postpre is a collection of presets for the post-processing library merge-pass.
This live example shows off all the different preset effects. There are sliders that allow you to play with all the parameters, so check it out!
This library provides extra effects and effect loops on top of merge-pass. Copied from the merge-pass readme:
This usage example will show you how to get started with using 2D images such as canvases and videos. This other example shows you how to use this library with only a single WebGL2 rendering context and textures instead of images.
The live example also contains code examples, and is similar to the merge-pass live example which also contains code examples at the bottom.