Add image conversion functions

Add several image conversion functions to use for saving avatar images into specific formats.

Also add some tests of the new functions, along with some test images.

src/Graphics/Avatars/Pixelated.hs

@@ -45,6 +45,9 @@ module Graphics.Avatars.Pixelated
   -- ** Avatar
   Avatar(..), generateAvatar, scaleAvatar, saveAvatar, saveAvatarWith, convertAvatarToImage,
 
+  -- *** Image Conversion
+  ImageConversion, encodeToPng, encodeToGif, encodeToTiff,
+
   -- ** Color
   Color(..), getColorValue, colorFromSeed,
 
@@ -56,7 +59,7 @@ module Graphics.Avatars.Pixelated
 )
 where
 
-import Codec.Picture (encodePng, generateImage, Image(..), PixelRGB8(..))
+import Codec.Picture (encodeColorReducedGifImage, encodePng, encodeTiff, generateImage, Image(..), PixelRGB8(..))
 import Data.Char (ord)
 import qualified Data.ByteString.Lazy as B (ByteString, writeFile)
 import Data.ByteString.Lazy.Internal (packChars)
@@ -118,21 +121,20 @@ scaleAvatar factor avatar = avatar { grid = AvatarGrid scaledGrid }
 --   saveAvatar avatar path
 -- @
 saveAvatar :: Avatar -> FilePath -> IO ()
-saveAvatar = saveAvatarWith encodePng
+saveAvatar = saveAvatarWith encodeToPng
 
 -- | Saves the given avatar to the given file location, using the given
 -- function to encode it into a specific image format.
 --
--- Some examples of encoding functions are `Codec.Picture.Tiff.encodeTiff` and
--- `Codec.Picture.Png.encodePng`.
+-- Some examples of encoding functions are `encodeToGif` and `encodeToTiff`.
 --
 -- @
 -- saveTiffAvatar :: Seed -> FilePath -> IO ()
 -- saveTiffAvatar seed path = do
 --   let avatar = generateAvatar seed path
 --   saveAvatarWith encodeTiff avatar path
 -- @
-saveAvatarWith :: (Image PixelRGB8 -> B.ByteString) -> Avatar -> FilePath -> IO ()
+saveAvatarWith :: ImageConversion -> Avatar -> FilePath -> IO ()
 saveAvatarWith conversion avatar path = do
   let image = conversion $ convertAvatarToImage avatar
   B.writeFile path image
@@ -146,6 +148,26 @@ convertAvatarToImage avatar = image
         colorGrid = (map . map) (toPixel $ color avatar) $ unAvatarGrid $ grid avatar
         toPixel c v = if v then getColorValue c else PixelRGB8 255 255 255
 
+----------------------------------------
+-- Image Conversion
+
+-- | A function which converts an image into a lazy ByteString.
+type ImageConversion = (Image PixelRGB8 -> B.ByteString)
+
+-- | Converts an image into a Png image ByteString.
+encodeToPng :: ImageConversion
+encodeToPng = encodePng
+
+-- | Converts an image into a Gif image ByteString.
+encodeToGif :: ImageConversion
+encodeToGif img = case encodeColorReducedGifImage img of
+  Right i -> i
+  Left  _ -> error "Unable to create valid gif color palette for avatar image."
+
+-- | Converts an image into a Tiff image ByteString.
+encodeToTiff :: ImageConversion
+encodeToTiff = encodeTiff
+
 -------------------------------------------------------------------------------
 -- Colors
 

test/Graphics/Avatars/PixelatedSpec.hs

@@ -4,7 +4,9 @@ import Test.Hspec
 import Test.QuickCheck
 
 import Codec.Picture
-import qualified Data.ByteString.Lazy as B (ByteString(..))
+import Data.String (IsString(..))
+import qualified Data.ByteString.Lazy as B (ByteString(..), readFile)
+import System.IO (hGetContents)
 import System.IO.Unsafe (unsafePerformIO)
 
 import Graphics.Avatars.Pixelated
@@ -44,7 +46,22 @@ spec = do
 
   describe "convertAvatarToImage" $ do
     it "converts an avatar into an image" $ do
-      encodePng (convertAvatarToImage helloAvatar) `shouldBe` helloAvatarImage
+      encodePng (convertAvatarToImage helloAvatar) `shouldBe` helloAvatarImagePng
+
+  ----------------------------------------
+  -- Image Conversion
+
+  describe "encodeToPng" $ do
+    it "can encode an image into png format" $ do
+      (encodeToPng . convertAvatarToImage) helloAvatar `shouldBe` helloAvatarImagePng
+
+  describe "encodeToGif" $ do
+    it "can encode an image into gif format" $ do
+      (encodeToGif . convertAvatarToImage) helloAvatar `shouldBe` helloAvatarImageGif
+
+  describe "encodeToTiff" $ do
+    it "can encode an image into tiff format" $ do
+      (encodeToTiff . convertAvatarToImage) helloAvatar `shouldBe` helloAvatarImageTiff
 
   -----------------------------------------------------------------------------
   -- Colors
@@ -145,10 +162,14 @@ helloAvatarGridString = (init . unlines) [
   , "  █  █  "
   ]
 
-helloAvatarImage :: B.ByteString
-helloAvatarImage = image
-  where image = unRight $ encodeDynamicPng bytestring
-        bytestring = unRight $ unsafePerformIO $ readImage "test/Graphics/Avatars/helloAvatar.png"
+helloAvatarImagePng :: B.ByteString
+helloAvatarImagePng = unsafePerformIO $ B.readFile "test/Graphics/Avatars/helloAvatar.png"
+
+helloAvatarImageGif :: B.ByteString
+helloAvatarImageGif = unsafePerformIO $ B.readFile "test/Graphics/Avatars/helloAvatar.gif"
+
+helloAvatarImageTiff :: B.ByteString
+helloAvatarImageTiff = unsafePerformIO $ B.readFile "test/Graphics/Avatars/helloAvatar.tiff"
 
 testAvatar :: Avatar
 testAvatar = Avatar {