Problem with jpanel zooming

Question

friends,
i have a jpanel with image as background and i am adding jlabels dynamically to the jpanel. i have to move the jlabel on the image so i added mouse listener to jlabel. now i want to add zooming functionality to the jpanel.
now if zoom out jpanel everything works well but jlabel mouse listener location is not changing so if i click on jlabel its not activating listener - i need to click outside of jlabel/jpanel (its original location when its 100% zoom) to activate the listener. how can i correct this ?
thanks in advance
i will add example after i cutdown (its part of big application)

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.net.*;
import java.util.ArrayList;
import java.util.List;
import javax.imageio.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
public class PP3 extends JFrame {
    private JButton btnStart;
    private JButton btnStop;
    private JLabel logoLabel;
    private JSlider zoom;
    private JPanel mainPanel;
    private JPanel btnPanel;
    private JScrollPane jspane;
    private BackPanel3 secondPanel;
    private boolean start = false;
    public PP3() {
        initComponents();
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    private void initComponents() {
        logoLabel = new JLabel();
        mainPanel = new JPanel();
        btnPanel = new JPanel();
        btnStart = new JButton();
        btnStop = new JButton();
        zoom = new JSlider(0,100,100);
        setBackground(Color.white);
        setLayout(new BorderLayout());
        mainPanel.setBackground(Color.white);
        mainPanel.setBorder(new EtchedBorder());
        mainPanel.setPreferredSize(new Dimension(650, 600));
        mainPanel.setLayout(new CardLayout());
        jspane = new JScrollPane(getSecondPanel());
        mainPanel.add(jspane,"Second Panel");
        add(mainPanel, BorderLayout.CENTER);
        btnPanel.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2,2,2,2);
        gbc.weighty = 1.0;
        gbc.gridwidth = gbc.REMAINDER;
        btnPanel.setBackground(Color.white);
        btnPanel.setBorder(new EtchedBorder());
        btnPanel.setPreferredSize(new Dimension(150, 600));
        btnStart.setText("Start Labelling");
        btnPanel.add(btnStart, gbc);
        btnStart.setEnabled(true);
        btnStart.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent ae){
                start = true;
                btnStart.setEnabled(false);
                btnStop.setEnabled(true);
                if(secondPanel != null){
                    secondPanel.setStart(start);
                    Cursor moveCursor = new Cursor(Cursor.TEXT_CURSOR);
                    secondPanel.setCursor(moveCursor);
        btnStop.setText("Done Labelling");
        btnPanel.add(btnStop, gbc);
        btnStop.setEnabled(false);
        btnStop.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent ae){
                start = false;
                btnStart.setEnabled(true);
                btnStop.setEnabled(false);
                if(secondPanel != null){
                    secondPanel.setStart(start);
                    Cursor moveCursor = new Cursor(Cursor.DEFAULT_CURSOR);
                    secondPanel.setCursor(moveCursor);
        final JLabel zoomLabel = new JLabel("Zoom");
        zoomLabel.setBorder(BorderFactory.createEtchedBorder());
        gbc.weighty = 0;
        gbc.weightx = 1.0;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        btnPanel.add(zoomLabel, gbc);
        btnPanel.add(zoom, gbc);
        zoom.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent ce) {
                JSlider source = (JSlider)ce.getSource();
                if(secondPanel != null) {
                    secondPanel.setZoomFactor((double)source.getValue());
                    zoomLabel.setText("Zoom = " + source.getValue()/100.0);
        String id = "<html><nobr>show label</nobr><br><center>locations";
        JCheckBox check = new JCheckBox(id, secondPanel.showLocations);
        check.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                secondPanel.toggleShowLocations();
        gbc.weighty = 1.0;
        gbc.fill = GridBagConstraints.NONE;
        btnPanel.add(check, gbc);
        add(btnPanel, BorderLayout.EAST);
        pack();
    public JPanel getSecondPanel() {
        if(secondPanel == null) {
            secondPanel = new BackPanel3("images/cougar.jpg", 850, 1100);
            secondPanel.setStart(false);
        return secondPanel;
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new PP3();
class BackPanel3 extends JPanel implements MouseListener,
                                           MouseMotionListener{
    String imgPath = null;
    BufferedImage image;
    private int width = 0;
    private int height = 0;
    private double zoomFactor = 1.0;
    private boolean start = false;
    private boolean same = false;
    Cursor hourglassCursor = new Cursor(Cursor.MOVE_CURSOR);
    // choose a declaration according to your java version
    List<JLabel> labels;     // declaration for j2se 1.5+
//    List labels;           // j2se 1.4-
    JLabel lastSelected;
    boolean showLocations;
    JLabel selectedLabel;
    boolean dragging;
    Point offset;
    int count = 0;
    private static String SELECTED = "selected";
    public BackPanel3(String path, int width, int height){
        setLayout(null);
        this.width = width;
        this.height = height;
        setPreferredSize(new Dimension(width,height));
        addMouseListener(this);
        addMouseMotionListener(this);
        // chose an instantiation according to your java version
        labels = new ArrayList<JLabel>();    // j2se 1.5+
//        labels = new ArrayList();          // j2se 1.4-
        lastSelected = new JLabel();
        lastSelected.putClientProperty(SELECTED, Boolean.FALSE);
        showLocations = true;
        dragging = false;
        offset = new Point();
        this.imgPath = path;
        setImage();
    public void setImage(){
        try{
            image = getImage(imgPath);
        }catch(Exception e){
            System.out.println(" (init) ERROR: " + e);
