How to: Animate the Position or Color of a Gradient Stop
This example shows how to animate the Color and Offset of GradientStop objects.
Example
The following example animates three gradient stops inside a LinearGradientBrush. The example uses three animations, each of which animates a different gradient stop:
The first animation, a DoubleAnimation, animates the first gradient stop's Offset from 0.0 to 1.0 and then back to 0.0. As a result, the first color in the gradient shifts from the left side to the right side of the rectangle and then back to the left side.
The second animation, a ColorAnimation, animates the second gradient stop's Color from Purple to Yellow and then back to Purple. As a result, the middle color in the gradient changes from purple to yellow and back to purple.
The third animation, another ColorAnimation, animates the opacity of the third gradient stop's Color by -1 and then back. As a result, the third color in the gradient fades away and then becomes opaque again.
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 GradientStopAnimationExample
Inherits Page
Public Sub New()
Title = "GradientStop Animation Example"
Background = Brushes.White
' Create a NameScope for the page so that
' Storyboards can be used.
NameScope.SetNameScope(Me, New NameScope())
' Create a rectangle. This rectangle will
' be painted with a gradient.
Dim aRectangle As New Rectangle()
aRectangle.Width = 200
aRectangle.Height = 100
aRectangle.Stroke = Brushes.Black
aRectangle.StrokeThickness = 1
' Create a LinearGradientBrush to paint
' the rectangle's fill.
Dim gradientBrush As New LinearGradientBrush()
' Create gradient stops for the brush.
Dim stop1 As New GradientStop(Colors.MediumBlue, 0.0)
Dim stop2 As New GradientStop(Colors.Purple, 0.5)
Dim stop3 As New GradientStop(Colors.Red, 1.0)
' Register a name for each gradient stop with the
' page so that they can be animated by a storyboard.
Me.RegisterName("GradientStop1", stop1)
Me.RegisterName("GradientStop2", stop2)
Me.RegisterName("GradientStop3", stop3)
' Add the stops to the brush.
gradientBrush.GradientStops.Add(stop1)
gradientBrush.GradientStops.Add(stop2)
gradientBrush.GradientStops.Add(stop3)
' Apply the brush to the rectangle.
aRectangle.Fill = gradientBrush
'
' Animate the first gradient stop's offset from
' 0.0 to 1.0 and then back to 0.0.
'
Dim offsetAnimation As New DoubleAnimation()
offsetAnimation.From = 0.0
offsetAnimation.To = 1.0
offsetAnimation.Duration = TimeSpan.FromSeconds(1.5)
offsetAnimation.AutoReverse = True
Storyboard.SetTargetName(offsetAnimation, "GradientStop1")
Storyboard.SetTargetProperty(offsetAnimation, New PropertyPath(GradientStop.OffsetProperty))
'
' Animate the second gradient stop's color from
' Purple to Yellow and then back to Purple.
'
Dim gradientStopColorAnimation As New ColorAnimation()
gradientStopColorAnimation.From = Colors.Purple
gradientStopColorAnimation.To = Colors.Yellow
gradientStopColorAnimation.Duration = TimeSpan.FromSeconds(1.5)
gradientStopColorAnimation.AutoReverse = True
Storyboard.SetTargetName(gradientStopColorAnimation, "GradientStop2")
Storyboard.SetTargetProperty(gradientStopColorAnimation, New PropertyPath(GradientStop.ColorProperty))
' Set the animation to begin after the first animation
' ends.
gradientStopColorAnimation.BeginTime = TimeSpan.FromSeconds(3)
'
' Animate the third gradient stop's color so
' that it becomes transparent.
'
Dim opacityAnimation As New ColorAnimation()
' Reduces the target color's alpha value by 1,
' making the color transparent.
opacityAnimation.By = Color.FromScRgb(-1.0F, 0F, 0F, 0F)
opacityAnimation.Duration = TimeSpan.FromSeconds(1.5)
opacityAnimation.AutoReverse = True
Storyboard.SetTargetName(opacityAnimation, "GradientStop3")
Storyboard.SetTargetProperty(opacityAnimation, New PropertyPath(GradientStop.ColorProperty))
' Set the animation to begin after the first two
' animations have ended.
opacityAnimation.BeginTime = TimeSpan.FromSeconds(6)
' Create a Storyboard to apply the animations.
Dim gradientStopAnimationStoryboard As New Storyboard()
gradientStopAnimationStoryboard.Children.Add(offsetAnimation)
gradientStopAnimationStoryboard.Children.Add(gradientStopColorAnimation)
gradientStopAnimationStoryboard.Children.Add(opacityAnimation)
' Begin the storyboard when the left mouse button is
' pressed over the rectangle.
AddHandler aRectangle.MouseLeftButtonDown, Sub(sender As Object, e As MouseButtonEventArgs) gradientStopAnimationStoryboard.Begin(Me)
Dim mainPanel As New StackPanel()
mainPanel.Margin = New Thickness(10)
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 GradientStopAnimationExample : Page
{
public GradientStopAnimationExample()
{
Title = "GradientStop Animation Example";
Background = Brushes.White;
// Create a NameScope for the page so that
// Storyboards can be used.
NameScope.SetNameScope(this, new NameScope());
// Create a rectangle. This rectangle will
// be painted with a gradient.
Rectangle aRectangle = new Rectangle();
aRectangle.Width = 200;
aRectangle.Height = 100;
aRectangle.Stroke = Brushes.Black;
aRectangle.StrokeThickness = 1;
// Create a LinearGradientBrush to paint
// the rectangle's fill.
