area_center_xldarea_center_xldAreaCenterXldAreaCenterXld (Operator)


area_center_xldarea_center_xldAreaCenterXldAreaCenterXld — Area and center of gravity (centroid) of contours and polygons.


area_center_xld(XLD : : : Area, Row, Column, PointOrder)

Herror area_center_xld(const Hobject XLD, double* Area, double* Row, double* Column, char* PointOrder)

Herror T_area_center_xld(const Hobject XLD, Htuple* Area, Htuple* Row, Htuple* Column, Htuple* PointOrder)

void AreaCenterXld(const HObject& XLD, HTuple* Area, HTuple* Row, HTuple* Column, HTuple* PointOrder)

HTuple HXLD::AreaCenterXld(HTuple* Row, HTuple* Column, HTuple* PointOrder) const

double HXLD::AreaCenterXld(double* Row, double* Column, HString* PointOrder) const

static void HOperatorSet.AreaCenterXld(HObject XLD, out HTuple area, out HTuple row, out HTuple column, out HTuple pointOrder)

HTuple HXLD.AreaCenterXld(out HTuple row, out HTuple column, out HTuple pointOrder)

double HXLD.AreaCenterXld(out double row, out double column, out string pointOrder)


area_center_xldarea_center_xldAreaCenterXldAreaCenterXldAreaCenterXld calculates the area and center of gravity (centroid) of the regions enclosed by the contours or polygons XLDXLDXLDXLDXLD as well as the order of the points along the boundary. The area and centroid are computed by applying Green's theorem using only the points on the contour or polygon, i.e., no region is generated explicitly for the purpose of calculating the features. If the points are arranged counterclockwise (i.e., in a positive mathematical sense) in the contour or polygon, PointOrderPointOrderPointOrderPointOrderpointOrder will be 'positive'"positive""positive""positive""positive". It is assumed that the contours or polygons are closed. If this is not the case area_center_xldarea_center_xldAreaCenterXldAreaCenterXldAreaCenterXld will artificially close the contour respectively polygon.

It should be noted that area_center_xldarea_center_xldAreaCenterXldAreaCenterXldAreaCenterXld only returns useful results if the contour or polygon encloses a region in the plane. In particular, the contour or polygon must not intersect itself. This is particularly important if open contours or polygons are passed because they are closed automatically, which can produce a self-intersection. To test whether the contours or polygons intersect themselves, test_self_intersection_xldtest_self_intersection_xldTestSelfIntersectionXldTestSelfIntersectionXldTestSelfIntersectionXld can be used. If the contour or polygon intersects itself, a useful value for the center of gravity can be calculated with area_center_points_xldarea_center_points_xldAreaCenterPointsXldAreaCenterPointsXldAreaCenterPointsXld.

If more than one contour or polygon is passed, the results are stored in tuples in the same order as the respective contours or polygons in XLDXLDXLDXLDXLD.

Execution Information


XLDXLDXLDXLDXLD (input_object)  xld(-array) objectHXLDHXLDHobject

Contours or polygons to be examined.

AreaAreaAreaAreaarea (output_control)  real(-array) HTupleHTupleHtuple (real) (double) (double) (double)

Area enclosed by the contour or polygon.

RowRowRowRowrow (output_control)  point.y(-array) HTupleHTupleHtuple (real) (double) (double) (double)

Row coordinate of the centroid.

ColumnColumnColumnColumncolumn (output_control)  point.x(-array) HTupleHTupleHtuple (real) (double) (double) (double)

Column coordinate of the centroid.

PointOrderPointOrderPointOrderPointOrderpointOrder (output_control)  string(-array) HTupleHTupleHtuple (string) (string) (HString) (char*)

point order along the boundary ('positive'/'negative').


Let n be the number of points of the contour or polygon. Then the run time is O(n).


area_center_xldarea_center_xldAreaCenterXldAreaCenterXldAreaCenterXld returns 2 (H_MSG_TRUE) if the input is not empty. If the input is empty the behavior can be set via set_system(::'no_object_result',<Result>:)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>). If necessary, an exception is raised.

Possible Predecessors

gen_contours_skeleton_xldgen_contours_skeleton_xldGenContoursSkeletonXldGenContoursSkeletonXldGenContoursSkeletonXld, smooth_contours_xldsmooth_contours_xldSmoothContoursXldSmoothContoursXldSmoothContoursXld, gen_polygons_xldgen_polygons_xldGenPolygonsXldGenPolygonsXldGenPolygonsXld



See also

moments_xldmoments_xldMomentsXldMomentsXldMomentsXld, moments_any_xldmoments_any_xldMomentsAnyXldMomentsAnyXldMomentsAnyXld, area_centerarea_centerAreaCenterAreaCenterAreaCenter, moments_region_2ndmoments_region_2ndMomentsRegion2ndMomentsRegion2ndMomentsRegion2nd