1. Apparatus for encoding a segmented image to produce an output encoded image which may be decoded to reproduce an image which substantially matches the segmented image, said apparatus comprising: means for processing the segmented image data to produce processed segmented image data which represents the image as a sequence of encoded segment borders, each border being represented by a sequence of displacements between respective border pixels that define a path around the border; means for encoding the processed segmented image data to produce encoded segmented image data, in which each group of N values, where N is an integer, in each sequence of the processed segmented image is encoded into a single sequence value of the encoded segmented image data and a code value complementary to the encoded sequence value; and variable length encoding means for processing encoded segmented image data using a predetermined set of variable length codes to produce variable-length encoded data representing the segmented image, as the output encoded image.