invalid context 0x0 under iOS 7.0 and system degradation

Error:

<Error>: CGContextAddEllipseInRect: invalid context 0x0. This is a serious error. This application, or a library it uses, is using an invalid context  and is thereby contributing to an overall degradation of system stability and reliability. This notice is a courtesy: please fix this problem. It will become a fatal error in an upcoming update.

Answer:

UIGraphicsBeginImageContext( size ); CGContextRef context = UIGraphicsGetCurrentContext();

make sure the size.width or size.height is not 0, 

you can add symbol breakpoint to CGPostError to check

参考：http://stackoverflow.com/questions/19599266/invalid-context-0x0-under-ios-7-0-and-system-degradation%3C/p%3E