java - How to display an image in a frame?

Question

I am coding a gui and I wanted to use embedde some pictures, but before embedding it in my main program I wrote that code to test it:

    public class guikopie extends javax.swing.JFrame{
        public guikopie() {
            a = new javax.swing.JLabel();
            setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
            a.setIcon(new javax.swing.ImageIcon("C:\Users\Public\Pictures\Sample Pictures\Tulpen.jpg"));       
            add(a);//here i add it to the jlabel
            pack();
        }

        public static void main(String args[]){
            java.awt.EventQueue.invokeLater(new Runnable() {
                public void run() {
                    new guikopie().setVisible(true);
                }
            });
        }

        private javax.swing.JLabel a;
    }

My question is: Why does this code do not display the picture?

Answer 1

I think people may hate me for repeating this :P:

• Dont extend JFrame class
• Class names begin with captial letter i.e Guikopie

Also depending on what the background is being used for i.e if its a logo that will be added to a specific location on the JPanel then using a JLabel is fine, however, if its being used as a background it is not; because it will moved around as more components are being added, thus we should not add the background as a component rather we paint the background on the component.

As for your question:

My question is: Why does this code do not display the picture?

your code works perfect for me thus the location of your picture must be incorrect.

I did a short example showing how to add a Image to JPanel background and then add JPanel to JFrame, it also includes class ImgUtils for resizing picture:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class JFrameWithPicture {

    public JFrameWithPicture() throws MalformedURLException, IOException {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    new JFrameWithPicture();
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    private void initComponents() throws MalformedURLException, IOException {
        JFrame frame = new JFrame("Frame with JPanel and background");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        final Image background = ImageUtils.scaleImage(300, 300, ImageIO.read(new URL("http://images2.layoutsparks.com/1/98191/naruto-14-red-design.jpg")));
        final Dimension jpanelDimensions = new Dimension(new ImageIcon(background).getIconWidth(), new ImageIcon(background).getIconHeight());

        frame.add(new JPanel() {
            @Override
            protected void paintComponent(Graphics grphcs) {
                super.paintComponent(grphcs);
                grphcs.drawImage(background, 0, 0, this);
            }

            @Override
            public Dimension getPreferredSize() {
                return jpanelDimensions;
            }
        });

        frame.setResizable(false);
        frame.pack();
        frame.setVisible(true);
    }
}

class ImageUtils {

    public static BufferedImage scaleImage(int width, int height, String filename) {
        BufferedImage bi;
        try {
            ImageIcon ii = new ImageIcon(filename);
            bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            Graphics2D g2d = (Graphics2D) bi.createGraphics();
            g2d.addRenderingHints(new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY));
            g2d.drawImage(ii.getImage(), 0, 0, width, height, null);
        } catch (Exception e) {
            return null;
        }
        return bi;
    }

    static Image scaleImage(int width, int height, BufferedImage filename) {
        BufferedImage bi;
        try {
            bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            Graphics2D g2d = (Graphics2D) bi.createGraphics();
            g2d.addRenderingHints(new RenderingHints(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY));
            g2d.drawImage(filename, 0, 0, width, height, null);
        } catch (Exception e) {
            return null;
        }
        return bi;
    }
}

Alternatively you may want to resize using Image#getScaledInstance(int width,int height,int hints), but this has its perils, the main problem being:

Image.getScaledInstance() does not return a finished, scaled image. It leaves much of the scaling work for a later time when the image pixels are used.