Question

Assume 2 images, a big one for Background and an smaller one for Foreground. The foreground stays exactly at the middle of the background, covering a relative amount of it (e.g. 50%) so the User sees them as a single image.

The problem is that I need the Background to fill the Window in various sizes. Setting its Stretch value to UniformToFill will do that. But how can I keep the foreground still covering 50% of the background?

Answer 1

It would be better to use a Vector Image, because it can scale ‘itself’ when you resize its container.

Then you set margin based on the window size as below:

<Window x:Class="MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    Height="400" Width="400">
<Grid>
    <Image Margin="100">
        <Image.Source>
            <DrawingImage>
                <DrawingImage.Drawing>
                    <GeometryDrawing Brush="#FF000000" Geometry="M14.800615,5.6499605L14.800615,14.800346C10.630442,17.910477 7.8903284,22.840685 7.8903284,28.44092 7.9003286,37.871319 15.530646,45.511639 24.961039,45.521641 34.391431,45.511639 42.011749,37.871319 42.04175,28.44092 42.03175,22.840685 39.291636,17.910477 35.121462,14.800346L35.121462,5.6599612C43.841825,9.5601254,49.912077,18.280493,49.912077,28.44092L49.922077,28.44092C49.912077,42.231503 38.741611,53.391972 24.961039,53.391972 11.170465,53.391972 0,42.231503 0,28.44092 0,18.270493 6.0902529,9.5501251 14.800615,5.6499605z M19.570043,0L30.237043,0 30.237043,33.917 19.570043,33.917z" />
                </DrawingImage.Drawing>
            </DrawingImage>
        </Image.Source>
    </Image>
</Grid>

To always use 50% of the window, you can use a Converter to bind the properties.

Also, maybe this can help you.