OpenCV FileStorage empty after loading - opencv

Question

Im trying to load a string into filestorage. I will not have the file to pass filename as a parameter to load it. Instead I recive an xml document as a string. In the doc http://docs.opencv.org/modules/core/doc/xml_yaml_persistence.html#filestorage it is mentioned that source attribute of fs.open can be "text string to read the data from". I run some simple tests with OpenCv CascadeClassifier as a string but I get an empty FileStorage. What am I doing wrong?
CascadeClassifier face_cascade;
std::ifstream t("haarcascade_frontalface_alt.xml");
std::string ClasifierInString((std::istreambuf_iterator<char>(t)),
std::istreambuf_iterator<char>());
cout << ClasifierInString << endl; //I CAN PRINT THE FILE AND SEE IT
cv::FileStorage fs;
if (!fs.open(ClasifierInString, cv::FileStorage::READ | cv::FileStorage::MEMORY | cv::FileStorage::FORMAT_XML))
{
cout << "Couldn't load file into memory" << endl;
return -2;
}
FileNodeIterator it = fs.getFirstTopLevelNode().begin(), it_end = fs.getFirstTopLevelNode().end();
for (; it != it_end; ++it)
{
cout << (string)*it << "\n"; //EMPTY LINE????
}
if (!face_cascade.read(fs.getFirstTopLevelNode()))
{
cout << "Couldn't read file from memory" << endl;
return -1;
}
EDIT:
#sop can't comment yet. Maybe your using older version of OpenCV. I have the file and I am able to load it with:
face_cascade.load("haarcascade_frontalface_alt.xml");
and it works. The problem is I'm unable to read it as a string with face_cascade.read(string)

Answer 1

#berak comment is the correct answer. I used lbpcascade_frontalface.xml as this is new cascade (and is faster! :) Thx for help.

Answer 2

I think your problem is the file name: "haarcascade_frontalface_alt.xml". There is no such a file in the OpenCV flder... Try "haarcascade_frontalface_alt_tree.xml".
Here is my code that works:
cv::CascadeClassifier face_cascade;
std::ifstream t("haarcascade_frontalface_alt_tree.xml");
std::string ClasifierInString((std::istreambuf_iterator<char>(t)), std::istreambuf_iterator<char>());
std::cout << ClasifierInString << std::endl; //I CAN PRINT THE FILE AND SEE IT
cv::FileStorage fs;
if (!fs.open(ClasifierInString, /*cv::FileStorage::READ | */cv::FileStorage::MEMORY | cv::FileStorage::FORMAT_XML))
{
std::cout << "Couldn't load file into memory" << std::endl;
return -2;
}
cv::FileNodeIterator it = fs.getFirstTopLevelNode().begin(), it_end = fs.getFirstTopLevelNode().end();
for (; it != it_end; ++it)
{
std::cout << (std::string)*it << "\n"; //EMPTY LINE????
}
if (!face_cascade.read(fs.getFirstTopLevelNode()))
{
std::cout << "Couldn't read file from memory" << std::endl;
return -1;
}