# 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. """ Implements RasterSource classes which can retrieve imagery from web services such as WMS and WMTS. The matplotlib interface can make use of RasterSources via the :meth:`cartopy.mpl.geoaxes.GeoAxes.add_raster` method, with additional specific methods which make use of this for WMS and WMTS (:meth:`~cartopy.mpl.geoaxes.GeoAxes.add_wms` and :meth:`~cartopy.mpl.geoaxes.GeoAxes.add_wmts`). An example of using WMTS in this way can be found at :ref:`sphx_glr_gallery_web_services_wmts.py`. """ import collections import io import math from pathlib import Path from urllib.parse import urlparse import warnings import weakref from xml.etree import ElementTree import numpy as np from PIL import Image import shapely.geometry as sgeom import cartopy try: import owslib.util from owslib.wfs import WebFeatureService from owslib.wms import WebMapService import owslib.wmts _OWSLIB_AVAILABLE = True except ImportError: WebMapService = None WebFeatureService = None _OWSLIB_AVAILABLE = False import cartopy.crs as ccrs from cartopy.img_transform import warp_array from cartopy.io import LocatedImage, RasterSource _OWSLIB_REQUIRED = 'OWSLib is required to use OGC web services.' # Hardcode some known EPSG codes for now. # The order given here determines the preferred SRS for WMS retrievals. _CRS_TO_OGC_SRS = collections.OrderedDict( [(ccrs.PlateCarree(), ['EPSG:4326']), (ccrs.Mercator.GOOGLE, ['EPSG:3857', 'EPSG:900913']), (ccrs.OSGB(approx=True), ['EPSG:27700']) ]) # Standard pixel size of 0.28 mm as defined by WMTS. METERS_PER_PIXEL = 0.28e-3 _WGS84_METERS_PER_UNIT = 2 * math.pi * 6378137 / 360 METERS_PER_UNIT = { 'urn:ogc:def:crs:EPSG::27700': 1, 'urn:ogc:def:crs:EPSG::900913': 1, 'urn:ogc:def:crs:OGC:1.3:CRS84': _WGS84_METERS_PER_UNIT, 'urn:ogc:def:crs:EPSG::3031': 1, 'urn:ogc:def:crs:EPSG::3413': 1, 'urn:ogc:def:crs:EPSG::3857': 1, 'urn:ogc:def:crs:EPSG:6.18.3:3857': 1 } _URN_TO_CRS = collections.OrderedDict( [('urn:ogc:def:crs:OGC:1.3:CRS84', ccrs.PlateCarree()), ('urn:ogc:def:crs:EPSG::4326', ccrs.PlateCarree()), ('urn:ogc:def:crs:EPSG::900913', ccrs.Mercator.GOOGLE), ('urn:ogc:def:crs:EPSG::27700', ccrs.OSGB(approx=True)), ('urn:ogc:def:crs:EPSG::3031', ccrs.Stereographic( central_latitude=-90, true_scale_latitude=-71)), ('urn:ogc:def:crs:EPSG::3413', ccrs.Stereographic( central_longitude=-45, central_latitude=90, true_scale_latitude=70)), ('urn:ogc:def:crs:EPSG::3857', ccrs.Mercator.GOOGLE), ('urn:ogc:def:crs:EPSG:6.18.3:3857', ccrs.Mercator.GOOGLE) ]) # XML namespace definitions _MAP_SERVER_NS = '{http://mapserver.gis.umn.edu/mapserver}' _GML_NS = '{http://www.opengis.net/gml}' def _warped_located_image(image, source_projection, source_extent, output_projection, output_extent, target_resolution): """ Reproject an Image from one source-projection and extent to another. Returns ------- LocatedImage A reprojected LocatedImage, the extent of which is >= the requested 'output_extent'. """ if source_projection == output_projection: extent = output_extent else: # Convert Image to numpy array (flipping so that origin # is 'lower'). # Convert to RGBA to keep the color palette in the regrid process # if any img, extent = warp_array(np.asanyarray(image.convert('RGBA'))[::-1], source_proj=source_projection, source_extent=source_extent, target_proj=output_projection, target_res=np.asarray(target_resolution, dtype=int), target_extent=output_extent, mask_extrapolated=True) # Convert arrays with masked RGB(A) values to non-masked RGBA # arrays, setting the alpha channel to zero for masked values. # This avoids unsightly grey boundaries appearing when the # extent is limited (i.e. not global). if np.ma.is_masked(img): img[:, :, 3] = np.where(np.any(img.mask, axis=2), 