用opengl实现bresenham算法画圆，先画1/8个圆，再借助圆的对称性，画出其余部分-Use opengl achieve bresenham algorithm Circle, first draw the 1/8 round, and then with the symmetry of the circle to draw the rest

用OpenGL实现中点Bresenham算法画直线与圆，改进Bresenham算法画直线-The midpoint of the Bresenham algorithm for drawing a straight line and circle, using OpenGL to improve the Bresenham algorithm draw a straight line