Sadly, this is not true....

I used the following test program:

import java.awt.image.BufferedImage; import java.io.File;

import javax.imageio.ImageIO;

import junit.framework.TestCase;

public class TestWriteImage extends TestCase { public static void main(String[] args) throws Exception { BufferedImage img = ImageIO.read(new File("painting.jpg")); for(int i=0;i<20;i++) { ImageIO.write(img,"jpeg",new File("painting0.jpg")); img = ImageIO.read(new File("painting.jpg")); } } }

The resulting 'painting0.jpg' image is all black...

BUT, if you use JPEG2000, you can set the "bit rate", so that repeated compressions result in the same size/quality file...

Using the following code:

import java.awt.image.BufferedImage; import java.io.File;

import javax.imageio.*; import javax.imageio.stream.ImageOutputStream;

import com.sun.media.imageio.plugins.jpeg2000.J2KImageWriteParam;

import junit.framework.TestCase;

public class TestWriteImage extends TestCase { public static void main(String[] args) throws Exception { BufferedImage img = ImageIO.read(new File("painting.jpg")); File f0 = new File("painting0.jpg"); for(int i=0;i<20;i++) { System.out.println("invocation "+i); J2KImageWriteParam p = new J2KImageWriteParam(); p.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); p.setEncodingRate(.5); f0.delete(); ImageWriter w = ImageIO.getImageWritersByFormatName ("jpeg2000").next(); ImageOutputStream ios =ImageIO.createImageOutputStream(f0); w.setOutput(ios); w.write(null,new IIOImage(img,null,null),p); w.dispose(); ios.close(); img = ImageIO.read(f0); } } }

At some point the On Nov 7, 2007, at 9:57 AM, robert engels wrote: