如何在tkinter python中获取用户签名

import tkinter as tk

class SignatureApp:
    def __init__(self, root):
        self.root = root
        self.canvas = tk.Canvas(root, width=400, height=200, bg="white")
        self.canvas.pack()

        self.last_x = None
        self.last_y = None

        self.canvas.bind("<Button-1>", self.on_mouse_down)
        self.canvas.bind("<B1-Motion>", self.on_mouse_move)
        self.canvas.bind("<ButtonRelease-1>", self.on_mouse_up)

    def on_mouse_down(self, event):
        self.last_x = event.x
        self.last_y = event.y

    def on_mouse_move(self, event):
        if self.last_x is not None and self.last_y is not None:
            self.canvas.create_line(self.last_x, self.last_y, event.x, event.y)
            self.last_x = event.x
            self.last_y = event.y

    def on_mouse_up(self, event):
        self.last_x = None
        self.last_y = None

root = tk.Tk()
app = SignatureApp(root)
root.mainloop()