I am trying to add a background image to iOS app. I am not sure about the dimensions of the image for the 1x, 2x, 3x. I want the background image working for all screen sizes.
Here is a nice graphic that displays all the screen sizes and background image sizes (courtesy of Reign Design):
you can use this link to get proper dimensions of an image for your app :)
just upload a high quality image and it returns 2 collections that can be used for different devices of IOS and Android apps