Shaman,
I have been looking a long time for a image processing library comparable to opencv in Java. For the amount of automated tasks opencv performs there is nothing that comes close to it for the advanced machine vision type applications.
In terms of image processing though imagej has a large amount of preimplemented algorithms and plugins. I use this library all the time to preprocess things I need to send into opencvs machine vision utilities. This is also open source with easy ways of adding additional features through plugins or direct manipulations so I think it could meet most of your requirements.
