binaryStorage

OpenCV HDF5 binary storage format alternative to xml/yml FileStorage.

Below you will find the same example used in OpenCV documentation to demonstrate the compatibility/similarity between our implementation and the current xml/yml storage current available in OpenCV.

The implementation allows you to save user defined and OpenCV types using the hdf5 file format.

To avoid name collision the following class names are renamed: FileStorage -> Storage, FileNode -> StorageNode, and FileNodeIterator -> NodeIterator.

#include "h5persistence.hpp"

using namespace cv;
using namespace std;

class MyData
{
public:
    MyData() : A(0), X(0), id()
    {}

    // explicit to avoid implicit conversion
    explicit MyData(int)
        : A(97), X(CV_PI), id("mydata1234")
    {}

    //Write serialization for this class
    //Using cv::Storage instead of cv::FileStorage
    void write(cv::Storage& fs) const
    {
        fs << "{" << "A" << A << "X" << X << "id" << id << "}";
    }

    //Read serialization for this class
    //Using cv::StorageNode instead of cv::FileNode
    void read(const cv::StorageNode& node)
    {
        A = (int)node["A"];
        X = (double)node["X"];
        id = (string)node["id"];
    }
    // Data Members
public:
    int A;
    double X;
    string id;
};

//These write and read functions must be defined for
//the serialization in FileStorage to work.
//Note the changes cv::Storage and cv::StorageNode
static void write(cv::Storage& fs, const std::string&, const MyData& x)
{
    x.write(fs);
}
static void read(const cv::StorageNode& 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 = "example.h5";
    //write
    {
        Mat R = Mat_<uchar>::eye(3, 3),
        T = Mat_<double>::zeros(3, 1);
        MyData m(1);

        Storage fs(filename, Storage::WRITE);

        fs << "iterationNr" << 100;
        // text - string sequence
        fs << "strings" << "[";
        fs << "image1.jpg" << "Awesomeness" << "baboon.jpg";
        // close sequence
        fs << "]";

        // text - mapping
        fs << "Mapping";
        fs << "{" << "One" << 1;
        fs <<        "Two" << 2 << "}";

        // cv::Mat
        fs << "R" << R;
        fs << "T" << T;

        // your own data structures
        fs << "MyData" << m;

        // explicit close
        fs.release();
        cout << "Write Done." << endl;
    }
    //read
    {
        cout << endl << "Reading: " << endl;
        cv::Storage fs;
        fs.open(filename, cv::Storage::READ);

        int itNr;
        //fs["iterationNr"] >> itNr;
        itNr = (int) fs["iterationNr"];
        cout << itNr;
        if (!fs.isOpened())
        {
            cerr << "Failed to open " << filename << endl;

            return 1;
        }

        // Read string sequence - Get node
        cv::StorageNode n = fs["strings"];
        if (n.type() != cv::StorageNode::SEQ)
        {
            cerr << "strings is not a sequence! FAIL" << endl;
            return 1;
        }

        // Go through the node
        NodeIterator it = n.begin(), it_end = n.end();
        for (; it != it_end; ++it)
            cout << (string)*it << endl;

        // Read mappings from a sequence
        n = fs["Mapping"];
        cout << "Two  " << (int)(n["Two"]) << "; ";
        cout << "One  " << (int)(n["One"]) << endl << endl;


        MyData m;
        Mat R, T;

        // Read cv::Mat
        fs["R"] >> R;
        fs["T"] >> T;
        // Read your own structure_
        fs["MyData"] >> m;

        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;
}

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Copyright (c) 2016 Andrés Solís Montero <http://www.solism.ca>, All rights reserved.


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