Memory and image coloring

Question

I want to keep a lot of images in the memory, so I use an array of images. The images are simple drawings and use few very few colors, thus take few space. I think they take 200 ko all together. However, once in a Image object, I suspect java to use billions of color because an Out of memory exception is declared. I can't believe 200 ko fill the memory up!! I know I can use a BufferedImage but I haven't found a way to load a BufferedImage from a file... help!

Answer 1

Here's a demo: by writing the image in PNG format, I can directly read it as a BufferedImage that
has an IndexColorModel.
import java.awt.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;
import javax.imageio.*;
import javax.swing.*;
public class IndexedExample {
    public static void main(String[] args) throws IOException {
        BufferedImage im1 = getOriginalImage();
        BufferedImage im2 = toIndexedType(im1);
        File file = new File("temp.png");
        saveImage(im2, file);
        BufferedImage im3 = loadImage(file);
        display(im1, im2, im3);
    static BufferedImage getOriginalImage() throws IOException {
        String url = "http://today.java.net/jag/bio/JagHeadshot-small.jpg";
        return ImageIO.read(new URL(url));
    static BufferedImage toIndexedType(BufferedImage im) {
        BufferedImage indexed = new BufferedImage(im.getWidth(), im.getHeight(),
            BufferedImage.TYPE_BYTE_INDEXED);
        Graphics2D g = indexed.createGraphics();
        g.drawRenderedImage(im, null);
        g.dispose();
        return indexed;
    static void display(BufferedImage im1, BufferedImage im2, BufferedImage im3) {
        JPanel cp = new JPanel(new GridLayout(1,0));
        addImage(cp, im1, "original");
        addImage(cp, im2, "indexed");
        addImage(cp, im3, "from file");
        JFrame f = new JFrame("IndexedExample");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(cp);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    static void addImage(JPanel cp, BufferedImage im, String title) {
        JLabel label = new JLabel(new ImageIcon(im));
        label.setBorder(BorderFactory.createTitledBorder(title));
        cp.add(label);
    static void saveImage(BufferedImage im, File file) throws IOException {
        String filename = file.getName();
        int dotIndex = filename.lastIndexOf('.');
        if (dotIndex == -1)
            throw new IOException("No file extension");
        ImageIO.write(im, filename.substring(dotIndex+1), file);
    static BufferedImage loadImage(File file) throws IOException {
        BufferedImage im = ImageIO.read(file);
        if (!(im.getColorModel() instanceof IndexColorModel))
            System.out.println("file image type is not ICM!");
        return im;
}