Thanks for the note, the best way to start is to look through some tutorials on OpenCV.
Here are some links:
Object Detection using Haar feature-based cascade classifiers is an effective object detection method proposed by Paul…docs.opencv.org
objc.io publishes books on advanced techniques and practices for iOS and OS X developmentwww.objc.io
In this tutorial we will learn how to swap out a face in one image with a completely different face using OpenCV and…www.learnopencv.com
Here is the rough steps I went through at a high level :
a) Build something with face swap
b) Switch the face swap to switch with a static image.
c) Switch the static image for a mask.
You can find the code for this project via: https://github.com/requestlabs/maskito-ios