Closed figure expansion/contraction algorithm

Ted Hill thill at
Tue Nov 26 09:18:12 PST 2002


I am working on a medical imaging application and I need to be able to
'expand' and 'contract' closed shapes. These are defined in two dimensions
as an ordered set of x,y points.

I am wondering if anyone knows of an algorithm in the public domain that can
used for this?

For example, in my application a physician may trace a line around a tumor
using the mouse
(thus defining the set of x,y points). Then the physician may want to expand
shape by adding a 1 cm margin around it. Alternatively, the physician may
want to 'shrink' the contour.

Thank you for any suggestions,

Ted Hill
Software Engineer

The compgeom mailing lists: see
or send mail to compgeom-request at with the line:
send readme
Now archived at

More information about the Compgeom-announce mailing list