Simple example of pixelating an image

PixelateImage.java

protected BufferedImage pixelate(BufferedImage source) {
    // How big should the pixelations be?
    final int PIX_SIZE = 16;

    BufferedImage img = new BufferedImage(source.getWidth(), source.getHeight(), BufferedImage.TYPE_INT_ARGB);
    Graphics2D g2d = img.createGraphics();
    g2d.drawImage(source, 0, 0, this);
    g2d.dispose();

    // Get the raster data (array of pixels)
    Raster src = img.getData();

    // Create an identically-sized output raster
    WritableRaster dest = src.createCompatibleWritableRaster();

    // Loop through every PIX_SIZE pixels, in both x and y directions
    for (int y = 0; y < src.getHeight(); y += PIX_SIZE) {
        for (int x = 0; x < src.getWidth(); x += PIX_SIZE) {

            // Copy the pixel
            double[] pixel = new double[4];
            pixel = src.getPixel(x, y, pixel);

            // "Paste" the pixel onto the surrounding PIX_SIZE by PIX_SIZE neighbors
            // Also make sure that our loop never goes outside the bounds of the image
            for (int yd = y; (yd < y + PIX_SIZE) && (yd < dest.getHeight()); yd++) {
                for (int xd = x; (xd < x + PIX_SIZE) && (xd < dest.getWidth()); xd++) {
                    dest.setPixel(xd, yd, pixel);
                }
            }
        }
    }

    // Save the raster back to the Image
    img.setData(dest);
    return img;
}

This is taken from https://stackoverflow.com/questions/15777821/how-can-i-pixelate-a-jpg-with-java