cv2.videocapture.read()不返回一个numpy数组 [英] cv2.videocapture.read() does not return a numpy array

问题描述

我有这段代码试图从树莓派上的网络摄像头捕获一个帧，并将其另存为图像.我使用的是opencv 2，但是在运行代码时出现奇怪的错误.

I have this code trying to capture a frame from my webcam on raspberry pi, and saving it as an image. I use opencv 2, but I get strange errors when I run the code..

import time
import sys
from subprocess import call
import cv2

cam = cv2.VideoCapture()

while True:
        cam.open(-1)
        image = cam.read()
        cv2.imwrite("current.jpeg",image)
        time.sleep(10);

这是程序返回的内容:

VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument
VIDIOC_QUERYMENU: Invalid argument

Traceback (most recent call last):
  File "kvamskogen.py", line 18, in <module>
    cv2.imwrite("current.jpeg",image)
TypeError: <unknown> is not a numpy array

这是怎么了?

推荐答案

从VideoCapture读取(cam.read())将返回元组(return value, image).对于第一个项目，您检查是否读取成功，如果读取成功，则继续使用返回的image.

Reading (cam.read()) from a VideoCapture returns a tuple (return value, image). With the first item you check wether the reading was successful, and if it was then you proceed to use the returned image.

此文档记录在 http://docs.opencv.org/modules/highgui/doc/reading_and_writing_images_and_video .html

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