How Facebook and Instagram face filters are developed?

Question

I need n explanation regarding how they implement face filters , Interested in developing custom filters
Any guidance?
Thanks :)

Answer 1

A possibility is a neuronal network:
http://www.ai-junkie.com/ann/evolved/nnt1.html
There's also a link for an explanation of genetic algorithms.

Answer 2

I am going to try to create a face filter using css
Hahahaha