How to write your own magic wand tool?

Question

iOS

Good day. The task was to create a "magic wand" tool, as in Photoshop for an application for ios devices. I will be grateful if you advise ready-made solutions, pods, C / C ++ code or an algorithm implemented in another language. Any information on the topic will also help: books that you can read to figure it out yourself, algorithms that can help in implementing the idea, etc.
I am attaching a video as an example of the result I want to get (2-3 minutes)
https://www.youtube.com/watch?v=GSlkeEhrqZ0

Answer 1

g.zeos.in/?q=magic%20wand%20source%20code