How to save what a tkinter window looks like without screenshot? (Possibly a numpy array?)

Question

I have a short program that generates images of 1, 2, 3, and 4 random coloured circles to train a neural network on. My issue is, just doing 4000 images takes about 20-30 mins, and I need about 50000 images. My current method is to create the image, screenshot it, and then delete the tkinter object and restart. The issue is, windows 11 has a little fade in/slide animation when a new window is created, only about 200 ms, but it adds up quite a bit, because I need to wait for the animation to finish to take the screenshot.

So my question is, Is there another way to save a tkinter canvas other than screenshot?

I want to point out that I am putting these images into a numpy array, so putting it directly into an array is an option, but I need some way to save that as a file, so I dont need to generate the images every time.

My current code (only showing how I make 4 circles)

from PIL import ImageGrab
from tkinter import *
from random import choice, randint

colors = ["red", "blue", "green", "yellow", "orange", "purple", "black"]

s = 1   #scale 1 = 50x50 px canvas, 20x20 px circles

def four(i):
    def ss():
        x, y = screen.winfo_rootx(), screen.winfo_rooty()
        w, h = screen.winfo_width(), screen.winfo_height()
        img = ImageGrab.grab((x, y, x + w, y + h))
        img.save(f"4MC{i}.jpg")

    def des():
        root.destroy()
    
    root = Tk()

    screen = Canvas(root, width = 50 * s, height = 50 * s, bg="white")
    screen.pack()

    colors = ["red", "blue", "green", "yellow", "orange", "purple", "black"]

    x = randint(1 * s, 19 * s)
    y = randint(1 * s, 19 * s)

    screen.create_oval(x, y, x + 10 * s, y + 10 * s, fill=choice(colors), outline="")
    screen.create_oval(x, y + 20 * s, x + 10 * s, y + 30 * s, fill=choice(colors), outline="")
    screen.create_oval(x + 20 * s, y, x + 30 * s, y + 10 * s, fill=choice(colors), outline="")
    screen.create_oval(x + 20 * s, y + 20 * s, x + 30 * s, y + 30 * s, fill=choice(colors), outline="")

    root.after(200, ss)
    root.after(300, des)

    root.mainloop()

for i in range(1000):
    four(i)

Answer 1

I think your approach of destroying and creating a new window over each iteration is tedious way of doing it. Instead, you can clear the canvas each time and keep creating this random circles and then click a picture of it.

from PIL import ImageGrab
from tkinter import *
from random import choice, randint

root = Tk()
colors = ["red", "blue", "green", "yellow", "orange", "purple", "black"]
s = 1 #scale 1 = 50x50 px canvas, 20x20 px circles
i = 1 # Variable for creating numbers in file-name: 1,2,3,...
LIMIT = 10 # Variable to keep limit of how many iterations/image

def create(i):
    if i <= LIMIT:
        screen.delete('all')
        
        x = randint(1 * s, 19 * s)
        y = randint(1 * s, 19 * s)

        screen.create_oval(x         , y         , x + 10 * s, y + 10 * s, fill=choice(colors), outline="")
        screen.create_oval(x         , y + 20 * s, x + 10 * s, y + 30 * s, fill=choice(colors), outline="")
        screen.create_oval(x + 20 * s, y         , x + 30 * s, y + 10 * s, fill=choice(colors), outline="")
        screen.create_oval(x + 20 * s, y + 20 * s, x + 30 * s, y + 30 * s, fill=choice(colors), outline="")
        
        if i == 1: # If it is first iteration, then the event loop hasnt been entered, so give a delay
            root.after(200, capture, screen, f'4MC{i}')
        else:
            # Give a general delay of 100ms before capturing the image
            root.after(100, capture, screen, f'4MC{i}')

        i += 1
        root.after(300, create, i) # Give a delay of 300ms before creating the circle

def capture(wid, file_name='img',file_format='png'):
    """Take screenshot of the passed widget"""
    
    x0 = wid.winfo_rootx()
    y0 = wid.winfo_rooty()
    x1 = x0 + wid.winfo_width()
    y1 = y0 + wid.winfo_height()
    
    im = ImageGrab.grab(bbox=(x0, y0, x1, y1)) # bbox means boundingbox, which is shown in the image below
    im.save(f'{file_name}.{file_format}')  # Can also say im.show() to display it

screen = Canvas(root, width = 50 * s, height = 50 * s, bg="white")
screen.pack()

create(i)

root.mainloop()

I replaced your ss with my capture which is taken from another answer of mine, the logic is same but adds more flexibility, you can use your function with necessary changes. I suggest you first run this with a LIMIT = 10 and check if the delay are okay, if not you can adjust it and then move on to produce your 50000 image-set.

If you furthermore want to convert/load your image as a numpy array, then check the first reference link below.

Extra references:

• How do I convert a PIL Image into a NumPy array?
• Emulate for loop with after
• How do you take a screenshot of a particular widget in Tkinter?