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shapely_utils.py
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shapely_utils.py
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from shapely.geometry import LineString
from shapely.geometry import Point as shapely_Point
from geometry_basics import *
# shapely_linestring_to_way
#
# Convert shapely linestring object to list of Point()
#
def shapely_linestring_to_way(geometry):
assert (geometry.geom_type == "LineString"), "Unexpected geometry type"
xl, yl = geometry.xy
way = []
for x, y in zip(xl, yl):
p = Point(x, y)
if len(way) > 0 and p == way[-1]:
# skip duplicate points (quite common in NVDB data)
continue
way.append(p)
return way
# simplify_way()
#
# Remove excess amount of points from geometry using Douglas-Peucker algorithm,
# here imported from Shapely
#
def simplify_way(points, epsilon):
if len(points) <= 2:
return points
ls = LineString(points).simplify(epsilon, preserve_topology=False)
return shapely_linestring_to_way(ls)
def way_is_self_crossing(points):
if len(points) <= 2:
return False
ls = LineString(points)
if ls.is_simple:
return False
# Shapely considers P-shaped loops to not be simple, but these are okay according to OSM
# so we say that those are not self-crossing.
idx = None
for p in points[1:-1]:
if p == points[0]:
if idx is not None:
return True
idx = 0
elif p == points[-1]:
if idx is not None:
return True
idx = -1
if idx is None:
return True
if idx == 0:
return not LineString(points[1:]).is_simple
return not LineString(points[:-1]).is_simple
def split_self_crossing_way(points):
# very inefficient, but okay since it's used rarely
way = points.copy()
new_ways = []
while len(way) > 1:
nl = len(way)
while way_is_self_crossing(way[:nl]):
nl -= 1
new_ways.append(way[:nl])
way = way[nl-1:]
return new_ways
def way_is_inside_or_crossing(polygon, points):
if not isinstance(points, list):
return polygon.contains(shapely_Point(points.x, points.y))
ls = LineString(points)
return polygon.contains(ls) or polygon.intersects(ls)
def shortest_way_inside_or_crossing(polygon, points):
if points is None:
return None
if polygon is None:
return points.copy()
ls = LineString(points)
if not polygon.intersects(ls):
if not polygon.contains(ls):
return None
return points.copy()
fp = shapely_Point(points[0].x, points[0].y)
lp = shapely_Point(points[-1].x, points[-1].y)
if len(points) <= 2 or (polygon.contains(fp) and polygon.contains(lp)):
return points.copy()
if not polygon.contains(lp):
idx = len(points) - 2
while not polygon.contains(shapely_Point(points[idx].x, points[idx].y)) and idx > 0:
idx -= 1
points = points[:idx+2]
if not polygon.contains(fp) and len(points) > 2:
idx = 1
while not polygon.contains(shapely_Point(points[idx].x, points[idx].y)) and idx < len(points):
idx += 1
points = points[idx-1:]
return points.copy()