Mapping question...

["Guillaume Dargaud" <dargaud(at)sung3.ifsi.rm.cnr.it>]

For lack of a better place, I'll ask it here even though it is not IDL
specific (but I will probably implement it in IDL).

I need to make maps of the world in a special way (I don't even know what
this is called, so if anybody can provide me with a keyword...)
Say you have a quantity of rain per sq degrees and you want to enlarge the
surface area of places where it rains a lot and shrink the surface area of
dry places... You end up with a tiny sahara, but large tropical zones...
How would you go to do something like that...?
I have seen it done before, but don't know what this kind of mapping is
called.
--
Guillaume Dargaud
Colorado State University - Dept of Atmospheric Science
http://rome.atmos.colostate.edu/
  "My girlfriend told me I should be more affectionate. So I got two
girlfriends."