Character image data compression system

Claim 1

A character image data compression method for compressing matrix-type binary data having data elements formed in lines and in combination corresponding to a two-directional character image comprising the steps of: detecting the occurrence or non-occurrence of a character image segment in each data element of the matrix in each line; identifying a contact state in a vertical direction of said character image segment, by comparison of data in adjacent lines; and producing an output comprising a control code corresponding to said contact state, and variable length coded data corresponding to information of respectively different types in accordance with the type of contact state, said control code being applicable to all of said states, wherein the contact state in a vertical direction of said character image segment, is identified as any one of the following modes: an insertion mode (INS) in which no contact segment exists in a previous line, a simple contact different mode (DIF) in which one segment in the previous line contacts to one segment in a present line, a join mode (JOIN) in which a plurality of segments in the previous line contact to one segment in the present line, a fork mode (FORK) in which one segment in the previous line contacts to a plurality of segments in the present line, a join-fork mode (J-F) in which a plurality of segments in the previous line contact to a plurality of segments in the present line, and a deletion mode (DEL) in which no contact segment exists in the present line, and the encoded information includes a control code corresponding to the contact state, and also (a) information regarding a length (M) of a background portion prior to said segment and a length (N) of said segment in a case where said contact state corresponds to the insertion mode (INS), (b) information regarding difference amounts (S;D) at each end of respective contact segments and/or repeat number (K) of said simple contact difference mode of the succeeding lines, and/or polarity information (Ps;Pd) applying positive and negative polarities to said difference amounts (S;D) in a case where said contact state corresponds to the simple contact difference mode (DIF), (c) information regarding a number (Q) of segments to be joined and difference amounts (S;D) between extreme ends of a plurality of segments to be joined and ends of one joined segment, and polarity information (Ps;Pd) regarding said difference amounts (S;D) in a case where said contact state corresponds to the join mode (JOIN), (d) information regarding a number (Q) of forked segments and run-lengths (Mq;Nq) of formed segments in a case where said contact state corresponds to the fork mode (FORK), or (e) information regarding a number (Qj) of segments to be joined, the number (Qf) of the forked segments, and run-lengths (Mqf;Nqf) of said forked segments in a case where said contact state corresponds to join-fork mode (J-F), but when the contact state corresponds to the deletion mode, onlly a deletion mode control code (DEL) is produced.