Java Swing How to - Maximize image size as the size of the JPanel








Question

We would like to know how to maximize image size as the size of the JPanel.

Answer

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Image;
import java.awt.LayoutManager;
import java.net.URL;
/*  w ww  .j a va2  s  . co m*/
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Main {
  public static void main(String[] args) throws Exception {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    URL url = new URL("http://www.java2s.com/style/download.png");
    Image image = ImageIO.read(url);

    ImagePanel ip = new ImagePanel(new GridLayout(4, 4, 20, 20));
    ip.setPreferredSize(new Dimension(640, 480));
    f.setContentPane(ip);
    f.pack();
    f.setVisible(true);  
    
    ip.setImage(new ImageIcon(image));
  }
}

class ImagePanel extends JPanel {
  private Image image = null;
  ImagePanel(LayoutManager layout) {
    super(layout);
  }
  public void setImage(ImageIcon icon) {
    image = icon.getImage().getScaledInstance(this.getWidth(),
        this.getHeight(), Image.SCALE_DEFAULT);
    repaint();
  }
  @Override
  public void paintComponent(Graphics g) {
    super.paintComponent(g);
    if (image != null) {
      g.drawImage(image, 0, 0, getWidth(), getHeight(), null); 
    }
  }
}