cvFindContours函数功能：对图像进行轮廓检测，这个函数将生成一条链表以保存检测出的各个轮廓信息，并传出指向这条链表表头的指针。-cvFindContours Function: the image contour detection, this function will generate a list to save each contour information detected and outgoing point to this list header pointer.