diff --git a/skimage/viewer/canvastools/base.py b/skimage/viewer/canvastools/base.py
index 68f84726..e73dcf24 100644
--- a/skimage/viewer/canvastools/base.py
+++ b/skimage/viewer/canvastools/base.py
@@ -12,7 +12,7 @@ class CanvasToolBase(object):
     Parameters
     ----------
     """
-    def __init__(self, ax, useblit=None):
+    def __init__(self, ax, useblit=None, on_update=None, on_enter=None):
         self.ax = ax
         self.canvas = ax.figure.canvas
         self.cids = []
@@ -26,6 +26,14 @@ class CanvasToolBase(object):
             self.canvas.draw()
             self.img_background = self.canvas.copy_from_bbox(self.ax.bbox)
 
+        if on_update is None:
+            on_update = lambda *args: None
+        self.on_update = on_update
+
+        if on_enter is None:
+            on_enter = lambda *args: None
+        self.on_enter = on_enter
+
     def connect_event(self, event, callback):
         """Connect callback with an event.
 
@@ -52,6 +60,15 @@ class CanvasToolBase(object):
         for a in self._artists:
             a.set_visible(val)
 
+    def redraw(self):
+        if self.useblit:
+            self.canvas.restore_region(self.img_background)
+            for artist in self._artists:
+                self.ax.draw_artist(artist)
+            self.canvas.blit(self.ax.bbox)
+        else:
+            self.canvas.draw_idle()
+
 
 class ToolHandles(object):
     """Control handles for canvas tools.
diff --git a/skimage/viewer/canvastools/line_tool.py b/skimage/viewer/canvastools/line_tool.py
index 8f1cd25a..c9e4f420 100644
--- a/skimage/viewer/canvastools/line_tool.py
+++ b/skimage/viewer/canvastools/line_tool.py
@@ -21,7 +21,8 @@ class LineTool(CanvasToolBase):
     """
     def __init__(self, ax, x, y, on_update=None, on_enter=None, maxdist=10,
                  lineprops=None):
-        super(LineTool, self).__init__(ax)
+        super(LineTool, self).__init__(ax, on_update=on_update,
+                                       on_enter=on_enter)
 
         props = dict(color='r', linewidth=1, alpha=0.4, solid_capstyle='butt')
         props.update(lineprops if lineprops is not None else {})
@@ -29,14 +30,6 @@ class LineTool(CanvasToolBase):
         self.maxdist = maxdist
         self._active_pt = None
 
-        if on_update is None:
-            on_update = lambda *args: None
-        self.on_update = on_update
-
-        if on_enter is None:
-            on_enter = lambda *args: None
-        self.on_enter = on_enter
-
         self._init_end_pts = np.transpose([x, y])
         self.end_pts = self._init_end_pts.copy()
 
@@ -100,15 +93,6 @@ class LineTool(CanvasToolBase):
 
         self.on_update(self.end_pts)
 
-    def redraw(self):
-        if self.useblit:
-            self.canvas.restore_region(self.img_background)
-            for artist in self._artists:
-                self.ax.draw_artist(artist)
-            self.canvas.blit(self.ax.bbox)
-        else:
-            self.canvas.draw_idle()
-
 
 class ThickLineTool(LineTool):