By default it draws four round corners, but you may customize preferred patterns by putting a file under Pictures/org.gemini.round_corner/. File name and position mapping:
0.0.png - top left.
90.0.png - top right.
180.0.png - bottom right.
270.0.png - bottom left.
a.png - all four corners.
Other file extensions are also supported, say, jpg, jpeg, bmp.
You can fine some samples at https://github.com/Hzj-jie/android-round-corner/tree/master/samples. Copying you preferred ones, putting them in the expected folder, and renaming them, all done.
This application does not automatically execute itself on boot: I use https://play.google.com/store/apps/details?id=org.gemini.init to do it. You may find a sample at https://github.com/Hzj-jie/android-init/blob/master/sample/init.sh.
I do not think this simple functionality deserves a cent, so I wrote one myself. You may get the source code at https://github.com/hzj-jie/android-round-corner.