I am trying to figure out how I can get the original format of an image so that I can store it with the same encoding.

It seems that the only way to save an Image is by using a BitmapEncoder but I don't know how I can get the correct format from the image.

Example:

Clipboard.GetImage() returns a InteropBitmap which doesn't seem to contain any information about the original format.

I also tried using an Extension method:

public static void Save(this BitmapImage image, System.IO.Stream stream)
{
    var decoder = BitmapDecoder.Create(image.StreamSource, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default);
    var encoder = BitmapEncoder.Create(decoder.CodecInfo.ContainerFormat);
    foreach (var frame in decoder.Frames)
    {
        encoder.Frames.Add(BitmapFrame.Create(decoder.Frames[0]));
    }
    encoder.Save(stream);
}

but the problem is that a) the ImageSource is not always a BitmapImage (Clipboard.GetImage()) for example and b) the image.StreamSource can be null in some cases (seems to be when the image is loaded via a relative Uri)