iOS: Preparing background images for applications

Question

Mostly every iOS application has a view with an image as background. Is there any image sizing guide out there? For example here is an iOS screen designed in Sketch:

Answer 1

I use background images in my Apps. To solve this problem I use one image that has the resolution to cover all iPhones and all the iPads except the large one. The image size is 2048x2048 points or 1024x1024 pixels at @2x to cover the 9.7 inch iPad.

The image is compressed JPG to keep the size down. Note that I allow it to scale for iPhone 6 Pluse (@3x) and 12.7 inch iPad Pro (@2x) as the quality doesn't seem to be affected. I can justify the scaling for the larger devices, because if I provided image for the 12.7 inch iPad Pro, it will be 5464x4096 points (@2x) and 2732x2048 pixels and then the JPG compression would have to be so high (if I wanted to keep the size down), that the quality of the image was low anyway compared with scaling.

If you need high quality try both JPG and PNG for comparison, because the PNG becomes very large for complex images, but gives the best quality.