ValueError: not enough values

Question

I tried running the code below and I came across a ValueError. My expected output was that the code would open up four camera windows that are all different. Can anyone please help me?

This is my code down below.

import cv2

firstframe = None

video = cv2.VideoCapture(0)

while True:
    check, frame = video.read()
    status = 0
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    gray = cv2.GaussianBlur(gray, (21, 21), 0)

    if firstframe is None:
       firstframe = gray
       continue

    delta_frame = cv2.absdiff(firstframe,gray)
    thresh_frame = cv2.threshold(delta_frame, 30, 255, cv2.THRESH_BINARY)[1]
    thresh_frame = cv2.dilate(thresh_frame, None, iterations=2)
    
    (_,cnts,_) = cv2.findContours(thresh_frame.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

    for contour in cnts:
        if cv2.contourArea(contour) < 10000:
            continue
        status = 1
        (x, y, w, h) = cv2.boundingRect(contour)
        cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 3)

    cv2.imshow("Gray Frame", gray)
    cv2.imshow("Delta Frame", delta_frame)
    cv2.imshow("Threshold Frame", thresh_frame)
    cv2.imshow("Normal Frame", frame)

    key = cv2.waitKey(1)

    if key == ord('q'):
        break
    print(status)
    
video.release()
cv2.destroyAllWindows

The error I got was this:

 cnts = cv2.findContours(thresh_frame.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
ValueError: not enough values to unpack (expected 3, got 2)

Just to add to the posted answer, if you want the second element, even if the return of the function is more than 2 elements, you could use ```(_,cnts,*_) = ...```. — sj95126, Sep 18 '21 at 15:05
Does this answer your question? [Want to find contours -> ValueError: not enough values to unpack (expected 3, got 2), this appears](https://stackoverflow.com/questions/54164630/want-to-find-contours-valueerror-not-enough-values-to-unpack-expected-3-go) — Christoph Rackwitz, Jul 15 '22 at 11:37

score 0 · Accepted Answer · answered Sep 18 '21 at 14:59

0

cv2.findContours returns 2 things (rather than 3). Those two are contours,hierarchy.

Change from (_,cnts,_) = cv2.findContours... to contours,hierarchy = cv2.findContours...

answered Sep 18 '21 at 14:59

saedx1

984
6
20

question should be flagged as a **duplicate** of https://stackoverflow.com/questions/54164630/want-to-find-contours-valueerror-not-enough-values-to-unpack-expected-3-go – Christoph Rackwitz Jul 15 '22 at 11:38

ValueError: not enough values

1 Answers1