Bio-inspired features returns NaNs

edit

Hello,

I am using bif function (bif.cpp) from the extra module 'face' of Opencv-3.0.1. When I run the function for a test image, the returned feature vector includes many NaN values. Could you please help me understand why this is happening?

#include "opencv2/opencv.hpp"
#include "opencv2/face/bif.hpp"
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char** argv) {

    cv::Mat fea;
    cv::Ptr<cv::face::BIF> bif = cv::face::createBIF();
    cv::Mat image(60, 60, CV_32F);
    cv::theRNG().fill(image, cv::RNG::UNIFORM, 0, 1);
    bif->compute(image, fea);
    cout << "fea = " << endl << " " << fea << endl << endl;

    return 0;
}

Thank you in advance.

EDIT: Sorry for my delayed edit, but please let me ask something more. I have made the changes you suggested and for most of the images the NaN value disappeared. However, the problem for some images is not fixed. I am giving an example below. Could you please provide some extra help on this?

EDIT Possible answer: The code of bif.cpp seems to implement correctly the algorithm presented in the corresponding paper, so the problem of negative values in sqrt is not algorithmic. By debugging the code, I noticed that the negative values were very small, having order of magnitude 10^-17 and 10^-19 for the specific example image and values of order 10^-17 to 10^-21 for other images. According to this post, these very small negative numbers are smaller than the numeric limit for double values and can be casted to 0. Therefore, I suggest that the line 210 can be:

 sd = sqrt((sd / area - mean  mean) < 0 & abs((sd / area - mean  mean)) < std::numeric_limits<double>::epsilon() ? 0 : (sd / area - mean * mean));

If (sd / area - mean mean) is positive, nothing changes. If (sd / area - mean mean) is negative and smaller than the numeric limit for doubles, it is set to 0. By changing line of code 210 as above, no NaN values emerge.