Nowhere. Face Invaders has no photo-library permission, so iOS never asks you for one — and the game has no way to read your album. It only ever receives the individual pictures you hand it, works on them on your device, and keeps the results inside its own storage.
This is the part worth understanding, because it is stronger than a promise not to upload anything.
An app that wants to read your photo library has to declare that intent, and iOS then shows you a permission prompt. Face Invaders makes no such declaration. If it tried to open your library it would be refused, because it never asked and cannot ask.
Instead, "Add from Photos" opens the system photo picker, which is a piece of iOS running in its own process, outside the game. You browse your album there; the game cannot see that screen. When you confirm your choice, iOS hands the game copies of those pictures and nothing else.
So the honest description is not "we don't upload your photos". It is that the game never had access to your photos in the first place.
Once you have handed over a picture, the game looks for faces in it using Vision, Apple's own image-analysis framework that is built into iOS. Specifically it runs a face-rectangle detection request against the image in memory.
All of that happens on the phone or iPad in your hand. Nothing is sent anywhere to be analysed, and there is no server involved in finding a face.
The detector returns rectangles. The game pads each one outwards into a square — deliberately generously, so hair and chin end up inside the circle rather than sliced off — and renders it as a face tile.
Each accepted face is written as a PNG in the app's Documents directory, inside the app's own container. The names you type and the order of the row are stored alongside it in the app's preferences.
Nothing here leaves the container. Remove a face in the Invader Studio and its file is deleted. Delete the app and all of it goes with it — there is no copy anywhere else to clean up.
The game makes network calls to exactly two places, and neither involves your pictures:
There are no third-party SDKs, no ad networks and no outside analytics tools. No image data is included in any of it.