Merge pull request #186 from pnuu/bugfix-invert-dtype-promotion

Fix dtype promotion in channel inversion

trollimage/tests/test_image.py

@@ -1595,8 +1595,8 @@ def test_crude_stretch_integer_data(self, dtype, max_stretch):
         np.testing.assert_allclose(img.data.values, arr.astype(np.float32) / max_stretch, rtol=1e-6)
 
     @pytest.mark.parametrize("dtype", (np.float32, np.float64, float))
-    def test_invert(self, dtype):
-        """Check inversion of the image."""
+    def test_invert_single_parameter(self, dtype):
+        """Check inversion of the image for single inversion parameter."""
         arr = np.arange(75, dtype=dtype).reshape(5, 5, 3) / 75.
         data = xr.DataArray(arr.copy(), dims=['y', 'x', 'bands'],
                             coords={'bands': ['R', 'G', 'B']})
@@ -1608,7 +1608,11 @@ def test_invert(self, dtype):
         assert img.data.dtype == dtype
         assert np.allclose(img.data.values, 1 - arr)
 
-        data = xr.DataArray(arr.copy(), dims=['y', 'x', 'bands'],
+    @pytest.mark.parametrize("dtype", (np.float32, np.float64, float))
+    def test_invert_parameter_for_each_channel(self, dtype):
+        """Check inversion of the image for single inversion parameter."""
+        arr = np.arange(75, dtype=dtype).reshape(5, 5, 3) / 75.
+        data = xr.DataArray(arr, dims=['y', 'x', 'bands'],
                             coords={'bands': ['R', 'G', 'B']})
         img = xrimage.XRImage(data)
 
@@ -1618,6 +1622,7 @@ def test_invert(self, dtype):
         scale = xr.DataArray(np.array([-1, 1, -1]), dims=['bands'],
                              coords={'bands': ['R', 'G', 'B']})
         np.testing.assert_allclose(img.data.values, (data * scale + offset).values)
+        assert img.data.dtype == dtype
 
     @pytest.mark.parametrize("dtype", (np.float32, np.float64, float))
     def test_linear_stretch(self, dtype):

trollimage/xrimage.py

@@ -1132,7 +1132,6 @@ def _check_stretch_value(self, val, kind='min'):
         if val is None:
             non_band_dims = tuple(x for x in self.data.dims if x != 'bands')
             val = getattr(self.data, kind)(dim=non_band_dims)
-
         if isinstance(val, (list, tuple)):
             val = self.xrify_tuples(val)
 
@@ -1302,7 +1301,7 @@ def invert(self, invert=True):
         logger.debug("Applying invert with parameters %s", str(invert))
         if isinstance(invert, (tuple, list)):
             invert = self.xrify_tuples(invert)
-            offset = invert.astype(int)
+            offset = invert.astype(self.data.dtype)
             scale = (-1) ** offset
         elif invert:
             offset = 1