QGraphicsItem click on alpha transparent area

[sw0ce]

Hi,

I´ve subclassed the QGraphicsItem and implemented the mousePressEvent. I load an image (.png) to the pixmap with transparent areas in it (opacity = 0). Everything is fine with the click event until I click into the transparent area. I want to get the click event also on These areas.
My solution at the moment is to set the opacity to 0.01 and this works fine. But with a bright background this part is visible (just a little bit but it annoys me :) ).

Does someone know a better solution without making the transparent sections visible?

Thanks an regards.