ENH: Allow Save buttons to save overlay

Closes Github #264

skimage/viewer/plugins/base.py

@@ -165,6 +165,11 @@ class Plugin(QDialog):
         # If param is a widget, return its `val` attribute.
         return param if not hasattr(param, 'val') else param.val
 
+    @property
+    def filtered_image(self):
+        """Return filtered image."""
+        return self.image_viewer.image
+
     def display_filtered_image(self, image):
         """Display the filtered image on image viewer.
 

skimage/viewer/plugins/overlayplugin.py

@@ -74,6 +74,14 @@ class OverlayPlugin(Plugin):
             self._overlay_plot.set_cmap(self.cmap)
         self.image_viewer.redraw()
 
+    @property
+    def filtered_image(self):
+        """Return filtered image.
+
+        This "filtered image" is used when saving from the plugin.
+        """
+        return self.overlay
+
     def display_filtered_image(self, image):
         """Display filtered image as an overlay on top of image in viewer."""
         self.overlay = image

skimage/viewer/widgets/history.py

@@ -6,6 +6,9 @@ try:
 except ImportError:
     print("Could not import PyQt4 -- skimage.viewer not available.")
 
+import numpy as np
+
+import skimage
 from skimage import io
 from .core import BaseWidget
 
@@ -84,7 +87,11 @@ class SaveButtons(BaseWidget):
         basename, ext = os.path.splitext(filename)
         if not ext:
             filename = '%s.%s' % (filename, self.default_format)
-        io.imsave(filename, self.plugin.image_viewer.image)
+        image = self.plugin.filtered_image
+        if image.dtype == np.bool:
+            #TODO: This check/conversion should probably be in `imsave`.
+            image = skimage.img_as_ubyte(image)
+        io.imsave(filename, image)
 
 
 def notify(msg):