How to compare two Mats columns in OpenCV

Question

i wonder how can we compare columns of two mats

here is what am doing

 cv::Mat M(2,2, CV_8UC3, cv::Scalar(0,0,255));
 cv::Mat M2(2,2, CV_8UC3, cv::Scalar(0,0,255));

 for(int c = 0; c < M.cols; c++ ){
     if( M.col(c) == M2.col(0) ){   // error

     }

 }

am getting error

error: no viable conversion from 'cv::MatExpr' to 'bool'

so how to compare columns as i have to stich two images for which i need to do comparison column wise , so that when i attach 2nd image with 1st image , i want to make sure that i attach it position where last column of 1st image is equal to somewhere in 2nd image so that duplicate portion is eliminated.

Answer 1

You can check if two matrix are identical as explained here.

You can pass the columns instead of the whole matrix:

bool are_equal(const cv::Mat& a, const cv::Mat& b)
{
    return (cv::sum(a != b) == cv::Scalar(0, 0, 0, 0));
}


int main()
{
    cv::Mat3b a(3, 3);
    cv::Mat3b b(3, 3);

    cv::randu(a, 0, 9);
    cv::randu(b, 0, 9);

    bool same_columns = are_equal(a.col(1), b.col(2));      
}