OpenSeadragon is a javascript library for displaying tiling images. This gem packages those assets and some Rails helpers for using them.

http://openseadragon.github.io/

Add the gem to your Gemfile:

gem 'openseadragon'

Run bundle install:

$ bundle install

And run the openseadragon-rails install generator:

$ bundle exec rails g openseadragon:install

The generator will install the Rails helpers and openseadragon assets.

This gem provides two helpers, #picture_tag and #openseadragon_picture_tag.

The #picture_tag helper creates HTML5 tags.

In the simple case, a view like:

picture_tag 'page1.jpg', 'page2.jpg', 'page3.jpg'

Creates the HTML like:

<picture>
  <source src="page1.jpg" />
  <source src="page2.jpg" />
  <source src="page3.jpg" />
</picture>

You can control the attributes on <picture> and <source> elements:

picture_tag ['page1.jpg' => { id: 'first-picture'}], 'page2.jpg', 'page3.jpg', { class: "picture-image" }, { id: 'my-picture'}

<picture id="my-picture">
  <source class="picture-image" id="first-picture" src="page1.jpg">
  <source class="picture-image" src="page2.jpg">
  <source class="picture-image" src="page3.jpg">
</picture>

If you have an OpenSeaDragon tilesource, you can use this helper to construct a HTML5 <picture> that will render as an OpenSeaDragon tile viewer.

openseadragon_picture_tag 'page1.jpg'

<picture data-openseadragon="true">
  <source media="openseadragon" src="page1.jpg" />
</picture>

This gem includes some javascript that translates that markup to the OSD viewer.

As with #picture_tag, you can provide additional options.

openseadragon_picture_tag 'page1.jpg', 'path/to/info.json', ['some-custom-tilesource' => { Image: {  xmlns: "...", Url: '...', Format: 'jpg', Overlap: 2}}], { class: 'osd-image'}, { data: { openseadragon: { preserveViewport: true, visibilityRatio: 1}}}

<picture data-openseadragon="{&quot;preserveViewport&quot;:true,&quot;visibilityRatio&quot;:1}">
    <source class="osd-image" media="openseadragon" src="page1.jpg" />
    <source class="osd-image" media="openseadragon" src="path/to/info.json" />
    <source class="osd-image" data-openseadragon="{&quot;Image&quot;:{&quot;xmlns&quot;:&quot;...&quot;,&quot;Url&quot;:&quot;...&quot;,&quot;Format&quot;:&quot;jpg&quot;,&quot;Overlap&quot;:2}}" media="openseadragon" src="some-custom-tilesource" />
</picture>

The src attribute (or the JSON-encoded options given in the data-openseadragon) are translated into an OpenSeaDragon tilesource configuration.