Here is an example of how the Douglas-Peucker, Visvalingam-Whyatt, and Reumann-Witkam line simplification algorithms can be implemented in VB.net:
Douglas-Peucker algorithm:
Public Function DouglasPeucker(ByVal points As List(Of PointF), ByVal tolerance As Double) As List(Of PointF)
Dim dmax As Double = 0
Dim index As Integer = 0
For i As Integer = 2 To points.Count - 1
Dim d As Double = PerpendicularDistance(points(i), New LineF(points(0), points(points.Count - 1)))
If d > dmax Then
index = i
dmax = d
End If
Next
If dmax > tolerance Then
Dim recResults1 As List(Of PointF) = DouglasPeucker(points.GetRange(0, index + 1), tolerance)
Dim recResults2 As List(Of PointF) = DouglasPeucker(points.GetRange(index, points.Count - index), tolerance)
recResults1.AddRange(recResults2)
Return recResults1
Else
Dim result As New List(Of PointF)
result.Add(points(0))
result.Add(points(points.Count - 1))
Return result
End If
End Function
Visvalingam-Whyatt algorithm:
Public Function VisvalingamWhyatt(ByVal points As List(Of PointF), ByVal tolerance As Double) As List(Of PointF)
For i As Integer = 0 To points.Count - 3
Dim area As Double = Area(points(i), points(i + 1), points(i + 2))
If area < tolerance Then
points.RemoveAt(i + 1)
End If
Next
Return points
End Function
Reumann-Witkam algorithm:
Public Function ReumannWitkam(ByVal points As List(Of PointF), ByVal tolerance As Double) As List(Of PointF)
For i As Integer = 0 To points.Count - 2
Dim d As Double = point_line_distance(points(i), New LineF(points(0), points(points.Count - 1)))
If d > tolerance Then
points.RemoveAt(i)
End If
Next
Return points
End Function
In these implementations, the input is a list of PointF and the tolerance value is a real number used to define the level of simplification. The output is a simplified version of the input line, represented as a list of PointF. It’s important to note that the above code examples are just a representation of the algorithm and may not be fully functional or optimized for specific use cases. They also may require additional functions such as PerpendicularDistance and point_line_distance to be defined and implemented as well. Also, as VB.net is an event-driven programming language, It’s important to consider the performance of these functions when working with large datasets, as they may be affected by the number of operations required by the algorithm. It’s also important to consider the specific requirements of your application and make any necessary adjustments to the code to ensure it meets those requirements.
