You should use the javax.imageio.ImageIO Class :

ImageIO.write( myImage, theImageFormat, theOutputStream);

myImage should be a BufferedImage,

theImageFormat should be "JPG" or "PNG",

theOutputStream sould be an OutputStream.



an example :

// read an image form myImage.png file
BufferedImage bufImg = new IconImage(myImage.png).getImage;
// prepare an output stream to newImage.png file
OutputStream out = new FileOutputStream(new File(newImage.png));
// write the image to the new file
ImageIO.write(bufImg, "PNG", out);