OpenCV indexing through Mat of unknown type

Question

I would like to access the elements of a matrix of unknown type:

for(int ii = 0; ii < origCols; ii++)
{
  colIdx.at(0,ii) = ii+1; // mak         


        

Answer 1

After looking through some of the docs, I don't think there is a native OpenCV way to do it without avoiding branching.

If you are just concerned about cleaner code, you could try a template approach so long as you don't mind templates:

template  void dostuff(cv::Mat& colIdx, int origCols)
{
   for(int ii = 0; ii < origCols; ii++)
   {
       colIdx.at(0,ii) = (T)(ii+1); // make one based index
   }
}

void dostuff_poly(cv::Mat& colIdx, int origCols)
{
    switch(colIdx.type())
    {
        case CV_8UC1: dostuff(colIdx, origCols); break;
        case CV_32FC1: dostuff(colIdx, origCols); break;
        case CV_64FC1: dostuff(colIdx, origCols); break;
        // and so on
        default:
    }
}

In this example, the code is rather small, so templates seems like it wouldn't be a bad choice and would give you the polymorphism you want without writing a bunch of redundant code.

Maybe some of these tutorials would give you a better idea:

OpenCV docs: core module tutorials

OpenCV docs: How to scan images