How to determine if a cv::Mat is a zero matrix?

Question

I have a matrix that is dynamically being changed according to the following code;

 for( It=all_frames.begin(); It != all_frames.end(); ++It)
{
    ItTemp = *It;

    subtract(ItTemp, Base, NewData);

    cout << "The size of the new data for ";
    cout << " is \n" << NewData.rows << "x" << NewData.cols << endl;
    cout << "The New Data is: \n" << NewData << endl << endl;

    NewData_Vector.push_back(NewData.clone());

}

What I want to do is determine the frames at which the cv::Mat NewData is a zero matrix. I've tried comparing it to a zero matrix that is of the same size, using both the cv::compare() function and simple operators (i.e NewData == NoData), but I can't even compile the program.

Is there a simple way of determining when a cv::Mat is populated by zeroes?

Answer 1

I used

if (countNonZero(NewData) < 1) 
{
    cout << "Eye contact occurs in this frame" << endl;
}

This is a pretty simple (if perhaps not the most elegant) way of doing it.