RasterDataset: add control over resampling algorithm

docs/tutorials/custom_raster_dataset.ipynb

@@ -336,6 +336,10 @@
     "\n",
     "Defaults to float32 for `is_image == True` and long for `is_image == False`. This is what you want for 99% of datasets, but can be overridden for tasks like pixel-wise regression (where the target mask should be float32).\n",
     "\n",
+    "### `resampling`\n",
+    "\n",
+    "Defaults to bilinear for float Tensors and nearest for int Tensors. Can be overridden for custom resampling algorithms.\n",
+    "\n",
     "### `separate_files`\n",
     "\n",
     "If your data comes with each spectral band in a separate files, as is the case with Sentinel-2, use `separate_files = True`. If all spectral bands are stored in a single file, use `separate_files = False` instead.\n",

tests/datasets/test_geo.py

@@ -5,12 +5,14 @@
 import sys
 from collections.abc import Iterable
 from pathlib import Path
+from typing import Any
 
 import pytest
 import torch
 import torch.nn as nn
 from _pytest.fixtures import SubRequest
 from rasterio.crs import CRS
+from rasterio.enums import Resampling
 from torch.utils.data import ConcatDataset
 
 from torchgeo.datasets import (
@@ -49,6 +51,16 @@ def __getitem__(self, query: BoundingBox) -> dict[str, BoundingBox]:
         return {'index': bounds}
 
 
+class CustomRasterDataset(RasterDataset):
+    def __init__(self, dtype: torch.dtype, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
+        self._dtype = dtype
+
+    @property
+    def dtype(self) -> torch.dtype:
+        return self._dtype
+
+
 class CustomVectorDataset(VectorDataset):
     filename_glob = '*.geojson'
     date_format = '%Y'
@@ -274,6 +286,22 @@ def test_getitem_uint_dtype(self, dtype: str) -> None:
         assert isinstance(x['image'], torch.Tensor)
         assert x['image'].dtype == torch.float32
 
+    @pytest.mark.parametrize('dtype', [torch.float, torch.double])
+    def test_resampling_float_dtype(self, dtype: torch.dtype) -> None:
+        paths = os.path.join('tests', 'data', 'raster', 'uint16')
+        ds = CustomRasterDataset(dtype, paths)
+        x = ds[ds.bounds]
+        assert x['image'].dtype == dtype
+        assert ds.resampling == Resampling.bilinear
+
+    @pytest.mark.parametrize('dtype', [torch.long, torch.bool])
+    def test_resampling_int_dtype(self, dtype: torch.dtype) -> None:
+        paths = os.path.join('tests', 'data', 'raster', 'uint16')
+        ds = CustomRasterDataset(dtype, paths)
+        x = ds[ds.bounds]
+        assert x['image'].dtype == dtype
+        assert ds.resampling == Resampling.nearest
+
     def test_invalid_query(self, sentinel: Sentinel2) -> None:
         query = BoundingBox(0, 0, 0, 0, 0, 0)
         with pytest.raises(

torchgeo/datasets/geo.py

@@ -22,6 +22,7 @@
 import shapely
 import torch
 from rasterio.crs import CRS
+from rasterio.enums import Resampling
 from rasterio.io import DatasetReader
 from rasterio.vrt import WarpedVRT
 from rtree.index import Index, Property
@@ -309,7 +310,7 @@ def files(self) -> list[str]:
                 files |= set(glob.iglob(pathname, recursive=True))
             elif os.path.isfile(path) or path_is_vsi(path):
                 files.add(path)
-            elif not hasattr(self, "download"):
+            elif not hasattr(self, 'download'):
                 warnings.warn(
                     f"Could not find any relevant files for provided path '{path}'. "
                     f'Path was ignored.',
@@ -384,6 +385,23 @@ def dtype(self) -> torch.dtype:
         else:
             return torch.long
 
+    @property
+    def resampling(self) -> Resampling:
+        """Resampling algorithm used when reading input files.
+
+        Defaults to bilinear for float dtypes and nearest for int dtypes.
+
+        Returns:
+            The resampling method to use.
+
+        .. versionadded:: 0.6
+        """
+        # Based on torch.is_floating_point
+        if self.dtype in [torch.float64, torch.float32, torch.float16, torch.bfloat16]:
+            return Resampling.bilinear
+        else:
+            return Resampling.nearest
+
     def __init__(
         self,
         paths: str | Iterable[str] = 'data',
@@ -555,7 +573,9 @@ def _merge_files(
             vrt_fhs = [self._load_warp_file(fp) for fp in filepaths]
 
         bounds = (query.minx, query.miny, query.maxx, query.maxy)
-        dest, _ = rasterio.merge.merge(vrt_fhs, bounds, self.res, indexes=band_indexes)
+        dest, _ = rasterio.merge.merge(
+            vrt_fhs, bounds, self.res, indexes=band_indexes, resampling=self.resampling
+        )
         # Use array_to_tensor since merge may return uint16/uint32 arrays.
         tensor = array_to_tensor(dest)
         return tensor