xaml define color based on another color

I am learning WinRT, and i define a custom theme for my program, including overwriting some of the default colors

Currently i do something like this in my App.xaml

<Application>
    <Application.Resource>
        <ResourceDictionary>
            ...
            <Color x:Key="PrimaryColor">#FF0055A3</Color>
            <Color x:Key="PrimaryColorHighlighShade">#FF1263B0</Color>
            <Color x:Key="PrimaryColorClickShade">#FF2674BD</Color>
            ...
            <SolidColorBrush x:Key="SliderTrackDecreaseBackgroundThemeBrush" Color="{StaticResoruce PrimaryColor}" />
            <SolidColorBrush x:Key="SliderTrackDecreasePointerOverBackgroundThemeBrush" Color="{StaticResoruce PrimaryColorHighlighShade}" />
            <SolidColorBrush x:Key="SliderTrackDecreasePressedBackgroundThemeBrush" Color="{StaticResoruce PrimaryColorClickShade}" />
            ...
        </ResourceDictionary>
    </Application.Resource>

To Get the Highlight shade and ClickShade, i open up photoshop, goto the HSB Slider, and move the S Down and the B up, but i was wondering if i could do this in XAML, so that all i had to do what change the PrimaryColor, and the other colors, where adjusted accordingly.

Solution

You can bind to a static resource (see Is it possible to supply a type converter for a static resource in WPF?) and use a value converter to construct a new color based on the color you provide.

Edit:

Here is some code to explain:

The value converter code (for simplicity I always just add red, you can do more complex calculations as you like):

class ColorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value is Color)
        {
            var theColor = Color.Add((Color)value, Color.FromArgb(255,255,0,0));
            return theColor;
        }
        else
        {
            return null;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

My App.Xaml looks like this:

<Application x:Class="SO_15979100.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:local="clr-namespace:SO_15979100"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <Color x:Key="PrimaryColor">#FF0055A3</Color>
        <local:ColorConverter x:Key="MyConverter" />
        <SolidColorBrush x:Key="PrimaryColorBrush" Color="{StaticResource PrimaryColor}" />
        <SolidColorBrush x:Key="ConvertedPrimaryColorBrush" Color="{Binding Source={StaticResource PrimaryColor}, Converter={StaticResource MyConverter}}" />
    </Application.Resources>
</Application>

Note that I've included a local namespace to have the converter at hand.

My main window is defined like this:

<Window x:Class="SO_15979100.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>
    
        <Rectangle Grid.Column="0" Fill="{StaticResource PrimaryColorBrush}" />
        <Rectangle Grid.Column="1" Fill="{StaticResource ConvertedPrimaryColorBrush}" />
    </Grid>
</Window>

The rectangle on the left is your color, the one on the right is pink.