gdstk (C++ library for manipulation of GDSII and OASIS files. )

Gdstk (GDSII Tool Kit) is a C++ library for creation and
manipulation of GDSII and OASIS files. It is also available as a
Python module meant to be a successor to Gdspy. Key features for the
creation of complex CAD layouts are included: Boolean operations on
polygons (AND, OR, NOT, XOR) based on clipping algorithm, Polygon
offset (inward and outward rescaling of polygons), Efficient
point-in-polygon solutions for large array sets.
Typical applications of Gdstk are in the fields of electronic chip
design, planar lightwave circuit design, and mechanical engineering.