Gallery Plugins for Joomla
Many business and organization web sites need to display galleries of photos or figures with the capability to provide or restrict user’s ability to download images. There are many free and fee extensions available for Joomla but two are particularly convenient if you work with Adobe Lightroom or load your images via scp or ftp. The sections that follow discuss two alternatives that use inline syntax within an article to specify a gallery. These are not good choices if you need to take payment for images, but can work for many web sites.
The examples here are taken from a family history web site where images of court probate records are displayed so that site users need not visit a courthouse and potentially damage fragile court records.
Note that many image gallery extensions use a lot of Javascript and CSS; minification, compression, consolidation and caching extensions can cause problems with some options. Make sure to turn off your performance software while you are debugging gallery problems.
Neither of these tools will add images to a site map that you can register with Google; you will need to generate a static site map or use another extension. Similarly, neither of these extensions will put an index.html file in the image directories to prevent an attacker from doing a directory scan of your media folders.
Simple Image Gallery by JoomlaWorks
Simple Image Gallery provides an easy way to make a gallery from an entire directory of images using simple syntax: {gallery}image_directory{/gallery}. It does not have any way to control downloads, and only allows fixed thumbnail sizes or other gallery characteristics–unless you upgrade to Simple Image Gallery Pro.
The free version of this product does not get frequent updates and was broken for a while in the fall of 2017, but was updated to run on Joomla 3.8.
Sigplus by Levente Hunyadi
Sigplus uses identical syntax to Simple Image Gallery, and appears to be a fork of the GPL code in Simple Image Gallery. It uses identical {gallery}image_directory{/gallery} syntax for including a gallery in an article. Sigplus offers much more customization than Simple Image Gallery–especially the ability to fit thumbnails into a bounding box while preserving the aspect ratio. It also allows you to specify a gallery subdirectory for thumbnails and previews, so you can pre-render the images using some other tool. This option also amounts to a permanent cache, so that lightly-used sites have better response times for large galleries.
Sigplus has a search plugin that allows you to search the website for image metadata; for the family history website used in this example, this makes images searchable by surname, location or other tags put into the metadata before exporting from Lightroom. For a community organization web site, this would allow someone to find all photos of themselves if the photos were tagged before export from Lightroom.
Sigplus has a module that gives you a way to incorporate a gallery as part of site design rather than just within an article.
Sigplus is a good alternative if you need more functionality than Simple Image Gallery but do not have the budget for the Simple Image Gallery Pro.
Image Indexing and Site Maps
Both of these extensions use Javascript to manage the image display, so when a robot crawls the page, the image generally will not be indexed by crawling the page. For many uses of a gallery extension, this is the behavior that you want.
If this is not what you want, you will need to create a site map and submit it to the search engines along with your other site maps. Since these plugins do not work with most (if any) Joomla site map extensions, you will need to use another utility to generate site maps of these images if you want Google to index them. If you have shell access to your server, this XML PHP script looks like a good free alternative, though it does not recursively search directories beyond the first level unless you make some changes to the script. If you have PERL installed on your web server, the Google Site Map Generator may work too.