计算机图形学简单绘图系统,该基本绘图系统的关键类为：绘图类CGraph。它由CClientDC类派生类，其派生类型为Public,功能是用来绘图，-Computer graphics drawing system, the basic drawing system key is: drawing class CGraph. It consists of the CClientDC class, the derived type is Public, function is used to dra