get_unique_orientations.py

def get_unique_orientations(poly):
    """
    Out of all possible rotations and flips, take into account the polygon symmetry and
    obtain the unique polygon orientations.
    :param poly: input polygon
    :return: array of unique settings of (rotation, flip)
    """
    cx, cy = poly.centroid.x, poly.centroid.y
    pts = np.array(poly.checkers)[:, :-1]
    checkers = np.array(poly.checkers)[:, -1]
    pts = pts[checkers == 1]
    poly = poly.difference(MultiPoint(pts + 0.5).buffer(0.2))

    rots = [0, 90, 180, 270]
    flips = [1, -1]
    iterables = [rots, flips]
    settings = np.array(list(itertools.product(*iterables)))
    unique_polys = []
    unique_settings = []
    for rot, flip in settings:
        p = poly
        p = rotate(p, rot, origin=[cx, cy])
        p = scale(p, flip, origin=[cx, cy, 0])
        if np.any([p.difference(u).area < 1e-5 for u in unique_polys]):
            continue
        unique_polys.append(p)
        unique_settings.append([rot, flip])
    return unique_settings