/// <summary>
/// Finds the ConvexHull of a series of points. See
/// http://www.cs.princeton.edu/courses/archive/spr10/cos226/demo/ah/GrahamScan.html
/// for further information.
/// </summary>
/// <param name="points">The points to compute the ConvexHull for</param>
/// <returns>a collection of points that represents the polygon
/// of the ConvexHull</returns>
public static ICollection<Point> CalculateConvexHull(ICollection<Point> points)
{
if (points.Count <= 3)
return points;
List<ConvexHullPoint> chPoints = new List<ConvexHullPoint>();
// Get the current anchor point
anchor = new ConvexHullPoint(DetermineAnchorPoint(points), 0, null);
// Loop over the points
foreach (Point currentPoint in points)
{
// Ensure that this point is not the anchor
if (currentPoint != anchor.Point)
{
// Create a new ConvexHUllPoint and save it for later use
ConvexHullPoint newConvexHullPoint = new ConvexHullPoint(currentPoint, CalculateCartesianAngle(currentPoint.X - anchor.Point.X, currentPoint.Y - anchor.Point.Y), anchor);
chPoints.Add(newConvexHullPoint);
}
}
// Sort the points
chPoints.Sort();
// Actually calculate and return the ConvexHull
return GrahamScan(chPoints);
}
/// <summary>
/// Determines the orientation of the provided points
/// </summary>
/// <param name="chPoint1">The first ConvexHullPoint</param>
/// <param name="chPoint2">The second ConvexHullPoint</param>
/// <param name="chPoint3">The third ConvexHullPoint</param>
/// <returns>a value indicating how the provided points are oriented</returns>
private static int Orientation(ConvexHullPoint chPoint1, ConvexHullPoint chPoint2, ConvexHullPoint chPoint3)
{
return Orientation(chPoint1.Point.X, chPoint1.Point.Y, chPoint2.Point.X, chPoint2.Point.Y, chPoint3.Point.X, chPoint3.Point.Y);
}
