When loading an application on an iPhone or iPad, a launch image can be shown to provide feedback to the user that the application is loading. On the iPhone one Default.png file was adequate, with the iPad one needs to anticipate the device being started in any orientation, including upside down.
iPad Launch Image Orientations
To deal with various orientation options, a new naming convention has been created for iPad launch images. The screen size of the iPad is 768×1024, notice in the dimensions that follow the height takes into account a 20 pixel status bar.
|Default-Portrait.png *||768w x 1004h|
|Default-PortraitUpsideDown.png||768w x 1004h|
|Default-Landscape.png **||1024w x 748h|
|Default-LandscapeLeft.png||1024w x 748h|
|Default-LandscapeRight.png||1024w x 748h|
* If you have not specified a Default-PortraitUpsideDown.png file, this file will take precedence.
** If you have not specified a Default-LandscapeLeft.png or Default-LandscapeRight.png image file, this file will take precedence.
Although you can include a Default.png file, and it will be used if no others are specified, I would consider it a best-practice to include all the relevant images needed by your application.
iPad Startup Orientation
Even though an iPad app may be started in any orientation, Apple recommends that you configure your application views upon startup in the preferred orientation inside the application:didFinishLaunchingWithOptions: method. Then, once the system notifies your application of the current orientation, you can arrange your views as needed.