本程序完成的是放大镜功能，这里的放大镜是一个正方形的形状，它是贴在屏幕上，所以无论用户如何修改视点都不会有影响。程序通过OpenGL实现-The completion of this program is a magnifying glass feature, where the magnifying glass is a square shape, which is attached to the screen, so no matter how users can modify the po