asp.net生成高清晰缩略图

 /// <summary> 
        /// 生成缩略图 
        /// </summary> 
        /// <param name="originalImagePath">源图路径（物理路径）</param> 
        /// <param name="thumbnailPath">缩略图路径（物理路径）</param> 
        /// <param name="width">缩略图宽度</param> 
        /// <param name="height">缩略图高度</param>   
        public  void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height) 
        { 
          System.Drawing.Image   originalImage = System.Drawing.Image.FromFile(originalImagePath); 

           int towidth = 0; 
           int toheight =0; 
            if(originalImage.Width>width &&originalImage.Height<height) 
            { 
                towidth = width; 
                toheight = originalImage.Height; 
            } 

            if (originalImage.Width<width && originalImage.Height >height) 
            { 
                towidth = originalImage.Width; 
                toheight = height; 
            } 
            if (originalImage.Width > width && originalImage.Height > height) 
            { 
                towidth = width; 
                toheight = height; 
            } 
            if (originalImage.Width < width && originalImage.Height < height) 
            { 
                towidth = originalImage.Width; 
                toheight = originalImage.Height; 
            } 
            int x = 0;//左上角的x坐标 
            int y = 0;//左上角的y坐标 
            

            //新建一个bmp图片 
         System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight); 

            //新建一个画板 
            Graphics g = System.Drawing.Graphics.FromImage(bitmap); 

            //设置高质量插值法 
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; 

            //设置高质量,低速度呈现平滑程度 
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; 

            //清空画布并以透明背景色填充 
            g.Clear(Color.Transparent); 

            //在指定位置并且按指定大小绘制原图片的指定部分 
            g.DrawImage(originalImage,x,y,towidth,toheight); 

            try 
            { 
                //以jpg格式保存缩略图 
                bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); 
            } 
            catch (System.Exception e) 
            { 
                throw e; 
            } 
            finally 
            { 
                originalImage.Dispose(); 
                bitmap.Dispose(); 
                g.Dispose(); 
            } 
        }