java – How to create post-processing effects in Slick2D?

As I get closer to the end of the development of the features of my game and the beginning of the redesign graphic, I still think of ideas of graphic effects that would make my game even better, but Slick2D is so limited in terms of capabilities graphics. . The LWJGL layer is exposed, and thus, the basic OpenGL functions, but I do not know anything about the various merge functions and other functions available.

One of the most basic elements that I must be able to do is to be able to mix primitive images and shapes, and to be able to create an appropriate lighting system. At the moment, I simply have a black and white "stencil" for my flashlight that I mix with a matte black layer that draws everything and sets its opacity so that it looks like a lamp. poached. However, I would like it to be more beautiful and can have other light sources in the scene.

In addition, I would really like to be able to have "glow" effects, such as electricity or fire, that brighten the scene and do not look like flat pixels. Is it as simple as drawing additively these images / shapes on the stage? Or is there more?

I know that Slick2D is horribly obsolete and no longer supported and I should never have used it, but it's definitely the last time I use it. I only went there because Java has limited game libraries and LibGDX gave me a lot of trouble getting started.

I would appreciate all articles and examples.

EDIT: As an example of the "glow effect", here is a nice explosion effect created in Unity that I found on / r / gamedev. It would be great if I could get something like this in my game.

Stylized explosion shader breakdown from gamedev