public int CompareTo(object obj)
{
PointToProcess another = (PointToProcess)obj;
return((K < another.K) ? -1 : (K > another.K) ? 1 :
((Distance > another.Distance) ? -1 : (Distance < another.Distance) ? 1 : 0));
}
public int CompareTo(object obj)
{
PointToProcess pointToProcess = (PointToProcess)obj;
if (!(K < pointToProcess.K))
{
if (!(K > pointToProcess.K))
{
if (!(Distance > pointToProcess.Distance))
{
if (!(Distance < pointToProcess.Distance))
{
return(0);
}
return(1);
}
return(-1);
}
return(1);
}
return(-1);
}
/// <summary>
/// Find convex hull for the given set of points.
/// </summary>
///
/// <param name="points">Set of points to search convex hull for.</param>
///
/// <returns>Returns set of points, which form a convex hull for the given <paramref name="points"/>.
/// The first point in the list is the point with lowest X coordinate (and with lowest Y if there are
/// several points with the same X value). Points are provided in counter clockwise order
/// (<a href="http://en.wikipedia.org/wiki/Cartesian_coordinate_system">Cartesian
/// coordinate system</a>).</returns>
///
public IEnumerable <Point> FindHull(IEnumerable <Point> points)
{
var pointsToProcess = new List <PointToProcess>();
int firstCornerIndex = 0;
PointToProcess firstCorner = null;
int fi = 0;
var firstPoint = new Point();
bool newPoly = true;
int polygonCount = 0;
foreach (var point in points)
{
// convert input points to points
var pp = new PointToProcess(point);
pointsToProcess.Add(pp);
if (newPoly)
{
firstPoint = point;
newPoly = false;
}
else
{
if (point == firstPoint)
{
polygonCount++;
newPoly = true;
}
}
// find a point, with lowest X and lowest Y
if ((firstCorner == null) ||
(pp.X < firstCorner.X) ||
((pp.X == firstCorner.X) && (pp.Y < firstCorner.Y)))
{
firstCorner = pp;
firstCornerIndex = fi;
}
fi++;
}
if (pointsToProcess.Count == 0)
{
return(points);
}
// thats not true! a convexhull can be different from the polyon!
//if (polygonCount <= 0)
// return points;
// remove the just found point
pointsToProcess.RemoveAt(firstCornerIndex);
// find K (tangent of line's angle) and distance to the first corner
foreach (var point in pointsToProcess)
{
var dx = point.X - firstCorner.X;
var dy = point.Y - firstCorner.Y;
// don't need square root, since it is not important in our case
point.Distance = dx * dx + dy * dy;
// tangent of lines angle
point.K = (dx == 0) ? double.PositiveInfinity : (double)dy / dx;
}
// sort point by angle and distance
pointsToProcess.Sort();
var convexHullTemp = new List <PointToProcess>();
// add first corner, which is always on the hull
convexHullTemp.Add(firstCorner);
// add another point, which forms a line with lowest slope
convexHullTemp.Add(pointsToProcess[0]);
pointsToProcess.RemoveAt(0); //Lytico: error here: was: points.removeat(0);
var lastPoint = convexHullTemp[1];
var prevPoint = convexHullTemp[0];
while (pointsToProcess.Count != 0)
{
PointToProcess newPoint = pointsToProcess[0];
// skip any point, which has the same slope as the last one
if (newPoint.K == lastPoint.K)
{
pointsToProcess.RemoveAt(0);
continue;
}
// check if current point is on the left side from two last points
if ((newPoint.X - prevPoint.X) * (lastPoint.Y - newPoint.Y) - (lastPoint.X - newPoint.X) * (newPoint.Y - prevPoint.Y) < 0)
{
// add the point to the hull
convexHullTemp.Add(newPoint);
// and remove it from the list of points to process
pointsToProcess.RemoveAt(0);
prevPoint = lastPoint;
lastPoint = newPoint;
}
else
{
// remove the last point from the hull
convexHullTemp.RemoveAt(convexHullTemp.Count - 1);
lastPoint = prevPoint;
prevPoint = convexHullTemp[convexHullTemp.Count - 2];
}
}
// convert points back
var convexHull = new List <Point>(convexHullTemp.Count);
foreach (PointToProcess pt in convexHullTemp)
{
convexHull.Add(new Point(pt.X, pt.Y));
}
return(convexHull);
//convexHullTemp.Select<PointToProcess,PointD>(pt=>pt.ToPoint());
}
public static List <Point> FindHull(List <Point> points)
{
List <PointToProcess> pointsToProcess = new List <PointToProcess>();
// convert input points to points we can process
foreach (Point point in points)
{
pointsToProcess.Add(new PointToProcess(point));
