I think maybe you're not familiar with the jjPIXELMAP class or the jjANIMSET::allocate method, which together are all you need to create new animsets. The graphics you put in jjPIXELMAP instances before saving them to jjANIMFRAME instances could come from anywhere, including external files. PlusOJ, after all, does not use any .j2a files.

This is misleading... some of my classes resemble certain existing API classes in their function, but in the end the images you create end up inside jjAnimFrames, jjAnimations, and jjAnimSets.