How to Display a BufferedImage in a JFrame in Java?

Question

What are the steps to display a BufferedImage in a JFrame using Java?

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;

public class ImageDisplay extends JPanel {
    private BufferedImage image;

    public ImageDisplay(BufferedImage img) {
        this.image = img;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, null);
    }

    public static void main(String[] args) throws Exception {
        BufferedImage img = new BufferedImage(400, 400, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = img.createGraphics();
        g2d.setColor(Color.BLUE);
        g2d.fillRect(0, 0, img.getWidth(), img.getHeight());

        JFrame frame = new JFrame();
        ImageDisplay panel = new ImageDisplay(img);
        frame.add(panel);
        frame.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer

Displaying a BufferedImage in a JFrame allows developers to show images dynamically in Java applications. Below are the steps required to achieve this.

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;

public class ImageDisplay extends JPanel {
    private BufferedImage image;

    public ImageDisplay(BufferedImage img) {
        this.image = img;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, null);
    }

    public static void main(String[] args) throws Exception {
        BufferedImage img = new BufferedImage(400, 400, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = img.createGraphics();
        g2d.setColor(Color.BLUE);
        g2d.fillRect(0, 0, img.getWidth(), img.getHeight());

        JFrame frame = new JFrame();
        ImageDisplay panel = new ImageDisplay(img);
        frame.add(panel);
        frame.setSize(400, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Causes

BufferedImage is not directly renderable in a JFrame.
You need to draw BufferedImage on a component's Graphics context.

Solutions

Create a subclass of JPanel to handle the painting of the image.
Override the paintComponent method to draw the BufferedImage on the panel.
Add the JPanel to a JFrame, set the size, and make it visible.

Common Mistakes

Mistake: Not overriding paintComponent method.

Solution: Always override the paintComponent(Graphics g) method when working with custom painting.

Mistake: Forgetting to dispose of the BufferedImage.

Solution: Make sure to dispose the Graphics object when you're done with it to free resources.

Mistake: Not setting JFrame visibility before adding components.

Solution: Set the JFrame as visible after adding all components and setting its size.

Helpers

BufferedImage
JFrame
Java
display image in Java
Java Swing