Creative Dojo shows how to use the sampleImage() expression in Ae to trigger animations.

VinhSon Nguyen has a new tutorial that shows how you can use the sampleImage() expression in After Effects to read color data in layers. You can then use that data to drive other layers or trigger animations, all dynamically.

“This is just a basic example of what you can do with the sampleImage() expression, and it can be a very powerful method to automate certain animations.” 

While pretty neat, it’s worthwhile to note that sampleImage() is a resource-heavy expression and can slow down After Effects if you’re sampling a lot of pixels.