Adding the USEMAP attribute to an
<IMG> element indicates that the image 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 (useful to ensure browser independence of HTML documents). The value used in the
USEMAP attribute specifies the location of the map definition to use with the image, in a format similar to the
HREF attribute on anchors. If the argument to
USEMAP starts with a '#', the map description is assumed to be in the same document as the
<IMG SRC="../images/image.gif" USEMAP="maps.html#map1">
This would use the map described as "map1" in "maps.html" as the overlay for the image file "image.gif". The map definition (see below) can be included either within the HTML document itself where the image is embedded, or in a completely separate file.
The different active regions of the image are described using MAP and AREA elements. The map describes each region in the image and indicates the location of the document to be retrieved when the defined area is activated. The basic format for the
MAP element is as follows:
<AREA [SHAPE="shape"] COORDS="x,y,..." [HREF="reference"] [NOHREF]>
The NAME specifies the name of the map so that it can be referenced by an
<IMG USEMAP=...> element (NOTE : the
NAME attribute of the
<AREA> element can also be used to reference the particular area for scripting purposes. See the information in the Document Object for more information). The SHAPE gives the shape of the specific area. Currently the shapes
"POLY" are supported (Mosaic only supports the
RECT shape), with
RECT being the default shape, if an explicit
SHAPE attribute is not specified. The COORDS attribute gives the co-ordinates of the shape, using image pixels as the units. For a rectangle (
COORDS are expressed as "left-x,top-y,right-x,bottom-y". For a circle, (
COORDS are expressed as "centre-x, centre-y, radius" and for a polygon (
SHAPE="POLY") (an irregular shape), the
COORDS are expressed in pairs of coordinates (i.e. "x1,y1,x2,y2,x3,y3... ") which defines the pixel coordinates of the various points of the polygonal image hotspot.
The NOHREF attribute indicates that clicks in this region should perform no action. An HREF attribute specifies where a click in that area should lead. Note that a relative anchor specification will be expanded using the URL of the map description as a base, rather than using the URL of the document from which the map description is referenced. If a
<BASE> tag is present in the document containing the map description, that URL will be used as the base to resolve partial URL's
An arbitrary number of
AREA elements may be specified. If two areas intersect, the one which appears first in the map definition takes precedence in the overlapping region.
<AREA> elements also support the following attributes:
The Internet Explorer 4.0 (and above) specific
TITLE attribute is used for informational purposes. If present in the
<AREA>, the value of the
TITLE attribute is presented as a ToolTip when the users mouse hovers over the section of the image defined by the
<AREA> element. The
TITLE attribute in the
<MAP> element can be used for informational purposes only (no ToolTip is presented to the user)
LANG attribute can be used to specify what language the
<AREA> elements are using. It accepts any valid ISO standard language abbreviation (for example
"en" for English,
"de" for German etc.) For more details, see the Document Localisation section for more details.
LANGUAGE attribute can be used to expressly specify which scripting language Internet Explorer 4.0 uses to interpret any scripting information used in the
<AREA> elements. It can accept values of
LANGUAGE attribute is set.
CLASS="Style Sheet class name"
CLASS attribute is used to specify the
<AREA> elements as using a particular style sheet class. See the Style Sheets topic for details.
STYLE="In line style setting"
As well as using previously defined style sheet settings, the
<AREA> elements can have in-line stylings attached to it. See the Style Sheets topic for details.
ID="Unique element identifier"
ID attribute can be used to either reference a unique style sheet identifier, or to provide a unique name for the
<AREA> element for scripting purposes. Any
<AREA> element with an
ID attribute can be directly manipulated in script by referencing its
ID attribute, rather than working through the All collection to determine the element. See the Scripting introduction topic for more information.
The following images all use a
<MAP...> element and
USEMAP attributes to specify them as image maps. Use the View Source option in the browser to see the source for these maps.
|A Circular image map - using
|A Rectangular image map - using
|A Polygonal image map - using
NOTE : The links in the above example don't actually exist, they're just there as an example. When the image is surrounded by an anchor element, which runs a script function, Netscape will only activate the script function when the actual hotspot as defined in the
<MAP> element is clicked. Internet Explorer will activate the script when _any_ part of the image is clicked on.
