Cut out users face and head?

I have a picture of a face on a green screen. I can remove the green ok, but then I need to cut out their face and head off the neck. Can the OpenCV for Unity plugin do this? I have only seen examples of it doing recognition and showing a rect where the face is. I need the chin outline though. Would DLib be a good choice?

 

If you have an isolated subject on a green background, you could probably write a compute shader that gets that area and writes it to another texture?

Just a simple high level idea: pass in the source frame. Then find out the bounds of the object by analysing the image pixels. Then center your selection to that area and copy the contents to a target power of two texture (like 512x512), and you got your head extracted.

 

Sorry, maybe I didn't explain very good.

Using something like DLib I can get landmark points. Using those I think I can construct a mask - the dark area at bottom and isolate the head. I was wondering if OpenCV for Unity could possibly do this as well.
Thanks for the suggestion.