A Proposed Extension to HTML : Client-Side Image Maps
RFC 1980
Document | Type |
RFC - Historic
(August 1996; No errata)
Obsoleted by RFC 2854
Was draft-seidman-clientsideimagemap (individual)
|
|
---|---|---|---|
Author | James Seidman | ||
Last updated | 2015-07-21 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1980 (Historic) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group J. Seidman Request for Comments: 1980 Spyglass, Inc. Category: Informational August 1996 A Proposed Extension to HTML : Client-Side Image Maps Status of this Memo This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Abstract The markup language known as "HTML/2.0" provides for image maps. Image maps are document elements which allow clicking different areas of an image to reference different network resources, as specified by Uniform Identifier (URIs). The image map capability in HTML/2.0 is limited in several ways, such as the restriction that it only works with documents served via the "HTTP" protocol, and the lack of a viable fallback for users of text-only browsers. This document specifies an extension to the HTML language, referred to as "Client- Side Image Maps," which resolves these limitations. Table of Contents 1. Introduction ............................................... 1 1.1 Purpose ............................................... 1 1.2 Overall Operation ..................................... 2 2. Client-Side Image Map Extension ............................ 2 2.1 Syntax ................................................ 2 2.2 Required Changes to HTML/2.0 DTD ...................... 4 2.3 Backwards Compatibility ............................... 5 2.4 Examples .............................................. 5 3. Security Considerations .................................... 6 4. References ................................................. 6 5. Author's Address ........................................... 7 1. Introduction 1.1 Purpose Image maps are an important feature of the point-and-click interface which makes the World Wide Web so popular. The most common use of image maps is to allow users to access different documents by clicking different areas in an image. Seidman Informational [Page 1] RFC 1980 Client-Side Image Maps August 1996 There are several limitations of the current image map implementation as it applies to this use. First, it only works over the HTTP protocol, making it unusable for reading local files or files accessed via alternate protocols. Second, a server transaction is required merely to determine where the link is directed. This can degrade performance noticeably when accessing distant sites. Third, unlike for normal links, there is no way for a browser to provide visual feedback to the user showing where a portion of an image map leads before the user actually clicks it. Lastly, the method for specifying the active regions of image maps is server-dependent, compromising portability of documents. This extension to support client-side image maps addresses these issues. It is proposed that this extension be included in a future revision of the HTML specification. 1.2 Overall Operation Client-side image maps work by placing a complete representation of the active areas of an image, including their shape, size, and destination (URI), into an SGML-compliant textual form. This markup may also optionally include a textual description for each area for display on non-textual browsers. This representation, or "map," is given a name to identify it. When an image is included in an HTML document, it may include an attribute specifying a map to use. The map may be contained in the same file which references the image, but this it not required. If the map is in a different file, a URI to that file must be provided. The browser will parse the map and remember the contents. When the user clicks the map, the browser will match up the location with the specified destination for that location and access that URI. In the case of a non-graphical browser, the browser could display the textual descriptions for each area instead of the image. Clicking a given textual description would then go to the associated destination. 2. Client-Side Image Map Extension 2.1 Syntax Adding a USEMAP attribute to an IMG element indicates that it is a client-side image map. The USEMAP attribute can be used with the ISMAP attribute to indicate that the image can be processed as either a client-side or server-side image map. The argument to USEMAP specifies which map to use with the image, by specifying the URI for the file containing the map, followed by a '#', followed by the name Seidman Informational [Page 2] RFC 1980 Client-Side Image Maps August 1996Show full document text