New UWP Community Toolkit - XAML Brushes

概述

上一篇 New UWP Community Toolkit 文章中，我们对 V2.2.0 版本的重要更新做了简单回顾。接下来会针对每个重要更新，结合 SDK 源代码和调用代码详细讲解。

本篇我们会针对 XAML Brushes 做详细分享。

Source:  https://github.com/Microsoft/UWPCommunityToolkit/tree/master/Microsoft.Toolkit.Uwp.UI/Media

Doc: https://docs.microsoft.com/zh-cn/windows/uwpcommunitytoolkit/

Namespace: Microsoft.Toolkit.Uwp.UI.Media;  Nuget: Microsoft.Toolkit.Uwp.UI

下面是 Nuget 安装时的一些重要信息：

我们看到依赖项中，除了 UAP（Windows 10 SDK）和 Microsoft.Toolkit.Uwp，还有一个依赖项是 Win2D.uwp，这和我们今天分享的内容有很紧密的关联。

Win2D 相信广大 UWPer 都不陌生了，UWP 图形渲染方面非常常用的库，引用一段官方介绍吧：

Win2D is an easy-to-use Windows Runtime API for immediate mode 2D graphics rendering with GPU acceleration. It is available to C#, C++ and VB developers writing Windows apps for Windows 8.1, Windows Phone 8.1 and Windows 10. It utilizes the power of Direct2D, and integrates seamlessly with XAML and CoreWindow.

Source: https://github.com/Microsoft/Win2D

Doc: http://microsoft.github.io/Win2D/html/Introduction.htm

Sample App: https://www.microsoft.com/store/apps/9NBLGGGXWT9F

代码分析

XAML Brushes 是 V2.2.0 版本新增加的功能，目前共支持 7 种画刷，它们都继承自 XamlCompositionBrushBase，一个创建 XAML Brushes 的基类，使用 CompositionBrush 来绘制一个区域；而实现效果都是用了 Win2D 中不同的 Effect。

XamlCompositionBrushBase Doc: https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.media.xamlcompositionbrushbase

下面我们依次做代码分析和功能体验。由于源代码篇幅较长，我们只截取关键部分。

1. BackdropBlurBrush

下面是 BackdropBlurBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source:https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/BackdropBlurBrush.cs

BackdropBlurBrush 使用的是 Win2D 中的 GaussianBlurEffect

Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_GaussianBlurEffect.htm

/// <summary>
/// Initializes the Composition Brush.
/// </summary>
protected override void OnConnected()
{
    // Delay creating composition resources until they're required.
    if (CompositionBrush == null)
    {
        // Abort if effects aren't supported.
        if (!CompositionCapabilities.GetForCurrentView().AreEffectsSupported())
        {
            return;
        }

        var backdrop = Window.Current.Compositor.CreateBackdropBrush();

        // Use a Win2D blur affect applied to a CompositionBackdropBrush.
        var graphicsEffect = new GaussianBlurEffect
        {
            Name = "Blur",
            BlurAmount = (float)Amount,
            Source = new CompositionEffectSourceParameter("backdrop")
        };

        var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect, new[] { "Blur.BlurAmount" });
        var effectBrush = effectFactory.CreateBrush();

        effectBrush.SetSourceParameter("backdrop", backdrop);

        CompositionBrush = effectBrush;
    }
}

BackdropBlurBrush 本身的源代码和使用方法都比较简单，来看一下使用方法和显示效果吧：

引入 BackdropBlurBrush 后，通过设置 Amount 来设置模糊的程度，Amount >= 0，默认值是 3.0，值越大模糊程度越高，为 0.0 时没有模糊效果。

我们把 Grid 分为两列，分别放了同样的图片，左侧是原图，右侧是实现了 BackdropBlurBrush 的图像；可以明显看出高斯模糊的画刷效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
    <Border Grid.Column="1">
        <Border.Background>
            <controls:BackdropBlurBrush Amount="10"/>
        </Border.Background>
    </Border>
</Grid>

2. BackdropGammaTransferBrush

下面是 BackdropGammaTransferBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source: https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/BackdropGammaTransferBrush.cs

