| 摘要 |
PURPOSE:To paint out only the inside except the boundary of a polygon in either of the replace mode and the EOR mode by providing a detecting means and a paint out means with respect to the parts of upper sides of trapezoids which do not overlap the boundary of the polygon. CONSTITUTION:A trapezoid dividing means 2 divides the polygon into trapezoids in accordance with apex data of the polygon stored in an apex data storage means 1. With respect to each of divided trapezoids, a trapezoid inside painting- out means 3 paints out the inside of the trapezoid with a desired pattern and a paint-out straight line detecting means 4 detects a part (straight line) of the upper side of the trapezoid, which does not overlap the boundary of the polygon and a straight line painting-out means 5 paints out the detected straight line with a prescribed pattern. Thus, only the inside of the polygon given with apex data is painted out and it is painted out in either of the EOR mode (the mode of Laster arithmetic where new data is written while operating exclusive OR between this data and already written data) and the replace mode. |
