GD.pm index table limitation

[julien]

Hi there,
i have a problem with the GD module: I need to allocate a lot of
colors (and very sharply defined) for one single image. Apparently,
once the image index color table is full (i.e. approx 255 elements),
all subsequently allocated colors will have the same rgb code as the
last element (the 255th one), which looks obviously not exactly as i
would like.
Anybody knows a solution ?
thanks
cheers
julien