python - OpenCV 错误 - 不是 numpy 数组

Question

我收到这个错误:

<unknown> is not a numpy array

执行这段代码时:

import cv2
import numpy as np

try:

    cap = cv2.VideoCapture(0)

    while (cap.isOpened()):
        ret,img=cap.read()
        cv2.imshow('output',img)
        img2=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) 
        cv2.imshow('gray_scale',img2)
        imgthreshold=cv2.inRange(img,cv2.cv.Scalar(3,3,125),cv2.cv.Scalar(40,40,255),)
        cv2.imshow('thresholded',imgthreshold)

        k=cv2.waitKey(10)
        if k==27:
            break

    cap.release()
    cv2.destroyAllWindows()


except Exception as inst:

    cap.release()
    cv2.destroyAllWindows()
    print("Eroor!!")
    print(inst)
    raise

这是回溯:

Traceback (most recent call last):
    File "C:\Users\... ...\camara.py", line 14, in <module>
        imgthreshold=cv2.inRange(img,cv2.cv.Scalar(3,3,125),cv2.cv.Scalar(40,40,255),)
TypeError: <unknown> is not a numpy array

我希望你能帮我解决这个问题。我已经检查了所有的依赖项，如果我删除行，它们也能正常工作

imgthreshold=cv2.inRange(img,cv2.cv.Scalar(3,3,125),cv2.cv.Scalar(40,40,255),)

下一个，程序运行没有问题

Answer 1

您需要检查 VideoCapture::read 返回的状态功能。它返回一个 bool 标志，指示返回的图像是否有效。

import cv2
import numpy as np

try:

    cap = cv2.VideoCapture(0)

    while (cap.isOpened()):
        ret,img=cap.read()
        if not ret:
            continue

        cv2.imshow('output',img)
        img2=cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) 
        cv2.imshow('gray_scale',img2)
        imgthreshold=cv2.inRange(img,cv2.cv.Scalar(3,3,125),cv2.cv.Scalar(40,40,255),)
        cv2.imshow('thresholded',imgthreshold)

        k=cv2.waitKey(10)
        if k==27:
            break

    cap.release()
    cv2.destroyAllWindows()


except Exception as inst:

    cap.release()
    cv2.destroyAllWindows()
    print("Eroor!!")
    print(inst)
    raise