Opencv将数据保存到xml、yaml / 从xml、yaml读取数据

• Opencv提供了读写xml、yaml的类实现：
  
• 本文重点参考：https://blog.csdn.net/cd_yourheart/article/details/122705776?spm=1001.2014.3001.5506，并将给出文件读写的具体使用实例。

1. 官方例程

1.1 写数据

#include "opencv2/core.hpp"
#include <time.h>
using namespace cv;
int main(int, char** argv)
{FileStorage fs("test.yml", FileStorage::WRITE);fs << "frameCount" << 5;time_t rawtime; time(&rawtime);fs << "calibrationDate" << asctime(localtime(&rawtime));Mat cameraMatrix = (Mat_<double>(3,3) << 1000, 0, 320, 0, 1000, 240, 0, 0, 1);Mat distCoeffs = (Mat_<double>(5,1) << 0.1, 0.01, -0.001, 0, 0);fs << "cameraMatrix" << cameraMatrix << "distCoeffs" << distCoeffs;fs << "features" << "[";for( int i = 0; i < 3; i++ ){int x = rand() % 640;int y = rand() % 480;uchar lbp = rand() % 256;fs << "{:" << "x" << x << "y" << y << "lbp" << "[:";for( int j = 0; j < 8; j++ )fs << ((lbp >> j) & 1);fs << "]" << "}";}fs << "]";fs.release();return 0;
}

output :

%YAML:1.0
frameCount: 5
calibrationDate: "Fri Jun 17 14:09:29 2011\n"
cameraMatrix: !!opencv-matrixrows: 3cols: 3dt: ddata: [ 1000., 0., 320., 0., 1000., 240., 0., 0., 1. ]
distCoeffs: !!opencv-matrixrows: 5cols: 1dt: ddata: [ 1.0000000000000001e-01, 1.0000000000000000e-02,-1.0000000000000000e-03, 0., 0. ]
features:- { x:167, y:49, lbp:[ 1, 0, 0, 1, 1, 0, 1, 1 ] }- { x:298, y:130, lbp:[ 0, 0, 0, 1, 0, 0, 1, 1 ] }- { x:344, y:158, lbp:[ 1, 1, 0, 0, 0, 0, 1, 0 ] }

1.2 读数据

FileStorage fs2("test.yml", FileStorage::READ);// first method: use (type) operator on FileNode.
int frameCount = (int)fs2["frameCount"];
String date;// second method: use FileNode::operator >>
fs2["calibrationDate"] >> date;
Mat cameraMatrix2, distCoeffs2;
fs2["cameraMatrix"] >> cameraMatrix2;
fs2["distCoeffs"] >> distCoeffs2;
cout << "frameCount: " << frameCount << endl<< "calibration date: " << date << endl<< "camera matrix: " << cameraMatrix2 << endl<< "distortion coeffs: " << distCoeffs2 << endl;
FileNode features = fs2["features"];
FileNodeIterator it = features.begin(), it_end = features.end();
int idx = 0;
std::vector<uchar> lbpval;// iterate through a sequence using FileNodeIterator
for( ; it != it_end; ++it, idx++ )
{cout << "feature #" << idx << ": ";cout << "x=" << (int)(*it)["x"] << ", y=" << (int)(*it)["y"] << ", lbp: (";// you can also easily read numerical arrays using FileNode >> std::vector operator.(*it)["lbp"] >> lbpval;for( int i = 0; i < (int)lbpval.size(); i++ )cout << " " << (int)lbpval[i];cout << ")" << endl;
}
fs2.release();

