使用python编写一个画图的软件，背景为黑色， 画笔为白色，在画布上可以进行画图，点击保存按钮后，整体保存为jpg文件

import tkinter as tk
from PIL import ImageGrab

class DrawingApp:
    def __init__(self):
        self.root = tk.Tk()
        self.root.title("简单画图软件")

        self.canvas = tk.Canvas(self.root, bg='black', width=800, height=600)
        self.canvas.pack()

        self.pen_color = 'white'
        self.last_x, self.last_y = None, None

        self.canvas.bind("<B1-Motion>", self.paint)
        self.canvas.bind("<ButtonRelease-1>", self.reset)

        save_button = tk.Button(self.root, text="保存", command=self.save_image)
        save_button.pack()

        reset_button = tk.Button(self.root, text="重置", command=self.reset_canvas)
        reset_button.pack()

    def paint(self, event):
        if self.last_x and self.last_y:
            self.canvas.create_line(self.last_x, self.last_y, event.x, event.y, fill=self.pen_color, width=2)
        self.last_x, self.last_y = event.x, event.y

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

    def save_image(self):
        # 获取窗口在屏幕上的位置
        x = self.root.winfo_rootx()
        y = self.root.winfo_rooty()
        # 获取画布在窗口中的位置和大小
        w = self.canvas.winfo_width()
        h = self.canvas.winfo_height()
        # 使用 ImageGrab 截取画布区域并保存为图片
        img = ImageGrab.grab((x + self.canvas.winfo_x(), y + self.canvas.winfo_y(), x + self.canvas.winfo_x() + w, y + self.canvas.winfo_y() + h))
        img.save("drawing.jpg")

    def reset_canvas(self):
        self.canvas.delete("all")

    def run(self):
        self.root.mainloop()

if __name__ == "__main__":
    app = DrawingApp()
    app.run()