setAreaOfInterest method of the RTRRecognitionService protocol
Sets the area on the frame where the text is to be found.
The size of the area of interest affects performance and the speed of convergence of the result. The best result is achieved when the area of interest does not touch the boundaries of the frame but has a margin of at least half the size of a typical printed character.
The rectangle specifying the area of interest. Pass CGRectZero as this parameter for the default area of interest (equal to the whole frame) to be selected.