Bresenham

bres.clj

(defn draw-line!
  "Draws a line (bresenham algorithm)"
  [color [c0 r0] [c1 r1] screen]
  (let [dc (- c1 c0)
        dr (- r1 r0)
        derr (Math/abs (/ dr dc))]
    (loop [err derr
           r r0
           c c0]
      (when (< c c1)
        (set-pixel! color c r screen)
        (if (> err 0.5)
          (recur (dec (+ err derr)) (inc r) (inc c))
          (recur (+ err derr) r (inc c)))))))