Digital watermarking gif images

Question

I ve writed a program which watermarks png and non-animated gif images .But there is a problem because we started to use animated gif images. How can we watermark animated gif images without corrupting animation of the image?
Regards
Murat

Answer 1

I haven't done much with gif animation, but here's an example that extracts the series of BufferedImages
from a gif file. Good luck!
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;
import java.net.URL;
import java.util.*;
import javax.imageio.*;
import javax.imageio.metadata.*;
import javax.imageio.stream.*;
import javax.swing.*;
import org.w3c.dom.*;
public class ViewGif extends JPanel {
    private BufferedImage[] images;
    private Point[] offsets;
    private BufferedImage composite;
    public static void main(String[] args) throws IOException {
        JPanel app = new ViewGif();
        app.setBackground(Color.RED);
        JFrame frame = new JFrame("ViewGif");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new JScrollPane(app));
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    public ViewGif() throws IOException {
        URL url = new URL("http://members.aol.com/royalef/sunglass.gif");
        Iterator readers = ImageIO.getImageReadersBySuffix("gif");
        if (!readers.hasNext())
            throw new IOException("no gif readers");
        ImageReader reader = (ImageReader) readers.next();
        if (readers.hasNext())
            System.out.println("(there were oither readers)");
        ImageInputStream iis = ImageIO.createImageInputStream(url.openStream());
        reader.setInput(iis);
        final int numImages = reader.getNumImages(true);
        images = new BufferedImage[numImages];
        offsets = new Point[numImages];
        for(int i=0; i<numImages; ++i) {
            images[i] =  reader.read(i);
            offsets[i] = getPixelOffsets(reader, i);
        composite = new BufferedImage(images[0].getWidth(), images[0].getHeight(),
            BufferedImage.TYPE_INT_ARGB);
        final Graphics2D g2 = composite.createGraphics();
        g2.drawImage(images[0], offsets[0].x, offsets[0].y, null);
        new javax.swing.Timer(100, new ActionListener(){
            int j = 1;
            public void actionPerformed(ActionEvent evt) {
                g2.drawImage(images[j], offsets[j].x, offsets[j].y, null);
                j = (j+1) % numImages;
                repaint();
        }).start();
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Insets insets = getInsets();
        g.drawImage(composite, insets.left, insets.top, null);
    public Dimension getPreferredSize() {
        Insets insets = getInsets();
        int w = insets.left + insets.right + composite.getWidth();
        int h = insets.top + insets.bottom + composite.getHeight();
        return new Dimension(w,h);
    static Point getPixelOffsets(ImageReader reader, int num) throws IOException {
        IIOMetadata meta = reader.getImageMetadata(num);
        Point point = new Point(-1,-1);
        Node root = meta.getAsTree("javax_imageio_1.0");
        for (Node c = root.getFirstChild(); c != null; c = c.getNextSibling()) {
            String name = c.getNodeName();
            if ("Dimension".equals(name)) {
                for (c = c.getFirstChild(); c != null; c = c.getNextSibling()) {
                    name = c.getNodeName();
                    if ("HorizontalPixelOffset".equals(name))
                        point.x = getValueAttribute(c);
                    else if ("VerticalPixelOffset".equals(name))
                        point.y = getValueAttribute(c);
                return point;
        return point;
    static int getValueAttribute(Node node) {
        try {
            return Integer.parseInt(node.getAttributes().getNamedItem("value").getNodeValue());
        } catch (NumberFormatException e) {
            return -2;