convexity — Shape factor for the convexity of a region.
The operator convexity calculates the convexity of each input region of Regions.
If is the area of the convex hull and the original area of the region the shape factor C is defined as:
The shape factor C is 1 if the region is convex (e.g., rectangle, circle etc.). If there are indentations or holes C is smaller than 1.
In the documentation of this chapter (Regions / Features), you can find an image illustrating regions which vary in their convexity.
In case of an empty region the operator convexity 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 contour length are stored in a tuple, the position of a value in the tuple corresponding to the position of the region in the input tuple.
Region(s) to be examined.
Convexity of the input region(s).
Assertion: Convexity <= 1
The operator convexity 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
select_shape, area_center, shape_trans