Since Qt 5.5, brush textures are stored as QImages. If the texture has
been set as a QPixmap, the conversion to QImage may change its pixel
format, depending on the native system format. That is acceptable.
Fixes: QTBUG-69193
Task-number: QTBUG-91418
Change-Id: Ic4dbeaa552b1f2183774a011e38414855a9dc4b1
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>