Conversion to binary images using ImageMagick and juicypixels

main.hs

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+import Codec.Picture
+import System.Cmd (system)
+import System.Environment (getArgs)
+
+toBinaryImage :: Either String DynamicImage -> Image PixelYA8
+toBinaryImage = pixelMap (\x -> if x > 128 then PixelYA8 255 100 else PixelYA8 0 100) . extractPixel . extractImage where
+  extractImage x  = let (Right w)   = x in w
+  extractPixel x  = let (ImageY8 w) = x in w
+
+main = do
+  imageName <- getArgs
+  system $ "convert " ++ head imageName ++ " -resize 600x600 -gravity Center -extent 600x600 -colorspace Gray " ++ "gs_" ++ head imageName  -- ImageMagick
+  gsImage <- readImage $ "gs_" ++ head imageName
+  system $ "rm " ++ "gs_" ++ head imageName
+  writePng ("binary" ++ takeWhile (/= '.') (head imageName) ++ ".png") $ toBinaryImage gsImage