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# Copyright Crown and Cartopy Contributors | ||
# | ||
# This file is part of Cartopy and is released under the BSD 3-clause license. | ||
# See LICENSE in the root of the repository for full licensing details. | ||
""" | ||
Extra functionality that is primarily intended for developers, providing support for | ||
transforming between Shapely geometries and Matplotlib paths. | ||
See also `Shapely Geometric Objects | ||
<https://shapely.readthedocs.io/en/latest/manual.html#geometric-objects>`_ | ||
and `Matplotlib Path API <https://matplotlib.org/stable/api/path_api.html>`_. | ||
""" | ||
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from matplotlib.path import Path | ||
import numpy as np | ||
import shapely.geometry as sgeom | ||
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def _ensure_path_closed(path): | ||
""" | ||
Method to ensure that a path contains only closed sub-paths. | ||
Parameters | ||
---------- | ||
path | ||
A :class:`matplotlib.path.Path` instance. | ||
Returns | ||
------- | ||
path | ||
A :class:`matplotlib.path.Path` instance with only closed polygons. | ||
""" | ||
# Split path into potential sub-paths and close all polygons | ||
# (explicitly disable path simplification applied in to_polygons) | ||
should_simplify = path.should_simplify | ||
try: | ||
path.should_simplify = False | ||
polygons = path.to_polygons() | ||
finally: | ||
path.should_simplify = should_simplify | ||
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codes, vertices = [], [] | ||
for poly in polygons: | ||
vertices.extend([poly[0], *poly]) | ||
codes.extend([Path.MOVETO, *[Path.LINETO]*(len(poly) - 1), Path.CLOSEPOLY]) | ||
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return Path(vertices, codes) | ||
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def geos_to_path(shape): | ||
""" | ||
Create a list of :class:`matplotlib.path.Path` objects that describe | ||
a shape. | ||
Parameters | ||
---------- | ||
shape | ||
A list, tuple or single instance of any of the following | ||
types: :class:`shapely.geometry.point.Point`, | ||
:class:`shapely.geometry.linestring.LineString`, | ||
:class:`shapely.geometry.linestring.LinearRing`, | ||
:class:`shapely.geometry.polygon.Polygon`, | ||
:class:`shapely.geometry.multipoint.MultiPoint`, | ||
:class:`shapely.geometry.multipolygon.MultiPolygon`, | ||
:class:`shapely.geometry.multilinestring.MultiLineString`, | ||
:class:`shapely.geometry.collection.GeometryCollection`, | ||
or any type with a _as_mpl_path() method. | ||
Returns | ||
------- | ||
paths | ||
A list of :class:`matplotlib.path.Path` objects. | ||
""" | ||
if isinstance(shape, (list, tuple)): | ||
paths = [] | ||
for shp in shape: | ||
paths.extend(geos_to_path(shp)) | ||
return paths | ||
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if isinstance(shape, sgeom.LinearRing): | ||
return [Path(np.column_stack(shape.xy), closed=True)] | ||
elif isinstance(shape, (sgeom.LineString, sgeom.Point)): | ||
return [Path(np.column_stack(shape.xy))] | ||
elif isinstance(shape, sgeom.Polygon): | ||
def poly_codes(poly): | ||
codes = np.ones(len(poly.xy[0])) * Path.LINETO | ||
codes[0] = Path.MOVETO | ||
codes[-1] = Path.CLOSEPOLY | ||
return codes | ||
if shape.is_empty: | ||
return [] | ||
vertices = np.concatenate([np.array(shape.exterior.xy)] + | ||
[np.array(ring.xy) for ring in | ||
shape.interiors], 1).T | ||
codes = np.concatenate([poly_codes(shape.exterior)] + | ||
[poly_codes(ring) for ring in shape.interiors]) | ||
return [Path(vertices, codes)] | ||
elif isinstance(shape, (sgeom.MultiPolygon, sgeom.GeometryCollection, | ||
sgeom.MultiLineString, sgeom.MultiPoint)): | ||
paths = [] | ||
for geom in shape.geoms: | ||
paths.extend(geos_to_path(geom)) | ||
return paths | ||
elif hasattr(shape, '_as_mpl_path'): | ||
vertices, codes = shape._as_mpl_path() | ||
return [Path(vertices, codes)] | ||
else: | ||
raise ValueError(f'Unsupported shape type {type(shape)}.') | ||
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def path_segments(path, **kwargs): | ||
""" | ||
Create an array of vertices and a corresponding array of codes from a | ||
:class:`matplotlib.path.Path`. | ||
Parameters | ||
---------- | ||
path | ||
A :class:`matplotlib.path.Path` instance. | ||
Other Parameters | ||
---------------- | ||
kwargs | ||
See :func:`matplotlib.path.iter_segments` for details of the keyword | ||
arguments. | ||
Returns | ||
------- | ||
vertices, codes | ||
A (vertices, codes) tuple, where vertices is a numpy array of | ||
coordinates, and codes is a numpy array of matplotlib path codes. | ||
See :class:`matplotlib.path.Path` for information on the types of | ||
codes and their meanings. | ||
""" | ||
pth = path.cleaned(**kwargs) | ||
