Https://developer.apple.com/library/ios/documentation/UserExperience/Conceptual/MobileHIG/LaunchImages.html
Launch Images
A launch file or image provides a simple placeholder image, IOS displays when your apps starts up. The placeholder image gives users the impression that your app are fast and responsive because it appears instantly and is Quickly replaced by the first screen of the Your app. Every app must supply a launch file or at least one static image.
In IOS 8 and later, you can create a XIB or storyboard file instead of a static launch image. When you create a launch file in Interface Builder, you use the size classes to define different layouts for different display Environments and you use the Auto Layout to make minor adjustments. Using size classes and Auto Layout means that's can create a single launch file that looks good on all devices and DISPL AY environments. (For a overview of display environments and size classes, see Build in adaptivity; Terface Builder, see Size Classes Design Help.)
If you also need to support earlier versions of IOS, you can continue to supply static launch images in addition to a Laun CH file.
Important
You use a launch XIB or storyboard file to indicate the your app runs on iphone 6 Plus or iphone 6.
The following design guidelines apply to both launch files and static launch images.
Design a plain launch image that improves the user experience. In particular, the launch image isn ' t a opportunity to provide:
An "app entry experience," such as a splash screens
An About window
Branding elements, unless they is a static part of the Your app ' s first screen
Because users is likely to switch among apps frequently, you should make every effort to cut launch time to a minimum, an D You should design a launch image, downplays the experience rather than drawing attention to it.
Design A launch image that's identical to the first screens of the app, except for :
Text. The launch image is static and so any text on your display in it won ' t was localized.
UI elements This might change. If you include elements this might look different while the app finishes launching, users can experience an unpleasant flas H between the launch image and the first app screen.
If you think that following these guidelines would result in a plain, boring launch image, you ' re right. Remember, the launch image doesn ' t provide you with a opportunity for artistic expression. It ' s solely intended to enhance the user's perception of your app as quick to launch and immediately ready for use. For example, Settings and Weather each supply a launch the image that's little more than a background image.
The Settings launch image
The Weather launch image
If you need the use of static launch images, you create images in different sizes for different devices. Static launch images for all devices must include the status bar region. For specific measurements, see Table 39-1.
Although it's best-use-a launch file for iphone 6 and iphone 6 Plus, you can instead supply static launch images if NEC Essary. If you need to create a static launch images for these devices, use the following sizes:
For IPhone 6:
X 1334 (@2x) for portrait
1334 x (@2x) for landscape
For IPhone 6 Plus:
1242 x 2208 (@3x) for portrait
2208 x 1242 (@3x) for landscape
If you ' re using the static launch images, you can give each image a name the specifies how it should is used. The format of the launch image filename includes modifiers you use to specify the device, resolution, and orientation of t He image. To learn the name launch images appropriately, see app Launch (Default) images in App Programming Guide for IOS.