0, img[:, :, 3]) img = img.data # Convert warped image array back to an Image, undoing the # earlier flip. image = Image.fromarray(img[::-1]) return LocatedImage(image, extent) def _target_extents(extent, requested_projection, available_projection): """ Translate the requested extent in the display projection into a list of extents in the projection available from the service (multiple if it crosses seams). The extents are represented as (min_x, max_x, min_y, max_y). """ # Start with the requested area. min_x, max_x, min_y, max_y = extent target_box = sgeom.box(min_x, min_y, max_x, max_y) # If the requested area (i.e. target_box) is bigger (or nearly bigger) than # the entire output requested_projection domain, then we erode the request # area to avoid re-projection instabilities near the projection boundary. buffered_target_box = target_box.buffer(requested_projection.threshold, resolution=1) fudge_mode = buffered_target_box.contains(requested_projection.domain) if fudge_mode: target_box = requested_projection.domain.buffer( -requested_projection.threshold) # Translate the requested area into the server projection. polys = available_projection.project_geometry(target_box, requested_projection) # Return the polygons' rectangular bounds as extent tuples. target_extents = [] for poly in polys.geoms: min_x, min_y, max_x, max_y = poly.bounds if fudge_mode: # If we shrunk the request area before, then here we # need to re-inflate. radius = min(max_x - min_x, max_y - min_y) / 5.0 radius = min(radius, available_projection.threshold * 15) poly = poly.buffer(radius, resolution=1) # Prevent the expanded request going beyond the # limits of the requested_projection. poly = available_projection.domain.intersection(poly) min_x, min_y, max_x, max_y = poly.bounds target_extents.append((min_x, max_x, min_y, max_y)) return target_extents class WMSRasterSource(RasterSource): """ A WMS imagery retriever which can be added to a map. Note ---- Requires owslib and Pillow to work. No caching of retrieved maps is done with this WMSRasterSource. To reduce load on the WMS server it is encouraged to tile map requests and subsequently stitch them together to recreate a single raster, thus allowing for a more aggressive caching scheme, but this WMSRasterSource does not currently implement WMS tile fetching. Whilst not the same service, there is also a WMTSRasterSource which makes use of tiles and comes with built-in caching for fast repeated map retrievals. """ def __init__(self, service, layers, getmap_extra_kwargs=None): """ Parameters ---------- service: string or WebMapService instance The WebMapService instance, or URL of a WMS service, from whence to retrieve the image. layers: string or list of strings The name(s) of layers to use from the WMS service. getmap_extra_kwargs: dict, optional Extra keywords to pass through to the service's getmap method. If None, a dictionary with ``{'transparent': True}`` will be defined. """ if WebMapService is None: raise ImportError(_OWSLIB_REQUIRED) if isinstance(service, str): service = WebMapService(service) if isinstance(layers, str): layers = [layers] if getmap_extra_kwargs is None: getmap_extra_kwargs = {'transparent': True} if len(layers) == 0: raise ValueError('One or more layers must be defined.') for layer in layers: if layer not in service.contents: raise ValueError(f'The {layer!r} layer does not exist in ' 'this service.') #: The OWSLib WebMapService instance. self.service = service #: The names of the layers to fetch. self.layers = layers #: Extra kwargs passed through to the service's getmap request. self.getmap_extra_kwargs = getmap_extra_kwargs def _native_srs(self, projection): # Return a list of all SRS identifiers that correspond to the given # projection