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using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
namespace QuickRoute.BusinessEntities
{
[Serializable]
public class SessionCollection : ICollection<Session>
{
private List<Session> sessions = new List<Session>();
public Session this[int index]
{
get { return sessions[index]; }
set
{
sessions[index] = value;
}
}
/// <summary>
/// Using linear least squares algorithm described at http://en.wikipedia.org/wiki/Linear_least_squares
/// </summary>
/// <returns></returns>
public Transformation CalculateAverageTransformation()
{
var averageProjectionOrigin = new LongLat();
foreach (var session in this)
{
averageProjectionOrigin += session.ProjectionOrigin / Count;
}
if (Count == 0) return null;
var n = 4;
var XtX = new GeneralMatrix(n, n);
var Xty = new GeneralMatrix(n, 1);
var numberOfUnknowns = 0;
foreach (var session in this)
{
var m = session.Handles.Length;
if (m < 2) continue;
numberOfUnknowns += m;
var startDistance = session.Route.GetAttributeFromParameterizedLocation(WaypointAttribute.Distance, session.Route.FirstPL).Value;
for (var i = 0; i < m; i++)
{
var longLat = session.Route.GetLocationFromParameterizedLocation(session.Handles[i].ParameterizedLocation);
var p = longLat.Project(averageProjectionOrigin); // projected point on earth (metres)
var q = session.Handles[i].Location; // point on map image (pixels)
var endDistance = (i != m - 1)
? (session.Route.GetAttributeFromParameterizedLocation(WaypointAttribute.Distance, session.Handles[i].ParameterizedLocation).Value +
session.Route.GetAttributeFromParameterizedLocation(WaypointAttribute.Distance, session.Handles[i + 1].ParameterizedLocation).Value ) / 2
: session.Route.GetAttributeFromParameterizedLocation(WaypointAttribute.Distance, session.Route.LastPL).Value;
var w = endDistance - startDistance; // weight
startDistance = endDistance;
XtX.SetElement(0, 0, XtX.GetElement(0, 0) + w * (p.X * p.X + p.Y * p.Y));
XtX.SetElement(0, 2, XtX.GetElement(0, 2) + w * p.X);
XtX.SetElement(0, 3, XtX.GetElement(0, 3) - w * p.Y);
XtX.SetElement(1, 1, XtX.GetElement(1, 1) + w * (p.X * p.X + p.Y * p.Y));
XtX.SetElement(1, 2, XtX.GetElement(1, 2) + w * p.Y);
XtX.SetElement(1, 3, XtX.GetElement(1, 3) + w * p.X);
XtX.SetElement(2, 0, XtX.GetElement(2, 0) + w * p.X);
XtX.SetElement(2, 1, XtX.GetElement(2, 1) + w * p.Y);
XtX.SetElement(2, 2, XtX.GetElement(2, 2) + w);
XtX.SetElement(3, 0, XtX.GetElement(3, 0) - w * p.Y);
XtX.SetElement(3, 1, XtX.GetElement(3, 1) + w * p.X);
XtX.SetElement(3, 3, XtX.GetElement(3, 3) + w);
Xty.SetElement(0, 0, Xty.GetElement(0, 0) + w * (q.X * p.X - q.Y * p.Y));
Xty.SetElement(1, 0, Xty.GetElement(1, 0) + w * (q.X * p.Y + q.Y * p.X));
Xty.SetElement(2, 0, Xty.GetElement(2, 0) + w * q.X);
Xty.SetElement(3, 0, Xty.GetElement(3, 0) + w * q.Y);
}
}
var T = new GeneralMatrix(3, 3);
if (numberOfUnknowns == 0)
{
T = this[0].InitialTransformationMatrix;
}
else if (numberOfUnknowns == 1)
{
T = this[0].Handles[0].TransformationMatrix;
}
else
{
var B = XtX.QRD().Solve(Xty);
T.SetElement(0, 0, B.GetElement(0, 0));
T.SetElement(0, 1, B.GetElement(1, 0));
T.SetElement(0, 2, B.GetElement(2, 0));
T.SetElement(1, 0, B.GetElement(1, 0));
T.SetElement(1, 1, -B.GetElement(0, 0));
T.SetElement(1, 2, B.GetElement(3, 0));
T.SetElement(2, 0, 0);
T.SetElement(2, 1, 0);
T.SetElement(2, 2, 1);
}
return new Transformation(T, averageProjectionOrigin);
}
/// <summary>
/// Creates a shallow copy.
/// </summary>
/// <returns></returns>
public SessionCollection Copy()
{
var copy = new SessionCollection();
foreach (var s in sessions)
{
copy.Add(s);
}
return copy;
}
#region ICollection<Session> Members
public void Add(Session item)
{
sessions.Add(item);
}
public void Clear()
{
sessions.Clear();
}
public bool Contains(Session item)
{
return sessions.Contains(item);
}
public void CopyTo(Session[] array, int arrayIndex)
{
sessions.CopyTo(array, arrayIndex);
}
public int Count
{
get { return sessions.Count; }
}
public bool IsReadOnly
{
get { return false; }
}
public bool Remove(Session item)
{
return sessions.Remove(item);
}
#endregion
#region IEnumerable<Session> Members
public IEnumerator<Session> GetEnumerator()
{
return sessions.GetEnumerator();
}
#endregion
#region IEnumerable Members
IEnumerator IEnumerable.GetEnumerator()
{
return sessions.GetEnumerator();
}
#endregion
}
}
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