How to find the color of a pixel in an OpenGL ES/NDK screen?

Question

Android

Hello!
Given: TV box Eltex NV 501 wac, Android 4.4.4, towelroot (before reboot).
I'm trying to make a backlight for TV + Android set-top box - a la Ambilight / Kodi + Boblight, but without xbmc, etc.
I want to quickly (from 5 frames / sec) get the color of a pixel at the given coordinates.
I searched the internet and narrowed it down to:

1. OpenGL ES - there is a method glReadPixel. This option seems to me the most successful, but I'm not familiar with OpenGL. Could not understand whether opengl can read from the "system" buffer frame? Those. open /dev/graphics/fb0 and get the desired pixel.
   
2. Adnroid NDK + /dev/framebuffer - read from the buffer, get the desired pixel. I'm afraid that it will take a long time to read the buffer (10Mb) + parse.
   
3. screencap/minicap/ffmpeg - in principle, you can use the application to take screenshots, but I'm afraid it will be slow or take a lot of resources.
   

Question: Can opengl do what I need?
Which of the proposed options is easier to implement, but at the expense of speed?
If you offer a better one I will be very grateful! Thanks in advance!