timer(100, this);
        timer.start();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.translate(getWidth() / 2, getHeight() / 2);
        g2.rotate(angle, image.getWidth(null) / 2, image.getHeight(null) / 2);
        g2.drawImage(image, transform, null);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        angle += Math.PI / 100;
        repaint();
    }
}