In HTML and XHTML , an image map is a list of coordinates relating to a specific image, created in order to hyperlink areas of the image to various destinations (as opposed to a normal image link, in which the entire area of the image links to a single destination). For example, a map of the world may have each country hyperlinked to further information about that country. The intention of an image map is to provide an easy way of linking various parts of an image without dividing the image into separate image files.

Implementation of image maps

<imagemap>Image:JoshuaReynoldsParty.jpg|Image map example. Clicking on a person in the picture causes the browser to load the appropriate article.|350px|thumb

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desc bottom-left </imagemap>

It is possible to create image maps by hand, using a text editor, however doing so requires that the web designer knows how to code HTML and also requires them to know the coordinates of the areas that they wish to place over the image. As a result, most image maps coded by hand are simple polygons.

Because creating image maps in a text editor requires much time and effort, there are many applications that allow the web designer to quickly and easily create image maps much as they would create shapes in a vector graphics editor. Examples of these are Adobe?s Dreamweaver, KImageMapEditor (for KDE), and the imagemap plugin found in GIMP.

Client-side vs. server-side

Image maps may be implemented either client-side or server-side. With a client-side image map, the determination of the target page can be done entirely on the user's own machine. A server-side image map must pass location data back to the server, which then determines the target page. Client-side image maps are generally better in accessibility terms, but server-side image maps give more flexibility to deal with complex decision-making.^[1]

Rollover effects

When designing an image map it is important to indicate to the user that the image is mapped. This may be done by a text instruction accompanying the image (like the one illustrating this page), by an indication within the image itself, or by a rollover effect which will alert the user that different sections of the image will respond differently to their interaction. When using an editor capable of layering images such as Photoshop or GIMP, sections of the image may be cut and pasted in place over a copy of the image which has reduced brightness. These highlighted areas will stand out to the user.

Client-side image maps can be implemented so that the user is given a visual indication of what can be clicked on. This can be an indication of the position of all the hot spots, or can be a rollover indication of the currently active hot spot. This functionality cannot be implemented using pure HTML, but can be implemented when a Clickable image is built using a programming environment such as XHTML with Cascading Style Sheets, ECMAScript and Java.

Rollover effects can be implemented by writing ECMAScript code to swap out the entire image with one that has that particular area highlighted, but this technique can use a considerable amount of bandwidth. Another solution is to script one or more page elements to respond as the mouse moves over the image.

Notes

See also

• Commons:Image map resources

External links

• Info on Image Maps from the W3C

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