The Maven-generated jar file doubles as an OSGi bundle, but requires some additional system packages to load properly (com.sun.image.codec.jpeg, sun.misc, sun.nio, and sun.nio.ch).
For Felix (including Karaf) set config.properties to something like:
org.osgi.framework.system.packages.extra=com.sun.image.codec.jpeg,sun.misc,sun.nio,sun.nio.ch