How can I convert the values of three sliders into

Question

I'm trying to create a custom user control that will allow a user to define a color in WPF. I've done this before in WinForms but in WPF it seems to be not as straight forward. This is also my first time dealing with a multi-converter.

The control has 3 Sliders - like so :

<Slider x:Name="sdrRed" Height="32" LargeChange="5" SmallChange="1" Maximum="255" Width="321" TickPlacement="Both"/>

The only difference is the name for each - sdrRed, sdrGreen, and sdrBlue.

This is the multi-value converter :

public class ByteToColorConverter : IMultiValueConverter 
{
    public object Convert( object[ ] values, Type targetType, object parameter, System.Globalization.CultureInfo culture ) {
        return Color.FromArgb( (byte)values[0], (byte)values[1], (byte)values[2], (byte)values[3]);
    }

    public object[ ] ConvertBack( object value, Type[ ] targetTypes, object parameter, System.Globalization.CultureInfo culture ) {
        Color C = ( Color )value;
        return new object[ ] { C.A, C.R, C.G, C.B };
    }
}

This is as far as I have been able to get - I haven't been able to find an example of how to proceed.

Also - how can I pass values to the multiconverter that are static, so that I may define a color with only a single slider (say, so that I may define shades of Red, Blue or Green)?

EDIT

For some clarity; The control itself will have a dependency property :

private static readonly DependencyProperty
    _Color = DependencyProperty.Register( "Color", typeof( Color ), typeof( ColorDefiner ), new PropertyMetadata( Colors.Black ) );

public Color Color {
    get { return ( Color )this.GetValue( ColorDefiner._Color ); }
    set { this.SetValue( ColorDefiner._Color, value ); }
}

This control will pass the converted Color value to that binding, so that other colors may be bound to it. I hope that clears things up.

Answer 1

Okay - I want to thank everyone for their help; I was finally able to come up with a solution - in the event anyone is interested or stumbles upon this, it's also a good lesson in MVVM (maybe; I don't know...).

Anyway :

This is the MVVM I implemented :

public class ColorViewModel : INotifyPropertyChanged {

    public event PropertyChangedEventHandler PropertyChanged;

    private Color _Color = Colors.Black;

    public double A {
        get { return this.Color.ScA; }
        set {
            this._Color.ScA = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "A" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }
    public double R {
        get { return this.Color.ScR; }
        set {
            this._Color.ScR = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "R" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Red" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }
    public double G {
        get { return this.Color.ScG; }
        set {
            this._Color.ScG = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "G" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Green" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }
    public double B {
        get { return this._Color.ScB; }
        set {
            this._Color.ScB = ( float )value;
            if ( this.PropertyChanged != null ) {
                this.PropertyChanged( this, new PropertyChangedEventArgs( "B" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Blue" ) );
                this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
            }
        }
    }

    public Color Color {
        get { return this._Color; }
        set {
            this._Color = value;
            if ( this.PropertyChanged != null )
                this.AllChanged( );
        }
    }
    public Color Red { get { return Color.FromScRgb( 1.0F, ( float )this.R, 0.0F, 0.0F ); } }
    public Color Green { get { return Color.FromScRgb( 1.0F, 0.0F, ( float )this.G, 0.0F ); } }
    public Color Blue { get { return Color.FromScRgb( 1.0F, 0.0F, 0.0F, ( float )this.B ); } }

    private void AllChanged( ) {
        this.PropertyChanged( this, new PropertyChangedEventArgs( "A" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "R" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "G" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "B" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Red" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Green" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Blue" ) );
        this.PropertyChanged( this, new PropertyChangedEventArgs( "Color" ) );
    }
}

This is the control class :

public partial class ColorDefiner : UserControl {

    public static readonly DependencyProperty
        _Color = DependencyProperty.Register( "Color", typeof( Color ), typeof( ColorDefiner ) );

    public Color Color {
        get { return ( Color )this.GetValue( ColorDefiner._Color ); }
        set { this.SetValue( ColorDefiner._Color, value ); }
    }

    private ColorViewModel CVM { get { return this.DataContext as ColorViewModel; } }

    public ColorDefiner( ) {
        InitializeComponent( );
        Binding B = new Binding( "Color" ) { Source = this.DataContext };
        this.SetBinding( ColorDefiner._Color, B );
    }
}

This is the XAML for the User Control (yes, I did it with a UserControl; this required a data context, and I really don't want to fuss with that yet in a Custom Control - this is really only going to be my own personal control for my own use anyway) :

