| 摘要 |
PURPOSE:To attain a painting-out even in a polygon having a recessed part by reversing display data between two points. CONSTITUTION:Respective points on a scanning line L (y=Y) to cross the recessed part are painted out as follows. Coordinates (Xalpha, Y) of a point alphaon a side AB are calculated at a coordinate calculating part 1, and its x- coordinate value is stored in a coordinate storing part 2. While coordinates (Xbeta, Y) of a point beta on a side BC are calculated at the coordinate calculating part 1, the x-coordinate Xalpha of the point alpha is fetched from the coordinate storing part 2, the two points (Xalpha, Y) and (Xbeta, Y) and the display data of points between them are reversed, and when the initial state of a picture memory is initially set to an 'all points white', a segment alphabeta is painted out in black. Coordinates (Xgamma, Y) of a point gamma on a side CD are calculated at the coordinate calculating part 1, and its x-coordinate value is stored in the coordinate storing part 2. While coordinates (Xdelta,, Y) of a point delta on a side AD are calculated at the coordinate calculating part 1, the x-coordinate Xgamma of the point gamma is fetched from the coordinate storing part 2, and the two points (Xgamma, Y) and (Xdelta, Y) and the display data of the points between the two points are reversed. |