when known, otherwise return None. native_srs_list = _CRS_TO_OGC_SRS.get(projection, None) # If the native_srs could not be identified, return None if native_srs_list is None: return None else: # If the native_srs was identified, check if it is provided # by the service. If not return None to continue checking # for available fallback srs contents = self.service.contents for native_srs in native_srs_list: native_OK = all( native_srs.lower() in map( str.lower, contents[layer].crsOptions) for layer in self.layers ) if native_OK: return native_srs return None def _fallback_proj_and_srs(self): """ Return a :class:`cartopy.crs.Projection` and corresponding SRS string in which the WMS service can supply the requested layers. """ contents = self.service.contents for proj, srs_list in _CRS_TO_OGC_SRS.items(): for srs in srs_list: srs_OK = all( srs.lower() in map(str.lower, contents[layer].crsOptions) for layer in self.layers) if srs_OK: return proj, srs raise ValueError('The requested layers are not available in a ' 'known SRS.') def validate_projection(self, projection): if self._native_srs(projection) is None: self._fallback_proj_and_srs() def _image_and_extent(self, wms_proj, wms_srs, wms_extent, output_proj, output_extent, target_resolution): min_x, max_x, min_y, max_y = wms_extent wms_image = self.service.getmap(layers=self.layers, srs=wms_srs, bbox=(min_x, min_y, max_x, max_y), size=target_resolution, format='image/png', **self.getmap_extra_kwargs) wms_image = Image.open(io.BytesIO(wms_image.read())) return _warped_located_image(wms_image, wms_proj, wms_extent, output_proj, output_extent, target_resolution) def fetch_raster(self, projection, extent, target_resolution): target_resolution = [math.ceil(val) for val in target_resolution] wms_srs = self._native_srs(projection) if wms_srs is not None: wms_proj = projection wms_extents = [extent] else: # The SRS for the requested projection is not known, so # attempt to use the fallback and perform the necessary # transformations. wms_proj, wms_srs = self._fallback_proj_and_srs() # Calculate the bounding box(es) in WMS projection. wms_extents = _target_extents(extent, projection, wms_proj) located_images = [] for wms_extent in wms_extents: located_images.append(self._image_and_extent(wms_proj, wms_srs, wms_extent, projection, extent, target_resolution)) return located_images class WMTSRasterSource(RasterSource): """ A WMTS imagery retriever which can be added to a map. Uses tile caching for fast repeated map retrievals. Note ---- Requires owslib and Pillow to work. """ _shared_image_cache = weakref.WeakKeyDictionary() """ A nested mapping from WMTS, layer name, tile matrix name, tile row and tile column to the resulting PIL image:: {wmts: {(layer_name, tile_matrix_name): {(row, column): Image}}} This provides a significant boost when producing multiple maps of the same projection or with an interactive figure. """ def __init__(self, wmts, layer_name, gettile_extra_kwargs=None, cache=False): """ Parameters ---------- wmts The URL of the WMTS, or an owslib.wmts.WebMapTileService instance. layer_name The name of the layer to use. gettile_extra_kwargs: dict, optional Extra keywords (e.g. time) to pass through to the service's gettile method. cache : bool or str, optional If True, the default cache directory is used. If False, no cache is used. If a string, the string is used as the path to the cache. """ if WebMapService is None: raise ImportError(_OWSLIB_REQUIRED) if not (hasattr(wmts, 'tilematrixsets') and hasattr(wmts, 'contents') and hasattr(wmts, 'gettile')): wmts = owslib.wmts.WebMapTileService(wmts) try: layer = wmts.contents[layer_name] except KeyError: raise ValueError( f'Invalid layer name {layer_name!r} for WMTS at {wmts.url!r}') #: The OWSLib