Merge ee0da69 into dd80145

continuous_integration/environment.yaml

@@ -60,6 +60,6 @@ dependencies:
   - pip:
     - pytest-lazy-fixtures
     - trollsift
-    - trollimage>=1.23
+    - trollimage>=1.24
     - pyspectral
     - pyorbital

doc/source/enhancements.rst

@@ -100,6 +100,15 @@ the example here::
             - {colors: spectral, min_value: 193.15, max_value: 253.149999}
             - {colors: greys, min_value: 253.15, max_value: 303.15}
 
+In addition, it is also possible to add a linear alpha channel to the colormap, as in the
+following example::
+
+    - name: colorize
+      method: !!python/name:satpy.enhancements.colorize
+      kwargs:
+        palettes:
+        - {colors: ylorrd, min_alpha: 100, max_alpha: 255}
+
 It is also possible to provide your own custom defined color mapping by
 specifying a list of RGB values and the corresponding min and max values
 between which to apply the colors. This is for instance a common use case for

pyproject.toml

@@ -18,7 +18,7 @@ dependencies = [
     "pyproj>=2.2",
     "pyresample>=1.24.0",
     "pyyaml>=5.1",
-    "trollimage>=1.23",
+    "trollimage>=1.24",
     "trollsift",
     "xarray>=0.14.1",
     "zarr",

satpy/composites/glm.py

@@ -50,19 +50,19 @@ def __init__(self, name, min_highlight=0.0, max_highlight=10.0,  # noqa: D417
         Args:
             min_highlight (float): Minimum raw value of the "highlight" data
                 that will be used for linearly scaling the data along with
-                ``max_hightlight``.
+                ``max_highlight``.
             max_highlight (float): Maximum raw value of the "highlight" data
                 that will be used for linearly scaling the data along with
-                ``min_hightlight``.
+                ``min_highlight``.
             max_factor (tuple): Maximum effect that the highlight data can
                 have on each channel of the primary image data. This will be
                 multiplied by the linearly scaled highlight data and then
                 added or subtracted from the highlight channels. See class
                 docstring for more information. By default this is set to
                 ``(0.8, 0.8, -0.8, 0)`` meaning the Red and Green channel
                 will be added to by at most 0.8, the Blue channel will be
-                subtracted from by at most 0.8, and the Alpha channel will
-                not be effected.
+                subtracted from by at most 0.8 (resulting in yellow highlights),
+                and the Alpha channel will not be affected.
 
         """
         self.min_highlight = min_highlight

satpy/enhancements/__init__.py

@@ -409,7 +409,7 @@ def create_colormap(palette, img=None):  # noqa: D417
     Colormaps can be loaded from lists of colors provided by the ``colors``
     key in the provided dictionary. Each element in the list represents a
     single color to be mapped to and can be 3 (RGB) or 4 (RGBA) elements long.
-    By default the value or control point for a color is determined by the
+    By default, the value or control point for a color is determined by the
     index in the list (0, 1, 2, ...) divided by the total number of colors
     to produce a number between 0 and 1. This can be overridden by providing a
     ``values`` key in the provided dictionary. See the "Set Range" section
@@ -455,12 +455,37 @@ def create_colormap(palette, img=None):  # noqa: D417
     ``max_value``. See :meth:`trollimage.colormap.Colormap.set_range` for more
     information.
 
+    **Set Alpha Range**
+
+    The alpha channel of a created colormap can be added and/or modified by
+    specifying ``min_alpha`` and ``max_alpha``.
+    See :meth:`trollimage.colormap.Colormap.set_alpha_range`  for more info.
+
     """
+    # are colors between 0-255 or 0-1
+    color_scale = palette.get("color_scale", 255)
+    cmap = _get_cmap_from_palette_info(palette, img, color_scale)
+
+    if palette.get("reverse", False):
+        cmap.reverse()
+    if "min_value" in palette and "max_value" in palette:
+        cmap.set_range(palette["min_value"], palette["max_value"])
+    elif "min_value" in palette or "max_value" in palette:
+        raise ValueError("Both 'min_value' and 'max_value' must be specified (or neither).")
+
+    if "min_alpha" in palette and "max_alpha" in palette:
+        cmap.set_alpha_range(palette["min_alpha"]/color_scale,
+                             palette["max_alpha"]/color_scale)
+    elif "min_alpha" in palette or "max_alpha" in palette:
+        raise ValueError("Both 'min_alpha' and 'max_alpha' must be specified (or neither).")
+
+    return cmap
+
+
+def _get_cmap_from_palette_info(palette, img, color_scale):
     fname = palette.get("filename", None)
     colors = palette.get("colors", None)
     dataset = palette.get("dataset", None)
-    # are colors between 0-255 or 0-1
-    color_scale = palette.get("color_scale", 255)
     if fname:
         if not os.path.exists(fname):
             fname = get_config_path(fname)
@@ -473,17 +498,10 @@ def create_colormap(palette, img=None):  # noqa: D417
         cmap = _create_colormap_from_dataset(img, dataset, color_scale)
     else:
         raise ValueError("Unknown colormap format: {}".format(palette))
-
-    if palette.get("reverse", False):
-        cmap.reverse()
-    if "min_value" in palette and "max_value" in palette:
-        cmap.set_range(palette["min_value"], palette["max_value"])
-    elif "min_value" in palette or "max_value" in palette:
-        raise ValueError("Both 'min_value' and 'max_value' must be specified (or neither)")
-
     return cmap
 
 
+
 def _create_colormap_from_dataset(img, dataset, color_scale):
     """Create a colormap from an auxiliary variable in a source file."""
     match = find_in_ancillary(img.data, dataset)

satpy/tests/enhancement_tests/test_enhancements.py

@@ -350,6 +350,31 @@ def test_cmap_vrgb_as_rgba(self):
             assert cmap.values[0] == 0
             assert cmap.values[-1] == 1.0
 
+    def test_cmap_with_alpha_set(self):
+        """Test that the min_alpha and max_alpha arguments set the alpha channel correctly."""
+        with closed_named_temp_file(suffix=".npy") as cmap_filename:
+            cmap_data = _generate_cmap_test_data(None, "RGB")
+            np.save(cmap_filename, cmap_data)
+            cmap = create_colormap({"filename": cmap_filename, "min_alpha": 100, "max_alpha": 255})
+            assert cmap.colors.shape[0] == 4
+            assert cmap.colors.shape[1] == 4  # RGBA
+            #check that we start from min_alpha
+            np.testing.assert_equal(cmap.colors[0], [1.0, 0, 0, 100/255.])
+            # two thirds of the linear scale
+            np.testing.assert_almost_equal(cmap.colors[2], [1., 1., 1., (100+(2/3)*(255-100))/255])
+            #check that we end at max_alpha
+            np.testing.assert_equal(cmap.colors[3], [0, 0, 1., 1.0])
+            # check that values have not been changed
+            assert cmap.values.shape[0] == 4
+            assert cmap.values[0] == 0
+            assert cmap.values[-1] == 1.0
+
+            # check that if a value is missing we raise a ValueError
+            with pytest.raises(ValueError, match="Both 'min_alpha' and 'max_alpha' must be specified*."):
+                create_colormap({"filename": cmap_filename, "max_alpha": 255})
+            with pytest.raises(ValueError, match="Both 'min_alpha' and 'max_alpha' must be specified*."):
+                create_colormap({"filename": cmap_filename, "min_alpha": 255})
+
     @pytest.mark.parametrize(
         ("real_mode", "forced_mode"),
         [