Thank you Keijo it worked!

@topi Hello Topi,
Thank you very much for the response!
That is a very good reason why you can not pass directly other data types to tool output.
So how to correctly copy this cv::Mat allocated by OpenCV function data to kuvio_image_alloc_copy(const kuvio_image* source) because it expects kuvio_image data type

Hello dear Sir,

I'm new user with software and I wanted to make my own tool that could read images from my file system. Is there a way that can be done?
I tried to use OpenCV imread function:
kuvio_string src = "_DSC4969.JPG";
cv::Mat mat = cv::imread(src, 0);
But I'm assuming that OpenCvMat function it wraps kuvio images and matrices to OpenCV data type, but not otherway around, so in the above case even though it compiles, but I can not convert it to kuvio image data type. Maybe there is similar function to OpenCV imread() that could read directly to kuvio image data types.
Very best regards