Data.Array.Repa.IO.DevIL

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 $
          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 a

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

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

Instances

Monad IL

MonadIO IL

Image IO

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

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

Example:

 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 ()

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.