probe exiv2 for the extensions it supports
Exiv2 supports reading from a handlful of file formats, although depending on how you compile it (aka with or without zlib support) some are not supposed (e.g. png). I'd like to be able to programically request a list of file formats exiv2 will currently supprot reading from or writing to. Aka I'd like two functions, one that returns a list of file formats we can read and another that returns a list of file formats we can write to.