C#生成缩略图的函数，可直接调用，代码非常简单，直接嵌入你的项目，调用该函数即可。

  /// <summary>    /// 生成缩略图   /// 转自：http://www.sharejs.com    /// </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>    /// <param name="mode">生成缩略图的方式</param>      public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)    {        Image originalImage = Image.FromFile(originalImagePath);                  int towidth = width;        int toheight = height;              int x = 0;        int y = 0;        int ow = originalImage.Width;        int oh = originalImage.Height;                  switch (mode)        {                  case "HW"://指定高宽缩放（可能变形）                              break;            case "W"://指定宽，高按比例                                  toheight = originalImage.Height * width/originalImage.Width;                break;            case "H"://指定高，宽按比例                towidth = originalImage.Width * height/originalImage.Height;                                     break;                  case "Cut"://指定高宽裁减（不变形）                              if((double)originalImage.Width/(double)originalImage.Height > (double)towidth/(double)toheight)                {                    oh = originalImage.Height;                    ow = originalImage.Height*towidth/toheight;                    y = 0;                    x = (originalImage.Width - ow)/2;                }                else                {                    ow = originalImage.Width;                    oh = originalImage.Width*height/towidth;                    x = 0;                    y = (originalImage.Height - oh)/2;                }                break;                              default :                break;        }                    //新建一个bmp图片        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, new Rectangle(0, 0, towidth, toheight),            new Rectangle(x, y, ow,oh),            GraphicsUnit.Pixel);            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();        }    }