Haskell snippet to convert depth maps took from kinect to meshlab compatible point clouds

pgm2asc.hs

-- takes a PGM file and outputs an ASCII list of triplets (coordinates)
-- in order to import a kinect depth map in meshlab as a point cloud
import Data.Char(toLower)
main = interact pgm2triplets

pgm2triplets :: String -> String

pgm2triplets whole = unlines $ map showTriplet noHoles
                     where tokens=words whole
		           height=read$tokens!!2 :: Int
                           width=read$tokens!!1 :: Int
                           depth=read$tokens!!3 :: Int
			   points=drop 4 tokens
			   pointsInt = map (read) points :: [Int]
                           numOfPoints=width*height
		           pointsWithIndex = zip [0 .. numOfPoints] pointsInt
			-- Pay attention to the Axes system. Depth and Height are inverted
			   triplets=map (\(i,v)->(i `mod` width,height - i `div` height,depth - v)) pointsWithIndex
			   noHoles = filter (\(_,_,x)->x/=0) triplets
			   showTriplet (x,y,z) = show x ++ " " ++ show y ++" " ++show (z `div` 8) ++ "\n"