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# Authors: see git history
#
# Copyright (c) 2010 Authors
# Licensed under the GNU GPL version 3.0 or later. See the file LICENSE for details.
import math
from shapely.geometry import LineString, LinearRing, MultiLineString, Polygon, MultiPolygon, MultiPoint, GeometryCollection
from shapely.geometry import Point as ShapelyPoint
def cut(line, distance, normalized=False):
""" Cuts a LineString in two at a distance from its starting point.
This is an example in the Shapely documentation.
"""
if normalized:
distance *= line.length
if distance <= 0.0:
return [None, line]
elif distance >= line.length:
return [line, None]
coords = list(ShapelyPoint(p) for p in line.coords)
traveled = 0
last_point = coords[0]
for i, p in enumerate(coords[1:], 1):
traveled += p.distance(last_point)
last_point = p
if traveled == distance:
return [
LineString(coords[:i + 1]),
LineString(coords[i:])]
if traveled > distance:
cp = line.interpolate(distance)
return [
LineString(coords[:i] + [(cp.x, cp.y)]),
LineString([(cp.x, cp.y)] + coords[i:])]
def cut_multiple(line, distances, normalized=False):
"""Cut a LineString at multiple distances along that line.
Always returns a list of N + 1 members, where N is the number of distances
provided. Some members of the list may be None, indicating an empty
segment. This can happen if one of the distances is at the start or end
of the line, or if duplicate distances are provided.
Returns:
a list of LineStrings or None values"""
distances = list(sorted(distances))
segments = [line]
distance_so_far = 0
nones = []
for distance in distances:
segment = segments.pop()
before, after = cut(segment, distance - distance_so_far, normalized)
segments.append(before)
if after is None:
nones.append(after)
else:
if before is not None:
distance_so_far += before.length
segments.append(after)
segments.extend(nones)
return segments
def roll_linear_ring(ring, distance, normalized=False):
"""Make a linear ring start at a different point.
Example: A B C D E F G A -> D E F G A B C
Same linear ring, different ordering of the coordinates.
"""
if not isinstance(ring, LinearRing):
# In case they handed us a LineString
ring = LinearRing(ring)
pieces = cut(LinearRing(ring), distance, normalized=False)
if None in pieces:
# We cut exactly at the start or end.
return ring
# The first and last point in a linear ring are duplicated, so we omit one
# copy
return LinearRing(pieces[1].coords[:] + pieces[0].coords[1:])
def reverse_line_string(line_string):
return LineString(line_string.coords[::-1])
def ensure_multi_line_string(thing):
"""Given either a MultiLineString or a single LineString, return a MultiLineString"""
if isinstance(thing, LineString):
return MultiLineString([thing])
else:
return thing
def ensure_geometry_collection(thing):
"""Given either some kind of geometry or a GeometryCollection, return a GeometryCollection"""
if isinstance(thing, (MultiLineString, MultiPolygon, MultiPoint)):
return GeometryCollection(thing.geoms)
elif isinstance(thing, GeometryCollection):
return thing
else:
return GeometryCollection([thing])
def ensure_multi_polygon(thing):
"""Given either a MultiPolygon or a single Polygon, return a MultiPolygon"""
if isinstance(thing, Polygon):
return MultiPolygon([thing])
else:
return thing
def cut_path(points, length):
"""Return a subsection of at the start of the path that is length units long.
Given a path denoted by a set of points, walk along it until we've travelled
the specified length and return a new path up to that point.
If the original path isn't that long, just return it as is.
"""
if len(points) < 2:
return points
path = LineString(points)
subpath, rest = cut(path, length)
return [Point(*point) for point in subpath.coords]
class Point:
def __init__(self, x: float, y: float):
self.x = x
self.y = y
@classmethod
def from_shapely_point(cls, point):
return cls(point.x, point.y)
@classmethod
def from_tuple(cls, point):
return cls(point[0], point[1])
def __json__(self):
return vars(self)
def __add__(self, other):
return self.__class__(self.x + other.x, self.y + other.y)
def __sub__(self, other):
return self.__class__(self.x - other.x, self.y - other.y)
def mul(self, scalar):
return self.__class__(self.x * scalar, self.y * scalar)
def __mul__(self, other):
if isinstance(other, Point):
# dot product
return self.x * other.x + self.y * other.y
elif isinstance(other, (int, float)):
return self.__class__(self.x * other, self.y * other)
else:
raise ValueError("cannot multiply %s by %s" % (type(self), type(other)))
def __neg__(self):
return self * -1
def __rmul__(self, other):
if isinstance(other, (int, float)):
return self.__mul__(other)
else:
raise ValueError("cannot multiply %s by %s" % (type(self), type(other)))
def __truediv__(self, other):
if isinstance(other, (int, float)):
return self * (1.0 / other)
else:
raise ValueError("cannot divide %s by %s" % (type(self), type(other)))
def __eq__(self, other):
return self.x == other.x and self.y == other.y
def __repr__(self):
return "%s(%s,%s)" % (type(self), self.x, self.y)
def length(self):
return math.sqrt(math.pow(self.x, 2.0) + math.pow(self.y, 2.0))
def distance(self, other):
return (other - self).length()
def unit(self):
return self.mul(1.0 / self.length())
def angle(self):
return math.atan2(self.y, self.x)
def rotate_left(self):
return self.__class__(-self.y, self.x)
def rotate(self, angle):
return self.__class__(self.x * math.cos(angle) - self.y * math.sin(angle), self.y * math.cos(angle) + self.x * math.sin(angle))
def scale(self, x_scale, y_scale):
return self.__class__(self.x * x_scale, self.y * y_scale)
def as_int(self):
return self.__class__(int(round(self.x)), int(round(self.y)))
def as_tuple(self):
return (self.x, self.y)
def __getitem__(self, item):
return self.as_tuple()[item]
def __len__(self):
return 2
def __str__(self):
return "({0:.3f}, {1:.3f})".format(self.x, self.y)
def line_string_to_point_list(line_string):
return [Point(*point) for point in line_string.coords]
def coordinate_list_to_point_list(coordinate_list):
return [Point.from_tuple(coords) for coords in coordinate_list]
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