Image<Gray, Byte> src = new Image<Gray, Byte>( "Your Image.png" );
Image<Gray, Byte> dst = new Image<Gray, Byte>( src.Width, src.Height );
StructuringElementEx element = new StructuringElementEx( 3, 3, 1, 1, Emgu.CV.CvEnum.CV_ELEMENT_SHAPE.CV_SHAPE_CROSS );

CvInvoke.cvMorphologyEx( src, dst, IntPtr.Zero, element, CV_MORPH_OP.CV_MOP_OPEN, 1 );

ImageViewer.Show( dst, "Your morphed Image" );

CV_MORPH_OP.CV_MOP_CLOSE