CODEWITHSUNDEEP
pythonopencvwebcam
Akanksha Dangi
Akanksha Dangi

Reputation: 51

Webcam + Open CV Python | Black screen

I am using the code below, but I get a black image. Could you please help me rectify the error?

import cv2
import numpy as np
c = cv2.VideoCapture(0)

while(1):
    _,f = c.read()
    cv2.imshow('e2',f)
    if cv2.waitKey(5)==27:
        break
cv2.destroyAllWindows()

Upvotes: 4

Views: 21421

Answers (8)

user3588569
user3588569

Reputation:

I faced the same issue after many calls with:

cap = cv2.VideoCapture(0)

and it solved when I changed the index to 1 :

cap = cv2.VideoCapture(1)

Upvotes: 0

TheBaz86
TheBaz86

Reputation: 11

In my case just disabling Kaspersy has solved the problem.

Upvotes: -1

Lulosoul Nofemele
Lulosoul Nofemele

Reputation: 1

Try put -0 on the index and pause any antivirus running

import cv2
import numpy as np

cap = cv2.VideoCapture(-0)
cap.set(3,640)
cap.set(3,480)

while(True):
    success, img = cap.read()

    cv2.imshow('frame',img)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

Upvotes: 0

Praveen
Praveen

Reputation: 73

Update: See github.com/opencv/opencv/pull/11880 and linked conversations, only few backends support -1 as index.

Although this is an old post, this answer can help people who are still facing the same problem. If you have a single webcam but it renders all black, use cv2.VideoCapture(-1). This will get you the working camera.

Upvotes: 6

sefiks
sefiks

Reputation: 1630

I've faced with same problem. Updating neither opencv nor webcam driver works. I am using kaspersky as antivirus. When I disable the kaspersky, then black output problem solved.

BTW, I can see the running .py file in kaspersky console > reports > host intrusion prevention. It reports application privilege control rule triggered - application: myfile.py, result: blocked: access to video capturing devices

Upvotes: 4

Durodola Opemipo
Durodola Opemipo

Reputation: 409

This worked for me: I did a pip install imutils. Imutils is a library with series of convenience functions to make basic image processing functions such as translation, rotation, resizing, skeletonization, displaying Matplotlib images, sorting contours, detecting edges, and much more easier with OpenCV and both Python 2.7 and Python 3.

import cv2
import imutils

cap = cv2.VideoCapture(0)  # video capture source camera (Here webcam of laptop)
ret, frame = cap.read()  # return a single frame in variable `frame`


while (True):
    # gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    (grabbed, frame) = cap.read()
    frame = imutils.resize(frame, width=400)
    cv2.imshow('img1', frame)  # display the captured image
    if cv2.waitKey(1) & 0xFF == ord('q'):  # save on pressing 'y'
        cv2.imwrite('capture.png', frame)
        cv2.destroyAllWindows()
        break

cap.release()

Upvotes: 0

Amit kumar
Amit kumar

Reputation: 91

Just change cv2.waitKey(0) to cv2.waitKey(30) and this issue will be resolved.

Upvotes: 5

Aphire
Aphire

Reputation: 1652

Try this:

import cv2
import numpy as np

cap = cv2.VideoCapture(0)

while(True):
    ret, frame = cap.read()

    cv2.imshow('frame',frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

Upvotes: 1

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