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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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  • Y yashwant

    I am just trying to open a python GUI(which opens fine in windows 10) using docker setup. I did install docker for windows using the standard procedure. And I can load the python codes (without .ui - python files without GUI) into the container without any problem. The problem arises only when I try to load python files with GUI.

    Pablo J. RoginaP Offline
    Pablo J. RoginaP Offline
    Pablo J. Rogina
    wrote on last edited by
    #19

    @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...

    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

    Y 1 Reply Last reply
    0
    • A Offline
      A Offline
      alphaomega
      wrote on last edited by alphaomega
      #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.)

      1 Reply Last reply
      1
      • Pablo J. RoginaP Pablo J. Rogina

        @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 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!

        Pablo J. RoginaP 1 Reply Last reply
        0
        • Y yashwant

          @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!

          Pablo J. RoginaP Offline
          Pablo J. RoginaP Offline
          Pablo J. Rogina
          wrote on 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

          1 Reply Last reply
          0
          • R Offline
            R Offline
            redeyed
            wrote on 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
            4
            • O Offline
              O Offline
              OBaladi
              wrote on 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

                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.

                eyllanescE Offline
                eyllanescE Offline
                eyllanesc
                wrote on 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 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

                    @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 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

                      @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 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

                        @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 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 last edited by hitbuyi
                          #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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