Before iOS7 I use UIGetScreenImage() to take screenshot of the entire screen at any view of the iOS, not only inside my tweak app but also views of other apps. 
In iOS7, when I use this function I got implicit declaration of function error, then I added a prototype in the code as blow, this error disappeared, but got  ld: symbol(s) not found for architecture arm64 error. It looks like 'UIGetScreenImage' has been deleted in iOS7, is it? If so, what can I do to replace it?
CGImageRef UIGetScreenImage(void);