Learning the details of creating an SWI-Prolog HTTP(S) server can be hard as there are often not many examples.
As such in the Wiki post
is the GitHub section
The following list were hand selected for the exceptional quality of the Prolog code.
With regards to what you seek take a look at
GitHub repositories for SWI-Prolog Ludum Dare Teams
If you use the GitHub search for image (search)
you may find what you seek but more importantly many other useful ideas.