# Difference between revisions of "Library for colours"

Simple thing for working on colours in the RGB colours space. (The intention being that each component is in the interval 0 <= x <= 1.) You could just use tuples, but this library provides simple colour arithmetic.

```module Colour where

data Colour = Colour {red, green, blue :: Double} deriving (Eq, Show)

cmap :: (Double -> Double) -> Colour -> Colour
cmap f (Colour r g b) = Colour (f r) (f g) (f b)

czip :: (Double -> Double -> Double) -> Colour -> Colour -> Colour
czip f (Colour r1 g1 b1) (Colour r2 g2 b2) = Colour (f r1 r2) (f g1 g2) (f b1 b2)

cfold :: (Double -> Double -> Double) -> Colour -> Double
cfold f (Colour r g b) = r `f` g `f` b

cpromote :: Double -> Colour
cpromote x = Colour x x x

instance Num Colour where
(+) = czip (+)
(-) = czip (-)
(*) = czip (*)
negate = cmap negate
abs    = cmap abs
signum = cmap signum
fromInteger x = cpromote (fromInteger x)

instance Fractional Colour where
(/) = czip (/)
recip = cmap recip
fromRational x = cpromote (fromRational x)

clip :: (Num n, Ord n) => n -> n
clip n
| n < 0 = 0
| n > 1 = 1
| otherwise = n

cclip :: Colour -> Colour
cclip = cmap clip

quantinize :: Int -> Double -> Int
quantinize max v = floor (v * (fromIntegral max))
```