Thanks. Yes compression arteficts always become very visible. Especially in low-detail areas like the sky.

Can you give a specific example? The term “anamorphic encryption” was used in a paper from EUROCRYPT 2022 and I don’t see any prior formal study of the subject. A follow-up paper from PoPETS 2023 establishes that most of the widely-used cryptosystems introduced over the past few decades are indeed capable of anamorphism but nobody used the term “anamorphic encryption” until the last few years.

To say that they have been used for “hundreds” of years seems like a sweeping generalization in need of better context.

Visual anagrams popped up last year using similar, though simpler methods to those in the posted. Flips, internal rotations, rearrangements, color negatives etc. [0]

Diffusion illusions did something similar at about the same time but with puzzles and multi-image color layer mixing. Some of the double puzzles they made are a lot of fun. They have great explainer videos [1] on that site including with Steve Mould.

Also there are diffusion double/hidden images using qrmonster, illusion diffusion, control net, or img2img that have been making the rounds. [2] for a random example. These work by using a fine-tuned diffusion model[3] to take an image and use it as a structuring element at various levels of following to a generated image. To see these illusions, squint or move the screen away. These are quite a bit more popular and easy to make than the other methods so many more examples show up around the internet.

[0] https://dangeng.github.io/visual_anagrams/

[1] https://diffusionillusions.com/

[2] https://www.reddit.com/r/StableDiffusion/s/nm9QMV6roD

[3] or a base model in the case of img2img