How to work with assets correctly?

Question

Objective-C

Hello everyone
I just can’t understand how to work with assets
1) (it seems clear) Let’s say there is a button 50 by 50, it should have an icon 30 by 30, which means that my icons should be 30x30 60x60 90x90
2) And what to do for large images ? Let's say I have a picture for the whole screen (launch screen for example)
Well, I take this size for 4 and multiply by 3? Yes, this is a gigantic picture will
help answer)

Answer 1

https://www.paintcodeapp.com/news/iphone-6-screens...
For splash screen, take the values ​​from the Rendered Pixels line

Answer 2

If it's simple, take the size in points (and everything in development on is is measured in points, not pixels) and multiply by two for @2 and by three for @3. Andrew already wrote the screen sizes a little higher, for images that go to full screen