1. A video image data encoding and compression system comprising: an electronic video camera for providing digital image data corresponding to a scene viewed by the camera; a first store coupled to the camera output for storing said digital image data; an edge detector coupled to the camera for processing said digital image data to detect edges in the image data as sharp image luminance changes or discontinuities, said edge detector outputting digital edge map data representative of edges detected in the digital image data; a second store coupled to the edge detector output for storing said digital edge map data; a data processor coupled to said first and second stores and responsive to said digital image data and said digital edge map data for matching representative polynomial functions to segments of detected image luminance data extending from ones of said edges to adjacent ones of said edges; and means for outputting said digital edge map data together with digital data representative of said polynomial functions.