2. 读写xml

#include <iostream>
#include "opencv2/opencv.hpp"using namespace std;#define WRITE_OR_READint main() {
//===========将数据写入到xml文件中================
#ifdef WRITE_OR_READ string name = "insomnia";int age = 18;float height = 1.83;char sex = 'M';cv::Mat matrix_eye = cv::Mat::eye(3, 3, CV_64F);cv::FileStorage fs("./test.xml", cv::FileStorage::WRITE);//会覆盖当前文件，不存在则新建文件if (fs.isOpened()){fs << "name" << name << "age" << age << "height" << height << "sex" << sex;//可以连续写入fs << "matrix_eye" << matrix_eye;//也可以依次写入fs.release();//release after used}
//===========从xml文件中读取数据================
#else string name;int age;float height;char sex;cv::Mat matrix_eye;cv::FileStorage fs("./test.xml", cv::FileStorage::READ);if (fs.isOpened()) {fs["name"] >> name;fs["age"] >> age;fs["height"] >> height;int temp;fs["sex"] >> temp;//这里不能直接读到char，所以转换了一下sex = (char)temp;fs["matrix_eye"] >> matrix_eye;fs.release();cout << "name: " << name << endl;cout << "age: " << age << endl;cout << "height: " << height << endl;cout << "sex: " << sex << endl;cout << "matrix_eye: " << endl << matrix_eye << endl;cout << "matrix_eye.size().height: " << matrix_eye.size().height << endl;cout << "matrix_eye.at<double>(1, 0): " << matrix_eye.at<double>(1, 0) << endl;}
#endifreturn 0;
}

将数据写入到xml文件后，打开查看一下
格式是自动生成的，只是将数据填充了进去。可以看到第一行是xml版本信息，不用考虑。第二行和最后一行是最外层的标签。

然后所有保存的数据都是一个并列的关系，同等级。只是像Mat这种数据类型，又有细分属性而已。

从xml文件中读取一下数据，看下输出结果

3. 读写yaml

#include<opencv2/opencv.hpp>
#include<iostream>using namespace std;
using namespace cv;//#define WRITE_OR_READint main()
{
#ifdef WRITE_OR_READ//1.创建文件cv::FileStorage fwrite("./test.yaml", cv::FileStorage::WRITE);//2.写入数据string name = "insomnia";int age = 18;float height = 1.83;char sex = 'M';cv::Mat matrix_eye = cv::Mat::eye(3, 3, CV_64F);fwrite << "name " << name;fwrite << "age " << age;fwrite << "height " << height;fwrite << "sex " << sex;fwrite << "matrix_eye " << matrix_eye;//3.关闭文件fwrite.release();return 0;
#else//1.读取文件指针	string strSettingsFile = "./test.yaml";cv::FileStorage fread(strSettingsFile.c_str(), cv::FileStorage::READ);//2.判断是否打开成功if (!fread.isOpened()){cout << "Failed to open settings file at: " << strSettingsFile << endl;return 0;}else cout << "success to open file at: " << strSettingsFile << endl;//3.打开文件后读取数据string name;int age;float height;char sex;cv::Mat matrix_eye;fread["name"] >> name;fread["age"] >> age;fread["height"] >> height;int temp;fread["sex"] >> temp;sex = (char)temp;fread["matrix_eye"] >> matrix_eye;cout << "name=" << name << endl;cout << "age=" << age << endl;cout << "height=" << height << endl;cout << "sex=" << sex << endl;cout << "matrix_eye=" << endl << matrix_eye << endl;cout << matrix_eye.size().height << endl;//4.关闭文件fread.release();return 0;
#endif}

保存的yaml文件

读取文件的结果

4. 保存矩阵与点集

//写数据
cv::FileStorage fs;
std::string label_ = "abc.xml";
fs.open(label_.c_str(), cv::FileStorage::WRITE);std::string str_ = "image" + std::to_string(i+1);
cv::Mat _pts(p_result); //p_result define:std::vector<cv::Point2f>p_result;
fs << str_ << _pts;
fs.release();//**************************
//读数据
cv::FileStorage fs;
fs.open( "abc.xml", cv::FileStorage::READ);
cv::Mat m_pts;
fs[str] >> m_pts;
std::vector<cv::Point2f>pts;
for (int i = 1; i < m_pts.rows; ++i)
{cv::Point2f _pt(m_pts.ptr<float>(i, 0)[0], m_pts.ptr<float>(i, 0)[1]);pts.push_back(_pt);std::cout << _pt << "\n";
}