Pixel plotting with Tkinter

tk_photoimage_pixels0.py

#!/usr/bin/env python3

''' Use a PhotoImage to plot single pixels in a Tkinter Label

    For some strange reason, it starts out fast but slows down...

    Written by PM 2Ring 2017.05.13
'''

import tkinter as tk

width, height = 301, 211

root = tk.Tk()
photo = tk.PhotoImage(width=width, height=height)
label = tk.Label(root, bg='#000', image=photo)
label.pack()

x, y = 10, 80
dx = dy = 1

def draw():
    ''' Linear motion, with bouncing '''
    global x, y, dx, dy
    photo.put('#cf9', (x, y))
    x += dx
    y += dy
    if not 0 <= x < width:
        dx = -dx
        x += dx
    if not 0 <= y < height:
        dy = -dy
        y += dy
    root.after(1, draw)

draw()
root.mainloop()