anchor.diff:                          (multiple-value-bind (r1 g1 b1)
                              (pixel origional i j)
                              (declare (type (unsigned-byte 8) r1 g1 b1))
  +                           (setf grey (floor (/ (+ r1 g1 b1) 3)))
                              (if (= r 255)
                                 (setf (pixel origional i j)
  -                                 (values 255 255 255))
  +                                 (values grey grey grey))
                                 (setf (pixel origional i j)
                                    (values r1 g1 b1))))))))))))
   
  
positive.code: 
  (defun e ()
     (load 'fa.lisp)
     ;(edge "images/odetojoy.png" "output/odetojoy_edge.png")
     (edge "images/the_scream.png" "output/scream_edge.png")
     ;(edge "images/odetojoy.png" "output/odetojoy_edge.png")
     ;(edge "images/im_blauen.png" "output/im_blauen_edge.png")
     ;(edge "images/pacman_game.png" "output/pacman_game_edge.png")
     ;(edge "images/stardust.png" "output/stardust_edge.png")
     ;(edge "images/starry_night.png" "output/starry_night_edge.png")
     )
  
negative.code: 
     (format t "Converting to greyscale~%")
     (greyscale-image img)
     (greyscale-image org)
  
     (format t "Bluring image~%")
     (setf img (blur-image img))
  