Merge pull request pytroll#2080 from mherbertson/update-sandwich-comp…

…ositor Ignore alpha when adding luminance in Sandwich compositor
mraspaud · Apr 6, 2022 · fd483d3 · fd483d3
2 parents 683df59 + 0a97b74
commit fd483d3
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Showing 2 changed files with 24 additions and 8 deletions.
diff --git a/satpy/composites/__init__.py b/satpy/composites/__init__.py
@@ -1101,7 +1101,8 @@ def __call__(self, projectables, *args, **kwargs):
 
         # Get the enhanced version of the RGB composite to be sharpened
         rgb_img = enhance2dataset(projectables[1])
-        rgb_img *= luminance
+        # Ignore alpha band when applying luminance
+        rgb_img = rgb_img.where(rgb_img.bands == 'A', rgb_img * luminance)
         return super(SandwichCompositor, self).__call__(rgb_img, *args, **kwargs)
 
 

diff --git a/satpy/tests/test_composites.py b/satpy/tests/test_composites.py
@@ -448,16 +448,25 @@ def test_compositor(self):
         np.testing.assert_allclose(res.data, 0.0, atol=1e-9)
 
 
-class TestSandwichCompositor(unittest.TestCase):
+class TestSandwichCompositor:
     """Test sandwich compositor."""
 
+    # Test RGB and RGBA
+    @pytest.mark.parametrize(
+        "input_shape,bands",
+        [
+            ((3, 2, 2), ['R', 'G', 'B']),
+            ((4, 2, 2), ['R', 'G', 'B', 'A'])
+        ]
+    )
     @mock.patch('satpy.composites.enhance2dataset')
-    def test_compositor(self, e2d):
+    def test_compositor(self, e2d, input_shape, bands):
         """Test luminance sharpening compositor."""
         from satpy.composites import SandwichCompositor
 
-        rgb_arr = da.from_array(np.random.random((3, 2, 2)), chunks=2)
-        rgb = xr.DataArray(rgb_arr, dims=['bands', 'y', 'x'])
+        rgb_arr = da.from_array(np.random.random(input_shape), chunks=2)
+        rgb = xr.DataArray(rgb_arr, dims=['bands', 'y', 'x'],
+                           coords={'bands': bands})
         lum_arr = da.from_array(100 * np.random.random((2, 2)), chunks=2)
         lum = xr.DataArray(lum_arr, dims=['y', 'x'])
 
@@ -467,9 +476,15 @@ def test_compositor(self, e2d):
 
         res = comp([lum, rgb])
 
-        for i in range(3):
-            np.testing.assert_allclose(res.data[i, :, :],
-                                       rgb_arr[i, :, :] * lum_arr / 100.)
+        for band in rgb:
+            if band.bands != 'A':
+                # Check compositor has modified this band
+                np.testing.assert_allclose(res.loc[band.bands].to_numpy(),
+                                           band.to_numpy() * lum_arr / 100.)
+            else:
+                # Check Alpha band remains intact
+                np.testing.assert_allclose(res.loc[band.bands].to_numpy(),
+                                           band.to_numpy())
         # make sure the compositor doesn't modify the input data
         np.testing.assert_allclose(lum.values, lum_arr.compute())