[Declared in "../coresys/common/kdu_roi_processing.h"]
This abstract base class defines an interface to a derived object which is able to supply ROI mask information. It has no state (no data members) of its own. The pull function retrieves a single line of ROI information from some tile-component, at some resolution or in some subband. The scope depends upon the object ( kdu_roi_level or kdu_roi_image) which supplied the relevant interface.