}
// find a point, with lowest X and lowest Y
int firstCornerIndex = 0;
PointToProcess firstCorner = pointsToProcess[0];
for (int i = 1, n = pointsToProcess.Count; i < n; i++)
{
if ((pointsToProcess[i].X < firstCorner.X) ||
((pointsToProcess[i].X == firstCorner.X) && (pointsToProcess[i].Y < firstCorner.Y)))
{
firstCorner = pointsToProcess[i];
firstCornerIndex = i;
}
}
// remove the just found point
pointsToProcess.RemoveAt(firstCornerIndex);
// find K (tangent of line's angle) and distance to the first corner
for (int i = 0, n = pointsToProcess.Count; i < n; i++)
{
double dx = pointsToProcess[i].X - firstCorner.X;
double dy = pointsToProcess[i].Y - firstCorner.Y;
// don't need square root, since it is not important in our case
pointsToProcess[i].Distance = dx * dx + dy * dy;
// tangent of lines angle
pointsToProcess[i].K = (dx == 0) ? float.PositiveInfinity : (float)dy / dx;
}
// sort points by angle and distance
pointsToProcess.Sort();
List <PointToProcess> convexHullTemp = new List <PointToProcess>();
// add first corner, which is always on the hull
convexHullTemp.Add(firstCorner);
// add another point, which forms a line with lowest slope
convexHullTemp.Add(pointsToProcess[0]);
points.RemoveAt(0);
PointToProcess lastPoint = convexHullTemp[1];
PointToProcess prevPoint = convexHullTemp[0];
while (pointsToProcess.Count != 0)
{
PointToProcess newPoint = pointsToProcess[0];
// skip any point, which has the same slope as the last one or
// has 0 distance to the first point
if ((newPoint.K == lastPoint.K) || (newPoint.Distance == 0))
{
pointsToProcess.RemoveAt(0);
continue;
}
// check if current point is on the left side from two last points
if ((newPoint.X - prevPoint.X) * (lastPoint.Y - newPoint.Y) - (lastPoint.X - newPoint.X) * (newPoint.Y - prevPoint.Y) < 0)
{
// add the point to the hull
convexHullTemp.Add(newPoint);
// and remove it from the list of points to process
pointsToProcess.RemoveAt(0);
prevPoint = lastPoint;
lastPoint = newPoint;
}
else
{
// remove the last point from the hull
convexHullTemp.RemoveAt(convexHullTemp.Count - 1);
lastPoint = prevPoint;
prevPoint = convexHullTemp[convexHullTemp.Count - 2];
}
}
// convert points back
List <Point> convexHull = new List <Point>();
foreach (PointToProcess pt in convexHullTemp)
{
convexHull.Add(pt.ToPoint());
}
return(convexHull);
}
public List <IntPoint> FindHull(List <IntPoint> points)
{
if (points.Count <= 3)
{
return(new List <IntPoint>(points));
}
List <PointToProcess> list = new List <PointToProcess>();
foreach (IntPoint point in points)
{
list.Add(new PointToProcess(point));
}
int index = 0;
PointToProcess pointToProcess = list[0];
int i = 1;
for (int count = list.Count; i < count; i++)
{
if (list[i].X < pointToProcess.X || (list[i].X == pointToProcess.X && list[i].Y < pointToProcess.Y))
{
pointToProcess = list[i];
index = i;
}
}
list.RemoveAt(index);
int j = 0;
for (int count2 = list.Count; j < count2; j++)
{
int num = list[j].X - pointToProcess.X;
int num2 = list[j].Y - pointToProcess.Y;
list[j].Distance = num * num + num2 * num2;
list[j].K = ((num == 0) ? float.PositiveInfinity : ((float)num2 / (float)num));
}
list.Sort();
List <PointToProcess> list2 = new List <PointToProcess>();
list2.Add(pointToProcess);
list2.Add(list[0]);
list.RemoveAt(0);
PointToProcess pointToProcess2 = list2[1];
PointToProcess pointToProcess3 = list2[0];
while (list.Count != 0)
{
PointToProcess pointToProcess4 = list[0];
if (pointToProcess4.K == pointToProcess2.K || pointToProcess4.Distance == 0f)
{
list.RemoveAt(0);
}
else if ((pointToProcess4.X - pointToProcess3.X) * (pointToProcess2.Y - pointToProcess4.Y) - (pointToProcess2.X - pointToProcess4.X) * (pointToProcess4.Y - pointToProcess3.Y) < 0)
{
list2.Add(pointToProcess4);
list.RemoveAt(0);
pointToProcess3 = pointToProcess2;
pointToProcess2 = pointToProcess4;
}
else
{
list2.RemoveAt(list2.Count - 1);
pointToProcess2 = pointToProcess3;
pointToProcess3 = list2[list2.Count - 2];
}
}
List <IntPoint> list3 = new List <IntPoint>();
foreach (PointToProcess item in list2)
{
list3.Add(item.ToPoint());
}
return(list3);
}
/// <summary>
/// Find convex hull for the given set of points.
