diff --git a/hakyll-images.cabal b/hakyll-images.cabal
--- a/hakyll-images.cabal
+++ b/hakyll-images.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: ae9f128028bfb7b003b7940adbbacf13e15a99ee309055e70cf616edbd4fb9b2
+-- hash: 937597bab3f482f7bbc2688e6a13a148528dc5fbd319eceea97fd955b04b54fa
 
 name:           hakyll-images
-version:        0.3.1
+version:        0.4.0
 synopsis:       Hakyll utilities to work with images
 description:    hakyll-images is an add-on to the hakyll package. It adds utilities to work with images, including JPEG compression.
 category:       Web
@@ -46,6 +46,7 @@
       JuicyPixels >=3
     , JuicyPixels-extra >0.3
     , base >=4.8 && <5
+    , binary >=0.5 && <0.10
     , bytestring >=0.9 && <0.11
     , hakyll >4
   default-language: Haskell2010
@@ -54,6 +55,7 @@
   type: exitcode-stdio-1.0
   main-is: TestSuite.hs
   other-modules:
+      Hakyll.Images.Common.Tests
       Hakyll.Images.CompressJpg.Tests
       Hakyll.Images.Resize.Tests
       Hakyll.Images
@@ -70,7 +72,10 @@
     , JuicyPixels >=3
     , JuicyPixels-extra >0.3
     , base >=4.8 && <5
+    , binary >=0.5 && <0.10
     , bytestring >=0.9 && <0.11
+    , directory >=1.0
+    , filepath >=1.0 && <1.5
     , hakyll >4
     , hakyll-images
     , tasty >=0.11 && <1.2
diff --git a/library/Hakyll/Images/Common.hs b/library/Hakyll/Images/Common.hs
--- a/library/Hakyll/Images/Common.hs
+++ b/library/Hakyll/Images/Common.hs
@@ -1,4 +1,7 @@
-
+{-# LANGUAGE TypeSynonymInstances #-}
+{-# LANGUAGE FlexibleInstances    #-}
+{-# LANGUAGE DeriveDataTypeable   #-}
+{-# LANGUAGE DeriveGeneric        #-}
 {-|
 Module      : Hakyll.Images.Common
 Description : Types and utilities for Hakyll.Images
@@ -23,11 +26,15 @@
 import Codec.Picture.Types              (DynamicImage)
 import Codec.Picture.Saving
 
+import Data.Binary                      (Binary(..))
 import Data.ByteString.Lazy             (toStrict)
 import Data.ByteString                  (ByteString)
+import Data.Typeable                    (Typeable)
+import GHC.Generics                     (Generic)
 
 import Hakyll.Core.Compiler             (Compiler, getResourceLBS, getUnderlyingExtension)
 import Hakyll.Core.Item                 (Item(..))
+import Hakyll.Core.Writable             (Writable(..))
 
 -- Supported (i.e. encodable) image formats
 data ImageFormat
@@ -35,15 +42,29 @@
     | Png
     | Bitmap
     | Tiff
-    deriving (Eq)
+    deriving (Eq, Generic)
 
--- Polymorphic type only to get an instance of functor
-data Image_ a = Image ImageFormat a
+instance Binary ImageFormat
 
+-- Polymorphic type only to get an instance of functor.
+-- Do not use this type.
+data Image_ a = Image ImageFormat a 
+    deriving (Typeable)
+
 instance Functor Image_ where
     fmap f (Image fmt a) = Image fmt (f a)
 
 type Image = Image_ ByteString
+
+-- When writing to disk, we ignore the image format.
+-- Trusting users to route correctly.
+instance Writable Image where
+    -- Write the bytestring content
+    write fp item  = write fp (image <$> item)
+
+instance Binary Image where
+    put (Image fmt content) = put fmt >> put content
+    get                     = Image <$> get <*> get
 
