准确提取txt中保存的Mat（矩阵）数据，不损失精度

由于近期研究相机标定以及三维重建工作，因此需要将标定程序以及重建程序分开，这样只需运行标定程序一次，之后重建时将各个矩阵从txt中读出即可，因此记录一下提取opencv保存的Mat数据的过程（可以用于矩阵提取的其他场合）。

原理：txt中通过ofstream保存的符号无非“[”、“, ”、“;”、“]”，因此将这些符号拆分出来就可以了。

保存的矩阵如图所示：

话不多说，直接贴程序。

//拆分字符串的函数
std::vector<std::string> split(std::string str, std::string pattern)
{
    std::vector<std::string> ret;
    if (pattern.empty()) return ret;
    size_t start = 0, index = str.find_first_of(pattern, 0);
    while (index != str.npos)
    {
        if (start != index)
            ret.push_back(str.substr(start, index - start));
        start = index + 1;
        index = str.find_first_of(pattern, start);
    }
    if (!str.substr(start).empty())
        ret.push_back(str.substr(start));
    return ret;
}

//从txt中获取矩阵的函数
void getMatrix(std::ifstream& ifs1,cv::Mat& cameraMatrix)
{
    std::vector<double> matrix_cam;

    std::string test_str;
    while (std::getline(ifs1, test_str))//逐行读取数据
    {
        //std::cout << test << std::endl;
        //string->char *
        std::string split1 = "[";
        //分割字符串
        std::vector<std::string> str1 = split(test_str, split1);//第一次拆分

        std::string split2 = ", ";
        std::vector<std::string> str2;
        for (int i = 0; i < str1.size(); i++)
        {
            std::vector<std::string> str_temp = split(str1[i], split2);//第二次拆分
            for (int j = 0; j < str_temp.size(); j++)
            {
                str2.push_back(str_temp[j]);
            }
        }
        //第三次拆分
        std::string split3 = ";";
        std::vector<std::string> str3;
        for (int i = 0; i < str2.size(); i++)
        {
            std::vector<std::string> str_temp2 = split(str2[i], split3);
            for (int j = 0; j < str_temp2.size(); j++)
            {
                str3.push_back(str_temp2[j]);
            }
        }
        //第四次拆分
        std::string split4 = "]";
        std::vector<std::string> str4;
        for (int i = 0; i < str3.size(); i++)
        {
            std::vector<std::string> str_temp3 = split(str3[i], split4);
            for (int j = 0; j < str_temp3.size(); j++)
            {
                str4.push_back(str_temp3[j]);
            }

        }

        for (int i = 0; i < str4.size(); i++)
        {
            double temp = std::stod(str4[i]);
            matrix_cam.push_back(temp);
        }
    }

    int k = 0;
    if (matrix_cam.size() != cameraMatrix.rows * cameraMatrix.cols)
        std::cout << "拆分的矩阵数据不对！" << std::endl;
    for (int i = 0; i < cameraMatrix.rows; i++)
    {
        for (int j = 0; j < cameraMatrix.cols; j++)
        {

            double temp = matrix_cam[k];
            cameraMatrix.at<double>(i, j) = temp;
            k++;
        }
    }
}

main函数中的程序：

std::ifstream ifs1;
    ifs1.open("../light_plan_calibration/camera_parameters.txt", std::ios::in);
    if (!ifs1)
    {
        std::cout << "camera_parameters.txt 无法打开！" << std::endl;
        exit(1);
    }

    //获取相机内参的矩阵
    cv::Mat cameraMatrix = cv::Mat(3, 3, CV_64FC1, cv::Scalar::all(0));

    getMatrix(ifs1, cameraMatrix);
    //std::cout << cameraMatrix << std::endl;
    //获取相机畸变矩阵
    std::ifstream ifs2;
    ifs2.open("../light_plan_calibration/discoeffs_parameters.txt", std::ios::in);
    if (!ifs2)
    {
        std::cout << "discoeffs_parameters.txt 无法打开！" << std::endl;
        exit(1);
    }
    cv::Mat distCoeffs = cv::Mat(1, 5, CV_64FC1, cv::Scalar::all(0));
    getMatrix(ifs2, distCoeffs);
    //std::cout << distCoeffs << std::endl;

    //获取旋转平移矩阵
    std::ifstream ifs3;
    ifs3.open("../light_plan_calibration/rvecs_parameters.txt", std::ios::in);
    if (!ifs3)
    {
        std::cout << "rvecs_parameters.txt 无法打开！" << std::endl;
        exit(1);
    }
    cv::Mat tvecsMat = cv::Mat(3, 1, CV_64FC1, cv::Scalar::all(0));
    getMatrix(ifs3, tvecsMat);
    //std::cout << tvecsMat << std::endl;

    std::ifstream ifs4;
    ifs4.open("../light_plan_calibration/tvecs_parameters.txt", std::ios::in);
    if (!ifs4)
    {
        std::cout << "tvecs_parameters.txt 无法打开！" << std::endl;
        exit(1);
    }
    cv::Mat rvecsMat = cv::Mat(3, 1, CV_64FC1, cv::Scalar::all(0));
    getMatrix(ifs4, rvecsMat);
    //std::cout << rvecsMat << std::endl;

    //获取光平面系数
    std::vector<double> light_plane;
    std::ifstream ifs5;
    ifs5.open("../light_plan_calibration/plane_parameters.txt", std::ios::in);
    if (!ifs5)
    {
        std::cout << "plane_parameters.txt 无法打开！" << std::endl;
        exit(1);
    }
    cv::Mat planeMat = cv::Mat(1, 4, CV_64FC1, cv::Scalar::all(0));
    getMatrix(ifs5, planeMat);
    for (int i = 0; i < planeMat.rows; i++)
    {
        for (int j = 0; j < planeMat.cols; j++)
        {
            light_plane.push_back(planeMat.at<double>(i, j));
        }
    }
    
    //获取传送带位移矩阵
    std::ifstream ifs6;
    ifs6.open("../light_plan_calibration/step_parameters.txt", std::ios::in);
    if (!ifs6)
    {
        std::cout << "step_parameters.txt 无法打开！" << std::endl;
        exit(1);
    }
    cv::Mat step = cv::Mat(3, 1, CV_64FC1, cv::Scalar::all(0));
    getMatrix(ifs6, step);
    std::cout << step << std::endl;

如果有错误，还请指正。