solved: Could not load the Qt platform plugin "xcb"

[ljubomirb]

I will leave here solution for a problem that I could not fix for days, hope it would help someone:
So, the error was:

QObject::moveToThread: Current thread (...) is not the object's thread (...).
Cannot move to target thread (...)
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/(...)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.

I was trying hard, but could not fix it. I was downloading literally hundreds of different packages, over and over again, trying all sorts of "hacks" found online, eventually trying anaconda, a massive download...
In the end, I don't know if that was the fix, because my system is about to be reinstalled after all of my "trying", BUT, after I wrote this in console:
export QT_QPA_PLATFORM=offscreen
everything worked.
Again, don't know if this was solution OR any of hundreds of packages installed, but try this first. If it works, maybe add this to Q&A .
Good luck!

[Tom94]

Hi there, thanks for reporting. This seems to have been a problem with the cv2 Python package and how it loops in Qt -- the instant-ngp codebase itself doesn't actually use Qt anywhere. Cheers!

[Ednaordinary]

Not sure exactly why, but this made it work for me! original error was

`qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/usr/local/lib/python3.9/dist-packages/opencv_python-4.5.5.64-py3.9-linux-x86_64.egg/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, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc.`

I agree this should be added to the Q&A, even if its a dependency and not instant-ngp that is causing trouble

[ben-milanko]

I ran into this issue, it seems to be from open-cv opencv/opencv-python#46.

Using open-cv-python-headless instead seems to work for me: https://stackoverflow.com/a/72090539

pip uninstall opencv-python
pip install opencv-python-headless

[abnormal749]

But it now cannot use cv2.imshow after install opencv-python-headless

cv2.error: OpenCV(4.8.1) /io/opencv/modules/highgui/src/window.cpp:1272: error: (-2:Unspecified error) The function is
not implemented. Rebuild the library with Windows, GTK+ 2.x or Cocoa support. If you are on Ubuntu or Debian, install
libgtk2.0-dev and pkg-config, then re-run cmake or configure script in function 'cvShowImage'

[LunaRose12]

Thank you for taking the time to post that for the idiots out there trying to learn computers as in myself

[luisjuarez099]

Thank you for your response. Fortunately, my boss didn't dismiss me. 🙅‍♂️ 👀

[BoZhiStudying233]

@abnormal749 I met the same problem. Have you solved it? I solved this problem by isolating the two programs via a virtual environment.

[joyehsu]

Works for me too, thanks very much~
My system is Win10 + WSL2

[MashyBasker]

Hi, were you using a virtual environment for installing python packages? I was facing the exact same problem and 30 mins later I realized my virtual environment was not activated.

[hoods-py]

i am using a virtual environment
and i'm having the same issue

[yojetsharma]

I am trying to run rstudio in a conda environment on an institutional server and I am getting the following error:

(rstudio) [yojetsharma@pakeeza ~]$ rstudio
TTY detected. Printing informational message about logging configuration. Logging configuration loaded from '/etc/rstudio/logging.conf'. Logging to '/home/praghu/yojetsharma/.local/share/rstudio/log/rdesktop.log'.
No protocol specified
Fontconfig warning: ignoring UTF-8: not a valid region tag
WebEngineContext used before QtWebEngine::initialize() or OpenGL context creation failed.
This plugin does not support propagateSizeHints()
This plugin does not support raise()
Failed to create OpenGL context for format QSurfaceFormat(version 2.0, options QFlags<QSurfaceFormat::FormatOption>(), depthBufferSize 24, redBufferSize -1, greenBufferSize -1, blueBufferSize -1, alphaBufferSize -1, stencilBufferSize 8, samples 0, swapBehavior QSurfaceFormat::DefaultSwapBehavior, swapInterval 1, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::NoProfile) 
Aborted
[5851:5851:0100/000000.063786:ERROR:zygote_linux.cc(607)] Zygote could not fork: process_type renderer numfds 3 child_pid -1
[5851:5851:0100/000000.063868:ERROR:zygote_linux.cc(639)] write: Broken pipe (32)

[kassbohm]

Worked also for me on Linux Mint.

