shapes.py 文件源码

def factor_polygon_into_circles(polygon, radius_km):
    """
    Takes a GEOSGeomtery Polygon and a radius in kilometers. Returns a list
    of (lng, lat) tuples representing the centers of circles of the specified
    radius that together cover the area of the Polygon.
    """
    safety_buffer = 0.01  # small safety buffer for overlap

    if not isinstance(polygon, Polygon):
        raise TypeError('object is not a Polygon')

    if radius_km <= safety_buffer:
        raise ValueError('radius must be greater than safety buffer')

    # get the bounds of the polygon with a small safety buffer
    buffer_dist_m = (radius_km * 1000) * safety_buffer
    bounds = create_buffered_bounds(polygon, buffer_dist_m)

    # get the space between circle centers, with a safety margin of 10 meters
    dist_bw_centers_m = calculate_circle_spacing(radius_km * 1000, overlap_m=10)

    # create a coordinate calculator for the increment distance
    calculator = vincenty(meters=dist_bw_centers_m)

    points = []  # array for collecting the circle centers

    # position first point so the circle intersects with the sw corner of bounds
    starting_pt = vincenty(kilometers=radius_km).destination(
        point=(bounds.s_lat, bounds.w_lng),
        bearing=45
    )

    # get the starting latitude
    lat = starting_pt.latitude

    # find the number of rows of circles needed to span the height of the polygon
    rows = int(math.ceil(bounds.height_m / dist_bw_centers_m))

    for dummy_row_idx in range(rows):

        # reset the starting longitude before each west-to-east loop
        lng = starting_pt.longitude

        # get the distance between w_lng and e_lng at the current latitude
        width_m = bounds.get_width_at_latitude_m(lat)

        # find the number of columns of circles needed to span the width
        cols = int(math.ceil(width_m / dist_bw_centers_m))

        for dummy_col_idx in range(cols):

            # add current coordinates to point array
            points.append((lng, lat))

            # calculate next point to the east and increment longitude
            lng = calculator.destination(point=(lat, lng), bearing=90).longitude

        # calculate next point to the north and increment latitude
        lat = calculator.destination(point=(lat, lng), bearing=0).latitude

    return points