Adjust image opacity with createImage in Java

Is it possible to adjust the alpha of an image when drawing it to a canvas like so?

public void drawImg(Graphics g) {
    g.开发者_如何学CdrawImage(img, 0, 0, null);
}

"img" is an Image object declared to a local file. If this is not possible, is it possible to change the alpha of "img" without actually altering the source file? Thanks ahead of time.

This is a easy and short most developers using java code for image fade.

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.awt.image.RescaleOp;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;

/**
 *
 * @author ADMIN
 */
public class ImageFade extends JFrame {

    ImageFade() {
        setLayout(null);

        JLabel l = new JLabel();
        l.setBounds(0, 0, 100, 96);
        add(l);

        Thread tp = new Thread() {
            @Override
            public void run() {
                for (int amp = 0; amp <= 500; amp++) {
                    try {
                        sleep(1);
                        try {
                            BufferedImage bim = ImageIO.read(new File("src/image/fade/image.png"));
                            BufferedImage nbim = new BufferedImage(bim.getWidth(), bim.getHeight(), BufferedImage.TYPE_INT_ARGB);
                            Graphics2D createGraphics = nbim.createGraphics();
                            createGraphics.drawImage(bim, null, 0, 0);
                            RescaleOp r = new RescaleOp(new float[]{1f, 1f, 1f, (float) amp / 500}, new float[]{0, 0, 0, 0}, null);
                            BufferedImage filter = r.filter(nbim, null);
                            l.setIcon(new ImageIcon(filter));
                        } catch (Exception ex) {
                            System.err.println(ex);
                        }
                    } catch (InterruptedException ex) {
                    }
                }
            }
        };
        tp.start();

        setUndecorated(true);
        setBackground(new Color(0, 0, 0, 0));
        setSize(100, 96);
        setVisible(true);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setResizable(false);
        setAlwaysOnTop(true);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        ImageFade fr = new ImageFade();
    }
}

in this code you can see a thread code. in the thread this image will fade in.

the used image is stack overflow web page's logo image.

only by shown code the image will fade in.

Thread tp = new Thread() {
    @Override
    public void run() {
        for (int amp = 0; amp <= 500; amp++) {
            try {
                sleep(1);
                try {
                    BufferedImage bim = ImageIO.read(new File("src/image/fade/image.png"));
                    BufferedImage nbim = new BufferedImage(bim.getWidth(), bim.getHeight(), BufferedImage.TYPE_INT_ARGB);
                    Graphics2D createGraphics = nbim.createGraphics();
                    createGraphics.drawImage(bim, null, 0, 0);
                    RescaleOp r = new RescaleOp(new float[]{1f, 1f, 1f, (float) amp / 500}, new float[]{0, 0, 0, 0}, null);
                    BufferedImage filter = r.filter(nbim, null);
                    l.setIcon(new ImageIcon(filter));
                } catch (Exception ex) {
                      System.err.println(ex);
                  }
            } catch (InterruptedException ex) {
            }
        }
    }
};
tp.start();

This code is very simple to use.

This is not from any book, internet or etc. It is developed by me.

A normal image is not able to change alpha. By code : BufferedImage nbim = new BufferedImage(bim.getWidth(), bim.getHeight(), BufferedImage.TYPE_INT_ARGB); the image will convert to ARGB - Alpha, Red, Green, Blue (R,G,B,A) image.

So you can change the alpha of a image.

If your image already has alpha data associated with it, you should just be able to draw it directly. You may have to do a setOpaque(true) for the object that you are drawing so that the alpha will show up properly.(this will only work for Swing components, you shouldn't be using the Canvas from AWT unless you absolutely have to).

You can also modify the image in-memory, as long as you don't write the image back to disk it won't be permanently changed. If you're loading the image through ImageIO.read() you get back a BufferedImage, which you can modify as much as you want.