HALFTONE DOT IMAGE PROCESSING METHOD AND ITS DEVICE

摘要

PURPOSE:To enable generation of a halftone dot pattern of any large size at high speed by generating a periodic halftone dot pattern decided exclusively by a dot gradient indicating a halftone dot angle or loading a periodic pattern generated in advance. CONSTITUTION:The period (a<2>+b<2>) of a halftone dot pattern is set in an X address generation circuit 109 and a Y address generation circuit 110 through a clock generation/timing control circuit 105. Consequently, a periodic halftone dot pattern in a square region with one side of (a<2>+b<2>) dot size is repeatedly read from a halftone dot pattern storage memory 108. As a result, a halftone dot pattern of any large size is generated and entered into a data conversion table memory 112. A series of density image data is read from a line buffer and entered into a comparison circuit 114, passing through a selector 117. After this, the data is compared with the above-mentioned halftone dot data in terms of size and the comparison results are output in bits serially. These serial bits are converted to parallel bits by a shift register 118 and this data is sent to a laser beam printer 119 to record a halftone dot image.