Getting the bounds of a drawn image on a panel

Question

Hello, I have a problem with getting the bounds of a drawn image on a panel...Since it is drawn as graphics, i tried getClipBounds and since my class extends JPanel i tried to get the bounds from the panel but neither of them worked properly. It only gets the bounds of a jframe that contains the panel.Then i tried to put the panel in a layeredpane and then a container; but this time the image disappeared completely. Hope someone can help or tell me what I am doing wrong. Thanks in advance. Here is the code below:
By the way what I am trying to do in this code is basically zooming the image in and out by dragging or the mouse wheel. But I need to get the bounds so that I can use this.
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* @author Admin
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.NoninvertibleTransformException;
import java.awt.geom.Point2D;
import javax.swing.JFrame;
import javax.swing.JLayeredPane;
import javax.swing.JPanel;
public class ZoomDemo extends JPanel {
AffineTransform tx = new AffineTransform();
String imagePath = "D:/Documents and Settings/Admin/Belgelerim/tsrm/resim.jpg";
Image image = Toolkit.getDefaultToolkit().getImage(imagePath);
int width = image.getWidth(this);
int height = image.getHeight(this);
int scrwidth = Toolkit.getDefaultToolkit().getScreenSize().width;
int scrheight = Toolkit.getDefaultToolkit().getScreenSize().height;
double zoomfac = 1.0;
int xAdj;
int yAdj;
int prevY;
double scale = 1.0;
Point pt;
public static int x;
public static int y;
public static int w;
public static int h;
public ZoomDemo() {
this.addMouseWheelListener(new ZoomHandler());
this.addMouseListener(new ZoomHandler());
this.addMouseMotionListener(new ZoomHandler());
  repaint();
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.drawImage(image, tx, this);
// x =    (int) g2.getClipBounds().getX();
// y=     (int) g2.getClipBounds().getY();
// w=     (int) g2.getClipBounds().getWidth();
// h=     (int) g2.getClipBounds().getHeight();
// System.out.println(x+" "+y+" "+w+" "+h);
//  public int getRectx(){
//    return x;
//public int getRecty(){
//    return y;
//public int getRectw(){
//    return w;
//public int getRecth(){
//    return h;
private class ZoomHandler implements MouseWheelListener,MouseListener, MouseMotionListener {
public void mousePressed(MouseEvent e){
    System.out.println("Mouse Pressed");
xAdj = e.getX();
yAdj = e.getY();
prevY = getY();
public void mouseDragged(MouseEvent e){
       System.out.println("Mouse Dragged");
boolean zoomed = false;
if(e.getY()<prevY){
     zoomfac = zoomfac + 0.1;
     prevY = e.getY();
     zoomed = true;
else if(e.getY()>prevY){
     zoomfac = zoomfac - 0.1;
     prevY = e.getY();
     zoomed = true;
   scale = zoomfac;
Point2D p1 = new Point((int)xAdj-(width/2),(int)yAdj-(height/2));
Point2D p2 = null;
try {
p2 = tx.inverseTransform(p1, null);
} catch (NoninvertibleTransformException ex) {
// should not get here
ex.printStackTrace();
return;
tx.setToIdentity();
tx.translate(p1.getX(), p1.getY());
tx.scale(scale, scale);
tx.translate(-p2.getX(), -p2.getY());
tx.transform(p1, p2);
ZoomDemo.this.revalidate();
ZoomDemo.this.repaint();
public void mouseWheelMoved(MouseWheelEvent e) {
if (e.getScrollType() == MouseWheelEvent.WHEEL_UNIT_SCROLL) {
Point2D p1 = e.getPoint();
Point2D p2 = null;
try {
p2 = tx.inverseTransform(p1, null);
} catch (NoninvertibleTransformException ex) {
// should not get here
ex.printStackTrace();
return;
scale -= (0.1 * e.getWheelRotation());
scale = Math.max(0.1, scale);
tx.setToIdentity();
tx.translate(p1.getX(), p1.getY());
tx.scale(scale, scale);
tx.translate(-p2.getX(), -p2.getY());
ZoomDemo.this.revalidate();
ZoomDemo.this.repaint();
        public void mouseClicked(MouseEvent e) {
            //throw new UnsupportedOperationException("Not supported yet.");
        public void mouseReleased(MouseEvent e) {
            //throw new UnsupportedOperationException("Not supported yet.");
        public void mouseEntered(MouseEvent e) {
           // throw new UnsupportedOperationException("Not supported yet.");
        public void mouseExited(MouseEvent e) {
           // throw new UnsupportedOperationException("Not supported yet.");
        public void mouseMoved(MouseEvent e) {
           // throw new UnsupportedOperationException("Not supported yet.");
public static void main(String[] args) {
//SwingUtilities.invokeLater(new ZoomDemo());
int scrwidth = Toolkit.getDefaultToolkit().getScreenSize().width;
int scrheight = Toolkit.getDefaultToolkit().getScreenSize().height;
JFrame f = new JFrame("Zoom");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(scrwidth , scrheight);
//JLayeredPane lp = new JLayeredPane();
//f.add(lp);
ZoomDemo zd = new ZoomDemo();
zd.getBounds();
f.add(zd);
//int x = (int) zd.getX();
//int y = (int) zd.getY();
//int w = (int) zd.getWidth();
//int h = (int) zd.getHeight();
//System.out.println(x+" "+y+" "+w+" "+h);
//zd.setBounds(x ,y ,w ,h );
//lp.add(zd, JLayeredPane.DEFAULT_LAYER);
//f.setLocationRelativeTo(null);
f.setVisible(true);
//lp.setVisible(true);
//zd.setVisible(true);
}Edited by: .mnemonic. on May 26, 2009 11:07 PM
Edited by: .mnemonic. on May 27, 2009 11:00 AM

