error: invalid initialization of non-const reference of type 'cv::Mat&'

Question

The below is my function prototype.

void devectorize(Mat &vec,Mat mask,Mat& img);

I am getting the below error when I try to call this function in my code. What would be the reason?

Mat V;

for(int i=0;i<V.cols;i++)
{
  devectorize(V.col(i),mask,E_img); //Error in this line
}

error: invalid initialization of non-const reference of type 'cv::Mat&' from an rvalue of type 'cv::Mat'
utils.h:11:6: error: in passing argument 1 of 'void devectorize(cv::Mat&, cv::Mat, cv::Mat&)'

http://eli.thegreenplace.net/2011/12/15/understanding-lvalues-and-rvalues-in-c-and-c/ — BartoszKP, Aug 31 '13 at 13:12

score 4 · Accepted Answer · edited Aug 31 '13 at 13:14

4

You cannot bind a non-const reference to a temporary. In your case the first argument to devectorize is a non-const reference and the return value from V.col(i) is the temporary. This code would work

for (int i = 0; i < V.cols; i++)
{
    Mat tmp = V.col(i);
    devectorize(tmp, mask, E_img);
}

so would changing the first parameter of devectorize to const Mat&.

edited Aug 31 '13 at 13:14

Vaughn Cato

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answered Aug 31 '13 at 13:11

john

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You saved my hours. Thank you sir, I owe you one. Great day. I also thank @user2727765 for the question – aliyasineser Oct 18 '18 at 13:10

error: invalid initialization of non-const reference of type 'cv::Mat&'

1 Answers1