The Image Citation Tool: for collaborative image-based scholarship

Christopher W. Blackwell, Neel Smith

Material on this site is based upon work supported by the National Science Foundation under Grants No. IIS-0535003, 0916148, 0916421, and EAGER-1041949. Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation (NSF).


The Image Citation Tool helps create citations to images. Like citations to text, an image-citation can point to a whole image (cp. ‘Homer, Iliad’), or to a specific part of an image (cp. ’Homer, Iliad 2.12). That citation can be ‘resolved’ in different ways.

For example, here is a citation to a high-resolution, full-color digital image of page 12 of the St. Chad Gospel from Lichfield Cathedral: urn:cite:fufolioimg:ChadRGB.Chad012. The citation is in urn format, following the conventions of the cite digital library infrastructure; the image is part of the collection identified as fufolioimg (images for research based at Furman University’s Department of Classics); the image in the group ChadRGB, and the particular image has an ID Chad012. This citation does not depend on the image’s location on a particular server, or the format in which the image is stored; it does not assume a particular scale.

With a citation to a book, you can go to a library, whose staff will let you retrieve the book. Any given library might have the book in hardback, in paperback, or in an electronic edition. With an image-citation, you can retrieve the image from an image-service; like a library, the image-service might offer the image in various formats. The Image Citation Tool is designed to work with images in a particular digital library, whose services can deliver images in particular ways. The tool helps create links that combine three important pieces of information: the citation to the image, the address of the library that has a copy of the image, and the format in which the library will deliver the image. The Image Citation Tool can create two kinds of links for the citation urn:cite:fufolioimg:ChadRGB.Chad012. The first kind delivers a version of whole image as a standard JPG file, which can be saved and used like any image file. The second kind of link leads to a dynamic view of the high-resolution image, which a user can zoom and pan to explore the image in a browser.

An image-citation can be more specific, pointing not to the whole image, but to a region-of-interest (ROI) on an image. This is what the Image Citation Tool is mainly designed to encourage. With the tool, a scholar can identify a rectangular section of an image and create a citation to that image. E.g. the URN of the image (urn:cite:fufolioimg:ChadRGB.Chad012) suffixed by four numbers (0.135,0.19,0.1567,0.0388) representing the left, top, width, and height of the ROI, as percentages of the whole image. This URN identifies a rectangle on the image of Page 12 of the St. Chad Gospel, a rectangle that shows the word ‘bonum’.

The Image Citation Tool lets users draw rectangles on images, automatically generating a URN citation to that region-of-interest, and links that will deliver the ROI as a cropped JPG, or that will show the whole image in dynamic view, with the ROI highlighted.

Using the Image Citation Tool

The The Image Citation Tool supplements the CITE Image Service, which in turn is part of the digital library infrastructure of the Homer Multitext (HMT), a project of the Center for Hellenic Studies of Harvard University. Casey Dué and Mary Ebbott are editors of the HMT; Neel Smith and Christopher Blackwell are its Project Architects. The CITE Infrastructure allows discovery, retrieval, and linking of objects, images, and texts in a networked digital library.

Why to Use the Image Citation Tool

Problem: You are having a conversation by e-mail about a digital image. You want to make a point about a particular feature on the image—a word written on a manuscript page, a leaf on a botanical specimen. How can you easily identify the precise part of the image you are discussing? How can you ‘quote’ from the larger image when making an argument in writing?


How to use the Image Citation Tool

The Image Citation Tool is here.

The Image Citation Tool is a webpage that loads an image and allows users to draw rectangles on it, identifying a region-of-interest (ROI). The page’s Javascript will calculate a region-of-interest based on the currently drawn rectangle and generate a URN citation based on that Image+ROI. The scripts will simultaneously update two links: one that will deliver a cropped JPG showing only the ROI, the other that will deliver a dynamic view of the whole image with the ROI highlighted.

To test the basic functionality, do the following:

By right-clicking on either Test Link - Image Quotation or Test Link - Image Quotation in Context, you can copy the URLs that produce the image-quotations. Those links will work in any web-page, e-mail, or word-processing document.

By copying the URN+ROI, it is possible to perform other actions using the CITE Image Service, but that is beyond the scope of this document. Further documentation of the image service can be found here or here.

How to get Images to Display in the Image Citation Tool

The tool can only work with images provided by the CITE Image Service for which it is configured. The version of the Image Citation Tool on is configured to draw images from the Homer Multitext’s the service at the University of Houston’s Center for High Performance Computing. The service hosts images of medieval and byzantine manuscripts, ancient papyry, and historical botanical specimens.

Any image whose URN is known can be loaded into the Image Citation Tool by adding its URN to the address. By default, the tool’s address is this:

To substitute an image from Mark Catesby’s botanical collections from the 1730s, you can simply replace the value of ‘…urn=…’:

For now, it is easiest to generate a page of links to the Image Citation Tool with different URN values already applied. An example of this is this page of images from William Bartram’s botanical specimens. Each page in the list has a thumbnail (automatically generated from the CITE Image Service), and a link to the Image Citation Tool with the URN of that image included in the address.

Zooming and Sizing the Working Image

The Tool has links that will allow users to make the displayed image larger or smaller. It is also possible to draw a rectangle and crop the visible image to it, allowing ROIs to be created with greater precision. The ROIs generated will be valid regardless of the level of zooming or cropping.

The Image Citation Tool will not allow users to zoom or crop beyond the natural resolution of the original image, since doing so will result in inaccurate ROIs.