Identification/recognition of the printed image?

Question

OpenCV

Good afternoon.
I will briefly outline why such a question arose and what is needed:
There is a production facility, Glory to the CPSU, orders are coming in.
There is a roll printing line.
The first problem starts with the fact that printing is streaming from a "roll" and sending to print is done by several monkeys. Those. sheets from different orders are mixed in sequence on a roll. (The order of printing can be set, but there are orders that take 3 days to print, and there are orders that take 1 minute to print)
After printing, the roll goes to cutting, where directly finished images are cut out of it.
Naturally, all cut out pictures fall into one container (Do not change - features of the cut technology).
This is where the main problem begins.
As you understand, then you need to sort out which picture is in which order.
At the moment, I made it possible to automatically feed each cut out picture under the camera.
The question remains - how to identify a picture that it belongs to a particular order?
I tried the Haar cascade - 70% and very slowly.
I think, maybe there is some way to introduce some kind of identifier on the image itself before printing, which could be recognized by the camera, but which would not be visible to the human eye in the finished image?

Answer 1

Almost solved with Digimarc for images. Sorry, but paid.
Read after printing. Minor problems with brightness and scaling.
I will do it in a similar way - change the brightness of some areas.
Something like a QR code.