The IMAGE-MAP export-type exists to allow well abstracted use of clickable image formats currently supported on CERN and NCSA servers. An image-map is both an image and a searchable object. Using a configuration file called a map file, areas of an image are specified to point to different URLS, either on the local host or at a remote site. When the client returns the coordinates of a user's mouse click, the server compares that data to the information supplied in the map file. The server then returns either the contents of a local URL or a redirect to a URL on a remote host. CL-HTTP parses the map file into a data structure at export time, so the information is already in memory when a user responds to an image-map. To allow compatability with existing files and graphics tools, either the CERN or the NCSA format for map files can be specified.
Image-maps are usually made up of basic shapes (eg. toolbars) but can contain concave polygons and layered shapes. They are often used as directories or indexes, providing a clear, graphical way to organize a group of links. While CL-HTTP supports GIF, JPEG, X-BITMAP, PICT, and TIFF searchable image types, only GIF is supported by most browsers. While some browsers will inline JPEG files, many launch an external application and cannot use the file for image-map purposes.
Christopher R. Vincent -- Christopher_Vincent@nospam.alum.mit.edu