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RadialGradientBrush Class

Paints an area with a radial gradient. A focal point defines the beginning of the gradient, and a circle defines the end point of the gradient.

Namespace: System.Windows.Media
Assembly: PresentationCore (in presentationcore.dll)
XML Namespace:  http://schemas.microsoft.com/winfx/2006/xaml/presentation

public sealed class RadialGradientBrush : GradientBrush
public final class RadialGradientBrush extends GradientBrush
public final class RadialGradientBrush extends GradientBrush
<RadialGradientBrush>
  GradientStops
</RadialGradientBrush>

The RadialGradientBrush is similar in programming model to the LinearGradientBrush. However, the linear gradient has a start and an end point to define the gradient vector, while the radial gradient has a circle, along with a focal point, to define the gradient behavior. The circle defines the end point of the gradient. In other words, a gradient stop at 1.0 defines the color at the circle's circumference. The focal point defines the center of the gradient. A gradient stop at 0.0 defines the color at the focal point.

The following image shows a rectangle filled with a radial gradient. The radial gradient that goes from white to gray. The outside circle represents the gradient circle while the red dot denotes the focal point. This gradient has its SpreadMethod set to Pad.

Radial gradient with a highlighted focal point


A radial gradient with highlighted components

NoteNote:

RadialGradientBrush objects are rendered using hardware acceleration on Tier 2 systems. For more information about hardware tiers, see the Graphics Rendering Tiers overview.

Freezable Features: Because it inherits from the Freezable class, the RadialGradientBrush class provides several special features: RadialGradientBrush objects can be declared as resources, shared among multiple objects, made read-only to improve performance, cloned, and made thread-safe. For more information about the different features provided by Freezable objects, see the Freezable Objects Overview.

This example shows how to use the RadialGradientBrush class to paint an area with a radial gradient.

The following example uses a RadialGradientBrush to paint a rectangle with a radial gradient that transitions from yellow to red to blue to lime green.


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;

        }

    }
}



<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>

The following illustration shows the gradient from the preceding example. The gradient's stops have been highlighted.

Gradient stops in a radial gradient

For additional RadialGradientBrush examples, see the Brushes Sample. For more information about gradients and other types of brushes, see Painting with WPF Brushes.

System.Object
   System.Windows.Threading.DispatcherObject
     System.Windows.DependencyObject
       System.Windows.Freezable
         System.Windows.Media.Animation.Animatable
           System.Windows.Media.Brush
             System.Windows.Media.GradientBrush
              System.Windows.Media.RadialGradientBrush

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0

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