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HTMLMAP driver - driver to create HTML image maps.


The HTMLMAP driver allows the generation of HTML image maps for area vector data. HTML image maps are used in conjunction with images to provide unique URL targets for different portions of an image. The HTMLMAP driver can create both client-side image maps embedded into HTML files, or server-side image maps used by web server software.

Note that GRASS display commands that require the MOUSE will not work correctly (or at all!)

Polygons can at most have 100 vertices (this limit imposed by HTML image map formats, see GRASS_HTMLMAXPOINTS below.) The driver will attempt to trim polygons that have more that 100 vertices by removing vertices with the least amount of angle to the next vertice. Also, any polygon that is entirely bounded by another polygon will be discarded.

Text written to the driver before polygons are used as the HREF tag for all subsequent polygons written. All polygons that exist in a vector map will have the same HREF tag.

The only GRASS display commands that should be used with this driver are:


Environment variables

Several environment variables affect the operation of HTMLMAP.

Typical usage


HTMLMAP was adapted from the CELL driver in GRASS 4.3. Point-in-polygon test code was lifted from Randolph Franklin's web page, see

If you create an HTML file with two or more images and image maps, you will need to edit the map names. The HTMLMAP driver creates its map with the name map. A small sed script can easily change the map name:

  sed -e 's/NAME="map"/NAME="foomap"/' < htmlmap > foomap.html


Display drivers
PNG driver, PostScript driver, XDRIVER
d.mon, d.text, d.vect

Last changed: $Date: 2016-08-17 23:50:38 -0700 (Wed, 17 Aug 2016) $

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