main/src/georegression/geometry/UtilPolygons2D_F64.java
public static Point2D_F64 center( Quadrilateral_F64 quad , Point2D_F64 center ) {
		if( center == null )
			center = new Point2D_F64();

		center.x = quad.a.x + quad.b.x + quad.c.x + quad.d.x;
		center.y = quad.a.y + quad.b.y + quad.c.y + quad.d.y;

		center.x /= 4.0;
		center.y /= 4.0;

		return center;
	}
public static Point2D_F64 center( Quadrilateral_F64 quad , Point2D_F64 center ) {
		if( center == null )
			center = new Point2D_F64();

		center.x = quad.a.x + quad.b.x + quad.c.x + quad.d.x;
		center.y = quad.a.y + quad.b.y + quad.c.y + quad.d.y;

		center.x /= 4.0;
		center.y /= 4.0;

		return center;
	}
Computes the center or average point in the quadrilateral.

@param quad (Input) Quadrilateral
@param center (output) Center point of the quadrilateral.  Can be null.
@return The center point.