Merge pull request #1144 from blink1073/master

Clear the blit background when the image changes

skimage/viewer/viewers/core.py

@@ -77,6 +77,8 @@ class BlitManager(object):
             self.canvas.restore_region(self.background)
             self.draw_artists()
             self.canvas.blit(self.ax.bbox)
+        else:
+            self.canvas.draw_idle()
 
     def draw_artists(self):
         for artist in self.artists:
@@ -368,6 +370,9 @@ class ImageViewer(QtGui.QMainWindow):
             clim = (0, clim[1])
         self._image_plot.set_clim(clim)
 
+        if self.useblit:
+            self._blit_manager.background = None
+
         self.redraw()
 
     def reset_image(self):