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Implementing Image Maps

Both types of imagemaps use Cartesian coordinates (x,y) to map an image. The origin (0,0) is at the upper left corner of the image, and the coordinates are in pixels from the origin..

Three shapes are used to define the mapped areas in an imagemap:

Circle

For Client-Side: defined by center (x,y) and radius length
For Server-Side: defined by center (x,y) and (x,y) on edge of circle

Rectangle

top left and bottom right (x,y)

Polygon

any shape defined by up to 100 (x,y) points

In the case of overlaps, the first shape specified takes priority. Think of later entries as being inserted underneath existing entires.

It is also possible to define holes in existing shapes so that whatever is underneath is exposed.

In addition, it is possible to specify a default hyperlink for clicks registered outside of defined "hot spots".

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"Mastering a Web Site" online course Created and maintained by Lorna Schmid and David Boldt. http://water.usgs.gov/usgs/training/webmaster/image_maps2.html     Last modified: Wed Nov 12 17:57:18 EST 2003