iOS : How to apply concave and convex effect on uiview?

I am working on an app where i have to open a camera and set surface view on it. That surface view will give concave or convex effect. Any help are most welcome.

Here i explained this two terminology:

A spherical mirror is said to be concave if the reflecting surface and the center of curvature (the center of the sphere of which the mirror forms part) are on the same side of the mirror; convex if the reflecting surface and the center of curvature are on opposite sides of the mirror.