"""Polygons and their linear ring components
"""
import numpy as np
import shapely
from shapely.algorithms.cga import is_ccw_impl, signed_area
from shapely.errors import TopologicalError
from shapely.geometry.base import BaseGeometry
from shapely.geometry.linestring import LineString
from shapely.geometry.point import Point
__all__ = ["Polygon", "LinearRing"]
def _unpickle_linearring(wkb):
linestring = shapely.from_wkb(wkb)
srid = shapely.get_srid(linestring)
linearring = shapely.linearrings(shapely.get_coordinates(linestring))
if srid:
linearring = shapely.set_srid(linearring, srid)
return linearring
class LinearRing(LineString):
"""
A geometry type composed of one or more line segments
that forms a closed loop.
A LinearRing is a closed, one-dimensional feature.
A LinearRing that crosses itself or touches itself at a single point is
invalid and operations on it may fail.
Parameters
----------
coordinates : sequence
A sequence of (x, y [,z]) numeric coordinate pairs or triples, or
an array-like with shape (N, 2) or (N, 3).
Also can be a sequence of Point objects.
Notes
-----
Rings are automatically closed. There is no need to specify a final
coordinate pair identical to the first.
Examples
--------
Construct a square ring.
>>> ring = LinearRing( ((0, 0), (0, 1), (1 ,1 ), (1 , 0)) )
>>> ring.is_closed
True
>>> list(ring.coords)
[(0.0, 0.0), (0.0, 1.0), (1.0, 1.0), (1.0, 0.0), (0.0, 0.0)]
>>> ring.length
4.0
"""
__slots__ = []
def __new__(self, coordinates=None):
if coordinates is None:
# empty geometry
# TODO better way?
return shapely.from_wkt("LINEARRING EMPTY")
elif isinstance(coordinates, LineString):
if type(coordinates) == LinearRing:
# return original objects since geometries are immutable
return coordinates
elif not coordinates.is_valid:
raise TopologicalError("An input LineString must be valid.")
else:
# LineString
# TODO convert LineString to LinearRing more directly?
coordinates = coordinates.coords
else:
if hasattr(coordinates, "__array__"):
coordinates = np.asarray(coordinates)
if isinstance(coordinates, np.ndarray) and np.issubdtype(
coordinates.dtype, np.number
):
pass
else:
# check coordinates on points
def _coords(o):
if isinstance(o, Point):
return o.coords[0]
else:
return [float(c) for c in o]
coordinates = np.array([_coords(o) for o in coordinates])
if not np.issubdtype(coordinates.dtype, np.number):
# conversion of coords to 2D array failed, this might be due
# to inconsistent coordinate dimensionality
raise ValueError("Inconsistent coordinate dimensionality")
if len(coordinates) == 0:
# empty geometry
# TODO better constructor + should shapely.linearrings handle this?
return shapely.from_wkt("LINEARRING EMPTY")
geom = shapely.linearrings(coordinates)
if not isinstance(geom, LinearRing):
raise ValueError("Invalid values passed to LinearRing constructor")
return geom
@property
def __geo_interface__(self):
return {"type": "LinearRing", "coordinates": tuple(self.coords)}
def __reduce__(self):
"""WKB doesn't differentiate between LineString and LinearRing so we
need to move the coordinate sequence into the correct geometry type"""
return (_unpickle_linearring, (shapely.to_wkb(self, include_srid=True),))
@property
def is_ccw(self):
"""True is the ring is oriented counter clock-wise"""
return bool(is_ccw_impl()(self))
@property
def is_simple(self):
"""True if the geometry is simple, meaning that any self-intersections
are only at boundary points, else False"""
return bool(shapely.is_simple(self))
shapely.lib.registry[2] = LinearRing
class InteriorRingSequence:
_parent = None
_ndim = None
_index = 0
_length = 0
def __init__(self, parent):
self._parent = parent
self._ndim = parent._ndim
def __iter__(self):
self._index = 0
self._length = self.__len__()
return self
def __next__(self):
if self._index < self._length:
ring = self._get_ring(self._index)
self._index += 1
return ring
else:
raise StopIteration
def __len__(self):
return shapely.get_num_interior_rings(self._parent)
def __getitem__(self, key):
m = self.__len__()
if isinstance(key, int):
if key + m < 0 or key >= m:
raise IndexError("index out of range")
if key < 0:
i = m + key
else:
i = key
return self._get_ring(i)
elif isinstance(key, slice):
res = []
start, stop, stride = key.indices(m)
for i in range(start, stop, stride):
res.append(self._get_ring(i))
return res
else:
raise TypeError("key must be an index or slice")
def _get_ring(self, i):
return shapely.get_interior_ring(self._parent, i)
class Polygon(BaseGeometry):
"""
A geometry type representing an area that is enclosed by a linear ring.
