ho risolto:

codice:
<html>
<head>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<%@ Page Language="VB" Debug="true" %>
<script language="VB" runat=server>

  Function NewthumbSize(currentwidth, currentheight)
    ' Calculate the Size of the New image
    dim x,y,h,w as Double
    x=currentwidth
    y=currentheight
    'h=Request.QueryString("h")
    'w=Request.QueryString("w")
    h=120
    w=120
    if (x>y) then
      x=w
      y=(w*y)/x
    else
      x=(h*x)/y
      y=h
    end if
    dim NewSize as New Size(x, y)
    return NewSize
  End Function

  Sub Page_Load(Sender As Object, E As EventArgs)
    dim objBMP as System.Drawing.Bitmap
    dim objGraph as System.Drawing.Image
    objBMP = New Bitmap(
      "C:\Programmi\Apache Group\Apache\htdocs\image.JPG")
    dim thumbSize as New size
    thumbSize = NewthumbSize(objBMP.width,objBMP.height)
    objGraph = objBMP.GetThumbnailImage(thumbsize.width,
      thumbsize.height, Nothing, IntPtr.Zero)
    objGraph.Save(Server.MapPath("image_t.JPG"),
      ImageFormat.JPEG)
  End Sub

</script>
</head>
<body Runat="server">
<asp:Image ID="objGraph" Src="image_t.JPG" Runat="server" />
</body>
</html>
ora mi stavo chiedendo come potevo utilizzare questo script richiamandolo più volte inviandogli come parametri larghezza e altezza dell'anteprima nome file d'origine e nome file destinato all'anteprima (forse con un form e quattro parametri passati col get?)