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_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)
Answers:
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)
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 with a code that could run on either last or older version of OpenCV.
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)
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)
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 with a code that could run on either last or older version of OpenCV.