| 摘要 |
PROBLEM TO BE SOLVED: To obtain an area for deciding gradation at high speed with a small circuit scale by obtaining an approximate area rate from the total of distances in a polygon, which is calculated based on the edges of the polygon and the crossing points of sub-scan lines. SOLUTION: A right/]eftcrossing point calculation means 101 takes in the coordinates of the apexes of the polygon and calculates the crossing point coordinates of the sub-scan lines obtained by dividing a scan line and the right/ left edges of the polygon. A distance calculation means 102 calculates the distances of the sub-scan lines in the polygon in a picture element in order from the picture element at the extremely left of the respective scan lines based on the crossing point. An area rate calculation means 103 adds up the distances of the sub-scan lines for the respective picture elements and divides the total value by the number of the sub-scan lines so as to obtain the approximate area rate. Thus, the approximate area rate for anti-aliasing can be obtained at high speed. |
