[Silverlight] How to watermark a WriteableBitmap with a text

Hello,
In my current project, I needed to watermark a WriteableBitmap with a text. As I couldn't find anything I decided to create a small extension method to do so.
public static class WriteableBitmapEx{ /// <summary> /// Creates a watermark on the specified image /// </summary> /// <param name="input">The image to create the watermark from</param> /// <param name="watermark">The text to watermark</param> /// <param name="color">The color - default is White</param> /// <param name="fontSize">The font size - default is 50</param> /// <param name="opacity">The opacity - default is 0.25</param> /// <param name="hasDropShadow">Specifies if a drop shadow effect must be added - default is true</param> /// <returns>The watermarked image</returns> public static WriteableBitmap Watermark(this WriteableBitmap input, string w ...