Patent US 3,980,809

The present invention relates to pictorial data transmission systems for transmitting fixed images from one point to another. The invention employs two modes for encoding successive blocks of elements (typically four elements by four elements). If a data block contains black elements, the system sequentially compares a series of a selected vocabulary of simple geometric patterns in a pattern library, with the pattern of black elements in the data block. The library of reference patterns are compared in the order of most black to least black. The bit compare logic of the subject invention determines when all the elements of a first reference pattern compare with elements present in the data block. The bit compare logic then indicates whether any bit locations in the data block are leftover after the comparison with the first reference pattern. Leftover elements are matched with a second reference pattern which in turn is encoded and transmitted on an output line. The matching process will continue until the data block has been completely encoded as a composite of reference patterns. All reference patterns matched are encoded and sequentially transmitted on an output line for transmission, storage or display. The second mode of operation for the subject invention is to employ run length of encoding of successive white spaces.