使用FileUpload控件上传图片并自动生成缩略图

  /**//// <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>
   /// <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)
   {
   System.Drawing.Image originalImage = System.Drawing.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
   System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
  
   //新建一个画板
   System.Drawing.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(System.Drawing.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 System.Drawing.Rectangle(0, 0, towidth, toheight),
   new System.Drawing.Rectangle(x, y, ow, oh),
   System.Drawing.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();
   }
   }
  
   /**//// <summary>
   /// 在图片上增加文字水印
   /// </summary>
   /// <param name="Path">原服务器图片路径</param>
   /// <param name="Path_sy">生成的带文字水印的图片路径</param>
   protected void AddShuiYinWord(string Path, string Path_sy)
   {
   string addText = "测试水印";
   System.Drawing.Image image = System.Drawing.Image.FromFile(Path);
   System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
   g.DrawImage(image, 0, 0, image.Width, image.Height);
   System.Drawing.Font f = new System.Drawing.Font("Verdana", 16);
   System.Drawing.Brush b = new System.Drawing.SolidBrush(System.Drawing.Color.Blue);
  
   g.DrawString(addText, f, b, 15, 15);
   g.Dispose();
  
   image.Save(Path_sy);
   image.Dispose();
   }
  
   /**//// <summary>
   /// 在图片上生成图片水印
   /// </summary>
   /// <param name="Path">原服务器图片路径</param>
   /// <param name="Path_syp">生成的带图片水印的图片路径</param>
   /// <param name="Path_sypf">水印图片路径</param>
   protected void AddShuiYinPic(string Path, string Path_syp, string Path_sypf)
   {
   System.Drawing.Image image = System.Drawing.Image.FromFile(Path);
   System.Drawing.Image copyImage = System.Drawing.Image.FromFile(Path_sypf);
   System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(image);
   g.DrawImage(copyImage, new System.Drawing.Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width,copyImage.Height, System.Drawing.GraphicsUnit.Pixel);
   g.Dispose();
  
   image.Save(Path_syp);
   image.Dispose();
   }
  }
  http://blog.csdn.net/mengyao/archive/2007/02/19/1511774.aspx

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