Private bmp1 As New Bitmap(500, 200)
Private G1 As Graphics
 
Private lastX As Integer = -1
Private lastY As Integer = 0
 
Dim r As New Random
 
Private G2 As Graphics
Private bmp2 As New Bitmap(500, 200)
 
Dim data As Integer()
Dim index As Integer
 
Dim drawmode As Boolean
 
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles MyBase.Load
 
    data = CType(Array.CreateInstance(GetType(Integer), 250), Integer())
 
    G1 = Graphics.FromImage(bmp1)
    G1.Clear(Color.White)
 
    G1.TranslateTransform(0, bmp1.Height \ 2)
    G1.ScaleTransform(2, -1)
    G1.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
 
 
    G2 = Graphics.FromImage(bmp2)
    G2.Clear(Color.White)
 
    G2.TranslateTransform(0, bmp2.Height \ 2)
    G2.ScaleTransform(2, -1)
    G2.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
 
    PictureBox1.Image = bmp1
 
End Sub
 
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Timer1.Tick
 
    Dim x As Integer = (lastX + 1) Mod bmp1.Width \ 2
    Dim y As Integer = CInt(r.Next(70, 90) * Math.Sin((Environment.TickCount + _
      r.Next(100)) / 400))
 
    G1.FillRectangle(Brushes.White, x, -bmp1.Height \ 2, 5, bmp1.Height)
 
    If x > lastX Then
        G1.DrawLine(Pens.Green, lastX, lastY, x, y)
    Else
        G1.DrawLine(Pens.Green, -1, lastY, x, y)
    End If
 
    lastX = x
    lastY = y
 
    G1.Flush()
 
    G2.Clear(Color.White)
 
    index = val(1)
    data(index) = y
 
    G2.DrawLine(Pens.Blue, -1, data(val(0)), 0, data(val(0)))
    For i As Integer = 1 To data.Length - 1
        G2.DrawLine(Pens.Blue, i - 1, data(val(i - 1)), i, data(val(i)))
    Next
 
    G2.Flush()
 
    PictureBox1.Refresh()
End Sub
 
Private Function val(ByVal i As Integer) As Integer
    Return (index + data.Length + i) Mod data.Length
End Function
 
Private Sub PictureBox1_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles PictureBox1.Click
    If drawmode Then
        PictureBox1.Image = bmp1
    Else
        PictureBox1.Image = bmp2
    End If
    drawmode = Not drawmode
End Sub