Android: Face recognition ( NOT detection ) for pictures

Android: Face recognition ( NOT detection ) for pictures

I'm developing an android application and I need to use face recognition.
I just want to ask what's the easiest way to compare 2 faces I have in two
bitmaps ( for example ) and find out they're one person or not... It's not
for face unlock or security systems, so it's confident isn't very
important. It's OK to be good enough :) and please help me to find easiest
samples if it's possible; because samples of OpenCV ( for example ) were
too confusing for me. :)
I know I can use OpenCV or ..., but it'll be much better to let me know,
if there's any way to do it with Android's APIs or something that run on
device, WITHOUT any additional applications' installation.
< THANK YOU VERY VERY MUCH. >