gimp -i -b '(batch-whiteboard-clean "*.png")' -b '(gimp-quit 0)'

# the batch-whiteboard-clean.scm script should go in: ~/.gimp-2.6/scripts

# from sites:
#   http://matthew.mceachen.us/blog/how-to-clean-up-photos-of-whiteboards-with-gimp-403.html
#   http://registry.gimp.org/node/19822