ImageJ is a very mature image processing library, developed by NIST. Though it doesn’t use Swing like all my other frameworks, all the filters and transformation tools are still a very useful addition to the image processing module that I’ve been working on. A colleague of mine here at uni has done extensive work with ImageJ in the past. Thought the conversion of the ImageJ releases is a bit time-consuming (also no source control system available), I finally got a range of releases published on Maven Central.