<Window x:Class="WPFBrushes.ColorAndAlpha"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Alpha Channel" Height="300" Width="300">
<Grid VerticalAlignment="Center" HorizontalAlignment="Center">
<Rectangle Height="200" Width="200">
<Rectangle.Fill>
<DrawingBrush Viewport="0,0,10,10" ViewportUnits="Absolute" TileMode="Tile">
<DrawingBrush.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="Black">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="0,0,10,10" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing Brush="Red" Geometry="M0,10 L 0,0 10,0 10,1 1,1 1,10Z">
</GeometryDrawing>
</DrawingGroup>
</DrawingBrush.Drawing>
</DrawingBrush>
</Rectangle.Fill>
</Rectangle>
</Grid>
</Window>