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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

       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:
              d.text  -  pass  href information for resulting image maps.  d.vect - draw polygons
              from a vector map.


   Environment variablesSeveral environment variables affect the operation
       of HTMLMAP.
              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.

              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.
              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 accommodate 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 "" | d.text
              d.vect map=area51
              echo "" | 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 directory.
              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 &


       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: 2012-03-02 21:22:34 -0800 (Fri, 02 Mar 2012) $

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