How to have 2DGraphics zoom into a specific part of an image?

Question

I am trying to mess around with2DGraphics and affinetramsform to zoom into a section of an image but i have no luck doing it. Can someone help me out? Lets say I want to zoom into the coordinates (200,300) and (400,600) . I know DrawImage has a method that does this but does 2DGraphics have it too or affinetransform? I havent see anything like it yet. thanks

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;
public class ZoomIt extends JPanel {
    BufferedImage image;
    Dimension size;
    Rectangle clip;
    AffineTransform at = new AffineTransform();
    public ZoomIt(BufferedImage image) {
        this.image = image;
        size = new Dimension(image.getWidth(), image.getHeight());
        clip = new Rectangle(100,100,200,200);
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        g2.drawRenderedImage(image, at);
        g2.setColor(Color.red);
        g2.draw(clip);
        //g2.setPaint(Color.blue);
        //g2.draw(at.createTransformedShape(clip));
    public Dimension getPreferredSize() {
        return size;
    private void zoomToClip() {
        // Viewport size.
        Dimension viewSize = ((JViewport)getParent()).getExtentSize();
        // Component dimensions.
        int w = getWidth();
        int h = getHeight();
        // Scale the clip to fit the viewport.
        double xScale = (double)viewSize.width/clip.width;
        double yScale = (double)viewSize.height/clip.height;
        double scale = Math.min(xScale, yScale);
        at.setToScale(scale, scale);
        size.width = (int)(scale*size.width);
        size.height = (int)(scale*size.height);
        revalidate();
    private void reset() {
        at.setToIdentity();
        size.setSize(image.getWidth(), image.getHeight());
        revalidate();
    private JPanel getControlPanel() {
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.weightx = 1.0;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        panel.add(getZoomControls(), gbc);
        panel.add(getClipControls(), gbc);
        return panel;
    private JPanel getZoomControls() {
        final JButton zoom = new JButton("zoom");
        final JButton reset = new JButton("reset");
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JButton button = (JButton)e.getSource();
                if(button == zoom)
                    zoomToClip();
                if(button == reset)
                    reset();
                repaint();
        zoom.addActionListener(al);
        reset.addActionListener(al);
        JPanel panel = new JPanel();
        panel.add(zoom);
        panel.add(reset);
        return panel;
    private JPanel getClipControls() {
        int w = size.width;
        int h = size.height;
        SpinnerNumberModel xModel = new SpinnerNumberModel(100, 0, w/2, 1);
        final JSpinner xSpinner = new JSpinner(xModel);
        SpinnerNumberModel yModel = new SpinnerNumberModel(100, 0, h/2, 1);
        final JSpinner ySpinner = new JSpinner(yModel);
        SpinnerNumberModel wModel = new SpinnerNumberModel(200, 0, w, 1);
        final JSpinner wSpinner = new JSpinner(wModel);
        SpinnerNumberModel hModel = new SpinnerNumberModel(200, 0, h, 1);
        final JSpinner hSpinner = new JSpinner(hModel);
        ChangeListener cl = new ChangeListener() {
            public void stateChanged(ChangeEvent e) {
                JSpinner spinner = (JSpinner)e.getSource();
                int value = ((Integer)spinner.getValue()).intValue();
                if(spinner == xSpinner)
                    clip.x = value;
                if(spinner == ySpinner)
                    clip.y = value;
                if(spinner == wSpinner)
                    clip.width = value;
                if(spinner == hSpinner)
                    clip.height = value;
                repaint();
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2,2,2,2);
        gbc.weightx = 1.0;
        addComponents(new JLabel("x"),      xSpinner, panel, gbc, cl);
        addComponents(new JLabel("y"),      ySpinner, panel, gbc, cl);
        addComponents(new JLabel("width"),  wSpinner, panel, gbc, cl);
        addComponents(new JLabel("height"), hSpinner, panel, gbc, cl);
        return panel;
    private void addComponents(Component c1, JSpinner s, Container c,
                               GridBagConstraints gbc, ChangeListener cl) {
        gbc.anchor = GridBagConstraints.EAST;
        c.add(c1, gbc);
        gbc.anchor = GridBagConstraints.WEST;
        c.add(s, gbc);
        s.addChangeListener(cl);
    public static void main(String[] args) throws IOException {
        String path = "images/owls.jpg";
        BufferedImage image = ImageIO.read(new File(path));
        ZoomIt test = new ZoomIt(image);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(test));
        f.getContentPane().add(test.getControlPanel(), "Last");
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
}