WebMapTileService instance. self.wmts = wmts #: The layer to fetch. self.layer = layer #: Extra kwargs passed through to the service's gettile request. if gettile_extra_kwargs is None: gettile_extra_kwargs = {} self.gettile_extra_kwargs = gettile_extra_kwargs self._matrix_set_name_map = {} # Enable a cache mechanism when cache is equal to True or to a path. self._default_cache = False if cache is True: self._default_cache = True self.cache_path = Path(cartopy.config["cache_dir"]) elif cache is False: self.cache_path = None else: self.cache_path = Path(cache) self.cache = set({}) self._load_cache() def _matrix_set_name(self, target_projection): key = id(target_projection) matrix_set_name = self._matrix_set_name_map.get(key) if matrix_set_name is None: if hasattr(self.layer, 'tilematrixsetlinks'): matrix_set_names = self.layer.tilematrixsetlinks.keys() else: matrix_set_names = self.layer.tilematrixsets def find_projection(match_projection): result = None for tile_matrix_set_name in matrix_set_names: matrix_sets = self.wmts.tilematrixsets tile_matrix_set = matrix_sets[tile_matrix_set_name] crs_urn = tile_matrix_set.crs tms_crs = None if crs_urn in _URN_TO_CRS: tms_crs = _URN_TO_CRS.get(crs_urn) elif ':EPSG:' in crs_urn: epsg_num = crs_urn.split(':')[-1] tms_crs = ccrs.epsg(int(epsg_num)) if tms_crs == match_projection: result = tile_matrix_set_name break return result # First search for a matrix set in the target projection. matrix_set_name = find_projection(target_projection) if matrix_set_name is None: # Search instead for a set in _any_ projection we can use. # Nothing to do for EPSG for possible_projection in _URN_TO_CRS.values(): # Look for supported projections (in a preferred order). matrix_set_name = find_projection(possible_projection) if matrix_set_name is not None: break if matrix_set_name is None: # Fail completely. available_urns = sorted({ self.wmts.tilematrixsets[name].crs for name in matrix_set_names}) msg = 'Unable to find tile matrix for projection.' msg += f'\n Projection: {target_projection}' msg += '\n Available tile CRS URNs:' msg += '\n ' + '\n '.join(available_urns) raise ValueError(msg) self._matrix_set_name_map[key] = matrix_set_name return matrix_set_name def validate_projection(self, projection): self._matrix_set_name(projection) def fetch_raster(self, projection, extent, target_resolution): matrix_set_name = self._matrix_set_name(projection) crs_urn = self.wmts.tilematrixsets[matrix_set_name].crs if crs_urn in _URN_TO_CRS: wmts_projection = _URN_TO_CRS[crs_urn] elif ':EPSG:' in crs_urn: epsg_num = crs_urn.split(':')[-1] wmts_projection = ccrs.epsg(int(epsg_num)) else: raise ValueError(f'Unknown coordinate reference system string:' f' {crs_urn}') if wmts_projection == projection: wmts_extents = [extent] else: # Calculate (possibly multiple) extents in the given projection. wmts_extents = _target_extents(extent, projection, wmts_projection) # Bump resolution by a small factor, as a weak alternative to # delivering a minimum projected resolution. # Generally, the desired area is smaller than the enclosing extent # in projection space and may have varying scaling, so the ideal # solution is a hard problem ! resolution_factor = 1.4 target_resolution = np.array(target_resolution) * resolution_factor width, height = target_resolution located_images = [] for wmts_desired_extent in wmts_extents: # Calculate target resolution for the actual polygon. Note that # this gives *every* polygon enough pixels for the whole result, # which is potentially excessive! min_x, max_x, min_y, max_y = wmts_desired_extent if wmts_projection == projection: max_pixel_span = min((max_x - min_x) / width, (max_y - min_y) / height) else: # X/Y orientation is arbitrary, so use a worst-case