Make QGraphicsItem interact with an image

I ask you for help because I could not find a way to select the red part of the image attached in a QGraphicsItem so that it can interact with other QGraphicsItems that I create.
The image will look like this:



I wish I could find the intersection of the items I insert with the red part of the image.

QPainterPath intersectedPath = item1->shape()->intersected(item_red->shape());

Thanks for your help.
Greetings

Not sure how are those QGraphicsItems implemented.
Not sure but I think that by default shape() = boundingRect(), so it's a rectangle.
If you want to to create another shapes you should override QGraphicsItem::shape().
As an example have a look at Servo::shape() or Buffer::shape().