area_center_points_xld🔗
Short description🔗
area_center_points_xld — Area and center of gravity (centroid) of contours and polygons
treated as point clouds.
Signature🔗
area_center_points_xld( xld XLD, out real Area, out point.y Row, out point.x Column )
Description🔗
area_center_points_xld calculates the area and center of
gravity (centroid) of the point clouds given by contours or polygons
XLD (i.e., the order of the points in the contour or
polygon is not taken into account). The area corresponds to the
number of points in the point cloud. The centroid is given by the
arithmetic mean of all points. If the contour or polygon is closed
(end point = start point), the end point of the contour or polygon is
not taken into account to avoid that it receives twice the weight of
the other points.
area_center_points_xld should be used if the contour XLD
intersects itself or if it is not possible to close the contour using a line
from end to start point without self-intersection, because in this case
area_center_xld does not produce useful results. To test whether the
contours or polygons intersect themselves,
test_self_intersection_xld can be used.
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
XLD.
Attention🔗
Even if the contour or polygon XLD is not intersecting itself, the
result of area_center_points_xld significantly differs from the
result of area_center_xld as it is calculated from the point cloud
and not from the enclosed region.
Execution information🔗
Execution information
-
Multithreading type: reentrant (runs in parallel with non-exclusive operators).
-
Multithreading scope: global (may be called from any thread).
-
Automatically parallelized on tuple level.
Parameters🔗
XLD (input_object) xld(-array) → object
Point clouds to be examined in form of contours or polygons.
Area (output_control) real(-array) → (real)
Area of the point cloud.
Row (output_control) point.y(-array) → (real)
Row coordinate of the centroid.
Column (output_control) point.x(-array) → (real)
Column coordinate of the centroid.
Complexity🔗
Let n be the number of points of the contour or polygon. Then the run time is O(n).
Result🔗
area_center_points_xld 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>:). If necessary,
an exception is raised.
Combinations with other operators🔗
Combinations
Possible predecessors
gen_contours_skeleton_xld, smooth_contours_xld, gen_polygons_xld
Alternatives
See also
moments_points_xld, moments_any_points_xld, area_center, moments_region_2nd
Module🔗
Foundation