Table 5-4 (about half way down) this Apple doc page suggests sizes for the launch images for iOS:
Device Portrait Landscape
iPhone and iPod touch 320 x 480 pixels Not supported
640 x 960 pixels (@2x)
iPhone 5 640 x 1136 pixels (@2x) Not supported
iPad 768 x 1024 pixels 1024 x 768 pixels
1536 x 2048 pixels (@2x) 2048 x 1536 pixels (@2x)
My app has a photo background at launch so at present I have to use GIMP to crop/resize the photo for each of these, which is fiddly.
Is there a tool to do this automatically ?
One other complication is that there are a couple of logos in the image too, ideally they will be in separate layers, so they can stay legible and tidily laid out for each size/orientation.