定义全局变量

Question

我正在尝试创建一个用户界面，用户可以在其中编辑实时流openCV应用程序的阈值。 运行此代码时，我收到一条错误消息，指出未定义全局变量“ slider”，而且我真的不明白为什么：

from threading import Thread  
from picamera.array import PiRGBArray
from picamera import PiCamera
import time
import cv2
import imutils
from Tkinter import*


thresh=0



def get_thresh():
    global thresh
    global slider
    thresh=slider.get()



def funkcija1():

        window=Tk()
        window.title("Test")
        window.geometry('800x480')

    slider=Scale(window,from_=0, to=255,command=get_thresh())
    slider.pack()

        window.mainloop()

def funkcija2():
    camera=PiCamera()
    rawCapture=PiRGBArray(camera)
    camera.resolution=(640,480)
    camera.framerate=32
    rawCapture=PiRGBArray(camera,size=(640,480))

    time.sleep(0.1)

    for frame in camera.capture_continuous(rawCapture,format="bgr",use_video_port=True):



    image=frame.array

    qray=cv2.cvtColor(image,cv2.COLOR_BGR2GRAY)
    cv2.imshow("crnobela",qray)
    threshold=cv2.threshold(qray,thresh,255,cv2.THRESH_BINARY)[1]
    cv2.imshow("thresh",threshold)
    canny=cv2.Canny(threshold,30,200)
    cv2.imshow("canny",canny)
    konture=cv2.findContours(canny.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)[1]

    cv2.drawContours(image,konture,-1,(0,255,0),3)  

    cv2.imshow("slika",image)

    key=cv2.waitKey(1) & 0xFF
    rawCapture.truncate(0)

    if key == ord("q"):
        cv2.destroyAllWindows()
        break


def Main():


    t1=Thread(target=funkcija1,args=())
    t2=Thread(target=funkcija2,args=())
    t1.start()
    t2.start()

if __name__ == '__main__':
    Main()