用水平扫描线从上到下扫描由点线段构成的多段构成的多边形。每根扫描线与多边形各边产生一系列交点。将这些交点按照x坐标进行分类，将分类后的交点成对取出，作为两个端点，以所填的色彩画水平直线。多边形被扫描完毕后，填色也就完成。(A polygon consisting of a plurality of segments consisting of a line segment from bottom to bottom by horizontal scanning. Each scan line produces a series of intersections with each polygon edge. The intersection points are classified according to the X coordinate, and the sorted intersection points are taken out in pairs as the two endpoint, and the horizontal lines are drawn with the filled colors. Polygon is after the scan is complete coloring.)