Polygon2d Polygon2d::scaleaboutcentroid(float scale) {
Polygon2d n;
V2d cen=centroid();
for (int i=1;i<=vs.len;i++) {
V2d x=vs.num(i);
x=x-cen;
x=x*scale;
x=x+cen;
n.add(x);
}
return n;
}
Polygon2d Polygon2d::operator*(float f) {
Polygon2d p;
for (int i=1;i<=vs.len;i++)
p.add(vs.num(i)*f);
return p;
}