Image Erosion using a kernel

Question

Hello all.
I am trying to change a black and white image. I want to perform erosion to increase gaps, etc. Does anyone know how I can erode a bufferedimage and get the result as a bufferedimage. I understand that I will have to use a kernel but I don't know how to implement this.
Please help if you can.

Answer 1

Ok so I am still playing around with this :-)
A very useful program to have when performing this kind of image manipulation is ZoomIn, which you can download for free from:
http://users.csc.calpoly.edu/~bfriesen/software/zoomin.shtml
Find below a simple manual implementation of a cross-like erosion kernel. Also notice the high number of operations involved (and I really don't know the cost of all these getRGB/setRGB calls). Working on a binary image (boolean array) instead of these BufferedImages should speed up things quite a lot.
import java.awt.BorderLayout;
import java.awt.image.BufferedImage;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Erosion {
    public static void main(String[] args) throws Exception {
        BufferedImage src = ImageIO.read(new URL(
                "http://homepages.inf.ed.ac.uk/rbf/HIPR2/thumbs/mon1thr1.GIF"));
        int w = src.getWidth();
        int h = src.getHeight();
        BufferedImage dest = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
        final int BLACK = 0xFF000000;
        final int WHITE = 0xFFFFFFFF;
        for (int x = 1; x < w - 1; x++) {
            for (int y = 1; y < h - 1; y++) {
                // System.out.println(Integer.toHexString(src.getRGB(x, y)));
                // a cross-like kernel (left, right, top, bottom)
                if (src.getRGB(x - 1, y) != WHITE //
                        || src.getRGB(x + 1, y) != WHITE //
                        || src.getRGB(x, y - 1) != WHITE //
                        || src.getRGB(x, y + 1) != WHITE//
                    // if one neighbor pixel is black, make this one black too
                    dest.setRGB(x, y, BLACK);
                } else {
                    dest.setRGB(x, y, WHITE);
        JFrame f = new JFrame("Erosion");
        f.getContentPane().add(new JLabel(new ImageIcon(src)), BorderLayout.CENTER);
        f.getContentPane().add(new JLabel(new ImageIcon(dest)), BorderLayout.EAST);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
}