Geoff is a collection of JavaScript functions for working with GeoJSON objects. More generally, it's a library that eases the creation and manipulation of geographic geometries, and makes doing some things in Polymaps shockingly easy.
In this example we use geoff.extent() to draw the visible
bounds of the map on the left onto the map on the right.
In these examples we use geoff.extent() to get
the rectangular bounds of a GeoJSON Polygon feature loaded in this file, then use
geoff.buffer() to add an outer ring to its
geometry, which produces a "knock-out" drawing effect in
SVG.