python - OpenCV Contours - need more than 2 values to unpack

Question

I am trying to implement contours using the following code..

im = cv2.imread('C:UsersPrashantDesktopT.jpg')
imgray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
ret,thresh = cv2.threshold(imgray,127,255,0)
image, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
img = cv2.drawContour(im, contours, -1, (0,255,0), 3)
cv2.imshow('Image1',img)

but i am continously getting the following error.

Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "C:Python27libsite-packagesspyderlibwidgetsexternalshellsitecustomize.py", line 540, in runfile
    execfile(filename, namespace)
  File "C:/Users/Prashant/.spyder2/.temp.py", line 17, in <module>
    image, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
ValueError: need more than 2 values to unpack

do the function findContours need more arguments? wht could i do to correct it.

Answer 1

In OpenCV 2, findContours returns just two values, contours and hierarchy. The error occurs when python tries to assign those two values to the three names given on left in this statement:

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