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Qt image resource is null

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  • Christian EhrlicherC Christian Ehrlicher

    Do you actually add the resource to your application?

    K Offline
    K Offline
    Kelenyche
    wrote on last edited by
    #4

    @Christian-Ehrlicher
    Yes, it's in a folder, available to the application. Like I mentioned, if I change the filepath or name in the code, it throws an error saying it can't find it - so it does seem to be finding it but isn't reading it somehow?

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    • SGaistS SGaist

      Hi,

      Can you show the structure of your project ?

      Did you try to load the file from the disk just to check that it loads properly ?

      K Offline
      K Offline
      Kelenyche
      wrote on last edited by
      #5

      @SGaist

      My project structure is:

      project
      -headers
      *.h
      -sources
      -main.cpp
      *.cpp (file that calls the image is in here)
      -extra
      -resources.qrc
      -images
      -scribble.jpg

      I think that's all the relevant info on my structure. What's a way to load the file from disk to see that my program sees it?

      K 1 Reply Last reply
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      • K Kelenyche

        @SGaist

        My project structure is:

        project
        -headers
        *.h
        -sources
        -main.cpp
        *.cpp (file that calls the image is in here)
        -extra
        -resources.qrc
        -images
        -scribble.jpg

        I think that's all the relevant info on my structure. What's a way to load the file from disk to see that my program sees it?

        K Offline
        K Offline
        Kelenyche
        wrote on last edited by
        #6

        @Kelenyche said in Qt image resource is null:

        @SGaist

        My project structure is:

        project
        -headers
        *.h
        -sources
        -main.cpp
        *.cpp (file that calls the image is in here)
        -extra
        -resources.qrc
        -images
        -scribble.jpg

        I think that's all the relevant info on my structure. What's a way to load the file from disk to see that my program sees it?

        Oh none of my nice spacing came through lol.

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        • SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #7

          Try editing it with coding tags.

          For the test, just use the full path to the file on the disk.

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          • K Offline
            K Offline
            Kelenyche
            wrote on last edited by
            #8
             project
                 headers
                     *.h
                 sources
                     main.cpp
                     *.cpp (file that calls the image is in here)
                 extra
                     resources.qrc
                     images
                         scribble.jpg
            

            I'll try the full disk path.

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            0
            • K Offline
              K Offline
              Kelenyche
              wrote on last edited by
              #9

              Full disk path is also coming up with a null image.

              Fwiw, I'm doing this on a raspberry pi, is it possible there's some permission problems?

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #10

                Next step: start your application with the QT_DEBUG_PLUGINS environment variable set to 1 to see what's going on with the image plugins.

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                • SGaistS SGaist

                  Next step: start your application with the QT_DEBUG_PLUGINS environment variable set to 1 to see what's going on with the image plugins.

                  K Offline
                  K Offline
                  Kelenyche
                  wrote on last edited by
                  #11

                  @SGaist
                  Where should this be set? I'm also doing all this off the command line, no qt creator. Would this be in the .pro file, or an argument called with qmake program.pro?

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                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #12

                    On the command line directly

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                    • K Offline
                      K Offline
                      Kelenyche
                      wrote on last edited by
                      #13

                      Ah, ok so I ran:
                      QT_DEBUG_PLUGINS=1 ./program
                      and it dumped a bunch of info. I'm not seeing any problems or failures in here...?

                      Got keys from plugin meta data ("ico", "cur")
                      QFactoryLoader::QFactoryLoader() looking at "/usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so"
                      Found metadata in lib /usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so, metadata=
                      {
                          "IID": "org.qt-project.Qt.QImageIOHandlerFactoryInterface",
                          "MetaData": {
                              "Keys": [
                                  "jpg",
                                  "jpeg"
                              ],
                              "MimeTypes": [
                                  "image/jpeg",
                                  "image/jpeg"
                              ]
                          },
                          "className": "QJpegPlugin",
                          "debug": false,
                          "version": 330499
                      }
                      

                      This seems like the most relevant portion, but again it seems to have succeeded in recognizing jpgs, so I don't see a problem. Let me know if there's anything else I should be looking for. I'm not seeing parts that are specific to my code, it just looks like Qt's background stuff for loading certain plugins.

                      K 1 Reply Last reply
                      0
                      • K Kelenyche

                        Ah, ok so I ran:
                        QT_DEBUG_PLUGINS=1 ./program
                        and it dumped a bunch of info. I'm not seeing any problems or failures in here...?

                        Got keys from plugin meta data ("ico", "cur")
                        QFactoryLoader::QFactoryLoader() looking at "/usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so"
                        Found metadata in lib /usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so, metadata=
                        {
                            "IID": "org.qt-project.Qt.QImageIOHandlerFactoryInterface",
                            "MetaData": {
                                "Keys": [
                                    "jpg",
                                    "jpeg"
                                ],
                                "MimeTypes": [
                                    "image/jpeg",
                                    "image/jpeg"
                                ]
                            },
                            "className": "QJpegPlugin",
                            "debug": false,
                            "version": 330499
                        }
                        

                        This seems like the most relevant portion, but again it seems to have succeeded in recognizing jpgs, so I don't see a problem. Let me know if there's anything else I should be looking for. I'm not seeing parts that are specific to my code, it just looks like Qt's background stuff for loading certain plugins.

                        K Offline
                        K Offline
                        Kelenyche
                        wrote on last edited by
                        #14

                        @Kelenyche said in Qt image resource is null:

                        Ah, ok so I ran:
                        QT_DEBUG_PLUGINS=1 ./program
                        and it dumped a bunch of info. I'm not seeing any problems or failures in here...?

