This is the beginnings of a pure Haskell loader for PNG images. It
stores the uncompressed image in a StorableArray (Int,Int) Word8, so
it should be convenient to use as a texture loader in OpenGL
applications since you can get a Ptr Word8 to the image data easily.

The performance is reasonable (the following run loads an 1.5megabyte
1024x768 24bit PNG image and writes out the raw bytes on a 2GHz
MacBook):

Mars2:PNG marko$ time ./Test scenery_1

real	0m0.315s
user	0m0.267s
sys	0m0.027s

Source for the test is in Test.hs.

Note that the library has not been tested with every possible kind of
PNG images, so use at your own risk.