GRAPHIC DRAWING/ERASING SYSTEM
PURPOSE:To rationalize graphic drawing and erasing and to improve its efficiency by allowing a processing means to execute the bit inversion processing of only the picture element data of a picture element requiring its processing and its flag based on the flag stored in a control memory. CONSTITUTI...
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Format: | Patent |
Sprache: | eng |
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Zusammenfassung: | PURPOSE:To rationalize graphic drawing and erasing and to improve its efficiency by allowing a processing means to execute the bit inversion processing of only the picture element data of a picture element requiring its processing and its flag based on the flag stored in a control memory. CONSTITUTION:A CPU 1 successively forms addresses in a frame memory 3 in accordance with a graphic to be drawn or erased by a program stored in a memory 2 based on an input from a keyboard and reads out the picture elements of the formed addresses and the picture element data of the picture elements in a pen point pattern around the addresses. At the time of drawing, inversion processing for finding out the exclusive OR of picture element data (P) and FFH (H indicates a hexa value) only when the least significant bit of the P, i.e. a flag, is '0' and the found value is written in the address. In case of erasing, the inversion processing for finding out the exclusive OR between the P and FFH is executed only when the flag is '1', and the found value is written in the address. Consequently, a graphic can be efficiently drawn or erased without generating a defect. |
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