The best guess of the uniform type identifier (UTI) for the format of the image source file. If specified, the value of this key must be a CFString object. This key can be provided in the options dictionary when you create a CGImageSource object.
Available in Mac OS X v10.4 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)