（1）
Mat src(128,128,CV_8UC1,Scalar(0));
imshow("src",src);
Point root_points[1][4];
root_points[0][0] = Point(51,31);
root_points[0][1] = Point(89,31);
root_points[0][2] = Point(89,69);
root_points[0][3] = Point(51,69);
const Point* ppt[1] = {root_points[0]};
int npt[] = {4};
polylines(src, ppt, npt, 1, 1, Scalar(255),1,8,0); 四个点组成1*4的数据，然后用指针进行访问
