/// 生成缩略图       /// </summary>       /// <param name="originalImagePath">源图路径</param>       /// <param name="thumbnailPath">缩略图路径</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:HW指定高宽缩放(可能变形);W指定宽，高按比例 H指定高，宽按比例 Cut指定高宽裁减(不变形)</param>　　       /// <param name="mode">要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为jpg</param>　　       public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType)      {          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               switch (imageType.ToLower())              {                  case "gif":                      bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);                      break;                  case "jpg":                      bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);                      break;                  case "bmp":                      bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);                      break;                  case "png":                      bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);                      break;                  default:                      bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);                      break;              }          }          catch (System.Exception e)          {              throw e;          }          finally          {              originalImage.Dispose();              bitmap.Dispose();              g.Dispose();          }      }