OGC API - Coverages: add full support for scaling

scale-size and scale-axes are now supported in addition to the
previously supported scale-factor. The recently added CoverageScaling
class is used for the implementation.

test/webapi/ows/coverages/test_controllers.py

@@ -76,7 +76,7 @@ def test_get_coverage_data_netcdf(self):
             'bbox': ['1,51,2,52'],
             'datetime': ['2017-01-24T00:00:00Z/2017-01-27T00:00:00Z'],
             'properties': ['conc_chl,kd489'],
-            'scale-factor': [2],
+            'scale-axes': ['lat(2),lon(2)'],
             'crs': [crs],
         }
         content, content_bbox, content_crs = get_coverage_data(
@@ -170,7 +170,7 @@ def test_get_coverage_data_png(self):
         query = {
             'subset': ['lat(52:51),lon(1:2),time(2017-01-25)'],
             'properties': ['conc_chl'],
-            'scale-factor': ['4'],
+            'scale-size': ['lat(100),lon(100)'],
         }
         content, content_bbox, content_crs = get_coverage_data(
             get_coverages_ctx().datasets_ctx, 'demo', query, 'png'
@@ -262,24 +262,6 @@ def test_get_crs_from_dataset(self):
         ds = xr.Dataset({'crs': ([], None, {'spatial_ref': '3035'})})
         self.assertEqual('EPSG:3035', get_crs_from_dataset(ds).to_string())
 
-    def test_get_coverage_scale_axes(self):
-        with self.assertRaises(ApiError.NotImplemented):
-            get_coverage_data(
-                get_coverages_ctx().datasets_ctx,
-                'demo',
-                {'scale-axes': ['x(2)']},
-                'application/netcdf',
-            )
-
-    def test_get_coverage_scale_size(self):
-        with self.assertRaises(ApiError.NotImplemented):
-            get_coverage_data(
-                get_coverages_ctx().datasets_ctx,
-                'demo',
-                {'scale-size': ['x(2)']},
-                'application/netcdf',
-            )
-
     def test_dtype_to_opengis_datatype(self):
         expected = [
             (

xcube/webapi/ows/coverages/controllers.py

@@ -33,6 +33,8 @@
 from xcube.util.timeindex import ensure_time_index_compatible
 from xcube.webapi.datasets.context import DatasetsContext
 from xcube.webapi.ows.coverages.request import CoverageRequest
+from xcube.webapi.ows.coverages.scaling import CoverageScaling
+from xcube.webapi.ows.coverages.util import get_h_dim, get_v_dim
 
 
 def get_coverage_as_json(ctx: DatasetsContext, collection_id: str):
@@ -140,27 +142,15 @@ def get_coverage_data(
     _assert_coverage_size_ok(ds, scale_factor)
 
     source_gm = GridMapping.from_dataset(ds, crs=native_crs)
-    target_gm = None
+    target_gm = source_gm
 
     if native_crs != final_crs:
-        target_gm = source_gm.transform(final_crs).to_regular()
-
-    if scale_factor != 1:
-        if target_gm is None:
-            target_gm = source_gm
-        target_gm = target_gm.scale(1. / scale_factor)
-    if request.scale_axes is not None:
-        # TODO implement scale-axes
-        raise ApiError.NotImplemented(
-            'The scale-axes parameter is not yet supported.'
-        )
-    if request.scale_size:
-        # TODO implement scale-size
-        raise ApiError.NotImplemented(
-            'The scale-size parameter is not yet supported.'
-        )
+        target_gm = target_gm.transform(final_crs).to_regular()
 
-    if target_gm is not None:
+    scaling = CoverageScaling(request, final_crs, ds)
+    target_gm = scaling.apply(target_gm)
+
+    if target_gm is not source_gm:
         ds = resample_in_space(ds, source_gm=source_gm, target_gm=target_gm)
 
     # In this case, the transformed native CRS bbox[es] may have been
@@ -421,18 +411,6 @@ def _ensure_bbox_y_ascending(bbox: list, xy_order: bool = True):
         bbox[y0], bbox[y1] = bbox[y1], bbox[y0]
 
 
-def get_h_dim(ds: xr.Dataset):
-    return [
-        d for d in list(map(str, ds.dims)) if d[:3].lower() in {'x', 'lon'}
-    ][0]
-
-
-def get_v_dim(ds: xr.Dataset):
-    return [
-        d for d in list(map(str, ds.dims)) if d[:3].lower() in {'y', 'lat'}
-    ][0]
-
-
 def _correct_inverted_y_range_if_necessary(
     ds: xr.Dataset, axis: str, range_: tuple[float, float]
 ) -> tuple[float, float]:

xcube/webapi/ows/coverages/scaling.py

@@ -23,8 +23,9 @@
 import pyproj
 import xarray as xr
 
+from xcube.core.gridmapping import GridMapping
 from xcube.server.api import ApiError
-from xcube.webapi.ows.coverages.controllers import get_h_dim, get_v_dim
+from xcube.webapi.ows.coverages.util import get_h_dim, get_v_dim
 from xcube.webapi.ows.coverages.request import CoverageRequest
 
 
@@ -120,3 +121,9 @@ def get_axis_from_crs(self, valid_identifiers: set[str]):
             if identifiers & valid_identifiers:
                 return axis.abbrev
         return None
+
+    def apply(self, gm: GridMapping):
+        if self.scale == (1, 1):
+            return gm
+        else:
+            return gm.scale((1 / self.scale[0], 1 / self.scale[1]))

xcube/webapi/ows/coverages/util.py

@@ -0,0 +1,35 @@
+# The MIT License (MIT)
+# Copyright (c) 2023 by the xcube team and contributors
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+# DEALINGS IN THE SOFTWARE.
+
+
+import xarray as xr
+
+
+def get_h_dim(ds: xr.Dataset):
+    return [
+        d for d in list(map(str, ds.dims)) if d[:3].lower() in {'x', 'lon'}
+    ][0]
+
+
+def get_v_dim(ds: xr.Dataset):
+    return [
+        d for d in list(map(str, ds.dims)) if d[:3].lower() in {'y', 'lat'}
+    ][0]