Dev102.com has a nice post explaining how to write a Brightness extension method.
Excerpt:
Suppose you have several objects in your WPF application filled with similar Brushes which differ in brightness only. Like in this image:
The nine rectangles use the same RadialGradienBrush but each rectangle is a little darker than previous. You can create these 9 different brushes in your favorite design tool (Expression Blend, etc.). But what if you need to change the base color later or you just need to make the brush user-configurable? Like in this sample:
The better approach would be to define the base brush once and then change it’s brightness in code. Unfortunately there’s no built-in way to change brightness of the Brush or Color in WPF. This is what we are going to address in this article.
Link: How to write a Brightness extension method.
