Private VSTwain1 As New VintaSoftTwain()


''' <summary>
''' Scans images asynchronously.
''' </summary>
Private Sub StartScan()
    ' open the device manager
    If Not VSTwain1.DeviceManager_Open() Then
        Console.WriteLine(VSTwain1.errorString)
        Exit Sub
    End If

    ' select device using standard device selection dialog
    VSTwain1.DeviceManager_ShowDefaultDeviceSelectionDialog()

    ' open the device manager
    If Not VSTwain1.Device_Open() Then
        Console.WriteLine(VSTwain1.errorString)
        Exit Sub
    End If

    ' specify that device UI must be shown
    VSTwain1.Device_ShowUI = True

    ' specify that acquired image must be added to an existing TIFF file
    VSTwain1.TiffEncoder_MultiPage = True

    ' subscribe to the device events
    AddHandler VSTwain1.DeviceImageAcquired, AddressOf VSTwain1_ImageAcquired
    AddHandler VSTwain1.DeviceScanCompleted, AddressOf VSTwain1_ScanCompleted
    AddHandler VSTwain1.DeviceScanFailed, AddressOf VSTwain1_ScanFailed
    AddHandler VSTwain1.DeviceScanCanceled, AddressOf VSTwain1_ScanCanceled

    ' acquire images asynchronously
    VSTwain1.Device_AcquireImage()
End Sub

Private Sub VSTwain1_ImageAcquired()
    ' get index of acquired image
    Dim imageIndex As Integer = VSTwain1.AcquiredImages_Count - 1

    ' despeckle image
    If Not VSTwain1.AcquiredImages_Despeckle(imageIndex, 8, 25, 30, 400) Then
        Console.WriteLine(VSTwain1.errorString)
    Else
        ' deskew image
        If Not VSTwain1.AcquiredImages_Deskew(imageIndex, IMAGEPROCESSINGBORDERCOLOR.IMAGEPROCESSINGBORDERCOLOR_AutoDetect, 5, 5) Then
            Console.WriteLine(VSTwain1.errorString)
        Else
            ' remove image border
            If Not VSTwain1.AcquiredImages_DetectBorder(imageIndex, 5) Then
                Console.WriteLine(VSTwain1.errorString)
            End If
        End If
    End If

    Dim currentNoiseLevel As Single
    ' if image is NOT blank
    If Not VSTwain1.AcquiredImages_IsBlank(imageIndex, 0.001, currentNoiseLevel) Then
        ' add image to TIFF file
        VSTwain1.AcquiredImages_Save(imageIndex, "d:\test.tif")
    End If
End Sub

Private Sub VSTwain1_ScanCompleted()
    Console.WriteLine("Scan is completed.")
End Sub

Private Sub VSTwain1_ScanFailed(errorString As String)
    Console.WriteLine(String.Format("Scan is failed: {0}.", errorString))
End Sub

Private Sub VSTwain1_ScanCanceled()
    Console.WriteLine("Scan is canceled.")
End Sub