上一篇"base64编码在silverlight中的使用"里已经提到WriteableBitmap对象可以借助FluxJpeg转化为base64字符串，而WriteableBitmap又能从BitmapSource直接构造，so ... 问题解决了
先将BitmapImage转化为WriteableBitmap，然后得到base64字符串，然后可以得到base64的byte[]数组，再然后您可以把byte[]变成Stream
关键代码：
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3 WriteableBitmap wb = new WriteableBitmap(img.Source as BitmapSource);//将Image对象转换为WriteableBitmap
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5 byte[] b = Convert.FromBase64String(GetBase64Image(wb));//得到byte数组
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3 WriteableBitmap wb = new WriteableBitmap(img.Source as BitmapSource);//将Image对象转换为WriteableBitmap
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5 byte[] b = Convert.FromBase64String(GetBase64Image(wb));//得到byte数组
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将byte[]还原为图片:
1 byte[] b = ...//这里的b为上面生成的base64编码的byte数组
2 MemoryStream ms = new MemoryStream(b);
3 BitmapImage bitImage = new BitmapImage();
4 bitImage.SetSource(ms);
5 img2.Source = bitImage;
2 MemoryStream ms = new MemoryStream(b);
3 BitmapImage bitImage = new BitmapImage();
4 bitImage.SetSource(ms);
5 img2.Source = bitImage;