Class CommonFilters implements certain common image
postprocessing filters.
It is not ideal that these filters are all included in a single
monolithic module. Unfortunately, when you want to apply two filters
at the same time, you have to compose them into a single shader, and
the composition process isn't simply a question of concatenating them:
you have to somehow make them work together. I suspect that there
exists some fairly simple framework that would make this automatable.
However, until I write some more filters myself, I won't know what
that framework is. Until then, I'll settle for this
clunky approach. - Josh