Gets or sets the degree of opacity of a Brush.
Assembly: PresentationCore (in PresentationCore.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
A value of 0 indicates that the brush is completely transparent, while a value of 1 indicates that the brush is completely opaque. A value of 0.5 indicates the brush is 50% opaque, a value of 0.725 indicates the brush is 72.5% opaque, and so on. Values less than 0 are treated as 0, while values greater than 1 are treated as 1.
This example shows how to make a UIElement transparent or semi-transparent. To make an element transparent or semi-transparent, you set its Opacity property. A value of 0.0 makes the element completely transparent, while a value of 1.0 makes the element completely opaque. A value of 0.5 makes the element 50% opaque, and so on. An element's Opacity is set to 1.0 by default.
The following example sets the Opacity of a button to 0.25, making it and its contents (in this case, the button's text) 25% opaque.
<!-- The image contained within this button has an effective opacity of 0.125 (0.25 * 0.5 = 0.125). --> <Button Opacity="0.25"> <StackPanel Orientation="Horizontal"> <TextBlock VerticalAlignment="Center" Margin="10">A Button</TextBlock> <Image Source="sampleImages\berries.jpg" Width="50" Height="50" Opacity="0.5"/> </StackPanel> </Button>
' ' The image contained within this button has an ' effective opacity of 0.125 (0.25*0.5 = 0.125) ' Dim myImageButton As New Button() myImageButton.Opacity = New Double() myImageButton.Opacity = 0.25 Dim myImageStackPanel As New StackPanel() myImageStackPanel.Orientation = Orientation.Horizontal Dim myTextBlock As New TextBlock() myTextBlock.VerticalAlignment = VerticalAlignment.Center myTextBlock.Margin = New Thickness(10) myTextBlock.Text = "A Button" myImageStackPanel.Children.Add(myTextBlock) Dim myImage As New Image() Dim myBitmapImage As New BitmapImage() myBitmapImage.BeginInit() myBitmapImage.UriSource = New Uri("sampleImages/berries.jpg",UriKind.Relative) myBitmapImage.EndInit() myImage.Source = myBitmapImage Dim myImageBrush As New ImageBrush(myBitmapImage) myImage.Width = 50 myImage.Height = 50 myImage.Opacity = 0.5 myImageStackPanel.Children.Add(myImage) myImageButton.Content = myImageStackPanel
Another way to control the opacity of an element is to set the opacity of the Brush that paints the element. This approach enables you to selectively alter the opacity of portions of an element, and provides performance benefits over using the element's Opacity property. The following example sets the of a SolidColorBrush used to paint the button's Background is set to 0.25. As a result, the brush's background is 25% opaque, but its contents (the button's text) remain 100% opaque.
' ' This button's background is made 25% opaque, ' but its text remains 100% opaque. ' Dim myOpaqueTextButton As New Button() Dim mySolidColorBrush As New SolidColorBrush(Colors.Gray) mySolidColorBrush.Opacity = 0.25 myOpaqueTextButton.Background = mySolidColorBrush myOpaqueTextButton.Content = "A Button"
You may also control the opacity of individual colors within a brush. For more information about colors and brushes, see Painting with Solid Colors and Gradients Overview. For an example showing how to animate an element's opacity, see How to: Animate the Opacity of an Element or Brush.
|How to: Animate the Opacity of an Element or Brush||To make a framework element fade in and out of view, you can animate its Opacity property or you can animate the property of the Brush (or brushes) used to paint it. Animating the element's opacity makes it and its children fade in and out of view, but animating the brush used to paint the element enables you to be more selective about which portion of the element fades. For example, you could animate the opacity of a brush used to paint a button's background. This would cause the button's background to fade in and out of view, while leaving its text fully opaque.|
|How to: Animate the Color or Opacity of a SolidColorBrush||This example shows how to animate the Color and of a SolidColorBrush.|
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.