anchor.diff:  "
     (let* ((mask (if mask mask (apply #'generate-mask pattern))))
       (binary-morphological-filter
  -     (binary-morphological-filter image :or mask fill) :and mask fill)))
  +     (binary-morphological-filter image :and mask fill) :or mask fill)))
   
   
   (defun close-filter (image &key pattern mask (fill '(0)))
  
positive.code:   2*size+1 gives the total width and height of the mask.
  "
    (let ((mask (if mask mask (apply #'generate-mask pattern))))
      (binary-morphological-filter image :or mask fill)))
  
  
  (defun dilation-filter (image &key pattern mask (fill '(0)))
    "Returns a binary GRAYSCALE-IMAGE produced by a morphological filter
    with an AND operation on the given mask kernel.
  
    The mask may be either specified by PATTERN or provided by MASK, a
    2-d array of (unsigned-byte 8) values set to 0 or 1.
  
negative.code:   2*size+1 gives the total width and height of the mask.
  "
    (let ((mask (if mask mask (apply #'generate-mask pattern))))
      (binary-morphological-filter image :or mask fill)))
  
  
  (defun majority-filter (image &key pattern mask (fill '(0)))
  