Thursday, December 27, 2007


In the Ur-web of the early 1990s, images came in fixed sizes. You might get a thumbnail-sized image, a smaller version or a larger version, but generally what appeared in your browser was a full, one-to-one view of a distinct image as it was delivered to you from a Web server.

Today, it's increasingly common for server- and client-side applications to manipulate what is, at least notionally, a single image that a user can navigate through. Google defined the current state of the art in browser-based image navigation when it introduced Google Maps in 2005. Its clever use of AJAX to load adjacent tiles at appropriate scales creates the illusion of continuous navigation of the whole earth.

The same technology can be applied to any image. At University College, London, the Centre for Advanced Spatial Analysis has developed "The Google Maps Image Cutter," an application to generate from any digital image the image tiles required by a Google maps-style web application.

A couple of projects I'm working on apply this technique to browse images that cannot be displayed in full detail in a single view because of their high resolution or awkward shape. The Center for Hellenic Studies' Homer Multitext Project has Google-mapped high-resolution photographs of Iliadic manuscripts. I've recently Google-mapped drawings and photographs of several dozen inscriptions in the Lycian language.

This is an easily implemented and effective way to let users explore an image. It comes at the cost of one tiny little white lie: we have to pretend to Google that the coordinate space of our rectangular image works like a Mercator projection of a spheroid (the earth).

This is innocent enough, if we recognize what we're doing, but it should provoke more serious reflection about how we use images and cite them in scholarly work. We need to define recognizable ways of referring to parts of an image independently of the state of a user's panning and zooming. I'll post more on that topic before long. For now, enjoy the pictures.

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