Source code for cartopy.mpl.patch

# Copyright Cartopy Contributors
# This file is part of Cartopy and is released under the LGPL license.
# See COPYING and COPYING.LESSER in the root of the repository for full
# licensing details.
Provide shapely geometry <-> matplotlib path support.

See also `Shapely Geometric Objects <see_also_shapely>`_
and `Matplotlib Path API <>`_.

.. see_also_shapely:


import numpy as np
from matplotlib.path import Path
import shapely.geometry as sgeom

[docs]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 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)}.')
[docs]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, :],[:-1]
[docs]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) # 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) # 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 if path_codes[-1] == Path.CLOSEPOLY: path_verts[-1, :] = path_verts[0, :] 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) 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) # If geom is a Polygon and is contained within the last geom in # collection, add it to its list of internal polygons, otherwise # simply append it as a new external geom. 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)): collection[-1][1].append(geom.exterior) elif isinstance(geom, sgeom.Point): other_result_geoms.append(geom) else: collection.append((geom, [])) # 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: # XXX worry about islands within lakes geom = sgeom.Polygon(external_geom.exterior, internal_polys) else: geom = external_geom # Correctly orientate the polygon (ccw) if isinstance(geom, sgeom.Polygon): if force_ccw and not geom.exterior.is_ccw: geom = sgeom.polygon.orient(geom) geom_collection.append(geom) # 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)] # 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)) result = list(filter(not_zero_poly, geom_collection)) return result + other_result_geoms