png - FrameBuffer to file inside libgdx or OpenGL -

i trying take screenshots in efficient way. thing using framebuffer efficient way of taking screenshots because can process data in different thread rendering thread. how can information framebuffer , transfer file?

framebuffer m_fbo;  render(){    m_fbo = new framebuffer(format.rgb565, (int)(w * m_fboscaler), (int)(h * m_fboscaler), false);    m_fboregion = new textureregion(m_fbo.getcolorbuffertexture());    m_fboregion.flip(false, true);    m_fbo.begin();    ...rendering...    m_fbo.end();    writetextureregiontofile(); - need lines of code implementation of method } 

the framebuffer contents reside in memory managed opengl, (as far understand things) still need fetch bytes using opengl apis on render thread. specifically, want the screenutils class byte[] containing rgba8888 contents of framebuffer.

once raw bytes, can compression/conversion/output on different thread, of course. there forum post has quick , dirty png writer. libgdx-specific (?) cim format option (see pixmapio class), you'll have convert bytes pixmap first.