java swing background image

Question

I am using JFrame and I have kept a background image on my frame. Now the problem is that the size of image is smaller then the size of the frame so i have to keep the same image once again on the empty part of the window. If user clicks maximize button than I may have to put the image on empty region of the frame at run time. Can anyone tell me how to accomplish this?

Answer 1

You want something like the background image of the windows desktop, when using the background image multiple times instead of resizing it or just display it centered?

You only have to keep the image once and just paint it multiple times in the paintComponent method.

Answer 2

It sounds as though you are talking about tiling vs. stretching, though it's not clear which behaviour you want.

This program has examples of both:

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.io.IOException;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.swing.AbstractAction;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main {
    public static void main(String[] args) throws IOException {
        final Image image = ImageIO.read(new URL("http://sstatic.net/so/img/logo.png"));
        final JFrame frame = new JFrame();
        frame.add(new ImagePanel(image));
        frame.setSize(800, 600);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

@SuppressWarnings("serial")
class ImagePanel extends JPanel {
    private Image image;
    private boolean tile;

    ImagePanel(Image image) {
        this.image = image;
        this.tile = false;
        final JCheckBox checkBox = new JCheckBox();
        checkBox.setAction(new AbstractAction("Tile") {
            public void actionPerformed(ActionEvent e) {
                tile = checkBox.isSelected();
                repaint();
            }
        });
        add(checkBox, BorderLayout.SOUTH);
    };

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (tile) {
            int iw = image.getWidth(this);
            int ih = image.getHeight(this);
            if (iw > 0 && ih > 0) {
                for (int x = 0; x < getWidth(); x += iw) {
                    for (int y = 0; y < getHeight(); y += ih) {
                        g.drawImage(image, x, y, iw, ih, this);
                    }
                }
            }
        } else {
            g.drawImage(image, 0, 0, getWidth(), getHeight(), this);
        }
    }
}