Merge pull request #1314 from SalvatoreScaramuzzino/RectTool_docs

Rect tool docs

CONTRIBUTORS.txt

@@ -200,3 +200,6 @@
 
 - Matěj Týč
   Extended the image labelling implementation so it also works on 3D images.
+
+- Salvatore Scaramuzzino
+  RectTool example

skimage/viewer/canvastools/recttool.py

@@ -37,8 +37,35 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
     ----------
     extents : tuple
         Rectangle extents: (xmin, xmax, ymin, ymax).
-    """
+    
+    Examples
+    ----------
+    >>> from skimage import data
+    >>> from skimage.viewer import ImageViewer
+    >>> from skimage.viewer.canvastools import RectangleTool
+    >>> from skimage.draw import line
+    >>> from skimage.draw import set_color
+ 
+    >>> viewer = ImageViewer(data.coffee())  # doctest: +SKIP
 
+    >>> def print_the_rect(extents):
+    ...     global viewer
+    ...     im = viewer.image    
+    ...     coord = np.int64(extents)
+    ...     [rr1, cc1] = line(coord[2],coord[0],coord[2],coord[1])
+    ...     [rr2, cc2] = line(coord[2],coord[1],coord[3],coord[1])
+    ...     [rr3, cc3] = line(coord[3],coord[1],coord[3],coord[0])
+    ...     [rr4, cc4] = line(coord[3],coord[0],coord[2],coord[0])
+    ...     set_color(im, (rr1, cc1), [255, 255, 0])
+    ...     set_color(im, (rr2, cc2), [0, 255, 255])
+    ...     set_color(im, (rr3, cc3), [255, 0, 255])
+    ...     set_color(im, (rr4, cc4), [0, 0, 0])
+    ...     viewer.image=im
+    
+    >>> rect_tool = RectangleTool(viewer.ax, on_enter=print_the_rect) # doctest: +SKIP
+    >>> viewer.show() # doctest: +SKIP
+    """
+    
     def __init__(self, viewer, on_move=None, on_release=None, on_enter=None,
                  maxdist=10, rect_props=None):
         self._rect = None