mirror of
https://github.com/danth/stylix
synced 2024-11-22 20:23:15 +00:00
72 lines
2.7 KiB
Haskell
72 lines
2.7 KiB
Haskell
module Data.Colour ( LAB(..), RGB(..), deltaE, lab2rgb, rgb2lab ) where
|
|
|
|
-- | Lightness A-B
|
|
data LAB a = LAB { lightness :: a
|
|
, channelA :: a
|
|
, channelB :: a
|
|
}
|
|
|
|
-- | Red, Green, Blue
|
|
data RGB a = RGB { red :: a
|
|
, green :: a
|
|
, blue :: a
|
|
}
|
|
|
|
-- Based on https://github.com/antimatter15/rgb-lab/blob/master/color.js
|
|
|
|
deltaE :: (Floating a, Ord a) => LAB a -> LAB a -> a
|
|
deltaE (LAB l1 a1 b1) (LAB l2 a2 b2) =
|
|
let deltaL = l1 - l2
|
|
deltaA = a1 - a2
|
|
deltaB = b1 - b2
|
|
c1 = sqrt $ a1^2 + b1^2
|
|
c2 = sqrt $ a2^2 + b2^2
|
|
deltaC = c1 - c2
|
|
deltaH = deltaA^2 + deltaB^2 - deltaC^2
|
|
deltaH' = if deltaH < 0 then 0 else sqrt deltaH
|
|
sc = 1 + 0.045 * c1
|
|
sh = 1 + 0.015 * c1
|
|
deltaCkcsc = deltaC / sc
|
|
deltaHkhsh = deltaH' / sh
|
|
i = deltaL^2 + deltaCkcsc^2 + deltaHkhsh^2
|
|
in if i < 0 then 0 else sqrt i
|
|
|
|
-- | Convert a 'LAB' colour to a 'RGB' colour
|
|
lab2rgb :: (Floating a, Ord a) => LAB a -> RGB a
|
|
lab2rgb (LAB l a bx) =
|
|
let y = (l + 16) / 116
|
|
x = a / 500 + y
|
|
z = y - bx / 200
|
|
x' = 0.95047 * (if x^3 > 0.008856 then x^3 else (x - 16/116) / 7.787)
|
|
y' = if y^3 > 0.008856 then y^3 else (y - 16/116) / 7.787
|
|
z' = 1.08883 * (if z^3 > 0.008856 then z^3 else (z - 16/116) / 7.787)
|
|
r = x' * 3.2406 + y' * (-1.5372) + z' * (-0.4986)
|
|
g = x' * (-0.9689) + y' * 1.8758 + z' * 0.0415
|
|
b = x' * 0.0557 + y' * (-0.204) + z' * 1.0570
|
|
r' = if r > 0.0031308 then 1.055 * r**(1/2.4) - 0.055 else 12.92 * r
|
|
g' = if g > 0.0031308 then 1.055 * g**(1/2.4) - 0.055 else 12.92 * g
|
|
b' = if b > 0.0031308 then 1.055 * b**(1/2.4) - 0.055 else 12.92 * b
|
|
in RGB { red = max 0 (min 1 r') * 255
|
|
, green = max 0 (min 1 g') * 255
|
|
, blue = max 0 (min 1 b') * 255
|
|
}
|
|
|
|
-- | Convert a 'RGB' colour to a 'LAB' colour
|
|
rgb2lab :: (Floating a, Ord a) => RGB a -> LAB a
|
|
rgb2lab (RGB r g b) =
|
|
let r' = r / 255
|
|
g' = g / 255
|
|
b' = b / 255
|
|
r'' = if r' > 0.04045 then ((r' + 0.055) / 1.055)**2.4 else r' / 12.92
|
|
g'' = if g' > 0.04045 then ((g' + 0.055) / 1.055)**2.4 else g' / 12.92
|
|
b'' = if b' > 0.04045 then ((b' + 0.055) / 1.055)**2.4 else b' / 12.92
|
|
x = (r'' * 0.4124 + g'' * 0.3576 + b'' * 0.1805) / 0.95047
|
|
y = r'' * 0.2126 + g'' * 0.7152 + b'' * 0.0722
|
|
z = (r'' * 0.0193 + g'' * 0.1192 + b'' * 0.9505) / 1.08883
|
|
x' = if x > 0.008856 then x**(1/3) else (7.787 * x) + 16/116
|
|
y' = if y > 0.008856 then y**(1/3) else (7.787 * y) + 16/116
|
|
z' = if z > 0.008856 then z**(1/3) else (7.787 * z) + 16/116
|
|
in LAB { lightness = (116 * y') - 16
|
|
, channelA = 500 * (x' - y')
|
|
, channelB = 200 * (y' - z')
|
|
}
|