I'm looking for an image metadata manipulation library, and so far I've 
only found a couple that look usable. ruby-exiv2 uses the C++ exiv2 
library, but is incomplete (no xmp support, doesn't seem to handle 
multiple iptc keywords. mini-exiftool uses the excellent exiftool library, 
but that's written in Perl, and I'd rather use something that's either 
pure-ruby, or a C/C++ library for efficiency.

Does anyone know of any mature image metadata manipulation libraries that 
I've missed?

Paul