GDALRasterWrapper: Avoid reading nodata mask if unnecessary

isciences · Aug 22, 2024 · 1562ab8 · 1562ab8
1 parent c825d82
commit 1562ab8
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Showing 2 changed files with 24 additions and 2 deletions.
diff --git a/src/gdal_raster_wrapper.cpp b/src/gdal_raster_wrapper.cpp
@@ -169,11 +169,15 @@ GDALRasterWrapper::read_box(const Box& box)
         throw std::runtime_error("Error reading from raster.");
     }
 
+    bool mask_needed = GDALGetMaskFlags(m_band) != GMF_ALL_VALID && GDALGetMaskFlags(m_band) != GMF_NODATA;
+
     if (has_scale || has_offset) {
         apply_scale_and_offset(static_cast<double*>(buffer), cropped_grid.size(), scale, offset);
+        mask_needed = mask_needed || GDALGetMaskFlags(m_band) == GMF_NODATA;
     }
 
-    if (GDALRasterBandH mask = GDALGetMaskBand(m_band)) {
+    if (mask_needed) {
+        GDALRasterBandH mask = GDALGetMaskBand(m_band);
         auto mask_rast = make_raster<std::int8_t>(cropped_grid);
         buffer = mask_rast->data().data();
 

diff --git a/test/test_cli.py b/test/test_cli.py
@@ -107,7 +107,7 @@ def writer(data, *, mask=None, nodata=None, scale=None, offset=None):
             if offset:
                 ds.GetRasterBand(i + 1).SetOffset(offset)
             if mask is not None:
-                ds.GetRasterBand(i + 1).CreateMaskBand(gdal.GMF_ALL_VALID)
+                ds.GetRasterBand(i + 1).CreateMaskBand(gdal.GMF_PER_DATASET)
                 mb = ds.GetRasterBand(i + 1).GetMaskBand()
                 assert mb.WriteArray(mask) == gdal.CE_None
                 del mb
@@ -606,6 +606,24 @@ def test_scale_offset(run, write_raster, write_features):
     assert float(rows[0]["d2m_values"]) == pytest.approx(278.2057, rel=1e-3)
 
 
+def test_scale_offset_nodata(run, write_raster, write_features):
+
+    data = np.array([[1, 2, 3], [-999, -999, -999], [4, 5, 6]], dtype=np.int32)
+
+    rows = run(
+        polygons=write_features(
+            {"id": 1, "geom": "POLYGON ((0.5 0.5, 2.5 0.5, 2.5 2.5, 0.5 2.5, 0.5 0.5))"}
+        ),
+        fid="id",
+        raster=f"{write_raster(data, scale=2, offset=-1, nodata=-999)}",
+        stat=["values"],
+        nested_output=True,
+    )
+
+    values = np.fromstring(rows[0]["values"].strip("[").strip("]"), sep=",")
+    np.testing.assert_array_equal(values, [1, 3, 5, 7, 9, 11])
+
+
 def test_id_rename(run, write_raster, write_features):
 
     data = np.array([[1, 2, 3, 4], [1, 2, 2, 5], [3, 3, 3, 2]], np.int16)