WIA 2.0 - Alterar resolução DPI

[Shafick 0]

Boas!

Estou usando o Microsoft Windows Image Acquisition Library v2.0 (WIA) para digitalizar imagens. Porém, cada imagem está ficando com 25mb em média (jpg, bmp, png, gif ou tiff da na mesma). A ideia é converter para PDF após a digitalização; mesmo assim, o arquivo PDF está ficando com 8mb em média.
Pensei então em diminuir a resolução da imagem digitalizada, mas estou encontrando dificuldade para lidar com essa propriedade.
Alguém pode ajudar? Ou sugerir alguma outra forma de obter imagens menores em MB?
Obrigado.

Código da Class usada.

Imports WIA

Public Class class_cp_Scanner

    Private ReadOnly _deviceInfo As DeviceInfo

    Public Sub New(deviceInfo As DeviceInfo)
        Me._deviceInfo = deviceInfo
    End Sub

    Public Function Scan() As ImageFile
        ' Connect to the device
        Dim device = Me._deviceInfo.Connect()

        'define dialogo para telas de scan (para scan com barra de progresso)
        Dim dialog = New WIA.CommonDialogClass()

        ' Start the scan
        Dim item = device.Items(1)
        'scan sem barra de progresso
        ''''Dim imageFile = DirectCast(item.Transfer(FormatID.wiaFormatJPEG), ImageFile)

        AdjustScannerSettings(item, 300, 0, 0, 1010, 620, 0, 0)

        'scan com barra de progresso
        Dim imageFile = TryCast(dialog.ShowTransfer(item, WIA.FormatID.wiaFormatJPEG), WIA.ImageFile)

        ' Return the imageFile
        Return imageFile
    End Function

    Public Overrides Function ToString() As String
        Return Me._deviceInfo.Properties("Name").Value.ToString '   get_Value().ToString()        
    End Function

    Public Sub SetWIAProperty(properties As IProperties, propName As Object, propValue As Object)
        Dim prop As [Property] = properties.get_Item(propName)
        prop.set_Value(propValue)
    End Sub

    Public Sub AdjustScannerSettings(scannnerItem As IItem, scanResolutionDPI As Integer, scanStartLeftPixel As Integer, scanStartTopPixel As Integer, scanWidthPixels As Integer, scanHeightPixels As Integer, _
    brightnessPercents As Integer, contrastPercents As Integer)
        Const WIA_HORIZONTAL_SCAN_RESOLUTION_DPI As String = "6147"
        Const WIA_VERTICAL_SCAN_RESOLUTION_DPI As String = "6148"
        Const WIA_HORIZONTAL_SCAN_START_PIXEL As String = "6149"
        Const WIA_VERTICAL_SCAN_START_PIXEL As String = "6150"
        Const WIA_HORIZONTAL_SCAN_SIZE_PIXELS As String = "6151"
        Const WIA_VERTICAL_SCAN_SIZE_PIXELS As String = "6152"
        Const WIA_SCAN_BRIGHTNESS_PERCENTS As String = "6154"
        Const WIA_SCAN_CONTRAST_PERCENTS As String = "6155"

        SetWIAProperty(scannnerItem.Properties, WIA_HORIZONTAL_SCAN_RESOLUTION_DPI, scanResolutionDPI)
        SetWIAProperty(scannnerItem.Properties, WIA_VERTICAL_SCAN_RESOLUTION_DPI, scanResolutionDPI)
        SetWIAProperty(scannnerItem.Properties, WIA_HORIZONTAL_SCAN_START_PIXEL, scanStartLeftPixel)
        SetWIAProperty(scannnerItem.Properties, WIA_VERTICAL_SCAN_START_PIXEL, scanStartTopPixel)
        SetWIAProperty(scannnerItem.Properties, WIA_HORIZONTAL_SCAN_SIZE_PIXELS, scanWidthPixels)
        SetWIAProperty(scannnerItem.Properties, WIA_VERTICAL_SCAN_SIZE_PIXELS, scanHeightPixels)
        SetWIAProperty(scannnerItem.Properties, WIA_SCAN_BRIGHTNESS_PERCENTS, brightnessPercents)
        SetWIAProperty(scannnerItem.Properties, WIA_SCAN_CONTRAST_PERCENTS, contrastPercents)
    End Sub

End Class

Erro obtido na linha: AdjustScannerSettings(item, 300, 0, 0, 1010, 620, 0, 0)

An unhandled exception of type 'System.MissingMemberException' occurred in Microsoft.VisualBasic.dll
Additional information: Public member 'get_Item' on type 'PropertiesClass' not found.

Referência: http://www.nakov.com/blog/2009/11/17/playing-with-the-scanner-with-wia-and-c/

Usando: VB.NET 2013