Getting pixel values under cursor

[Bill]

I'm using Tkinter right now for a GUI.  Is there a way for me to get, in
real time or when the user clicks the mouse button on a pixel, the pixel
intensity value?  Currently, I have a tkinter label which is showing a large
grey scale image.  I would like the user to move the mouse cursor over the
image and show the pixel intensity under the cursor.  Is there a way to do
this?  Perhaps some kind of event binding with the mouse and the image?
Would putting the image in a canvas instead provide more flexibility?

Thanks in advance,
Bill