/// <summary>
/// kruznice zadana dvema body na obvodu a polomerem
/// , pokud je polomer mensi nez polovina vzdalenosti bodu, umisti se stred kruznice do stredoveho bodu tvoriciho obema ridicimi body
/// , stred kruznice se umisti do poloroviny urcene ridicimi body, podle znamenka polomeru
/// </summary>
/// <param name="pt1">prvni bod na obvodu</param>
/// <param name="pt2">druhy bod na ovodu</param>
/// <param name="r">polomer</param>
public Circle2D(Point pt1, Point pt2, double r)
{
double d = Funcs2D.Distance(pt1, pt2) / 2;
if (Math.Abs(r) <= d)
{
Radius = d;
Center = new Point((pt1.X + pt2.X) / 2, (pt1.Y + pt2.Y) / 2);
}
else
{
Radius = Math.Abs(r);
double v = Math.Sqrt(Math.Pow(Radius, 2) - Math.Pow(d, 2));
Center = Funcs2D.LineRelPtOffset(pt1, pt2, 0.5, r < 0 ? -v : v);
}
}