C#中的Drawing 类案例详解

<Window x:Class="DemoDrawing.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Drawing 示例" Width="300" Height="200">
    <Grid>
        <!-- 使用 DrawingBrush 做背景 -->
        <Rectangle x:Name="btnRect" Width="180" Height="60"
                   MouseEnter="BtnRect_MouseEnter"
                   MouseLeave="BtnRect_MouseLeave">
            <Rectangle.Resources>
                <!-- 阴影 Drawing -->
                <GeometryDrawing x:Key="shadow"
                                 Geometry="M 5,5 175,5 175,55 5,55 Z"
                                 Brush="#80000000">
                    <GeometryDrawing.Pen>
                        <Pen Brush="Transparent" Thickness="1"/>
                    </GeometryDrawing.Pen>
                </GeometryDrawing>
                <!-- 按钮主体 Drawing -->
                <GeometryDrawing x:Key="body" Geometry="M 0,0 170,0 170,50 0,50 Z">
                    <GeometryDrawing.Brush>
                        <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
                            <GradientStop Offset="0"  Color="#FF4C9AFF"/>
                            <GradientStop Offset="1"  Color="#FF0050DD"/>
                        </LinearGradientBrush>
                    </GeometryDrawing.Brush>
                    <GeometryDrawing.Pen>
                        <Pen Brush="#FF003399" Thickness="2"/>
                    </GeometryDrawing.Pen>
                </GeometryDrawing>
                <!-- 组合 DrawingGroup -->
                <DrawingGroup x:Key="combined">
                    <!-- 先画阴影 -->
                    <DrawingGroup.Children>
                        <DrawingGroup>
                            <DrawingGroup.Children>
                                <StaticResource ResourceKey="shadow"/>
                            </DrawingGroup.Children>
                            <DrawingGroup.BitmapEffect>
                                <BlurBitmapEffect Radius="5"/>
                            </DrawingGroup.BitmapEffect>
                        </DrawingGroup>
                        <!-- 再画按钮主体 -->
                        <StaticResource ResourceKey="body"/>
                    </DrawingGroup.Children>
                </DrawingGroup>
                <!-- 把 DrawingGroup 变成 Brush -->
                <DrawingBrush x:Key="btnBrush" Drawing="{StaticResource combined}"/>
            </Rectangle.Resources>
            <Rectangle.Fill>
                <StaticResource ResourceKey="btnBrush"/>
            </Rectangle.Fill>
        </Rectangle>
    </Grid>
</Window>

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }
    private void BtnRect_MouseEnter(object sender, MouseEventArgs e)
    {
        // 找到 Drawing 里的渐变刷
        var rect = (Rectangle)sender;
        var brush = (DrawingBrush)rect.Fill;
        var dg = (DrawingGroup)brush.Drawing;
        var body = (GeometryDrawing)((DrawingGroup)dg.Children[1]).Children[0];
        var lg = (LinearGradientBrush)body.Brush;
        // 动画高亮
        var da = new ColorAnimation(Color.FromRgb(0x6F, 0xBA, 0xFF),
                                    TimeSpan.FromMilliseconds(300));
        lg.GradientStops[0].BeginAnimation(GradientStop.ColorProperty, da);
    }
    private void BtnRect_MouseLeave(object sender, MouseEventArgs e)
    {
        var rect = (Rectangle)sender;
        var brush = (DrawingBrush)rect.Fill;
        var dg = (DrawingGroup)brush.Drawing;
        var body = (GeometryDrawing)((DrawingGroup)dg.Children[1]).Children[0];
        var lg = (LinearGradientBrush)body.Brush;
        var da = new ColorAnimation(Color.FromRgb(0x4C, 0x9A, 0xFF),
                                    TimeSpan.FromMilliseconds(300));
        lg.GradientStops[0].BeginAnimation(GradientStop.ColorProperty, da);
    }
}

protected override void OnPaint(PaintEventArgs e)
{
    var g = e.Graphics;
    g.SmoothingMode = SmoothingMode.AntiAlias;
    // 1. 阴影
    using (var path = CreateRoundRect(5, 5, 175, 55, 8))
    using (var brush = new SolidBrush(Color.FromArgb(128, 0, 0, 0)))
    using (var blur = new Bitmap(180, 60))
    {
        using (var g2 = Graphics.FromImage(blur))
        {
            g2.SmoothingMode = SmoothingMode.AntiAlias;
            g2.FillPath(brush, path);
        }
        // 手动高斯模糊（略）...
        g.DrawImage(blur, 0, 0);
    }
    // 2. 主体
    using (var path = CreateRoundRect(0, 0, 170, 50, 8))
    using (var brush = new LinearGradientBrush(
        new Point(0, 0), new Point(0, 50),
        Color.FromArgb(255, 0x4C, 0x9A, 0xFF),
        Color.FromArgb(255, 0x00, 0x50, 0xDD)))
    using (var pen = new Pen(Color.FromArgb(255, 0x00, 0x33, 0x99), 2))
    {
        g.FillPath(brush, path);
        g.DrawPath(pen, path);
    }
}
private GraphicsPath CreateRoundRect(float x, float y, float w, float h, float r)
{
    var gp = new GraphicsPath();
    gp.AddArc(x + w - r, y, r, r, 270, 90);
    gp.AddArc(x + w - r, y + h - r, r, r, 0, 90);
    gp.AddArc(x, y + h - r, r, r, 90, 90);
    gp.AddArc(x, y, r, r, 180, 90);
    gp.CloseFigure();
    return gp;
}