[Development] What is the correct way to use QTransform to rotate a QImage by the Y axis?

JiDe Zhang zccrs at live.com
Wed Jul 20 11:06:43 CEST 2022

The software backend and opengl backend have same as bug, so I think the bug is not related to scene graphics backend. I conjecture this bug is related to QQuickRotation::applyTo, It's use the QMatrix4x4::projectedRotate, In elsewhere, this QMatrix4x4 will be converted to a QTransform, so I started testing QTransform, and found those problems using it with QImage for rotate.
From: Allan Sandfeld Jensen <kde at carewolf.com>
Sent: Wednesday, July 20, 2022 16:47
To: development at qt-project.org <development at qt-project.org>; JiDe Zhang <zccrs at live.com>
Subject: Re: [Development] What is the correct way to use QTransform to rotate a QImage by the Y axis?

On Mittwoch, 20. Juli 2022 10:43:36 CEST JiDe Zhang wrote:
> I trying fix https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugreports.qt.io%2Fbrowse%2FQTBUG-75954&data=05%7C01%7C%7C23d7f64cd4714c88d47508da6a2c8103%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637939036634730765%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=EMVm0A3nA5c8qDEy8myCQrOq6DwTWW5VE0r6StkUflc%3D&reserved=0, I think the
> problem is related to it.

Interesting. Might be worth checking out if it acts differently between
different scenegraph backends. RHI OpenGL vs Software for instance. Not sure
we would be doing the transform on qimages unless in software mode.

Best regards

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