Sharpen

import java.awt.Color;
import java.awt.image.BufferedImage;

public class Sharpen implements BaseFilter {
    @Override
    public BufferedImage process(BufferedImage source) {
        BufferedImage img = new BufferedImage(source.getWidth(), source.getHeight(), BufferedImage.TYPE_INT_RGB);

        for (int x = 0; x < img.getWidth(); x++)
            for (int y = 0; y < img.getHeight(); y++){
                img.setRGB(x, y, source.getRGB(x, y));
            }

        double[][] table = {
                {0.0, -0.67, 0.0},
                {-0.67, 3.67, -0.67},
                {0.0, -0.67, 0.0}
        };

        double sumRed = 0, sumGreen = 0, sumBlue = 0;

        for (int x = 1; x < source.getWidth() - 1; x++)
            for (int y = 1; y < source.getHeight() - 1; y++) {


                for (int nx = -1; nx <= 1; nx++)
                    for (int ny = -1; ny <= 1; ny++) {
                        double t = table[nx + 1][ny + 1];

                        Color c = new Color(source.getRGB(x + nx, y + ny));

                        sumRed   += t * c.getRed();
                        sumGreen += t * c.getGreen();
                        sumBlue  += t * c.getBlue();
                    }

                int red   = norm((int) sumRed);
                int green = norm((int) sumGreen);
                int blue  = norm((int) sumBlue);

                Color boja = new Color(red, green, blue);

                img.setRGB(x, y, boja.getRGB());
        }

        return img;
    }

    public int norm(int x) {
        if (x > 255)
            return 255;
        if (x < 0)
            return 0;
        return x;
    }
}