Shape factor for the circularity (similarity to a circle) of contours or polygons.
The operator circularity_xld calculates the similarity of each input contour or polygon with a circle. The input contour or polygon must not intersect itself, otherwise the resulting parameter is not meaningful (Whether the input contour or polygon intersects itself or not can be determined with test_self_intersection_xld). If the input contour or polygon is not closed it will be closed automatically.
Calculation:
If F is the area enclosed by the contour or polygon and max is the
maximum distance from the center to all contour or polygon pixels, the shape
factor
Circularity is defined as:
Circularity = F / (max^2 * pi)
The shape factor Circularity of a circle is 1. If the contour
or polygon encloses an elongated area Circularity is smaller than 1.
The operator circularity_xld especially responds to large bulges.
If more than one contour or polygon is passed, the numerical values of the shape factor are stored in a tuple in the same order as the respective contours or polygons in XLD.
|
XLD (input_object) |
xld(-array) -> object |
| Contours or polygons to be examined. | |
|
Circularity (output_control) |
real(-array) -> real |
| Roundness of the input contours or polygons. | |
| Assertion: (0 <= Circularity) && (Circularity <= 1.0) | |
The operator circularity_xld returns the value 2 (H_MSG_TRUE) if the input is not empty. The behavior in case of empty input (no input contour available) is set via the operator set_system('no_object_result',<Result>). If necessary an exception is raised.
circularity_xld is reentrant and automatically parallelized (on tuple level).
gen_contours_skeleton_xld, edges_sub_pix, threshold_sub_pix, gen_contour_polygon_xld, test_self_intersection_xld
compactness_xld, convexity_xld, eccentricity_xld
area_center_xld, select_shape_xld
Foundation