[FMX] How do I make a radial mask?

1

Does anyone know how to mask in a circle?

To try to clarify:

If you had a clock face with the minute hand at 12, as the minute hand sweeps round it reveals a picture.

Here is an example of what I’m looking to do (the orange logo at the top)

http://www.burton.com/Gravis/

thanx
mark