Picture Description Instructions (Pdi) for the Telidon Videotex System

摘要

The Telidon Videotex system is a method by which information is accessed from central data bases by the general public. By the use of a domestic home television receiver augmented by a microcomputer controlled interface device a user can access pages of graphical and textual information over a public common carrier communications facility such as the telephone network, a cable television line, or in a broadcast television signal. A coding scheme which encodes a picture into the geometric drawing elements which compose it is described. The picture description instructions are an alpha geometric coding model and are based on the primitives of POINT, LINE, ARC, RECTANGLE, POLYGON, point by point BIT encoded images, and TEXT encoded as ASCII characters. A detailed specification of the code as well as a description of the principles which make it independent of communications channel and display hardware is provided.