ret在以下程序中有什么用

Question

import cv2
import numpy as np

img1 = cv2.imread('p1.jpg')
img2 = cv2.imread('p2.jpg')

rows,cols,channels = img2.shape
roi = img1[0:rows,0:cols]

ret,img2gray = cv2.cvtColor(img2, cv2.COLOR_BGR2GRAY)
mask = cv2.threshold(img2gray,100,255, cv2.THRESH_BINARY_INV)

cv2.imshow('mask',mask)
cv2.waitKey(0)
cv2.destroyAllWindows() 

如果我从img2gray代码行中删除ret，则以下错误将生成此ValueError

Traceback (most recent call last):
  File "oc5.py", line 10, in <module>
    ret,img2gray = cv2.cvtColor(img2, cv2.COLOR_BGR2GRAY)
ValueError: too many values to unpack (expected 2)

Answer 1

cv2.cvtColor返回两个值。 Ret只是一个虚拟变量，用于保存第一个值