[GRASS5] Histogram matching algorithm?

[Markus Neteler]

Dear developers,

for the mosaicking of some hundred orthophotos we need 
to apply a histogram matching algorithm to minimize the
effects of changing sun position during the flight. 
Does anyone know a solution/algorithm which has been already 
implemented in C (Free Software of course)?

The mosaicking algorithm is almost done but histogram 
matching is a TODO.

Any ideas?

 Markus Neteler