Problem in saving Python tkinter Canvas drawing as an image file using PIL Image and ImageDraw functions - python-3.x

Question

Problem statement
I have written a code in Python on which a user can draw on a tkinter GUI canvas. The program is capable of taking the app's screenshot but saving the canvas content to a viewable image file (such as .jpg or .png) is not properly done yet.
Screenshots
What I draw on the tkinter app's canvas.
What the code (given below) saved.
What I expect.
I have tried and will expect
A number of possible solutions from the internet (including Stack Overflow) have been tried but somehow the process cannot be completed successfully. After drawing whatever on the canvas, the saved image will have nothing but a dot whether it is in *.jpg or *.png. I need the image of the full canvas with all the colorful drawings on it in that saved image file.
For any reference, here is my code
from tkinter import Tk, Canvas, Button
from PIL import Image, ImageDraw
X = 0
Y = 0
app = Tk()
def set_xy(click):
global X, Y
X, Y = click.x, click.y
def draw_line(drag):
global X, Y
draw_panel.create_line((X, Y, drag.x, drag.y), fill="black", capstyle="round", smooth=True)
draw.line([(X, Y), (drag.x, drag.y)], fill="black", joint="curve")
X, Y = drag.x, drag.y
def save(event=None):
# ATTENTION: This is not working properly
image.save("image.png", "png")
# App's drawing panel
draw_panel = Canvas(app, background="white", cursor="dot")
draw_panel.place(x=0, relwidth=1.0, y=0, relheight=1.0)
# Invisible canvas for saving as an image later on
image = Image.new("RGB", (draw_panel.winfo_width(), draw_panel.winfo_height()), "white")
draw = ImageDraw.Draw(image)
# Mouse and Key bindings
draw_panel.bind('<Button-1>', set_xy)
draw_panel.bind('<B1-Motion>', draw_line)
app.bind('<s>', save) # press 's' to save the drawing as .png
app.mainloop()
Addition Informations:
HOST: Windows 10 Version 20H2 (OS Build 19042.2130)
IDE: PyCharm 2022.2 (Community Edition) (Build #PC-222.3345.131)
Language: Python 3.10.6
Framework: tkinter Tk/Tcl 8.6
Library: pillow 9.2.0
Any solution shall be highly appreciated, and I shall be thankful.

Answer 1

That's a nice idea and there is just one piece missing. You set the size of the image to the size of the canvas before you call mainloop() for the first time. The canvas does not have a size at this time because the window has not been initiated, yet.
You need to force an update before getting the width and height. Then, it works fine:
# Invisible canvas for saving as an image later on
draw_panel.update()
image = Image.new("RGB", (draw_panel.winfo_width(), draw_panel.winfo_height()), "white")
draw = ImageDraw.Draw(image)
If you print the draw_panel.winfo_width() before and after calling the update, you see what I mean. Before update(), width and height are both 1. Afterwards, they are 200, as they should be.