/// </summary>
///
/// <param name="points">Set of points to search convex hull for.</param>
///
/// <returns>Returns set of points, which form a convex hull for the given <paramref name="points"/>.
/// The first point in the list is the point with lowest X coordinate (and with lowest Y if there are
/// several points with the same X value). Points are provided in counter clockwise order
/// (<a href="http://en.wikipedia.org/wiki/Cartesian_coordinate_system">Cartesian
/// coordinate system</a>).</returns>
///
public List <IntPoint> FindHull(List <IntPoint> points)
{
// do nothing if there 3 points or less
if (points.Count <= 3)
{
return(new List <IntPoint>(points));
}
// find a point, with lowest X and lowest Y
int firstCornerIndex = 0;
IntPoint pointFirstCorner = points[0];
for (int i = 1, n = points.Count; i < n; i++)
{
if ((points[i].X < pointFirstCorner.X) ||
((points[i].X == pointFirstCorner.X) && (points[i].Y < pointFirstCorner.Y)))
{
pointFirstCorner = points[i];
firstCornerIndex = i;
}
}
// convert input points to points we can process
PointToProcess firstCorner = new PointToProcess(pointFirstCorner);
// Points to process must exclude the first corner that we've already found
PointToProcess[] arrPointsToProcess = new PointToProcess[points.Count - 1];
for (int i = 0; i < points.Count - 1; i++)
{
IntPoint point = points[i >= firstCornerIndex ? i + 1 : i];
arrPointsToProcess[i] = new PointToProcess(point);
}
// find K (tangent of line's angle) and distance to the first corner
for (int i = 0, n = arrPointsToProcess.Length; i < n; i++)
{
int dx = arrPointsToProcess[i].X - firstCorner.X;
int dy = arrPointsToProcess[i].Y - firstCorner.Y;
// don't need square root, since it is not important in our case
arrPointsToProcess[i].Distance = dx * dx + dy * dy;
// tangent of lines angle
arrPointsToProcess[i].K = (dx == 0) ? float.PositiveInfinity : (float)dy / dx;
}
// sort points by angle and distance
Array.Sort(arrPointsToProcess);
// Convert points to process to a queue. Continually removing the first item of an array list
// is highly inefficient
Queue <PointToProcess> queuePointsToProcess = new Queue <PointToProcess>(arrPointsToProcess);
LinkedList <PointToProcess> convexHullTemp = new LinkedList <PointToProcess>();
// add first corner, which is always on the hull
PointToProcess prevPoint = convexHullTemp.AddLast(firstCorner).Value;
// add another point, which forms a line with lowest slope
PointToProcess lastPoint = convexHullTemp.AddLast(queuePointsToProcess.Dequeue()).Value;
while (queuePointsToProcess.Count != 0)
{
PointToProcess newPoint = queuePointsToProcess.Peek();
// skip any point, which has the same slope as the last one or
// has 0 distance to the first point
if ((newPoint.K == lastPoint.K) || (newPoint.Distance == 0))
{
queuePointsToProcess.Dequeue();
continue;
}
// check if current point is on the left side from two last points
if ((newPoint.X - prevPoint.X) * (lastPoint.Y - newPoint.Y) - (lastPoint.X - newPoint.X) * (newPoint.Y - prevPoint.Y) < 0)
{
// add the point to the hull
convexHullTemp.AddLast(newPoint);
// and remove it from the list of points to process
queuePointsToProcess.Dequeue();
prevPoint = lastPoint;
lastPoint = newPoint;
}
else
{
// remove the last point from the hull
convexHullTemp.RemoveLast();
lastPoint = prevPoint;
prevPoint = convexHullTemp.Last.Previous.Value;
}
}
// convert points back
List <IntPoint> convexHull = new List <IntPoint>();
foreach (PointToProcess pt in convexHullTemp)
{
convexHull.Add(pt.ToPoint());
}
return(convexHull);
}
