Draw the perimiter of a PointF collection?
 

My brain hurts again.

I want to take a collection of PointF objects and crate a path that is the outer perimiter of the collection, so that I don't get a criss-cross problem. I'm assuming no wierd shapes with undercuts; just a collection of 'border' points. The best I could come up with is a 'Clock Hand' type radial sorting function (below). There HAS to be a better way. Anyone?


(Note: The seGpsPoint object contains a .DrawingPoint property that is a PointF object, everything else is standard)



''' <summary>
''' Sorts the DrawingPoints ofa a collection
''' of seGpsPoints in a clockwise direction
''' for use in drawing a path or polygon around
''' the outer perimeter of the collection
''' </summary>
''' <param name="GPSPointCollection">Collection of seGpsPoints to sort</param>
''' <param name="Bounds">Rectale defining sort area</param>
''' <param name="GraphicsObject">System.Graphics object to scan</param>
''' <returns></returns>
''' <remarks></remarks>


Public Function RadialSort(ByVal GPSPointCollection As Collection, ByVal Bounds As RectangleF, ByVal GraphicsObject As Graphics) As PointF()
Dim oPoint As New Point
Dim oGPS As New seGpsPoint
Dim oColl As New Collection
Dim oTemp As New Collection 'Collection of Points already captured
Dim CenterPt As New Point
Dim oMatrix As New Matrix
Dim iAngle As Integer = 0
'Set Sweep Centerpoint
CenterPt.X = CInt(Bounds.X + Bounds.Width / 2)
CenterPt.Y = CInt(Bounds.Y + Bounds.Height / 2)
Dim oSweepRect As New RectangleF
'Define Sweep Arm rectangle
oSweepRect.Y = CenterPt.Y
'Conservatively define Sweep Arm
oSweepRect.Width = Convert.ToSingle(Math.Max(10, Bounds.Width / 20))
oSweepRect.X = (CenterPt.X - oSweepRect.Width / 2)
'Trig to make sure all points are in Sweep Radius
oSweepRect.Height = Convert.ToSingle(Math.Sqrt(((Bounds.Height / 2) ^ 2 + (Bounds.Width / 2) ^ 2))) + 10
Dim oSweepRegion As New Region(oSweepRect)
'Collection of seGpsPoint Objects, each with a PointF
oColl = GPSPointCollection
'Target PointF Array to be returned length = Collection Count
Dim aryPoints(oColl.Count - 1) As PointF
'Dim return array index counter
Dim iCtr As Integer = 0
'Dim index counter for Rectange Objects
'that will approximate the Sweep Arm using
'the GetRegionScans method
Dim iIndex As Integer = 0
'Define rotation as 1 degree
oMatrix.RotateAt(1, CenterPt)
GraphicsObject.FillRegion(Brushes.Transparent, oSweepRegion)
'Make sure all 360 degrees are covered
For iAngle = 0 To 361
'This will rotate the Matrix by 1 degree
oSweepRegion.Transform(oMatrix)
GraphicsObject.FillRegion(Brushes.Transparent, oSweepRegion)
Dim aryArm() As RectangleF = oSweepRegion.GetRegionScans(oMatrix)
'This is a processor intensive bit
For iIndex = 0 To aryArm.Length - 1
For Each oGPS In GPSPointCollection
If aryArm(iIndex).Contains(oGPS.DrawingPoint) Then
Dim strKey As String
strKey = oGPS.GpsID.ToString
'Don't duplicate points, in case arms
'recapture a point on this iteration
If Not oTemp.Contains(strKey) Then
'Add seGpsPoint object and key to 'already captured' Collection
oTemp.Add(oGPS, oGPS.GpsID.ToString)
aryPoints(iCtr) = oGPS.DrawingPoint
'Increment array index when new point is captured
iCtr += 1
If iCtr = oColl.Count Then
'Commit array and exit when array is full
RadialSort = aryPoints
Exit Function
End If
End If
End If
Next
Next
Next
'This code should never be executed if all is well:
RadialSort = aryPoints
End Function