 -- | Extract format from an image
 format :: Image_ a -> ImageFormat
diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name: hakyll-images
-version: '0.3.1'
+version: '0.4.0'
 github: "LaurentRDC/hakyll-images"
 license: BSD3
 author: "Laurent P. René de Cotret"
@@ -26,6 +26,7 @@
 library:
   dependencies:
   - base              >= 4.8 && < 5
+  - binary            >= 0.5 && < 0.10
   - bytestring        >= 0.9 && < 0.11
   - hakyll            > 4
   - JuicyPixels       >= 3
@@ -47,8 +48,11 @@
     - tasty             >= 0.11 && < 1.2
     - tasty-hunit       >= 0.9  && < 0.11
     - HUnit-approx      >= 1.0.0.0
+    - filepath          >= 1.0  && < 1.5
+    - directory         >= 1.0
     # Base hakyll-images dependencies
     - base              >= 4.8 && < 5
+    - binary            >= 0.5 && < 0.10
     - bytestring        >= 0.9 && < 0.11
     - hakyll            > 4
     - JuicyPixels       >= 3
diff --git a/tests/Hakyll/Images/Common/Tests.hs b/tests/Hakyll/Images/Common/Tests.hs
new file mode 100644
--- /dev/null
+++ b/tests/Hakyll/Images/Common/Tests.hs
@@ -0,0 +1,62 @@
+{-# LANGUAGE OverloadedStrings #-}
+--------------------------------------------------------------------------------
+module Hakyll.Images.Common.Tests
+    ( tests
+    ) where
+
+
+--------------------------------------------------------------------------------
+import           Test.Tasty             (TestTree, testGroup)
+import           Test.Tasty.HUnit       (Assertion, testCase, assertBool)
+
+
+--------------------------------------------------------------------------------
+import           Hakyll
+import qualified Hakyll.Core.Logger as L
+import           Hakyll.Core.Runtime
+import           Hakyll.Images
+
+import           System.Directory       (doesFileExist)
+import           System.FilePath        ((</>))
+import           Text.Printf            (printf)
+
+fromAssertions :: String       -- ^ Name
+               -> [Assertion]  -- ^ Cases
+               -> [TestTree]   -- ^ Result tests
+fromAssertions name =
+    zipWith testCase [printf "[%2d] %s" n name | n <- [1 :: Int ..]]
+
+testConfiguration :: Configuration
+testConfiguration = defaultConfiguration
+    { destinationDirectory = "_testsite"
+    , storeDirectory       = "_teststore"
+    , tmpDirectory         = "_testtmp"
+    , providerDirectory    = "tests/data"
+    }
+
+cleanTestEnv :: IO ()
+cleanTestEnv = do
+    removeDirectory $ destinationDirectory testConfiguration
+    removeDirectory $ storeDirectory testConfiguration
+    removeDirectory $ tmpDirectory testConfiguration
+
+case1 :: Assertion
+case1 = do
+    logger <- L.new L.Error
+    _ <- run testConfiguration logger $ do
+        match "*.jpg" $ do
+            route idRoute
+            compile $ loadImage
+                >>= compressJpgCompiler 50
+    
+    _ <- assertBool "Image was not written" <$> 
+        (doesFileExist $ destinationDirectory testConfiguration </> "piccolo.jpg")
+
+    cleanTestEnv
+
+
+--------------------------------------------------------------------------------
+tests :: TestTree
+tests = testGroup "Hakyll.Images.Common.Tests" $ concat
+   [ fromAssertions "run" [ case1 ]
+   ]
diff --git a/tests/TestSuite.hs b/tests/TestSuite.hs
--- a/tests/TestSuite.hs
+++ b/tests/TestSuite.hs
@@ -9,14 +9,16 @@
 
 
 --------------------------------------------------------------------------------
-import qualified Hakyll.Images.CompressJpg.Tests
 
+import qualified Hakyll.Images.Common.Tests
+import qualified Hakyll.Images.CompressJpg.Tests
 import qualified Hakyll.Images.Resize.Tests
 
 
 --------------------------------------------------------------------------------
 main :: IO ()
 main = defaultMain $ testGroup "Hakyll"
-    [ Hakyll.Images.CompressJpg.Tests.tests
+    [ Hakyll.Images.Common.Tests.tests
+    , Hakyll.Images.CompressJpg.Tests.tests
     , Hakyll.Images.Resize.Tests.tests 
     ]