/// <summary>
/// Returns the convex hull of the points created from the list
/// <code>points</code>. Note that the first and last point in the
/// returned <code>List<java.awt.Point></code> are the same
/// point.
/// </summary>
/// <param name="points">The list of points. </param>
/// <returns>The convex hull of the points created from the list <code>points</code>. </returns>
public static IList <IntPoint> GetConvexHull(List <IntPoint> points)
{
IntPoint lowestPoint = GetLowestPoint(points);
// Sort points based on angle to lowestPoint
IntPointSorter sorter = new IntPointSorter(lowestPoint);
points.Sort(sorter.ComparePoints);
// Alias for clarity
List <IntPoint> sorted = points;
if (sorted.Count < 3)
{
throw new System.ArgumentException("can only create a convex hull of 3 or more unique points");
}
if (AreAllCollinear(sorted))
{
throw new System.ArgumentException("cannot create a convex hull from collinear points");
}
Stack <IntPoint> stack = new Stack <IntPoint>();
stack.Push(sorted[0]);
stack.Push(sorted[1]);
for (int i = 2; i < sorted.Count; i++)
{
IntPoint head = sorted[i];
IntPoint middle = stack.Pop();
IntPoint tail = stack.Peek();
Turn turn = GetTurn(tail, middle, head);
switch (turn)
{
case Turn.CounterClockwise:
stack.Push(middle);
stack.Push(head);
break;
case Turn.Clockwise:
i--;
break;
case Turn.Collinear:
stack.Push(head);
break;
}
}
// close the hull
stack.Push(sorted[0]);
return(new List <IntPoint>(stack));
}
/// <summary>
/// Returns the convex hull of the points created from the list
/// <code>points</code>. Note that the first and last point in the
/// returned <code>List<java.awt.Point></code> are the same
/// point.
/// </summary>
/// <param name="points">The list of points. </param>
/// <returns>The convex hull of the points created from the list <code>points</code>. </returns>
public static IList<IntPoint> GetConvexHull(List<IntPoint> points)
{
IntPoint lowestPoint = GetLowestPoint(points);
// Sort points based on angle to lowestPoint
IntPointSorter sorter = new IntPointSorter(lowestPoint);
points.Sort(sorter.ComparePoints);
// Alias for clarity
List<IntPoint> sorted = points;
if (sorted.Count < 3)
{
throw new System.ArgumentException("can only create a convex hull of 3 or more unique points");
}
if (AreAllCollinear(sorted))
{
throw new System.ArgumentException("cannot create a convex hull from collinear points");
}
Stack<IntPoint> stack = new Stack<IntPoint>();
stack.Push(sorted[0]);
stack.Push(sorted[1]);
for (int i = 2; i < sorted.Count; i++)
{
IntPoint head = sorted[i];
IntPoint middle = stack.Pop();
IntPoint tail = stack.Peek();
Turn turn = GetTurn(tail, middle, head);
switch (turn)
{
case Turn.CounterClockwise:
stack.Push(middle);
stack.Push(head);
break;
case Turn.Clockwise:
i--;
break;
case Turn.Collinear:
stack.Push(head);
break;
}
}
// close the hull
stack.Push(sorted[0]);
return new List<IntPoint>(stack);
}
