Info panel background

[Gervase Lam]

I am in the middle of making the digits in the timer and top info panel 
fixed width.  After a lot of struggle, especially with GIMP, and a little 
bit of looking into the ClanLib code, I have managed to do this.

Unfortunately, this means that the info panel needs to be widened 
slightly.  The background to it is not a solid black but has a sort of 
marbled or glass effect.  This used to have "variable" alpha but now does 
not after the images were flattened.

I have gone through the GIMP effects but cannot find any one that would 
produce this effect.  So, what effect was used to produce the info panel 
background?

Thanks,
Gervase.