Screenshot with wapring and blending included

Hi everyone,
i used nvidia-settings github project from NVIDIA to warp and blend my displays

and now i’m trying to take a screenshot of the warped screen, but all my tries failed.
I tried:

allo of these take a screenshot, but without wapring and blending.
I need to do this for testing the correctness of warp and blend results.
How can i do it?
Any help would be appreciated, thank you.

I’ve also opened a issue in nvidia-settings project: