How to set repeating background image to a JPanel?

Question

I want to set an image which repeats throughout the full width of the JPanel like we apply Background image to a DIV in CSS. How do I obtain that in swing for a JPanel?

Answer 1

Swing doesn't provide this functionality out of the box, so you will need to do it yourself...

The overall process is relative simple,

for (y = 0 to containerHeight) do
    for (x = 0 to containerWidth) do
        drawImage(tile, x, y)

The fun part is knowing where and how to apply it. Take a look at:

• Performing Custom Painting
• 2D Graphics
• Reading/Loading an Image

For details about the various parts you will need to know.

Example

So using this as the tile...

I was able to produce this...

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class PaintTitle {

    public static void main(String[] args) {
        new PaintTitle();
    }

    public PaintTitle() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private BufferedImage tile;

        public TestPane() {
            try {
                tile = ImageIO.read(getClass().getResource("/tile.jpg"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            int tileWidth = tile.getWidth();
            int tileHeight = tile.getHeight();
            for (int y = 0; y < getHeight(); y += tileHeight) {
                for (int x = 0; x < getWidth(); x += tileWidth) {
                    g2d.drawImage(tile, x, y, this);
                }
            }
            g2d.dispose();
        }
    }

}