Add resampling

rasterio/merge.py

@@ -629,7 +629,9 @@ def virtual_merge(
                 src.indexes, src.colorinterp, src.block_shapes, src.dtypes
             ):
                 vrtrasterband = vrtdataset.find(f"VRTRasterBand[@band='{bidx}']")
-                complexsource = ET.SubElement(vrtrasterband, "ComplexSource")
+                complexsource = ET.SubElement(
+                    vrtrasterband, "ComplexSource", resampling=resampling.name
+                )
                 ET.SubElement(
                     complexsource, "SourceFilename", relativeToVRT="0", shared="0"
                 ).text = _parse_path(src.name).as_vsi()
@@ -685,7 +687,9 @@ def virtual_merge(
                 for bidx, ci, block_shape, dtype in zip(
                     src.indexes, src.colorinterp, src.block_shapes, src.dtypes
                 ):
-                    simplesource = ET.SubElement(vrtrasterband, "SimpleSource")
+                    simplesource = ET.SubElement(
+                        vrtrasterband, "SimpleSource", resampling=resampling.name
+                    )
                     ET.SubElement(
                         simplesource, "SourceFilename", relativeToVRT="0", shared="0"
                     ).text = _parse_path(src.name).as_vsi()

tests/test_merge.py

@@ -1,6 +1,7 @@
 """Tests of rasterio.merge"""
 
 from glob import glob
+from xml.etree import ElementTree as ET
 
 import boto3
 from hypothesis import given, settings
@@ -11,6 +12,7 @@ import pytest
 import affine
 import rasterio
 from rasterio.crs import CRS
+from rasterio.enums import Resampling
 from rasterio.errors import RasterioError
 from rasterio.merge import merge, virtual_merge
 
@@ -128,6 +130,8 @@ def test_issue2202(dx, dy):
 def test_virtual_merge(tmp_path):
     """Test."""
     xml = virtual_merge(glob("tests/data/rgb?.tif"))
+    assert b'resampling="nearest"' in xml
+
     tmp_path.joinpath("test.vrt").write_bytes(xml)
     with rasterio.open(tmp_path.joinpath("test.vrt")) as dataset:
         rgb = dataset.read()
@@ -135,3 +139,18 @@ def test_virtual_merge(tmp_path):
     import matplotlib.pyplot as plt
     plt.imshow(numpy.moveaxis(rgb, 0, -1))
     plt.savefig("test_virtual_merge.png")
+
+
+@pytest.mark.parametrize("resampling", [Resampling.nearest, Resampling.bilinear])
+def test_virtual_merge_resampling(tmp_path, resampling):
+    """Test."""
+    xml = virtual_merge(glob("tests/data/rgb?.tif"), resampling=resampling)
+    root = ET.fromstring(xml)
+    assert all(
+        elem.attrib["resampling"] == resampling.name
+        for elem in root.findall(".//ComplexSource")
+    )
+    assert all(
+        elem.attrib["resampling"] == resampling.name
+        for elem in root.findall(".//SimpleSource")
+    )