@hackage binary-file0.12.6

runghc -XQuasiQuotes exam.hs some.bmp out.bmp

exam.hs:

 import File.Binary
 import File.Binary.Data.LittleEndian
 import System.Environment
 import Data.ByteString as BS

 main = do
	[inf, outf] <- getArgs

   cnt <- BS.readFile inf
	let bmp = readBitmap $ cnt `BS.append` replicate 20 ' '
	print bmp

	let out = writeBitmap bmp {
		authorFirst = "Yoshikuni ",
		authorSecond = "Jujo      "
	 }
   BS.writeFile outf out

 instance RetType (Int, Int, Int) where
    type Argument (Int, Int, Int) = ()
    fromType _ (b, g, r) = cc $ [
        fromType 1 b, fromType 1 g, fromType 1 r, zero]
    toType _ str = let
        (b, rest) = toType 1 str
        (g, rest') = toType 1 rest
        (r, rest'') = toType 1 rest' in
        ((b, g, r), dp 1 rest'')

 [binary|

 Bitmap

 2: "BM"
 4: fileSize
 2: 0
 2: 0
 4: offset

 4: 40
 4: bitmapWidth
 4: bitmapHeight
 2: 1
 2: bitsPerPixel
 4: compressionMethod
 4: imageSize
 4: horizontalResolution
 4: verticalResolution
 4: numberOfColors
 4: importantColors
 ((), Just numberOfColors)<[(Int, Int, Int)]>: colors
 imageSize<BS.ByteString>: image

 10<String>: authorFirst
 10<String>: authorSecond

 |]