Best to ask the developer as it is an add-on hasn’t received any updates for 2 years. About the error.
The add-on might have been built on a different version of the cv2 library that you have installed.
Thank you very much for the response @JeroenBakker !
Unfortunately, the developer did no respond. When you say add-on, do you mean the blender version?
And, yes you are right about the “The add-on might have been built on a different version of the cv2 library that you have installed.”
I get the following warning and error as well:
libpng warning: Application was compiled with png.h from libpng-1.5.13
libpng warning: Application is running with png.c from libpng-1.2.50
libpng error: Incompatible libpng version in application and library
Does it mean that I I have to install the same opencv version that the developer used? In fact, I installed the version recommended by developer in requirements.txt
It is not only installing the same version but making sure that any library that is being used is also available on your machine. You have installed libpng1.5.13, but the requirements.txt uses some library that requires libpng1.2.50 (or compatible).