Unable to Capture an Image using OpenCV on BeagleBone Black Wireless (Debian 10.3)

General Discussion
1

I am running Python 3.7.3 on Debian 10 Buster, and I am trying to capture one image and save it using opencv-python and a Logitech C270 Webcam.

I am trying to achieve this using the simple program below:

import cv2

cap = cv2.VideoCapture(0) # video capture source camera (Here webcam of laptop) 
ret,frame = cap.read() # return a single frame in variable `frame`
cv2.imwrite('images/c1.png',frame)
      
cap.release()

when I run this code, I keep on getting !_img.empty() in function 'imwrite'. My webcam has a little indicator light, and when the code runs it turns on, so I am confused as to why the program isn’t capturing the image.

Troubleshooting steps taken:
I tested my webcam using guvcview, and it works just fine. A v2l2-ctl --list-devices command returns: /dev/video0 /dev/video1

Thanks in advance for your help.

2

Hello,

I am by far a OpenCV master of any sort but…

  1. Have you tried to manually add the file and then run the source?
  2. touch c1.png && python3 YourFile.py

Please let me know if that works.

Seth

3

Update: The resulting warning from the terminal prompted me to Google it, and I found this thread:

https://forum.opencv.org/t/videoio-v4l2-dev-video0-select-timeout/8822

I added this line of code before ret,frame = cap.read():

camera.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M', 'J', 'P', 'G'))

and now the program works. Thanks!

1 Like
4

Thanks for your suggestions.
1.) I ran the code below, manually providing an image:

import cv2

img = cv2.imread("sample.png", cv2.IMREAD_COLOR)

cv2.imshow("image", img)

cv2.imwrite('test.png', img)
cv2.waitKey(0)

cv2.destroyAllWindows()

The program was able to read the image, show it in a window, and save it with a different name. This file that was saved contained the original image with no issues.

2.) When I ran this in the terminal using the original program I asked about in this post, I got the following in the terminal:

[WARN:0] VIDEOIO(V4L2:/dev/video0): select() timeout.

The image “c1.png” that was produced after running your command contained no image data when I tried to open it. I still saw the light on my Webcam turn on, but again no image data could be obtained from it.