Polygon created by subtracted polygons

Question

Above is a polygon (gray area) where I subtracted 4 polygons (red, green, purple, and blue areas). Is there a way to get the vertices of the created sub-polygon (small gray polygon)?

The polygons can be of any shape. Also, the side subtracted polygon can lie on the side of the main polygon (that's why I did not call it hole).

Answer 1

You want to look into clipping algorithms like Vatti. Or may be you want some port or binding of gpc.