Answer 1

You'll need a stable point in the component to track and orient to the scaling transform(s).
From this you can construct whatever you need in the way of image location and size.
Let's try a center&#8211;of&#8211;image tracking point:
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import javax.swing.*;
import javax.swing.event.MouseInputAdapter;
public class ZD extends JPanel {
    BufferedImage image;
    Point center;
    AffineTransform at = new AffineTransform();
    Point2D.Double origin = new Point2D.Double(0,0);
    public ZD(BufferedImage image) {
        this.image = image;
        center = new Point(image.getWidth()/2, image.getHeight()/2);
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                            RenderingHints.VALUE_INTERPOLATION_BICUBIC);
        g2.drawRenderedImage(image, at);
        g2.setPaint(Color.red);
        g2.fill(new Ellipse2D.Double(origin.x-1.5, origin.y-1.5, 4, 4));
        g2.setPaint(Color.blue);
        g2.fill(new Ellipse2D.Double(center.x-1.5, center.y-1.5, 4, 4));
    private void setTransform(double scale) {
        // keep image centered over Point "center"
        double x = center.x - scale*image.getWidth()/2;
        double y = center.y - scale*image.getHeight()/2;
        origin.setLocation(x, y);
        at.setToTranslation(x, y);
        at.scale(scale, scale);
    public static void main(String[] args) throws java.io.IOException {
        java.net.URL url = ZD.class.getResource("images/hawk.jpg");
        BufferedImage image = javax.imageio.ImageIO.read(url);
        ZD test = new ZD(image);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(test);
        f.setSize(500,500);
        f.setLocation(100,100);
        f.setVisible(true);
        test.addMouseListener(test.mia);
        test.addMouseMotionListener(test.mia);
    /** MouseAdapter okay in j2se 1.6+ */
    private MouseInputAdapter mia = new MouseInputAdapter() {
        final double SCALE_INC = 0.05;
        final int SCALE_STEP = 20;
        double scale = 1.0;
        double lastStep;
        public void mousePressed(MouseEvent e) {
            Point p = e.getPoint();
            center.setLocation(p);
            //System.out.printf("center = [%3d, %3d]%n", p.x, p.y);
            setTransform(scale);
            repaint();
        public void mouseDragged(MouseEvent e) {
            // scale up/down with relative vertical motion
            int step = (e.getY() - center.y)/SCALE_STEP;
            if(step != lastStep) {
                scale += SCALE_INC*((step < lastStep) ? -1 : 1);
                //System.out.printf("step = %3d  scale = %.3f%n", step, scale);
                setTransform(scale);
                lastStep = step;
                repaint();
}