What is to FromFile and ToFile equivalent for BitmapImage?

The System.Drawing.Image has the easy to use methods for FromFile and ToFile. What is the equivalent for the Silverlight BitmapImage? I am trying to load an开发者_开发技巧d save a jpeg image as part of a unit test. The bytes must match exactly for it to pass. Here is my current guess:

    //I am not sure this is right
    private BitmapImage GetImage(string fileName)
    {
        BitmapImage bitmapImage = new System.Windows.Media.Imaging.BitmapImage();
        using (Stream imageStreamSource = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read))
        {
            bitmapImage.BeginInit();
            bitmapImage.StreamSource = imageStreamSource;
            bitmapImage.EndInit();
        }

        return bitmapImage;
    }

    private void SaveImage(BitmapImage bitmapImage, string file)
    {
        //How to do this?
    }

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An in-browser Silverlight application cannot open a file using a filename. You would need it run out-of-browser with elevated trust to do that.

Silverlight has no built-in image encoding so you can't take the contents of a bitmap (BTW you would need to be using WriteableBitmap to be able to access the raw image).

You find something you need in Image Tools.

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From MSDN link, use the ctor overload which takes in a URI or

BitmapImage myBitmapImage = new BitmapImage();

// BitmapImage.UriSource must be in a BeginInit/EndInit block
myBitmapImage.BeginInit();
myBitmapImage.UriSource = new Uri(@"C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Water Lilies.jpg");
myBitmapImage.DecodePixelWidth = 200;
myBitmapImage.EndInit();

//set image source
myImage.Source = myBitmapImage;

To save the image to disk, you'd need the specific encoder e.g. JpegBitmapEncoder