A polygon is a two-dimensional feature and has a non-zero area. It may
have one or more negative-space "holes" which are also bounded by linear
rings. If any rings cross each other, the feature is invalid and
operations on it may fail.
Parameters
----------
shell : sequence
A sequence of (x, y [,z]) numeric coordinate pairs or triples, or
an array-like with shape (N, 2) or (N, 3).
Also can be a sequence of Point objects.
holes : sequence
A sequence of objects which satisfy the same requirements as the
shell parameters above
Attributes
----------
exterior : LinearRing
The ring which bounds the positive space of the polygon.
interiors : sequence
A sequence of rings which bound all existing holes.
Examples
--------
Create a square polygon with no holes
>>> coords = ((0., 0.), (0., 1.), (1., 1.), (1., 0.), (0., 0.))
>>> polygon = Polygon(coords)
>>> polygon.area
1.0
"""
__slots__ = []
def __new__(self, shell=None, holes=None):
if shell is None:
# empty geometry
# TODO better way?
return shapely.from_wkt("POLYGON EMPTY")
elif isinstance(shell, Polygon):
# return original objects since geometries are immutable
return shell
else:
shell = LinearRing(shell)
if holes is not None:
if len(holes) == 0:
# shapely constructor cannot handle holes=[]
holes = None
else:
holes = [LinearRing(ring) for ring in holes]
geom = shapely.polygons(shell, holes=holes)
if not isinstance(geom, Polygon):
raise ValueError("Invalid values passed to Polygon constructor")
return geom
@property
def exterior(self):
return shapely.get_exterior_ring(self)
@property
def interiors(self):
if self.is_empty:
return []
return InteriorRingSequence(self)
@property
def coords(self):
raise NotImplementedError(
"Component rings have coordinate sequences, but the polygon does not"
)
@property
def __geo_interface__(self):
if self.exterior == LinearRing():
coords = []
else:
coords = [tuple(self.exterior.coords)]
for hole in self.interiors:
coords.append(tuple(hole.coords))
return {"type": "Polygon", "coordinates": tuple(coords)}
def svg(self, scale_factor=1.0, fill_color=None, opacity=None):
"""Returns SVG path element for the Polygon geometry.
Parameters
==========
scale_factor : float
Multiplication factor for the SVG stroke-width. Default is 1.
fill_color : str, optional
Hex string for fill color. Default is to use "#66cc99" if
geometry is valid, and "#ff3333" if invalid.
opacity : float
Float number between 0 and 1 for color opacity. Default value is 0.6
"""
if self.is_empty:
return ""
if fill_color is None:
fill_color = "#66cc99" if self.is_valid else "#ff3333"
if opacity is None:
opacity = 0.6
exterior_coords = [["{},{}".format(*c) for c in self.exterior.coords]]
interior_coords = [
["{},{}".format(*c) for c in interior.coords] for interior in self.interiors
]
path = " ".join(
[
"M {} L {} z".format(coords[0], " L ".join(coords[1:]))
for coords in exterior_coords + interior_coords
]
)
return (
''
).format(2.0 * scale_factor, path, fill_color, opacity)
@classmethod
def from_bounds(cls, xmin, ymin, xmax, ymax):
"""Construct a `Polygon()` from spatial bounds."""
return cls([(xmin, ymin), (xmin, ymax), (xmax, ymax), (xmax, ymin)])
shapely.lib.registry[3] = Polygon
def orient(polygon, sign=1.0):
s = float(sign)
rings = []
ring = polygon.exterior
if signed_area(ring) / s >= 0.0:
rings.append(ring)
else:
rings.append(list(ring.coords)[::-1])
for ring in polygon.interiors:
if signed_area(ring) / s <= 0.0:
rings.append(ring)
else:
rings.append(list(ring.coords)[::-1])
return Polygon(rings[0], rings[1:])