Haskell でサムネイル生成 ref: http://qiita.com/satosystems/items/abdb9696185f647b65a2

ThumbPlusSample.hs

import Control.Monad.IO.Class (liftIO)
import Control.Monad.Trans.Resource (runResourceT)
import qualified Data.ByteString.Lazy as LBI
import Data.Default (def)
import Data.Either (either)
import Graphics.ThumbnailPlus ( CreatedThumbnails(..)
                              , createThumbnails
                              , Configuration(..)
                              , Size(..)
                              , Thumbnail(..)
                              )
import System.Directory (renameFile)

file :: FilePath
file = "img/original.jpg"

conf :: Configuration
conf = def { maxFileSize = 1024 * 1024 * 100
           , thumbnailSizes = [ ( Size 200 200
                                , Nothing
                                )
                              ]
           }

main :: IO ()
main = do
  jpeg <- LBI.readFile file
  runResourceT $ do
    CreatedThumbnails (_:[t]) _ <- createThumbnails conf file
    liftIO $ renameFile (thumbFp t) "img/thumb2.jpg"
  return ()

ThumbSample.hs

import qualified Data.ByteString.Lazy as LBI
import Graphics.Thumbnail (mkThumbnail', Thumbnail(..))

file :: FilePath
file = "img/original.jpg"

main :: IO ()
main = do
  jpeg <- LBI.readFile file
  Right thumb <- mkThumbnail' ((50, 50), (200, 200)) jpeg
  saveFile thumb "img/thumb1.jpg"