C#生成縮略圖的函數，可直接調用

C#生成縮略圖的函數，可直接調用，代碼非常簡單，直接嵌入你的項目，調用該函數即可。

  /// <summary>
  /// 生成縮略圖
 /// 轉自：http://www.sharejs.com
  /// </summary>
  /// <param name="originalImagePath">源圖路徑（物理路徑）</param>
  /// <param name="thumbnailPath">縮略圖路徑（物理路徑）</param>
  /// <param name="width">縮略圖寬度</param>
  /// <param name="height">縮略圖高度</param>
  /// <param name="mode">生成縮略圖的方式</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"://指定高寬縮放（可能變形）              
          break;
      case "W"://指定寬，高按比例                  
          toheight = originalImage.Height * width/originalImage.Width;
          break;
      case "H"://指定高，寬按比例
          towidth = originalImage.Width * height/originalImage.Height;                  

          break;      
      case "Cut"://指定高寬裁減（不變形）              
          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;
  }  

  //新建一個bmp圖片
  Image bitmap = new System.Drawing.Bitmap(towidth,toheight);

  //新建一個畫板
  Graphics g = System.Drawing.Graphics.FromImage(bitmap);

  //設置高質量插值法
  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

  //設置高質量,低速度呈現平滑程度
  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

  //清空畫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繪制原圖片的指定部分
  g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
      new Rectangle(x, y, ow,oh),
      GraphicsUnit.Pixel);

  try
  {          
      //以jpg格式保存縮略圖
      bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
  }
  catch(System.Exception e)
  {
      throw e;
  }
  finally
  {
      originalImage.Dispose();
      bitmap.Dispose();                      
      g.Dispose();
  }

}</pre>