Polygon Offsetting

You can offset a list of Polygons polys by an amount amount like this:

>>> result = Polygon.offset(polys, amount)

Again, the return variable will be a list of Polygons since offsetting may create additional polygons.

Positive values for amount result in a growing of the polygons, negative values result in shrinking by that amount.

You may specify an optional tip_decorator argument which takes a reference to a tip decorator function of the type f(a,b, c,d, is_cw). The tip decorator function will return a list of additional vertices to insert between the line segments (a,b) and (c,d) to make them look nicer. The is_cw variable specifies the orientation of the line segments. As an example for a tip decorator function, have a look at the default “pointy” tip decorator from the Py2D source:

def tip_decorator_pointy(a,b, c,d, is_cw):
	intersection = intersect_line_line(a,b,c,d)
	return [intersection]