public class GetBitmapImageClass
 {
  public BitmapSource GetImageHttp(string url,int width)
  {
   var image = new BitmapImage();
   int BytesToRead = 100;
   if (!string.IsNullOrEmpty(url))
   {
    WebRequest request = WebRequest.Create(new Uri(url, UriKind.Absolute));
    request.Timeout = -1;
    WebResponse response = request.GetResponse();
    Stream responseStream = response.GetResponseStream();
    BinaryReader reader = new BinaryReader(responseStream);
    MemoryStream memoryStream = new MemoryStream();

    byte[] bytebuffer = new byte[BytesToRead];
    int bytesRead = reader.Read(bytebuffer, 0, BytesToRead);

    while (bytesRead > 0)
    {
     memoryStream.Write(bytebuffer, 0, bytesRead);
     bytesRead = reader.Read(bytebuffer, 0, BytesToRead);
    }

    image.BeginInit();
    image.DecodePixelWidth = width;
    image.CacheOption = BitmapCacheOption.OnLoad;
    memoryStream.Seek(0, SeekOrigin.Begin);

    image.StreamSource = memoryStream;
    image.EndInit();
    image.Freeze();
    memoryStream.Close();
    reader.Close();
    responseStream.Close();
    response.Close();
   }
   return image;
  }

  public BitmapSource GetImageFtp(string url, int width)
  {
   var image = new BitmapImage();
   if (!string.IsNullOrEmpty(url))
   {
    FtpWebRequest reqFtp;
    reqFtp = (FtpWebRequest)FtpWebRequest.Create(new Uri(url));

    reqFtp.Method = WebRequestMethods.Ftp.DownloadFile;
    reqFtp.UseBinary = true;
    FtpWebResponse response = (FtpWebResponse)reqFtp.GetResponse();
    Stream ftpStream = response.GetResponseStream();
    MemoryStream mStream = new MemoryStream();
    ftpStream.CopyTo(mStream);
    mStream.Position = 0;
    int length = (int)mStream.Length;
    byte[] returnbyte = new byte[length];
    mStream.Read(returnbyte, 0, length);

    mStream.Close();
    ftpStream.Close();
    response.Close();

    System.IO.MemoryStream stream = new System.IO.MemoryStream(returnbyte);
    image.BeginInit();
    image.DecodePixelWidth = width;
    image.CacheOption = BitmapCacheOption.OnLoad;
    stream.Seek(0, SeekOrigin.Begin);

    image.StreamSource = stream;
    image.EndInit();
    image.Freeze();
    stream.Close();
   }
   return image;

  }


  [DllImport("gdi32.dll", SetLastError = true)]
  private static extern bool DeleteObject(IntPtr hObject);

  public BitmapSource ToBitmapSource(System.Drawing.Bitmap bmp)
  {
   try
   {
    var ptr = bmp.GetHbitmap();
    var source = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(
     ptr, IntPtr.Zero, Int32Rect.Empty, System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions());
    DeleteObject(ptr);
    return source;
   }
   catch
   {
    return null;
   }
  }

  //获取缩略图
  public BitmapSource GetBitImage(string imageLink)
  {
   //"http://172.17.1.231:8083/3050273262379466760/2017/05/28/09/340800100999/09163448402.jpg?fid=1267520"
   if (imageLink.StartsWith("http://"))
   {
    return GetImageHttp(imageLink,200);
   }
   //ftp格式的
   else if (imageLink.StartsWith("ftp://"))
   {
    return GetImageFtp(imageLink, 200);
   }
  }

  //获取原图
  public BitmapSource GetHightBitImage(string imageLink)
  {
   //"http://172.17.1.231:8083/3050273262379466760/2017/05/28/09/340800100999/09163448402.jpg?fid=1267520"
   if (imageLink.StartsWith("http://"))
   {
    return GetImageHttp(imageLink, 0);
   }
   //ftp格式的
   else if (imageLink.StartsWith("ftp://"))
   {
    return GetImageFtp(imageLink, 0);
   }
  }

 }