通过getTrackbarPos获取trackbar位置
def threshold_trackbar(gray_res):
cv.namedWindow('image',flags=cv.WINDOW_NORMAL)
cv.createTrackbar('num','image',0,255,lambda x:None)
while True:
num = cv.getTrackbarPos('num','image')
_, threshold1 = cv.threshold(gray_res,num,255,cv.THRESH_BINARY)
cv.imshow('image',threshold1)
k = cv.waitKey(1) & 0xFF
if k == 27:
break