code: func (w *Webcam) ReadFrame() ([]byte, error) {
  	result, index, err := w.GetFrame()
  	if err == nil {
  		w.ReleaseFrame(index)
  	}
  	return result, err
  }
docs: // Read a single frame from the webcam
  // If frame cannot be read at the moment
  // function will return empty slice