Dim myImage As Image = ' ... load the image somehow
 ' Save the image with a quality of 50% 
SaveJpeg(destImagePath, myImage, 50)

'add this!
Imports System.Drawing.Imaging      
' Saves an image as a jpeg image, with the given quality     
' Gets:    
'   path   - Path to which the image would be saved.    
'   quality - An integer from 0 to 100, with 100 being the     
'           highest quality    
         Public Shared Sub SaveJpeg(ByVal path As String, ByVal img As Image, ByVal quality As Long)        
         If ((quality < 0) OrElse (quality > 100)) Then            
                  Throw New ArgumentOutOfRangeException("quality must be between 0 and 100.")        
         End If         
         ' Encoder parameter for image quality        
         Dim qualityParam As New EncoderParameter(Encoder.Quality, quality)        
         ' Jpeg image codec
         Dim jpegCodec As ImageCodecInfo = GetEncoderInfo("image/jpeg")

         Dim encoderParams As New EncoderParameters(1)
        encoderParams.Param(0) = qualityParam
        img.Save(path, jpegCodec, encoderParams)
    End Sub
       ' Returns the image codec with the given mime type
     Private Shared Function GetEncoderInfo(ByVal mimeType As String) As ImageCodecInfo
        ' Get image codecs for all image formats
         Dim codecs As ImageCodecInfo() = ImageCodecInfo.GetImageEncoders()
         ' Find the correct image codec
         For i As Integer = 0 To codecs.Length - 1
            If (codecs(i).MimeType = mimeType) Then
                Return codecs(i)
            End If
        Next i
         Return Nothing
    End Function