The Simple DirectMedia Layer (SDL) is a cross-platform development library, written in C, that provides low-level audio, video, and input capabilities for multimedia applications. The SDL_image library extends SDL by providing capabilties for loading and working with a variety of image file formats.
Haskell already has bindings for SDL and SDL_image that work with version 1 of the library. However, the SDL library made a major change to the API with version 2, and SDL_image version 2 and greater changed their implementations to match. The existing Haskell bindings do not work with the updated versions of either of these libraries.
There is a new Haskell library, SDL2, which provides updated bindings for SDL v2 and later. However, it takes a very different approach from the Haskell SDL library it replaces, implementing instead a low-level set of bindings.
Hence, this library. This binding for SDL_image version 2 or greater builds upon SDL2 and currently provides a low-level approach quite similar to SDL2.
module Main (main) where
import Control.Monad
import Control.Monad.Error
import Foreign.C.String
import Foreign.Ptr
import Foreign.Storable
import Prelude hiding (init)
import Graphics.UI.SDL hiding (init, quit)
import Graphics.UI.SDL.Image
type AppM = ErrorT String IO
initApp :: AppM ()
initApp = do
initializedFlags <- liftIO $ init cFlags
when (initializedFlags /= cFlags) $ throwError "Error: SDL_image failed to load."
getArg :: AppM String
getArg = liftIO getArgs >>= extractArg
where
extractArg [] = throwError "Usage: ex1 <filename>"
extractArg (arg:_) = return arg
loadImage :: String -> AppM Surface
loadImage = loadImage' >=> peekImage
where
cFlags = initFlagsToC [InitPNG]
loadImage' fileName = liftIO $ withCString fileName load
peekImage imagePtr = do
when (imagePtr == nullPtr) $ throwError "Error: Image failed to load."
liftIO $ peek imagePtr
main :: IO ()
main = runErrorT (initApp >> getArg >>= loadImage) >>= printResult >> quit
where
printResult (Left err) = hPutStrLn stderr err
printResult (Right image) = putStrLn $ show imageSee the examples directory for other examples of the library in action.
This library is incompatible with the SDL and SDL-image Haskell packages. You must install
the Haskell package sdl2 instead.
To install the package from Hackage:
cabal install sdl2-imageTo build from source using GHC (installing in your home directory):
runhaskell Setup.hs --user configure
runhaskell Setup.hs build
runhaskell Setup.hs installThis library has been tested minimally using:
test directoryTo build and run tests using GHC:
runhaskell Setup.hs --user --enable-tests configure
runhaskell Setup.hs build
runhaskell Setup.hs test