QCamera has strange blue tint
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wrote on 29 May 2019, 12:34 last edited by
what mranger said...the color format that Qt expects to see is not what is being sent.
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@SolaVitae said in QCamera has strange blue tint:
QImage(640, 480, QImage::Format_A2RGB30_Premultiplied);
Blue tint could be because the red and blue channels are swapped. If you are in windows this is a common problem. Try using Format_A2BGR30_Premultiplied, when creating the QImage.
wrote on 29 May 2019, 13:18 last edited by SolaVitae@mranger90
it's still blue, its also blue in the viewfinder before the image is even savedside note: The camera works perfectly, and is not blue in the QML Example from QT Creator, but is blue in the regular QT Example
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wrote on 29 May 2019, 15:58 last edited by Kent-Dorfman
Try different values for QCameraImageProcessing::WhiteBalanceMode and see if they have any effect.
In particular look at the definition for the white balance value you are currently using. It says "base value", which would probably infer that there is a list of vender values starting at 1000, where the required value is specific to the product being used.
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Try different values for QCameraImageProcessing::WhiteBalanceMode and see if they have any effect.
In particular look at the definition for the white balance value you are currently using. It says "base value", which would probably infer that there is a list of vender values starting at 1000, where the required value is specific to the product being used.
wrote on 29 May 2019, 16:18 last edited by@Kent-Dorfman
ive tried all of them, with no changeI've narrowed the issue down to it inverting the red/blue colors
as seen in this image
The colors actually are Red - > Green - > Blue, but it inverts red and blue
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wrote on 29 May 2019, 17:23 last edited by
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.
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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.
wrote on 29 May 2019, 17:48 last edited byIs 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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wrote on 29 May 2019, 18:08 last edited by 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. -
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.wrote on 29 May 2019, 18:54 last edited byThe 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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wrote on 29 May 2019, 19:44 last edited by
@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? -
@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?wrote on 29 May 2019, 22:35 last edited by SolaVitae@fcarney
yes, it does not change anythingThe 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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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.
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wrote on 21 Aug 2019, 10:33 last edited by
have you got solution for this problem?
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wrote on 7 Sept 2019, 17:13 last edited by Dan_Dew 9 Jul 2019, 17:14
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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Hi,
From the description you are giving, there might be something like a switch from RGB to BGR.
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wrote on 8 Sept 2019, 16:57 last edited by
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? -
I don't think there's an easy way to do that except by going lower level.
