Launch screen storyboard constraints in iOS Universal app

Question

I'm working on a LaunchScreen.storyboard file for an iOS Universal app in Xcode 7.3.

I must use only constraints defined in storyboard, because the launch screen will be shown before the app will be loaded (can't configure constraints programmatically in a UIViewController subclass).

The background image in the main UIViewController has

• aspect-ratio (3456:2592),
• center vertically and
• center horizontally constraints.

I'm trying to obtain the following conditions:

• maintain the background image aspect-ratio,
• activate backgroundImageView.Top = containerView.Top when screen width <= screen height
• activate backgroundImageView.Leading = containerView.Leading - 20 when screen width > screen height

The problem is that storyboard constraint definition by size classes is not powerful enough to express conditions like screen width >/<= screen height (e.g.: an iPad Air Fullscreen has always regular width and height, but screen width < screen height in portrait mode and screen width > screen height in landscape mode).

I tried also to define the background image asset set by device, but it allows only to specify iPhone/iPad x1, x2 and x3 versions of the image.

Answer 1

You don't need auto-layout for this. Make the UIImageView fill the whole screen, then select the Aspect Fill mode for the background UIImageView.

Result:

Note that the background image (1) keeps the aspect ratio, (2) centered horizontally and vertically, and (3) automatically scale up to fit the longest axis.