BackdropGammaTransferBrush 使用的是 Win2D 中的 GammaTransferEffect

Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_GammaTransferEffect.htm

/// <summary>
/// Initializes the Composition Brush.
/// </summary>
protected override void OnConnected()
{
    // Delay creating composition resources until they're required.
    if (CompositionBrush == null)
    {
        // Abort if effects aren't supported.
        if (!CompositionCapabilities.GetForCurrentView().AreEffectsSupported())
        {
            return;
        }

        var backdrop = Window.Current.Compositor.CreateBackdropBrush();

        // Use a Win2D blur affect applied to a CompositionBackdropBrush.
        var graphicsEffect = new GammaTransferEffect
        {
            Name = "GammaTransfer",
            AlphaAmplitude = (float)AlphaAmplitude,
            ...
            Source = new CompositionEffectSourceParameter("backdrop")
        };

        var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect, new[]
        {
            "GammaTransfer.AlphaAmplitude",
            ...
        });
        var effectBrush = effectFactory.CreateBrush();

        effectBrush.SetSourceParameter("backdrop", backdrop);

        CompositionBrush = effectBrush;
    }
}

BackdropGammaTransferBrush 本身的源代码和使用方法也都比较简单，直接看一下使用方法和显示效果吧：

引入 BackdropGammaTransferBrush 后，通过分别设置 A R G B 四个通道的变换值来改变颜色显示；

我们把 Grid 分为两列，分别放了同样的图片，左侧是原图，右侧是实现了 BackdropGammaTransferBrush 的图像；可以明显看出伽玛变换画刷效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
    <Border Grid.Column="1">
        <Border.Background>
                <controls:BackdropGammaTransferBrush RedAmplitude="3.25" GreenAmplitude="1" BlueAmplitude="1"/>
        </Border.Background>
    </Border>
</Grid>

3. BackdropInvertBrush

下面是 BackdropInvertBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source: https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/BackdropInvertBrush.cs

BackdropInvertBrush 使用的是 Win2D 中的 InvertEffect

Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_InvertEffect.htm

/// <summary>
/// Initializes the Composition Brush.
/// </summary>
protected override void OnConnected()
{
    // Delay creating composition resources until they're required.
    if (CompositionBrush == null)
    {
        // Abort if effects aren't supported.
        if (!CompositionCapabilities.GetForCurrentView().AreEffectsSupported())
        {
            return;
        }

        var backdrop = Window.Current.Compositor.CreateBackdropBrush();

        // Use a Win2D invert affect applied to a CompositionBackdropBrush.
        var graphicsEffect = new InvertEffect
        {
            Name = "Invert",
            Source = new CompositionEffectSourceParameter("backdrop")
        };

        var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect);
        var effectBrush = effectFactory.CreateBrush();

        effectBrush.SetSourceParameter("backdrop", backdrop);

        CompositionBrush = effectBrush;
    }
}

看一下使用方法和显示效果吧：

我们把 Grid 分为两列，分别放了同样的图片，左侧是原图，右侧是实现了 BackdropInvertBrush 的图像；可以明显看出反转画刷效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
    <Border Grid.Column="1">
        <Border.Background>
                <controls:BackdropInvertBrush/>
        </Border.Background>
    </Border>
</Grid>

4. BackdropSaturaionBrush

下面是 BackdropSaturaionBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source: https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/BackdropSaturationBrush.cs

BackdropSaturaionBrush 使用的是 Win2D 中的 SaturationEffect

Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_SaturationEffect.htm

/// <summary>
/// Initializes the Composition Brush.
/// </summary>
protected override void OnConnected()
{
    // Delay creating composition resources until they're required.
    if (CompositionBrush == null)
    {
        // Abort if effects aren't supported.
        if (!CompositionCapabilities.GetForCurrentView().AreEffectsSupported())
        {
            return;
        }

        var backdrop = Window.Current.Compositor.CreateBackdropBrush();

        // Use a Win2D blur affect applied to a CompositionBackdropBrush.
        var graphicsEffect = new SaturationEffect
        {
            Name = "Saturation",
            Saturation = (float)Saturation,
            Source = new CompositionEffectSourceParameter("backdrop")
        };

        var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect, new[] { "Saturation.Saturation" });
        var effectBrush = effectFactory.CreateBrush();

        effectBrush.SetSourceParameter("backdrop", backdrop);

        CompositionBrush = effectBrush;
    }
}

看一下使用方法和显示效果吧：

引入 BackdropSaturaionBrush 后，通过设置 Saturaion 的值来调整饱和度的值；取值范围是 [0, 1]，默认是 0.5，值越大饱和度越高，为 0 时图像为黑色单色。

