C ++: how to create a dynamic template type

Question

I have the following code snippet that I created to change the pixel intensity in an OpenCV image (Cv :: Mat class).

As you can see, I do the loop in both cases, but with a different type of pattern.

The transfer function may be overloaded.

So my question is how can I create a dynamic type of template to make it look better.

Mat mat = _mat.clone() ;
int channels = mat.channels();

switch(channels)
{
case 1: 
    for (int i=0; i<mat.rows; i++)
    {
        for (int j=0; j<mat.cols; j++)
        {
            uchar src = mat.at<uchar>(i,j);
            uchar dst = mat.at<uchar>(i,j);

            t.transfer(src, dst);
        }
    }
    break;

case 3: 
    for (int i=0; i<mat.rows; i++)
    {
        for (int j=0; j<mat.cols; j++)
        {
            Vec3b src = mat.at<Vec3b>(i,j);
            Vec3b dst = mat.at<Vec3b>(i,j);

            t.transfer(src, dst);
        }
    }
    break;
}

return mat ;

Answer 1

How about something like this:

template <typename U, typename T>
void transfer_mat(Mat & mat, T & t)
{
    for (int i = 0, r = mat.rows; i != r; ++j)
    {
        for (int j = 0, c = mat.cols; j != c; ++j)
        {
            U src = mat.at<U>(i, j);
            U dst = mat.at<U>(i, j);

            t.transfer(src, dst);
        }
    }
}

Then you can say:

switch(channels)
{
case 1:
    transfer_mat<uchar>(mat, t);
    break;
case 2:
    transfer_mat<Vec3b>(mat, t);
    break;
}

Answer 2

It's not clear if your code area (looks like a member function) and what type it is t, but this should start:

template<typename AtT>
Mat& transfer_impl(Mat& mat, T& t)
{
    for (int i = 0; i < mat.rows; ++i)
        for (int j = 0; j < mat.cols; ++j)
            t.transfer(mat.at<AtT>(i, j), mat.at<AtT>(i, j));
    return mat;
};

Mat transfer(Mat const& _mat, T& t)
{
    Mat mat = _mat.clone();
    switch (mat.channels())
    {
    case 1:  return transfer_impl<uchar>(mat, t);
    case 3:  return transfer_impl<Vec3b>(mat, t);
    default: throw std::runtime_error(/*...*/);
    }
}