anchor.diff:       (lambda (x1 x2 y alpha)
          (declare (type fixnum x1 x2 y)
   		(type fixnum alpha))
  -       ;;(declare (optimize (speed 3)))
          (setf alpha (min (abs alpha) 255))
          (when (plusp alpha)
   	 (loop for x from x1 below x2 do
  
positive.code:      (lambda (x y alpha)
         (declare (type fixnum x y)
  		(type fixnum alpha))
         ;;(declare (optimize (speed 3)))
         (when (or (null clip-region) (clim:region-contains-position-p clip-region x y))
  	 (setf alpha (min (abs alpha) 255))
  	 (when (plusp alpha)
  
negative.code:   `(let ((data ,data))
       (declare (type rgba-image-data data))
       (lambda (x1 x2 y alpha)
         (setf alpha (min (abs alpha) 255))
         (when (plusp alpha)
  	 (loop for x from x1 below x2 do
  