Main.hs

import Graphics.Gloss
import Codec.BMP
import System.Environment

-- | Displays uncompressed 24/32 bit BMP images.
main
 = do   args    <- getArgs
        case args of
         [fileName] -> run fileName
         _ -> putStr 
           $  unlines [ "usage: bitmap <file.bmp>"
                      , "  file.bmp should be a 24 or 32-bit uncompressed BMP file" ]

run fileName
 = do   picture@(Bitmap width height _ _)
                <- loadBMP fileName

        animate (InWindow fileName (width, height) (10,  10))
                black (frame width height picture)

frame :: Int -> Int -> Picture -> Float -> Picture
frame width height picture t
        = Color (greyN (abs $ sin (t * 2)))
        $ Pictures 
                [rectangleSolid (fromIntegral width) (fromIntegral height)
                , picture]