opencv Rodrigues函数调用问题

在做单目标定使用vc2013+opencv2.4.9环境写代码时，遇到Mat类型访问矩阵元素出错的bug，现在问题解决了，所以想在这里简单记一下，

Mat cameraMatrix = Mat(3, 3, CV_32FC1, Scalar::all(0)); /* 摄像机内参数矩阵 */
vector tvecsMat;  /* 每幅图像的旋转向量 */
vector rvecsMat; /* 每幅图像的平移向量 */
Mat rotation_matrix = Mat(3, 3, CV_32FC1, Scalar::all(0)); /* 保存每幅图像的旋转矩阵 */
Mat M1 = Mat(3, 4, CV_32FC1, Scalar::all(0));
vector M2;
vector M;  /* 投影矩阵M，由矩阵M1、M2相乘得 */

在用以下函数标定完得到内外参之后，

calibrateCamera(object_points, image_points_seq, image_size, cameraMatrix, distCoeffs, rvecsMat, tvecsMat, 0);

我再存入M1、M2矩阵中，最后得到投影矩阵M

在存入M1、M2的过程中，我遇到了Mat类型访问矩阵元素出错，以下语句：

//由内参得到M1
    M1.at<float>(0, 0) = cameraMatrix.at<float>(0, 0);
    M1.at<float>(0, 1) = cameraMatrix.at<float>(0, 1);
    M1.at<float>(0, 2) = cameraMatrix.at<float>(0, 2);
    M1.at<float>(0, 3) = 0;
    M1.at<float>(1, 0) = cameraMatrix.at<float>(1, 0);
    M1.at<float>(1, 1) = cameraMatrix.at<float>(1, 1);
    M1.at<float>(1, 2) = cameraMatrix.at<float>(1, 2);
    M1.at<float>(1, 3) = 0;
    M1.at<float>(2, 0) = cameraMatrix.at<float>(2, 0);
    M1.at<float>(2, 1) = cameraMatrix.at<float>(2, 1);
    M1.at<float>(2, 2) = cameraMatrix.at<float>(2, 2);
    M1.at<float>(2, 3) = 0;
    fout << "摄像机的M1矩阵：" << endl;
    fout << M1 << endl;

之前at<>内为double时，也有这样的错误，后来发现上面定义是CV_32FC1，所以改成了float问题就解决了，于是M2我也用了一样的方法，出错了，最后正确的代码如下：

for (int i = 0; i"第" << i + 1 << "幅图像的旋转向量：" << endl;
        fout << rvecsMat[i] << endl;
        /* 将旋转向量转换为相对应的旋转矩阵 */
        Rodrigues(rvecsMat[i], rotation_matrix);
        fout << "第" << i + 1 << "幅图像的旋转矩阵：" << endl;
        fout << rotation_matrix << endl;

        cout << rotation_matrix.at<double>(0, 0) << endl;

        fout << "第" << i + 1 << "幅图像的平移向量：" << endl;
        fout << tvecsMat[i] << endl << endl;
        /* 将旋转矩阵存入M2中 */
        Mat TempM2 = Mat(4, 4, CV_32FC1, Scalar::all(0));

        //cout << sizeof(CV_8UC1) << endl;
        //cout << sizeof(CV_32FC1) << endl;
        //cout << sizeof(int) << endl;
        //cout << sizeof(short) << endl;
        //cout << sizeof(long) << endl;
        //cout << sizeof(float) << endl;
        //cout << sizeof(double) << endl;


        TempM2.at<float>(0, 0) = rotation_matrix.at<double>(0, 0);
        TempM2.at<float>(0, 1) = rotation_matrix.at<double>(0, 1);
        TempM2.at<float>(0, 2) = rotation_matrix.at<double>(0, 2);
        TempM2.at<float>(0, 3) = tvecsMat[i].at<double>(0);
        TempM2.at<float>(1, 0) = rotation_matrix.at<double>(1, 0);
        TempM2.at<float>(1, 1) = rotation_matrix.at<double>(1, 1);
        TempM2.at<float>(1, 2) = rotation_matrix.at<double>(1, 2);
        TempM2.at<float>(1, 3) = tvecsMat[i].at<double>(1);
        TempM2.at<float>(2, 0) = rotation_matrix.at<double>(2, 0);
        TempM2.at<float>(2, 1) = rotation_matrix.at<double>(2, 1);
        TempM2.at<float>(2, 2) = rotation_matrix.at<double>(2, 2);
        TempM2.at<float>(2, 3) = tvecsMat[i].at<double>(2);
        TempM2.at<float>(2, 0) = 0;
        TempM2.at<float>(2, 1) = 0;
        TempM2.at<float>(2, 2) = 0;
        TempM2.at<float>(2, 3) = 1;
        cout << TempM2 << endl;
        M2.push_back(TempM2);
        fout << "摄像机的M2矩阵：" << endl;
        fout << M2[i] << endl;
    }

之前我用的所有矩阵对应元素访问语句如下：

TempM2.at<float>(0, 0) = rotation_matrix.at<float>(0, 0);

我的想法是M1、cameraMatrix、TempM2、rotation_matrix都是CV_32FC1型，所以所有at<>都用的float，后来出错后，单步调试找原因，最后发现

Rodrigues(rvecsMat[i], rotation_matrix);

是这个函数这里的问题，在调用这个函数之前

cout << rotation_matrix.at<float>(0, 0) << endl;

是对的，这个函数作用之后，就要用double访问了，后面好不容易找到了Rodrigues函数的源码，在calibration.cpp中，看了仍然没搞明白，时间原因就没有细究了，有时间再回来看看~

所以要注意Rodrigues函数会改变mat的数值类型。