Hi,
My problem is this: I want to make "holes" into an imported bitmap image, so that I can see through to what is below that image.
I can't figure a way to achieve this with currently available possibilities.
I would suggest a blending mode "source" on individual objects.
(Comparable to composition-mode "Source" from QPainter: http://doc.qt.nokia.com/4.6/qpainter.html#CompositionMode-enum)
Currently creating an object with an alpha value allows transparency to the object below. But it does not make a hole into that object because the "normal" blending imitates a real transparent object.
The mode "source" on an object would take the complete RGBA from a pixel and apply it only in the same layer. So if that object is on top in that layer, the alpha value would define how that layer is transparent at that position, regardless, what objects are below. This would be like erasing the objects below in that layer.
Best regards, (you're doing a great job!)
Joachim
Have you tried using a clippath or mask to achieve what you're looking for?