Generates a Mandelbrot fractal as a PNM image.

mandel.clj

; Example http://www.flickr.com/photos/sneeu/5894879494/
(ns mandel
  (:require [clojure.string :as string]))

(defn mandel
  "Generates a Mandelbrot image as a seq of seqs."
  [size max-iteration scale depth]
  (let [width (first size)
        height (second size)
        mandel-limit (fn mandel-limit [x0 y0 x y i]
                  (if (= i max-iteration)
                    0
                    (if (> (- (* x x) (* y y)) 4)
                      (int (/ (* i depth) max-iteration))
                      (mandel-limit x0 y0 (+ x0 (- (* x x) (* y y))) (+ y0 (* 2 x y)) (+ i 1)))))
        mandel-point  #(let [x0 (* (+ (/ width -2) %1) scale)
                             y0 (* (+ (/ height -2) %2) scale)]
                          (mandel-limit x0 y0 x0 y0 0))
        mandel-row (fn [x ys] (map #(mandel-point x %1) ys))]
      (map #(mandel-row %1 (range 0 height)) (range 0 width))))

(defn mandel-pnm
  [size max-iteration scale depth]
  (println (format "P2\n%d %d\n%d" (first size) (second size) depth))
  (println (string/join "\n" (map #(string/join " " %1) (mandel size max-iteration scale depth)))))

(mandel-pnm '(800 800) 200 0.005 255)