Demo/tkinter/guido/paint.py

""""Paint program by Dave Michell.

Subject: tkinter "paint" example
From: Dave Mitchell <davem@magnet.com>
To: python-list@cwi.nl
Date: Fri, 23 Jan 1998 12:18:05 -0500 (EST)

  Not too long ago (last week maybe?) someone posted a request
for an example of a paint program using Tkinter. Try as I might
I can't seem to find it in the archive, so i'll just post mine
here and hope that the person who requested it sees this!

  All this does is put up a canvas and draw a smooth black line
whenever you have the mouse button down, but hopefully it will
be enough to start with.. It would be easy enough to add some 
options like other shapes or colors...

						yours,
						dave mitchell
						davem@magnet.com
"""

from Tkinter import *

"""paint.py: not exactly a paint program.. just a smooth line drawing demo."""

b1 = "up"
xold, yold = None, None

def main():
  root = Tk()
  drawing_area = Canvas(root)
  drawing_area.pack()
  drawing_area.bind("<Motion>", motion)
  drawing_area.bind("<ButtonPress-1>", b1down)
  drawing_area.bind("<ButtonRelease-1>", b1up)
  root.mainloop()

def b1down(event):
  global b1
  b1 = "down"		# you only want to draw when the button is down
			# because "Motion" events happen -all the time-

def b1up(event):
  global b1, xold, yold
  b1 = "up"
  xold = None		# reset the line when you let go of the button
  yold = None

def motion(event):
  if b1 == "down":
    global xold, yold
    if xold != None and yold != None:
      event.widget.create_line(xold,yold,event.x,event.y,smooth=TRUE)
			# here's where you draw it. smooth. neat.
    xold = event.x
    yold = event.y

if __name__ == "__main__":
  main()