Tkinter, getting canvas-object, how?

[skanemupp at yahoo.se]

so i load a gif onto a canvas and when i click the canvs i want to get
the color of the pixel that is clicked.
so i need to ge the object im clicking.
i was told in another thread to use find_withtag or find_closest but
it is not working, maybe im using the
method on the wrong object.
how do i do this?
and how do i then get specifics about that object, ie the pixel-color?

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python25\lib\lib-tk\Tkinter.py", line 1403, in __call__
    return self.func(*args)
  File "C:\Users\saftarn\Desktop\pythonkod\mapexperiments
\mapgetobject.py", line 17, in callback
    undermouse=find_closest(master.CURRENT)
NameError: global name 'find_closest' is not defined

from Tkinter import *

master = Tk()

w = Canvas(master, width=400, height=625)
w.pack(expand = YES, fill = BOTH)

mapq = PhotoImage(file = 'C:\Users\saftarn\Desktop\Maps\provinces-of-
sweden.gif')
w.create_image(30, 30, image = mapq, anchor = NW)

def key(event):
    print "pressed", repr(event.char)

def callback(event):
    clobj=event.widget
##    undermouse=find_withtag(master.CURRENT)
    undermouse=find_closest(master.CURRENT)
    print repr(undermouse)

w.bind("<Key>", key)
w.bind("<Button-1>", callback)
w.pack()

mainloop()