[Kupofty]

Also worked for me on Ubuntu20 after the last update of QtCreator, thanks a lot !

[montanaviking]

running Ubuntu 22.04. Sadly installing opencv-python-headless did not work for me

[The-R4V3N]

Thanks this finally worked

[fattypiggy]

This one works for me, thanks a lot.

[israelins85]

To solve this just run:

sudo apt-get install libxcb-xinerama0

[aino-gautam]

This seems to be the real solution for Ubuntu. There should be a way in github to highlight this as a solution :)

[amitpd1]

worked for ubuntu

[ArunChamiyappan]

The same here, Thank you

[Lijuming33]

ubuntu 2204，有用！

[xyf9474]

牛逼

[Jalagarto]

https://stackoverflow.com/a/68058308/9033534 - first answer

for pyqt6 in ubuntu 20.04, following spell in forum linked above, solved the problem for me sudo apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev
Author: harish
Oct 21, 2021

[criogenox]

It works!!!! Thanks, my friend.

[Drone944]

Thanks Bro, it works, saved me a lot of time.

[fvydjt]

This works for me.

[interval1066]

Thanks Jalagarto, your apt install chain worked for me as well. I know a lot of AI tools as well as everything else uses python, it seems, but I resent having to install a bunch of junk I don't use just to get qtcreator working. I didn't ask the updater to install this copilot client on my qt stack.. especially anything made with python. I really resent this.

[mahdi3100]

thanks mate

[tomnattle]

sudo apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev

this work for me , i use qt in docker

[tomnattle]

168  pip3 install labelImg
  169  labelImg
  170  export DISPLAY=192.168.56.1:0.0
  171  labelImg
  172  export QT_DEBUG_PLUGINS=1
  173  labelImg
  174  apt-get install libxcb-xinerama0
  175  labelImg
  176  cd /home/brainiac/Qt/Tools/QtCreator/lib/Qt/plugins/platforms/
  177  labelImg
  178  ldd /usr/lib/qt/plugins/platforms/libqxcb.so
  179  pip uninstall opencv-python
  180  pip install opencv-python-headless
  181  labelImg
  182* pip uninstall opencv-python-
  183  pip install opencv-python
  184  sudo apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev    
  185  apt-get install '^libxcb.*-dev' libx11-xcb-dev libglu1-mesa-dev libxrender-dev libxi-dev libxkbcommon-dev libxkbcommon-x11-dev
  186  labelImg
  187  history

[darkrams98]

This worked for me : ubuntu 22.04

[JoshuaTokisaki]

This worked for me: ubuntu 22.04 WSL 2

[jinhoishere]

This worked for me : Ubuntu WSL 2 22.04.4 LTS

[zym198098]

我用wsl2 ubuntu 22.04 有用。多谢

[bhjolly]

export QT_QPA_PLATFORM=offscreen

I ran across this thread trying to diagnose the same issue trying to run Agisoft Metashape on a GPU-equipped-but-headless server. Exporting that environment variable fixed it.

[satpalsr]

This helped. Thanks. I am runnning in ec2-instance.

[maple367]

This works in WSL2 debian with conda environment. Thanks.

[BryceWayne]

This worked Ubuntu+WSL+Conda+Python3.10

[AmrinKareem]

This worked for me in Linux with conda environment. Thank you!

[m1ndcrash]

Oh my god. 4 hours. This one saved me. PS training nerf

[Petros626]

My solutions I've tested on my code.

If you get Could not load the Qt platform plugin "xcb"after import cv2
fix 1: use os.environ.pop("QT_QPA_PLATFORM_PLUGIN_PATH") in code
fix 2: try pip install opencv-python-headless (without GUI)
fix 3: delete the libqxcb from "/home/usernamexyz/.local/lib/python3.9/site-packages/cv2/qt/plugins/platforms

[Daa98]

fix 3: delete the libqxcb from "/home/usernamexyz/.local/lib/python3.9/site-packages/cv2/qt/plugins/platforms

is useful

Thanks

[HasarinduPerera]

Thanks, this is useful indeed!

