Question

So, I am writing some OpenCV C++ code and I am having trouble porting my code from OpenCV 2.2 to 2.3.1. The main problem right now is the Mat::copyTo function. In the documentation or the release notes, they have mentioned that while the new version of this function takes OutputArray, the old code should still work (i.e., Mat::copyTo(Mat &m)). The thing is that it does not work.

Here’s my code

void copyMatRows(Mat &src,Mat &dest,int start_pos)
{
    for(int i=0; i < src.rows;i++)
    {
        int dest_y = start_pos;

        if(start_pos < 1)
        {
            dest_y = dest_y+i;
        }
        src.row(i).copyTo(dest.row(dest_y));

    }
}

So in the above code the line

src.row(i).copyTo(dest.row(dest_y));

fails with the error

no matching function for call to cv::Mat::copyTo(cv::Mat) candidates
are: void cv::Mat::copyTo(const cv::_OutputArray&) const

Any help would be appreciated? any way in which i can fix this?

What I am trying to do is to get N number of matrices and combine them all in one big matrix.

Answer 1

This should fix your function, but I’m not sure it’s doing exactly what you want:

void copyMatRows(Mat &src, Mat &dest, int start_pos)
{
    for(int i = 0; i < src.rows; i++)
    {
        int dest_y = start_pos;

        if(start_pos < 1)
        {
            dest_y = dest_y + i;
        }

        Mat destRow = dest.row(dest_y);
        src.row(i).copyTo(destRow);
    }
}

EDIT :
This should do pretty much what you’re looking for:

void appendMatRows(Mat &src, Mat &dst, int start_pos)
{
    for(int i = start_pos; i < src.rows; i++)
    {
        dst.push_back(src.row(i));
    }
}

The main caveat with the push_back member function is that the number of columns must be the same, but I don’t think you’re too worried about that.

Hope that helps!