[Freetype] FreeType newbie

[Marco Mussini]

Hi all,
I'm trying to put an antialiased freetype rendered text into QT graphics 
library. To do this I have an object (called QImage) with 8-bpp depth and 
gray scale color map in which I have copied pixel per pixel the freetype 
rendered bitmap. Also in this QImage object I set white background color to 
be transparent so that it can be overlapped with other objects.
But there is of course a problem now:
if image is displayed into a widget with white background it appear fine. But 
if background is different from white or has many colors (above all dark 
colors), gray scale pixels that regards antialiasing appears badly.
For example if my background is dark blue and text is black, image's pixel 
that regards antialiasing are much more visible and they form a contour for 
any character of the text.
How to handle this problem??

I think that a solution could be to set a partial transparency on all
image's pixel that regard antialiasing, that is all pixels with colors that
are not black or white.
I don't know how to do that.
Does someone knows better techniques to handle this problem??
Thanks,
Marco