Why do I get java.lang.StackOverflowError when using Flood Fill algorithm?

Question

My program is supposed to fill in a non-regular shape with a color (black and white for the beginning) that I specify in the boundaryFill4 method. Here is the link to myImage.png: https://dl.dropbox.com/u/41007907/myImage.png I use a very simple flood fill algorithm, but it does not work somehow... Here is the FULL code:

  import java.awt.Color;
  import java.awt.Container;
  import java.awt.Image;
  import java.awt.image.BufferedImage;
  import javax.swing.ImageIcon;
  import javax.swing.JFrame;
  import javax.swing.JLabel;

      public class MyPolygon extends JFrame {

private JLabel my;

public MyPolygon() throws InterruptedException {
    createMy();
}

private void createMy() throws InterruptedException {
    Container contentPane = getContentPane();
    contentPane.setBackground(Color.WHITE);
    contentPane.setLayout(null);
    contentPane.setSize(1000, 700);

    my = new JLabel();
    my.setIcon(new ImageIcon("myImage.png"));
    my.setBounds(50, 50, 300, 300);
    contentPane.add(my);

    setSize(1000, 700);
    setVisible(true);
    setLocationRelativeTo(null);

    int fill = 100;
    boundaryFill4(100, 100, fill, 50);
}

// Flood Fill method
public void boundaryFill4(int x, int y, int fill, int boundary) {
    int current;
    current = getPixel(x, y);
    if ((current >= boundary) && (current != fill)) {
        setPixel(x, y, fill);
        boundaryFill4(x + 1, y, fill, boundary);
        boundaryFill4(x - 1, y, fill, boundary);
        boundaryFill4(x, y + 1, fill, boundary);
        boundaryFill4(x, y - 1, fill, boundary);
    }
}

// Getting the color integer at specified point(x, y)
private int getPixel(int x, int y) {
    Image img = ((ImageIcon) my.getIcon()).getImage();
    BufferedImage buffered = new BufferedImage(img.getWidth(null),
            img.getHeight(null), BufferedImage.TYPE_INT_ARGB);
    buffered.getGraphics().drawImage(img, 0, 0, null);
    Color c = new Color(buffered.getRGB(x, y));
    int current = buffered.getRGB(x, y);
    return current;
}

// Setting the color integer to a specified point(x, y)
private void setPixel(int x, int y, int fill) {
    Image img = ((ImageIcon) my.getIcon()).getImage();
    BufferedImage buffered = new BufferedImage(img.getWidth(null),
            img.getHeight(null), BufferedImage.TYPE_INT_ARGB);
    buffered.getGraphics().drawImage(img, 0, 0, null);
    int red = fill;
    int green = fill;
    int blue = fill;
    Color c = new Color(buffered.getRGB(x, y));
    c = new Color(red, green, blue);
    buffered.setRGB(x, y, c.getRGB());
}

// Main method
public static void main(String args[]) throws InterruptedException {
    MyPolygon my = new MyPolygon();
    my.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

Why do I get StackOverflow error? How can I correct for it so that my code works?

Answer 1

StackOverflowException means, that your recursion is too deep for your memory or does not end. Try on a smaller Image. When this does not solves the problem there is something wrong with your recursion-end-condition. (Does setPixel() and getPixel really change the Image? Write a JUnitTest)

Also you really should simplify your setPixel and getPixel methods. They are too complex. For every Pixel you set or get you create a new BufferedImage-Instance and then dispose it after setting ONE pixel. You can store and reuse the BufferedImage.