Segmented coding of digital image sequences

New algorithms, based on region-contour segmentation of images, are reported for application to low bit rate coding of monochrome and colour videotelephone image sequences. The prime importance of image edges in visual perception emphasises the need for their accurate representation in image compression. A centroid linkage region growing technique is employed to partition an image into homogeneous regions with distinct contours which are then coded and transmitted. Using a priori knowledge about 'head and shoulders' images, a method is developed which determines the location of the face for more accurate coding of this region. To achieve the low bit rates required for transmission of videotelephone images over the ISDN, motion compensation techniques have been included and good quality results are obtained at rates in the region of 64 kbit/s.