[vtkusers] Dataset Math Transfer?

[Jianhua Ma]

Hi Dear VTK users,
I was wondering is there some way in the vtkStructuredPointsReader
or vtkStructuredPointsFilter:x to do the Math transfer:f(x) say, 
if x >0 then extract Ln(x)? In other words, I want to obtain 
Ln(all StructuredPoints>0), because my original data has too big dynamic
range(0, 4.964107E+9).It has laye values in very few point. 
I would use this method to compress original data for Scalar Visualization.
 Any help would be appreciated.
-Jianhua