Writing multiple images to one file using ImageIO

Question

I am having trouble saving and reading multiple images from to/from one file. Here is the best i can come up with:
//this is utilizing an ObjectOutputStream because i need to also save some objects to the file
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("C:\\images.dat"));
oos.writeInt(ImageTable.size());
for(int k = 0; k  < ImageTable.size(); k++)
    ImageIO.write((BufferedImage)ImageTable.get(k), "png", oos);
    oos.flush();
//////////////////////////read function/////////////////////////
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("C:\\images.dat"));
int size = ois.readInt();
for(int k = 0; k < size; k++)
    ImageTable.add(ImageIO.read(ois));
}What it seems to do is read the first image and then place the marker at the end of the file so each consecutive calls to reading the file end up in either null, -1, or an EOF exception (bleh). Does anyone know how i can do this properly?
The code does run and saves something, although it is hard to tell exactly what it is saving since it is all in png format, it also loads the first image properly.

Answer 1

Is it possible to pack the different images in one big image?Conversely, some image formats let you store multiple images in a single image file.
Here's a demo. My results are that I don't have a gif writer, tiff can write sequences (this
is a well-known tiff property), I can trick (?) jpeg into stroring multiple images and I
can't get png to work: three images go in, one comes out.
import java.awt.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;
import java.util.*;
import javax.imageio.*;
import javax.swing.*;
import java.util.List;
public class MultiImageTest {
    public static void main(String[] args) throws IOException {
        URL url1 = new URL("http://today.java.net/jag/bio/JagHeadshot-small.jpg");
        URL url2 = new URL("http://today.java.net/jag/bio/JAG2001small.jpg");
        URL url3 = new URL("http://today.java.net/jag/Image24-small.jpeg");
        BufferedImage[] images = {ImageIO.read(url1), ImageIO.read(url2), ImageIO.read(url3)};
        display(images, "original", 0, 0);
        String[] suffixes = {"gif", "jpeg", "png", "tiff"};
        int x = 30, y = 20;
        for(int j=0; j<suffixes.length; ++j) {
            String suffix = suffixes[j];
            try {
                writeFile(images, suffix);
                display(readFile(suffix), suffix, x, y);
                x += 30;
                y += 20;
            } catch (Exception e) {
                System.err.println(suffix + ": " + e.getMessage());
    static void writeFile(BufferedImage[] images, String suffix) throws IOException {
        Iterator ws = ImageIO.getImageWritersBySuffix(suffix);
        if (!ws.hasNext())
            throw new IOException("no writer for: " + suffix);
        ImageWriter w = (ImageWriter) ws.next();
        File file = new File("temp." + suffix);
        file.delete();
        w.setOutput(ImageIO.createImageOutputStream(file));
        if (w.canWriteSequence()) {
            System.out.println("Using writeToSequence for format " + suffix);
            w.prepareWriteSequence(null);
            for(int j=0; j<images.length; ++j)
                w.writeToSequence(new IIOImage(images[j], null, null), null);
            w.endWriteSequence();
        } else {
            System.out.println("cross fingers for format " + suffix);
            for(int j=0; j<images.length; ++j)
                w.write(images[j]);
    static BufferedImage[] readFile(String suffix) throws IOException {
        Iterator rs = ImageIO.getImageReadersBySuffix(suffix);
        if (!rs.hasNext())
            throw new IOException("no reader for: " + suffix);
        ImageReader r = (ImageReader) rs.next();
        File file = new File("temp." + suffix);
        if (!file.exists())
            throw new IOException("no file: " + file.getName());
        r.setInput(ImageIO.createImageInputStream(file));
        List images = new ArrayList();
        for(int j=0; true; ++j) {
            try {
                images.add(r.read(j));
            } catch (IndexOutOfBoundsException e) {
                break;
        return (BufferedImage[]) images.toArray(new BufferedImage[images.size()]);
    static void display(BufferedImage[] images, String title, int x, int y) {
        JPanel cp = new JPanel(new GridLayout(1,0));
        for(int j=0; j<images.length; ++j)
            cp.add(new JLabel(new ImageIcon(images[j])));
        JFrame f = new JFrame(title);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(cp));
        f.pack();
        f.setLocation(x, y);
        f.setVisible(true);