[FOP][PNG][color-mode]

Hi,

I am using fop 0.95 and I get a problem with the color mode.
I would like to have only black color, but it is not working.
This is my fop configuration :

<renderer mime="image/png">
     <color-mode>bi-level</color-mode>
     <transparent-page-background>true</transparent-page-background>
     <anti-aliasing>true</anti-aliasing>
     <rendering>quality</rendering>

     <fonts>
     ...
</renderer>

Do you have any idea why I always get colors in my PNG file ?

Thanks.

Regards,

Yannick