private static void DouglasPeuckerReduction(List <Point> points,
Int32 firstPoint, Int32 lastPoint, Double tolerance, ref List <Int32> pointIndexsToKeep)
{
Double maxDistance = 0;
Int32 indexFarthest = 0;
for (Int32 index = firstPoint; index < lastPoint; index++)
{
Double distance = CustomMath.PerpendicularDistance(points [firstPoint], points [lastPoint], points [index]);
if (distance > maxDistance)
{
maxDistance = distance;
indexFarthest = index;
}
}
if (maxDistance > tolerance && indexFarthest != 0)
{
//Add the largest point that exceeds the tolerance
pointIndexsToKeep.Add(indexFarthest);
CustomMath.DouglasPeuckerReduction(points, firstPoint, indexFarthest, tolerance, ref pointIndexsToKeep);
CustomMath.DouglasPeuckerReduction(points, indexFarthest, lastPoint, tolerance, ref pointIndexsToKeep);
}
}
public static List <Point> DouglasPeuckerReduction(List <Point> points, Double tolerance)
{
if (points == null || points.Count < 3)
{
return(points);
}
Int32 firstPoint = 0;
Int32 lastPoint = points.Count - 1;
List <Int32> pointIndexsToKeep = new List <Int32> ( );
//Add the first and last index to the keepers
pointIndexsToKeep.Add(firstPoint);
pointIndexsToKeep.Add(lastPoint);
//The first and the last point can not be the same
while (points [firstPoint].Equals(points [lastPoint]))
{
lastPoint--;
}
CustomMath.DouglasPeuckerReduction(points, firstPoint, lastPoint, tolerance, ref pointIndexsToKeep);
List <Point> returnPoints = new List <Point> ( );
pointIndexsToKeep.Sort( );
foreach (Int32 index in pointIndexsToKeep)
{
returnPoints.Add(points [index]);
}
return(returnPoints);
}