. File Input and Output using XML and YAML files

#include <opencv2/core.hpp>
#include
#include

using namespace cv;
using namespace std;

class MyData
{
public:
MyData() : A(0), X(0), id()
{}
explicit MyData(int) : A(97), X(CV_PI), id(“mydata1234”) // explicit to avoid implicit conversion
{}
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”];
}
public: // Data Members
int A;
double X;
string id;
};
//These write and read functions must be defined for the serialization in FileStorage to work
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);
}
// This function will print our custom class to the console
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)
{

string filename = "/home/chang/projects/opencv_GPU_example/chang.xml";
{ //write
    Mat R = Mat_<uchar>::eye(3, 3),
        T = Mat_<double>::zeros(3, 1);
    MyData m(1);
    FileStorage fs(filename, FileStorage::WRITE);
    fs << "iterationNr" << 100;
    fs << "strings" << "[";                              // text - string sequence
    fs << "image1.jpg" << "Awesomeness" << "../data/baboon.jpg";
    fs << "]";                                           // close sequence
    fs << "Mapping";                              // text - mapping
    fs << "{" << "One" << 1;
    fs <<        "Two" << 2 << "}";
    fs << "R" << R;                                      // cv::Mat
    fs << "T" << T;
    fs << "MyData" << m;                                // your own data structures
    fs.release();                                       // explicit close
    cout << "Write Done." << endl;
}
{//read
    cout << endl << "Reading: " << endl;
    FileStorage fs;
    fs.open(filename, FileStorage::READ);
    int itNr;
    //fs["iterationNr"] >> itNr;
    itNr = (int) fs["iterationNr"];
    cout << itNr;
    if (!fs.isOpened())
    {
        cerr << "Failed to open " << filename << endl;
        return 1;
    }
    FileNode n = fs["strings"];                         // Read string sequence - Get node
    if (n.type() != FileNode::SEQ)
    {
        cerr << "strings is not a sequence! FAIL" << endl;
        return 1;
    }
    FileNodeIterator it = n.begin(), it_end = n.end(); // Go through the node
    for (; it != it_end; ++it)
        cout << (string)*it << endl;
    n = fs["Mapping"];                                // Read mappings from a sequence
    cout << "Two  " << (int)(n["Two"]) << "; ";
    cout << "One  " << (int)(n["One"]) << endl << endl;
    MyData m;
    Mat R, T;
    fs["R"] >> R;                                      // Read cv::Mat
    fs["T"] >> T;
    fs["MyData"] >> m;                                 // Read your own structure_
    cout << endl
        << "R = " << R << endl;
    cout << "T = " << T << endl << endl;
    cout << "MyData = " << endl << m << endl << endl;
    //Show default behavior for non existing nodes
    cout << "Attempt to read NonExisting (should initialize the data structure with its default).";
    fs["NonExisting"] >> m;
    cout << endl << "NonExisting = " << endl << m << endl;
}
cout << endl
    << "Tip: Open up " << filename << " with a text editor to see the serialized data." << endl;
return 0;

}