Add spacings

pylidc/Annotation.py

@@ -904,15 +904,17 @@ def update(_):
             txt = 'Z: %.3f'
             txt = txt % float(images[current_slice].ImagePositionPatient[-1])
             sslice.label.set_text(txt)
+
             if contour_checkbox.is_checked:
                 for i,c in enumerate(contour_lines):
-                    flag = (index_of_contour[i] == current_slice)
-                    flag = flag and (current_slice >= min_slice)
-                    flag = flag and (current_slice <= max_slice)
+                    flag = ((index_of_contour[i] == current_slice) and 
+                            (current_slice >= min_slice) and
+                            (current_slice <= max_slice))
                     # Set contour visible if flag is True.
                     c.set_visible(flag)
             else:
                 for c in contour_lines: c.set_visible(False)
+
             fig.canvas.draw_idle()
 
         def update_contours(_):

pylidc/Scan.py

@@ -569,6 +569,7 @@ def update(_):
         sslice.on_changed(update)
         update(None)
         plt.show()
+        return sslice
 
     @property
     def slice_zvals(self):
@@ -594,6 +595,16 @@ def slice_spacing(self):
         """
         return np.median(np.diff(self.slice_zvals))
 
+    @property
+    def spacings(self):
+        """
+        The spacings in the i, j, k image coordinate directions, as a 
+        length 3 array.
+        """
+        return np.array([self.pixel_spacing,
+                         self.pixel_spacing,
+                         self.slice_spacing])
+
     def to_volume(self, verbose=True):
         """
         Return the scan as a 3D numpy array volume.