实现图形学中的DDA算法、中点画线算法和八分法画圆算法，已将物理坐标映射成逻辑坐标，象素点用一个小圆点代替。-The DDA algorithm to achieve graphics, the eight law stipple-line algorithms and draw a circle algorithm, has been mapped to the physical coordinates of the logical coordinates of pixels instead of using a small dot.