-- | A module defining some basic color tuples.  The old 16 color standard plus
--   a variable gray and some functions to attenuate, and fade colors.
module Graphics.Rendering.Hieroglyph.Colors where

import Graphics.Rendering.Hieroglyph.Primitives

white       = (1,1,1,1)
black       = (0,0,0,1)
red         = (1,0,0,1)
green       = (0,1,0,1)
blue        = (0,0,1,1)
yellow      = (1,1,0,1)
violet      = (1,0,1,1)
cyan        = (0,1,1,1)
darkRed     = attenuate 0.5 red
darkGreen   = attenuate 0.5 green
darkBlue    = attenuate 0.5 blue
darkYellow  = attenuate 0.5 yellow
darkViolet  = attenuate 0.5 violet
darkCyan    = attenuate 0.5 cyan

-- | Grey.  Domain of the input values is the bounded interval [0..100]
pctGrey :: Double -> (Double,Double,Double,Double) 
pctGrey k 
    | k >= 0 && k <= 100 = (k*0.01,k*0.01,k*0.01,k*0.01)
    | k < 0 = black
    | k > 0 = white

-- | Lighten the color by a floating point amount between [0..1]
unattenuate :: Double -> (Double,Double,Double,Double) -> (Double,Double,Double,Double)
unattenuate by ( r, g, b, a) = ((clamp 0 1 $ (1+by)*r), (clamp 0 1 $ (1+by)*g), (clamp 0 1 $ (1+by)*b), a)

-- | Darken the color by a floating point amount between [0..1]
attenuate :: Double -> (Double,Double,Double,Double) -> (Double,Double,Double,Double)
attenuate by (r, g, b, a) =  ((clamp 0 1 $ by*r), (clamp 0 1 $ by*g), (clamp 0 1 $ by*b), a)

-- | Make the color more transparent by multiplying the alpha component by a floating point amount between [0..1]
fade :: Double -> (Double,Double,Double,Double) -> (Double,Double,Double,Double)
fade by (r, g, b, a) =  (r, g, b, (clamp 0 1 $ by*a))

-- | Make the color less transparent by multiplying the alpha component by a floating point amount between [0..1]
unfade :: Double -> (Double,Double,Double,Double) -> (Double,Double,Double,Double)
unfade by (r, g, b, a) =  (r, g, b, (clamp 0 1 $ (1+by)*a))

-- | Mix two colors together with a ratio.
mix :: Double -> (Double,Double,Double,Double) -> (Double,Double,Double,Double) -> (Double,Double,Double,Double)
mix ratio ( r1, g1, b1, a1) ( r2, g2, b2, a2) = ( r', g', b', a') 
    where r' = clamp 0 1 $ (r1+r2) * ratio
          g' = clamp 0 1 $ (g1+g2) * ratio
          b' = clamp 0 1 $ (b1+b2) * ratio
          a' = clamp 0 1 $ (a1+a2) * ratio

clamp lo hi val = min hi (max lo val)