add random colormap for visualizing image segmentation in imviz

jdaviz/configs/default/plugins/plot_options/plot_options.py

@@ -36,16 +36,27 @@
 
 def _register_random_cmap(
     cmap_name,
-    background_color=[0, 0, 0],
-    background_alpha=0,
+    bkg_color=[0, 0, 0],
+    bkg_alpha=1,
     seed=42,
     ncolors=10_000
 ):
+    """
+    Custom random colormap, useful for rendering image
+    segmentation maps. The default background for
+    `label==0` is *transparent*. If the segmentation map
+    contains more than 10,000 labels, adjust the `ncolors`
+    kwarg to ensure uniqueness.
+    """
     cmap = make_random_cmap(ncolors=ncolors, seed=seed)
-    cmap.colors[0] = background_color + [background_alpha]
+    cmap.colors[0] = bkg_color + [bkg_alpha]
+    cmap.name = cmap_name
     colormaps.add(cmap_name, cmap)
 
 
+_register_random_cmap('Random', bkg_alpha=1)
+
+
 class SplineStretch:
     """
     A class to represent spline stretches.
@@ -1100,3 +1111,13 @@ def _is_image_viewer(viewer):
             viewers = [viewers]
 
         return np.all([_is_image_viewer(viewer) for viewer in viewers])
+
+    @observe('image_colormap_value')
+    def _random_cmap_limit_update(self, *args, **kwargs):
+        # if 'Random' colormap is used for visualizing image segmentation,
+        # ensure the stretch limits are the min and max, so all label colors
+        # are unique:
+        if self.image_colormap_value != 'Random':
+            return
+
+        self.stretch_preset.value = 100

jdaviz/configs/default/plugins/plot_options/tests/test_plot_options.py

@@ -391,3 +391,25 @@ def test_track_mixed_states(imviz_helper):
     assert not po.stretch_function_sync['mixed']
     assert po.stretch_function_value == 'spline'
     assert not po.stretch_params_sync['mixed']
+
+
+def test_segmentation_image(imviz_helper):
+    # Make one circular segment for a hypothetical
+    # image with one source:
+    nx = ny = 100
+    radius = 15
+    x0 = y0 = 50
+
+    segmentation_map = np.zeros((nx, ny))
+    xx, yy = np.meshgrid(np.arange(nx), np.arange(ny))
+    in_circle = np.hypot(xx - x0, yy - y0) < radius
+    segmentation_map[in_circle] = 1
+
+    imviz_helper.load_data(segmentation_map)
+
+    plot_opts = imviz_helper.plugins['Plot Options']
+    plot_opts.image_colormap = 'Random'
+
+    # ensure that stretch preset is listening to the update to the
+    # random colormap so that all colors are uniquely displayed:
+    assert plot_opts.stretch_preset.value == 100

jdaviz/configs/imviz/tests/test_astrowidgets_api.py

@@ -180,7 +180,7 @@ def test_colormap_options(self):
             'Gray', 'Viridis', 'Plasma', 'Inferno', 'Magma', 'Purple-Blue',
             'Yellow-Green-Blue', 'Yellow-Orange-Red', 'Red-Purple', 'Blue-Green',
             'Hot', 'Red-Blue', 'Red-Yellow-Blue', 'Purple-Orange', 'Purple-Green',
-            'Rainbow', 'Seismic',
+            'Random', 'Rainbow', 'Seismic',
             'Reversed: Gray', 'Reversed: Viridis', 'Reversed: Plasma', 'Reversed: Inferno',
             'Reversed: Magma', 'Reversed: Hot', 'Reversed: Rainbow']