The code below adds this shortcode {{ gallery folder="" title=""}}
folder: must be a subdirectory in that Page Bundle. Required. I need to test if this allows multiple galleries in the same page.
Title: used in the initial H4 of the gallery. Optional.
This version is mostly a proof of concept and requires that you install PhotoSwipe, and optionaly Masonry, in your themes/YOURTHEME/static/plugins directory, or /static/plugins for example.
- Photoswipe: https://github.com/dimsemenov/PhotoSwipe
- Masonry: https://masonry.desandro.com/
To do: Define a default value for folder and find a way to load the javascript and css only once per page
Hope it’s useful for someone. 
Example front matter:
---
resources:
- src: "gallery/*.jpg"
name: gallery-:counter
title: gallery-title-:counter
---
Shortcode: gallery.html
<link rel="stylesheet" href="/plugins/photoswipe/photoswipe.css">
<link rel="stylesheet" href="/plugins/photoswipe/default-skin/default-skin.css">
{{ $galleryimages := .Page.Resources.Match (printf "%s-*" (.Get "folder")) }}
<h4 class="title">{{ .Get "title" }}</h4>
<div class="row">
<div class="12u$">
<div class="gallery" itemscope itemtype="http://schema.org/ImageGallery">
{{ range $galleryimages }}
{{ $thumbnail := .Resize "320x" }}
<figure itemscope itemtype="http://schema.org/ImageObject" class="image gallery-item">
<a href="{{ .Permalink }}" itemprop="contentUrl" data-size="{{ .Width }}x{{ .Height }}" >
<img src="{{ $thumbnail.Permalink }}" itemprop="thumbnail" alt="galleryImage" />
</a>
<figcaption itemprop="caption description">
<span itemprop="copyrightHolder"></span>
</figcaption>
</figure>
{{ end }}
</div>
</div>
</div>
<style>
/* Extra Small Devices, Phones */
@media only screen and (min-width : 480px) {
.gallery {
column-count: 1;
column-gap: 3px;
}
}
/* Small Devices, Tablets */
@media only screen and (min-width : 768px) {
.gallery {
column-count: 3;
column-gap: 3px;
}
}
/* Medium Devices, Desktops */
@media only screen and (min-width : 992px) {
.gallery { /* Masonry container */
column-count: 4;
column-gap: 3px;
}
}
/* Large Devices, Wide Screens */
@media only screen and (min-width : 1200px) {
.gallery{
column-count: 4;
column-gap: 3px;
}
}
.gallery-item { /* Masonry bricks or child elements */
background-color: #eee;
display: inline-block;
margin: 0 0 0em;
width: 100%;
}
</style>
<!-- Root element of PhotoSwipe. Must have class pswp. -->
<div class="pswp" tabindex="-1" role="dialog" aria-hidden="true">
<!-- Background of PhotoSwipe.
It's a separate element, as animating opacity is faster than rgba(). -->
<div class="pswp__bg"></div>
<!-- Slides wrapper with overflow:hidden. -->
<div class="pswp__scroll-wrap">
<!-- Container that holds slides.
PhotoSwipe keeps only 3 of them in DOM to save memory.
Don't modify these 3 pswp__item elements, data is added later on. -->
<div class="pswp__container">
<div class="pswp__item"></div>
<div class="pswp__item"></div>
<div class="pswp__item"></div>
</div>
<!-- Default (PhotoSwipeUI_Default) interface on top of sliding area. Can be changed. -->
<div class="pswp__ui pswp__ui--hidden">
<div class="pswp__top-bar">
<!-- Controls are self-explanatory. Order can be changed. -->
<div class="pswp__counter"></div>
<button class="pswp__button pswp__button--close" title="Close (Esc)"></button>
<button class="pswp__button pswp__button--share" title="Share"></button>
<button class="pswp__button pswp__button--fs" title="Toggle fullscreen"></button>
<button class="pswp__button pswp__button--zoom" title="Zoom in/out"></button>
<!-- Preloader demo http://codepen.io/dimsemenov/pen/yyBWoR -->
<!-- element will get class pswp__preloader--active when preloader is running -->
<div class="pswp__preloader">
<div class="pswp__preloader__icn">
<div class="pswp__preloader__cut">
<div class="pswp__preloader__donut"></div>
</div>
</div>
</div>
</div>
<div class="pswp__share-modal pswp__share-modal--hidden pswp__single-tap">
<div class="pswp__share-tooltip"></div>
</div>
<button class="pswp__button pswp__button--arrow--left" title="Previous (arrow left)">
</button>
<button class="pswp__button pswp__button--arrow--right" title="Next (arrow right)">
</button>
<div class="pswp__caption">
<div class="pswp__caption__center"></div>
</div>
</div>
</div>
</div>
<script src="/plugins/photoswipe/photoswipe.min.js"></script>
