Public Class Form1
  Dim m_mfi As New cMultiFrameImage

  Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
    m_mfi.LoadFromFile("c:\111\test.tif")
  End Sub

  Private Sub ButtonShow_Click(sender As Object, e As EventArgs) Handles ButtonShow.Click
    PictureBox1.Image = m_mfi.Zoom(, PictureBox1.Width, 0)
  End Sub
...


Public Class cMultiFrameImage
  Private m_Bitmap As Bitmap
  Private m_nFrameCount As Integer
  Private m_nFrameIndex As Integer

  Public Sub LoadFromFile(ByVal FileName As String)
    Clear()
    m_nFrameCount = 0
    m_nFrameIndex = 0
    If IO.File.Exists(FileName) = False Then Exit Sub
    Try : m_Bitmap = New Bitmap(FileName) : Catch : End Try
  End Sub

  Public ReadOnly Property FrameCount() As Integer
    Get
      If m_nFrameCount = 0 Then
        If Not m_Bitmap Is Nothing Then
          Try : m_nFrameCount = m_Bitmap.GetFrameCount(FrameDimension.Page) : Catch : End Try
        End If
      End If
      Return m_nFrameCount
    End Get
  End Property

  Public Property frameIndex() As Integer
    Set(ByVal nFrame As Integer)
      If (nFrame > 0) And (nFrame <= FrameCount) Then
        Try
          m_Bitmap.SelectActiveFrame(FrameDimension.Page, nFrame - 1)
          m_nFrameIndex = nFrame
        Catch
        End Try
      End If
    End Set
    Get
      If m_Bitmap Is Nothing Then
        m_nFrameIndex = 0
      ElseIf m_nFrameIndex = 0 Then
        m_nFrameIndex = 1
      End If
      Return m_nFrameIndex
    End Get
  End Property
...
  Public Function Zoom(Optional ByVal nFrame As Integer = 0, _
   Optional ByVal MaxWidth As Integer = 0, _
   Optional ByVal MaxHeight As Integer = 0) As Bitmap
    Dim nActiveFrame As Integer
    Dim nSrcWidth As Integer
    Dim nSrcHeight As Integer
    Dim nDstWidth As Integer
    Dim nDstHeight As Integer
    Dim r0 As Double

    If nFrame = 0 Then
      If m_Bitmap Is Nothing Then Return Nothing
    ElseIf (nFrame > 0) And (nFrame <= FrameCount) Then
      nActiveFrame = frameIndex
      frameIndex = nFrame
    Else
      Return Nothing
    End If
...

    Dim bmDst As New Bitmap(nDstWidth, nDstHeight)
    Using gr As Graphics = Graphics.FromImage(bmDst)
      gr.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
      gr.PixelOffsetMode = Drawing2D.PixelOffsetMode.HighQuality
      gr.CompositingQuality = Drawing2D.CompositingQuality.HighQuality

      gr.CompositingMode = Drawing2D.CompositingMode.SourceOver
      gr.InterpolationMode = Drawing2D.InterpolationMode.Bilinear
      gr.DrawImage(m_Bitmap, 0, 0, nDstWidth, nDstHeight)
    End Using
    Return bmDst
  End Function

  Public Sub Clear()
    If Not m_Bitmap Is Nothing Then
      m_Bitmap.Dispose()
      m_Bitmap = Nothing
    End If
  End Sub

  Protected Overrides Sub Finalize()
    Clear()
    MyBase.Finalize()
  End Sub

    Using gr As Graphics = Graphics.FromImage(bmDst)
...
    End Using

Private Sub Class_Terminate()
  If m_nBitmap Then GdipExec GdipDisposeImage(m_nBitmap)
  If m_GdipSession Then GdipExec GdiplusShutdown(m_GdipSession)
End Sub