[GRASS-user] using grass on rasters without converting?

[Patton, Eric]

Is there any program available, or a project
in the works, for easy in-and-out conversion? or better yet, a method to use
grass commands on external formats like geotiff without conversion? 

Have a look at r.external:

http://grass.itc.it/grass64/manuals/html64_user/r.external.html

~ Eric.