C++ OpenCV读写XML或YAML文件的方法详解

C++：FileStorage::FileStorage()
C++：FileStorage::FileStorage(const string& source, int flags, const string& encoding=string())

FileStorage fs("abc.xml", FileStorage::WRITE);

FileStorage fs;
fs.open("abc.xml",FileStorage::WRITE);

FileStorage fs(“abc.xml”, FileStorage::READ);

FileStorage fs;
fs.open(“abc.xml”, FileStorage::READ);

fs<<"iterationNr"<<100;

int itNr;
fs["iterationNr"]>>itNr;
itNr = (int) fs["iterationNr"];

// 数据结构的初始化
Mat R = Mat_<uchar>::eye(3,3);
Mat T = Mat_<double>::zeros(3, 1);
// 向Mat中写入数据
fs << "R" << R;
fs << "T" << T;
// 从Mat中读取数据
fs["R"]  >>  R;
fs["T"] >> T;

fs << "strings"<<"[";  //开始读入string文本序列
fs << "image1.jpg" << "Awesomeness" << "baboon.jpg";
fs << "]"; //关闭序列

fs << "Mapping";//开始读入Mapping文本
fs << "{" << "One" << 1;
fs << "Two" << 2 << "}";

```cpp
FileNode n = fs["strings"];//读取字符串序列以得到节点
if (n.type()!=FileNode::SEQ)
{
    cerr << "发生错误！字符串不是一个序列" << endl;
    return 1;
}
FileNodeIterator it = n.begin(),it_end = n.end(); //遍历节点
for(;it!=it_end;it++)
cout << (string)*it << endl;

#include<opencv2/opencv.hpp>
#include<time.h>
using namespace cv;

int main()
{
    //初始化
    FileStorage fs("test.yaml", FileStorage::WRITE);

    //开始文件写入
    fs << "frameCount" << 5;
    time_t rawtime; time(&rawtime);
    fs << "calibrationDate" << asctime(localtime(&rawtime));//读取时间量
     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);//畸变参数
    fs << "cameraMatrix" << cameraMatrix << "distCoeffs" << distCoeffs;//读取Mat型cameraMatrix，distcoeffs的内容
    fs << "feature" << "[";
    for (int i = 0; i < 3; i++)
    {
        int x = rand() % 640;
        int y = rand() % 480;
        uchar ibp = rand() % 256;

        fs << "{:" << "x" << x << "y" << y << "ibp" << "[:";
        for (int j = 0; j < 8; j++)
            fs << ((ibp >> j) & 1);
        fs << "]" << "}";
    }
    fs << "]";
    fs.release();
    printf("完毕，请在工程目录下查看文件-");
    getchar();

    return 0;
}

#include<opencv2/opencv.hpp>
#include<time.h>
using namespace cv;
using namespace std;

int main()
{
    //改变consolo字体颜色
    system("color 6F");

    //初始化
    FileStorage fs2("test.yaml", FileStorage::READ);

    //开始文件读取
    //法一,对FileNode操作
    int frameCount2 = (int)fs2["framecount2"];
    std::string date;//定义字符串 date

    //法二，使用FileNode运算符>>
    fs2["calibrationDate"] >> date;

    Mat cameraMatrix2, distCoeffs2;
    fs2["cameraMatrix"] >> cameraMatrix2;
    fs2["distCoeffs"] >> distCoeffs2;//读取

    cout << "frameCount2:" << frameCount2 << endl
        << "calibration date:" << date << endl
        << "camera matrix:" << cameraMatrix2 << endl
        << "distortion coeffs:" << distCoeffs2 << endl;

    FileNode feature = fs2["feature"];
    FileNodeIterator it = feature.begin(), it_end = feature.end();//定义it
    int idx = 0;
    std::vector<uchar>ibpval;//定义向量容器ibpal

    //使用FileNodeIterator历遍序列（读取）
    for (; it != it_end; it++, idx++)
    {
        cout << "feature#" << idx << ":";
        cout << "x=" << (int)(*it)["x"] << ",y=" << (int)(*it)["y"] << ",ibp:(";
        //也可以使用filenod>>std::vector操作符很容易读取数值阵列
        (*it)["ibp"] >> ibpval;
        for (int i = 0; i < (int)ibpval.size(); i++)
            cout << "" << (int)ibpval[i];
        cout << ")" << endl;
    }


    fs2.release();
    printf("读取完毕，请按任意键结束-");
    getchar();

    return 0;
}

/*
 * filestorage_sample demonstrate the usage of the opencv serialization functionality
 */
#include "opencv2/core.hpp"
#include <iostream>
#include <string>
using std::string;
using std::cout;
using std::endl;
using std::cerr;
using std::ostream;
using namespace cv;
static void help(char** av)
{
  cout << "\nfilestorage_sample demonstrate the usage of the opencv serialization functionality.\n"
      << "usage:\n"
      <<  av[0] << " outputfile.yml.gz\n"
      << "\n   outputfile above can have many different extensions, see below."
      << "\nThis program demonstrates the use of FileStorage for serialization, that is in use << and >>  in OpenCV\n"
