Public Class RandomColors
 
    Dim _coltab As New DataTable
    Dim _mindiff As Integer
    Dim _rndm As New Random
 
    ''' <summary>Erstellung einer Liste mit Zufallsfarben </summary>
    ''' <param name="Count">Anzahl der Farben (1-300)</param>
    ''' <param name="MinDiff">Mindestdifferenz, RGB gewichtet (0-30)</param>
    Public Sub New(ByVal Count As Integer, ByVal MinDiff As Integer)
 
        If Count < 1 Then Throw New Exception("Keine Farbe angefordert")
        If Count > 300 Then Throw New Exception("Zu viele Farben")
        If MinDiff < 0 Or MinDiff > 30 Then Throw New Exception("Ungültige" & _
          "Schranke")
 
        _coltab.TableName = "RandomColors"
        _coltab.Columns.Add("Red", GetType(Byte))
        _coltab.Columns.Add("Green", GetType(Byte))
        _coltab.Columns.Add("Blue", GetType(Byte))
 
        _mindiff = MinDiff
        Dim counter As Integer, newcolor As Color
        For i As Integer = 0 To Count - 1
            _coltab.Rows.Add({0, 0, 0}) : counter = 0
            Do
                newcolor = RandomColor()
                counter += 1
                If counter > 500 Then
                    Throw New Exception("Ungeeignete Parameter")
                End If
            Loop While Not CheckColor(newcolor)
 
            _coltab.Rows(i)("Red") = newcolor.R
            _coltab.Rows(i)("Green") = newcolor.G
            _coltab.Rows(i)("Blue") = newcolor.B
        Next i
    End Sub
 
    ''' <summary>Abfrage einer Farbe </summary>
    ''' <param name="index">Index der Liste</param>
    Public ReadOnly Property GetColor(ByVal index As Integer) As Color
        Get
            Return Color.FromArgb(CInt(_coltab(index)("Red")), _
                                  CInt(_coltab(index)("Green")), _
                                  CInt(_coltab(index)("Blue")))
        End Get
    End Property
 
    ''' <summary> Anzahl der Farben </summary>
    Public ReadOnly Property Count() As Integer
        Get
            Return _coltab.Rows.Count
        End Get
    End Property
 
    ''' <summary>Farben speichern</summary>
    Public Function Save(ByVal Filename As String) As Boolean
        Try
            _coltab.WriteXml(Filename, XmlWriteMode.WriteSchema)
            Return True
        Catch ex As Exception
            Return False
        End Try
    End Function
 
    ''' <summary>Farben laden</summary>
    Public Function Load(ByVal Filename As String) As Boolean
        Try
            _coltab.Rows.Clear()
            Dim rm As XmlReadMode = _coltab.ReadXml(Filename)
            Return True
        Catch ex As Exception
            Return False
        End Try
    End Function
 
    Private Function RandomColor() As Color
        Return Color.FromArgb(_rndm.Next(0, 256), 
               _rndm.Next(0, 256), _rndm.Next(0, 256))
    End Function
 
    Private Function CheckColor(ByVal testcolor As Color) As Boolean
        For i As Integer = 0 To _coltab.Rows.Count - 1
            If ColorDiff(GetColor(i), testcolor) < _mindiff Then Return False
        Next i
        Return True
    End Function
 
    Private Function ColorDiff(ByVal a As Color, ByVal b As Color) As Integer
        Return CInt(Math.Abs(CInt(a.R) - b.R) * 0.5) + _
         CInt(Math.Abs(CInt(a.G) - b.G) * 0.4 + _
         CInt(Math.Abs(CInt(a.B) - b.B) * 0.1))
    End Function
 
End Class