NOTE : The TARGET attribute can be used within the
<AREA> element, allowing the use of Client side image maps within framed documents. For more information about the use of
TARGET attributes, see the
<AREA> element in a document is an object that can be manipulated through scripting. Note that scripting of the CLient Side Image Maps elements/objects is supported to a greater extent by Internet Explorer 4.0 in its Dynamic HTML object model. Netscape does support some scripting of the
<AREA> element, through its appearance in the Links Collection (alongside
<A> elements). For details of Netscape scripting support, see the Links Collection topic.
Client Side Image Map Properties
<AREA> elements/objects support all of the standard Dynamic HTML properties (i.e. className, document, id, innerHTML, innerText, isTextEdit, lang, language, offsetHeight, offsetLeft, offsetParent, offsetTop, offsetWidth, outerHTML, outerText, parentElement, parentTextEdit, sourceIndex, style, tagName and title). Details of these can be found in the standard Dynamic HTML properties topics.
<AREA> element supports the following properties:
alt property directly reflects the
ALT attribute (see above) for the
coords property directly reflects the
COORDS attribute (see above) for the
hash property reflects, or sets any 'bookmark' definitions within the hot-spot's
HREF attribute. For example:
<AREA HREF="http://www.htmlib.com/files/intro.htm#contents" ID="ContentsLinkHotSpot" COORDS="...">
. . .
strHash have the value of
host property is essentially a combination of the
hostname (see below) and
port (see below) properties. For the above example (for the
hash property), the
host property would be
www.htmlib.com:80. (80 is the standard port for Web servers)
hostname property reflects, or sets the name of the computer identified in the
HREF attribute. Using the above example (for the
hash property), the
hostname property would be
href property reflects, or sets, the
HREF attribute of the hot-spot. It is possible to change a link's
href property through scripting.
noHref property reflects any setting of the
NOHREF attribute for the hot-spot.
pathname property reflects, or sets the full path to the target document, as given in the
HREF attribute. For example, in the above example for the
hash property, the
pathname property would be
As mentioned above, the
port property reflects, or sets the port setting (if given) in the
HREF attribute (if set). If no port is specified in the
HREF setting, then port 80 is assumed (the standard port for Web servers).
protocol property reflects, or sets the protocol of the
HREF attribute (if set). For example:
<AREA HREF="http://www.htmlib.com/" COORDS="..." ...>
http:// for the
search property reflects, or sets any search strings appended to the URL given in the
HREF attribute (if set), after the
? query string de-limiter.
shape property directly reflects the
SHAPE attribute (see above) for the
target property directly reflects the
TARGET attribute (see above) for the
Client Side Image Map Methods
<AREA> elements/objects support all of the standard Dynamic HTML methods (i.e. click, contains, getAttribute, insertAdjacentHTML, insertAdjacentText, removeAttribute, scrollIntoView and setAttribute). Details of these can be found in the standard Dynamic HTML Methods topics.
<AREA> element supports the following methods:
blur method can be used to force the users focus away from the
<AREA> element, thus firing the
blur method, the
focus method can be used to force the users focus to the referenced
<AREA> element, which then causes the
onfocus event to occur.
Client Side Image Map Events
<AREA> elements/objects support all of the standard Dynamic HTML events (i.e. onclick, ondblclick, ondragstart, onfilterchange, onhelp, onkeydown, onkeypress, onkeyup, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup and onselectstart). Details of these can be found in the standard Dynamic HTML events topics.
<AREA> element also supports the following events:
onblur event fires when the user removes the focus from the referenced
<AREA> element, either by clicking to another section of the document, by 'tabbing' away, or by a script function using the
As you've probably guessed, the
onfocus event fires when the user passes the focus to the referenced
<AREA> element, by clicking on it, by 'tabbing' to the hot-spot, or by a script function using the
focus method to pass the focus to the specific
© 1995-1998, Stephen Le Hunte
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