;;; Procedure:
;;;   image-render-spot!
;;; Parameters:
;;;   image, an image
;;;   spot, a spot
;;; Purpose:
;;    Draw the spot on the image.
;;; Produces:
;;;   [Nothing; Called for the side effect]
(define image-render-spot!
  (lambda (image spot)
    (context-set-fgcolor! (spot-color spot))
    (image-select-rectangle! image selection-replace
                             (spot-col spot) (spot-row spot) 1 1)
    (image-fill! image)
    (image-select-nothing! image)))