ImageIO.framework

ImageIO.framework
Private Framework
Availabile	2.0 – present
Class Prefix	CGImage

The ImageIO framework is a direct port of the Mac OS X's equivalent, except that it is private on the iPhoneOS. Usage of this framework is clearly illustrated in this official reference:

• Using the ImageIO framework with Mac OS X 10.4 Tiger

Usually you don't need to use these functions, as UIKit's UIImage can read most of the formats.