这是一个生成圆周的源代码，首先用Bresenham算法生成八分圆坐标，再计算出8个对称点，生成圆周的所有点之后，按y值排序，转换成线段表。-This is a generation of source code circumference, first using Bresenham algorithm generated nearly circular coordinates, and then work out eight symmetry, circumferential generate all points, according y values, in order of conversion segment table.