Want to find contours -> ValueError: not enough values to unpack (expected 3, got 2), this appears

Question

My simple python code is this

import cv2

img=cv2.imread(\'Materials/shapes.png\')

blur=cv2.GaussianBlur(img,(3,3),0)
gray=cv2.cvtColor(blur,cv2.COLOR_BGR2G         


        

Answer 1

Well explained in this python code example, the best way to make your code version-proof is with this following syntax:

# check OpenCV version
major = cv2.__version__.split('.')[0]
if major == '3':
    ret, contours, hierarchy = cv2.findContours(im.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
else:
    contours, hierarchy = cv2.findContours(im.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

This provides you a code that could run on last or older version of OpenCV.

Answer 2

the function cv2.findContours() has been changed to return only the contours and the hierarchy and not ret

you should change it to:

contours,hierachy=cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)