Making a green screen identifier

Recently I just had the idea of making a green screen identifier, I do have some Swift Xcode experience, but I don’t know where I should start or what to use for this idea. Any suggestions?

not really sure what you mean by this, do you mean you want to identify if a video/picture is using a greenscreen?

Almost, I’m aiming for the idea of the program identifying a green screen so the user can do a green screen substitution overlay.

oh that quite different basically thats image processing so its more algorithm and processing instead of making the ios app, the app will probably just serve as a “middle man” to get the image so it can be processed

So what would the algorithm be?

thats something you need to figure out, these kind of apps require a lot of research and 3rd party tools to implement which are pretty advanced stuff