            e.printStackTrace();
    public void setStart(boolean flag){
        start = flag;
    public void setZoomFactor(double zoom){
        zoomFactor = (zoom/100);
        setPreferredSize(new Dimension((int)(850*zoomFactor), (int)(1100*zoomFactor)));
        repaint();
        revalidate();
    public double getZoomFactor(){
        return zoomFactor;
    public void toggleShowLocations() {
        showLocations = !showLocations;
        repaint();
    public void mouseClicked(MouseEvent e) {
        if(start){
            JLabel msgLabel = new JLabel("Test " + count++);
            this.add(msgLabel);
            Dimension d = msgLabel.getPreferredSize();
            msgLabel.setBounds(e.getX(), e.getY(), d.width, d.height);
            labels.add(msgLabel);
            msgLabel.putClientProperty(SELECTED, Boolean.FALSE);
            return;
    public void mousePressed(MouseEvent e) {
        Point p = e.getPoint();
        for(int j = 0; j < labels.size(); j++) {
            JLabel label = (JLabel)labels.get(j);
            Rectangle bounds = label.getBounds();
            AffineTransform at =
                AffineTransform.getScaleInstance(zoomFactor, zoomFactor);
            Shape xs = at.createTransformedShape(bounds);
            if(xs.contains(p)) {
                selectedLabel = label;
                Rectangle r = xs.getBounds();
                offset.x = p.x - r.x;
                offset.y = p.y - r.y;
                dragging = true;
                break;
    public void mouseReleased(MouseEvent e) {
        dragging = false;
    public void mouseDragged(MouseEvent me){
        if(dragging) {
            Rectangle bounds = selectedLabel.getBounds();
            AffineTransform at =
                AffineTransform.getScaleInstance(1.0/zoomFactor, 1.0/zoomFactor);
            Point2D p = at.transform(me.getPoint(), null);
            int x = (int)(p.getX() - offset.x);
            int y = (int)(p.getY() - offset.y);
            selectedLabel.setLocation(x, y);
            repaint();
    public void mouseMoved(MouseEvent me){
        if(labels.size() == 0)
            return;
        Point p = me.getPoint();
        boolean hovering = false;
        boolean selectionChanged = false;
        for(int j = 0; j < labels.size(); j++) {
            final JLabel label = (JLabel)labels.get(j);
            Rectangle r = label.getBounds();
            AffineTransform at =
                AffineTransform.getScaleInstance(zoomFactor, zoomFactor);
            Shape scaledBounds = at.createTransformedShape(r);
            if(scaledBounds.contains(p)) {
                hovering = true;
                if(!((Boolean)label.getClientProperty(SELECTED)).booleanValue()) {
                    label.putClientProperty("selected", Boolean.TRUE);
                    setCursor(hourglassCursor);
                    if(lastSelected != label)  // for only one JLabel
                        lastSelected.putClientProperty(SELECTED, Boolean.FALSE);
                    lastSelected = label;
                    selectionChanged = true;
                    break;
        // reset lastSelected when there is no selection/hovering
        if(!hovering &&
            ((Boolean)lastSelected.getClientProperty(SELECTED)).booleanValue()) {
            lastSelected.putClientProperty(SELECTED, Boolean.FALSE);
            setCursor(Cursor.getDefaultCursor());
            selectionChanged = true;
        if(selectionChanged)
            repaint();
    public void mouseEntered(MouseEvent e) { }
    public void mouseExited(MouseEvent e) { }
    protected void paintComponent(Graphics g){
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.scale(zoomFactor, zoomFactor);
        g2.drawImage(image, 0, 0, this);
        if(showLocations) {
            // show bounds of the actual JLabel children
            // components as they exist on this component
            AffineTransform at = AffineTransform.getScaleInstance(1.0/zoomFactor,
                                                                  1.0/zoomFactor);
            g2.setPaint(Color.blue);
            Component[] c = getComponents();
            for(int j = 0; j < c.length; j++)
                g2.draw(at.createTransformedShape(c[j].getBounds()));
        // show selected label
        g2.setPaint(Color.red);
        for(int j = 0; j < labels.size(); j++) {
            JLabel label = (JLabel)labels.get(j);
            if(((Boolean)label.getClientProperty("selected")).booleanValue()) {
                g2.draw(label.getBounds());
                break;
    protected BufferedImage getImage(String path){
        try{
            URL imgURL = BackPanel3.class.getResource(path);
            if (imgURL == null &&
                   (path.indexOf(":\\") > 0 || path.indexOf(":/") > 0))
                imgURL = new URL("file:///"+path);
            return getImage(imgURL);
        }catch(MalformedURLException mue){
            System.out.println("error "+mue);
        return null;
    protected BufferedImage getImage(URL url){
        try{
            if (url != null) {
                BufferedImage source = ImageIO.read(url);
                double xScale = (double)width / source.getWidth();
                double yScale = (double)height / source.getHeight();
                double scale = Math.min(xScale, yScale);
                int w = (int)(scale*source.getWidth());
                int h = (int)(scale*source.getHeight());
                BufferedImage scaled = new BufferedImage(w, h, source.getType());
                Graphics2D g2 = scaled.createGraphics();
                g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
                                    RenderingHints.VALUE_INTERPOLATION_BICUBIC);
                // scales faster than getScaledInstance
                AffineTransform at = AffineTransform.getScaleInstance(scale, scale);
                g2.drawRenderedImage(source, at);
                g2.dispose();
                return scaled;
            }else{
                return null;
        }catch(IOException ioe){
            System.out.println("read error "+ioe);
            return null;
}