guess. max_pixel_span = (min(max_x - min_x, max_y - min_y) / max(width, height)) # Fetch a suitable image and its actual extent. wmts_image, wmts_actual_extent = self._wmts_images( self.wmts, self.layer, matrix_set_name, extent=wmts_desired_extent, max_pixel_span=max_pixel_span) # Return each (image, extent) as a LocatedImage. if wmts_projection == projection: located_image = LocatedImage(wmts_image, wmts_actual_extent) else: # Reproject the image to the desired projection. located_image = _warped_located_image( wmts_image, wmts_projection, wmts_actual_extent, output_projection=projection, output_extent=extent, target_resolution=target_resolution) located_images.append(located_image) return located_images @property def _cache_dir(self): """Return the name of the cache directory""" return self.cache_path / self.__class__.__name__ def _load_cache(self): """Load the cache""" if self.cache_path is not None: cache_dir = self._cache_dir if not cache_dir.exists(): cache_dir.mkdir(parents=True, exist_ok=True) if self._default_cache: warnings.warn( 'Cartopy created the following directory to cache ' f'WMTSRasterSource tiles: {cache_dir}') self.cache = self.cache.union(set(cache_dir.iterdir())) def _choose_matrix(self, tile_matrices, meters_per_unit, max_pixel_span): # Get the tile matrices in order of increasing resolution. tile_matrices = sorted(tile_matrices, key=lambda tm: tm.scaledenominator, reverse=True) # Find which tile matrix has the appropriate resolution. max_scale = max_pixel_span * meters_per_unit / METERS_PER_PIXEL for tm in tile_matrices: if tm.scaledenominator <= max_scale: return tm return tile_matrices[-1] def _tile_span(self, tile_matrix, meters_per_unit): pixel_span = (tile_matrix.scaledenominator * (METERS_PER_PIXEL / meters_per_unit)) tile_span_x = tile_matrix.tilewidth * pixel_span tile_span_y = tile_matrix.tileheight * pixel_span return tile_span_x, tile_span_y def _select_tiles(self, tile_matrix, tile_matrix_limits, tile_span_x, tile_span_y, extent): # Convert the requested extent from CRS coordinates to tile # indices. See annex H of the WMTS v1.0.0 spec. # NB. The epsilons get rid of any tiles which only just # (i.e. one part in a million) intrude into the requested # extent. Since these wouldn't be visible anyway there's nothing # to be gained by spending the time downloading them. min_x, max_x, min_y, max_y = extent matrix_min_x, matrix_max_y = tile_matrix.topleftcorner epsilon = 1e-6 min_col = int((min_x - matrix_min_x) / tile_span_x + epsilon) max_col = int((max_x - matrix_min_x) / tile_span_x - epsilon) min_row = int((matrix_max_y - max_y) / tile_span_y + epsilon) max_row = int((matrix_max_y - min_y) / tile_span_y - epsilon) # Clamp to the limits of the tile matrix. min_col = max(min_col, 0) max_col = min(max_col, tile_matrix.matrixwidth - 1) min_row = max(min_row, 0) max_row = min(max_row, tile_matrix.matrixheight - 1) # Clamp to any layer-specific limits on the tile matrix. if tile_matrix_limits: min_col = max(min_col, tile_matrix_limits.mintilecol) max_col = min(max_col, tile_matrix_limits.maxtilecol) min_row = max(min_row, tile_matrix_limits.mintilerow) max_row = min(max_row, tile_matrix_limits.maxtilerow) return min_col, max_col, min_row, max_row def _wmts_images(self, wmts, layer, matrix_set_name, extent, max_pixel_span): """ Add images from the specified WMTS layer and matrix set to cover the specified extent at an appropriate resolution. The zoom level (aka. tile matrix) is chosen to give the lowest possible resolution which still provides the requested quality. If insufficient resolution is available, the highest available resolution is used. Parameters ---------- wmts The owslib.wmts.WebMapTileService providing the tiles. layer The owslib.wmts.ContentMetadata (aka. layer) to draw. matrix_set_name The name of the matrix set to use. extent Tuple of (left, right, bottom, top) in Axes coordinates. max_pixel_span Preferred maximum pixel width or height in Axes coordinates. """ # Find which tile matrix has the appropriate resolution. tile_matrix_set = wmts.tilematrixsets[matrix_set_name] tile_matrices = tile_matrix_set.tilematrix.values() if tile_matrix_set.crs in METERS_PER_UNIT: meters_per_unit = METERS_PER_UNIT[tile_matrix_set.crs] elif ':EPSG:' in tile_matrix_set.crs: epsg_num = tile_matrix_set.crs.split(':')[-1] tms_crs = ccrs.epsg(int(epsg_num)) # catch UserWarning from .to_dict(), because the resulting # dictionary does not contain all information for all projections; # need only 'units' here with warnings.catch_warnings(): warnings.simplefilter("ignore") crs_dict = tms_crs.to_dict() crs_units = crs_dict.get('units', '') if crs_units != 'm': raise ValueError('Only unit "m" implemented for' ' EPSG projections.') meters_per_unit = 1 else: raise ValueError(f'Unknown coordinate reference system string:' f' {tile_matrix_set.crs}') tile_matrix = self._choose_matrix(tile_matrices, meters_per_unit, max_pixel_span) # Determine which tiles are required to cover the requested extent. tile_span_x, tile_span_y = self._tile_span(tile_matrix, meters_per_unit) tile_matrix_set_links = getattr(layer, 'tilematrixsetlinks', None) if tile_matrix_set_links is None: tile_matrix_limits = None else: tile_matrix_set_link = tile_matrix_set_links[matrix_set_name] tile_matrix_limits = tile_matrix_set_link.tilematrixlimits.get( tile_matrix.identifier) min_col, max_col, min_row, max_row = self._select_tiles( tile_matrix, tile_matrix_limits, tile_span_x, tile_span_y, extent) # Find the relevant section of the image cache. tile_matrix_id = tile_matrix.identifier cache_by_wmts = WMTSRasterSource._shared_image_cache cache_by_layer_matrix = cache_by_wmts.setdefault(wmts, {}) image_cache = cache_by_layer_matrix.setdefault((layer.id, tile_matrix_id), {}) # To avoid nasty seams between the individual tiles, we # accumulate the tile images into a single image. big_img = None n_rows = 1 + max_row - min_row n_cols = 1 + max_col - min_col # Ignore out-of-range errors if the current version of OWSLib # doesn't provide the regional information. ignore_out_of_range = tile_matrix_set_links is None for row in range(min_row, max_row + 1): for col in range(min_col, max_col + 1): # Get the tile's Image from the cache if possible. img_key = (row, col) img = image_cache.get(img_key) if img is None: # Try it from disk cache if self.cache_path is not None: filename = f"{img_key[0]}_{img_key[1]}.npy" cached_file = self._cache_dir / filename else: filename = None cached_file = None if cached_file in self.cache: img = Image.fromarray(np.load(cached_file, allow_pickle=False)) else: try: tile = wmts.gettile( layer=layer.id, tilematrixset=matrix_set_name, tilematrix=str(tile_matrix_id), row=str(row), column=str(col), **self.gettile_extra_kwargs) except owslib.util.ServiceException as exception: if ('TileOutOfRange' in exception.message and ignore_out_of_range): continue raise exception img = Image.open(io.BytesIO(tile.read())) image_cache[img_key] = img # save image to local cache if self.cache_path is not None: np.save(cached_file, img, allow_pickle=False) self.cache.add(filename) if big_img is None: size = (img.size[0] * n_cols, img.size[1] * n_rows) big_img = Image.new('RGBA', size, (255, 255, 255, 255)) top = (row - min_row) * tile_matrix.tileheight left = (col - min_col) * tile_matrix.tilewidth big_img.paste(img, (left, top)) if big_img is None: img_extent = None else: matrix_min_x, matrix_max_y = tile_matrix.topleftcorner min_img_x = matrix_min_x + tile_span_x * min_col max_img_y = matrix_max_y - tile_span_y * min_row img_extent = (min_img_x, min_img_x + n_cols * tile_span_x, max_img_y - n_rows * tile_span_y, max_img_y) return big_img, img_extent class WFSGeometrySource: """Web Feature Service (WFS) retrieval for Cartopy.""" def __init__(self, service, features, getfeature_extra_kwargs=None): """ Parameters ---------- service The URL of a WFS, or an instance of :class:`owslib.wfs.WebFeatureService`. features The typename(s) of the features from the WFS that will be retrieved and made available as geometries. getfeature_extra_kwargs: optional Extra keyword args to pass to the service's `getfeature` call. Defaults to None """ if WebFeatureService is None: raise ImportError(_OWSLIB_REQUIRED) if isinstance(service, str): # host name such as mapserver.gis.umn.edu or # agroenvgeo.data.inra.fr from full address # http://mapserver.gis.umn.edu/mapserver # or https://agroenvgeo.data.inra.fr:443/geoserver/wfs self.url = urlparse(service).hostname # WebFeatureService of owslib service = WebFeatureService(service) else: self.url = '' if isinstance(features, str): features = [features] if getfeature_extra_kwargs is None: getfeature_extra_kwargs = {} if not features: raise ValueError('One or more features must be specified.') for feature in features: if feature not in service.contents: raise ValueError( f'The {feature!r} feature does not exist in this service.') self.service = service self.features = features self.getfeature_extra_kwargs = getfeature_extra_kwargs self._default_urn = None def default_projection(self): """ Return a :class:`cartopy.crs.Projection` in which the WFS service can supply the requested features. """ # Using first element in crsOptions (default). if self._default_urn is None: default_urn = {self.service.contents[feature].crsOptions[0] for feature in self.features} if len(default_urn) != 1: ValueError('Failed to find a single common default SRS ' 'across all features (typenames).') else: default_urn = default_urn.pop() if (str(default_urn) not in _URN_TO_CRS) and ( ":EPSG:" not in str(default_urn) ): raise ValueError( f"Unknown mapping from SRS/CRS_URN {default_urn!r} to " "cartopy projection.") self._default_urn = default_urn if str(self._default_urn) in _URN_TO_CRS: return _URN_TO_CRS[str(self._default_urn)] elif ':EPSG:' in str(self._default_urn): epsg_num = str(self._default_urn).split(':')[-1] return ccrs.epsg(int(epsg_num)) else: raise ValueError(f'Unknown coordinate reference system:' f' {str(self._default_urn)}') def fetch_geometries(self, projection, extent): """ Return any Point, Linestring or LinearRing geometries available from the WFS that lie within the specified extent. Parameters ---------- projection: :class:`cartopy.crs.Projection` The projection in which the extent is specified and in which the geometries should be returned. Only the default (native) projection is supported. extent: four element tuple (min_x, max_x, min_y, max_y) tuple defining the geographic extent of the geometries to obtain. Returns ------- geoms A list of Shapely geometries. """ if self.default_projection() != projection: raise ValueError('Geometries are only available in projection ' f'{self.default_projection()!r}.') min_x, max_x, min_y, max_y = extent response = self.service.getfeature(typename=self.features, bbox=(min_x, min_y, max_x, max_y), **self.getfeature_extra_kwargs) geoms_by_srs = self._to_shapely_geoms(response) if not geoms_by_srs: geoms = [] elif len(geoms_by_srs) > 1: raise ValueError('Unexpected response from the WFS server. The ' 'geometries are in multiple SRSs, when only one ' 'was expected.') else: srs, geoms = list(geoms_by_srs.items())[0] # Attempt to verify the SRS associated with the geometries (if any) # matches the specified projection. if srs is not None: if