repa-devil-0.1.2: Support for image reading and writing of Repa arrays

PortabilityRepa interface to the DevIL image loading library.
MaintainerDon Stewart <>




Read and write images in many formats, representing them in Haskell as a 3-dimensional repa array. Image parsing and decoding is done by the Developers Image Library, DevIL.

  • Many formats are supported, including .png, .bmp, .jpg, .tif
  • Image format parsing is determined by the filepath extension type.

Example: read a .png file into a 3D repa array, and write it out as a .jpg

 main = runIL $ do
          x <- readImage "/tmp/y.png" 
          writeImage "/tmp/x.jpg" x

Note that as DevIL is stateful, we ensure the library is initialized by running image manipulation functions in the IL monad, a wrapper over IO that ensures the library has been initialized. It is a type error to call image functions outside of the IL monad.


The IL monad

runIL :: IL a -> IO aSource

Running code in the IL monad. This is a simple wrapper over IO that guarantees the DevIL library has been initialized before you run functions on it.

data IL a Source

The IL monad. Provides statically-guaranteed access to an initialized IL context.


Image IO

readImage :: FilePath -> IL (Array DIM3 Word8)Source

Reads an image into an RGBA array. Indices are (row,column,color-channel).


 main = do
    x <- runIL $ readImage "/tmp/x.png"
    .. operations on x ..

Note: The image input type is determined by the filename extension.

writeImage :: FilePath -> Array DIM3 Word8 -> IL ()Source

Writes an RGBA array to a file. Indices are the row, column, and color-channel.

Note: The image output type is determined by the filename extension.