do I need to include @1x images of app only runs on iphone 4s and above?

Question

Is this still necessary? 2x and 3x seem to be the only images I need based on models I support. What is the correct approach?

Answer 1

If your app is targeted for iOS9 or less then you still have to build for the iPad 2 which does not have a retina display.

http://www.evad3rs.net/2014/10/ios-9-supported-devices-compatibility.html

Even if you're building an iPhone only app they will run on an iPad.

You cannot restrict your app by device. So if you're supporting iOS9 or less (which is every OS version) then you should include @1x images for this reason. If you don't then the @1x devices will just display scaled down versions of the @2x images so you don't NEED to include them... but you should.

What you can do instead (which is something that I have been doing more and more recently) is to use an app like PaintCode. This will take your images and turn them into code. This code is then imported into your project and the images are generated at runtime by the code. They are completely resolution independent and it reduces your app bundle size as you don't have to bundle in any images.

Answer 2

According to IOS Human Interface Guidelines all IOS high resolution devices below IPhone 6, use 2x form of images. So if your app will not run for non-high resolution devices, I am guessing you don't have to add 1x version of images.