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Python: ValueError: too many values to unpack

asked 2014-08-26 08:18:29 -0600

ahmadux gravatar image

updated 2014-08-26 08:20:02 -0600

I'm writing an opencv program and I found a script on another stackoverflow question: Computer Vision Masking A Human Hand

I've already asked this question at Stackoverflow: OpenCV python: ValueError: too many values to unpack

When I run the scripted answer, I get the following error:

Traceback (most recent call last):
    File "", line 13, in <module>
    contours, _ = cv2.findContours(skin_ycrcb, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
ValueError: too many values to unpack

The code:

import sys
import numpy
import cv2

im = cv2.imread('Photos/test.jpg')
im_ycrcb = cv2.cvtColor(im, cv2.COLOR_BGR2YCR_CB)

skin_ycrcb_mint = numpy.array((0, 133, 77))
skin_ycrcb_maxt = numpy.array((255, 173, 127))
skin_ycrcb = cv2.inRange(im_ycrcb, skin_ycrcb_mint, skin_ycrcb_maxt)
cv2.imwrite('Photos/output2.jpg', skin_ycrcb) # Second image

contours, _ = cv2.findContours(skin_ycrcb, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
for i, c in enumerate(contours):
    area = cv2.contourArea(c)
    if area > 1000:
        cv2.drawContours(im, contours, i, (255, 0, 0), 3)
cv2.imwrite('Photos/output3.jpg', im)

Any help is appreciated!

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1 answer

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answered 2014-08-26 10:09:13 -0600

Guanta gravatar image

I bet you are using the current OpenCV's master branch: here the return statements have changed, see

Thus, change the correspinding line to:

_, contours, _ = cv2.findContours(skin_ycrcb, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

Or: since the current trunk is still not stable and you probably will run in some more problems, you may want to use OpenCV's current stable version 2.4.9.

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Excellent stuff! To note, I changed the line. Thanks for the solution!

ahmadux gravatar imageahmadux ( 2014-08-26 10:39:22 -0600 )edit

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Asked: 2014-08-26 08:18:29 -0600

Seen: 15,835 times

Last updated: Aug 26 '14