/// <summary>
/// Original version of compress
/// The use of shortest path results in some drawbacks...
/// </summary>
/// <param name="trj"></param>
/// <returns></returns>
public VCompressedTrj Compress_v1(Trajectory trj)
{
if (trj.Count == 0)
{
return(null);
}
List <RefPoint> refPoints = getRefPoints(trj);
VCompressedTrj cTrj = new VCompressedTrj();
VCompressedTrj.Item item = new VCompressedTrj.Item();
double dist = 0, appDist = 0;
Edge lastEdge = refPoints[0].e;
item.RefPoint = refPoints[0];
for (int i = 1; i < refPoints.Count; ++i)
{
RefPoint cur = refPoints[i], prev = refPoints[i - 1];
double distance = 0.0, v = 0;
byte roundV = 0, si = (byte)(cur.t - prev.t);
if (cur.e == prev.e)
{
distance = cur.distance - prev.distance;
}
else if (cur.e.Start == prev.e.End)
{
distance = prev.e.Length - prev.distance + cur.distance;
}
else
{
distance = prev.e.Length - prev.distance;
var path = _g.FindPath(prev.e.End, cur.e.Start);
foreach (var e in path)
{
distance += e.Length;
}
distance += cur.distance;
}
v = distance / si;
roundV = (byte)(Math.Round(v) / _binSize);
dist += distance;
appDist += roundV * si * _binSize;
if (Math.Abs(dist - appDist) >= _maxDev)
{
// insert the reference point
cTrj.Items.Add(item);
// clear
item = new VCompressedTrj.Item();
item.RefPoint = cur;
dist = 0;
appDist = 0;
}
else
{
item.Points.Add(new VCompressedMV(si, cur.eid, roundV));
}
}
cTrj.Items.Add(item);
return(cTrj);
}
public Trajectory Decompress(VCompressedTrj ctrj)
{
int size = ctrj.Items.Count;
if (size <= 0)
{
return(null);
}
Trajectory trj = new Trajectory();
// Add the first reference point
for (int i = 0; i < size; ++i)
{
var item = ctrj.Items[i];
double dist = item.RefPoint.distance; // distance from the start point the edge to the current point
long t = item.RefPoint.t;
// add the reference point first
trj.Add(new MotionVector(item.RefPoint.Point, item.RefPoint.t));
Edge lastEdge = item.RefPoint.e;
// Calculate the position of each point
for (int j = 0; j < item.Points.Count; ++j)
{
var cMV = item.Points[j];
double totalDistance = cMV.si * cMV.v * _binSize; // the distance covered during the interval
GeoPoint p = GeoPoint.INVALID;
t += cMV.si;
if (cMV.rid == lastEdge.ID)
{
dist += totalDistance;
p = lastEdge.Predict(lastEdge.Start.Point, dist);
}
else
{
Edge curEdge = _g.Edges[cMV.rid];
dist = totalDistance - (lastEdge.Length - dist); // minus the distance left in the previous road
if (lastEdge.End == curEdge.Start)
{
p = curEdge.Predict(curEdge.Start.Point, dist);
}
else
{
var path = _g.FindPath(lastEdge.End, curEdge.Start);
if (path != null)
{
foreach (var e in path)
{
dist -= e.Length;
}
p = curEdge.Predict(curEdge.Start.Point, dist);
}
else
{
Debug.Assert(false);
}
}
lastEdge = curEdge;
}
trj.Add(new MotionVector(p, t));
}
}
return(trj);
}
