VectorDataset: fix issue with empty query (microsoft#467)

* VectorDataset: fix issue with empty query

* isort

tests/data/vector/data.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
+
+import json
+
+# Create an L shape:
+#
+# +--+
+# |  |
+# +--+--+
+# |  |  |
+# +--+--+
+#
+# This allows us to test queries:
+#
+# * within the L
+# * within the dataset bounding box but with no features
+# * outside the dataset bounding box
+
+geojson = {
+    "type": "FeatureCollection",
+    "crs": {"type": "name", "properties": {"name": "urn:ogc:def:crs:OGC:1.3:CRS84"}},
+    "features": [
+        {
+            "type": "Feature",
+            "properties": {},
+            "geometry": {
+                "type": "Polygon",
+                "coordinates": [
+                    [[0.0, 0.0], [0.0, 1.0], [1.0, 1.0], [1.0, 0.0], [0.0, 0.0]]
+                ],
+            },
+        },
+        {
+            "type": "Feature",
+            "properties": {},
+            "geometry": {
+                "type": "Polygon",
+                "coordinates": [
+                    [[1.0, 0.0], [1.0, 1.0], [2.0, 1.0], [2.0, 0.0], [1.0, 0.0]]
+                ],
+            },
+        },
+        {
+            "type": "Feature",
+            "properties": {},
+            "geometry": {
+                "type": "Polygon",
+                "coordinates": [
+                    [[0.0, 1.0], [0.0, 2.0], [1.0, 2.0], [1.0, 1.0], [0.0, 1.0]]
+                ],
+            },
+        },
+    ],
+}
+
+with open("vector.geojson", "w") as f:
+    json.dump(geojson, f)

tests/data/vector/vector.geojson

@@ -0,0 +1 @@
+{"type": "FeatureCollection", "crs": {"type": "name", "properties": {"name": "urn:ogc:def:crs:OGC:1.3:CRS84"}}, "features": [{"type": "Feature", "properties": {}, "geometry": {"type": "Polygon", "coordinates": [[[0.0, 0.0], [0.0, 1.0], [1.0, 1.0], [1.0, 0.0], [0.0, 0.0]]]}}, {"type": "Feature", "properties": {}, "geometry": {"type": "Polygon", "coordinates": [[[1.0, 0.0], [1.0, 1.0], [2.0, 1.0], [2.0, 0.0], [1.0, 0.0]]]}}, {"type": "Feature", "properties": {}, "geometry": {"type": "Polygon", "coordinates": [[[0.0, 1.0], [0.0, 2.0], [1.0, 2.0], [1.0, 1.0], [0.0, 1.0]]]}}]}

tests/datasets/test_geo.py

@@ -16,7 +16,6 @@
 from torchgeo.datasets import (
     NAIP,
     BoundingBox,
-    CanadianBuildingFootprints,
     GeoDataset,
     IntersectionDataset,
     RasterDataset,
@@ -44,6 +43,10 @@ def __getitem__(self, query: BoundingBox) -> Dict[str, BoundingBox]:
         return {"index": query}
 
 
+class CustomVectorDataset(VectorDataset):
+    filename_glob = "*.geojson"
+
+
 class CustomVisionDataset(VisionDataset):
     def __getitem__(self, index: int) -> Dict[str, int]:
         return {"index": index}
@@ -201,20 +204,25 @@ def test_plot_with_cmap(self, custom_dtype_ds: RasterDataset) -> None:
 
 
 class TestVectorDataset:
-    @pytest.fixture
-    def dataset(self) -> CanadianBuildingFootprints:
-        root = os.path.join("tests", "data", "cbf")
+    @pytest.fixture(scope="class")
+    def dataset(self) -> CustomVectorDataset:
+        root = os.path.join("tests", "data", "vector")
         transforms = nn.Identity()  # type: ignore[no-untyped-call]
-        return CanadianBuildingFootprints(root, res=0.1, transforms=transforms)
+        return CustomVectorDataset(root, res=0.1, transforms=transforms)
 
-    def test_getitem(self, dataset: CanadianBuildingFootprints) -> None:
+    def test_getitem(self, dataset: CustomVectorDataset) -> None:
         x = dataset[dataset.bounds]
         assert isinstance(x, dict)
         assert isinstance(x["crs"], CRS)
         assert isinstance(x["mask"], torch.Tensor)
 
-    def test_invalid_query(self, dataset: CanadianBuildingFootprints) -> None:
-        query = BoundingBox(2, 2, 2, 2, 2, 2)
+    def test_empty_shapes(self, dataset: CustomVectorDataset) -> None:
+        query = BoundingBox(1.1, 1.9, 1.1, 1.9, 0, 0)
+        x = dataset[query]
+        assert torch.equal(x["mask"], torch.zeros(7, 7, dtype=torch.uint8))
+
+    def test_invalid_query(self, dataset: CustomVectorDataset) -> None:
+        query = BoundingBox(3, 3, 3, 3, 0, 0)
         with pytest.raises(
             IndexError, match="query: .* not found in index with bounds:"
         ):

torchgeo/datasets/geo.py

@@ -661,9 +661,14 @@ def __getitem__(self, query: BoundingBox) -> Dict[str, Any]:
         transform = rasterio.transform.from_bounds(
             query.minx, query.miny, query.maxx, query.maxy, width, height
         )
-        masks = rasterio.features.rasterize(
-            shapes, out_shape=(int(height), int(width)), transform=transform
-        )
+        if shapes:
+            masks = rasterio.features.rasterize(
+                shapes, out_shape=(int(height), int(width)), transform=transform
+            )
+        else:
+            # If no features are found in this query, return an empty mask
+            # with the default fill value and dtype used by rasterize
+            masks = np.zeros((int(height), int(width)), dtype=np.uint8)
 
         sample = {"mask": torch.tensor(masks), "crs": self.crs, "bbox": query}