What are the graphics editors that can be built upon?

Question

I want to start off with a capable vector graphics drawing/editing program and extend it to create a visual designer for a project I'm working on.

Do you know of a graphics editor that can be built upon? Maybe open source? Users should already be able to freely draw and color graphics, and any form of grouping / arranging elements is a plus.

Answer 1

You could use Inkscape or Karbon14 for vector graphics.

For inkscape, you have access to the API and there is a proposal for a Python extention.

If you don't need colours, you could easely use the Dia Python Plugin.