                        Got keys from plugin meta data ("ico", "cur")
                        QFactoryLoader::QFactoryLoader() looking at "/usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so"
                        Found metadata in lib /usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so, metadata=
                        {
                            "IID": "org.qt-project.Qt.QImageIOHandlerFactoryInterface",
                            "MetaData": {
                                "Keys": [
                                    "jpg",
                                    "jpeg"
                                ],
                                "MimeTypes": [
                                    "image/jpeg",
                                    "image/jpeg"
                                ]
                            },
                            "className": "QJpegPlugin",
                            "debug": false,
                            "version": 330499
                        }
                        

                        This seems like the most relevant portion, but again it seems to have succeeded in recognizing jpgs, so I don't see a problem. Let me know if there's anything else I should be looking for. I'm not seeing parts that are specific to my code, it just looks like Qt's background stuff for loading certain plugins.

                        This chunk also seems like it recognized that it needs jpgs:

                        Got keys from plugin meta data ("svg", "svgz")
                        QFactoryLoader::QFactoryLoader() checking directory path "/home/pi/Desktop/program/imageformats" ...
                        loaded library "/usr/lib/aarch64-linux-gnu/qt5/plugins/imageformats/libqjpeg.so"
                        QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/aarch64-linux-gnu/qt5/plugins/accessible" ...
                        QFactoryLoader::QFactoryLoader() checking directory path "/home/pi/Desktop/program/accessible" ...
                        QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/aarch64-linux-gnu/qt5/plugins/accessiblebridge" ...
                        QFactoryLoader::QFactoryLoader() checking directory path "/home/pi/Desktop/program/accessiblebridge" ...
                        QFactoryLoader::QFactoryLoader() checking directory path "/usr/lib/aarch64-linux-gnu/qt5/plugins/iconengines" ...
                        QFactoryLoader::QFactoryLoader() looking at "/usr/lib/aarch64-linux-gnu/qt5/plugins/iconengines/libqsvgicon.so"
                        Found metadata in lib /usr/lib/aarch64-linux-gnu/qt5/plugins/iconengines/libqsvgicon.so, metadata=
                        {
                            "IID": "org.qt-project.Qt.QIconEngineFactoryInterface",
                            "MetaData": {
                                "Keys": [
                                    "svg",
                                    "svgz",
                                    "svg.gz"
                                ]
                            },
                            "className": "QSvgIconPlugin",
                            "debug": false,
                            "version": 330499
                        }
                        
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                        • SGaistS Offline
                          SGaistS Offline
                          SGaist
                          Lifetime Qt Champion
                          wrote on last edited by
                          #15

                          That part looks good.
                          And I am guessing that it also says somewhere that the plugin was successfully loaded ?

                          The next step: did you check that the file is a valid jpeg ?

                          Interested in AI ? www.idiap.ch
                          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                          • K Offline
                            K Offline
                            Kelenyche
                            wrote on last edited by
                            #16

                            Yea I can't find any problems in that debug info, no failures or anything.

                            I actually created the jpg in paint, it's literally just some scribbles. I have a .png I've been trying to use but no luck, so I wanted to try a different file type, with a differently formatted name to see if anything would change. I don't see how it wouldn't be a valid jpg, having just saved it from paint?

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by
                              #17

                              Getting really strange...

                              No special characters in the path ? Not that it should play a role but who knows...

                              If you use QFile to open it, does it work ?

                              Interested in AI ? www.idiap.ch
                              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                              • K Offline
                                K Offline
                                Kelenyche
                                wrote on last edited by
                                #18

                                Nope, the full path is: "/home/pi/Desktop/program/extra/images/scribble.jpg"

                                Alright I'm not familiar with QFile, but I used:

                                QFile testfile("/home/pi/Desktop/program/extra/images/scribble.jpg");
                                
                                if(testfile.exists())
                                {
                                    outputTextBox->append("opened the file");
                                }
                                

                                and it seems to have succeeded.
                                will testfile.exists() do the same test as isNull in QImage?

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                                • SGaistS Offline
                                  SGaistS Offline
                                  SGaist
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #19

                                  No, it just confirms the existence of the file not whether it is valid.

                                  Use the QImageReader class. It's lower level but may give you more information about what is going wrong.

                                  Interested in AI ? www.idiap.ch
                                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                  • K Offline
                                    K Offline
                                    Kelenyche
                                    wrote on last edited by
                                    #20

                                    Ok so I have:

                                    QImage testimage(64,64,QImage::Format_RGB32);
                                    QImageReader reader("/home/pi/Desktop/program/extra/images/scribble.jpg");
                                    
                                    if(reader.read(&testimage))
                                    {
                                        outputTextBox->append("opened the file");
                                    }
                                    

                                    It's telling me the file is good now...

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                                    • SGaistS Offline
                                      SGaistS Offline
                                      SGaist
                                      Lifetime Qt Champion
                                      wrote on last edited by
                                      #21

                                      Within the same application, do you have the same issue if you load a different QImage variable using the usual way ?

                                      Interested in AI ? www.idiap.ch
                                      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                      • K Offline
                                        K Offline
                                        Kelenyche
                                        wrote on last edited by
                                        #22

                                        I think so - I initially tried with the png, then switched to the jpg, and neither one is doing what I expect, so I think they're both coming in null with QImage.

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                                        • K Offline
                                          K Offline
                                          Kelenyche
                                          wrote on last edited by
                                          #23

                                          Ooh, I think I'm onto something. So the way my code was implemented, I read the image, did some resizing and stuff, then was checking if it was null after that, since my textbox wasn't added to the gui yet. I switched to QDebug since that's more handy, and moved that code up - it looks like my resizing stuff was causing the image to become null? I now have a not-resized image that's painting onto the background of the graph!

                                          I'll post my full fix once I figure this out. :)

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