alt Hacker NewsThe table at the end is seriously misguided. You can’t compare the sizes of an iOS preinstalled app against a non-preinstalled app. It’s just a thin UI shell where the code for all the functionality is inside system frameworks. The Photos app is quoted at 4.2MB. Guess what, if you delete that, you still have system components to render photos, UI for a photo picker, perform analysis on photos such as face recognition, all the iCloud networking code to support iCloud Photo Library, etc.
You can though because a lot of those things you're talking about are available for any app. Sure Apple does have some private frameworks and what not that aren't available to everyone but I imagine if you wanted to recreate what the photo app is doing you'd be able to in 4.2mb or less.