from tkinter import *
import pyscreenshot as ImageGrab

root = Tk()
cv = Canvas(root)
cv.create_rectangle(10,10,50,50)
cv.pack()

print("wut")

def getter(widget):
    x=widget.winfo_rootx()+widget.winfo_x()
    y=widget.winfo_rooty()+widget.winfo_y()
    x1=x+widget.winfo_width()
    y1=y+widget.winfo_height()

    im = ImageGrab.grab(bbox=(x,y,x1,y1))
    im.save("screenshot.png")
    print("ok")

#getter(cv)
root.after(500, lambda:getter(cv))
root.after(4500, lambda: exit())
root.mainloop()