asp.net创建缩略图

记录一个保存缩略图通用的函数。

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  /// <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) 
  { 
      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(); 
      } 
  }