绘图库
1. 设计和实现一个图形函数库，具有绘制直线
段、任意圆弧、椭圆弧、多边形区域的阴影填
充和颜色填充等功能。（仅调用画点函数）
Windows API: setpixel(hdc,x,y,color),Drawing 1. Design and Implementation of a graphics library, with the straight-line drawing, arbitrary arc, elliptical arc, polygon area fill and color filled the shadow functions. (Just call paintings point function) Windows API: setpixel (hdc, x, y, color)