Como: Pintar uma Área com um Gradiente Radial

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

Exemplo

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.

Imports Microsoft.VisualBasic
Imports System
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

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="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="https://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.

Observação

The examples in this topic use the default coordinate system for setting control points.O sistema de coordenadas padrão é em relação a uma caixa delimitadora: 0 indica 0 por cento da caixa delimitadora, e 1 indica a 100 por cento da caixa delimitadora.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.

Para mais RadialGradientBrush exemplos, consulte o A amostra de pincéis. For more information about gradients and other types of brushes, see Painting with Solid Colors and Gradients Overview.