HALCON Reference Manual 10.0.2

area_center_xldarea_center_xldarea_center_xldAreaCenterXldAreaCenterXld (Operator)

Name

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

Signature

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

area_center_xldarea_center_xldarea_center_xldAreaCenterXldAreaCenterXld 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_xldarea_center_xldAreaCenterXldAreaCenterXld will artificially close the contour respectively polygon.

It should be noted that area_center_xldarea_center_xldarea_center_xldAreaCenterXldAreaCenterXld 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_xldtest_self_intersection_xldTestSelfIntersectionXldTestSelfIntersectionXld 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_xldarea_center_points_xldAreaCenterPointsXldAreaCenterPointsXld.

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.