/// <summary>
/// Takes all the hull points and strings them together
/// </summary>
/// <param name="p_cho"></param>
/// <returns></returns>
private static List <Point> connectTheDots(ConvexHullObject p_cho)
{
List <Point> hullPoints = new List <Point>();
//add all of Q1
hullPoints.AddRange(p_cho.m_Q1.hullPoints);
//remove duplicates
if (hullPoints.Last().Equals(p_cho.m_Q4.hullPoints.First()))
{
hullPoints.RemoveAt(hullPoints.Count - 1);
}
hullPoints.AddRange(p_cho.m_Q4.hullPoints);
if (hullPoints.Last().Equals(p_cho.m_Q3.hullPoints.First()))
{
hullPoints.RemoveAt(hullPoints.Count - 1);
}
hullPoints.AddRange(p_cho.m_Q3.hullPoints);
if (hullPoints.Last().Equals(p_cho.m_Q2.hullPoints.First()))
{
hullPoints.RemoveAt(hullPoints.Count - 1);
}
//rinse and repeat
hullPoints.AddRange(p_cho.m_Q2.hullPoints);
if (hullPoints.Last().Equals(hullPoints.First()))
{
hullPoints.RemoveAt(hullPoints.Count - 1);
}
return(hullPoints);
}
/// <summary>
/// Using Liu and Chen's Convex shell algorithm to quicly find the outside points of the hand
/// </summary>
/// <param name="p_dataPoints"></param>
/// <returns>List of hull points</returns>
/// <seealso cref="http://www.codeproject.com/Articles/775753/A-Convex-Hull-Algorithm-and-its-implementation-in"/>
public static List <Point> getConvexHull(List <Point> p_dataPoints)
{
ConvexHullObject cho = new ConvexHullObject();
//get root points
getRoots(p_dataPoints, ref cho);
//Get the shell in each quadrant
getShell(p_dataPoints, cho);
return(connectTheDots(cho));
}
/// <summary>
/// prepare the data and send it off to be worked on in parallel
/// </summary>
/// <param name="p_dataPoints"></param>
/// <param name="p_cho"></param>
private static void getShell(List <Point> p_dataPoints, ConvexHullObject p_cho)
{
List <Point> ySortedList = p_dataPoints.OrderBy(p => p.Y).ThenBy(p => p.X).ToList();
List <Point> xSortedList = p_dataPoints.OrderBy(p => p.X).ThenBy(p => p.Y).ToList();
Parallel.Invoke(
() =>
{
p_cho.m_Q1.evaluate(ySortedList);
},
() =>
{
p_cho.m_Q2.evaluate(ySortedList);
},
() =>
{
p_cho.m_Q3.evaluate(xSortedList);
},
() =>
{
p_cho.m_Q4.evaluate(xSortedList);
});
}
/// <summary>
/// This part is to find the vertex of the extreme points thus creating 4 areas with shell points.
/// </summary>
/// <param name="p_dataPoints">data points to search</param>
/// <param name="p_cho">object that stores data</param>
private static void getRoots(List <Point> p_dataPoints, ref ConvexHullObject p_cho)
{
int xMin, yMin, xMax, yMax;
xMax = yMax = 0;
xMin = yMin = Int32.MaxValue;
foreach (Point point in p_dataPoints)
{
#region Setting Left Roots
//If this is the leftmost point set both roots Y to its Y
if (point.X < xMin)
{
//I'm worried about them having references to each other
// becuase they are not always the same
p_cho.m_Q2.xPoint = point;
p_cho.m_Q3.xPoint = point;
xMin = point.X;
}
//If the X point equals the min set the Y values to the extremes
else if (point.X == xMin)
{
if (point.Y < p_cho.m_Q2.xPoint.Y)
{
p_cho.m_Q2.xPoint = point;
}
else if (point.Y > p_cho.m_Q3.xPoint.Y)
{
p_cho.m_Q3.xPoint = point;
}
}
#endregion
#region Setting Right Roots
//If this is the rightmost point set both roots Y to its Y
else if (point.X > xMax)
{
p_cho.m_Q1.xPoint = point;
p_cho.m_Q4.xPoint = point;
xMax = point.X;
}
//If the X point equals the max, set the Y values to the extremes
else if (point.X == xMax)
{
if (point.Y < p_cho.m_Q1.xPoint.Y)
{
p_cho.m_Q1.xPoint = point;
}
else if (point.Y > p_cho.m_Q4.xPoint.Y)
{
p_cho.m_Q4.xPoint = point;
}
}
#endregion
#region Setting Top Roots
//If this is the topmost point, set both roots X to its X
if (point.Y < yMin)
{
p_cho.m_Q1.yPoint = point;
p_cho.m_Q2.yPoint = point;
yMin = point.Y;
}
//If the Y point equals the min, set the X values to the extremes
else if (point.Y == yMin)
{
if (point.X < p_cho.m_Q2.yPoint.X)
{
p_cho.m_Q2.yPoint = point;
}
else if (point.X > p_cho.m_Q1.yPoint.X)
{
p_cho.m_Q1.yPoint = point;
}
}
#endregion
#region Setting Bottom Roots
//If this is the bottommost point, set both roots X to its X
else if (point.Y > yMax)
{
p_cho.m_Q3.yPoint = point;
p_cho.m_Q4.yPoint = point;
yMax = point.Y;
}
//If the Y point equals the max, set the X values to the extremes
else if (point.Y == yMax)
{
if (point.X < p_cho.m_Q3.yPoint.X)
{
p_cho.m_Q3.yPoint = point;
}
else if (point.X > p_cho.m_Q4.yPoint.X)
{
p_cho.m_Q4.yPoint = point;
}
}
#endregion
}
}
