;; Flip effect - flips image horizontally or vertically
;; @param horizontal bool default true
;; @param vertical bool default false

(define-effect flip
  ((horizontal true) (vertical false))
  (let ((result frame))
    (if horizontal
        (set! result (flip-h result))
        nil)
    (if vertical
        (set! result (flip-v result))
        nil)
    result))