Problem with fbcon linux support

Good evening!

I’m working with fbcon SDL support, and I’m getting an strange error :
the video output look likes darker.
I tryed with a RivaTNT2 and an ATI Radeon 9250 and I got the same
picture. It’s very strange because at console screen, it’s normal.

If you like, I can provide some pictures.

To finish, I have a simple question: fbcon driver can support 32 bit

Thanks in advice!