Is there something like sampleImage() for a Comp?

Hi everyone,

I couldn't find any reference for this -

Can I check the alpha value of a comp pixel and not a layer pixel (similar to a layer's sampleImage() method)?

AEScripts.com and various other places have scripts like these:

Auto Crop - aescripts + aeplugins - aescripts.com

pt_CropPrecomps - aescripts + aeplugins - aescripts.com 

How do the various auto crop scripts know where the comp's layers transparency is in order to crop it to the layers' actual size?

I don't necessarily want to crop a comp - just get the alpha values of a comp in a script... or whatever method those auto-crop scripts use.

Thanks a lot in advance,

Roy