Q: GDI text and the associated alpha

I want to create an image containing some text.
I want to construct the image data for the text
with the TextOut function. I need the alpha
(blending) channel also because the image is
later composed with other images. My problem is
that it seems like Windows uses different alpha
values depending on the background color on which
the text is drawn. Does anybody know if this is
the case or if there is another way of getting
the text and alpha.

Thanks in advance
Ole Petersen