本代码包含以下算法的演示：

直线：DDA算法生成直线，中点算法生成直线，Bresenham算法生成直线。

圆：中点画圆，Bresenham画圆。

椭圆：中点画椭圆。

区域填充：多边形扫描线填充，种子扫描线填充。-This code contains a demonstration of the following algorithm:

Direct Line: DDA algorithm to generate a straight line, the midpoint algorithm to generate a straight line, Bresenham algorithm to generate a straight line.

Round: the mid-point circle, Bresenham s circle.

Oval: in dotted ellipse.

The area filling: polygon scan line filling, seed scan line filling.