一个简单但很有代表性的几何变换的例子！从程序运行结果中能明示感觉到对一个三角形或四边形进行平移、缩放、旋转变换所留下的痕迹！-A simple but highly representative examples of geometric transformations! Results from the program to run to express feeling of a triangle or quadrilateral to pan, zoom, rotation of the traces left behind!