[c#] interpolazione immagine

[Istrich]

Salve a tutti
sono alle prime armi con asp.net...
Il mio problema è che non riesco a utilizzare i parametri di interpolazione per le immagini, cambio le impostazioni di "InterpolationMode" e di tutti i parametri che riguardano la qualità dell'immagine ma il risultato non cambia cioè i bordi di alcuni tratti appaiono seghettati, mentre la compressione ed il ridimensionamento funzionano..
ecco il codice:

<%@ Page Language="C#" ContentType="text/html" ResponseEncoding="iso-8859-1"%>
<%@ import Namespace="System.IO" %>
<%@ import Namespace="System.Drawing" %>
<%@ import Namespace="System.Drawing.Imaging" %>
<%@ import Namespace="System.Drawing.Drawing2D" %>
<script language="C#" runat="server">

void Page_Load(Object sender, EventArgs e) {
        
        
        string imageLocation;
        bool forceaspect = true;
        int newHeight;
        int newWidth;
        int reqHeight = 100;
        int reqWidth = 100;
        int origHeight;
        int origWidth;
        imageLocation = Request.QueryString["Image"];
        if (Request.QueryString["Height"] != null){
            reqHeight = Convert.ToInt32(Request.QueryString["Height"]);
        }
        if (Request.QueryString["ForceAspect"] != null){
            forceaspect = Convert.ToBoolean(Request.QueryString["ForceAspect"]);
        }
        if(Request.QueryString["Width"] != null){
            reqWidth = Convert.ToInt32(Request.QueryString["Width"]);
        }
        if (Request.QueryString["ForceAspect"] == "true"){
            forceaspect = true;
        }
        System.Drawing.Bitmap origBitmap = new System.Drawing.Bitmap(Server.MapPath(imageLocation));
        origHeight = origBitmap.Height;
        origWidth = origBitmap.Width;
        
        if (forceaspect){
            //Force Aspect Change
            newHeight = reqHeight;
            newWidth = reqWidth;
        }        
        else if (origBitmap.Width >= origBitmap.Height){
            //Portrait
            newWidth = reqWidth;
            newHeight = (int)(((double)origBitmap.Height / (double)origBitmap.Width) * reqWidth);
        }
        else{ 
            //Landscape
            newWidth = reqWidth;
            newHeight = (int)(((double)origBitmap.Height / (double)origBitmap.Width) * reqWidth);
        }
        origBitmap.Dispose();

    ResizeFile(imageLocation, newWidth, newHeight, "", 95);
}


private void Resize(Stream imgStr, int width, int height, string FileName, int compression) {

    //creo il bitmap dallo stream
    System.Drawing.Image bmpStream=System.Drawing.Image.FromStream(imgStr);
        


    //creo un nuovo bitmap
    Bitmap img;
    

    Graphics oGraphic = Graphics.FromImage(bmpStream);

    oGraphic.CompositingQuality = CompositingQuality.HighQuality;
    //oGraphic.SmoothingMode = SmoothingMode.HighQuality;
    oGraphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
    oGraphic.PixelOffsetMode = PixelOffsetMode.HighQuality; 
    oGraphic.SmoothingMode = SmoothingMode.AntiAlias;
    
    //se indicato lo ridimensiono
    if (width == 0 || height == 0) img=new Bitmap(bmpStream);
    else img=new Bitmap(bmpStream,new Size(width,height));
    

        
    ImageCodecInfo jpegCodecInfo;
    System.Drawing.Imaging.Encoder encoder;
    EncoderParameter encoderParameter;
    EncoderParameters encoderParameters;
    jpegCodecInfo = GetEncoderInfo("image/jpeg");
    encoder = System.Drawing.Imaging.Encoder.Quality;
    encoderParameters = new EncoderParameters(1);
    encoderParameter = new EncoderParameter(encoder, compression);
    encoderParameters.Param[0] = encoderParameter;
    
    if (FileName == "") {
        img.Save(FileName, jpegCodecInfo, encoderParameters);
    } else {
        Response.ContentType = "image/jpeg";
        img.Save(Response.OutputStream, jpegCodecInfo, encoderParameters);
    }
    img.Dispose();
    img = null;

}

private void ResizeFile(string nomefile,int width, int height, string nuovonome, int compression) {

    //carico un'immagine in uno stream
    try {
        FileStream file=new FileStream(Server.MapPath(nomefile),FileMode.Open);
        Resize(file,width,height,Server.MapPath(nuovonome),compression);
        file.Close();
    } catch (System.IO.FileNotFoundException ex) {
        Response.Write("l'immagine non esiste");
    }

}

ImageCodecInfo GetEncoderInfo(string mimeType) {
   ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders();
   for (int j = 0; j< encoders.Length; j++) {
      if (encoders[j].MimeType == mimeType) {
           return encoders[j];
      }
   }
   return null;
}
</script>