[Amin_Mansouri]

کد:

Imports System.Drawing
Imports System.Drawing.Drawing2D

Dim gu As New Guid
gu = Guid.NewGuid
Dim ext As String = Path.GetExtension(FileUpload1.FileName)
ImageName = gu.ToString & ext
FileUpload1.SaveAs(Server.MapPath("~/DynamicImages/News/" & ImageName))
Using fl = File.OpenRead(Server.MapPath("~/DynamicImages/News/" & ImageName))
    Using thumbFile = File.Create(Server.MapPath("~/DynamicImages/News/thumbnails/" & ImageName))
        ResizeImage(0.1, fl, thumbFile)
    End Using
End Using

Private Sub ResizeImage(ByVal scaleFactor As Double, ByVal fromStream As Stream, ByVal toStream As Stream)
    Using image__1 = Image.FromStream(fromStream)
        'Dim newWidth = CInt(image__1.Width * scaleFactor)
        ' Dim newHeight = CInt(image__1.Height * scaleFactor)
        Dim newWidth = 150
        Dim newHeight = 150

        Using thumbnailBitmap = New Bitmap(newWidth, newHeight)
            Using thumbnailGraph = Graphics.FromImage(thumbnailBitmap)
                thumbnailGraph.CompositingQuality = CompositingQuality.HighQuality
                thumbnailGraph.SmoothingMode = SmoothingMode.HighQuality
                thumbnailGraph.InterpolationMode = InterpolationMode.HighQualityBicubic

                Dim imageRectangle = New Rectangle(0, 0, newWidth, newHeight)
                thumbnailGraph.DrawImage(image__1, imageRectangle)

                thumbnailBitmap.Save(toStream, image__1.RawFormat)
            End Using
        End Using
    End Using
End Sub

اینم ببین
http://www.nerdymusings.com/LPMArticle.asp?ID=32
بهتر از این لینک بالا فکر نکنم بتونم بهت بگم