结合solidcolor刷

Question

有没有办法创造一种"solidcolorbrush",它是2种纯色画笔的混合物？

对于背面颜色,我希望能够将DynamicReference用于其他一些画笔.而另一种颜色(在前面)可以是具有不透明度的静态颜色.

如果这真的没有意义,请随时要求澄清!

Answer 1

我遇到了同样的问题.我通常只使用一个xaml用于基本的黑暗,基本的灯光,然后每个颜色重点使用一个(蓝色,红色等).重点是略微透视,当深色背景选择较暗的主题时,它会变暗.

当创建具有辅助强调颜色的主题以在应用程序中具有更多对比度时(例如,当选择浅色主题时为灰色,当暗主题时为强调色),我需要使用两种颜色构建画笔,否则我将不得不创建每种颜色都有深色和浅色的主题.

这是我使用的:

<DrawingBrush x:Key="SecondaryAccentColorBrush" Viewport="0,0,1,1" TileMode="Tile">
    <DrawingBrush.Drawing>
        <DrawingGroup>
            <GeometryDrawing>
                <GeometryDrawing.Geometry>
                    <RectangleGeometry Rect="0,0,1,1" />
                </GeometryDrawing.Geometry>
                <GeometryDrawing.Brush>
                    <SolidColorBrush Color="{DynamicResource AccentColor}"/>
                </GeometryDrawing.Brush>
            </GeometryDrawing>
            <GeometryDrawing>
                <GeometryDrawing.Geometry>
                    <RectangleGeometry Rect="0,0,1,1" />
                </GeometryDrawing.Geometry>
                <GeometryDrawing.Brush>
                    <SolidColorBrush Color="{DynamicResource Gray10}"/>
                </GeometryDrawing.Brush>
            </GeometryDrawing>
        </DrawingGroup>
    </DrawingBrush.Drawing>
</DrawingBrush>

切换主题时,"Gray10"的alpha值在00和FF之间切换,因此画笔显示灰色或强调色.

Answer 2

遗憾的是，WPF 中不支持自定义画笔（画笔类型被标记为“内部”且无法继承），因此无法像普通 SolidColorBrush 一样创建由两个画笔混合而成的画笔，并且可以从 XAML 使用该画笔。

作为解决方法，您可以使用 MarkupExtension 来模拟自定义画笔的行为，这允许您使用 XAML 语法并提供自定义值，从而允许我们使用内置的 SolidColorBrush（无需自定义画笔）设置为混合两种颜色时得到的值：

/// <summary>
/// Markup extension to mix two SolidColorBrushes together to produce a new SolidColorBrush.
/// </summary>
[MarkupExtensionReturnType(typeof(SolidColorBrush))]
public class MixedColorBrush : MarkupExtension, INotifyPropertyChanged
{
    /// <summary>
    /// The foreground mix color; defaults to white.  
    /// If not changed, the result will always be white.
    /// </summary>
    private SolidColorBrush foreground = Brushes.White;

    /// <summary>
    /// The background mix color; defaults to black.  
    /// If not set, the result will be the foreground color.
    /// </summary>
    private SolidColorBrush background = Brushes.Black;

    /// <summary>
    /// PropertyChanged event for WPF binding.
    /// </summary>
    public event PropertyChangedEventHandler PropertyChanged;

    /// <summary>
    /// Gets or sets the foreground mix color.
    /// </summary>
    public SolidColorBrush Foreground
    {
        get 
        { 
            return this.foreground; 
        }
        set 
        { 
            this.foreground = value; 
            this.NotifyPropertyChanged("Foreground"); 
        }
    }

    /// <summary>
    /// Gets or sets the background mix color.
    /// </summary>
    public SolidColorBrush Background
    {
        get 
        { 
            return this.background; 
        }
        set 
        { 
            this.background = value; 
            this.NotifyPropertyChanged("Background"); 
        }
    }

    /// <summary>
    /// Returns a SolidColorBrush that is set as the value of the 
    /// target property for this markup extension.
    /// </summary>
    /// <param name="serviceProvider">Object that can provide services for the markup extension.</param>
    /// <returns>The object value to set on the property where the extension is applied.</returns>
    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (this.foreground != null && this.background != null)
        {
            // Create a new brush as a composite of the old ones
            // This does simple non-perceptual additive color, e.g 
            // blue + red = magenta, but you can swap in a different
            // algorithm to do subtractive color (red + yellow = orange)
            return new SolidColorBrush(this.foreground.Color + this.background.Color);
        }

        // If either of the brushes was set to null, return an empty (white) brush.
        return new SolidColorBrush();
    }

    /// <summary>
    /// Raise the property changed event.
    /// </summary>
    /// <param name="propertyName">Name of the property which has changed.</param>
    protected void NotifyPropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
        {
            this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

然后可以像使用普通画笔一样从 XAML 使用它：

<Grid>
    <Grid.Background>
        <local:MixedColorBrush Foreground="Blue" Background="Red"/>
    </Grid.Background>
</Grid>

或者使用标记扩展语法：

<Grid Background="{local:MixedColorBrush Foreground=Blue, Background=Red}">

此方法的缺点是您无法使用 DynamicResource 或 StaticResource 引用将值绑定到应用程序中的其他资源。MarkupExtension 不是 DependencyObject，资源绑定仅适用于 DependencyObject；内置画笔是 DependencyObjects，这就是绑定适用于传统画笔的原因。