(Continuous) strip chart recorders with Tkinter/PIL

Chris WRIGHT caw at cs.mu.OZ.AU
Mon Mar 27 04:11:15 CEST 2000

I need to produce "strip chart" type screen output for various
physiological parameters. I'm currently using Tkinter with a Canvas, a
PhotoImage and the put method on the Image and calling update() to
redicplay the canvas. This is OK, but I'd like to make it a bit faster. 
I'm not sure that using PIL will help...The putpixel method is certainly
quick, but the re-draw doesn't happen when I call update...

I'd be grateful for help and advice as to how to speed this process up

Sample code: (modified from "plot single pixel" thread)

from Tkinter import *

class App:
     def __init__(self, master):
         self.frame = frame = Frame(master)
         self.button = Button(frame, text="QUIT", fg="red",command=frame.quit)
         self.test_B = Button(frame, text="Test", command=self.test)
         self.img = PhotoImage(height=100, width=100)
         self.canvas = Canvas(frame, width=100, height=100)
         self.canvas.create_image(0, 0, anchor=NW, image=self.img)
     def test(self):
         import time
         max_x = max_y = 100
         start = time.time()
         start_cpu = time.clock()

         m = self.frame.master
         for x in range(max_x):
             for y in range(max_y):
                 self.img.put("black", (x,y))
                 m.update() # UPDATE THE CANVAS
         elapsed = time.time() - start
         elapsed_cpu = time.clock() - start_cpu
         print "done -- it took us: "
         print elapsed
         print elapsed_cpu
root = Tk()
app = App(root)

Dr Chris Wright
Deputy Director, Intensive Care Unit
Monash Medical Centre,
Clayton 3168 VIC

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