How to create a control signal from image analysis? (Trigger on layer brigthness)

Is there a way to create a control signal from ISF or image analysis, when for example a layer goes above a certain brightness? How do i create “data” from the visual content of layers, output control data from ISFs?

Background:

My goal is to make collision detect triggers (bangs, midi events) whenever the non-alpha parts of two animated layers interact. I can make an ISF that watches the two layers, and “heatmaps” from black to white whenever and wherever the layers interact.

I have found the Pixel Color Sampler.vuo plugin that kinda works. It watches a single pixel and outputs that value as data which I can then use to trigger external events. My ISF can report the collision detection to this pixel. So I got it working, but without collision location. Its an inelegant solution that feels kinda overly complex, and also for FPS optimisation and project loading I like to avoid running any processing through VUO.

I was wondering if there is a simpler, smarter way using only internal tools?

(I have a faint memory of someone asking something similar a while ago, but couldn’t re-find the thread/answer)