Opencv error unspecified error incorrect element name operator <<

1.问题描述

今天在用opencv的FileStorage类进行xml文件读写操作的时候报了个错。
源代码如下所示：

#include <opencv2\opencv.hpp>
#include <vector>
#include <iostream>

using namespace std;
using namespace cv;

typedef pair<Point, double> PointTemper;

int main()
{

    vector<PointTemper> a;
    a.push_back(make_pair(Point(1, 1), 2.5));
    a.push_back(make_pair(Point(2, 2), 3.4));

    FileStorage fs("a.yml", FileStorage::WRITE);
    if (!fs.isOpened())
    {
        cout << "cannot open xml file to write" << endl;
        getchar();
        return 0;
    }

    fs << "a_size" << (int)(a.size());

    fs << "1-th" << "[";
    fs << "{" << "point_x" << a[0].first.x << "point_y" << a[0].first.y << "temper" << a[0].second << "}";
    fs << "{" << "point_x"