获取缩略图

获得缩略图
    bitmap.GetThumbnailImage(
          int thumbWidth,
          int thumbHeight,
          Image.GetThumbnailImageAbort callback,
          IntPtr callbackData
    );
用法：
            static Bitmap myBitmap = new Bitmap(@"Paths");
            public static bool ThumbnailCallback(){ return false;}
            static Image.GetThumbnailImageAbort myCallback = new Image.GetThumbnailImageAbort(ThumbnailCallback);
            Image myThumbnail = myBitmap.GetThumbnailImage(40, 40, myCallback, IntPtr.Zero);