Render photos individually, optimize gallery images, and prune old releases

_plugins/gallery_items.rb

@@ -0,0 +1,24 @@
+require 'nokogiri'
+
+module GalleryItems
+  # Uploaded batches share one source document, but each photo is a gallery item.
+  # Keeping this at render time also fixes batches that have already been published.
+  def gallery_items(content)
+    fragment = Nokogiri::HTML::DocumentFragment.parse(content)
+    images = fragment.css('img')
+    return [content] unless images.length > 1 && images.all? { |image|
+      image['src'].to_s.start_with?('/img/arts/uploads/') && image.parent.name == 'p'
+    }
+
+    captions = fragment.css('.image-details').map(&:to_html).join
+    images.each { |image| image.parent.remove }
+    fragment.css('.image-details').each(&:remove)
+    # Preserve the batch's existing anchor exactly once, before the first photo.
+    prefix = fragment.to_html
+    images.each_with_index.map do |image, index|
+      "#{index.zero? ? prefix : ''}<p>#{image.to_html}</p>#{captions}"
+    end
+  end
+end
+
+Liquid::Template.register_filter(GalleryItems)