Specifying a Viewbox
<Page xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"> <Rectangle> <Rectangle.Fill> <ImageBrush Stretch="UniformToFill" Viewbox="0.75,0.42,0.25,0.34" ImageSource="c:\image.jpg" /> </Rectangle.Fill> </Rectangle> </Page>