LinearGradientBrush gradientBrush = new LinearGradientBrush();
// Create gradient stops for the brush.
GradientStop stop1 = new GradientStop(Colors.MediumBlue, 0.0);
GradientStop stop2 = new GradientStop(Colors.Purple, 0.5);
GradientStop stop3 = new GradientStop(Colors.Red, 1.0);
// Register a name for each gradient stop with the
// page so that they can be animated by a storyboard.
this.RegisterName("GradientStop1", stop1);
this.RegisterName("GradientStop2", stop2);
this.RegisterName("GradientStop3", stop3);
// Add the stops to the brush.
gradientBrush.GradientStops.Add(stop1);
gradientBrush.GradientStops.Add(stop2);
gradientBrush.GradientStops.Add(stop3);
// Apply the brush to the rectangle.
aRectangle.Fill = gradientBrush;
//
// Animate the first gradient stop's offset from
// 0.0 to 1.0 and then back to 0.0.
//
DoubleAnimation offsetAnimation = new DoubleAnimation();
offsetAnimation.From = 0.0;
offsetAnimation.To = 1.0;
offsetAnimation.Duration = TimeSpan.FromSeconds(1.5);
offsetAnimation.AutoReverse = true;
Storyboard.SetTargetName(offsetAnimation, "GradientStop1");
Storyboard.SetTargetProperty(offsetAnimation,
new PropertyPath(GradientStop.OffsetProperty));
//
// Animate the second gradient stop's color from
// Purple to Yellow and then back to Purple.
//
ColorAnimation gradientStopColorAnimation = new ColorAnimation();
gradientStopColorAnimation.From = Colors.Purple;
gradientStopColorAnimation.To = Colors.Yellow;
gradientStopColorAnimation.Duration = TimeSpan.FromSeconds(1.5);
gradientStopColorAnimation.AutoReverse = true;
Storyboard.SetTargetName(gradientStopColorAnimation, "GradientStop2");
Storyboard.SetTargetProperty(gradientStopColorAnimation,
new PropertyPath(GradientStop.ColorProperty));
// Set the animation to begin after the first animation
// ends.
gradientStopColorAnimation.BeginTime = TimeSpan.FromSeconds(3);
//
// Animate the third gradient stop's color so
// that it becomes transparent.
//
ColorAnimation opacityAnimation = new ColorAnimation();
// Reduces the target color's alpha value by 1,
// making the color transparent.
opacityAnimation.By = Color.FromScRgb(-1.0F, 0F, 0F, 0F);
opacityAnimation.Duration = TimeSpan.FromSeconds(1.5);
opacityAnimation.AutoReverse = true;
Storyboard.SetTargetName(opacityAnimation, "GradientStop3");
Storyboard.SetTargetProperty(opacityAnimation,
new PropertyPath(GradientStop.ColorProperty));
// Set the animation to begin after the first two
// animations have ended.
opacityAnimation.BeginTime = TimeSpan.FromSeconds(6);
// Create a Storyboard to apply the animations.
Storyboard gradientStopAnimationStoryboard = new Storyboard();
gradientStopAnimationStoryboard.Children.Add(offsetAnimation);
gradientStopAnimationStoryboard.Children.Add(gradientStopColorAnimation);
gradientStopAnimationStoryboard.Children.Add(opacityAnimation);
// Begin the storyboard when the left mouse button is
// pressed over the rectangle.
aRectangle.MouseLeftButtonDown += delegate(object sender, MouseButtonEventArgs e)
{
gradientStopAnimationStoryboard.Begin(this);
};
StackPanel mainPanel = new StackPanel();
mainPanel.Margin = new Thickness(10);
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="GradientStop Animation Example"
Background="White">
<StackPanel Margin="10">
<Rectangle
Width="200"
Height="100"
Stroke="Black" StrokeThickness="1">
<Rectangle.Fill>
<LinearGradientBrush>
<GradientStop x:Name="GradientStop1" Color="MediumBlue" Offset="0.0" />
<GradientStop x:Name="GradientStop2" Color="Purple" Offset="0.5" />
<GradientStop x:Name="GradientStop3" Color="Red" Offset="1.0" />
</LinearGradientBrush>
</Rectangle.Fill>
<Rectangle.Triggers>
<EventTrigger RoutedEvent="Rectangle.MouseLeftButtonDown">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="GradientStop1"
Storyboard.TargetProperty="Offset"
From="0.0" To="1.0" Duration="0:0:1.5"
AutoReverse="True" />
<ColorAnimation
Storyboard.TargetName="GradientStop2"
Storyboard.TargetProperty="Color"
From="Purple" To="Yellow"
Duration="0:0:1.5"
AutoReverse="True"
BeginTime="0:0:3" />
<ColorAnimation
Storyboard.TargetName="GradientStop3"
Storyboard.TargetProperty="Color"
Duration="0:0:1.5"
AutoReverse="True"
BeginTime="0:0:6">
<ColorAnimation.By>
<Color ScA="-1" ScR="0" ScB="0" ScG="0" />
</ColorAnimation.By>
</ColorAnimation>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</Rectangle.Triggers>
</Rectangle>
</StackPanel>
</Page>
Although this example uses a LinearGradientBrush, the process is the same for animating GradientStop objects inside a RadialGradientBrush.
For additional examples, see the Brushes Sample.