htmlmapdriver(1grass)						Grass User's Manual					     htmlmapdriver(1grass)

NAME

       HTMLMAP driver - driver to create HTML image maps.
       (drivers)

DESCRIPTION

       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 vec-
       tor map will have the same HREF tag.

       The only GRASS display commands that should be used with this driver are:
	      d.text - pass href information for resulting image maps.	d.vect - draw polygons from a vector map.

USAGE

   Environment variablesSeveral environment variables effect the operation
       of HTMLMAP.
	      GRASS_WIDTH=xxx
	      the width of the image map (default is 640).  GRASS_HEIGHT=yyy
	      the height of the image map (default is 480).  GRASS_HTMLTYPE=type
	      the type of image mape to create (default is CLIENT):
	      CLIENT	Netscape/IE client-side image map.  (NAME="map")
	      APACHE	Apache/NCSA server-side image map.
	      RAW	  Raw url and polygon vertices ( url  x1  y1  x2  y2 format with user supplied conversion program.

	      GRASS_HTMLFILE=filename
	      specifies the resulting file to store the html image map, default is htmlmap. Files without absolute path names are written  in  the
	      current directory where the driver was started.
	      Any existing file of the same name is overwritten without warning.  GRASS_HTMLMINDIST=n
	      specifies  the  minimum  distance  in  pixels that a point must change from the previous point to keep in the list of vertices for a
	      polygon.	The default is 2, which means that a point's x and y difference from the previous point must change by a number of  pixels
	      greater than this value.	This parameter helps to eliminate closely spaced points.  GRASS_HTMLMINBBOX=n
	      specifies the minimum bounding box dimensions to record a polygon as a clickable area.  The default is 2, which means that a polygon
	      with a bounding box of less than this value is not included. This parameter helps to eliminate polygons than are a  point  or  line.
	      GRASS_HTMLMAXPOINTS=n
	      specifies  the maximum number of vertices included in a polygon's clickable area.  The default is 99.  Some browsers can only accom-
	      modate polygons of 100 vertices or less.	The HTMLMAP driver automatically ensures that a polygon is closed by making the last point
	      the same as the first point.

   Typical usage
	      Start up the driver
	      d.mon start=HTMLMAP
	       Display text strings (HREF's) and polygons
	      echo "http://www.no-such-place.net/area51/" | d.text
	      d.vect map=area51
	      echo "http://www.roswell-nm.net/little/green/men.html" | d.text
	      d.vect map=roswell
		Stop  the driver when all polygon have been displayed. This will cause a file named 'htmlmap' to be created in your current direc-
	      tory.
	      d.mon stop=HTMLMAP
	       You will also want to create an image for your image map. Use the PNG driver and other utilities to create .gif or .jpg files.  The
	      following example is somewhat out of date and refers to options available in GRASS 5.
	      # using previous GRASS_WIDTH & GRASS_HEIGHT
	      d.mon start=PNG
	      d.mon select=PNG
	      d.rast map=terrain
	      d.vect map=area51  fillcolor=white  linecolor=blue
	      d.vect map=roswell fillcolor=yellow linecolor=blue
	      d.vect map=states  color=green
	      d.vect map=roads	 color=black
	      d.mon stop=PNG
	      # make the region the same as the newly created cell for ppm export
	      g.region save=saved.reg
	      g.region raster=D_cell
	      r.out.ppm -q input=D_cell output=alien.ppm
	      # use the netpbm utilities to create a gif (quantize if needed)
	      ppmquant 128 <alien.ppm |  ppmtogif >alien.gif
	      # assemble some html with the image and the image map
	      cat htmlmap					    >>alien.html

	      # don't forget to reset your region
	      g.region region=saved.reg
	      # take a look and test it out
	      netscape file:`pwd`/alien.html &

NOTES

       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
	      http://www.ecse.rpi.edu/Homepages/wrf/ http://www.ecse.rpi.edu/Homepages/wrf/research/geom/pnpoly.html

       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

SEE ALSO

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

       Last changed: $Date: 2010-01-20 14:26:08 +0100 (Wed, 20 Jan 2010) $

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       (C) 2003-2011 GRASS Development Team

GRASS 6.4.2														     htmlmapdriver(1grass)