Show multiple (2,3,4,…) images in the same window in OpenCV

Question

I want to show 2, 3 or more images in the same window.

My problem is how to put the second, third image just on the right side (above, left or upper) the main image.

Answer 1

Or just use:

Mat a, Mat b, Mat dst // a,b loaded

cv::hconcat(a, b, dst) // horizontal
cv::vconcat(a, b, dst) // vertical

Mat dst -> | a | b |

or do it with vector:

std::vector matrices = {
            a, b
    };
hconcat(matrices, dst);