gnull

import Data.Word

freq = 0.3
spread = 8.0

unbase :: Integral int => int -> Word8 -> Word8 -> Word8 -> int
unbase base r g b = (fi r*base+fi g)*base+fi b
    where fi = fromIntegral

-- | Approximate a 24-bit Rgb colour with a colour in the xterm256 6x6x6 colour cube, returning its index.