opencv drawMarker()函数的显示图例

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