diff --git a/Graphics/Thumbnail.hs b/Graphics/Thumbnail.hs
--- a/Graphics/Thumbnail.hs
+++ b/Graphics/Thumbnail.hs
@@ -14,6 +14,12 @@
 
 data ImageFormat = Gif | Jpeg | Png
 
+-- | Convert `ImageFormat` to a mime type
+formatToType :: ImageFormat -> String
+formatToType Gif  = "image/gif"
+formatToType Jpeg = "image/jpeg"
+formatToType Png  = "image/png"
+
 data Thumbnail = Thumbnail { fmt :: ImageFormat     -- ^ Image Format Type
                            , img :: Image           -- ^ Thumbnail Image
                            , sz  :: Size            -- ^ Thumbnail Size
@@ -23,9 +29,11 @@
                            , saveFile :: FilePath -> IO ()
                            }
 
+-- | Create a thumbnails with the default size
 mkThumbnail :: L.ByteString -> IO (Either String Thumbnail)
 mkThumbnail = mkThumbnail' defaultBounds
 
+-- | Create a thumbnail from a specific subregion of the image
 mkThumbnail' :: ((Int,Int),(Int,Int)) -> L.ByteString -> IO (Either String Thumbnail)
 mkThumbnail' sizeBounds = thumbnail . L.unpack
   where
diff --git a/thumbnail.cabal b/thumbnail.cabal
--- a/thumbnail.cabal
+++ b/thumbnail.cabal
@@ -1,5 +1,5 @@
 Name:                thumbnail
-Version:             0.7
+Version:             0.7.1
 Synopsis:            generate thumbnail image
 Description:         generate thumbnail image
 Homepage:            https://github.com/cutsea110/thumbnail