New feature: circularity

[lidakanari]

This feature needs to be implemented on the 2D projection of a morphology and it will describe the circularity in the projected plane i.e. x-y. We will therefore need to compute this in all three projections at the morphology level.

Circularity is defined as 4 * pi * area / (perimeter)^2

def circularity(pts):
    """Computes circularity as 4 pi A / P^2"""
    hull = nm.geom.ConvexHull(pts)
    area = hull.volume
    perimeter = hull.area
    return (4 * np.pi * area) / (perimeter * perimeter)

[lidakanari]

For the same dataset:
TestData.zip

The expected circularity is:

circularity(circle) == 0.9878344238311306
circularity(square) == 0.8166489559832344
circularity(rectangle) == 0.6109332086629591
circularity(oval) == 0.8102300985964894