elliptic_axis_points_xld — Parameters of the equivalent ellipse of contours or polygons treated as
elliptic_axis_points_xld calculates the radii
Rb) and the orientation (
Phi, in radians)
of the ellipse
having the same orientation and the same aspect ratio as the point cloud
given by the contour or polygon
XLD (i.e., the order of the points in the contour or
polygon is not taken into account). 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.
If the moments , and
are normalized to the area (see
the major radius
Ra and the minor radius
Rb are calculated
Phi, i.e., the angle between the major axis
and the x (column) axis, is defined by:
elliptic_axis_points_xld should be used if the contour
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
elliptic_axis_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
Contours or polygons to be examined.
Ra >= 0.0
Rb >= 0.0 && Rb <= Ra
Angle between the major axis and the column axis (radians).
- pi / 2 < Phi && Phi <= pi / 2
Let n be the number of points of the contour or polygon. Then the run time is O(n).
elliptic_axis_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.
R. Haralick, L. Shapiro “Computer and Robot Vision” Addison-Wesley, 1992, pp. 73-75