我们把 Grid 分为两列，分别放了同样的图片，左侧是原图，右侧是实现了 BackdropSaturaionBrush 的图像；可以明显看出饱和度画刷效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
    <Border Grid.Column="1">
        <Border.Background>
                <controls:BackdropSaturationBrush Saturation="0.4"/>
        </Border.Background>
    </Border>
</Grid>

5. BackdropSepiaBrush

下面是 BackdropSepiaBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source: https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/BackdropSepiaBrush.cs

BackdropSepiaBrush 使用的是 Win2D 中的 SepiaEffect

Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_SepiaEffect.htm

/// <summary>
/// Initializes the Composition Brush.
/// </summary>
protected override void OnConnected()
{
    // Delay creating composition resources until they're required.
    if (CompositionBrush == null)
    {
        // Abort if effects aren't supported.
        if (!CompositionCapabilities.GetForCurrentView().AreEffectsSupported())
        {
            return;
        }

        var backdrop = Window.Current.Compositor.CreateBackdropBrush();

        // Use a Win2D blur affect applied to a CompositionBackdropBrush.
        var graphicsEffect = new SepiaEffect
        {
            Name = "Sepia",
            Intensity = (float)Intensity,
            Source = new CompositionEffectSourceParameter("backdrop")
        };

        var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect, new[] { "Sepia.Intensity" });
        var effectBrush = effectFactory.CreateBrush();

        effectBrush.SetSourceParameter("backdrop", backdrop);

        CompositionBrush = effectBrush;
    }
}

看一下使用方法和显示效果吧：

引入 BackdropSepiaBrush 后，通过设置 Intensity 的值来调整深色的值；取值范围是 [0, 1]，默认是 0.5，值越大深色度越高。

我们把 Grid 分为两列，分别放了同样的图片，左侧是原图，右侧是实现了 BackdropSepiaBrush 的图像；可以明显看出深色画刷效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
    <Border Grid.Column="1">
        <Border.Background>
                <controls:BackdropSepiaBrush Intensity="0.8"/>
        </Border.Background>
    </Border>
</Grid>

6. ImageBlendBrush

下面是 ImageBlendBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source: https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/ImageBlendBrush.cs

ImageBlendBrush 使用的是 Win2D 中的 BlendEffect  去融合两张图片

Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_BlendEffect.htm

protected override void OnConnected()
{
    // Delay creating composition resources until they're required.
    if (CompositionBrush == null && Source != null && Source is BitmapImage bitmap)
    {
        // Use LoadedImageSurface API to get ICompositionSurface from image uri provided
        // If UriSource is invalid, StartLoadFromUri will return a blank texture.
        _surface = LoadedImageSurface.StartLoadFromUri(bitmap.UriSource);

        // Load Surface onto SurfaceBrush
        _surfaceBrush = Window.Current.Compositor.CreateSurfaceBrush(_surface);
        _surfaceBrush.Stretch = CompositionStretchFromStretch(Stretch);

        // Abort if effects aren't supported.
        if (!CompositionCapabilities.GetForCurrentView().AreEffectsSupported())
        {
            // Just use image straight-up, if we don't support effects.
            CompositionBrush = _surfaceBrush;
            return;
        }

        var backdrop = Window.Current.Compositor.CreateBackdropBrush();

        // Use a Win2D invert affect applied to a CompositionBackdropBrush.
        var graphicsEffect = new BlendEffect
        {
            Name = "Invert",
            Mode = (BlendEffectMode)(int)Mode,
            Background = new CompositionEffectSourceParameter("backdrop"),
            Foreground = new CompositionEffectSourceParameter("image")
        };

        var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect);
        var effectBrush = effectFactory.CreateBrush();

        effectBrush.SetSourceParameter("backdrop", backdrop);
        effectBrush.SetSourceParameter("image", _surfaceBrush);

        CompositionBrush = effectBrush;
    }
}

大致实现过程是：加载 ImageBlendBrush 画刷所用的 Bitmap，到 SurfaceBrush，使用 Win2D 的 BlendBrush，把 SurfaceBrush 设置进去。

我们看到这里的 BlendEffectMode 设置，会影响融合的方式和效果，效果如下图：

详见 Win2D Doc: http://microsoft.github.io/Win2D/html/T_Microsoft_Graphics_Canvas_Effects_BlendEffectMode.htm

