BUG: Fix indexing error when mask_and_scale=True was combined with band dim chunking

docs/history.rst

@@ -3,6 +3,7 @@ History
 
 Latest
 ------
+- BUG: Fix indexing error when `mask_and_scale=True` was combined with band dim chunking (issue #387, pull #388)
 
 0.6.0
 ------

rioxarray/_io.py

@@ -288,11 +288,9 @@ def _getitem(self, key):
                 if self.masked:
                     out = np.ma.filled(out.astype(self.dtype), self.fill_value)
                 if self.mask_and_scale:
-                    for band in np.atleast_1d(band_key):
-                        band_iii = band - 1
-                        out[band_iii] = (
-                            out[band_iii] * riods.scales[band_iii]
-                            + riods.offsets[band_iii]
+                    for iii, band_iii in enumerate(np.atleast_1d(band_key) - 1):
+                        out[iii] = (
+                            out[iii] * riods.scales[band_iii] + riods.offsets[band_iii]
                         )
 
         if squeeze_axis:

test/integration/test_integration__io.py

@@ -682,6 +682,23 @@ def test_chunks():
             assert_allclose(ac, ex)
 
 
+def test_chunks_with_mask_and_scale():
+    with create_tmp_geotiff(
+        10, 10, 4, transform_args=[1, 2, 0.5, 2.0], crs="+proj=latlong"
+    ) as (tmp_file, expected):
+        # Chunk at open time
+        with rioxarray.open_rasterio(
+            tmp_file, mask_and_scale=True, chunks=(1, 2, 2)
+        ) as actual:
+            assert isinstance(actual.data, dask.array.Array)
+            assert "open_rasterio" in actual.data.name
+
+            # do some arithmetic
+            ac = actual.mean().compute()
+            ex = expected.mean()
+            assert_allclose(ac, ex)
+
+
 def test_pickle_rasterio():
     # regression test for https://github.com/pydata/xarray/issues/2121
     with create_tmp_geotiff() as (tmp_file, expected):