public void detectEdges()
    {
        GreenfootImage bg = getBackground();
        for (int x =0; x< bg.getWidth()-1; x++)
        {
            for (int y = 0; y< bg.getHeight(); y++)
            {
               Color c = bg.getColorAt(x,y);
               Color d = bg.getColorAt(x+1,y);
               if ( Math.sqrt(Math.pow(c.getRed() - d.getRed(),2))+(Math.sqrt(Math.pow(c.getBlue() - d.getBlue(),2)))+(Math.sqrt(Math.pow(c.getGreen()-d.getGreen(),2))));
               bg.setColorAt(x,y,c.WHITE);
            }
        }
    }