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sampleImage returns inaccurate result?

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Jeremy Paul
sampleImage returns inaccurate result?
on Aug 20, 2017 at 9:05:06 pm
Last Edited By Jeremy Paul on Aug 20, 2017 at 9:05:59 pm

I'm playing around and stumbled upon this tutorial that uses greyness of a pixel to determine scale:





To get R value of a pixel it uses sampleImage() method. It samples the central point of a layer. I found it strange that even though the central point is still 100% black, scaling of a shape layer already occurred. Check this image at

t=9m26s

for example.


The expression in question:

sampleSize = [1,1];
samplePoint = thisComp.layer("Control Layer").transform.position; // it is [960,540]
sampleColor = thisComp.layer("Control Layer").sampleImage(sampleSize,samplePoint)[0];

[sampleColor*100,sampleColor*100];


What am I missing here?


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Leopoldo Perizzolo
Re: sampleImage returns inaccurate result?
on Aug 26, 2017 at 2:57:20 pm

You simply switched the two arguments of the expression in sampleImage (just like the video did..)
It should be:

sampleImage(position, radius), and in your case:

sampleColor = thisComp.layer("Control Layer").sampleImage(samplePoint, sampleSize)[0];

Hope it's all clear.

Leopy


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