The personal care company L'oreal used to have an augmented reality app that let people create, save, and browse from different makeup looks that would overlay onto their face in real time, see here: https://youtu.be/G1z2Od5lIsA?t=20 (unfortunately the app appears to no longer be available on iPhone for real-life reference).
My question is what kind of (preferably open source) APIs or libraries are there that can be used to recreate something like this AR functionality? (Ie. identifying segments of the face (I assume), adding makeup overlays in AR, etc.).