Help Resizing PNG's and GIF's

Good Morning All,

I'm a CF developer and I've been tasked to come up with a way to
upload images (JPG, PNG and GIF) and resize them while maintaining the
original aspect ratio for the resized image. I was able to find and
modify some sample code that handled the resizing for JPEG's. But, I
have to do this for the other formats as well. Here's the sample code
snippet for JPEG's:

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

public class Thumbnail {
..
..
..

    public myResizeMethod(String inputFile, String outputFile, int
thumbWidth, int thumbHeight, int qualitySpec) throws Exception {
    Image image = Toolkit.getDefaultToolkit().getImage(inputFile);
    MediaTracker mediaTracker = new MediaTracker(new Container());
    mediaTracker.addImage(image, 0);
    mediaTracker.waitForID(0);

    double thumbRatio = (double)thumbWidth / (double)thumbHeight;
    int imageWidth = image.getWidth(null);
    int imageHeight = image.getHeight(null);
    double imageRatio = (double)imageWidth / (double)imageHeight;
    if (thumbRatio < imageRatio) {
      thumbHeight = (int)(thumbWidth / imageRatio);
    } else {
      thumbWidth = (int)(thumbHeight * imageRatio);
    }

    // draw original image to thumbnail image object and
    // scale it to the new size on-the-fly
    BufferedImage thumbImage = new BufferedImage(thumbWidth,
thumbHeight, BufferedImage.TYPE_INT_RGB);
    Graphics2D graphics2D = thumbImage.createGraphics();
    graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
 
RenderingHints.VALUE_INTERPOLATION_BICUBIC);
    graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);

    // save thumbnail image to OUTFILE
    BufferedOutputStream out = new BufferedOutputStream(new
FileOutputStream(outputFile));
    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
    JPEGEncodeParam param =
encoder.getDefaultJPEGEncodeParam(thumbImage);

    int quality = Math.max(0, Math.min(qualitySpec, 100));
    param.setQuality((float)quality / 100.0f, false);
    encoder.setJPEGEncodeParam(param);
    encoder.encode(thumbImage);
    out.close();
  }
}

Now, not knowing much about the internal workings of images, can I use
a similar algorithm for PNG's and GIF's? I was hoping there was a
similar set of encoders/decoder classes for them. But, I haven't been
able to find any.