Masking techniques for greenscreen

jrs's picture

Hi All,

Can someone suggest the best way to mask out a green screen? I've tried using the NI mask from colour patch along with a blur but I'm still getting some green pixels.

Is it possible to write a core image filter that measure the distance between colors and uses that to compute the alpha? if so does anyone know the distance function?

Cheers James

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MaskTest2.qtz75.6 KB
Screen shot 2011-08-01 at 3.48.15 PM.png
Screen shot 2011-08-01 at 3.48.15 PM.png210.83 KB

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jersmi's picture
Re: Masking techniques for greenscreen

Here are two of the CI filter solutions floating around. There's at least one more I can think of -- google "daisyrust chroma".

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Chroma key +BW.qtz42.98 KB
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dust's picture
Re: Masking techniques for greenscreen

you can use this color key and background subtraction example to key out your green screen. with just background subtraction on normal white wall there is no need to use the color subtraction. you can use multiple color keys if you don't have a background photo. try this experiment with blurs and filters, image controls on background mask. i think you will find a combination that should mask out green screens.

http://kineme.net/composition/dust/clcolorandbackgroundimagekeying

would love to see some comparison results type of things. once this is set up right there isn't any fussing about trying to get rid of shadow and garbage masking things out like you normally have to do. ;)