I know Calibre can remove DRM, but it seems that Calibre does not remove things like watermarks, references to the buyer by name, etc. Now maybe I can try to find those manually, but that is an error prone process. Plus, what if they embed a unique digital signature that ties back to me? I understand that this is a very uncommon practice, but I do not want to find myself in a bad place.
I suppose the only way to remove a digital signature of any sort is to buy two of the same e-book by different people, diff them, and remove anything that differentiates them.
Is there any tool that does this or automates the process? am I being too paranoid, and this is not a real threat?
Pymupdf has options to handle images. Good package.
But then those images could contain the very fingerprints he’s trying to avoid
Theoretically, yes. Handling of images programmatically could allow for some simple lossy compression which would help.
You can mess with the levels to see any hidden watermarks
There are so many ways to encode information into an image without changing its look that I doubt you’ll find most of them by “changing levels”
But what transformations are they stable to?
I’d personally be a lot more likely to blur and add random noise, then use lossy compression if I wanted to mitigate steganography, but even then, they don’t need to encode a lot of information and they have a base image and secrets to compare to. It’s entirely possible for them to have chosen something reasonably robust through random edits like that.