I have developed C++ DLL by using the C wrapper that is used for various languages. At present, I can use in Python & C#. I have to find the way to read it in same in LabVIEW.
I use visual studio have installed OpenCV on c:\ added include directory and the .lib files for my project, & I have created a variable in my DLL and I use that during #include <opencv2/core/core.hpp>.