How to choose the size/resolution for custom images for use in iOS applications?

Question

I understand how 1x, 2x and 3x image resolutions work but I'm unsure how I go about choosing the right size/resolution for custom images in general. Imagine that we have a simple layout like the following:

Now it is up to me to create the image (in Photoshop for example) for that UIImageView. What size and resolution should the highest quality version be? Do I just use the highest screen resolution of the iOS devices that are currently available as my guide?

Answer 1

There is not really a best size. As you said the highest screen resolution would be the maximum, because the device obviously can not display more pixels than it has provided. If the image view is only about 1/5 of the screen size then I would use a smaller image size for memory usage.

And you only need one size for background images for example. I normally place them in my assets folder into the 2x place and I am good.

For icons i use 25x25, 50x50 and 75x75 (which will display really small on the screen)

hope I could help you a little bit…