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in Python by (12.7k points)

I've as of late began learning OpenCV on Python. 

I'm alluding to this instructional exercise here, to get some assistance on getting the forms of a picture. 

My code:

import cv2

import numpy as np

img = cv2.imread('shapes.jpg', 0)

img = cv2.medianBlur(img, 5)

thresh =     cv2.adaptiveThreshold(img,255,cv2.ADAPTIVE_THRESH_GAUSSIAN_C,\

cv2.THRESH_BINARY,11,2)

cv2.imshow('Thresh', thresh)

cv2.waitKey(0)

cv2.destroyAllWindows()

image, contours, hierarchy =   cv2.findContours(thresh.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

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

cv2.imshow('Contours', img)

cv2.waitKey(0)

cv2.destroyAllWindows()

The first thresholded picture is showing up, yet after that, I get a mistake message as

Traceback (most recent call last):

  File "contours.py", line 21, in <module>

    image, contours, hierarchy =     cv2.findContours(thresh.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

ValueError: need more than 2 values to unpack

Anyone, please me to resolve this issue.

1 Answer

0 votes
by (26.4k points)

You can use below code:

cv2.findContours(...)

just returns two objects, you're attempting to unload it into three. 

change that line to this:

contours, hierarchy =   cv2.findContours(thresh.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

It will work.

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