本程序通过OpenGL和shader实现了圆形放大镜，并且在放大镜的中间贴上了一个十字瞄准镜的纹理，就像cs中的狙击枪的放大效果一样。-This procedure achieved through OpenGL and shader round magnifying glass, and in the middle of the magnifying glass labeled a cross-sight of the texture, like cs guns in the sniper l