      << "For example, how to create a class and have it serialize, but also how to use it to read and write matrices.\n"
      << "FileStorage allows you to serialize to various formats specified by the file end type."
          << "\nYou should try using different file extensions.(e.g. yaml yml xml xml.gz yaml.gz etc...)\n" << endl;
}
struct MyData
{
  MyData() :
    A(0), X(0), id()
  {
  }
  explicit MyData(int) :
    A(97), X(CV_PI), id("mydata1234")
  {
  }
  int A;
  double X;
  string id;
  void write(FileStorage& fs) const //Write serialization for this class
  {
    fs << "{" << "A" << A << "X" << X << "id" << id << "}";
  }
  void read(const FileNode& node)  //Read serialization for this class
  {
    A = (int)node["A"];
    X = (double)node["X"];
    id = (string)node["id"];
  }
};
//These write and read functions must exist as per the inline functions in operations.hpp
static void write(FileStorage& fs, const std::string&, const MyData& x){
  x.write(fs);
}
static void read(const FileNode& node, MyData& x, const MyData& default_value = MyData()){
  if(node.empty())
    x = default_value;
  else
    x.read(node);
}
static ostream& operator<<(ostream& out, const MyData& m){
  out << "{ id = " << m.id << ", ";
  out << "X = " << m.X << ", ";
  out << "A = " << m.A << "}";
  return out;
}
int main(int ac, char** av)
{
  cv::CommandLineParser parser(ac, av,
    "{@input||}{help h ||}"
  );
  if (parser.has("help"))
  {
    help(av);
    return 0;
  }
  string filename = parser.get<string>("@input");
  if (filename.empty())
  {
    help(av);
    return 1;
  }
  //write
  {
    FileStorage fs(filename, FileStorage::WRITE);
    cout << "writing images\n";
    fs << "images" << "[";
    fs << "image1.jpg" << "myfi.png" << "baboon.jpg";
    cout << "image1.jpg" << " myfi.png" << " baboon.jpg" << endl;
    fs << "]";
    cout << "writing mats\n";
    Mat R =Mat_<double>::eye(3, 3),T = Mat_<double>::zeros(3, 1);
    cout << "R = " << R << "\n";
    cout << "T = " << T << "\n";
    fs << "R" << R;
    fs << "T" << T;
    cout << "writing MyData struct\n";
    MyData m(1);
    fs << "mdata" << m;
    cout << m << endl;
  }
  //read
  {
    FileStorage fs(filename, FileStorage::READ);
    if (!fs.isOpened())
    {
      cerr << "failed to open " << filename << endl;
      help(av);
      return 1;
    }
    FileNode n = fs["images"];
    if (n.type() != FileNode::SEQ)
    {
      cerr << "images is not a sequence! FAIL" << endl;
      return 1;
    }
    cout << "reading images\n";
    FileNodeIterator it = n.begin(), it_end = n.end();
    for (; it != it_end; ++it)
    {
      cout << (string)*it << "\n";
    }
    Mat R, T;
    cout << "reading R and T" << endl;
    fs["R"] >> R;
    fs["T"] >> T;
    cout << "R = " << R << "\n";
    cout << "T = " << T << endl;
    MyData m;
    fs["mdata"] >> m;
    cout << "read mdata\n";
    cout << m << endl;
    cout << "attempting to read mdata_b\n";   //Show default behavior for empty matrix
    fs["mdata_b"] >> m;
    cout << "read mdata_b\n";
    cout << m << endl;
  }
  cout << "Try opening " << filename << " to see the serialized data." << endl << endl;
  //read from string
  {
    cout << "Read data from string\n";
    string dataString =
        "%YAML:1.0\n"
        "mdata:\n"
        "   A: 97\n"
        "   X: 3.1415926535897931e+00\n"
        "   id: mydata1234\n";
    MyData m;
    FileStorage fs(dataString, FileStorage::READ | FileStorage::MEMORY);
    cout << "attempting to read mdata_b from string\n";   //Show default behavior for empty matrix
    fs["mdata"] >> m;
    cout << "read mdata\n";
    cout << m << endl;
  }
  //write to string
  {
    cout << "Write data to string\n";
    FileStorage fs(filename, FileStorage::WRITE | FileStorage::MEMORY | FileStorage::FORMAT_YAML);
    cout << "writing MyData struct\n";
    MyData m(1);
    fs << "mdata" << m;
    cout << m << endl;
    string createdString = fs.releaseAndGetString();
    cout << "Created string:\n" << createdString << "\n";
  }
  return 0;
}