put an Image (black/white) over a panel backgroundimage

Question

Hello,

I want to put a scanned picture (I get it as a byte[] from an external module) into a panel. The panel has a backgroundImage which works like an empty form. The scanned image should fill the "fields" of the form.
The scanned image is a simple black/white picture.

Now I want to change the color white into transparent and mix the two pictures. Is this possible?
Or is there an other way to "mix" two pictures?

Thomas