''' <summary>Komprimnieren der Bild-Daten</summary>
    ''' <param name="file">Pfad der Bilddatei</param>
    ''' <param name="Picsize">Größe des Bildes im Speicher</param>
    '''<param name="PicQuality">Qualität des kompr. Bildes (50-95)</param> 
    ''' <returns>Komprimierte Bilddaten (Byte-Array) oder Nothing</returns>
    Public Function GetJPGBytesFromFile(ByVal file As String, ByVal Picsize As _
      Size, _
                                ByVal PicQuality As Integer) As Byte()
        Dim pt, pl, pw, ph As Integer
 
        'Für JPEG-Komptimierung
        Dim EncoderInfo As Imaging.ImageCodecInfo = GetEncoderInfo("JPEG")
        Dim EncoderParameters As New Imaging.EncoderParameters(1)
        EncoderParameters.Param(0) = New  _
        Imaging.EncoderParameter(Imaging.Encoder.Quality, CType(PicQuality,  _
        System.Int32))
 
        Try
            Using bmp As New Bitmap(file), _
                ibmp As New Bitmap(Picsize.Width, Picsize.Height, _
                                   Imaging.PixelFormat.Format24bppRgb), _
                gr As Graphics = Graphics.FromImage(ibmp), _
                ms As New IO.MemoryStream
 
                'Bildgröße in Fläche einpassen und Bild zentrieren
                pt = 0 : pl = 0 : pw = bmp.Width : ph = bmp.Height
                If pw > Picsize.Width Then
                    pw = Picsize.Width : ph = CInt(bmp.Height * pw / bmp.Width)
                    pt = (Picsize.Height - ph) \ 2
                End If
                If ph > Picsize.Height Then
                    ph = Picsize.Height : pw = CInt(bmp.Width * ph / bmp.Height)
                    pl = (Picsize.Width - pw) \ 2 : pt = 0
                End If
 
                'Bild in neuer Größe zeichnen
                Dim srcrect As New Rectangle(0, 0, bmp.Width, bmp.Height)
                Dim destrect As New Rectangle(pl, pt, pw, ph)
                gr.Clear(Color.White)
                gr.DrawImage(bmp, destrect, srcrect, GraphicsUnit.Pixel)
 
                'Bilddaten JPEG-komprimieren und in den Speicher-Stream 
                ' schreiben
                ibmp.Save(ms, EncoderInfo, EncoderParameters)
 
                'Komprimierte Bilddaten als Bytefolge zurückgeben
                Dim jpg_bytes As Byte() = ms.GetBuffer()
                Return jpg_bytes
            End Using
        Catch ex As System.Exception
            Return Nothing
        End Try
    End Function
 
    Public Function GetBitmapFromJPGBytes(ByVal JPGBytes() As Byte) As Bitmap
        Using ms As New IO.MemoryStream
            'Bilddaten (JPEG) in den Speicherstream übertragen
            ms.Write(JPGBytes, 0, JPGBytes.Length)
            'Bilddaten dekomprimieren (per Bitmap-Objekt)
            Return CType(Bitmap.FromStream(ms), Bitmap)
        End Using
    End Function
 
    ''' <summary>Hilfsfunktion ermittelt den GDI+-Encoder zu einem 
    ' Bildformat-Descriptor</summary>
    Private Function GetEncoderInfo( _
      ByVal FormatDescriptor As String) As Imaging.ImageCodecInfo
        Dim i As Integer = 0
        Dim encoders() As Imaging.ImageCodecInfo = _
          Imaging.ImageCodecInfo.GetImageEncoders()
        FormatDescriptor = FormatDescriptor.ToUpper.Trim
        While i < encoders.Length
            If encoders(i).FormatDescription.ToUpper = FormatDescriptor Then
                Return encoders(i)
            End If
            i += 1
        End While
        Return Nothing
    End Function