<UserControl
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
    xmlns:Components="clr-namespace:WPFTools.Components"
    xmlns:Controls="clr-namespace:WPFTools.Controls"
    x:Class="WPFTools.Controls.ColorDefiner"
    mc:Ignorable="d"
    Width="100" Height="100" FontFamily="Arial" FontWeight="Bold">
    <UserControl.DataContext>
        <Controls:ColorViewModel/>
    </UserControl.DataContext>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="20"/>
            <RowDefinition Height="5"/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Viewbox HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
            <Components:WPFGLabel Text="A" StrokeThickness="0.5" TextAlignment="Right" Stroke="#99000000">
                <Components:WPFGLabel.Fill>
                    <SolidColorBrush Color="{Binding Color}"/>
                </Components:WPFGLabel.Fill>
            </Components:WPFGLabel>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Column="1">
            <Components:WPFGLabel Text="R" StrokeThickness="0.5" TextAlignment="Right" Stroke="#99000000">
                <Components:WPFGLabel.Fill>
                    <SolidColorBrush Color="{Binding Red, Mode=OneWay}"/>
                </Components:WPFGLabel.Fill>
            </Components:WPFGLabel>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Column="2">
            <Components:WPFGLabel Text="G" StrokeThickness="0.5" TextAlignment="Right" Stroke="#99000000">
                <Components:WPFGLabel.Fill>
                    <SolidColorBrush Color="{Binding Green, Mode=OneWay}"/>
                </Components:WPFGLabel.Fill>
            </Components:WPFGLabel>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Grid.Column="3">
            <Components:WPFGLabel Text="B" StrokeThickness="0.5" TextAlignment="Right" Stroke="#99000000" RenderTransformOrigin="-7.272,0.575">
                <Components:WPFGLabel.Fill>
                    <SolidColorBrush Color="{Binding Blue, Mode=OneWay}"/>
                </Components:WPFGLabel.Fill>
            </Components:WPFGLabel>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" Grid.Row="2" VerticalAlignment="Stretch">
            <Slider Orientation="Vertical" TickPlacement="Both" LargeChange="0.1" Maximum="1" SmallChange="0.01" TickFrequency="0.02" Height="90" TabIndex="0" Value="{Binding A, Mode=TwoWay}"/>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" Grid.Row="2" Grid.Column="1"  VerticalAlignment="Stretch">
            <Slider Orientation="Vertical" TickPlacement="Both" LargeChange="0.1" Maximum="1" SmallChange="0.01" TickFrequency="0.02" Height="90" TabIndex="1" Value="{Binding R, Mode=TwoWay}"/>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" Grid.Row="2" Grid.Column="2"  VerticalAlignment="Stretch">
            <Slider Orientation="Vertical" TickPlacement="Both" LargeChange="0.1" Maximum="1" SmallChange="0.01" TickFrequency="0.02" Height="90" TabIndex="2" Value="{Binding G, Mode=TwoWay}"/>
        </Viewbox>
        <Viewbox HorizontalAlignment="Stretch" Grid.Row="2" Grid.Column="3"  VerticalAlignment="Stretch">
            <Slider Orientation="Vertical" TickPlacement="Both" LargeChange="0.1" Maximum="1" SmallChange="0.01" TickFrequency="0.02" Height="90" Value="{Binding B, Mode=TwoWay}"/>
        </Viewbox>
    </Grid>
</UserControl>

I bound the Brush Color of the Labels to their respective colors in the View Model (A got the entire thing). I Two-Way Bound the value of each slider to it's respective value within the view model, and in the code I bound the Dependency Property to the view model Color property. I tested this, and it worked.

Once again, thank you all for your help.

Answer 2

First of all, I'd recommend making these changes to your ByteToColorConverter:

public class DoubleToColorConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        // Values bound to sliders are going to be doubles.
        return Color.FromScRgb((float)(double)values[0], (float)(double)values[1], (float)(double)values[2], (float)(double)values[3]);
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        Color C = (Color)value;
        return new object[] { (double)C.ScA, (double)C.ScR, (double)C.ScG, (double)C.ScB };
    }
}

I've switched from bytes to doubles, as the slider value you're trying to bind to will only return/accept doubles. The (float)(double) cast is to deal with unboxing the values in the array.

With this XAML, I was able to get a basic ARGB colour mixer working. Notice I've changed the Min/Max values on the slider, now we're not dealing with bytes anymore.

<StackPanel>
    <Slider x:Name="sdrAlpha" Height="32" LargeChange="0.5" SmallChange="0.1" Minimum="0" Maximum="1" Width="321" TickPlacement="Both"/>
    <Slider x:Name="sdrRed" Height="32" LargeChange="0.5" SmallChange="0.1" Minimum="0" Maximum="1" Width="321" TickPlacement="Both"/>
    <Slider x:Name="sdrGreen" Height="32" LargeChange="0.5" SmallChange="0.1" Minimum="0" Maximum="1" Width="321" TickPlacement="Both"/>
    <Slider x:Name="sdrBlue" Height="32" LargeChange="0.5" SmallChange="0.1" Minimum="0" Maximum="1" Width="321" TickPlacement="Both"/>
    <Border x:Name="colourBorder" Height="200" HorizontalAlignment="Stretch">
        <Border.Background>
            <SolidColorBrush>
                <SolidColorBrush.Color>
                    <MultiBinding Converter="{StaticResource colorConverter}">
                        <Binding ElementName="sdrAlpha" Path="Value" Mode="TwoWay" />
                        <Binding ElementName="sdrRed" Path="Value" Mode="TwoWay" />
                        <Binding ElementName="sdrGreen" Path="Value" Mode="TwoWay" />
                        <Binding ElementName="sdrBlue" Path="Value" Mode="TwoWay" />
                    </MultiBinding>
                </SolidColorBrush.Color>
            </SolidColorBrush>
        </Border.Background>
    </Border>
</StackPanel>

If you wanted to bind a single slider to the converter, you could update your converter to inspect the number of values in the values[] array. You could perhaps use the ConverterParameter to pass in the colour you'd like that single slider to affect ... something like this:

<MultiBinding Converter="{StaticResource colorConverter}" ConverterParameter="Red">
    <Binding ElementName="sdrRed" Path="Value" Mode="TwoWay" />
</MultiBinding>