Store and display high resolution images with the International Image Interoperability Framework (IIIF)

Recently a faculty member working in the Digital Humanities on my campus asked the library to explore International Image Interoperability Framework (IIIF) image servers, with the ultimate goal of determining whether it would be feasible for the library to support a IIIF server as a service for the campus.  I typically am not very involved in supporting work in the Digital Humanities on my campus, despite my background in (and love for) the humanities (philosophy majors, unite!). Since I began investigating this technology, I seem to see references to IIIF-compliance popping up all over the place, mostly in discussions related to IIIF compatibility in Digital Asset Management System (DAMS) repositories like Hydra ¹ and Rosetta ², but also including ArtStor³ and the Internet Archive ⁴.

IIIF was created by a group of technologists from Stanford, the British Library, and Oxford to solve three problems: 1) slow loading of high resolution images in the browser, 2) high variation of user experience across image display platforms, requiring users to learn new controls and navigation for different image sites, and 3) the complexity of setting up high performance image servers.⁵ Image servers traditionally have also tended to silo content, coupling back-end storage with either customized or commercial systems that do not allow additional 3rd party applications to access the stored data.

By storing your images in a way that multiple applications can access them and render them, you enable users to discover your content through a variety of different portals. With IIIF, images can be stored in a way that facilitates API access to them. This enables a variety of applications to retrieve the data. For example, if you have images stored in a IIIF-compatible server, you could have multiple front-end discovery platforms access the images through API, either at your own institution or other institutions that would be interested in providing gateways to your content. You might have images that are relevant to multiple repositories or collections; for instance, you might want your images to be discoverable through your institutional repository, discovery system, and digital archives system.

IIIF systems are designed to work with two components: an image server (such as the Python-based Loris application)⁶ and a front-end viewer (such as Mirador ⁷ or OpenSeadragon⁸).  There are other viewer options out there (IIIF Viewer ⁹, for example), and you could conceivably write your own viewer application, or write a IIIF display plugin that can retrieve images from IIIF servers.  Your image server can serve up images via APIs (discussed below) to any IIIF-compatible front-end viewer, and any IIIF-compatible front-end viewer can be configured to access information served by any IIIF-compatible image server.

IIIF Image API and Presentation API

IIIF-compatible software enables retrieval of content from two APIs: the Image API and the Presentation API. As you might expect, the Image API is designed to enable the retrieval of actual images. Supported file types depends on the image server application being used, but API calls enable the retrieval of specific file type extensions including .jpg, .tif, .png, .gif, .jp2, .pdf, and .webp.¹⁰. A key feature of the API is the ability to request images to be returned by image region – meaning that if only a portion of the image is requested, the image server can return precisely the area of the image requested.¹¹ This enables faster, more nimble rendering of detailed image regions in the viewer.

The basic structure of a request to a IIIF image server follows a standard scheme:

{scheme}://{server}{/prefix}/{identifier}/{region}/{size}/{rotation}/{quality}.{format}

An example request to a IIIF image server might look like this:

http://www.example.org/imageservice/abcd1234/full/full/0/default.jpg¹²

The Presentation API returns contextual and descriptive information about images, such as how an image fits in with a collection or compound object, or annotations and properties to help the viewer understand the origin of the image. The Presentation API retrieves metadata stored as “manifests” that are often expressed as JSON for Linked Data, or JSON-LD.¹³ Image servers such as Loris may only provide the ability to work with the Image API; Presentation API data and metadata can be stored on any server and image viewers such as Mirador can be configured to retrieve presentation API data.¹⁴

Why would you need a IIIF Image Server or Viewer?

IIIF servers and their APIs are particularly suited for use by cultural heritage organizations. The ability to use APIs to render high resolution images in the browser efficiently is essential for collections like medieval manuscripts that have very fine details that lower-quality image rendering might obscure. Digital humanities, art, and history scholars who need access to high quality images for their research would be able to zoom, pan and analyze images very closely.  This sort of an analysis can also facilitate collaborative editing of metadata – for example, a separate viewing client could be set up specifically to enable scholars to add metadata, annotations, or translations to documents without necessarily publishing the enhanced data to other repositories.

Example: Biblissima

A nice example of the power of the IIIF Framework is with the Biblissima Mirador demo site. As the project website describes it,

In this demo, the user can consult a number of manuscripts, held by different institutions, in the same interface. In particular, there are several manuscripts from Stanford and Yale, as well as the first example from Gallica and served by Biblissima (BnF Français 1728)….

It is important to note that the images displayed in the viewer do not leave their original repositories; this is one of the fundamental principles of the IIIF initiative. All data (images and associated metadata) remain in their respective repositories and the institutions responsible for them maintain full control over what they choose to share. ¹⁵.

The approach described by Biblissima represents the increasing shift toward designing repositories to guide users toward linked or related information that may not be actually held by the repository.  While I can certainly anticipate some problems with this approach for some archival collections – injecting objects from other collections might skew the authentic representation of some collections, even if the objects are directly related to each other – this approach might work well to help represent provenance for collections that have been broken up across multiple institutions. Without this kind of architecture, researchers would have to visit and keep track of multiple repositories that contain similar collections or associated objects. Manuscript collections are particularly suited to this kind approach, where a single manuscript may have been separated into individual leaves that can be found in multiple institutions worldwide – these manuscripts can be digitally re-assembled without requiring institutions to transfer copies of files to multiple repositories.

One challenge we are running into in exploring IIIF is how to incorporate this technology into existing legacy applications that host high resolution images (for example, ContentDM and DSpace).  We wouldn’t necessarily want to build a separate IIIF image server – it would be ideal if we could continue storing our high res images on our existing repositories and pull them together with a IIIF viewer such as Loris).  There is a Python-based translator to enable ContentDM to serve up images using the IIIF standard¹⁶, but I’ve found it difficult to find case studies or step-by-step implementation and troubleshooting information (if you have set up IIIF with ContentDM, I’d love to know about your experience!).  To my knowledge, there is not an existing way to integrate IIIF with DSpace (but again, I would love to stand corrected if there is something out there).  Because IIIF is such a new standard, and legacy applications were not necessarily built to enable this kind of content distribution, it may be some time before legacy digital asset management applications integrate IIIF easily and seamlessly.  Apart from these applications serving up content for use with IIIF viewers, embedding IIIF viewer capabilities into existing applications would be another challenge.

Finally, another challenge is discovering IIIF repositories from which to pull images and content.  Libraries looking to explore supporting IIIF viewers will certainly need to collaborate with content experts, such as archivists, historians, digital humanities and/or art scholars, who may be familiar with external repositories and sources of IIIF content that would be relevant to building coherent collections for IIIF viewers.  Viewers are manually configured to pull in content from repositories, and so any library wanting to support a IIIF viewer will need to locate sources of content and configure the viewer to pull in that content.

Undertaking support for IIIF servers and viewers is fundamentally not a trivial project, but can be a way for libraries to potentially expand the visibility and findability of their own high-resolution digital collections (by exposing content through a IIIF-compatible server) or enable their users to find content related to their collections (by supporting a IIIF viewer).  While my library hasn’t determined what exactly our role will be in supporting IIIF technology, we will definitely be taking information learned from this experiences to shape our exploration of emerging digital asset management systems, such as Hydra and Islandora.

More Information

• IIIF Website: http://search.iiif.io/
• IIIF Metadata Overview: https://lib.stanford.edu/home/iiif-metadata-overview
• IIIF Google Group: https://groups.google.com/forum/#!forum/iiif-discuss

Notes