srs in _URN_TO_CRS: geom_proj = _URN_TO_CRS[srs] if geom_proj != projection: raise ValueError( f'The geometries are not in expected projection. ' f'Expected {projection!r}, got {geom_proj!r}.') elif ':EPSG:' in srs: epsg_num = srs.split(':')[-1] geom_proj = ccrs.epsg(int(epsg_num)) if geom_proj != projection: raise ValueError( f'The EPSG geometries are not in expected ' f' projection. Expected {projection!r}, ' f' got {geom_proj!r}.') else: warnings.warn( f'Unable to verify matching projections due to ' f'incomplete mappings from SRS identifiers to cartopy ' f'projections. The geometries have an SRS of {srs!r}.') return geoms def _to_shapely_geoms(self, response): """ Convert polygon coordinate strings in WFS response XML to Shapely geometries. Parameters ---------- response: (file-like object) WFS response XML data. Returns ------- geoms_by_srs A dictionary containing geometries, with key-value pairs of the form {srsname: [geoms]}. """ linear_rings_data = [] linestrings_data = [] points_data = [] tree = ElementTree.parse(response) # Get geometries from http://mapserver.gis.umn.edu/mapserver # and other servers for node in tree.iter(): snode = str(node) if ((_MAP_SERVER_NS in snode) or (self.url and (self.url in snode) )): s1 = snode.split()[1] tag = s1[s1.find('}') + 1:-1] if ('geom' in tag) or ('Geom' in tag): # Find LinearRing geometries in our msGeometry node. find_str = f'.//{_GML_NS}LinearRing' if self._node_has_child(node, find_str): data = self._find_polygon_coords(node, find_str) linear_rings_data.extend(data) # Find LineString geometries in our msGeometry node. find_str = f'.//{_GML_NS}LineString' if self._node_has_child(node, find_str): data = self._find_polygon_coords(node, find_str) linestrings_data.extend(data) # Find Point geometries in our msGeometry node. find_str = f'.//{_GML_NS}Point' if self._node_has_child(node, find_str): data = self._find_polygon_coords(node, find_str) points_data.extend(data) geoms_by_srs = {} for srs, x, y in linear_rings_data: geoms_by_srs.setdefault(srs, []).append( sgeom.LinearRing(zip(x, y))) for srs, x, y in linestrings_data: geoms_by_srs.setdefault(srs, []).append( sgeom.LineString(zip(x, y))) for srs, x, y in points_data: geoms_by_srs.setdefault(srs, []).append( sgeom.Point(zip(x, y))) return geoms_by_srs def _find_polygon_coords(self, node, find_str): """ Return the x, y coordinate values for all the geometries in a given`node`. Parameters ---------- node: :class:`xml.etree.ElementTree.Element` Node of the parsed XML response. find_str: string A search string used to match subelements that contain the coordinates of interest, for example: './/{http://www.opengis.net/gml}LineString' Returns ------- data A list of (srsName, x_vals, y_vals) tuples. """ data = [] for polygon in node.findall(find_str): feature_srs = polygon.attrib.get('srsName') x, y = [], [] # We can have nodes called `coordinates` or `coord`. coordinates_find_str = f'{_GML_NS}coordinates' coords_find_str = f'{_GML_NS}coord' if self._node_has_child(polygon, coordinates_find_str): points = polygon.findtext(coordinates_find_str) coords = points.strip().split(' ') for coord in coords: x_val, y_val = coord.split(',') x.append(float(x_val)) y.append(float(y_val)) elif self._node_has_child(polygon, coords_find_str): for coord in polygon.findall(coords_find_str): x.append(float(coord.findtext(f'{_GML_NS}X'))) y.append(float(coord.findtext(f'{_GML_NS}Y'))) else: raise ValueError('Unable to find or parse coordinate values ' 'from the XML.') data.append((feature_srs, x, y)) return data @staticmethod def _node_has_child(node, find_str): """ Return whether `node` contains (at any sub-level), a node with name equal to `find_str`. """ element = node.find(find_str) return element is not None