Data commit

Task/Grayscale-image/Haskell/grayscale-image.hs

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+module Bitmap.Gray(module Bitmap.Gray) where
+
+import Bitmap
+import Control.Monad.ST
+
+newtype Gray = Gray Int deriving (Eq, Ord)
+
+instance Color Gray where
+    luminance (Gray x) = x
+    black = Gray 0
+    white = Gray 255
+    toNetpbm = map $ toEnum . luminance
+    fromNetpbm = map $ Gray . fromEnum
+    netpbmMagicNumber _ = "P5"
+    netpbmMaxval _ = "255"
+
+toGrayImage :: Color c => Image s c -> ST s (Image s Gray)
+toGrayImage = mapImage $ Gray . luminance