The Lightbox Gallery is a third party Module for Moodle maintained by Netspot AU and available from https://github.com/netspotau/moodle-mod_lightboxgallery
It is a great way of sharing images with students and uses a “Lightbox” gallery to overlay full size images on screen when you click on a thumbnail view of an image.
Unfortunately the default version of the gallery does not support scaling of images to fit the view-port of the browser so if a lecturer uploads a large mega-pixel image it will not fit the screen and spoils the Lightbox effect.
I have modified the code to now support in browser image resizing. My fork is available at https://github.com/brum1975/moodle-mod_lightboxgallery (a pull request has been sent to Netspot).
To see it in action visit http://matc-online.co.uk/moodle/mod/lightboxgallery/view.php?id=2 where some oversize images have been added to a gallery so you can see it in action.