And then I see this in the ExecPlan for my latest refactor:
---
# Observations
- Observation: The refactor made the screenshots pixel-identical after the baseline was recaptured correctly.
Evidence: sha256sum screenshots/before-implementation-x.png screenshots/after-implementation-x.png reported matching hashes for before/after pairs 1, 2, and 3.
---
Which is crazy! I've never told Codex to do an sha compare on before/after screenshots of the app, but I do have instructions in my PLANS.md to take before & after screenshots of the webapp for the game to make sure we avoid frontend regressions (it uses GPT-Image-2 for analysis). So for non-frontend impacting changes, of course nothing should be different between screenshots taken at identical timestamps into the game start.
But doing an explicit SHA compare - that's just...not something I would've ever thought of. Wild.
TacticalCoder•1h ago
If I'm not mistaken SGI (Silicon Graphics, Inc.) was already doing that to prevent regression 40 years ago: maybe not SHA but they were taking "screenshots" of the entire screen at a time t and some kind of checksum to then verify (without having to compare every single pixel in the happy case) that enhancement/optimization to their rendering pipeline not supposed to change the output indeed did indeed generate the exact same image as before.
It's basically a 40 years old technique: not too sure what's that wild about it.
ditchfieldcaleb•1h ago
Edit: I'm not saying no one does checksums to compare files (lol). I'm saying no one takes screenshots at specific timestamps within an app or game's lifecycle and then compares them to ensure they're identical.
kay_o•1h ago
Everyone does this to match files as identical, be it sha, md5, or something else. I cannot imagine any other method such that it would first come to mind easily you would be doing to check if two files are the same.
I don't mean to offend but I quite literally mean everyone does this. Every software updater, game patcher, checking if two binary files are identical (pixel perfect/lossless in this case: BMP, PNG created by same encoder off same inputs would qualify, JPG would likely not), all of them do exactly this.
GPT-Analysis or a similarity and image chunk hashing would not be the first thing you turn to if what you wanted was exact identical pixel perfect. I am curious what your background is if this is the case.
ditchfieldcaleb•9m ago
No one takes automated screenshots of webapps or games or what have you at pre-determined timestamps to make sure the app looks identical with every change.
(regardless of the method; the SHA'ing isn't the point here, the point is that it's a shortcut instead of "inspect the image for any regressions", since we don't need to inspect the image at all if it is identical)
tomjakubowski•1h ago
ditchfieldcaleb•8m ago