Draw image on a canvas with the given EXIF orientation

image.cljs

(defn draw-image [canvas img orientation]
  (let [ctx (.getContext canvas "2d")
        [width height] (.-width img) (.-height img)]
    (case orientation
      (1 nil) ; left top
      (do
        (set! (.-width canvas) width)
        (set! (.-height canvas) height)
        (.drawImage ctx img 0 0 width height))

      2 (do ; top right
          (set! (.-width canvas) width)
          (set! (.-height canvas) height)
          (.scale ctx -1 1)
          (.drawImage ctx img (* -1 width) 0 width height))

      3 (do ; right top
          (set! (.-width canvas) width)
          (set! (.-height canvas) height)
          (.rotate ctx (.-PI js/Math))
          (.drawImage ctx img (* -1 width) (* -1 height) width height))

      4 (do ; left top
          (set! (.-width canvas) width)
          (set! (.-height canvas) height)
          (.scale ctx 1 -1)
          (.drawImage ctx img 0 (* -1 height) width height))

      5 (do ; top left
          (set! (.-width canvas) height)
          (set! (.-height canvas) width)
          (.rotate ctx (/ (.-PI js/Math) -2))
          (.scale ctx -1 1)
          (.drawImage ctx img 0 0 width height))

      6 (do ; top right
          (set! (.-width canvas) height)
          (set! (.-height canvas) width)
          (.rotate ctx (/ (.-PI js/Math) 2))
          (.drawImage ctx img 0 (* -1 height) width height))

      7 (do ; bottom right
          (set! (.-width canvas) height)
          (set! (.-height canvas) width)
          (.rotate ctx (/ (.-PI js/Math) -2))
          (.scale ctx 1 -1)
          (.drawImage ctx img 0 (* -1 height) (* -1 width) height))

      8 (do ; bottom left
          (set! (.-width canvas) height)
          (set! (.-height canvas) width)
          (.rotate ctx (/ (.-PI js/Math) -2))
          (.drawImage ctx img 0 0 (* -1 width) height)))))