I don't really know what to call them, but the filters most commonly used by mobile photo and video apps, which are part of post-processing. I'm not a big fan of them but I'm curious as to how they work. Do they use the lighting and colour settings the app provides and can be manually created or they involve other photography effects?
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The answer is a little complex.
I'm hotlinking an image from this site: https://filterforge.com/features/version4/groups-and-instancing.html That is a good program to make your own filters.
The idea is that you have a basic set of basic "nodes". For example one can be a blur, another one that modifies the saturation and another one that controls contrast.
Then, for a specific filter you can add them as steps, handling the amount of each one.
There a lot of this basic nodes. Ones can inclusive add information from another source. For example one filter that adds a paper texture to a photo, could gather the data from a grayscale image of that texture.
Another kind of textures can be procedural. This are textures generated by the computer. For example a cloud texture can have parameters on how much cloud or sky proportion you need or the color of the sky.
Depending on your settings this procedurals can generate a entire new image or just add an effect to a photo.
Some of this nodes can modify the values of each individual pixel, and some others need to take in account adjacent pixels.