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

问题

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_BGR2GRAY)
returns,thresh=cv2.threshold(gray,80,255,cv2.THRESH_BINARY)

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

for cnt in contours:

    area=cv2.contourArea(cnt) #contour area

    if (area>1220):
        cv2.drawContours(img,[cnt],-1,(0,255,0),2)
        cv2.imshow('RGB',img)
        cv2.waitKey(1000)
        print(len(cnt))

import numpy as np

contours=np.array(contours)

print(contours)

This worked fine. But recently without me even making any changes. This was throwed to me

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

ValueError: not enough values to unpack (expected 3, got 2)

Help me guys.

Thanks.

回答1:

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)

回答2:

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.

来源：https://stackoverflow.com/questions/54164630/want-to-find-contours-valueerror-not-enough-values-to-unpack-expected-3-go

标签

python

python-3.x

opencv-contour