matplotlib · tacaswell · May 24, 2015 · Jan 9, 2015 · Jan 9, 2015 · Jan 10, 2015
diff --git a/doc/users/whats_new/2015-01-19_cursor_pixel_data.rst b/doc/users/whats_new/2015-01-19_cursor_pixel_data.rst
@@ -0,0 +1,6 @@
+Allow Artists to Display Pixel Data in Cursor
+---------------------------------------------
+
+Adds `get_pixel_data` and `format_pixel_data` methods to artists
+which can be used to add zdata to the cursor display
+in the status bar.  Also adds an implementation for Images.
diff --git a/lib/matplotlib/artist.py b/lib/matplotlib/artist.py
@@ -903,6 +903,22 @@ def matchfunc(x):
             artists.append(self)
         return artists
 
+    def get_cursor_data(self, event):
+        """
+        Get the cursor data for a given event.
+        """
+        return None
+
+    def format_cursor_data(self, data):
+        """
+        Return *cursor data* string formatted.
+        """
+        try:
+            data[0]
+        except (TypeError, IndexError):
+            data = [data]
+        return ', '.join('{:0.3g}'.format(item) for item in data)
+
 
 class ArtistInspector(object):
     """

diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1694,15 +1694,9 @@ def onRemove(self, ev):
 
             canvas.mpl_connect('mouse_press_event',canvas.onRemove)
         """
-        def sort_artists(artists):
-            # This depends on stable sort and artists returned
-            # from get_children in z order.
-            L = [(h.zorder, h) for h in artists]
-            L.sort()
-            return [h for zorder, h in L]
-
         # Find the top artist under the cursor
-        under = sort_artists(self.figure.hitlist(ev))
+        under = self.figure.hitlist(ev)
+        under.sort(key=lambda x: x.zorder)
         h = None
         if under:
             h = under[-1]
@@ -2800,6 +2794,16 @@ def mouse_move(self, event):
             except (ValueError, OverflowError):
                 pass
             else:
+                artists = event.inaxes.hitlist(event)
+                if event.inaxes.patch in artists:
+                    artists.remove(event.inaxes.patch)
+
+                if artists:
+                    artists.sort(key=lambda x: x.zorder)
+                    a = artists[-1]
+                    data = a.get_cursor_data(event)
+                    if data is not None:
+                        s += ' [%s]' % a.format_cursor_data(data)
                 if len(self.mode):
                     self.set_message('%s, %s' % (self.mode, s))
                 else:

diff --git a/lib/matplotlib/image.py b/lib/matplotlib/image.py
@@ -683,6 +683,20 @@ def get_extent(self):
             else:
                 return (-0.5, numcols-0.5, -0.5, numrows-0.5)
 
+    def get_cursor_data(self, event):
+        """Get the cursor data for a given event"""
+        xmin, xmax, ymin, ymax = self.get_extent()
+        if self.origin == 'upper':
+            ymin, ymax = ymax, ymin
+        arr = self.get_array()
+        data_extent = mtransforms.Bbox([[ymin, xmin], [ymax, xmax]])
+        array_extent = mtransforms.Bbox([[0, 0], arr.shape[:2]])
+        trans = mtransforms. BboxTransform(boxin=data_extent,
+                                           boxout=array_extent)
+        y, x = event.ydata, event.xdata
+        i, j = trans.transform_point([y, x]).astype(int)
+        return arr[i, j]
+
 
 class NonUniformImage(AxesImage):
     def __init__(self, ax, **kwargs):

diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
@@ -158,6 +158,39 @@ def test_imsave_color_alpha():
 
     assert_array_equal(data, arr_buf)
 
+
+@cleanup
+def test_cursor_data():
+    from matplotlib.backend_bases import MouseEvent
+
+    fig, ax = plt.subplots()
+    im = ax.imshow(np.arange(100).reshape(10, 10), origin='upper')
+
+    x, y = 4, 4
+    xdisp, ydisp = ax.transData.transform_point([x, y])
+
+    event = MouseEvent('motion_notify_event', fig.canvas, xdisp, ydisp)
+    assert im.get_cursor_data(event) == 44
+
+    ax.clear()
+    im = ax.imshow(np.arange(100).reshape(10, 10), origin='lower')
+
+    x, y = 4, 4
+    xdisp, ydisp = ax.transData.transform_point([x, y])
+
+    event = MouseEvent('motion_notify_event', fig.canvas, xdisp, ydisp)
+    assert im.get_cursor_data(event) == 44
+
+    fig, ax = plt.subplots()
+    im = ax.imshow(np.arange(100).reshape(10, 10), extent=[0, 0.5, 0, 0.5])
+
+    x, y = 0.25, 0.25
+    xdisp, ydisp = ax.transData.transform_point([x, y])
+
+    event = MouseEvent('motion_notify_event', fig.canvas, xdisp, ydisp)
+    assert im.get_cursor_data(event) == 55
+
+
 @image_comparison(baseline_images=['image_clip'])
 def test_image_clip():
     from math import pi