drawMarker(img, Point(20, 100), Scalar(0, 255, 0), MARKER_CROSS, 5);
//marker的几种形状 MARKER_CROSS = 0, //!< A crosshair marker shape MARKER_TILTED_CROSS = 1, //!< A 45 degree tilted crosshair marker shape MARKER_STAR = 2, //!< A star marker shape, combination of cross and tilted cross MARKER_DIAMOND = 3, //!< A diamond marker shape MARKER_SQUARE = 4, //!< A square marker shape MARKER_TRIANGLE_UP = 5, //!< An upwards pointing triangle marker shape MARKER_TRIANGLE_DOWN = 6 //!< A downwards pointing triangle marker shape
