Thank you Brandon for following up so quickly and so thoroughly.
I did see the 4-points transform, which is why I kinda 'deep down in the cockles of my heart' knew that the functionality must be there somewhere and that there is a hole in my knowledge 🙂
I also did see setWarpTransformMatrix3x3 in the API and my thought was that it would/might/should do what I needed, based on my limited understanding of the algorithms doing the actual work behind the OpenCV fisheye functions that I currently use, but as I was at the limits of my knowledge I wanted to check before I invested serious learning time into an approach that might actually be a dead-end.
This is critically important to me, and so armed with the knowledge that there is a path there for me to pursue, I will follow it as best I can.
If you are able to get the output to 4K, this would be fantastic (I am already doing 1080 with the RPi4 and it really needs to be higher. I was on the verge of trying to solve this by trying to get 2K by stitching two frames or such)
To be honest, this will be challenging for me. I will appreciate anything that reduces the slope of my curve.
I will start on this today, though will disappear down a hole for a few days (hopefully!) while I work to get my head around it properly. I will re-emerge with either results, questions, or both I expect. When I do, would your Discord server be the more appropriate forum for this communication?
Thank you again. I very much appreaciate how good your support is. I am sure you guys must be very busy.