module Data.Prizm.Color.CIE ( toRGB , toRGBMatrix , toLAB , toXYZ ) where import Control.Applicative import Data.Prizm.Types import Data.Prizm.Color.Transform import Data.Prizm.Color.Matrices.XYZ -- 2deg observer, d65 illuminant -- [x,y,z] refWhite :: [Double] refWhite = [95.047, 100.000, 108.883] -- | exact rational of the "0.008856" value. v1 :: Double v1 = (6/29) ** 3 -- | exact rational of the "7.787" value. v2 :: Double v2 = 1/3 * ((29/6) ** 2) -- | @transformRGB@ transform an XYZ integer to be computed against -- the xyzToRGB matrix. transformRGB :: Double -> Integer transformRGB v | v > 0.0031308 = min (round ((1.055 * (v ** (1 / 2.4)) - 0.055) * 255)) 255 | otherwise = min (round ((12.92 * v) * 255)) 255 transformLAB :: Double -> Double transformLAB v | v > v1 = v ** (1/3) | otherwise = (v2 * v) + (16 / 116) transformXYZ :: Double -> Double transformXYZ v | cv > v1 = cv | otherwise = (v - 16 / 116) / v2 where cv = v**3 -- | @toRGB@ convert a CIE color to an SRGB color. -- -- Once I've implemented CIE L*a*b -> XYZ and vice-versa functions -- then I'll introduce the type exhaustively here to handle any CIE -- color -> SRGB conversion. toRGB :: CIEXYZ Double -> RGB Integer toRGB = (toRGBMatrix d65SRGB) toRGBMatrix :: XYZtoRGB -> CIEXYZ Double -> RGB Integer toRGBMatrix m (CIEXYZ x y z) = let t = ZipList ((/100) <\$> [x,y,z]) [r,g,b] = (transformRGB) <\$> ((zipTransform t) <\$> m) in RGB r g b toLAB :: CIEXYZ Double -> CIELAB Double toLAB (CIEXYZ x y z) = let v = getZipList \$ ZipList ((/) <\$> [x,y,z]) <*> ZipList refWhite [tx,ty,tz] = (transformLAB) <\$> v l = (116 * ty) - 16 a = 500 * (tx - ty) b = 200 * (ty - tz) in CIELAB l a b toXYZ :: CIELAB Double -> CIEXYZ Double toXYZ (CIELAB l a b) = let y = (l + 16) / 116 x = a / 500 + y z = y - b / 200 [nx,ny,nz] = getZipList \$ ((*) <\$> ZipList ((transformXYZ) <\$> [x,y,z])) <*> ZipList refWhite in CIEXYZ nx ny nz