在 python 中使用 cv2.findContours() 时出现 ValueError.->没有足够的值来解包(预期为 3，得到 2) [英] ValueError while using cv2.findContours() in python. -> not enough values to unpack (expected 3, got 2)

问题描述

出现错误:

Traceback (most recent call last):
    File "motion_detector.py", line 21, in <module>
        (_, cnts, _) = cv2.findContours(thresh_frame.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE) 
ValueError: not enough values to unpack (expected 3, got 2)

在检测图像中的轮廓时遇到问题.已经从教程中仔细检查并从堆栈溢出中查看以了解我遗漏了什么，但找不到解决方案.使用 Python 3.6.4 和 OpenCV 4.0.0.感谢您的帮助！

Having problems with detecting contours in an image. Have been double checking from the tutorial and also looking from stack overflow to understand where I miss something, but can't find the solution. Using Python 3.6.4 and OpenCV 4.0.0. Thanks for the help!

代码在这里:

import cv2, time

first_frame = None

video = cv2.VideoCapture(0)

while True:
    check, frame = video.read()

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    gray = cv2.GaussianBlur(gray,(21,21),0) 

    if first_frame is None:
        first_frame = gray 

    delta_frame = cv2.absdiff(first_frame, 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) < 1000: 
            continue
        (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("Color Frame", frame)

    key = cv2.waitKey(1)
    print(gray)
    print(delta_frame)

    if key == ord('q'):
        break

video.release()
cv2.destroyAllWindows

推荐答案

我也遇到了同样的问题，如果你使用的是旧教程 cv2.findContours() 函数返回 3 值但如果你是使用更高版本它会返回 2 个值，因此您可以删除第一个变量赋值并像这样使用

I also encountered same problem, if you are using an old tutorial cv2.findContours() function returns 3 value but if you are using later versions it returns 2 value so you can remove first variable assignment and use like that

cnts, _ = cv2.findContours(thresh_frame.copy(), cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

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