public void open() {
        Util.validateMainThread();

        open = true;
        cameraClosed = false;

        cameraThread.incrementAndEnqueue(opener);
    }
@return the camera rotation relative to display rotation, in degrees. Typically 0 if the
   display is in landscape orientation.
zxing-android-embedded/src/com/journeyapps/barcodescanner/camera/CameraInstance.java