ASP.NET压缩图片

using System.Drawing;

// <summary> 
/**//// 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）　
           if (originalImage.Width > originalImage.Height)
          ...{
              toheight = originalImage.Height * width / originalImage.Width;
          }
          else
          ...{
              towidth = originalImage.Width * height / originalImage.Height;
          }

          if (toheight > height)
          ...{
              int h = toheight;
              toheight = height;
              towidth = towidth * height / h;
          }

          if (towidth > width)
          ...{
              int w = towidth;
              towidth = width;
              toheight = toheight * width / w;
          }　　　　　　　 
           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(); 
   } 
}