Image Maps

Monmouth Internet users can use NCSA server side imagemaps on your web sites. There is an offsite tutor.

If you prefer you may also use Client Site maps. Yahoo's Imagemap page provides links to Imagemap utilities and information. The menu on the left is a good example of a Server Side Imagemap.

Referencing your mapfile

<A HREF="/imagemap.map"> <IMG ISMAP SRC="/imagemap.gif"> </A>

Imagemap File

The lines in the imagemap files can have one of several formats:

directive value [x,y ...]
directive value "Menu text" [x,y ...]
directive value x,y ... "Menu text"

The directive is one of base, default, poly, circle, rect, or point. The value is an absolute or relative URL, or one of the special values listed below. The coordinates are x,y pairs separated by whitespace. The quoted text is used as the text of the link if a imagemap menu is generated. Lines beginning with '#' are comments.

Imagemap File Directives

There are six directives allowed in the imagemap file. The directives can come in any order, but are processed in the order they are found in the imagemap file.

base Directive

Has the effect of <BASE HREF="value">. The non-absolute URLs of the map-file are taken relative to this value. The base directive overrides ImapBase as set in a .htaccess file or in the server configuration files. In the absence of an ImapBase configuration directive, base defaults to http://server_name/.
base_uri is synonymous with base. Note that a trailing slash on the URL is significant.

default Directive

The action taken if the coordinates given do not fit any of the poly, circle or rect directives, and there are no point directives. Defaults to nocontent in the absence of an ImapDefault configuration setting, causing a status code of 204 No Content to be returned. The client should keep the same page displayed.

poly Directive

Takes three to one-hundred points, and is obeyed if the user selected coordinates fall within the polygon defined by these points.

circle

Takes the center coordinates of a circle and a point on the circle. Is obeyed if the user selected point is with the circle.

rect Directive

Takes the coordinates of two opposing corners of a rectangle. Obeyed if the point selected is within this rectangle.

point Directive

Takes a single point. The point directive closest to the user selected point is obeyed if no other directives are satisfied. Note that default will not be followed if a point directive is present and valid coordinates are given.

Values

The values for each of the directives can any of the following:

a URL

The URL can be relative or absolute URL. Relative URLs can contain '..' syntax and will be resolved relative to the base value.
base itself will not resolved according to the current value. A statement base mailto: will work properly, though.

map

Equivalent to the URL of the imagemap file itself. No coordinates are sent with this, so a menu will be generated unless ImapMenu is set to 'none'.

menu

Synonymous with map.

referer

Equivalent to the URL of the referring document. Defaults to http://servername/ if no Referer: header was present.

nocontent

Sends a status code of 204 No Content, telling the client to keep the same page displayed. Valid for all but base.

error

Fails with a 500 Server Error. Valid for all but base, but sort of silly for anything but default.

Coordinates

0,0 200,200

A coordinate consists of an x and a y value separated by a comma. The coordinates are separated from each other by whitespace. To accommodate the way Lynx handles imagemaps, should a user select the coordinate 0,0, it is as if no coordinate had been selected.

Quoted Text

"Menu Text"

After the value or after the coordinates, the line optionally may contain text within double quotes. This string is used as the text for the link if a menu is generated:
<a HREF="http://foo.com/">Menu text</a>
If no quoted text is present, the name of the link will be used as the text:
<a HREF="http://foo.com/">http://foo.com</a>
It is impossible to escape double quotes within this text.

Example Mapfile

#Comments are printed in a 'formatted' or 'semiformatted' menu. #And can contain html tags. <hr> base referer poly map "Could I have a menu, please?" 0,0 0,10 10,10 10,0 rect .. 0,0 77,27 "the directory of the referer" circle http://www.inetnebr.com/lincoln/feedback/ 195,0 305,27 rect another_file "in same directory as referer" 306,0 419,27 point http://www.zyzzyva.com/ 100,100 point http://www.tripod.com/ 200,200 rect mailto:nate@tripod.com 100,150 200,0 "Bugs?"

Referencing your mapfile

<A HREF="/imagemap.map"> <IMG ISMAP SRC="/imagemap.gif"> </A>

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