How to perform 2D picture plotting

Public Function ColorGradient(ByVal Value As Single) As Brush
    Dim val As Single
    Dim bt As Byte

    Val = 1 - Math.Abs(Value) * 10 / 3
    If Val() > 1 Then Val = 1
    If Val() < 0 Then Val = 0
    bt = Val() * 255

    If Value > 0 Then
        'Red color
        Return New SolidColorBrush(Color.FromRgb(255, bt, bt))
    ElseIf Value < 0 Then
        'Blue color
        Return New SolidColorBrush(Color.FromRgb(bt, bt, 255))
    Else
        'White color
        Return New SolidColorBrush(Colors.White)
    End If
End Function

Private Function MidPointKelvin(ByVal x As Double, ByVal y As Double)
    Dim m As Double = 80
    Dim h As Double = Math.PI / (2 * m)
    Dim p As Double = 0.001
    Dim pheda, t1, t2, sum, g1, gp1, cg1, sg1, sgp1 As Double
    sum = 0
    For i As Integer = 1 To m
        pheda = -(Math.PI / 2) + (2 * i - 1) * h
        g1 = g0(x, y, pheda)
        gp1 = gp(x, y, pheda)
        cg1 = Math.Sin(gp1 * h)
        sg1 = Math.Sin(g1)
        sgp1 = Math.Sin(gp1 * h)
        t1 = p * 2 * h * cg1
        t2 = 2 * gp1 * cg1 * sgp1
        sum = sum + (t1 + t2) / (p + gp1 ^ 2)
    Next
    Return sum
End Function

Private Function g0(ByVal x As Double, ByVal y As Double, ByVal p As Double) As Double
    Return (x - y * Math.Tan(p)) / Math.Cos(p)
End Function

Private Function gp(ByVal x As Double, ByVal y As Double, ByVal p As Double) As Double
    Return -(1 / Math.Cos(p)) ^ 3 + (1 / Math.Cos(p)) * Math.Tan(p) * (x - y * Math.Tan(p))
End Function