JPS6447169A - Compression system for dot picture data - Google Patents

Abstract

PURPOSE:To compress a dot picture data efficiently by obtaining a coordinate of a picture element in the in-phase relation with an object picture element of a dot picture from parameter information including a dot angle or the like and using plural same phase picture elements having the highest correlation in revising the dot angle through the reference thereby applying prediction coding. CONSTITUTION:A dot picture signal obtained by scanning a dot picture is given to a RAM 41 and a register 0 for each picture element and an output of a register 0 is given directly and an output of the RAM 41 is given via registers 1-9 to a multiplexer 45 being a selection means respectively. In applying prediction from lots of picture elements, since the prediction table is too large to make the prediction difficult, the near part of the object picture, the same phase picture elements, and the near picture element thereof are selected as reference picture elements. Then an arithmetic circuit 43 executes costheta calculation from the dot angle by using a screen line number and dot density and the value is referenced with a reference picture element selection table in the ROM 44 and the result is stored in the ROM 46 as a prediction signal.