public partial class ImageViewer_ExternalScrollBars : System.Windows.Forms.Form
{

    #region Constructors

    public ImageViewer_ExternalScrollBars()
    {
        InitializeComponent();
        // ...
        imageViewer.ZoomChanged += new System.EventHandler<Vintasoft.Imaging.UI.ZoomChangedEventArgs>(imageViewer_ZoomChanged);
        imageViewer.ImageLoaded += new System.EventHandler<Vintasoft.Imaging.ImageLoadedEventArgs>(imageViewer_ImageLoaded);
        imageViewer.SizeChanged += new System.EventHandler(imageViewer_SizeChanged);
        hScrollBar1.ValueChanged += new System.EventHandler(ScrollBar_ValueChanged);
        vScrollBar1.ValueChanged += new System.EventHandler(ScrollBar_ValueChanged);

        imageViewer.AutoScroll = false;
        // ...
    }

    #endregion



    #region Methods

    /// <summary>
    /// Image viewer size is changed.
    /// </summary>
    private void imageViewer_SizeChanged(object sender, System.EventArgs e)
    {
        SetScrollBarParams();
    }

    /// <summary>
    /// Image is loaded in image viewer.
    /// </summary>
    private void imageViewer_ImageLoaded(object sender, Vintasoft.Imaging.ImageLoadedEventArgs e)
    {
        SetScrollBarParams();
    }

    /// <summary>
    /// Image viewer zoom is changed.
    /// </summary>
    private void imageViewer_ZoomChanged(object sender, Vintasoft.Imaging.UI.ZoomChangedEventArgs e)
    {
        SetScrollBarParams();
    }

    /// <summary>
    /// Sets parameters of scroll bars.
    /// </summary>
    private void SetScrollBarParams()
    {
        // initialize horizontal scroll bar
        int width = imageViewer.ViewerState.AutoScrollSize.Width;
        hScrollBar1.Minimum = 0;
        hScrollBar1.Maximum = width + width / 5;
        hScrollBar1.LargeChange = width / 5;
        hScrollBar1.SmallChange = width / 20;
        hScrollBar1.Enabled = width != 0;

        // initialize vertical scroll bar
        int height = imageViewer.ViewerState.AutoScrollSize.Height;
        vScrollBar1.Minimum = 0;
        vScrollBar1.Maximum = height + height / 5;
        vScrollBar1.LargeChange = height / 5;
        vScrollBar1.SmallChange = height / 20;
        vScrollBar1.Enabled = height != 0;
    }

    /// <summary>
    /// Scrollbar value is changed.
    /// </summary>
    private void ScrollBar_ValueChanged(object sender, System.EventArgs e)
    {
        System.Drawing.PointF currentPosition =
            new System.Drawing.PointF((float)hScrollBar1.Value, (float)vScrollBar1.Value);
        imageViewer.ViewerState.AutoScrollPosition = currentPosition;
    }

    #endregion

}

Public Partial Class ImageViewer_ExternalScrollBars
    Inherits System.Windows.Forms.Form

    #Region "Constructors"

    Public Sub New()
        InitializeComponent()
        ' ...
        AddHandler imageViewer.ZoomChanged, New System.EventHandler(Of Vintasoft.Imaging.UI.ZoomChangedEventArgs)(AddressOf imageViewer_ZoomChanged)
        AddHandler imageViewer.ImageLoaded, New System.EventHandler(Of Vintasoft.Imaging.ImageLoadedEventArgs)(AddressOf imageViewer_ImageLoaded)
        AddHandler imageViewer.SizeChanged, New System.EventHandler(AddressOf imageViewer_SizeChanged)
        AddHandler hScrollBar1.ValueChanged, New System.EventHandler(AddressOf ScrollBar_ValueChanged)
        AddHandler vScrollBar1.ValueChanged, New System.EventHandler(AddressOf ScrollBar_ValueChanged)

            ' ...
        imageViewer.AutoScroll = False
    End Sub

    #End Region



    #Region "Methods"

    ''' <summary>
    ''' Image viewer size is changed.
    ''' </summary>
    Private Sub imageViewer_SizeChanged(sender As Object, e As System.EventArgs)
        SetScrollBarParams()
    End Sub

    ''' <summary>
    ''' Image is loaded in image viewer.
    ''' </summary>
    Private Sub imageViewer_ImageLoaded(sender As Object, e As Vintasoft.Imaging.ImageLoadedEventArgs)
        SetScrollBarParams()
    End Sub

    ''' <summary>
    ''' Image viewer zoom is changed.
    ''' </summary>
    Private Sub imageViewer_ZoomChanged(sender As Object, e As Vintasoft.Imaging.UI.ZoomChangedEventArgs)
        SetScrollBarParams()
    End Sub

    ''' <summary>
    ''' Sets parameters of scroll bars.
    ''' </summary>
    Private Sub SetScrollBarParams()
        ' initialize horizontal scroll bar
        Dim width As Integer = imageViewer.ViewerState.AutoScrollSize.Width
        hScrollBar1.Minimum = 0
        hScrollBar1.Maximum = width + width \ 5
        hScrollBar1.LargeChange = width \ 5
        hScrollBar1.SmallChange = width \ 20
        hScrollBar1.Enabled = width <> 0

        ' initialize vertical scroll bar
        Dim height As Integer = imageViewer.ViewerState.AutoScrollSize.Height
        vScrollBar1.Minimum = 0
        vScrollBar1.Maximum = height + height \ 5
        vScrollBar1.LargeChange = height \ 5
        vScrollBar1.SmallChange = height \ 20
        vScrollBar1.Enabled = height <> 0
    End Sub

    ''' <summary>
    ''' Scrollbar value is changed.
    ''' </summary>
    Private Sub ScrollBar_ValueChanged(sender As Object, e As System.EventArgs)
        Dim currentPosition As New System.Drawing.PointF(CSng(hScrollBar1.Value), CSng(vScrollBar1.Value))
        imageViewer.ViewerState.AutoScrollPosition = currentPosition
    End Sub

    #End Region

End Class