[Visual Studio 2015] Changer la couleur d'une portion d'une courbe sur un graphique

bonjour

2 séries de points -Positive (Ord Y > origine Oy de référence) et Négative( Ord Y < origine Oy de référencé) suffisent si tu utilises soit :
-Graphics.DrawCurve (pen,points())
-GraphicsPath.AddCurve(points())
Curve c'est pour une courbe spline cardinale ...

exemple code pour sinus avec GraphicsPath ,un Form & un Panel droppé sur le Form:

Code:

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Imports System.Drawing.Drawing2D
 
Public Class Form1
 
    Private Sub Panel1_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Panel1.Paint
        Dim gr As Graphics = e.Graphics
        gr.SmoothingMode = SmoothingMode.HighQuality
        drawPath(gr)
    End Sub
 
    Private Sub drawPath(ByVal gr As Graphics)
        Dim angle As Single
        Dim pt As PointF
 
        Dim PostivePts As New List(Of PointF)
        Dim NegativePts As New List(Of PointF)
        For i As Integer = 0 To 718
            angle = i * Math.PI / 180
            pt = New PointF()
            pt.X = angle * 50.0
            pt.Y = 100 * Math.Sin(angle)
            pt.Y += Panel1.Height / 2
            If pt.Y > Panel1.Height / 2 Then
                PostivePts.Add(pt)
            Else
                NegativePts.Add(pt)
            End If
        Next
 
        Using path As New GraphicsPath
 
            path.AddCurve(PostivePts.ToArray)
            gr.DrawPath(Pens.Red, path)
            path.Reset()
            path.AddCurve(NegativePts.ToArray)
            gr.DrawPath(Pens.Green, path)
 
        End Using
 
        Dim p0 As PointF = PostivePts(0)
        Dim p1 As PointF = NegativePts(NegativePts.Count - 1)
        Using myPen As New Pen(Brushes.DarkBlue, 2.0)
            myPen.DashStyle = DashStyle.DashDot
            gr.DrawLine(myPen, p0, p1)
        End Using
 
 
    End Sub
 
    Private Sub Form1_Resize(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Resize
        Panel1.Invalidate()
 
    End Sub
End Class

bon code....