Dear Qt workers,

I am using custom items to display images, polygons and labels in a QGraphicsView.

Going further on QGraphicsItem features, I want to apply a treatment on the result of the images rendered on the screen. The treatment applies only on image data and not labels, neither polygons.

So I wondering myself what is the best way to manage an off screen buffer, apply treatments, then display it :
1 - manage a group item that will be updated with images displayed, and play with paintEvent. Since paintEvent of children will be called before the group item, I can fill an off screen buffer, then apply the treatments in the paintEvent of the group
2 - overload the [QTCLASS]QGraphicsScene::drawItemsQTCLASS] to first draw raw data of image items, then apply treatments. Polygons and labels can be painted then without interferring.

Maybe there is another features of QGraphicsView I didn't see.
Does anyone had the same needs, and how did you do it?

Thanks by advance.