ENH: Add Stadia Maps image tile server class

docs/source/reference/io.rst

@@ -63,6 +63,7 @@ automatically load the proper tile and resolution depending on the desired domai
     MapboxTiles
     OrdnanceSurvey
     QuadtreeTiles
+    StadiaMapsTiles
     Stamen
 
 Open Geospatial Consortium (OGC)

lib/cartopy/io/img_tiles.py

@@ -320,6 +320,66 @@ def _image_url(self, tile):
         return f'https://a.tile.openstreetmap.org/{z}/{x}/{y}.png'
 
 
+class StadiaMapsTiles(GoogleWTS):
+    """
+    Retrieves tiles from stadiamaps.com.
+
+    For a full reference on the styles available please see
+    https://docs.stadiamaps.com/themes/. A few of the specific styles
+    that are made available are ``alidade_smooth``, ``stamen_terrain`` and
+    ``osm_bright``.
+
+    Using the Stadia Maps API requires including an attribution. Please see
+    https://docs.stadiamaps.com/attribution/ for details.
+
+    For most styles that means including the following attribution:
+
+    `© Stadia Maps <https://www.stadiamaps.com/>`_
+    `© OpenMapTiles <https://openmaptiles.org/>`_
+    `© OpenStreetMap contributors <https://www.openstreetmap.org/about/>`_
+
+    with Stamen styles *additionally* requiring the following attribution:
+
+    `© Stamen Design <https://stamen.com/>`_
+
+    Parameters
+    ----------
+    apikey : str, required
+        The authentication key provided by Stadia Maps to query their APIs
+    style : str, optional
+        Name of the desired style. Defaults to ``alidade_smooth``.
+        See https://docs.stadiamaps.com/themes/ for a full list of styles.
+    resolution : str, optional
+        Resolution of the images to return. Defaults to an empty string,
+        standard resolution (256x256). You can also specify "@2x" for high
+        resolution (512x512) tiles.
+    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.
+    """
+
+    def __init__(self,
+                 apikey,
+                 style="alidade_smooth",
+                 resolution="",
+                 cache=False):
+        super().__init__(cache=cache, desired_tile_form="RGBA")
+        self.apikey = apikey
+        self.style = style
+        self.resolution = resolution
+        if style == "stamen_watercolor":
+            # Known style that has the jpg extension
+            self.extension = "jpg"
+        else:
+            self.extension = "png"
+
+    def _image_url(self, tile):
+        x, y, z = tile
+        return ("http://tiles.stadiamaps.com/tiles/"
+                f"{self.style}/{z}/{x}/{y}{self.resolution}.{self.extension}"
+                f"?api_key={self.apikey}")
+
+
 class Stamen(GoogleWTS):
     """
     Retrieves tiles from maps.stamen.com. Styles include
@@ -351,6 +411,9 @@ class Stamen(GoogleWTS):
 
     def __init__(self, style='toner',
                  desired_tile_form=None, cache=False):
+        warnings.warn("The Stamen styles are no longer served by Stamen and "
+                      "are now served by Stadia Maps. Please use the "
+                      "StadiaMapsTiles class instead.")
 
         # preset layer configuration
         layer_config = {

lib/cartopy/tests/test_img_tiles.py

@@ -214,6 +214,22 @@ def test_mapbox_style_tiles_api_url():
     assert url_str == exp_url
 
 
+@pytest.mark.parametrize("style,extension,resolution", [
+    ("alidade_smooth", "png", ""),
+    ("alidade_smooth", "png", "@2x"),
+    ("stamen_watercolor", "jpg", "")])
+def test_stadia_maps_tiles_api_url(style, extension, resolution):
+    apikey = 'foo'
+    tile = [0, 1, 2]
+    exp_url = ('http://tiles.stadiamaps.com/tiles/'
+               f'{style}/2/0/1{resolution}.{extension}'
+               '?api_key=foo')
+
+    sample = cimgt.StadiaMapsTiles(apikey, style=style, resolution=resolution)
+    url_str = sample._image_url(tile)
+    assert url_str == exp_url
+
+
 def test_ordnance_survey_tile_styles():
     """
     Tests that setting the Ordnance Survey tile style works as expected.