return pth.vertices[:-1, :], pth.codes[:-1] | ||
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def path_to_geos(path, force_ccw=False): | ||
""" | ||
Create a list of Shapely geometric objects from a | ||
:class:`matplotlib.path.Path`. | ||
Parameters | ||
---------- | ||
path | ||
A :class:`matplotlib.path.Path` instance. | ||
Other Parameters | ||
---------------- | ||
force_ccw | ||
Boolean flag determining whether the path can be inverted to enforce | ||
ccw. Defaults to False. | ||
Returns | ||
------- | ||
A list of instances of the following type(s): | ||
:class:`shapely.geometry.polygon.Polygon`, | ||
:class:`shapely.geometry.linestring.LineString` and/or | ||
:class:`shapely.geometry.multilinestring.MultiLineString`. | ||
""" | ||
# Convert path into numpy array of vertices (and associated codes) | ||
path_verts, path_codes = path_segments(path, curves=False) | ||
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# Split into subarrays such that each subarray consists of connected | ||
# line segments based on the start of each one being marked by a | ||
# matplotlib MOVETO code. | ||
verts_split_inds = np.where(path_codes == Path.MOVETO)[0] | ||
verts_split = np.split(path_verts, verts_split_inds) | ||
codes_split = np.split(path_codes, verts_split_inds) | ||
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# Iterate through the vertices generating a list of | ||
# (external_geom, [internal_polygons]) tuples. | ||
other_result_geoms = [] | ||
collection = [] | ||
for path_verts, path_codes in zip(verts_split, codes_split): | ||
if len(path_verts) == 0: | ||
continue | ||
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if path_codes[-1] == Path.CLOSEPOLY: | ||
path_verts[-1, :] = path_verts[0, :] | ||
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verts_same_as_first = np.isclose(path_verts[0, :], path_verts[1:, :], | ||
rtol=1e-10, atol=1e-13) | ||
verts_same_as_first = np.logical_and.reduce(verts_same_as_first, | ||
axis=1) | ||
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if all(verts_same_as_first): | ||
geom = sgeom.Point(path_verts[0, :]) | ||
elif path_verts.shape[0] > 4 and path_codes[-1] == Path.CLOSEPOLY: | ||
geom = sgeom.Polygon(path_verts[:-1, :]) | ||
else: | ||
geom = sgeom.LineString(path_verts) | ||
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# If geom is a Polygon and is contained within the last geom in | ||
# collection, it usually needs to be an interior to that geom (e.g. a | ||
# lake within a land mass). Sometimes there is a further geom within | ||
# this interior (e.g. an island in a lake, or some instances of | ||
# contours). This needs to be a new external geom in the collection. | ||
if geom.is_empty: | ||
pass | ||
elif (len(collection) > 0 and | ||
isinstance(collection[-1][0], sgeom.Polygon) and | ||
isinstance(geom, sgeom.Polygon) and | ||
collection[-1][0].contains(geom.exterior)): | ||
if any(internal.contains(geom) for internal in collection[-1][1]): | ||
collection.append((geom, [])) | ||
else: | ||
collection[-1][1].append(geom) | ||
elif isinstance(geom, sgeom.Point): | ||
other_result_geoms.append(geom) | ||
else: | ||
collection.append((geom, [])) | ||
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# Convert each (external_geom, [internal_polygons]) pair into a | ||
# a shapely Polygon that encapsulates the internal polygons, if the | ||
# external geom is a LineString leave it alone. | ||
geom_collection = [] | ||
for external_geom, internal_polys in collection: | ||
if internal_polys: | ||
exteriors = [geom.exterior for geom in internal_polys] | ||
geom = sgeom.Polygon(external_geom.exterior, exteriors) | ||
else: | ||
geom = external_geom | ||
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# Correctly orientate the polygon (ccw) | ||
if isinstance(geom, sgeom.Polygon): | ||
if force_ccw and not geom.exterior.is_ccw: | ||
geom = sgeom.polygon.orient(geom) | ||
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geom_collection.append(geom) | ||
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# If the geom_collection only contains LineStrings combine them | ||
# into a single MultiLinestring. | ||
if geom_collection and all(isinstance(geom, sgeom.LineString) for | ||
geom in geom_collection): | ||
geom_collection = [sgeom.MultiLineString(geom_collection)] | ||
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# Remove any zero area Polygons | ||
def not_zero_poly(geom): | ||
return ((isinstance(geom, sgeom.Polygon) and not geom.is_empty and | ||
geom.area != 0) or | ||
not isinstance(geom, sgeom.Polygon)) | ||
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result = list(filter(not_zero_poly, geom_collection)) | ||
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return result + other_result_geoms |