opencv.imshow will cause jupyter notebook crash

Question

I check other question on google or stackoverflow, they are talking about run cv2.imshow in script, but my code run in jupyter notebook.

Here is my configuration:

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Answer 1

I am not sure if you can open a window from Jupyter Notebook. cv2.imshow expects a waitKey which doesn't work in Jupyter.

Here is what I have done (using OpenCV 3.3):

from IPython.display import display, HTML
import cv2
import base64

def imshow(name, imageArray):
     _, png = cv2.imencode('.png', imageArray)
     encoded = base64.b64encode(png)
     return HTML(data='''<img alt="{0}" src="data:image/png;base64, {1}"/>'''.format(name, encoded.decode('ascii')))

img = cv2.imread('./media/baboon.jpg',cv2.IMREAD_COLOR)
imshow('baboon', img)

If you don't need to use cv2, just:

from IPython.display import Image
Image('./media/baboon.jpg')

Answer 2

The following code works fine in Jupyter to show one image

%matplotlib inline
import cv2
from matplotlib import pyplot as plt
cap = cv2.VideoCapture(videoFName)
ret, image = cap.read()
image=cv2.resize(image,None,fx=0.25,fy=0.25,interpolation=cv2.INTER_AREA)
plt.imshow(image)
plt.show()

If you want to show the video instead of an image in a separate window, use the following code:

import cv2
cap = cv2.VideoCapture(videoFName)
while cap.isOpened():
    ret, image = cap.read()
    image=cv2.resize(image,None,fx=0.25,fy=0.25,interpolation=cv2.INTER_AREA)
    cv2.imshow('image',image)

    k = cv2.waitKey(30) & 0xff # press ESC to exit
    if k == 27 or cv2.getWindowProperty('image', 0)<0:
        break
cv2.destroyAllWindows()
cap.release()

Make sure the window name match, otherwise it will not work. In this case I use 'image' as window name.