It's not X11 dependent; it's a standard part of the OpenGL ES API. It is however generally slow. It is worth nothing that for most hardware-based graphics almost any form of readback is slow, so this issue is not unique to read pixels. For "typical use" the CPU never touches the rendered image; it is rendered, composited with other windows, and displayed on screen all using different hardware blocks. Most graphics architectures exploit this fact to improve efficiency, but in consequence forcing things back on the CPU can cause stalls in the processing pipeline. Reading back from /dev/fb0 may be faster, as far as you can bypass the graphics pipeline issues, but you have to sync up what in in the framebuffer with a specific application frame (and hope it isn't overwritten by the _next_ frame - remember the hardware rendering is asynchronous to the application calls). HTH,Iso