Interactive image coding for level 3 teletext origination

The development of Teletext and Videotex world-wide has been largely based upon the UK teletext standard, and has been aided by the availability of low-cost receiver decoder chips which meet this specification. Efficient magazine and page origination systems are also required for commercial success however. Level 3 of the display specification for Teletext and Videotex includes the provision of Dynamically Redefinable Character Sets (DRCS) which can be used to construct new characters or arbitrary graphic images. Although transmission equipment and receivers are potentially capable of supporting level 3 Teletext/Videotex, equipment suitable for originating level 3 images efficiently is not yet available. This paper describes how character recognition and clustering algorithms can be used to map from a pixel-based image to the level 3 character-oriented Teletext/Videotex display format. The mapping typically requires a compromise to be made between image coding efficiency, image accuracy and aesthetic factors. This is achieved using an interactive system where the image originator retains aesthetic control while varying the character recognition and clustering parameters