如何：使用放射狀漸層繪製區域

此範例會示範如何使用 RadialGradientBrush 類別以放射漸層繪製區域。

範例

下列範例會使用 RadialGradientBrush 繪製矩形，其中的放射漸層會從黃色依序轉換為紅色、藍色和檸檬綠。

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace BrushesIntroduction
{
    public class RadialGradientBrushSnippet : Page
    {
        public RadialGradientBrushSnippet()
        {
            Title = "RadialGradientBrush Example";
            Background = Brushes.White;
            Margin = new Thickness(20);

            //
            // Create a RadialGradientBrush with four gradient stops.
            //
            RadialGradientBrush radialGradient = new RadialGradientBrush();

            // Set the GradientOrigin to the center of the area being painted.
            radialGradient.GradientOrigin = new Point(0.5, 0.5);

            // Set the gradient center to the center of the area being painted.
            radialGradient.Center = new Point(0.5, 0.5);

            // Set the radius of the gradient circle so that it extends to
            // the edges of the area being painted.
            radialGradient.RadiusX = 0.5;
            radialGradient.RadiusY = 0.5;

            // Create four gradient stops.
            radialGradient.GradientStops.Add(new GradientStop(Colors.Yellow, 0.0));
            radialGradient.GradientStops.Add(new GradientStop(Colors.Red, 0.25));
            radialGradient.GradientStops.Add(new GradientStop(Colors.Blue, 0.75));
            radialGradient.GradientStops.Add(new GradientStop(Colors.LimeGreen, 1.0));

            // Freeze the brush (make it unmodifiable) for performance benefits.
            radialGradient.Freeze();

            // Create a rectangle and paint it with the
            // RadialGradientBrush.
            Rectangle aRectangle = new Rectangle();
            aRectangle.Width = 200;
            aRectangle.Height = 100;
            aRectangle.Fill = radialGradient;

            StackPanel mainPanel = new StackPanel();
            mainPanel.Children.Add(aRectangle);
            Content = mainPanel;
        }
    }
}

Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Animation
Imports System.Windows.Shapes

Namespace BrushesIntroduction
    Public Class RadialGradientBrushSnippet
        Inherits Page
        Public Sub New()
            Title = "RadialGradientBrush Example"
            Background = Brushes.White
            Margin = New Thickness(20)

            '
            ' Create a RadialGradientBrush with four gradient stops.
            '
            Dim radialGradient As New RadialGradientBrush()

            ' Set the GradientOrigin to the center of the area being painted.
            radialGradient.GradientOrigin = New Point(0.5, 0.5)

            ' Set the gradient center to the center of the area being painted.
            radialGradient.Center = New Point(0.5, 0.5)

            ' Set the radius of the gradient circle so that it extends to
            ' the edges of the area being painted.
            radialGradient.RadiusX = 0.5
            radialGradient.RadiusY = 0.5

            ' Create four gradient stops.
            radialGradient.GradientStops.Add(New GradientStop(Colors.Yellow, 0.0))
            radialGradient.GradientStops.Add(New GradientStop(Colors.Red, 0.25))
            radialGradient.GradientStops.Add(New GradientStop(Colors.Blue, 0.75))
            radialGradient.GradientStops.Add(New GradientStop(Colors.LimeGreen, 1.0))

            ' Freeze the brush (make it unmodifiable) for performance benefits.
            radialGradient.Freeze()

            ' Create a rectangle and paint it with the 
            ' RadialGradientBrush.
            Dim aRectangle As New Rectangle()
            aRectangle.Width = 200
            aRectangle.Height = 100
            aRectangle.Fill = radialGradient

            Dim mainPanel As New StackPanel()
            mainPanel.Children.Add(aRectangle)
            Content = mainPanel

        End Sub

    End Class
End Namespace

<Page 
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="RadialGradientBrush Example"
  Background="White" Margin="20">
  <StackPanel>

    <!-- This rectangle is painted with a radial gradient. -->
    <Rectangle Width="200" Height="100">
      <Rectangle.Fill>
        <RadialGradientBrush 
          GradientOrigin="0.5,0.5" 
          Center="0.5,0.5" RadiusX="0.5" RadiusY="0.5">
          <RadialGradientBrush.GradientStops>
            <GradientStop Color="Yellow" Offset="0" />
            <GradientStop Color="Red" Offset="0.25" />
            <GradientStop Color="Blue" Offset="0.75" />
            <GradientStop Color="LimeGreen" Offset="1" />
          </RadialGradientBrush.GradientStops>
        </RadialGradientBrush>
      </Rectangle.Fill>
    </Rectangle>
  </StackPanel>
</Page>

下圖顯示上述範例中的漸層。 已醒目提示漸層的停駐點。

如需其他 RadialGradientBrush 範例，請參閱筆刷範例 (英文)。 如需有關漸層和其他筆刷類型的詳細資訊，請參閱使用純色和漸層繪製的概觀。