Android : Detect human body in Bitamp, crop it, change background of it and save it to gallery

I am trying to detect human body from Bitamp and then i want to crop it from that image and change the background and want to save the image as different image.

I want to do it in android. I heard about openCV but not able to implement it.

Can someone help me to do that task ? Stuck since long, running out of time now.