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QCamera has strange blue tint

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  • mranger90M mranger90

    Ok, that's pretty much what I expected. The output from the camera is probably RGB but a lot of windows drivers are expecting BGR. Or it's possible (but less likely) that your camera is putting out BGR and the driver expects RGB. You might be able to change this by examining the QImageEncoderSettings to see if there is a pixel format and changing it. Or you can try intercepting the buffers and building a QImage based on the correct orientation.

    SolaVitaeS Offline
    SolaVitaeS Offline
    SolaVitae
    wrote on last edited by
    #15

    @mranger90

    Is there an easy way to do this? seems odd that it only occurs in QT, with both my actual webcam and a virtual one, but doesn't occur in an example using QML

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    • mranger90M Offline
      mranger90M Offline
      mranger90
      wrote on last edited by mranger90
      #16

      You can check to see what the camera is supporting with

          QList<QVideoFrame::PixelFormat> formats = m_camera->supportedViewfinderPixelFormats();
          qDebug() << "supported formats " << formats;
      

      Then you might be able to do something like:

      viewFinderSettings.setPixelFormat(QVideoFrame::Format_RGB24);
      

      You might also want to check with some other application. As I recall, on windows the QCamera stuff is a rather thin layer over DirectShow so you might want to play with that to get a clear idea of whats coming off the camera.
      If worse comes to worst you may want to use something like OpenCV which will give you more control over the capture buffers and how to format them.

      SolaVitaeS 1 Reply Last reply
      1
      • mranger90M mranger90

        You can check to see what the camera is supporting with

            QList<QVideoFrame::PixelFormat> formats = m_camera->supportedViewfinderPixelFormats();
            qDebug() << "supported formats " << formats;
        

        Then you might be able to do something like:

        viewFinderSettings.setPixelFormat(QVideoFrame::Format_RGB24);
        

        You might also want to check with some other application. As I recall, on windows the QCamera stuff is a rather thin layer over DirectShow so you might want to play with that to get a clear idea of whats coming off the camera.
        If worse comes to worst you may want to use something like OpenCV which will give you more control over the capture buffers and how to format them.

        SolaVitaeS Offline
        SolaVitaeS Offline
        SolaVitae
        wrote on last edited by
        #17

        @mranger90

        The list returns (Format_RGB24, Format_YUV420P), its default set to the RGB24, and changing it to YUV420p does nothing.

        As for testing it elsewhere, it works flawlessly everywhere else. The default camera app on windows works, a webcam testing website works, skype works.

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        • fcarneyF Offline
          fcarneyF Offline
          fcarney
          wrote on last edited by
          #18

          @SolaVitae,
          Just a shot in the dark. Have you tried explicitly setting the pixel format to QVideoFrame::Format_RGB24? Just in case some other app changed its mode?

          C++ is a perfectly valid school of magic.

          SolaVitaeS 1 Reply Last reply
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          • fcarneyF fcarney

            @SolaVitae,
            Just a shot in the dark. Have you tried explicitly setting the pixel format to QVideoFrame::Format_RGB24? Just in case some other app changed its mode?

            SolaVitaeS Offline
            SolaVitaeS Offline
            SolaVitae
            wrote on last edited by SolaVitae
            #19

            @fcarney
            yes, it does not change anything

            The issue does not occur on my laptop, or a friend's PC. So im guessing it has something to do with my pc. What it is I can't figure out, but I guess it's not that big of a deal if it's only on my PC. It will subconciously bother me to no ender, but oh well

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #20

              Hi,

              Since you are talking about a virtual camera, it might be generating BGR images. And since it's virtual you might be able to configure that.

              In any case, you can use QImage::rgbSwapped to convert to the right order.

              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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              • V Offline
                V Offline
                VietTran
                wrote on last edited by
                #21

                have you got solution for this problem?

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                • D Offline
                  D Offline
                  Dan_Dew
                  wrote on last edited by Dan_Dew
                  #22

                  Same here. Maybe after Windows-Update (Win10).
                  Viewfinder and Image of QCamera in blue.
                  People look like smurfs.
                  Different webcams, same result.
                  QML-Camera is OK. Any other Cam-Apps in Windows (Skype,..) are OK.
                  I hope of a solution, most of my apps base on that.

                  Someone with more information? Thank You.

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                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #23

                    Hi,

                    From the description you are giving, there might be something like a switch from RGB to BGR.

                    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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                    • D Offline
                      D Offline
                      Dan_Dew
                      wrote on last edited by
                      #24

                      SGaist, thank you and yes, its a BGR/RGB problem. It seems to occur rare at this time.
                      When customers complains, I would improvise with a manual switch for swapping colors at the QImages.
                      Do you have an idea for doing that at the viewfinder?

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                      • SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #25

                        I don't think there's an easy way to do that except by going lower level.

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

                        1 Reply Last reply
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