cv2.imshow(img) is crashing the kernel

[epignatelli]

As per title cv2.imshow(img) is crashing the server.

If we avoid cv2.waitForKey() and cv2.closeAllWindows(), and keep the windows open, the notebook will continue running.

Python version:

Python 3.5.6 |Anaconda custom (64-bit)| (default, Aug 26 2018, 16:05:27) [MSC v.1900 64 bit (AMD64)]

Kernel about:

Python 3.5.5 |Anaconda, Inc.| (default, Mar  9 2018, 12:39:44) [MSC v.1900 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information
IPython 6.2.1 -- An enhanced Interactive Python. Type '?' for help.

To reproduce: (coming)

[ah3243]

I'm having a similar problem, the imshow() window is displayed it crashes when it would normally be destroyed. Even it's the last of 10 windows created and destroyed in a loop the last one will always freeze as the program moves on. Gives no errors when running identical code in a terminal.

OSx Mojave 10.14.2
Python 3.5
opencv-python 4.0.0.12

[nvt-ak]

You can use this solution if you're using google colab:
from google.colab.patches import cv2_imshow
cv2_imshow(img)
It works fine!

[mitesh98]

image is appearing too big.I use below code
import matplotlib.pyplot as plt
plt.figure(figsize=(18,18))
plt.imshow(image)
plt.axis('off')
plt.show()

[Oshana]

how to convert this to cv2_imshow?

cv2.imshow('object detection', cv2.resize(image_np, (800, 600)))

[shivam-kotwalia]

@Oshana just say -
cv2_imshow(cv2.resize(image_np, (800, 600)))
cv2_imshow only takes one input parameter, https://github.com/googlecolab/colabtools/blob/8708337447efdef2732cca9764ede400da6c051f/google/colab/patches/__init__.py#L14

[epignatelli]

You can also consider using matplotlib rather than IPython.display, although, I would not recommend to mix the two.

import matplotlib.pyplot as plt
import cv2
def cv2_imshow(a, **kwargs):
    a = a.clip(0, 255).astype('uint8')
    # cv2 stores colors as BGR; convert to RGB
    if a.ndim == 3:
        if a.shape[2] == 4:
            a = cv2.cvtColor(a, cv2.COLOR_BGRA2RGBA)
        else:
            a = cv2.cvtColor(a, cv2.COLOR_BGR2RGB)

    return plt.imshow(a, **kwargs)

[kyteinsky]

image is appearing too big.I use below code
import matplotlib.pyplot as plt
plt.figure(figsize=(18,18))
plt.imshow(image)
plt.axis('off')
plt.show()

You can use this insted:
plt.figure(figsize=(10,18))
for resizing the image.

[kyteinsky]

This fix also works for opening image using imshow() function from OpenCV::

cv.namedWindow(winname='my')
while True:
cv.imshow('my',img)
if cv.waitKey(1) & 0xFF == 27:
break
cv.destroyAllWindows()

[PrasadNR]

You can use this solution if you're using google colab:
from google.colab.patches import cv2_imshow
cv2_imshow(img)
It works fine!

This is just showing some black blank image.

[antopolskiy]

Copying the mentioned function cv2_imshow from colabtools and using it locally worked well for me. It displays the image inline.

[kilicsedat]

This approach worked for me, too.

[ozrite]

hi guys, here is the solution of the problem.

If you are using a 64-bit machine, you will have to modify
k = cv2.waitKey(0)
line as follows :
k = cv2.waitKey(0) & 0xFF

The full solution is like this:

```
cv2.imshow('image',img)
k = cv2.waitKey(0) & 0xFF
if k == 27:         # wait for ESC key to exit
    cv2.destroyAllWindows()

Now the kernel will not be stuck or crash. You just need to press esc to quit.

[KrishnaChaitanya-Gopaluni]

You can also consider using matplotlib rather than IPython.display, although, I would not recommend to mix the two.

import matplotlib.pyplot as plt
import cv2
def cv2_imshow(a, **kwargs):
    a = a.clip(0, 255).astype('uint8')
    # cv2 stores colors as BGR; convert to RGB
    if a.ndim == 3:
        if a.shape[2] == 4:
            a = cv2.cvtColor(a, cv2.COLOR_BGRA2RGBA)
        else:
            a = cv2.cvtColor(a, cv2.COLOR_BGR2RGB)

    return plt.imshow(a, **kwargs)

Thank you.