Issue #527 add basic band metadata to cubes loaded with load_stac (PR #548)

Author: VincentVerelst

openeo/metadata.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import logging
+import pystac
 import warnings
 from typing import Any, Callable, List, NamedTuple, Optional, Tuple, Union
 
@@ -522,3 +523,63 @@ def _repr_html_(self):
     def __str__(self) -> str:
         bands = self.band_names if self.has_band_dimension() else "no bands dimension"
         return f"CollectionMetadata({self.extent} - {bands} - {self.dimension_names()})"
+
+
+def metadata_from_stac(url: str) -> CubeMetadata:
+    """
+    Reads the band metadata a static STAC catalog or a STAC API Collection and returns it as a :py:class:`CubeMetadata`
+
+    :param url: The URL to a static STAC catalog (STAC Item, STAC Collection, or STAC Catalog) or a specific STAC API Collection
+    :return: A :py:class:`CubeMetadata` containing the DataCube band metadata from the url.
+    """
+
+    def get_band_metadata(eo_bands_location: dict) -> List[Band]:
+        return [
+            Band(name=band["name"], common_name=band.get("common_name"), wavelength_um=band.get("center_wavelength"))
+            for band in eo_bands_location.get("eo:bands", [])
+        ]
+
+    def get_band_names(bands: List[Band]) -> List[str]:
+        return [band.name for band in bands]
+
+    def is_band_asset(asset: pystac.Asset) -> bool:
+        return "eo:bands" in asset.extra_fields
+
+    stac_object = pystac.read_file(href=url)
+
+    bands = []
+    collection = None
+
+    if isinstance(stac_object, pystac.Item):
+        item = stac_object
+        if "eo:bands" in item.properties:
+            eo_bands_location = item.properties
+        elif item.get_collection() is not None:
+            collection = item.get_collection()
+            eo_bands_location = item.get_collection().summaries.lists
+        else:
+            eo_bands_location = {}
+        bands = get_band_metadata(eo_bands_location)
+
+    elif isinstance(stac_object, pystac.Collection):
+        collection = stac_object
+        bands = get_band_metadata(collection.summaries.lists)
+
+        # Summaries is not a required field in a STAC collection, so also check the assets
+        for itm in collection.get_items():
+            band_assets = {asset_id: asset for asset_id, asset in itm.get_assets().items() if is_band_asset(asset)}
+
+            for asset in band_assets.values():
+                asset_bands = get_band_metadata(asset.extra_fields)
+                for asset_band in asset_bands:
+                    if asset_band.name not in get_band_names(bands):
+                        bands.append(asset_band)
+
+    else:
+        assert isinstance(stac_object, pystac.Catalog)
+        catalog = stac_object
+        bands = get_band_metadata(catalog.extra_fields.get("summaries", {}))
+
+    band_dimension = BandDimension(name="bands", bands=bands)
+    metadata = CubeMetadata(dimensions=[band_dimension])
+    return metadata

openeo/rest/connection.py

@@ -27,7 +27,14 @@
 from openeo.internal.jupyter import VisualDict, VisualList
 from openeo.internal.processes.builder import ProcessBuilderBase
 from openeo.internal.warnings import deprecated, legacy_alias
-from openeo.metadata import Band, BandDimension, CollectionMetadata, SpatialDimension, TemporalDimension
+from openeo.metadata import (
+    Band,
+    BandDimension,
+    CollectionMetadata,
+    SpatialDimension,
+    TemporalDimension,
+    metadata_from_stac,
+)
 from openeo.rest import (
     CapabilitiesException,
     OpenEoApiError,
@@ -1361,6 +1368,10 @@ def load_stac(
                 prop: build_child_callback(pred, parent_parameters=["value"]) for prop, pred in properties.items()
             }
         cube = self.datacube_from_process(process_id="load_stac", **arguments)
+        try:
+            cube.metadata = metadata_from_stac(url)
+        except Exception:
+            _log.warning(f"Failed to extract cube metadata from STAC URL {url}", exc_info=True)
         return cube
 
     def load_ml_model(self, id: Union[str, BatchJob]) -> MlModel:

setup.py

@@ -73,6 +73,7 @@
         "numpy>=1.17.0",
         "xarray>=0.12.3",
         "pandas>0.20.0",
+        "pystac",
         "deprecated>=1.2.12",
         'oschmod>=0.3.12; sys_platform == "win32"',
         "importlib_resources; python_version<'3.9'",

tests/test_metadata.py

@@ -2,6 +2,7 @@
 
 from typing import List
 
+import json
 import pytest
 
 from openeo.metadata import (
@@ -14,6 +15,7 @@
     MetadataException,
     SpatialDimension,
     TemporalDimension,
+    metadata_from_stac,
 )
 
 
@@ -782,3 +784,57 @@ def filter_bbox(self, bbox):
     assert isinstance(new, MyCubeMetadata)
     assert orig.bbox is None
     assert new.bbox == (1, 2, 3, 4)
+
+
+@pytest.mark.parametrize(
+    "test_stac, expected",
+    [
+        (
+            {
+                "type": "Collection",
+                "id": "test-collection",
+                "stac_version": "1.0.0",
+                "description": "Test collection",
+                "links": [],
+                "title": "Test Collection",
+                "extent": {
+                    "spatial": {"bbox": [[-180.0, -90.0, 180.0, 90.0]]},
+                    "temporal": {"interval": [["2020-01-01T00:00:00Z", "2020-01-10T00:00:00Z"]]},
+                },
+                "license": "proprietary",
+                "summaries": {"eo:bands": [{"name": "B01"}, {"name": "B02"}]},
+            },
+            ["B01", "B02"],
+        ),
+        (
+            {
+                "type": "Catalog",
+                "id": "test-catalog",
+                "stac_version": "1.0.0",
+                "description": "Test Catalog",
+                "links": [],
+            },
+            [],
+        ),
+        (
+            {
+                "type": "Feature",
+                "stac_version": "1.0.0",
+                "id": "test-item",
+                "properties": {"datetime": "2020-05-22T00:00:00Z", "eo:bands": [{"name": "SCL"}, {"name": "B08"}]},
+                "geometry": {"coordinates": [[[0, 0], [0, 1], [1, 1], [1, 0], [0, 0]]], "type": "Polygon"},
+                "links": [],
+                "assets": {},
+                "bbox": [0, 1, 0, 1],
+                "stac_extensions": [],
+            },
+            ["SCL", "B08"],
+        ),
+    ],
+)
+def test_metadata_from_stac(tmp_path, test_stac, expected):
+
+    path = tmp_path / "stac.json"
+    path.write_text(json.dumps(test_stac))
+    metadata = metadata_from_stac(path)
+    assert metadata.band_names == expected