Yes! I toyed around with this about two years ago, and I was able to make NetBeans edit TIFF images (which it doesn't, by default). I also replaced some older-looking elements from the Images Editor module, most of that was accomplished by following Geertjan (https://blogs.oracle.com/geertjan/), who was also regularly in IRC, reachable via e-mail, his blog, etc.
Unfortunately, NetBeans was in the middle of an internal transition at the time (having to do with how actions are bound to keys and menu items), and I didn't get the newer way, and the module I expanded used the old keybinding method.
Unfortunately, NetBeans was in the middle of an internal transition at the time (having to do with how actions are bound to keys and menu items), and I didn't get the newer way, and the module I expanded used the old keybinding method.