Learning more about image handling

Hey,

I want to learn a bit more on how wordpress handles images. In detail on a code level. I want to know exactly what image sizes are stored, how to setup e.g. a CPT field to store one image of a specific size using the crop tool.

I found the documentation on e.g. wp.media a bit lacking.

Does anyone know a book, course, video or other resource that go in-depth on this topic?