title: Is there a fast way to the average colors from several framebuffers in WebGL / Javascript?
body: <p>I am very new to the WebGL subject.
  What I want to do is to calculate the average color of 6 different framebuffers like the ones below in the picture. Now I am wondering what the best way to go about it would be?
  I tried to do </p>
  
  <pre><code>gl.readPixels(0, 0, 256, 256, gl.RGBA, gl.UNSIGNED_BYTE, pixelValues);
  </code></pre>
  
  <p>but that seems to be very slow...
  Is there a way that this can happen on the graphics card?</p>
  
  <p><img src="https://i.stack.imgur.com/gKspR.png" alt="enter image description here"></p>
  
  <pre><code>this is how the FBO is set up - I have this from a tutorial:
  
  ...
  </code></pre>