asp.net生成的缩略图不够清晰，望高手解决... 

public static bool CreateMiniPic(string url, string newPath, int width)
        {
            double w = 0.0;
            double h = 0.0;
            bool result = false;
            System.Drawing.Image image = null;
            System.Drawing.Graphics g = null;
            string newMapPath = System.Web.HttpContext.Current.Server.MapPath(newPath);
            try
            {
                //从文件取得图片对象 
                System.Net.WebRequest rq = System.Net.WebRequest.Create(url);
                rq.Timeout = 10000;
                System.Net.HttpWebResponse rs = (System.Net.HttpWebResponse)rq.GetResponse();
                Stream st = rs.GetResponseStream();

                image = System.Drawing.Image.FromStream(st);
                w = Convert.ToDouble(width);
                h = (w * Convert.ToDouble(image.Height)) / Convert.ToDouble(image.Width);

                //取得图片大小 
                System.Drawing.Size size = new System.Drawing.Size(Convert.ToInt32(w), Convert.ToInt32(h));
                //新建一个bmp图片 
                System.Drawing.Image bmp = new System.Drawing.Bitmap(size.Width, size.Height);
                //新建一个画板 
                g = System.Drawing.Graphics.FromImage(bmp);
                //设置高质量插值法 
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                //设置高质量,低速度呈现平滑程度 
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                //清空一下画布 
                g.Clear(System.Drawing.Color.Transparent);
                //在指定位置画图 
                g.DrawImage(image, new System.Drawing.Rectangle(0, 0, bmp.Width, bmp.Height),
                new System.Drawing.Rectangle(0, 0, image.Width, image.Height),
                System.Drawing.GraphicsUnit.Pixel);
                //保存高清晰度的缩略图 
                bmp.Save(newMapPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                result = true;
            }
            catch
            {
                result = false;
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }

            return result;
        }