example with interactive exploration of properties obtained with regi…

…onprops (#5010)

* example with interactive exploration of properties obtained with regionprops

* Update doc/examples/segmentation/plot_regionprops.py

doc/examples/segmentation/plot_regionprops.py

@@ -4,8 +4,8 @@
 =========================
 
 This example shows how to measure properties of labelled image regions. We
-analyze an image with two ellipses.
-
+first analyze an image with two ellipses. Below we show how to explore
+interactively the properties of labelled objects.
 """
 import math
 import matplotlib.pyplot as plt
@@ -76,3 +76,43 @@
 # dict.
 
 pd.DataFrame(props)
+
+#####################################################################
+# It is also possible to explore interactively the properties of labelled
+# objects by visualizing them in the hover information of the labels.
+# This example uses plotly in order to display properties when
+# hovering over the objects.
+
+import plotly.express as px
+import plotly.graph_objects as go
+from skimage import data, filters, measure, morphology
+
+img = data.coins()
+# Binary image, post-process the binary mask and compute labels
+threshold = filters.threshold_otsu(img)
+mask = img > threshold
+mask = morphology.remove_small_objects(mask, 50)
+mask = morphology.remove_small_holes(mask, 50)
+labels = measure.label(mask)
+
+fig = px.imshow(img, binary_string=True)
+fig.update_traces(hoverinfo='skip') # hover is only for label info
+
+props = measure.regionprops(labels, img)
+properties = ['area', 'eccentricity', 'perimeter', 'mean_intensity']
+
+# For each label, add a filled scatter trace for its contour,
+# and display the properties of the label in the hover of this trace.
+for index in range(1, labels.max()):
+    label = props[index].label
+    contour = measure.find_contours(labels == label, 0.5)[0]
+    y, x = contour.T
+    hoverinfo = ''
+    for prop_name in properties:
+        hoverinfo += f'<b>{prop_name}: {getattr(props[index], prop_name):.2f}</b><br>'
+    fig.add_trace(go.Scatter(
+        x=x, y=y, name=label,
+        mode='lines', fill='toself', showlegend=False,
+        hovertemplate=hoverinfo, hoveron='points+fills'))
+
+fig

doc/source/conf.py

@@ -149,6 +149,9 @@
     major, minor = v.release[:2]
     binder_branch = 'v{}.{}.x'.format(major, minor)
 
+# set plotly renderer to capture _repr_html_ for sphinx-gallery
+import plotly.io as pio
+pio.renderers.default = 'sphinx_gallery'
 
 sphinx_gallery_conf = {
     'doc_module': ('skimage',),

requirements/docs.txt

@@ -14,3 +14,4 @@ pooch>=0.5.2
 tifffile>=2020.5.30
 myst-parser
 ipywidgets
+plotly>=4.8.0