CODEWITHSUNDEEP
c++opencvmat
anti
anti

Reputation: 3125

cv::Mat use row data to fill a new Mats columns

I have a function which returns an opencv Mat, with 4 rows and 1 column. It runs in a for loop, iterating between two and 100 times.

What I need, is to copy the returned column to a new Mat, so that each iteration adds a new column.

I have (pseudo):

cv::Mat ResultMat(4, 1, CV_64F);

Mat returnMat(4, 1, CV_64F);

for (int i = 0; i < iterations; i++)
    {

returnMat= (function that returns a 4x1 Mat);

returnMat.col(0).copyTo(ResultMat.col(0));
   }

which works fine, but overwrites the Resultmat column each time.

Replacing the last line with 

returnMat.col(0).copyTo(ResultMat.col(i));

causes an exception error.

EDIT: If I create the ResultMat as 'Resultmat(4, 100, CV_64F)', it works, but I need it to self-adjust the number of columns...

How can I add columns to the ResultMat dynamically, one for each loop?

Upvotes: 1

Views: 2042

Answers (1)

ypx
ypx

Reputation: 1459

Not sure why it didn't work for you when you changed the size of ResultMat. But here's a solution, given that you know the number of iterations, which is bascially the number of columns in the end result. I defined a function func() to demonstrate the function called inside the loop.

Mat func() {

    Mat m(4, 1, CV_64F);
    randn(m, 0., 1.); // fill with random values.

    return m;
}

int main() {
    int iterations = 3;
    cv::Mat result(4, iterations, CV_64F);

    for (int i = 0; i < iterations; i++) {

        Mat m = func();
        m.col(0).copyTo(result.col(i));
    }
    return 0;
}

Upvotes: 4

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