HTMLMAP driver Tom Poindexter tpoindex@nyx.net This display driver is to allow 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 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.) The driver will attempt to trim polygons that have more that 100 vertices (also see GRASS_RENDER_HTMLMAXPOINTS, below.) 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. It is intended that all polygons that exists in a vector file 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.area - draw polygons from a vector file. 0. Set environment variables: GRASS_RENDER_WIDTH=xxx #if you want another size than the default 640 export GRASS_RENDER_WIDTH GRASS_RENDER_HEIGHT=xxx #if you want another size than the default 480 export GRASS_RENDER_WIDTH Additionally, HTMLMAP driver recognizes: export GRASS_RENDER_HTMLTYPE GRASS_RENDER_HTMLTYPE=xxx specifies the type of Html map to create: CLIENT - Netscape client-side image map (default). (NAME="map") APACHE - Apache/NCSA server-side image map RAW - Raw url and polygon vertices ("url x1 y1 x2 y2 .....") suitable for conversion to CERN server format, or any other format with user supplied conversion program. export GRASS_RENDER_FILE GRASS_RENDER_FILE=xxxxxx 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 is overwritten without warning. export GRASS_RENDER_HTMLMINDIST GRASS_RENDER_HTMLMINDIST=xx specifies the minimum distance (in pixels) that a point must change from the previous one to keep in the list of vertices for a polygon. The default is '2', which means that a point's x or y difference from the previous point must change by a number of pixels greate than this value. This parameters helps to eliminate points closely spaced points. export GRASS_RENDER_HTMLMINBBOX GRASS_RENDER_HTMLMINBBOX=xx specifies the minimum bounding box dimensions (both width and height) in order to store a polygon. The default is '2', which means any polygon having bounding box width or height extent of less than 2 pixels will not be output as a clickable area. This parameter helps to eliminate clickable areas that are one pixel in height or width, typically a single point or line. export GRASS_RENDER_HTMLMAXPOINTS GRASS_RENDER_HTMLMAXPOINTS=xx specifies the maxiumum number of vertices that a polygon can have. The default is 99. Some browser can only handle image map polygons of less that 100 vertices. 1. Start it up. # set the environment variables (above) if desired, or use defaults d.mon start=HTMLMAP d.mon select=HTMLMAP 2. Display text strings (href's) and area polygons: echo "http://www.no-such-place.net/area51/" | d.text d.vect.area map=area51 echo "http://www.roswell-nm.net/little/green/men.html" | d.text d.vect.area map=roswell 3. When done displaying stuff to HTMLMAP driver, use d.mon stop=HTMLMAP This will write the image map file file. A new file called 'htmlmap' (or whatever you specified with GRASS_RENDER_FILE) will be created in your current directory. 4. In practice, you'll want to create gif/jpg/png images that correspond with your newly created image map: # using previous GRASS_RENDER_WIDTH & GRASS_RENDER_HEIGHT d.mon start=CELL d.mon select=CELL d.rast map=terrain d.vect.area map=area51 fillcolor=white linecolor=blue d.vect.area map=roswell fillcolor=yellow linecolor=blue d.vect map=states color=green d.vect map=roads color=blue d.mon stop=CELL # make the region the same as the newly created cell for ppm export g.pushregion.sh # or 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.gif # assemble some html with the image and the image map echo '' >alien.html cat htmlmap >>alien.html echo '' >>alien.html # don't forget to reset your region g.popregion.sh # or g.region region=saved.reg # take a look and test it out netscape file:`pwd`/alien.html & Building the HTMLMAP driver: Change to the HTMLMAP directory, and make it: cd src/display/devices/HTMLMAP gmake5 If all goes well, the HTMLMAP driver will be compiled and moved into your device driver directory ($GISBASE/driver) and "etc/monitorcap" will be modified. Other: Don't forget to add the HTMLMAP driver in your monitorcap file! Your monitorcap file exists as $GISBASE/etc/monitorcap. HTMLMAP:driver/HTMLMAP:Create HTML Image Map: \ /usr/local/grass43/dev/fifo.9a /usr/local/grass43/dev/fifo.9b \ ::any terminal Note: This job will be done by the Gmakefile. 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 & 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"/' foomap.html ----------------------------- http://www.nyx.net/~tpoindex/grass-stuff/