Some explanations for iOS xcasset catalogs required

Question

I am completely new to iOS development. I want to make a small game with the Sprite-Kit framework and I am already stuck at the xcasset catalog.

Say I have a 320x320 pixel image for my iPhone 4s that features a resolution of 960x480 pixels. I put this to "iPhone 2x" in the xcasset catalog, right (cp. following image) ?

Now, do I need for the "iPhone 1x" a 160x160 and for the "iPhone 3x" a 640x640 version of the image? What about the iPad ? What does "iPad 1x" and "iPad 2x" exactly mean in terms of pixels? Is "iPad 1x" also 320x320 and "iPad 2x" 640x640 in my example ?

EDIT-1: Thanks for the link to the possible duplicate. But there's also not discussed what exactly the iPad version are for and how they are related in terms of pixels.

EDIT-2: The resizing results with Asset Catalog Creator are not satisfying, although I used a 4096x4096 pixel image to produce the launch images (cp. following image):

Answer 1

It looks like your Sky image isn't set for "universal devices" which is why it's asking about iPad images. See Apple's Asset Catalog Help for more info about why you'd want device-specific images.

Select the Sky image name, then hit Command-Opt-4 to open the Attribute Inspector. Where it says "Devices" set it to "Universal" and you should just see the "Universal" section with the 1x, 2x, & 3x image wells.

Also, your sample image sizes seem off. If your @2x image (for iPhone 4s) is 960x480 then the 1x image would be 480 x 240. (and your 3x image for use on the iPhone 6+ would be 1440 x 960.) Your 1x image should be whatever point size you want, the 2x should be twice that in both dimensions, and the 3x should be three times the 1x in both dimensions.