看一下使用方法和显示效果吧：

我们把 Grid 分为两列，分别放了同样的图片去实现 ImageBlendBrush，左侧 Mode=‘Color’，右侧 Mode='Subtract'；大家可以多尝试不同的 Mode 去体验效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
    <Border Grid.Column="0">
        <Border.Background>
            <controls:ImageBlendBrush Source="ms-appx:///Assets/shaomeng.jpg" Mode="Color"/>
        </Border.Background>
    </Border>
    <Border Grid.Column="1">
        <Border.Background>
            <controls:ImageBlendBrush Source="ms-appx:///Assets/shaomeng.jpg" Mode="Subtract"/>
        </Border.Background>
    </Border>
</Grid>

7. RadialGradientBrush

下面是 RadialGradientBrush 中创建画刷的源代码，大家也可以在 Git 中查看：

Source: https://github.com/Microsoft/UWPCommunityToolkit/blob/master/Microsoft.Toolkit.Uwp.UI/Media/RadialGradientBrush.cs

RadialGradientBrush 是 WPF RadialGradientBrush 的移植，使用 Win2D FillRectangle 的方式实现绘制过程.

Doc: https://msdn.microsoft.com/en-us/library/system.windows.media.radialgradientbrush(v=vs.110).aspx

/// <inheritdoc/>
protected override bool OnDraw(CanvasDevice device, CanvasDrawingSession session, Vector2 size)
{
    // Create our Brush
    if (GradientStops != null && GradientStops.Count > 0)
    {
        var gradientBrush = new CanvasRadialGradientBrush(
                                device,
                                GradientStops.ToWin2DGradientStops(),
                                SpreadMethod.ToEdgeBehavior(),
                                (CanvasAlphaMode)(int)AlphaMode,
                                ColorInterpolationMode.ToCanvasColorSpace(),
                                CanvasColorSpace.Srgb,
                                CanvasBufferPrecision.Precision8UIntNormalized)
        {
            // Calculate Surface coordinates from 0.0-1.0 range given in WPF brush
            RadiusX = size.X * (float)RadiusX,
            RadiusY = size.Y * (float)RadiusY,
            Center = size * Center.ToVector2(),

            // Calculate Win2D Offset from origin/center used in WPF brush
            OriginOffset = size * (GradientOrigin.ToVector2() - Center.ToVector2()),
        };

        // Use brush to draw on our canvas
        session.FillRectangle(size.ToRect(), gradientBrush);

        gradientBrush.Dispose();

        return true;
    }

    return false;
}

看一下使用方法和显示效果吧：

和 WPF 的 RadialGradientBrush 使用方式很类似，引入画刷后，设置径向渐变的中心，半径和渐变的停顿点等；

我们把 Grid 分为两列，分别放了同样的图片，左侧是原图，右侧是实现了 BackdropSepiaBrush 的图像；可以明显看出径向渐变画刷效果。

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="*"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="0"/>
        <Image Source="Assets/02.jpg" Stretch="UniformToFill" Grid.Column="1"/>
        <Border Grid.Column="1">
        <Border.Background>
                <controls:RadialGradientBrush
                AlphaMode="Premultiplied"
                Center="0.5,0.5"
                ColorInterpolationMode="SRgbLinearInterpolation"
                GradientOrigin="0.5,0.5"
                Opacity="1"
                RadiusX="0.5"
                RadiusY="0.5"
                SpreadMethod="Pad">
                    <GradientStop Color="Red" Offset="0" />
                    <GradientStop Color="Transparent" Offset="0.25" />
                    <GradientStop Color="Yellow" Offset="0.50" />
                    <GradientStop Color="Transparent" Offset="0.75" />
                    <GradientStop Color="Green" Offset="1.0" />
                </controls:RadialGradientBrush>
            </Border.Background>
    </Border>
</Grid>

总结

到这里我们就把 UWP Community Toolkit V2.2.0 中实现的 7 种画刷介绍完了，我们更多的从源代码的实现和 SDK 的简单实用角度来分析，如果大家有兴趣，可以多尝试每种画刷里的参数设置不同值时的效果；如果工作中上面 7 种画刷不满足需求，也可以在 Win2D 寻找更多种类的画刷去封装实现。

欢迎大家多多交流，有任何疑问或建议，欢迎留言告诉我，谢谢！