wp8怎样调用当前存入图片库mediaLibrary的图片？c#

我们现在有这样一个刚截取的图片。
c# var fileName = "hello"; WriteableBitmap aaa = new WriteableBitmap(555, 555); aaa.Render(ccc, new MatrixTransform()); aaa.Invalidate(); SaveToMediaLibrary(aaa, fileName, 100);

如果提取文件路径，把pics 代入到path中，应该怎么写？

C# MediaLibrary mediaLibrary = new MediaLibrary(); PictureAlbumCollection albums = mediaLibrary.RootPictureAlbum.Albums; var pics = albums[0].Pictures[albums[0].Pictures.Count - 1].GetImage(); var pic = albums[0].Pictures[albums[0].Pictures.Count - 1].GetThumbnail();

又怎样调取thumbnail的地址呢？
C# byte[] PNG = gogo(pics); byte[] PNGS = gogo(pics); message.ThumbData = PNG; message.ImageData = PNGS;
}

这个byte转化工具是不是很鸡肋？我们一定要提取path么？能够直接调用writeablebitmap中的图片么？
c# private byte[] gogo(string path) { StreamResourceInfo info = App.GetResourceStream(new Uri(path, UriKind.Relative)); if (info == null) return null; Stream stream = info.Stream; byte[] data = new byte[stream.Length]; stream.Read(data, 0, (int)stream.Length); return data; }