[DatleUNL]

Fix 1 worked for my Kinz library that uses opencv-contrib-python. Thanks!

[WEIIEW97]

Fix 1 solved mine. Thanks a lot!

[masuraoru]

In my case it was conflict in Qt installation on the system with the Qt that is shipped with OpenCV. Solved on Ubuntu 22.04 Desktop by removing opencv-python:
pip3 uninstall opencv-python
and reinstaing with --no-binary option:
pip3 install --no-binary opencv-python opencv-python
Warning: opencv-python compiling may take some time.

[AnshuDFKI]

This is the only solution which worked for me. Thank You

[xmlyqing00]

This is the most decent way to solve this problem.

[abnormal749]

It's the only solution really helps for my program with qt and cv.imshow

[Lwy-1998]

This is really help！！！

[JasOleander]

You saved my day. This is the only answer for both qt and cv2 errors.
Thank you so much. :)

[ljjTYJR]

My problem:

qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" 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: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

I use the command:

export DISPLAY=:0

works for me...

[eneserdo]

Worked for WSL, thanks

[tymho]

Worked for me! I think this might be related to SSH?

[trojanof]

Thanks for solution! export QT_QPA_PLATFORM=offscreen works for me! I had an issue running streamlit app on a server with ubuntu and music21 python module. I had musescore installed there but faced the qt related problem when trying to display music scores. Setting that variable solved my problem.

[opticalor]

Thats not work,but i use export QT_QPA_PLATFORM_PLUGIN_PATH=/path/to/your/qt/directory/plugins,is run now.(dont forget unset QT_QPA_PLATFORM if you accept before this)

[zzhuolun]

I found this answer that showed how to narrow down and locate the problem very helpful.

In my case, installing the specific missing libraries AND reinstalling PyQt5 solved the problem.

[Truthuleave]

No error appears through export QT_DEBUG_PLUGINS=1 when in conda venv.
Quitting from conda venv works for me~

[leung1010]

I will leave here solution for a problem that I could not fix for days, hope it would help someone: So, the error was:

QObject::moveToThread: Current thread (...) is not the object's thread (...).
Cannot move to target thread (...)
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/(...)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.

I was trying hard, but could not fix it. I was downloading literally hundreds of different packages, over and over again, trying all sorts of "hacks" found online, eventually trying anaconda, a massive download... In the end, I don't know if that was the fix, because my system is about to be reinstalled after all of my "trying", BUT, after I wrote this in console: export QT_QPA_PLATFORM=offscreen everything worked. Again, don't know if this was solution OR any of hundreds of packages installed, but try this first. If it works, maybe add this to Q&A . Good luck!

This answer just turns off the screen. Maybe this cmd could help you guys fix the issue. sudo apt install libxcb-xinerama0

[sajadalipour]

It works for me after installing opencv-contrib-python-headless

[1850298154]

您的邮件已收到！祝工作顺利！

[eavelardev]

export XDG_CURRENT_DESKTOP=Unity could work for Ubuntu, but I have an undesired behavior where PyQt windows and dialogs aren't centered

[CrikersPL]

flatpak override --user --env=QT_QPA_PLATFORM=wayland org.kde.dolphin
(org.kde.dolphin) in my case

Worked for me

[stevenlafl]

I got this error when loading a QT6 program that didn't ship the required QT6 plugins. In particular, obs under rockchip repository for aarch64. Instead, the plugin package installed was a QT5 one, so essentially it wouldn't find any DDE plugins.

apt-get install qt6-qpa-plugins

will install the libqxcb.so file required along with libqeglfs.so, libqminimalegl.so, libqoffscreen.so, libqvnc.so, libqlinuxfb.so, libqminimal.so and libqvkkhrdisplay.so.