这是图形学中的多边形裁剪程序，可以在文档中画出一个区域，在用鼠标点击画出多边形的几个顶点，这时多边形就会按照原来画出的区域进行裁剪-this is the polygon graphics cutting procedures, the documents paint a regional, using mouse clicks draw polygons several vertex, then according to the original polygon will be the hea