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Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found"

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  • A Offline
    A Offline
    alphaomega
    wrote on 12 Apr 2021, 16:27 last edited by alphaomega 4 Dec 2021, 16:31
    #20

    Replacing opencv-python with opencv-python-headless is one option. However, for some reasons if you want to keep the library, then you could add following lines after import cv2:

    import os, sys
    ci_build_and_not_headless = False
    try:
        from cv2.version import ci_build, headless
        ci_and_not_headless = ci_build and not headless
    except:
        pass
    if sys.platform.startswith("linux") and ci_and_not_headless:
        os.environ.pop("QT_QPA_PLATFORM_PLUGIN_PATH")
    if sys.platform.startswith("linux") and ci_and_not_headless:
        os.environ.pop("QT_QPA_FONTDIR")
    

    This is based on the cv2's init file . What it does is essentially removing environment variables that are added by the init file (This are only done at runtime and does not have permanent effect upon your system.)

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    1
    • P Pablo J. Rogina
      12 Apr 2021, 12:30

      @yashwant said in Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found":

      The problem arises only when I try to load python files with GUI.

      That's the point. You may need to check how to make a Docker container use the GUI of the host...

      Y Offline
      Y Offline
      yashwant
      wrote on 13 Apr 2021, 13:09 last edited by
      #21

      @Pablo-J-Rogina said in Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found":

      UI of the host..

      Yes that was my goal (docker with gui)! and above mentioned was my error when I try GUI on docker.! Anyway thanks!

      P 1 Reply Last reply 13 Apr 2021, 13:24
      0
      • Y yashwant
        13 Apr 2021, 13:09

        @Pablo-J-Rogina said in Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found":

        UI of the host..

        Yes that was my goal (docker with gui)! and above mentioned was my error when I try GUI on docker.! Anyway thanks!

        P Offline
        P Offline
        Pablo J. Rogina
        wrote on 13 Apr 2021, 13:24 last edited by
        #22

        @yashwant said in Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found":

        that was my goal (docker with gui)!

        Yes, I understand that. Please take into account that this issue is not related (or produced by) Qt itself so the solution might come from some other source(s), not only this forum

        Upvote the answer(s) that helped you solve the issue
        Use "Topic Tools" button to mark your post as Solved
        Add screenshots via postimage.org
        Don't ask support requests via chat/PM. Please use the forum so others can benefit from the solution in the future

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        0
        • R Offline
          R Offline
          redeyed
          wrote on 22 Apr 2021, 14:08 last edited by redeyed
          #23

          @jeremy_k said in Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found":

          worka

          Hello guys, so the problem is that import cv2 sets QT_* env vars.
          I came to this workaround, maybe it will help someone:

              import cv2
              for k, v in os.environ.items():
                  if k.startswith("QT_") and "cv2" in v:
                      del os.environ[k]
          
          A 1 Reply Last reply 16 Mar 2022, 09:19
          4
          • O Offline
            O Offline
            OBaladi
            wrote on 18 Sept 2021, 21:34 last edited by
            #24

            I solved the problem by downgrading the cv2 version, simply run
            python3 -m pip install opencv-contrib-python==4.1.0.25
            i used to have the 4.5.3.56

            1 Reply Last reply
            0
            • L lvlanson
              18 Sept 2020, 10:40

              Hey there,

              I am working on a big project, creating a GUI for working with convolutional neural networks. I need to use cv2 for image processing. For some reason I cannot import cv2 without my application creating an error.

              I am using pycharm as an IDE which is handling my virtual environment via pip. The librarys I use are the following:

              • PyQt5
              • pyqtchart
              • pyyaml
              • Pillow
              • tensorflow
              • distro
              • numpy
              • sklearn
              • pandas
              • opencv-python

              When I use cv2 I get the following error-message:

              qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "$HOME/Documents/gui_nn/venv/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, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.

