下面这段代码实现的功能是在asp.net中生成高清晰的缩略图，提供源图路径、缩略图路径、宽度、高度这四个参数就完成了此项的功能。详细代码如下：

        /// <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();
            }
        }