Gets or sets an opacity mask, as a Brush implementation that is applied to any alpha-channel masking for the rendered content of this element. This is a dependency property.
Public Property OpacityMask As Brush
This property only uses whatever the alpha channel value is for the supplied Brush. The other channels of the Brush's rendered content (Red, Green, or Blue) are ignored.
The most typical Brush for this purpose is an ImageBrush, which can be used for a variety of photo masking techniques such as a vignette. But any defined Brush (such as LinearGradientBrush) can be used.
In Extensible Application Markup Language (XAML), this property value can use an inline syntax that is specific to each implementation of the Brush abstract class. For more information, see Painting with Solid Colors and Gradients Overview.
The following markup example shows an ImageBrush opacity mask applied to another Image.
<!-- With the Opacity Mask-->
Supported in: 4.6, 4, 3.5, 3.0
.NET Framework Client Profile
Supported in: 4, 3.5 SP1
Windows 8.1, Windows Server 2012 R2, 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.