性质减法的ColorAnimation

Question

如何使WPF通过属性从模板绑定的背景中减去？

我想使用"By“属性动画按钮模板的背景。如果我需要使背景变浅，它就能正确地工作，因为"By“加起来是”背景色“。但实际上，我想让它变得更暗，我不知道如何使WPF从模板绑定的背景中通过属性减去。

<Border x:Name="BackRect" Background="{TemplateBinding Background}" 
                CornerRadius="15" BorderThickness="0" Height="115" Width="215">
                <ContentControl x:Name="MainTitle"
                            FontFamily="Inter"    
                            FontSize="{TemplateBinding FontSize}" 
                            Content="{TemplateBinding Content}"
                            HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>

<ControlTemplate.Triggers>
            <EventTrigger RoutedEvent="MouseEnter">
                <BeginStoryboard>
                    <Storyboard> 
                        <ColorAnimation Storyboard.TargetName="BackRect" Storyboard.TargetProperty=(Button.Background).(SolidColorBrush.Color)"
                                        By="#A0A0A0" FillBehavior="HoldEnd" Duration="0:0:0.3" >
                            <ColorAnimation.EasingFunction>
                                <SineEase EasingMode="EaseOut"/>
                            </ColorAnimation.EasingFunction>
                        </ColorAnimation>
                    </Storyboard>
                </BeginStoryboard>
            </EventTrigger>
</ControlTemplate.Triggers>

Answer 1

似乎，尽管在文档中显然没有提到，但是您可以对颜色结构的ScA、ScR、ScG和ScB属性使用负值，这样就可以通过颜色动画的By属性获得减去的颜色。

下面是一个示例：

<Rectangle Width="300" Height="200">
    <Rectangle.Fill>
        <SolidColorBrush Color="Red"/>
    </Rectangle.Fill>
    <Rectangle.Triggers>
        <EventTrigger RoutedEvent="MouseEnter">
            <BeginStoryboard Name="AnimateFillColor">
                <Storyboard>
                    <ColorAnimation
                        Storyboard.TargetProperty="Fill.Color"
                        Duration="0:0:0.2">
                        <ColorAnimation.By>
                            <Color ScR="-0.5"/>
                        </ColorAnimation.By>
                    </ColorAnimation>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
        <EventTrigger RoutedEvent="MouseLeave">
            <StopStoryboard BeginStoryboardName="AnimateFillColor"/>
        </EventTrigger>
    </Rectangle.Triggers>
</Rectangle>