Mandelbrot Image Generator using DevIL

Mandelbrot.hs

import Data.Complex
import Codec.Image.DevIL
import Data.Array.Unboxed
import System.Directory
import Control.Monad

main = ilInit
  >> doesFileExist path
  >>= flip when (removeFile path)
  >> writeImage path image

path = "fractal2.png"

image :: UArray (Int, Int, Int) Word8
image = render (400,320) (-2.2,-1.5) (1.2,1.5) mandel

mb = maxBound :: Word8

render (width,height) (lx,ly) (hx,hy) f = listArray ((0,0,0), (height, width, 3)) $
    do y <- [0..height]
       x <- [0..width]

       f (normalize width (lx,hx) x) (normalize height (ly,hy) y)

mandel :: Double -> Double -> [Word8]
mandel x y = if d > 20 then [0,0,0,mb] else [v, p `div` 3, v, mb] -- R,G,B,A
  where
    p        = ceiling $ fromIntegral mb * (phase $ is !! 10) / (2 * pi)
    v        = mb `div` fromIntegral d
    d        = 1 + length (take 20 $ takeWhile (<3) res)
    res      = map magnitude is
    is       = iterate (step com) com
    com      = x :+ y
    step c p = p**2 + c

normalize :: Int -> (Double, Double) -> Int -> Double
normalize s (l,h) i = l + (h - l) * i' / s' where [s', i'] = map fromIntegral [s,i]