Icon and Image Sizes of IOS Apps
Every app needs an app icon and a launch file or image. In addition, some apps need custom icons to represent app-specific content, functions, or modes in navigation bars, toolbars, and tab bars.
For all images and icons, the PNG format is recommended. You should avoid using interlaced PNGs.
The standard bit depth for icons and images is 24 bits—that is, 8 bits each for red, green, and blue—plus an 8-bit alpha channel, for a total of 32 bits.