How to use GLES3 in iOS

Hi, Evryone.

I want to use GLES3’s GL_ATOMIC_COUNTER_BUFFER in IOS.
Is there a good way to install gles3?

I’m making a drawing application for IOS.
I’m trying to create a function to display the area of the drawn color accurately in real time.
I plan to use GL_ATOMIC_COUNTER_BUFFER to count the number of pixels for each color.

If you know how to install gles3 or a good way to count the pixels, please advise me.

Thanks.