Hi and welcome to devnet,

To add to @koahnig , your application is probably not finding the OpenCV dlls. You would need to update the PATH variable in the Run part of the Project panel.

Hi,

If my cv::Mat variable is a 2 dimension matrix of a small size (<10*10）, is it possible to show its elements in "locals and expressions" window? Is it easy or lots of work needed? Or there has already been some tools?

Thanks a lot.
Yanming

Could you send us the minimum projects which could reproduce the bugs(.hpp, .cpp and your .pro), if you could put it on github, it would be even better(easier for us to download and test it)
I have a long time haven't played with openCV2, but I do have some experience about it

By the way, since you are using Qt, why not just use QLabel or graphicsview framework to show the image?If you need to convert the QImage and cv::Mat, you could look at here.