Author: Shaun McCormick (http://www.splittingred.com)
A Gallery system for your photos. Supports albums, items, tagging, and more. Also integrates a custom TV for resizing/cropping/editing of a photo before putting it into a document.
Simply download through Package Management, and install.
For setting up the custom TV, create a TV with Input and Output types of 'galleryitem'.
Please see the official documentation at: http://rtfm.modx.com/display/ADDON/Gallery/