vb验证码制作求助

Private Sub CreateValidImage(ByVal checkCode As String)
  Dim iWidth As Integer = checkCode.Length * 15
  Dim image As New Bitmap(iWidth, 25) '图片大小
  Dim g As Graphics = Graphics.fromImage(image)
  g.Clear(Color.White)
  Dim c As Color() = {Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Red, Color.Brown, Color.DarkCyan, Color.Purple}
  Dim font As String() = {"Verdana", "System", "Comic Sans MS", "Arial", "宋体"}
  Dim rand As New Random()
  Dim j As Short
  For j = 0 To checkCode.Length - 1
  Dim tmpPoint = New Point()
  Dim cIndex As Short = rand.Next(8)  
 Dim fIndex As Short = rand.Next(5)  
 Dim f As New Font(font(fIndex), 12, FontStyle.Regular) '12磅，斜体）
  Dim b As New SolidBrush(c(cIndex))  
  Dim dg = rand.Next(10, 50)
  If (rand.Next(0, 2) = 0) Then
  tmpPoint.x = 12
  tmpPoint.y = -6
  Else
  dg = -dg + 1
  tmpPoint.x = -10
  tmpPoint.y = 6
  End If
  g.RotateTransform(dg)