Custom Coordinates by transforming the Canvas
<Window x:Class="LineInCustomSystem" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Line In Custom System" Height="240" Width="220"> <Border BorderBrush="Black" BorderThickness="1" Height="200" Width="200"> <Canvas Height="200" Width="200"> <Canvas.RenderTransform> <TransformGroup> <ScaleTransform ScaleY="-1" /> <TranslateTransform Y="200" /> </TransformGroup> </Canvas.RenderTransform> <Line X1="0" Y1="0" X2="100" Y2="100" Stroke="Black" StrokeThickness="2" /> </Canvas> </Border> </Window>