edgelink

代码说明：

  在边缘检测之后得到的边缘不一定是完整的，利用这个函数可以将个线段生长一些，然后连接起来，成完整的形状(At the edge of the edge detection after get is not necessarily complete, use this function can be a line segment to grow some, and then connect, into the shape of a complete)