// show a graphic on top of your xwindows display (full-screen) from a PNG file
// by misan, September 2017

import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
import java.util.*;
import java.io.*;
import javax.imageio.*;
import java.awt.image.BufferedImage;

public class FullscreenTest {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setSize(dim);
        frame.setUndecorated(true);
        frame.add(new ImagePanel());
        frame.setVisible(true);
    }
}

class ImagePanel extends JPanel{

    private BufferedImage image;

    public ImagePanel() {
       try {
          image = ImageIO.read(new File("cernicalo2.png"));
       } catch (IOException ex) {
            // handle exception...
       }
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, this); // see javadoc for more info on the parameters
    }

}