Could not load the QT platform "xcb" even though it was found.

[baskpann]

System information (version)

• OpenCV => 4.5.1.48
• Operating System / Platform => Ubuntu 20.10
• Compiler => Visual Studio 2020

Detailed description

I'm trying to run a face recognition algorithm in python3.8.5(in anaconda4.9 under a env base).
Once cv2.imshow() is encountered, I'm getting the following error.

qt.qpa.xcb: could not connect to display 
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/bas/anaconda3/lib/python3.8/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb.

Aborted (core dumped)

Also I tried executing the code with QT_DEBUG_PLUGINS=1 python3 my_script.py still provides the same error along with debug lines.

QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xz"
"Failed to extract plugin meta data from '/home/bas/anaconda3/bin/xz'" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzcat"
"Failed to extract plugin meta data from '/home/bas/anaconda3/bin/xz'" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzcmp"
QElfParser: '/home/bas/anaconda3/bin/xzdiff' is not an ELF object
"'/home/bas/anaconda3/bin/xzdiff' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzdec"
"Failed to extract plugin meta data from '/home/bas/anaconda3/bin/xzdec'" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzdiff"
QElfParser: '/home/bas/anaconda3/bin/xzdiff' is not an ELF object
"'/home/bas/anaconda3/bin/xzdiff' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzegrep"
QElfParser: '/home/bas/anaconda3/bin/xzgrep' is not an ELF object
"'/home/bas/anaconda3/bin/xzgrep' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzfgrep"
QElfParser: '/home/bas/anaconda3/bin/xzgrep' is not an ELF object
"'/home/bas/anaconda3/bin/xzgrep' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzgrep"
QElfParser: '/home/bas/anaconda3/bin/xzgrep' is not an ELF object
"'/home/bas/anaconda3/bin/xzgrep' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzless"
QElfParser: '/home/bas/anaconda3/bin/xzless' is not an ELF object
"'/home/bas/anaconda3/bin/xzless' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/xzmore"
QElfParser: '/home/bas/anaconda3/bin/xzmore' is not an ELF object
"'/home/bas/anaconda3/bin/xzmore' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/zstd"
"Failed to extract plugin meta data from '/home/bas/anaconda3/bin/zstd'" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/zstdcat"
"Failed to extract plugin meta data from '/home/bas/anaconda3/bin/zstd'" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/zstdgrep"
QElfParser: '/home/bas/anaconda3/bin/zstdgrep' is not an ELF object
"'/home/bas/anaconda3/bin/zstdgrep' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/zstdless"
QElfParser: '/home/bas/anaconda3/bin/zstdless' is not an ELF object (file too small)
"'/home/bas/anaconda3/bin/zstdless' is not an ELF object (file too small)" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/bin/zstdmt"
"Failed to extract plugin meta data from '/home/bas/anaconda3/bin/zstd'" 
         not a plugin
QFactoryLoader::QFactoryLoader() checking directory path "/home/bas/anaconda3/lib/python3.8/site-packages/cv2/qt/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/home/bas/anaconda3/lib/python3.8/site-packages/cv2/qt/plugins/platforms/libqxcb.so"
Found metadata in lib /home/bas/anaconda3/lib/python3.8/site-packages/cv2/qt/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "archreq": 0,
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 331520
}


Got keys from plugin meta data ("xcb")
QFactoryLoader::QFactoryLoader() checking directory path "/home/bas/anaconda3/bin/platforms" ...
loaded library "/home/bas/anaconda3/lib/python3.8/site-packages/cv2/qt/plugins/platforms/libqxcb.so"
qt.qpa.xcb: could not connect to display 
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/home/bas/anaconda3/lib/python3.8/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb.

Aborted (core dumped)

Steps to reproduce

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  forum.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc

[alalek]

Ensure what you don't have mess with Qt binaries from different locations in the process: #17827 (comment)

---

qt.qpa.xcb: could not connect to display

This message usually means wrong/missing configuration (usually missing DISPLAY due to terminal connection).

• Check other simple GUI applications (without OpenCV).
• Check other Qt based GUI applications (without OpenCV).

[baskpann]

Could you please brief about what should I do now? Should I reinstall opencv-python and opencv-contrib-python?

[alalek]

opencv-python and opencv-contrib-python

These packages are unofficial.
There are several compatibility issues, so you should check package's issues here first: https://github.com/skvark/opencv-python/issues

---

If you want report issue about OpenCV source code, then you need to build OpenCV from sources and confirm the problem.

---

Usage questions should go to Users OpenCV Q/A forum: https://forum.opencv.org/
This tracker is for issues and bugs that needs fix in OpenCV.

[shuang1204]

我在做目标检测的时候也遇到了相同的问题，请问您解决了嘛@Baskaran Panneerselvam baskpann