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Why does OpenCV cv2.imshow freeze after closing the window manually on Ubuntu?

I am working with OpenCV to display an image, and I encountered a problem on Ubuntu. The code works fine when I press the ESC key to exit the window, but if I manually click the "X" button to close the window, the program hangs and doesn’t proceed to the next steps (e.g., saving the image).

Here is my code:

import cv2

path = "/home/huanyizhiyuan/Softwares/VsCode_workspace/Python_workspace/image_solve/card1.jpg"

# Read the image
img = cv2.imread(path)
if img is None:
    raise FileNotFoundError(f"Image not found: {path}")

# Resize the image
img = cv2.resize(img, (1000, 800))

# Display the image
cv2.imshow('image', img)

# Wait for keyboard input
cv2.waitKey(0)

# Close the window
cv2.destroyWindow('image')

# Save the image
cv2.imwrite('new_image.jpg', img)

  • If I press ESC or any key while the window is open, the program exits as expected, and the image is saved correctly.

  • If I manually click the close button (the "X" button in the corner of the window), the program freezes. It does not save the image or exit gracefully.

Environment:

Operating System: Ubuntu 24.04.1 LTS

opencv-python: 4.10.0.84

Python: 3.12.7

What I’ve Tried:

  • I checked if the image path was correct and verified that the image is being displayed properly.
  • I attempted to use cv2.destroyWindow after cv2.waitKey(0), but the issue persists when clicking the close button.
Tags:

2

Answers


  1. 0

    My hunch its with compatibility across different systems. As you are using linux modify like this

    while True:
    key = cv2.waitKey(1) & 0xFF
    if key == 27 or cv2.getWindowProperty('image', cv2.WND_PROP_VISIBLE) < 1:
        break

    In a single Picture

    import cv2

path = "/home/huanyizhiyuan/Softwares/VsCode_workspace/Python_workspace/image_solve/card1.jpg"

# Read the image
img = cv2.imread(path)
if img is None:
    raise FileNotFoundError(f"Image not found: {path}")

# Resize the image
img = cv2.resize(img, (1000, 800))

# Display the image
cv2.imshow('image', img)

# Wait for key event or window close
while True:
    key = cv2.waitKey(1) & 0xFF
    if key == 27 or cv2.getWindowProperty('image', cv2.WND_PROP_VISIBLE) < 1:
        break

# Close the window
cv2.destroyAllWindows()

# Save the image
cv2.imwrite('new_image.jpg', img)

    The & 0xFF is used to extract the last 8 bits of the key code, which can help with compatibility across different systems

    Have a look – What's 0xFF for in cv2.waitKey(1)?

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  2. 0

    Why does OpenCV cv2.imshow freeze after closing the window manually on
    Ubuntu?

    The problem can be fixed.

    You must include another cv2.imshow since you are using cv2.destroyWindow('image').

    Snippet:

    # Display the image
cv2.imshow('image', img)
cv2.imshow('image_1', img)

    This will close button (the "X" button in the corner of the window). One at a time.

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