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Brightness sample?

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David FranklinBrightness sample?
by on Sep 7, 2010 at 3:04:35 pm

Not sure if this post belongs in the expressions forum, but I'm not looking for help writing the expression itself, just in trying to gather the data that will drive it, so I'm going to post it here.

What I'm trying to do is sample the brightness of a given pixel area on screen, and then use that brightness to adjust the brightness of a separate layer -- kind of like a parenting idea, but with brightness instead of position.

Is there a way to get a numerical value for the grayscale value of a pixel in aftereffects? I'm trying to think of a way to do it, and can't decide if it's really easy and obvious but I'm missing it, or if the reason I can't figure it out is because it's actually hard.

Any thoughts from the group would be much appreciated.
Made With Care In Brooklyn, NY

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Walter SoykaRe: Brightness sample?
by on Sep 7, 2010 at 3:26:16 pm

You want to use sampleImage().

See Dan Ebbert's excellent Obscuration using sampleImage() for a great example might be similar to what you want to do.

Walter Soyka
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David FranklinRe: Brightness sample?
by on Sep 8, 2010 at 12:52:52 am

Thank you. That is indeed exactly what I wanted!
Made With Care In Brooklyn, NY

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