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Geografic-Information-System


			
				
					
						
						
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							<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
 <TITLE>HTMLMAP driver</TITLE>
 <META http-equiv=Content-Type content="text/html; charset=iso-8859-1">
 <link rel="stylesheet" href="grassdocs.css" type="text/css">
</HEAD>
<BODY bgColor=white>

<img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade>

<H2>NAME</H2>

<EM><B>HTMLMAP driver</B></EM> - driver to create HTML image maps.
<BR><EM>(drivers)</EM>

<H2>DESCRIPTION</H2>

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. 
<P>
Note that GRASS display commands that require the MOUSE will not work 
correctly (or at all!) 
<P>
Polygons can at most have 100 vertices (this limit imposed by HTML image map 
formats, see <B>GRASS_HTMLMAXPOINTS</B> 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. 
<P>
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. 
<P>
The only GRASS display commands that should be used with this driver are: 
<UL>
  <LI><a href="d.text.html">d.text</A> 
  - pass href information for resulting image maps.</LI>
  <LI><a href="d.vect.html">d.vect</A> 
  - draw polygons from a vector map.</LI>
</UL>

<H2>USAGE</H2>

<H3>Environment variables</H3>Several environment variables effect the operation 
of HTMLMAP. 

<UL>
  <LI><B>GRASS_WIDTH=xxx</B><BR>the width of the image map (default is 
    640).
  </LI>
  <LI><B>GRASS_HEIGHT=yyy</B><BR>the height of the image map (default is 
    480).
  </LI>
  <LI><B>GRASS_HTMLTYPE=type</B><BR>the type of image mape to create (default is 
    CLIENT): 
    <DL>
      <DD><TT><B>CLIENT</B></TT> &nbsp;&nbsp; Netscape/IE client-side image map. 
	(NAME="map")<BR>
      <DD><TT><B>APACHE</B></TT> &nbsp;&nbsp; Apache/NCSA server-side image 
	map.<BR>
      <DD><TT><B>RAW</B></TT> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Raw url 
	and polygon vertices ( <I>url&nbsp; x1&nbsp; y1&nbsp; x2&nbsp; y2&nbsp; 
	  ..... </I>), suitable for conversion to CERN server format, or any other 
	format with user supplied conversion program.</DD>
    </DL>
  </LI>
  <LI><B>GRASS_HTMLFILE=filename</B><BR>
    specifies the resulting file to store 
    the html image map, default is <tt>htmlmap</tt>. Files without absolute path 
    names are written in the current directory where the driver was started. 
    <BR>
    <em>Any existing file of the same name is overwritten without 
      warning.</em>
  </LI>
  <LI><B>GRASS_HTMLMINDIST=n</B><BR>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 <tt>2</tt>, 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.
  </LI>
  <LI><B>GRASS_HTMLMINBBOX=n</B><BR>specifies the minimum bounding box
  dimensions to record a polygon as a clickable area.
  The default is <tt>2</tt>, 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.
  </LI>
  <LI><B>GRASS_HTMLMAXPOINTS=n</B><BR>specifies the maximum number of
  vertices included in a polygon's clickable area.
  The default is <tt>99</tt>.  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.</LI>
</UL>

<H3>Typical usage</H3>
<UL>
  <LI>Start up the driver
<DIV class="code"><PRE>
d.mon start=HTMLMAP
</PRE></DIV>
  </LI>
  <LI>Display text strings (HREF's) and polygons
<DIV class="code"><PRE>
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
</PRE></div>
  <LI>Stop the driver when all polygon have been displayed. This will cause a file 
    named 'htmlmap' to be created in your current directory.
<DIV class="code"><PRE>
d.mon stop=HTMLMAP
</PRE></DIV>
  <LI>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.
    <i>The following example is somewhat out of date and refers to options
      available in GRASS 5.</i>
<DIV class="code"><PRE>
# using previous GRASS_WIDTH &amp; 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
<!-- ????  FIXME -->
# 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 &lt;alien.ppm |  ppmtogif &gt;alien.gif 

# assemble some html with the image and the image map
echo '&lt;html&gt;&lt;body&gt;&lt;img src="alien.gif" usemap="#map"&gt;' &gt;alien.html
cat htmlmap                                           &gt;&gt;alien.html
echo '&lt;/body&gt;&lt;/html&gt;'                                 &gt;&gt;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 &amp;
</PRE></DIV>
  </LI>
</UL>

<H2>NOTES</H2>

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 
<UL>
  <LI><a href="http://www.ecse.rpi.edu/Homepages/wrf/">http://www.ecse.rpi.edu/Homepages/wrf/</A></LI>
  <LI><a href="http://www.ecse.rpi.edu/Homepages/wrf/research/geom/pnpoly.html">http://www.ecse.rpi.edu/Homepages/wrf/research/geom/pnpoly.html</A></LI>
</UL>

<P>
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 
<tt>map</tt>. A small sed script can easily change the map name:

<PRE>
  sed -e 's/NAME="map"/NAME="foomap"/' &lt; htmlmap &gt; foomap.html
</PRE>

<H2>SEE ALSO</H2>

<EM>
  <a href="displaydrivers.html">Display drivers</a>
  <br>
  <a href="pngdriver.html">PNG driver</A>,
  <a href="psdriver.html">PostScript driver</A>,
  <a href="xdriver.html">XDRIVER</A>
  <BR>
  <A href="d.mon.html">d.mon</A>,
  <a href="d.text.html">d.text</A>, 
  <a href="d.vect.html">d.vect</A>
</EM> 

<p>
<i>Last changed: $Date: 2008-03-23 14:34:53 +0000 (Sun, 23 Mar 2008) $</i>