Reading and displaying matrix from xml file with openCV

Question

I'm trying to read and display a matrix from within an xml file, using openCV. The XML file looks like this:

  <?xml version="1.0"?>
    <opencv_storage>
    <frame_00000>
      <pose type_id="opencv-matrix">
        <rows>0</rows>
        <cols>0</cols>
        <dt>u</dt>
        <data></data></pose>
      <expertCode>3</expertCode>
      <autoCode>-1</autoCode></frame_00000>
    <frame_00001>
      <pose type_id="opencv-matrix">
        <rows>0</rows>
        <cols>0</cols>
        <dt>u</dt>
        <data></data></pose>
      <expertCode>0</expertCode>
      <autoCode>-1</autoCode></frame_00001>
    <frame_00002>
      <pose type_id="opencv-matrix">
        <rows>6</rows>
        <cols>1</cols>
        <dt>d</dt>
        <data>
          9.6603986167822176e-02 2.7534827334102827e-02
          -7.9839974858475181e-03 2.9772357539313782e+02
          2.6446663460538508e+02 1.5645098067258549e+00</data></pose>
      <expertCode>0</expertCode>
      <autoCode>0</autoCode></frame_00002>
etc...

I have managed to open the file, but I can't get it to print the frame data when it is compiled and run. This is the code I have:

#include "opencv2/opencv.hpp"
#include <fstream>

using namespace cv;
using namespace std;

int main()
{
    std::cout<< endl << "Reading:" << endl;
    FileStorage fs;
    fs.open("output.xml", FileStorage::READ);

    if (fs.isOpened()) 
    {
        cout<<"File is opened\n";
    }


    Mat pose2;
    fs["pose"] >> pose2;
    std::cout<< pose2;

    fs.release();
    return (0);
}

The problem is with the last block of code before fs.release(). No matter what I try, it doesn't display the data.

I want it to display all the frame data from the xml file. I've been using the OpenCV tutorials and reference manual as a guide, but it's just not helping.

Any pointers would be appreciated, even if it's just a basic outline of the commands I should be using.

No, it was generated by a piece of facetracking software written by someone else. — JM92, Dec 13 '12 at 05:48
Maybe I'm wrong, but the way this is formatted, I don't think you can read it with OpenCV's inbuilt functions. You could use a simple XML parser to do the job. Check out [this question](http://stackoverflow.com/questions/170686/best-open-xml-parser-for-c?lq=1) for recommendations. — Sassa, Dec 13 '12 at 16:40

score 2 · Accepted Answer · answered Dec 13 '12 at 22:54

2

 FileNode n = fs.root();
    for (FileNodeIterator current = n.begin(); current != n.end(); current++) {
        FileNode item = *current;
        Mat v;
        item["pose"] >> v;
        cout << v << endl;
    }

This works! :)

answered Dec 13 '12 at 22:54

JM92

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Reading and displaying matrix from xml file with openCV

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