In embedded systems, you often want your application to be fullscreen and hide the Linux GUI and menu. OpenCV offers an easy method to set the fullscreen window property, but make sure you created the window using the NORMAL flag:
// Create a fullscreen GUI window for display on the screen.
namedWindow(windowName, WINDOW_NORMAL);
setWindowProperty(windowName, PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);