anchor.diff:  
   (defun e ()
      (load 'fa.lisp)
  -   ;(edge "images/odetojoy.png" "output/odetojoy_edge.png")
  +   (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/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")
      )
  
positive.code:    (format t "Applying edge detect~%")
     (setf img (discrete-convolve img *edge-kernel*))
  
     (format t "Threashold the image~%")
     (threashold-image img 30)
  
     (format t "Edge thinning (long process)~%")
     (edge-thin img)
  
     (format t "overlaying image~%")
     (overlay img org)
     ;(format t "labelling ~%")
     ;(setf img (colourise-components img))
     ;(format t "K-means clustering~%")
     ;(format t "~S" (k-means-cluster-image-pixels org 3))
  
     (format t "Writing to file~%")
     (write-image org output)) ; output the image for now
  
negative.code: 
     (format t "Converting to greyscale~%")
     (greyscale-image img)
     (greyscale-image org)
  
     (format t "Bluring image~%")
     (setf img (blur-image img))
  