public AreaStatistics(Geometry <Point> geometry)
{
this.NumberOfPoints = geometry.TotalNumberOfPoints;
this.Areas = SpatialUtility.GetPrimitiveAreas(geometry);
}
// ref: https://www.tandfonline.com/doi/abs/10.1179/000870493786962263
public static List <T> SimplifyByVisvalingam <T>(List <T> pointList, SimplificationParamters parameters, bool isRing /*, double threshold, bool isRing, bool retain3Points = false*/) where T : IPoint
{
if (pointList == null || pointList.Count <= 3)
{
return(pointList);
}
var areas = SpatialUtility.GetPrimitiveAreas(pointList, isRing);
List <T> pList = pointList.ToList();
//var areas2 = SpatialUtility.GetPrimitiveAreas(pointList, isRing);
//List<T> pList2 = pointList.ToList();
while (areas.Count > 0)
{
//if (!areas.SequenceEqual(areas2))
//{
//}
//if (!pList.SequenceEqual(pList2))
//{
//}
var minArea = Statistics.Statistics.GetMin(areas);
if (minArea > parameters.AreaThreshold)
{
break;
}
var pointCount = pList.Count;
var areaCount = areas.Count;
//double a1=0, a2=0;
//remove min areas
for (int i = areas.Count - 1; i >= 0; i--)
{
if (areas[i] == minArea)
{
if (isRing || i > 0)
{
// (i-1, i, i+2): i+2 is used insted of i+1 because i+1 is going to be removed
var firstIndex = i - 1 < 0 ? pointCount - 1 : i - 1;
areas[firstIndex] = SpatialUtility.GetUnsignedTriangleArea(pList[firstIndex], pList[i], pList[(i + 2) % pointCount]);
//a1 = areas[firstIndex];
}
if (isRing || i < areas.Count - 1)
{
// (i, i+2, i+3): i is used insted of i+1 because i+1 is going to be removed
areas[(i + 1) % areaCount] = SpatialUtility.GetUnsignedTriangleArea(pList[i], pList[(i + 2) % pointCount], pList[(i + 3) % pointCount]);
//a2 = areas[(i + 1) % areaCount];
}
////recalculate adjacent areas
//if (i > 0)
//{
// areas[i - 1] = SpatialUtility.GetUnsignedTriangleArea(pList[i - 1], pList[i], pList[i + 2]);
//}
//if (i < areas.Count - 1)
//{
// areas[i] = SpatialUtility.GetUnsignedTriangleArea(pList[i], pList[i + 1], pList[i + 2]);
//}
pList.RemoveAt((i + 1) % pointCount);
areas.RemoveAt(i);
break;
}
}
//for (int i = areas2.Count - 1; i >= 0; i--)
//{
// if (areas2[i] == minArea)
// {
// pList2.RemoveAt((i + 1));
// areas2.RemoveAt(i);
// ////recalculate adjacent areas
// if (i > 0)
// {
// areas2[i - 1] = SpatialUtility.GetUnsignedTriangleArea(pList2[i - 1], pList2[i], pList2[i + 1]);
// if (areas2[i - 1] != a1)
// {
// }
// }
// if (i < areas2.Count - 1)
// {
// areas2[i] = SpatialUtility.GetUnsignedTriangleArea(pList2[i], pList2[i + 1], pList2[i + 2]);
// if (areas2[i] != a2)
// {
// }
// }
// break;
// }
//}
}
if (parameters.Retain3Points && pList.Count == 2)
{
pList.Insert(1, pointList[pointList.Count() / 2]);
}
return(pList.ToList());
}
public AreaStatistics(List <Geometry <Point> > geometries)
{
this.NumberOfPoints = geometries.Sum(g => g.TotalNumberOfPoints);
this.Areas = SpatialUtility.GetPrimitiveAreas(geometries);
}