ENH: Simplify creation of Slider widget.

skimage/viewer/plugins/base.py

@@ -1,7 +1,7 @@
 from PyQt4 import QtGui
 
 import matplotlib as mpl
-from skimage.io._plugins.q_color_mixer import IntelligentSlider
+from ..widgets import Slider
 
 
 class Plugin(QtGui.QDialog):
@@ -78,17 +78,17 @@ class Plugin(QtGui.QDialog):
         else:
             return param
 
-    def add_argument(self, name, low, high, callback, **kwargs):
-        name, slider = self.add_slider(name, low, high, callback, **kwargs)
+    def add_argument(self, name, low, high, **kwargs):
+        name, slider = self.add_slider(name, low, high, **kwargs)
         self.arguments.append(slider)
 
-    def add_keyword_argument(self, name, low, high, callback, **kwargs):
-        name, slider = self.add_slider(name, low, high, callback, **kwargs)
+    def add_keyword_argument(self, name, low, high, **kwargs):
+        name, slider = self.add_slider(name, low, high, **kwargs)
         self.keyword_arguments[name] = slider
 
-    def add_slider(self, name, low, high, callback, **kwargs):
-        slider = IntelligentSlider(name, low, high, callback,
-                                   orientation='horizontal', **kwargs)
+    def add_slider(self, name, low, high, **kwargs):
+        slider = Slider(name, low, high, **kwargs)
+        slider.callback = self.caller
         self.layout.addWidget(slider, self.row, 0)
         self.row += 1
         return name.replace(' ', '_'), slider
@@ -110,6 +110,13 @@ class Plugin(QtGui.QDialog):
 
         This should be used in lieu of `figure.canvas.mpl_connect` since this
         function stores call back ids for later clean up.
+
+        Parameters
+        ----------
+        event : str
+            Matplotlib event.
+        callback : function
+            Callback function with a matplotlib Event object as its argument.
         """
         cid = self.image_viewer.connect_event(event, callback)
         self.cids.append(cid)

skimage/viewer/plugins/canny.py

@@ -12,12 +12,9 @@ class CannyPlugin(OverlayPlugin):
         width = kwargs.get('width', 400)
         super(CannyPlugin, self).__init__(image_viewer,
                                           width=width, height=height)
-        self.add_keyword_argument('sigma', 0.005, 0, self.caller,
-                                  update_on='release')
-        self.add_keyword_argument('low_threshold', 0.255, 0, self.caller,
-                                  update_on='release')
-        self.add_keyword_argument('high_threshold', 0.255, 0, self.caller,
-                                  update_on='release')
+        self.add_keyword_argument('sigma', 0, 5, update_on='release')
+        self.add_keyword_argument('low_threshold', 0, 255, update_on='release')
+        self.add_keyword_argument('high_threshold', 0, 255, update_on='release')
         # Call callback so that image is updated to slider values.
         self.caller()
 

skimage/viewer/widgets/__init__.py

@@ -0,0 +1 @@
+from core import *

skimage/viewer/widgets/core.py

@@ -0,0 +1,21 @@
+from skimage.io._plugins.q_color_mixer import IntelligentSlider
+
+class Slider(IntelligentSlider):
+    """Slider widget.
+
+    Parameters
+    ----------
+    name : str
+        Name of slider parameter. If this parameter is passed as a keyword
+        argument, it must match the name of that keyword argument. In addition,
+        this name is displayed as the name of the slider.
+    low, high : float
+        Range of slider values.
+    ptype : {'arg' | 'kwarg' | ...}
+        Parameter
+    """
+    def __init__(self, name, low, high, ptype='kwarg', callback=None, **kwargs):
+        self.ptype = ptype
+        kwargs.setdefault('orientation', 'horizontal')
+        scale = (high - low) / 1000.0
+        super(Slider, self).__init__(name, scale, low, callback, **kwargs)