I'm sure the comment you're replying to wasn't thinking of the algorithm that applies a filter to a jpeg, but the process by which that filter is created in the

I'm sure the comment you're replying to wasn't thinking of the algorithm that applies a filter to a jpeg, but the process by which that filter is created in the first place. The assumption being that there's some sort of theory to colour that allows you to systematically improve the aesthetic qualities of images. As an analogy, think of the value music theory (i. e. https://en.wikipedia.org/wiki/Scale_(music)#Harmonic_content https://en.wikipedia.org/wiki/Scale_(music)#Harmonic_content) for composition.