On one hand it is simpler on GLES, because it allows direct readback, and on the other hand it fixes failures when EXT_texture_buffer is not available.
Also unbind the buffers after use because otherwise glReadPixel would interpret the pixel pointer argument as offset into the pixel buffer and would fail.
Closes: #45 (closed)
Signed-off-by: Gert Wollny gert.wollny@collabora.com