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Silverlight Pixel Shader Effect that does a chroma key transparency with tolerances. This will allow transparent video effects (green screen) in Silverlight 3 and Silverlight 4.


Chroma Keying is a standard technique in videography where a subject is shot in front of a solid color background (like a green screen) and then that footage is superimposed over other video or graphcs to simulate the coincidence of visual elements that aren't physically adjacent. The Pixel Shader functionality in Silverlight 3, Silverlight 4, and WPF make it possible to easily perform this type of compositing using a Chroma Key Effect that turns any pixels of a specifc color to transparent (with a tolerance value). This effect is based on the Color Key Alpha Effect from the WPF Pixel Shader Library.



1. Once you install the Synergist Effect library on your system, you should see the ChromaKeyAlphaEffect in the Effects pane of the Expression Blend Asset Library:
2. Drag the effect onto a MediaElement that has a Chroma Key
3. Modify the ColorKey and Tolerance properties of the Effect to suite the color used in the Key.
4. Use element ordering or ZIndex to place the chroma keyed Media Element in front of other video elements that will serve as its background.
5. In the downloadable Demo, the field shows through the blue background (the Color Key) with 27% tolerance. You can see this demo here (Requires Silverlight 3) here).
Last edited Aug 4 2010 at 5:46 PM  by mscherotter, version 12
MeanMrW wrote  Jan 24 2013 at 11:09 PM  
Great plugin - thanks for sharing. Easy install and good results. If only you could feather the edges, too... Then it would be PERFECT!

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