A thumbnail is a small version of an image.

An imagemap is a single image with selectable regions that are associated with URLs.

Imago can be used to create imagemaps from collections of thumbnails such that selectable areas of the imagemap correspond to each thumbnail.

Imago incorporates different layout algorithms for determining the positions of thumbnails within imagemaps.

Imago has been used to create systems for visual bookmarks, visual session summaries, and visual website indexes.

Imago functions as a server, listening for connections and responding to requests from other applications. When a client application requests a thumbnail or imagemap, Imago either returns the image data over the connection or publishes the image with a web server and returns the new URL. Imago also returns information found in the image headers of web images (e.g. width, height, color space, number of colors).

Imago is written in C and has been tested on IRIX 6.5, SunOS 4.1.4, Solaris 5.5, and Windows 98 with the Cygwin dll. Imago uses public-domain C code for encoding and decoding images. Images in the JPG format are handled with the libjpeg software from the Independent JPEG Group. Images in the GIF format are handled with the gd software from boutell.com.

Imago communicates with its clients over sockets through a protocol much like HTTP: messages have ASCII headers (where the first line indicates the request, argument, and version and the last line is blank) with optional ASCII or binary data. Imago's protocol extends HTTP by adding additional requests and header fields for additional arguments.