How can I draw shape on texture (image)?

I trying to make pie decal under character, representing his health. So I want to make dynamic texture. Can I use somehow drawPie(...) method from circle shape class on image? Or my only options is create my own drawing pie function using image.color(...)?

Meybe someone know other way to draw generated pie as decal?

Second question is, how can I create texture from image and mask (in code)?

This may help you:
http://www.esenthel.com/community/showth...p?tid=6340

Thank you Rubeus, but I saw that thread before. I know how draw pie on display, but what I need is draw it on image.

Anyway, I able to make pie by myself, using midpoint algorithm, but I'm affraid, that maybe isn't it the fastet way when I have to draw over a dozen decal with pie on scene.

On this screen you can see what I trying to do: