Create an image of a JLayeredPane 's content

Question

hi there,
we have a problem here: we'd like to create one image out of a JLayeredPane`s content. but the only thing we get is a gray box which size is the size of the JLayeredPane.
the purpose is: we're developing a graphic tool where you can draw and arrange objects in the JLayeredPane(which is in a JScrollPane). and now we're implementing the print-function which allows to print the graphs over several pages, therefore it is neccessary to have an image(*.jpeg) for our printpreview-window. the preview-window and the printfuntion are nearly implemented and the only problem is that we cant make an image of the JLayerdPane's content.
maybe you have an idea or codesamples...
thanks a lot in advance!!
george

Answer 1

1. Getting any JComponent to render onto a buffered image isn't a problem -- just call paint, passing it a graphics object backed by that buffered image.
2. Writing an image to a file isn't a problem: use javax.imageio.ImageIO.
Some code:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;
import javax.swing.*;
import javax.swing.border.*;
public class Ex {
    public static void main(String[] args) {
        JFrame f = new JFrame("Ex");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final JLayeredPane pane = new JLayeredPane();
        Border b = BorderFactory.createEtchedBorder();
        pane.add(createLabel("DEFAULT_LAYER", b, 00, 10), JLayeredPane.DEFAULT_LAYER);
        pane.add(createLabel("PALETTE_LAYER", b, 40, 20), JLayeredPane.PALETTE_LAYER);
        pane.add(createLabel("MODAL_LAYER", b, 80, 30), JLayeredPane.MODAL_LAYER);
        pane.add(createLabel("POPUP_LAYER", b, 120, 40), JLayeredPane.POPUP_LAYER);
        pane.add(createLabel("DRAG_LAYER", b, 160, 50), JLayeredPane.DRAG_LAYER);
        f.getContentPane().add(pane);
        JPanel south = new JPanel();
        JButton btn = new JButton("save");
        btn.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent evt) {
                save(pane);
        south.add(btn);
        f.getContentPane().add(south, BorderLayout.SOUTH);
        f.setSize(400,300);
        f.show();
    static JLabel createLabel(String text, Border b, int x, int y) {
        JLabel label = new JLabel(text);
        label.setOpaque(true);
        label.setBackground(Color.WHITE);
        label.setBorder(b);
        label.setBounds(x,y, 100,20);
        return label;
    static void save(JComponent comp) {
        int w = comp.getWidth(), h = comp.getHeight();
        BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = image.createGraphics();
        g2.setPaint(Color.MAGENTA);
        g2.fillRect(0,0,w,h);
        comp.paint(g2);
        g2.dispose();
        try {
            ImageIO.write(image, "jpeg", new File("image.jpeg"));
        } catch(IOException e) {
            e.printStackTrace();
}Why does the saved image have a magenta background? JLayerPane, by default, is non-opaque. You can set it to be opaque and choose its background color, as you like.