Encoding an image to a JPEG file

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Ever run into the problem of wanting to write an image object to disk in a popular format for images ?

With Java 2 platform, image objects or any memory based image representation can be written to disk in the JPEG format. The example shows a simple image created in memory written to disk in the JPEG format. The example makes use of the com.sun.image.codec.jpeg classes to do the encoding. Though it is not a part of the feature set of the Java 2 platform, these classes are still available in the distributed runtime.

Code

/*
 * This example is from javareference.com
 * for more information visit,
 * http://www.javareference.com
 */

import java.awt.*;
import java.awt.image.*;

import java.io.*;
import com.sun.image.codec.jpeg.*;

/*
 * This class can take a variable number of parameters on the command 
 * line. Program execution begins with the main() method. The class 
 * constructor is not invoked unless an object of type 'Class1' 
 * created in the main() method.  
 *
 * @author Anand Hariharan(anand@javareference.com) 
 */
public class EncodeJPEG
{
    public static void encode(Image img,int x, int y, int w, int h,
                              String absoluteFileName) throws Exception
    {
        int[] pixels = new int[w * h];
        PixelGrabber pg = new PixelGrabber(img, x, y, w, h, pixels, 0, w);

        try
        {
            pg.grabPixels();
        }
        catch (InterruptedException e)
        {
            System.err.println("interrupted waiting for pixels!");
            return;
        }
        if ((pg.getStatus() & ImageObserver.ABORT) != 0)
        {
            System.err.println("image fetch aborted or errored");
            return;
        }

        BufferedImage bimg = new BufferedImage(w,h,BufferedImage.TYPE_INT_RGB);

        for (int j = 0; j < h; j++)
        {
            for (int i = 0; i < w; i++)
            {
                bimg.setRGB(x+i, y+j, pixels[j * w + i]);
            }
        }

        FileOutputStream fout = new FileOutputStream(absoluteFileName);

        JPEGImageEncoder jencoder = JPEGCodec.createJPEGEncoder(fout);
        JPEGEncodeParam enParam = jencoder.getDefaultJPEGEncodeParam(bimg);

        enParam.setQuality(1.0F, true);
        jencoder.setJPEGEncodeParam(enParam);
        jencoder.encode(bimg);

        fout.close();
    }

    public static void main(String [] args) throws Exception
    {
        Frame f = new Frame();
        f.addNotify();

        // CREATE an image in memory to draw on 
        Image img = f.createImage(100,100);

        Graphics g = img.getGraphics();
        g.setColor(Color.red);
        // Draw whatever is needed. 
        g.fillRect(0, 0, 100,100);
        g.setColor(Color.black);
        g.setFont(new Font("Arial", Font.BOLD, 14));
        g.drawString("Hello from,",10,25);
        g.drawString("Java",30,55);
        g.drawString("Reference",10,80);

        g.setColor(Color.white);
        g.drawString("Hello from,",8,22);
        g.drawString("Java",28,52);
        g.drawString("Reference",8,77);

        // Encode into a JPEG 
        String homeDir = System.getProperty("user.home");
        System.out.println("Output JPEG ..." + homeDir + File.separator + "jpg.jpg");
        encode(img,0,0,100,100, homeDir + File.separator + "jpg.jpg");
        f.removeNotify();
        f.dispose();
        System.exit(0);
    }
}

Demonstration

Following JPEG image is created using above java code.

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