RadialGradientBrush Class (System.Windows.Media)

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework 3.0

.NET Framework Class Library

RadialGradientBrush Class

Updated: November 2007

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)
XMLNS for XAML: http://schemas.microsoft.com/winfx/xaml/presentation

Syntax

Visual Basic (Declaration)

Public NotInheritable Class RadialGradientBrush _
    Inherits GradientBrush

Visual Basic (Usage)

Dim instance As RadialGradientBrush

public sealed class RadialGradientBrush : GradientBrush

Visual C++

public ref class RadialGradientBrush sealed : public GradientBrush

public final class RadialGradientBrush extends GradientBrush

JScript

public final class RadialGradientBrush extends GradientBrush

XAML Object Element Usage

<RadialGradientBrush>
  GradientStops
</RadialGradientBrush>

Remarks

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

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

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 Freezable Objects Overview.

Examples

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;

        }

    }
}

XAML

<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.

Note:
The examples in this topic use the default coordinate system for setting control points . The default coordinate system is relative to a bounding box: 0 indicates 0 percent of the bounding box , and 1 indicates 100 percent of the bounding box. You can change this coordinate system by setting the MappingMode property to the value Absolute. An absolute coordinate system is not relative to a bounding box. Values are interpreted directly in local space.

Note:

The examples in this topic use the default coordinate system for setting control points . The default coordinate system is relative to a bounding box: 0 indicates 0 percent of the bounding box , and 1 indicates 100 percent of the bounding box. You can change this coordinate system by setting the MappingMode property to the value Absolute. An absolute coordinate system is not relative to a bounding box. Values are interpreted directly in local space.

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

Inheritance Hierarchy

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

Thread Safety

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

Platforms

Windows Vista

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information