ValueError: not enough values to unpack (expected 3, got 2) (OpenCV)

Question

我的 python 程序有问题（第 22 行 -(_cnts_) ）。我用win11，PyCharm。我收到错误 ValueError: not enough values to unpack (expected 3, got 2).

import cv2, time
import pandas

first_frame = None
video = cv2.VideoCapture(0)

while True:

    check, frame = video.read()
    print(frame)

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

    if first_frame is None:
        first_frame = gray
        continue

    delta_frame = cv2.absdiff(first_frame,gray)
    thresh_delta = cv2.threshold(delta_frame, 30, 255, cv2.THRESH_BINARY)[1]
    thresh_delta = cv2.dilate(thresh_delta, None, iterations=0)
    (_,cnts,_) = cv2.findContours(thresh_delta.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('frame',frame)
    cv2.imshow('Capturing',gray)
    cv2.imshow('delta',delta_frame)
    cv2.imshow('thresh',thresh_delta)

    cv2.imshow('Capturing #by ensar',gray)

    key = cv2.waitKey(1)

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

video.release()
cv2.destroyAllWindows()

当我尝试添加此行时出现问题

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

Answer 1

findContours 方法 returns 两个值：contours 和 hierarchy 但您期望三个值：_,cnts,_。更改为：

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

Answer 2

我把错误行修改成这样：

cnts = cv2.findContours(thresh_delta.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)

上面的return值为（在调试器中看到）：

cnts = ((), None)

所以这将解决问题，但代码稍后会出现另一个问题，因为它在循环中使用此值并且其内容是 empty tuple 和 None。

ValueError: not enough values to unpack (expected 3, got 2) (OpenCV)

ValueError: not enough values to unpack (expected 3, got 2) (OpenCV)

python

opencv

python-3.x