鼠标操作绘制多边形，可以任意移动旋转放大绘制的多边形，检测鼠标的位置，当鼠标接近多边形顶点时，拖动鼠标来改变多边形顶点的位置；当鼠标接近做边形的边时，在该边上任意加入顶点。-Mouse drawing polygons, you can draw any move to enlarge the polygon rotation to detect the mouse position, when the mouse near the polygon vertices, the drag the mouse to change the location of the polygon vertices　when the mouse-shaped side-by-doing approach, when, at the edge of arbitrary join the vertices.