import unittest
import pytest
import shapely
from shapely.algorithms.polylabel import polylabel
from shapely.geometry import LineString, Point, Polygon
class PolylabelTestCase(unittest.TestCase):
def test_polylabel(self):
"""
Finds pole of inaccessibility for a polygon with a tolerance of 10
"""
polygon = LineString(
[(0, 0), (50, 200), (100, 100), (20, 50), (-100, -20), (-150, -200)]
).buffer(100)
label = polylabel(polygon, tolerance=0.001)
expected = Point(59.733, 111.330)
assert expected.equals_exact(label, 1e-3)
def test_concave_polygon(self):
"""
Finds pole of inaccessibility for a concave polygon and ensures that
the point is inside.
"""
concave_polygon = LineString([(500, 0), (0, 0), (0, 500), (500, 500)]).buffer(
100
)
label = polylabel(concave_polygon)
assert concave_polygon.contains(label)
def test_rectangle_special_case(self):
"""
The centroid algorithm used is vulnerable to floating point errors
and can give unexpected results for rectangular polygons. Test
that this special case is handled correctly.
https://github.com/mapbox/polylabel/issues/3
"""
polygon = Polygon(
[
(32.71997, -117.19310),
(32.71997, -117.21065),
(32.72408, -117.21065),
(32.72408, -117.19310),
]
)
label = polylabel(polygon)
if shapely.geos_version >= (3, 12, 0):
# recent GEOS corrects for this
assert label.coords[:] == [(32.722025, -117.201875)]
else:
# older versions not
assert label.coords[:] == [(32.722025, -117.208595)]
def test_polygon_with_hole(self):
"""
Finds pole of inaccessibility for a polygon with a hole
https://github.com/shapely/shapely/issues/817
"""
polygon = Polygon(
shell=[(0, 0), (10, 0), (10, 10), (0, 10), (0, 0)],
holes=[[(2, 2), (6, 2), (6, 6), (2, 6), (2, 2)]],
)
label = polylabel(polygon, 0.05)
assert label.x == pytest.approx(7.65625)
assert label.y == pytest.approx(7.65625)
@pytest.mark.skipif(
shapely.geos_version < (3, 12, 0), reason="Fails with GEOS < 3.12"
)
def test_polygon_infinite_loop(self):
# https://github.com/shapely/shapely/issues/1836
# corner case that caused an infinite loop in the old custom implemetation
polygon = shapely.from_wkt(
"POLYGON ((536520.0679737709 5438764.374763639, 536520.0679737704 5438764.374763602, 536520.0679737709 5438764.374763642, 536520.0679737709 5438764.374763639))" # noqa: E501
)
label = polylabel(polygon)
assert label.x == pytest.approx(536520.068)
assert label.y == pytest.approx(5438764.375)