{- Copyright (c) 2008, 2009 Russell O'Connor Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. -} -- |Specifies 'Colour's in accordance with the sRGB standard. module Data.Colour.SRGB (Colour, RGB(..) ,sRGB24, sRGBBounded, sRGB ,toSRGB24, toSRGBBounded, toSRGB ,sRGB24shows, sRGB24show ,sRGB24reads, sRGB24read ,sRGBSpace ) where import Data.Word import Numeric import Data.Colour.Internal (quantize) import Data.Colour.SRGB.Linear import Data.Colour.RGBSpace hiding (transferFunction) {- a rewrite rule to think about adding. Should I have some instance restrictions (like Word8/Word16 Float/Double)? # RULES "sRGBBounded" forall r g b. toSRGBBounded (sRGBBounded r g b) = RGB r g b # -} {- Non-linear colour space -} {- the sRGB transfer function approximates a gamma of about 1/2.2 -} transferFunction lin | lin == 1 = 1 | lin <= 0.0031308 = 12.92*lin | otherwise = (1 + a)*lin**(1/2.4) - a where a = 0.055 invTransferFunction nonLin | nonLin == 1 = 1 | nonLin <= 0.04045 = nonLin/12.92 | otherwise = ((nonLin + a)/(1 + a))**2.4 where a = 0.055 -- |Construct a colour from an sRGB specification. -- Input components are expected to be in the range [0..1]. sRGB :: (Ord b, Floating b) => b -> b -> b -> Colour b sRGB = curryRGB (uncurryRGB rgb . fmap invTransferFunction) -- |Construct a colour from an sRGB specification. -- Input components are expected to be in the range [0..'maxBound']. sRGBBounded :: (Ord b, Floating b, Integral a, Bounded a) => a -> a -> a -> Colour b sRGBBounded r' g' b' = uncurryRGB sRGB (fmap f (RGB r' g' b')) where f x' = (fromIntegral x'/m) m = fromIntegral $ maxBound `asTypeOf` r' -- |Construct a colour from a 24-bit (three 8-bit words) sRGB -- specification. sRGB24 :: (Ord b, Floating b) => Word8 -> Word8 -> Word8 -> Colour b sRGB24 = sRGBBounded -- |Return the sRGB colour components in the range [0..1]. toSRGB :: (Ord b, Floating b) => Colour b -> RGB b toSRGB c = fmap transferFunction (toRGB c) {- Results are clamped and quantized -} -- |Return the approximate sRGB colour components in the range -- [0..'maxBound']. -- Out of range values are clamped. toSRGBBounded :: (RealFrac b, Floating b, Integral a, Bounded a) => Colour b -> RGB a toSRGBBounded c = fmap f (toSRGB c) where f x' = quantize (m*x') m = fromIntegral $ maxBound `asTypeOf` (f undefined) -- |Return the approximate 24-bit sRGB colour components as three 8-bit -- components. -- Out of range values are clamped. toSRGB24 :: (RealFrac b, Floating b) => Colour b -> RGB Word8 toSRGB24 = toSRGBBounded -- |Show a colour in hexadecimal form, e.g. \"#00aaff\" sRGB24shows :: (RealFrac b, Floating b) => Colour b -> ShowS sRGB24shows c = ("#"++) . showHex2 r' . showHex2 g' . showHex2 b' where RGB r' g' b' = toSRGB24 c showHex2 x | x <= 0xf = ("0"++) . showHex x | otherwise = showHex x -- |Show a colour in hexadecimal form, e.g. \"#00aaff\" sRGB24show :: (RealFrac b, Floating b) => Colour b -> String sRGB24show x = sRGB24shows x "" -- |Read a colour in hexadecimal form, e.g. \"#00aaff\" or \"00aaff\" sRGB24reads :: (Ord b, Floating b) => ReadS (Colour b) sRGB24reads "" = [] sRGB24reads x = [(sRGB24 a b c, c0) |(a,a0) <- readPair x', (b,b0) <- readPair a0, (c,c0) <- readPair b0] where x' | head x == '#' = tail x | otherwise = x readPair [] = [] readPair [_] = [] readPair a = [(x,a1)|(x,"") <- readHex a0] where (a0,a1) = splitAt 2 a -- |Read a colour in hexadecimal form, e.g. \"#00aaff\" or \"00aaff\" sRGB24read :: (Ord b, Floating b) => String -> (Colour b) sRGB24read x | length rx /= 1 || not (null (snd (head rx))) = error "Data.Colour.SRGB.sRGB24read: no parse" | otherwise = fst (head rx) where rx = sRGB24reads x -- |The sRGB colour space sRGBSpace :: (Ord a, Floating a) => RGBSpace a sRGBSpace = mkRGBSpace sRGBGamut transfer where transfer = TransferFunction transferFunction invTransferFunction (recip 2.2)