This package uses the Raspberry Camera Module to capture four pictures with a visible countdown. Once captured, all four images are shown for a configurable duration and can be optionally be uploaded to an external web service for post-processing. This server can then return an additional transparent PNG file that will overlay the four photos.

The capture sequence is triggered by GPIO. So you can wire it to a button or other hardware.

A playlist of videos and images is constantly looped while the device is idle.

The photo sequence is triggered by GPIO. Have a look at the GPIO demo package for an example of how to connect a button to GPIO pin 18:

https://info-beamer.com/pkg/8421

If you specify an upload url, the device will upload all four images in a single POST request to the url. In your server code you can then store or otherwise do post-processing on the images. Your service should return a transparent PNG file as a response. This image is then added on top of the four photos. This allows you to augment the output - for example by overlaying a QR code where the user can download their photos.

This package includes an example server in server.py that shows how this works. You might want to use a secret url (instead of /upload) and HTTPS for handling upload requests.