video overlay to an still image

Dear Community,

I am looking for info how to coregister a live video feed to a still image.

Problem: assume the same posture seen by a camera to a reference image.

Example: I have a .jpg of an ideal posture, e.g. person standing with a tennis racket and ready to serve. Call this reference image.

I would like this image as a background image on a live video camera.

A different person in front of the video camera has to mimic as close as possibly the position of the reference image.

Ideally the application should give immidiate numerical feedback in form of an percentage or a transformation matrix dispaying the differences.

Any help with fusing these two different modalities would be appreciated.

Perhaps there are other open source applications, which come with

this functionality already integrated. If so please provide information.

Thank you,

fm