It sounds like you are asking how to create an effect which doesn’t blend two layers together but simply takes the Saturation out of whatever you are applying the effect to. If so, then you can use the the RGB to HSL conversion methods that are included in the effects above (Hue, Saturation, Luminosity, and Color) to do that.

Also, are you using WPF 3.5? If so, you might run into the PS 2.0 shader boundary (number of instructions). If you use WPF 4.0 and take advantage of PS 3.0 … then realize that the software renderer in WPF 4.0 doesn’t handle PS 3.0 shaders (meaning that if the video card doesn’t support PS 3.0 … WPF will do nothing).

Hope that helps.

Hmmm. I could quite easily write that Saturation effect. It
would be kind of a nice effect to disable a control … without making it transparent. Let me know if you want me to give it a whirl.

I have very little experience with HLSL so I’m asking for some assistance in understanding. All of the shaders you provided are good-to-go but I wanted to know if there is a way to control the output of some of them with a 0.0 to 1.0 valued variable. For example, with the saturation effect, it would be nice to have a constant that I can change in .NET from 0 (which gives the normal color saturation), and change it to 1 (which means no color saturation at all).

- Rashad Rivera

Thanks for leaving a comment though! I’m willing to try anything.

Another fellow contacted me via email and said that the differences are a result of Photoshop using a completely different model for computing what it calls hue/saturation/luminosity than what I am using. In this diagram, I am using the bottom middle … and Photoshop is using the bottom right.

If he ever drafts the math to convert back and forth between that HSL model and RGB, I’ll integrate it in … and see if it matches!

In float3 RGBToHSL(float3 color), change the last if statement:

if (hsl.x < 0.0)
{
    // hsl.x += 1.0;
    hsl.x = 0 - hsl.x;
}

I think there was a problem when hue wraps round.

Hope it helps – David