A flexible polygon representation of multiple overlapping regions of interest for wavelet-based image coding

Image transmission over low-bandwidth channels can be speeded up if the image coding mechanism supports regions of interest (RoIs). By such a scheme, image parts not belonging to RoIs can be encoded at a lower bitrate. This paper describes a flexible dynamic RoI scheme which supports the definition of arbitrarily-shaped RoIs before the start of the transmission process and the refinement of a partially transmitted image by the definition of new RoIs at any time during image transmission. The overhead to represent RoIs is kept as small as possible by exploiting a polygon-based RoI representation. Span arithmetic on a multiresolution grid is used to support the redundancy-free transmission of overlapping RoIs.