''' <summary>
''' The timer for getting intermediate images.
''' </summary>
Public _timer As New System.Diagnostics.Stopwatch()

''' <summary>
''' The index of intermediate image.
''' </summary>
Public _intermediateImageIndex As Integer = 0

''' <summary>
''' Time interval, in milliseconds, for getting intermediate image during rendering.
''' </summary>
Public INTERMEDIATE_RENDER_IMAGE_INTERVAL As Integer = 300



''' <summary>
''' Gets the image of PDF page.
''' </summary>
''' <param name="page">The page of PDF document.</param>
Public Function RenderPdfPageProgressively(page As Vintasoft.Imaging.Pdf.Tree.PdfPage) As Vintasoft.Imaging.VintasoftImage
    _intermediateImageIndex = 0
    ' start timer
    _timer.Start()

    ' render PDF page progressively
    Dim image As Vintasoft.Imaging.VintasoftImage = page.Render(page.CropBox, 1F, Nothing, New System.EventHandler(Of Vintasoft.Imaging.ImageRendering.IntermediateImageRequestEventArgs)(AddressOf IntermediateImageRequest))

    ' stop timer
    _timer.[Stop]()

    ' return the result image
    Return image
End Function

''' <summary>
''' Handler of event that occurs when intermediate image is ready and can be obtained.
''' </summary>
Public Sub IntermediateImageRequest(sender As Object, e As Vintasoft.Imaging.ImageRendering.IntermediateImageRequestEventArgs)
    ' if intermediate image must be saved
    If _timer.ElapsedMilliseconds >= INTERMEDIATE_RENDER_IMAGE_INTERVAL Then
        ' reset timer
        _timer.Reset()
        ' set the delegate which invoked for obtaining the intermediate image
        e.IntermediateImageCompleted = New Vintasoft.Imaging.ImageRendering.IntermediateImageCompletedDelegate(AddressOf IntermediateImageReady)
        ' start timer
        _timer.Start()
    End If
End Sub

''' <summary>
''' Delegate that allows to obtain intermediate image.
''' </summary>
Public Sub IntermediateImageReady(e As Vintasoft.Imaging.ImageRendering.IntermediateImageReadyEventArgs)
    ' increment counter of intermediate images
    _intermediateImageIndex += 1

    ' clone the rendered image
    Using image As Vintasoft.Imaging.VintasoftImage = DirectCast(e.Image.Clone(), Vintasoft.Imaging.VintasoftImage)
        Dim filename As String = String.Format("IntermediateImage_{0}.bmp", _intermediateImageIndex.ToString("00"))
        ' save the intermediate image to a file
        image.Save(filename)
    End Using
End Sub

/// <summary>
/// The timer for getting intermediate images.
/// </summary>
public System.Diagnostics.Stopwatch _timer = new System.Diagnostics.Stopwatch();

/// <summary>
/// The index of intermediate image.
/// </summary>
public int _intermediateImageIndex = 0;

/// <summary>
/// Time interval, in milliseconds, for getting intermediate image during rendering.
/// </summary>
public int INTERMEDIATE_RENDER_IMAGE_INTERVAL = 300;



/// <summary>
/// Gets the image of PDF page.
/// </summary>
/// <param name="page">The page of PDF document.</param>
public Vintasoft.Imaging.VintasoftImage RenderPdfPageProgressively(
    Vintasoft.Imaging.Pdf.Tree.PdfPage page)
{
    _intermediateImageIndex = 0;
    // start timer
    _timer.Start();

    // render PDF page progressively
    Vintasoft.Imaging.VintasoftImage image = page.Render(page.CropBox, 1.0f, null,
        new System.EventHandler<Vintasoft.Imaging.ImageRendering.IntermediateImageRequestEventArgs>(IntermediateImageRequest));

    // stop timer
    _timer.Stop();

    // return the result image
    return image;
}

/// <summary>
/// Handler of event that occurs when intermediate image is ready and can be obtained.
/// </summary>
public void IntermediateImageRequest(object sender, Vintasoft.Imaging.ImageRendering.IntermediateImageRequestEventArgs e)
{
    // if intermediate image must be saved
    if (_timer.ElapsedMilliseconds >= INTERMEDIATE_RENDER_IMAGE_INTERVAL)
    {
        // reset timer
        _timer.Reset();
        // set the delegate which invoked for obtaining the intermediate image
        e.IntermediateImageCompleted =
            new Vintasoft.Imaging.ImageRendering.IntermediateImageCompletedDelegate(IntermediateImageReady);
        // start timer
        _timer.Start();
    }
}

/// <summary>
/// Delegate that allows to obtain intermediate image.
/// </summary>
public void IntermediateImageReady(Vintasoft.Imaging.ImageRendering.IntermediateImageReadyEventArgs e)
{
    // increment counter of intermediate images
    _intermediateImageIndex++;

    // clone the rendered image
    using (Vintasoft.Imaging.VintasoftImage image =
        (Vintasoft.Imaging.VintasoftImage)e.Image.Clone())
    {
        string filename = string.Format("IntermediateImage_{0}.bmp", _intermediateImageIndex.ToString("00"));
        // save the intermediate image to a file
        image.Save(filename);
    }
}