;; Threshold effect - converts to black and white

(define-effect threshold
  :params (
    (level :type int :default 128 :range [0 255])
    (invert :type bool :default false)
  )
  (map-pixels frame
    (lambda (x y c)
      (let* ((lum (luminance c))
             (above (if invert (< lum level) (> lum level))))
        (if above
            (rgb 255 255 255)
            (rgb 0 0 0))))))