Resize2

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

@SuppressWarnings("unused")
public class Resize2 implements BaseFilter {

    @Override
    public BufferedImage process(BufferedImage source) {
        BufferedImage slika = new BufferedImage(source.getWidth(), source.getHeight(), BufferedImage.TYPE_INT_RGB);
        for (int x = 0; x < source.getWidth()/2; x++)
        {
            for (int y = 0; y < source.getHeight()/2; y++)
            {
                Color boja1 = new Color(source.getRGB(2*x, 2*y));
                Color boja2 = new Color(source.getRGB(2*x+1, 2*y));
                Color boja3 = new Color(source.getRGB(2*x, 2*y+1));
                Color boja4 = new Color(source.getRGB(2*x+1, 2*y+1));

                int red = average(boja1.getRed(), boja2.getRed(), boja3.getRed(), boja4.getRed());
                int green = average(boja1.getGreen(), boja2.getGreen(), boja3.getGreen(), boja4.getGreen());
                int blue = average(boja1.getBlue(), boja2.getBlue(), boja3.getBlue(), boja4.getBlue());
                int bojaNova = new Color(red, green, blue).getRGB();
                slika.setRGB(x, y, bojaNova);
            }
        }
        return slika;
    }

    private int average(int a1, int a2, int a3, int a4)
    {
        int avg = (a1 + a2 + a3 + a4)/4;
        return avg;
    }

}