Drag Moouse to rotate Image Smoothly

Question

I have to write an application look somewhat like igoogle's eyes. When I click onto an image, then every where I drag my mouse, the image will rotate smoothly (does not move, rotate only) to where my mouse position is? Think of an arrow that will rotate to point to wherever my pointer's position is. Can you guy give me some advices on how to accomplish this. Thanks. I do know the basic things, like how to rotate image and how to move object using MouseMotionListener... Thank in advance.
Edited by: yunaeyes on May 20, 2009 5:40 PM

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
public class SpinMe extends JPanel {
    BufferedImage image;
    double theta = 0;
    Point loc = new Point(140,150);
    public SpinMe() {
        initImage();
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        AffineTransform at =
            AffineTransform.getTranslateInstance(loc.x, loc.y);
        double cx = image.getWidth()/2.0;
        double cy = image.getHeight()/2.0;
        at.rotate(theta, cx, cy);
        g2.drawRenderedImage(image, at);
    private void initImage() {
        // make an image
        int w = 80;
        int h = 30;
        int type = BufferedImage.TYPE_INT_RGB;
        image = new BufferedImage(w, h, type);
        // make an arrow
        double cx = w/2.0;
        double cy = h/2.0;
        double len = w;
        double barb = 25.0;
        double phi = Math.toRadians(20);
        Path2D.Double arrow = new Path2D.Double();
        arrow.moveTo(cx-len/2, cy);
        arrow.lineTo(cx+len/2, cy);
        double theta = Math.PI + phi;
        double x = cx+len/2 + barb*Math.cos(theta);
        double y = cy + barb*Math.sin(theta);
        arrow.lineTo(x, y);
        arrow.moveTo(cx+len/2, cy);
        theta = Math.PI - phi;
        x = cx+len/2 + barb*Math.cos(theta);
        y = cy + barb*Math.sin(theta);
        arrow.lineTo(x, y);
        // draw the arrow into the image
        Graphics2D g2 = image.createGraphics();
        g2.setBackground(new Color(210,210,240));
        g2.clearRect(0,0,w,h);
        g2.setPaint(Color.red);
        g2.draw(arrow);
        g2.dispose();
    public static void main(String[] args) {
        SpinMe test = new SpinMe();
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(test);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
        test.addMouseListener(test.ma);
        test.addMouseMotionListener(test.ma);
    private double getTheta(Point p) {
        Point2D.Double ctr = getCenter();
        double dy = p.y - ctr.y;
        double dx = p.x - ctr.x;
        return Math.atan2(dy, dx);
    private Point2D.Double getCenter() {
        int iw = image.getWidth();
        int ih = image.getHeight();
        double cos = Math.abs(Math.cos(theta));
        double sin = Math.abs(Math.sin(theta));
        double width  = iw*cos + ih*sin;
        double height = ih*cos + iw*sin;
        Point2D.Double p = new Point2D.Double();
        p.x = loc.x + width/2;
        p.y = loc.y + height/2;
        return p;
    /** Use MouseInputAdapter for j2se 1.5- */
    private MouseAdapter ma = new MouseAdapter() {
        double offsetTheta;
        public void mousePressed(MouseEvent e) {
            offsetTheta = getTheta(e.getPoint()) - theta;
        public void mouseDragged(MouseEvent e) {
            theta = getTheta(e.getPoint()) - offsetTheta;
            repaint();
}