WPF - Control over blending between semi-transparent layers

Answer 1

I believe you you'll have to write a custom shader effect to make WPF blend colors in a different way.

http://msdn.microsoft.com/en-us/library/dd901594%28VS.95%29.aspx Scroll to Creating a Custom Pixel Shader Effect

It's not a trivial thing, I understand. Sometimes it's easier to compromise by using static graphic resources. Our UI designer cannot live with WPF color blending, so some parts of our interface use simple .png files where he absolutely had to have it look a certain way.

Answer 2

What you are looking for is called blend modes if you google it you'll find a lot . Here is a simple example how it can be achieved using pixel shaders. You would use multi-input shader effect for this.

Here is a very good complete tutorial that walks you through creating a reusable library of blend modes using multi-input shader effect.

Blend modes as an intrinsic part of the WPF APIs has been frequently requested since early CTPs but never made it into the product.

Answer 3

Just ran into this question ... but you can use my blend mode library to do this in certain situations (unfortunately there are some limitations ... we really need this capability burned into the WPF API).

bitbonk references the beginning post in my blog series ... but every post has source code and binaries attached for the blend mode library itself.

Here is the series so-far (in chronological order). I do want to write one more post on how these blend modes can be used ... and what value they bring to the table.

• Blend Modes, Part I
• Blend Modes, Part II
• Blend Modes for Silverlight
• Blend Modes, Part III
• Blend Modes: Now Opacity Aware
• Blend Modes: Hue, Saturation, Color, and Luminosity with WPF 4.0

If I could point you to one set of source code/binaries to use, it would be the one where I make the blend mode library opacity aware. This is the latest and greatest bits that work on both WPF and Silverlight. The final post which has the hue, saturation, color, and luminosity effects is a WPF only version of the library, as Pixel Shader 3.0 is required for these effects and currently only WPF 4.0 supports that.

Good luck and let me know if you use my library!