openCV:qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "user" even though it was found.

revathib

Hi,

We developed a program which displays images from a camera using cv2 library(imshow). This program is running fine when we executing it through terminal . But, when we tried to execute on bootup using crontab we getting the below error

qt.qpa.xcb: could not connect to display 
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/opt/MVS/Samples/64/Python/GrabImage/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.

Aborted (core dumped)

we tried to debug our program using export QT_DEBUG_PLUGINS=1, below is the output

QFactoryLoader::QFactoryLoader() checking directory path "/opt/MVS/Samples/64/Python/GrabImage/cv2/qt/plugins" ...
QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin" ...

<Deleted few messages like the below one due to character limit>
<QElfParser: '/usr/bin/2to3-2.7' is not an ELF object
"'/usr/bin/2to3-2.7' is not an ELF object" 
         not a plugin
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/2to3-3.5"
QElfParser: '/usr/bin/2to3-3.5' is not an ELF object
"'/usr/bin/2to3-3.5' is not an ELF object" 
         not a plugin>
QFactoryLoader::QFactoryLoader() checking directory path "/opt/MVS/Samples/64/Python/GrabImage/cv2/qt/plugins/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/opt/MVS/Samples/64/Python/GrabImage/cv2/qt/plugins/platforms/libqxcb.so"
Found metadata in lib /opt/MVS/Samples/64/Python/GrabImage/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 "/usr/bin/platforms" ...
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqeglfs.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqeglfs.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "eglfs"
        ]
    },
    "className": "QEglFSIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("eglfs")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqlinuxfb.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqlinuxfb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "linuxfb"
        ]
    },
    "className": "QLinuxFbIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("linuxfb")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqminimal.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqminimal.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimal"
        ]
    },
    "className": "QMinimalIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("minimal")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqminimalegl.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqminimalegl.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "minimalegl"
        ]
    },
    "className": "QMinimalEglIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("minimalegl")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqoffscreen.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqoffscreen.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "offscreen"
        ]
    },
    "className": "QOffscreenIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("offscreen")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqvnc.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqvnc.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "vnc"
        ]
    },
    "className": "QVncIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("vnc")
QFactoryLoader::QFactoryLoader() looking at "/usr/bin/platforms/libqxcb.so"
Found metadata in lib /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqxcb.so, metadata=
{
    "IID": "org.qt-project.Qt.QPA.QPlatformIntegrationFactoryInterface.5.3",
    "MetaData": {
        "Keys": [
            "xcb"
        ]
    },
    "className": "QXcbIntegrationPlugin",
    "debug": false,
    "version": 329989
}
Got keys from plugin meta data ("xcb")
loaded library "/opt/MVS/Samples/64/Python/GrabImage/cv2/qt/plugins/platforms/libqxcb.so"

Can you let us know what is causing this issue and how to resolve it,we want our python program to run on bootup?

jsulm

@revathib said in openCV:qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "user" even though it was found.:

But, when we tried to execute on bootup using crontab we getting the below error

Is the X server running when the app is started?