compactness — Shape factor for the compactness of a region.
compactness(Regions : : : Compactness)
The operator compactness calculates the compactness of the input regions.
If L is the length of the contour (see
contlength) and F the area of the region the shape
factor C is defined as:
C = max(1,C')
In the documentation of this chapter (Regions / Features), you can find an image illustrating regions which vary in their compactness.
The shape factor C of a circle is 1. If the region
is long or has holes C is larger than 1.
The operator compactness responds to the course of the contour
(roughness) and to holes. The value of C is clipped to 1.0,
because the pixel area of a region can only be an approximation of a
real circle's area. This approximation error is bigger for small
regions than for large regions.
In case of an empty region the operator compactness returns the
value 0 if no other behavior was set (see set_system).
If more than one region is passed the numerical values of the shape
factor are stored in a tuple, the position of a value in the tuple corresponding
to the position of the region in the input tuple.
Regions (input_object) region(-array) → object
Region(s) to be examined.
Compactness (output_control) real(-array) → (real)
Compactness of the input region(s).
Assertion: Compactness >= 1.0 || Compactness == 0
The operator compactness returns the value 2 (H_MSG_TRUE)
if the input is not empty.
The behavior in case of empty input (no input regions available) is
set via the operator set_system('no_object_result',<Result>).
The behavior in case of empty region (the region is the empty set) is set via
set_system('empty_region_result',<Result>).
If necessary an exception is raised.
threshold,
regiongrowing,
connection
contlength,
area_center,
select_shape
Foundation