# Rotationally Invariant Digital Fingerprint (RIDF) for Photos of Flat Objects? [RE: Rotationally Invariant Digital Fingerprint (RIDF) for Images?]

```Retitled to: Rotationally Invariant Digital Fingerprint (RIDF) for Photos of Flat Objects?

From: Michael Herman (Trusted Digital Web)
Sent: September 5, 2021 2:23 PM
To: public-credentials (public-credentials@w3.org) <public-credentials@w3.org>
Subject: Rotationally Invariant Digital Fingerprint (RIDF) for Images?

Does anyone have any experience with this or know of a solution for computing an RIDF (rye-diff)?

Problem Statement

1. Alice takes a digital photo Pa of a relatively flat physical object T (e.g. a cracker or a slice of toasted bread)
2. Locally, Alice processes the photo Pa to compute a value RIDF(Pa)
3. Alice sends the physical object T to Bob
4. Bob receives the object T from Alice
5. Bob uses a similar camera to take a digital photo Pb of T ... at a slightly different distance and camera angle than Alice used
6. Bob, local to Bob, using the same software as Alice, processes Pb to compute a value RIDF(Pb)

Question

What kind of algorithm can be used so that RIDF(Pb) is equal, within some sort of standard deviation, to RIDF(Pa)?  Ideally, they're exactly equal to some level of precision.

Some sample images are attached. Assume each cracker is it's own image file. 3 images of each cracker.

Michael Herman

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Received on Sunday, 5 September 2021 22:07:41 UTC