How do I save user drawn graphics to a jpeg? (This code doesn't work).

Question

As the title says, I have the code that I think should work but cannot see what is wrong with it:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class SavePaint extends JPanel {
    protected JButton saveButton;
    protected JFrame frame;
    protected int firstX, firstY, currentX, currentY, counter;
    protected JPanel mainPanel = this, panel2;
    protected JButton clearButton;
    protected Color background = Color.PINK;
    protected boolean dragged;
    public SavePaint() {
        JFrame frame = new JFrame("TheFrame");
        frame.add(mainPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 400);
        frame.setVisible(true);
        MyMouseListener myMouseListener = new MyMouseListener();
        mainPanel.addMouseListener(myMouseListener);
        mainPanel.addMouseMotionListener(myMouseListener);
    private class MyMouseListener implements MouseListener, MouseMotionListener {
        public void mouseClicked(MouseEvent e) throws UnsupportedOperationException {
            // code
        public void mousePressed(MouseEvent e) throws UnsupportedOperationException {
            firstX = e.getX();
            firstY = e.getY();
            dragged = true;
        public void mouseReleased(MouseEvent e) throws UnsupportedOperationException {
            currentX = e.getX();
            currentY = e.getY();
            dragged = true;
            repaint();
        public void mouseEntered(MouseEvent e) throws UnsupportedOperationException {
            // code
        public void mouseExited(MouseEvent e) throws UnsupportedOperationException {
            try {
                BufferedImage image = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_RGB);
                Graphics2D graphics2D = image.createGraphics();
                mainPanel.paint(graphics2D);
                ImageIO.write(image, "jpeg", new File("/home/deniz/Desktop/jmemPractice.jpeg"));
            } catch (Exception exception) {
                System.out.println("The exception is: " + exception);
        public void mouseDragged(MouseEvent e) throws UnsupportedOperationException {
            currentX = e.getX();
            currentY = e.getY();
            dragged = true;
            repaint();
        public void mouseMoved(MouseEvent e) throws UnsupportedOperationException {
            dragged = false;
    protected void paintComponent(Graphics g) {
        g.drawLine(firstX, firstY, currentX, currentY);
        firstX = currentX;
        firstY = currentY;
    public static void main(String[] args) {
        new SavePaint();
}An observation that I made is that on top of the white background, there is a dot (is this technically one pixel?) which seems to be the endpoint of what the user (in this case - me) has drawn. The frame has a continous flow of dots display as the user makes them with the cursor. Why isn't the jpeg a continuous flow of dots as well?
Any help would be greatly appreciated!
Thanks in advance!

Answer 1

there is a dot (is this technically one pixel?) This shows a problem with your painting logic.
Whenever the panel is repainted, you only have a single line of code, so only a single pixel is ever drawn. The drawing looks like its working because Swing hasn't asked the panel to repaint itself so you see the cummulative effect of all your drawLine(...) method.
However, try drawing a few lines, then minimize the window and then restore the window. You will only see a single pixel. This is exactly what you see when you try to create the jpeg.
You should probably be using the "Draw on Image" approach suggested in [url http://www.camick.com/java/blog.html?name=custom-painting-approaches]Custom Painting Approaches.
Just for interest sake you can also use the ScreenImage class I suggested to you earlier in your other posting (when you didn't bother to accept the answer I provided, so this will be the last time I help if you don't learn to use the forum properly).
ScreenImage.writeImage(ScreenImage.createImage((Component)mainPanel), "mainPanel.jpg");This will force the class to use the Robot to capture the actual pixels on the screen. Using a Robot is slower then using the paint() method.