title: FrameBuffer to file inside libgdx or OpenGL
body: <p>I am trying to take screenshots in the most efficient way. I thing using a FrameBuffer is the most efficient way of taking screenshots because i can process the data in different thread than rendering thread. 
  How can i get the information from FrameBUffer and transfer it to a file?</p>
  
  <pre><code>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(); - i need some lines of code for the implementation of this method
  }
  </code></pre>