I'm working with creating a histogram overlay. I created a shader witch generates a 8x8 histogram. I would like to draw it as a tiny overlay in the corner of the screen as a realtime feature of a videostream. Everything work fine when working on screen. I render local histograms all over then picture and then reduce them with another shader and finally reads back it to the CPU memory. Then I draw an overlay and renders it back to the screen.
The problems starts when using a FBO. It works great when rendering but finally I want to read back data from the FBO to the CPU memory. In ES 2.0 specification GetTexImage(..) isn't supported and readBuffer(..) is also gone. When working online readPixels(..) works but I won't work with offScreen rendering. readPixels(..) works for off screen pBuffers but I really want to use FBO.
I'm working with the Imagination simulator. Maybe there will be some extensions?