OpenGL to draw an image, then analyze it, both by GPU

I need fast parallel computation of image pixel values,which is previously rendered by OpenGL (or other graphics library) APIs.
I use MS Visual Studio C++ and I want my NVIDIA processor to do both, to maximize efficiency by directly sharing the image buffer.
Could someone guide me which APIs/tools I should choose? There are cuda, opencl, vulkan, … in which I have no experience at all.