Public Partial Class FormWithPdfImageExtractorTool
    Inherits System.Windows.Forms.Form
    '...
    Private _imageViewer As Vintasoft.Imaging.UI.ImageViewer
    Private _imageExtractorTool As Vintasoft.Imaging.Pdf.UI.PdfImageExtractorTool
    '...
    Public Sub New()
        '...
        ' create an instance of the PdfImageExtractorTool
        _imageExtractorTool = New Vintasoft.Imaging.Pdf.UI.PdfImageExtractorTool()

        ' set a pen and brush for image selection
        _imageExtractorTool.SelectionBrush = New System.Drawing.SolidBrush(System.Drawing.Color.FromArgb(32, System.Drawing.Color.Blue))
        _imageExtractorTool.SelectionPen = System.Drawing.Pens.Red

        ' subscribe to image extractor events
        AddHandler _imageExtractorTool.ImageMouseEnter, New System.EventHandler(Of Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs)(AddressOf _pdfImageExtractorTool_ImageMouseEnter)
        AddHandler _imageExtractorTool.ImageMouseLeave, New System.EventHandler(Of Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs)(AddressOf _pdfImageExtractorTool_ImageMouseLeave)

        ' set the image extractor tool as current tool
        _imageViewer.VisualTool = _imageExtractorTool
    End Sub

    ' Occurs when the mouse pointer enters the image on PDF page.
    Private Sub _pdfImageExtractorTool_ImageMouseEnter(sender As Object, e As Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs)
        ' set the focused image as selected image
        _imageExtractorTool.SelectedImage = e.ContentImage
    End Sub

    ' Occurs when the mouse pointer leaves the image on PDF page.
    Private Sub _pdfImageExtractorTool_ImageMouseLeave(sender As Object, e As Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs)
        ' remove selected image from image extractor tool
        _imageExtractorTool.SelectedImage = Nothing
    End Sub
End Class

public partial class FormWithPdfImageExtractorTool : System.Windows.Forms.Form
{
    //...
    Vintasoft.Imaging.UI.ImageViewer _imageViewer;
    Vintasoft.Imaging.Pdf.UI.PdfImageExtractorTool _imageExtractorTool;
    //...
    public FormWithPdfImageExtractorTool()
    {
        //...
        // create an instance of the PdfImageExtractorTool
        _imageExtractorTool = new Vintasoft.Imaging.Pdf.UI.PdfImageExtractorTool();

        // set a pen and brush for image selection
        _imageExtractorTool.SelectionBrush = 
            new System.Drawing.SolidBrush(
                System.Drawing.Color.FromArgb(32, System.Drawing.Color.Blue));
        _imageExtractorTool.SelectionPen = System.Drawing.Pens.Red;

        // subscribe to image extractor events
        _imageExtractorTool.ImageMouseEnter += 
            new System.EventHandler<Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs>(_pdfImageExtractorTool_ImageMouseEnter);
        _imageExtractorTool.ImageMouseLeave += 
            new System.EventHandler<Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs>(_pdfImageExtractorTool_ImageMouseLeave);

        // set the image extractor tool as current tool
        _imageViewer.VisualTool = _imageExtractorTool;
    }

    // Occurs when the mouse pointer enters the image on PDF page.
    void _pdfImageExtractorTool_ImageMouseEnter(object sender, Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs e)
    {
        // set the focused image as selected image
        _imageExtractorTool.SelectedImage = e.ContentImage;
    }

    // Occurs when the mouse pointer leaves the image on PDF page.
    void _pdfImageExtractorTool_ImageMouseLeave(object sender, Vintasoft.Imaging.Pdf.UI.PdfImageExtractorEventArgs e)
    {
        // remove selected image from image extractor tool
        _imageExtractorTool.SelectedImage = null;
    }
}