              E Offline
              E Offline
              eyllanesc
              wrote on 18 Sept 2021, 21:37 last edited by
              #25

              @lvlanson Also see https://stackoverflow.com/a/68417901/6622587

              If you want me to help you develop some work then you can write to my email: e.yllanescucho@gmal.com.

              1 Reply Last reply
              0
              • T Offline
                T Offline
                Thiago Oliveira
                wrote on 27 Oct 2021, 22:08 last edited by
                #26

                @Hikari-Tretaki, muito obrigado por sua ajuda. Também consegui resolver o meu problema com sua dica.

                1 Reply Last reply
                0
                • R redeyed
                  22 Apr 2021, 14:08

                  @jeremy_k said in Using PyQt5 with opencv-python (cv2) causes error "could not load Qt platform plugin xcb even though it was found":

                  worka

                  Hello guys, so the problem is that import cv2 sets QT_* env vars.
                  I came to this workaround, maybe it will help someone:

                      import cv2
                      for k, v in os.environ.items():
                          if k.startswith("QT_") and "cv2" in v:
                              del os.environ[k]
                  
                  A Offline
                  A Offline
                  aria212019005
                  wrote on 16 Mar 2022, 09:19 last edited by
                  #27

                  @redeyed Thankyou, I was confused around installing

                  opencv-python
                  

                  and

                  opencv-python-headless
                  

                  before this. But it ends with "we need both libraries, and this"

                  1 Reply Last reply
                  0
                  • H Hikari Tretaki
                    10 Nov 2020, 21:12

                    @lvlanson I had the same problem. You can install headless opencv without GUI. Then it works.

                    pip install opencv-python-headless

                    V Offline
                    V Offline
                    Vijay Kumar
                    wrote on 15 May 2022, 03:07 last edited by
                    #28

                    @Hikari-Tretaki Thank you so much, installing opencv-python-headless fixed the issue

                    1 Reply Last reply
                    0
                    • H Hikari Tretaki
                      10 Nov 2020, 21:12

                      @lvlanson I had the same problem. You can install headless opencv without GUI. Then it works.

                      pip install opencv-python-headless

                      V Offline
                      V Offline
                      Vitor Dalla Vecchia
                      wrote on 18 Jul 2022, 09:55 last edited by
                      #29

                      @Hikari-Tretaki MAN, I LOVE YOU SO MUCH. THANKS!

                      1 Reply Last reply
                      0
                      • H Offline
                        H Offline
                        hitbuyi
                        wrote on 10 Oct 2022, 12:45 last edited by hitbuyi 10 Nov 2022, 01:39
                        #30

                        I also have this problem, my environments are
                        1, OS: ubuntu20.04
                        2, conda: 4.13
                        3, PyQt5: 5.15.2
                        4, local Qt5: 5.15.6
                        5, opencv- python 4.5.x

                        It really takes several days to find a solution, @jeremy_k gave almost the solution. I use PyQt5 + OpenCV-python on conda virtual environment,
                        summarize the solutions :

                        1, delete cv2/libqxcb.so, it works for pyqt5 which has its own version of Qt, but opencn-python doesn't work for other application which isn't relevant to PyQt5

                        2, if pyside2 is installed, pyside2 has its owen version of Qt, so add below code at the beginning of python program

                        ```
                        import PySide2
                        dirname = os.path.dirname(PySide2.__file__)
                        plugin_path = os.path.join(dirname, 'plugins', 'platforms')
                        os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = plugin_path
                        ```
                        

                        this solution works, at expense of intalling pyside2 which is 400M+

                        3, PyQt5 has its own version of Qt,similiar to above, add below code at the beginning of python program

                         ```
                        import PyQt5
                         dirname = os.path.dirname(PyQt5.__file__)
                         plugin_path = os.path.join(dirname, 'Qt5','plugins', 'platforms')
                         os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = plugin_path
                        
                        this soltuion is fine,
                        1 Reply Last reply
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