Java - Image Transparency With Graphics g

Question

I would like to create a fade in and fade out effect for one of the characters in my video game. To do this I would like to have the image of them be fade out and fade back in. I would like to change the opacity of the image but have no idea how. I am using the java Graphics. Here is some code.

g.drawImage(joople, jx, jy, sx, sy, this);

I am running this code in this method:

public void paint(Graphics g) {

Many thanks, Oak

Answer 1

You will want to have a look at Compositing Graphics

import java.awt.AlphaComposite;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class FadeMe {

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

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

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

    public class TestPane extends JPanel {

        private BufferedImage img;
        private float alpha = 0;
        private float delta = 0.01f;

        public TestPane() {
            try {
                img = ImageIO.read(...);
                Timer timer = new Timer(40, new ActionListener(){ 
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        alpha += delta;
                        if (alpha > 1.0) {
                            alpha = 1.0f;
                            delta *= -1.0f;
                        } else if (alpha < 0.0) {
                            alpha = 0.0f;
                            delta *= -1.0f;
                        }
                        repaint();
                    }
                });
                timer.start();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return img != null ? new Dimension(img.getWidth(), img.getHeight()) : new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setComposite(AlphaComposite.SrcOver.derive(alpha));
            int x = (getWidth() - img.getWidth()) / 2;
            int y = (getHeight() - img.getHeight()) / 2;
            g2d.drawImage(img, x, y, this);
            g2d.dispose();
        }

    }

}