<script src="/plugins/photoswipe/photoswipe-ui-default.min.js"></script>
<script type="text/javascript">
var initPhotoSwipeFromDOM = function(gallerySelector) {
// parse slide data (url, title, size ...) from DOM elements
// (children of gallerySelector)
var parseThumbnailElements = function(el) {
var thumbElements = el.getElementsByTagName('figure'),
numNodes = thumbElements.length,
items = [],
figureEl,
linkEl,
size,
item;
for(var i = 0; i < numNodes; i++) {
figureEl = thumbElements[i]; // <figure> element
// include only element nodes
if(figureEl.nodeType !== 1) {
continue;
}
linkEl = figureEl.children[0]; // <a> element
size = linkEl.getAttribute('data-size').split('x');
// create slide object
item = {
src: linkEl.getAttribute('href'),
w: parseInt(size[0], 10),
h: parseInt(size[1], 10)
};
if(figureEl.children.length > 1) {
// <figcaption> content
item.title = figureEl.children[1].innerHTML;
}
if(linkEl.children.length > 0) {
// <img> thumbnail element, retrieving thumbnail url
item.msrc = linkEl.children[0].getAttribute('src');
}
item.el = figureEl; // save link to element for getThumbBoundsFn
items.push(item);
}
return items;
};
// find nearest parent element
var closest = function closest(el, fn) {
return el && ( fn(el) ? el : closest(el.parentNode, fn) );
};
// triggers when user clicks on thumbnail
var onThumbnailsClick = function(e) {
e = e || window.event;
e.preventDefault ? e.preventDefault() : e.returnValue = false;
var eTarget = e.target || e.srcElement;
// find root element of slide
var clickedListItem = closest(eTarget, function(el) {
return (el.tagName && el.tagName.toUpperCase() === 'FIGURE');
});
if(!clickedListItem) {
return;
}
// find index of clicked item by looping through all child nodes
// alternatively, you may define index via data- attribute
var clickedGallery = clickedListItem.parentNode,
childNodes = clickedListItem.parentNode.getElementsByTagName('figure'),
numChildNodes = childNodes.length,
nodeIndex = 0,
index;
for (var i = 0; i < numChildNodes; i++) {
if(childNodes[i].nodeType !== 1) {
continue;
}
if(childNodes[i] === clickedListItem) {
index = nodeIndex;
break;
}
nodeIndex++;
}
if(index >= 0) {
// open PhotoSwipe if valid index found
openPhotoSwipe( index, clickedGallery );
}
return false;
};
// parse picture index and gallery index from URL (#&pid=1&gid=2)
var photoswipeParseHash = function() {
var hash = window.location.hash.substring(1),
params = {};
if(hash.length < 5) {
return params;
}
var vars = hash.split('&');
for (var i = 0; i < vars.length; i++) {
if(!vars[i]) {
continue;
}
var pair = vars[i].split('=');
if(pair.length < 2) {
continue;
}
params[pair[0]] = pair[1];
}
if(params.gid) {
params.gid = parseInt(params.gid, 10);
}
if(!params.hasOwnProperty('pid')) {
return params;
}
params.pid = parseInt(params.pid, 10);
return params;
};
var openPhotoSwipe = function(index, galleryElement, disableAnimation) {
var pswpElement = document.querySelectorAll('.pswp')[0],
gallery,
options,
items;
items = parseThumbnailElements(galleryElement);
// define options (if needed)
options = {
index: index,
// define gallery index (for URL)
galleryUID: galleryElement.getAttribute('data-pswp-uid'),
getThumbBoundsFn: function(index) {
// See Options -> getThumbBoundsFn section of documentation for more info
var thumbnail = items[index].el.getElementsByTagName('img')[0], // find thumbnail
pageYScroll = window.pageYOffset || document.documentElement.scrollTop,
rect = thumbnail.getBoundingClientRect();
return {x:rect.left, y:rect.top + pageYScroll, w:rect.width};
}
};
if(disableAnimation) {
options.showAnimationDuration = 0;
}
// Pass data to PhotoSwipe and initialize it
gallery = new PhotoSwipe( pswpElement, PhotoSwipeUI_Default, items, options);
gallery.init();
};
// loop through all gallery elements and bind events
var galleryElements = document.querySelectorAll( gallerySelector );
for(var i = 0, l = galleryElements.length; i < l; i++) {
galleryElements[i].setAttribute('data-pswp-uid', i+1);
galleryElements[i].onclick = onThumbnailsClick;
}
// Parse URL and open gallery if it contains #&pid=3&gid=1
var hashData = photoswipeParseHash();
if(hashData.pid > 0 && hashData.gid > 0) {
openPhotoSwipe( hashData.pid - 1 , galleryElements[ hashData.gid - 1 ], true );
}
};</script>
<script>initPhotoSwipeFromDOM('.gallery');</script>
