bounds.py 文件源码

def oriented_bounds_2D(points):
    '''
    Find an oriented bounding box for a set of 2D points.

    Arguments
    ----------
    points: (n,2) float, 2D points

    Returns
    ----------
    transform: (3,3) float, homogenous 2D transformation matrix to move the input set of 
               points to the FIRST QUADRANT, so no value is negative. 
    rectangle: (2,) float, size of extents once input points are transformed by transform
    '''
    c = ConvexHull(np.asanyarray(points))
    # (n,2,3) line segments
    hull = c.points[c.simplices] 
    # (3,n) points on the hull to check against
    dot_test = c.points[c.vertices].reshape((-1,2)).T
    edge_vectors = unitize(np.diff(hull, axis=1).reshape((-1,2)))
    perp_vectors = np.fliplr(edge_vectors) * [-1.0,1.0]
    bounds = np.zeros((len(edge_vectors), 4))
    for i, edge, perp in zip(range(len(edge_vectors)),
                             edge_vectors, 
                             perp_vectors):
        x = np.dot(edge, dot_test)
        y = np.dot(perp, dot_test)
        bounds[i] = [x.min(), y.min(), x.max(), y.max()]

    extents  = np.diff(bounds.reshape((-1,2,2)), axis=1).reshape((-1,2))
    area     = np.product(extents, axis=1)
    area_min = area.argmin()

    offset = -bounds[area_min][0:2]
    theta  = np.arctan2(*edge_vectors[area_min][::-1])

    transform = transformation_2D(offset, theta)
    rectangle = extents[area_min]

    return transform, rectangle