WPF Sample Series – Solution for the Obsolete BitmapEffect Property and Rendering an OuterGlowBitmapEffect

Since the release of .NET 3.5 SP1, I have been getting a new Visual Studio warning in my code where I have assigned a BitmapEffect to a UIElement.  Specifically I was using the OuterGlowBitmapEffect.

Warning 1 ‘Public Property BitmapEffect() As System.Windows.Media.Effects.BitmapEffect’ is obsolete: ‘Avoid using BitmapEffects as they have very poor performance characteristics.  They will be deprecated in a future version.  Consider using the UIElement.Effect property and ShaderEffects where appropriate instead.’

Problem

I needed an outer glow effect in my application so I read up on the new Effects property and the new Effect and ShaderEffects classes.  However, I could not find a replacement for the OuterGlowBitmapEffect that would work with the new UIElement.Effects property.

UIElement.BitmapEffect property is obsolete, making those bitmap effects we have been using obsolete also.

On the surface it seems the new UIElement.Effect property does not have an OuterGlowEffect class we can use to replace the OuterGlowBitmapEffect we have been using.

Solution

Today I was reading a WPF thread and found the solution that I want to share with you.

The simple example has four buttons, two with effects declared in  XAML the other two effects assigned in code.  When using the obsolete BitmapEffect property in XAML, no warnings are given by Visual Studio.  The warnings are only provided when you assign the BitmapEffect property a value in code.

Most of you are familar with the OutGlowBitmapEffect.  There is no new class deriving from Effect or ShaderEffect that has a name with OuterGlow in it.

The solution is to use the new DropShadowEffect and set its ShadowDepth to zero.  Presto, we not have an outer glow effect we need.  You can also play around with the BlurRadius property to get the glow size you want.

Here is the best part of all, your outer glow will now be hardware rendered and not software rendered, giving you a nice performance boost. 

You can read about the hardware performance boost in this post GPU-Accelerated Custom Effects for WPF.

<Window x:Class="Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="Window1" Height="300" Width="300">

  <StackPanel>

    <Button Margin="11" Content="OuterGlowBitmpEffect - XAML">
      <Button.BitmapEffect>
        <OuterGlowBitmapEffect GlowColor="Blue" GlowSize="5" />
      </Button.BitmapEffect>
    </Button>

    <Button Margin="11" Content="DropShadowEffect - XAML">
      <Button.Effect>
        <DropShadowEffect ShadowDepth="0" Color="Blue" BlurRadius="10" />
      </Button.Effect>
    </Button>

    <Button Margin="11" Content="OuterGlowBitmpEffect - Code" x:Name="btnOuterGlow" />

    <Button Margin="11" Content="DropShadowEffect - Code" x:Name="btnDropShadow" />

  </StackPanel>

</Window>

The below line of code, Me.btnOuterGlow.BitmapEffect = objOutGlow gets flagged by Visual Studio with the warning message in the below comment.

Below the comment is the code for assigning the new DropShadowEffect to the button in code.  By setting the ShadowDepth to zero and increasing the BlurRadius to ten, you get the same outer glow effect you had with the now obsolete OuterGlowBitmapEffect .

Imports System.Windows.Media.Effects

Class Window1

    Private Sub Window1_Loaded(ByVal sender As Object, _
            ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded

        Dim objOuterGlow As New OuterGlowBitmapEffect
        objOuterGlow.GlowSize = 5
        objOuterGlow.GlowColor = Colors.Red
        Me.btnOuterGlow.BitmapEffect = objOuterGlow

        'Public Property BitmapEffect() As System.Windows.Media.Effects.BitmapEffect
        ' is obsolete.  Avoid using BitmapEffects as they have very poor performance
        'characteristics.  They will be deprecated in a future version.  

        'Consider using the UIElement.Effect property and ShaderEffects where appropriate
        'instead.

        Dim objDropShadow As New DropShadowEffect
        objDropShadow.ShadowDepth = 0
        objDropShadow.BlurRadius = 10
        objDropShadow.Color = Colors.Red
        Me.btnDropShadow.Effect = objDropShadow

    End Sub
End Class

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