Imports System.Drawing.Imaging

Public Class Form1
  Dim Buffer As Bitmap
  Dim graph As Graphics
  Dim Xtmr As Integer

  Private Sub Winkelscroll_Scroll(ByVal sender As System.Object, _
        ByVal e As System.Windows.Forms.ScrollEventArgs) Handles _
        Winkelscroll.Scroll
    Winkelanz.Text = Winkelscroll.Value / 10 & "°"
  End Sub

  Private Sub Form1_Load(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles MyBase.Load
    Buffer = New Bitmap(PictureBox1.Width, PictureBox1.Height, _
          PixelFormat.Format32bppPArgb)
    graph = Graphics.FromImage(Buffer)
    Call DreheBild()
  End Sub

  Private Sub DreheBild()
    graph.Clear(Color.Transparent)
    graph.ResetTransform()
    graph.TranslateTransform(PictureBox1.Width / 2, _
          PictureBox1.Height / 2, Drawing2D.MatrixOrder.Append)
    graph.RotateTransform(Winkelscroll.Value / 10)
    graph.DrawImage(PictureBox1.Image, _
          New Rectangle(-PictureBox1.Width / 2, _
          -PictureBox1.Height / 2, PictureBox1.Width, _
          PictureBox1.Height))
    Vorschau.Image = Buffer
  End Sub

  Private Sub Go_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Go.Click
    Call DreheBild()
  End Sub

  Private Sub einst1_SelectedIndexChanged(ByVal sender As _
        System.Object, ByVal e As System.EventArgs) Handles _
        einst1.SelectedIndexChanged
    On Error Resume Next
    Select Case einst1.Text
      Case "HighQualityBicubic"
        graph.InterpolationMode = _
              Drawing2D.InterpolationMode.HighQualityBicubic
      Case "Bicubic"
        graph.InterpolationMode = _
              Drawing2D.InterpolationMode.Bicubic
      Case "Bilinear"
        graph.InterpolationMode = _
              Drawing2D.InterpolationMode.Bilinear
      Case "High"
        graph.InterpolationMode = Drawing2D.InterpolationMode.High
      Case "HighQualityBilinear"
        graph.InterpolationMode = _
              Drawing2D.InterpolationMode.HighQualityBilinear
      Case "Low"
        graph.InterpolationMode = Drawing2D.InterpolationMode.Low
      Case "NearestNeighbor"
        graph.InterpolationMode = _
              Drawing2D.InterpolationMode.NearestNeighbor
    End Select
    Call DreheBild()
  End Sub

  Private Sub DemoTMR_Tick(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles DemoTMR.Tick
    Winkelscroll.Value = Winkelscroll.Value + Xtmr
    Winkelanz.Text = Winkelscroll.Value / 10 & "°"
    If Winkelscroll.Value >= 3600 Then
      Xtmr = -10
    End If
    If Winkelscroll.Value <= -3600 Then
      Xtmr = 10
    End If
    Call DreheBild()
  End Sub

  Private Sub Button1_Click(ByVal sender As System.Object, _
        ByVal e As System.EventArgs) Handles Button1.Click
    If Button1.Text = "Demo starten" Then
      Button1.Text = "Demo beenden"
      DemoTMR.Enabled = True
      Xtmr = 10
      Winkelscroll.Value = CInt(Winkelscroll.Value / 10) * 10
    Else
      Button1.Text = "Demo starten"
      DemoTMR.Enabled = False
    End If
  End Sub
End Class