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Can't send image to QLabel in Windows environment (it works without problems in Linux)

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  • H Helge1980

    Hi!
    I can't output the image to QLabel in a Windows environment.
    I tried it in two ways. The image size is 144 x 88 pixels (~ 3 KB).

    1. using QImage:
    const QString tmb_file = "C:\\Users\\User\\thumbnail.jpg";
    const QImage img = QImage(tmb_file, "JPG");
    const QPixmap pixmap = QPixmap::fromImage(img);
    ui->labelThumb->setPixmap(pixmap);
    
    1. directly via QPixmap:
    const QString tmb_file = "C:\\Users\\User\\thumbnail.jpg";
    const QPixmap pixmap = QPixmap(tmb_file);
    ui->labelThumb->setPixmap(pixmap);
    
    Pl45m4P Offline
    Pl45m4P Offline
    Pl45m4
    wrote on last edited by
    #2

    @Helge1980 said in Can't send image to QLabel in Windows environment (it works without problems in Linux):

    I can't

    "I cant" is not a proper description of an issue :)

    Try / instead of \\.


    If debugging is the process of removing software bugs, then programming must be the process of putting them in.

    ~E. W. Dijkstra

    H 1 Reply Last reply
    0
    • Pl45m4P Pl45m4

      @Helge1980 said in Can't send image to QLabel in Windows environment (it works without problems in Linux):

      I can't

      "I cant" is not a proper description of an issue :)

      Try / instead of \\.

      H Offline
      H Offline
      Helge1980
      wrote on last edited by Helge1980
      #3

      @Pl45m4

      Replacing \ \ with / didn't help

      1 Reply Last reply
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      • Christian EhrlicherC Offline
        Christian EhrlicherC Offline
        Christian Ehrlicher
        Lifetime Qt Champion
        wrote on last edited by
        #4

        Then check if the file really exists and is readable.

        Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
        Visit the Qt Academy at https://academy.qt.io/catalog

        H 1 Reply Last reply
        3
        • H Helge1980

          Hi!
          I can't output the image to QLabel in a Windows environment.
          I tried it in two ways. The image size is 144 x 88 pixels (~ 3 KB).

          1. using QImage:
          const QString tmb_file = "C:\\Users\\User\\thumbnail.jpg";
          const QImage img = QImage(tmb_file, "JPG");
          const QPixmap pixmap = QPixmap::fromImage(img);
          ui->labelThumb->setPixmap(pixmap);
          
          1. directly via QPixmap:
          const QString tmb_file = "C:\\Users\\User\\thumbnail.jpg";
          const QPixmap pixmap = QPixmap(tmb_file);
          ui->labelThumb->setPixmap(pixmap);
          
          JonBJ Offline
          JonBJ Offline
          JonB
          wrote on last edited by JonB
          #5

          @Helge1980
          As @Christian-Ehrlicher has said. Also, QPixmap(tmb_file) and QPixmap::fromImage(img) will return a pixmap where QPixmap::isNull() == true, and similarly for QImage(tmb_file, "JPG"). You should check for this, both for debugging/because you have a problem and anyway at runtime since you're reading from a file.

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          • Christian EhrlicherC Christian Ehrlicher

            Then check if the file really exists and is readable.

            H Offline
            H Offline
            Helge1980
            wrote on last edited by
            #6

            @Christian-Ehrlicher

            Yes, the file exists and is readable

            Pl45m4P 1 Reply Last reply
            0
            • Christian EhrlicherC Offline
              Christian EhrlicherC Offline
              Christian Ehrlicher
              Lifetime Qt Champion
              wrote on last edited by
              #7

              Did you relocate Qt or similar? Please check if you jpg image plugin is available and check if jpg can be loaded with e.g. QImageReader::supportedFormats()

              Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
              Visit the Qt Academy at https://academy.qt.io/catalog

              H 1 Reply Last reply
              0
              • Christian EhrlicherC Christian Ehrlicher

                Did you relocate Qt or similar? Please check if you jpg image plugin is available and check if jpg can be loaded with e.g. QImageReader::supportedFormats()

                H Offline
                H Offline
                Helge1980
                wrote on last edited by
                #8

                @Christian-Ehrlicher

                No, I didn't move the Qt libraries, everything was installed automatically.

                Indeed, for some reason there is no support for the JPG format:

                qDebug() << QImageReader::supportedImageFormats();
                

                ("bmp", "pbm", "pgm", "png", "ppm", "xbm", "xpm")

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                • Christian EhrlicherC Offline
                  Christian EhrlicherC Offline
                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on last edited by
                  #9

                  The jpeg plugin must be in <QTDIR>/plugins/imageformats

                  Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                  Visit the Qt Academy at https://academy.qt.io/catalog

                  1 Reply Last reply
                  3
                  • H Helge1980

                    @Christian-Ehrlicher

                    Yes, the file exists and is readable

                    Pl45m4P Offline
                    Pl45m4P Offline
                    Pl45m4
                    wrote on last edited by Pl45m4
                    #10

                    Stupid question:
                    Is the labelThumb QLabel visible and enabled in your GUI?

                    @Helge1980 said in Can't send image to QLabel in Windows environment (it works without problems in Linux):

                    ("bmp", "pbm", "pgm", "png", "ppm", "xbm", "xpm")

                    Edit: Ah ok, so no JPG plugin


                    If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                    ~E. W. Dijkstra

                    H 1 Reply Last reply
                    0
                    • Pl45m4P Pl45m4

                      Stupid question:
                      Is the labelThumb QLabel visible and enabled in your GUI?

                      @Helge1980 said in Can't send image to QLabel in Windows environment (it works without problems in Linux):

                      ("bmp", "pbm", "pgm", "png", "ppm", "xbm", "xpm")

                      Edit: Ah ok, so no JPG plugin

                      H Offline
                      H Offline
                      Helge1980
                      wrote on last edited by
                      #11
                      This post is deleted!
                      1 Reply Last reply
                      0
                      • H Offline
                        H Offline
                        Helge1980
                        wrote on last edited by
                        #12

                        I solved the problem by replacing the jpg format with png

                        1 Reply Last reply
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