title: How can I access the raw pixel data of an opengl es 2 off screen render buffer?
body: <p>I can render to the screen but I would like to be able to access the raw pixels that have been rendered by the shader. The only way I know how is to use glReadPixels off of the screen, but I would like to access them before they are draw to screen in order to save frames to disk.</p>
  
  <p>Specifically I want to use shaders to process images that are never displayed: 1)grab image from disk 2)render it 3)output back to disk.</p>