Are there ready implementations of Gaussian Blur opengl?

Question

C++ / C#

We need a blurred window background near the program interface (example in the picture)

. that's actually all, then I'm not ready to climb into the hell of the openGL language yet and still hope to get off with a little blood, there will even be enough example that takes a texture and applies shaders to it, somehow I'll screw the Blur shaders
Application with # WPF, but it will do something in c++ (I’ll just format it as a lib and screw it to c#)
I’ve already tested the standard C# tools for blurring - it slows down

Answer 1

I have already tested the standard C# tools for blurring - it slows down

You are doing something wrong.
c# wpf shader effect
There is even in Russian https://habrahabr.ru/post/194734/ (though not Gauss, but I think you can tweak it for yourself)

Answer 2

Is it really hard to google it? straight the second line either