htmlmapdriver(1)

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

6       htmlmapdriver
7

NAME

9       HTMLMAP driver - driver to create HTML image maps
10       (drivers)
11

DESCRIPTION

13       The  HTMLMAP  driver  allows the generation of HTML image maps for area
14       vector data. HTML image maps are used in  conjunction  with  images  to
15       provide  unique  URL  targets  for  different portions of an image. The
16       HTMLMAP driver can create both client-side  image  maps  embedded  into
17       HTML files, or server-side image maps used by web server software.
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19       Note  that  GRASS display commands that require the MOUSE will not work
20       correctly (or at all!)
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22       Polygons can at most have 100 vertices  (this  limit  imposed  by  HTML
23       image  map  formats,  see  GRASS_HTMLMAXPOINTS  below.) The driver will
24       attempt to trim polygons that have more that 100 vertices  by  removing
25       vertices  with the least amount of angle to the next vertice. Also, any
26       polygon that is entirely bounded by another polygon will be discarded.
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28       Text written to the driver before polygons are used as the HREF tag for
29       all  subsequent  polygons  written. All polygons that exist in a vector
30       map will have the same HREF tag.
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32       The only GRASS display commands that should be used  with  this  driver
33       are:
34              d.text - pass href information for resulting image maps.  d.vect
35              - draw polygons from a vector map.
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USAGE

38   Environment variablesSeveral environment variables effect the operation
39       of HTMLMAP.
40              GRASS_WIDTH=xxx
41              the width of the image map (default is 640).
42              GRASS_HEIGHT=yyy
43              the height of the image map (default is 480).
44              GRASS_HTMLTYPE=type
45              the type of image mape to create (default is CLIENT):
46                     CLIENT       Netscape/IE    client-side    image     map.
47                     (NAME="map")
48                     APACHE    Apache/NCSA server-side image map.
49                     RAW          Raw  url  and polygon vertices ( url  x1  y1
50                     x2  y2 format with user supplied conversion program.
51              GRASS_HTMLFILE=filename
52              specifies the resulting  file  to  store  the  html  image  map,
53              default  is htmlmap. Files without absolute path names are writ‐
54              ten in the current directory where the driver was started.
55              Any existing file of the same name is overwritten without  warn‐
56              ing.
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58              GRASS_HTMLMINDIST=n
59              specifies  the  minimum  distance  in  pixels  that a point must
60              change from the previous point to keep in the list  of  vertices
61              for  a  polygon.  The default is 2, which means that a point's x
62              and y difference from the previous point must change by a number
63              of  pixels  greater  than  this  value.  This parameter helps to
64              eliminate closely spaced points.
65              GRASS_HTMLMINBBOX=n
66              specifies the minimum bounding box dimensions to record a  poly‐
67              gon  as  a clickable area.  The default is 2, which means that a
68              polygon with a bounding box of  less  than  this  value  is  not
69              included.  This parameter helps to eliminate polygons than are a
70              point or line.
71              GRASS_HTMLMAXPOINTS=n
72              specifies the maximum number of vertices included in a polygon's
73              clickable  area.   The  default  is  99.  Some browsers can only
74              accomodate polygons of 100 vertices or less.  The HTMLMAP driver
75              automatically  ensures  that  a  polygon is closed by making the
76              last point the same as the first point.
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78   Typical usage
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80                       d.mon select=HTMLMAP
81               Display text strings (HREF's) and polygons
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83                       echo "http://www.no-such-place.net/area51/" | d.text
84                       d.vect map=area51
85                       echo  "http://www.roswell-nm.net/little/green/men.html"
86              | d.text
87                       d.vect map=roswell
88               Stop the driver when all polygon have been displayed. This will
89              cause a file named 'htmlmap'  to  be  created  in  your  current
90              directory.
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92                       d.mon stop=HTMLMAP
93                You  will also want to create an image for your image map. Use
94              the PNG driver and other utilities to create .gif or .jpg files.
95              The  following  example  is  somewhat  out of date and refers to
96              options available in GRASS 5.
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98                       # using previous GRASS_WIDTH & GRASS_HEIGHT
99                       d.mon start=PNG
100                       d.mon select=PNG
101                       d.rast map=terrain
102                       d.vect map=area51  fillcolor=white  linecolor=blue
103                       d.vect map=roswell fillcolor=yellow linecolor=blue
104                       d.vect map=states  color=green
105                       d.vect map=roads   color=black
106                       d.mon stop=PNG
107                       # make the region the same as the  newly  created  cell
108              for ppm export
109                       g.region save=saved.reg
110                       g.region raster=D_cell
111                       r.out.ppm -q input=D_cell output=alien.ppm
112                       # use the netpbm utilities to create a gif (quantize if
113              needed)
114                       ppmquant 128 <alien.ppm |  ppmtogif >alien.gif
115                       # assemble some html with the image and the image map
116                       cat                                             htmlmap
117              >>alien.html
118                       # don't forget to reset your region
119                       g.region region=saved.reg
120                       # take a look and test it out
121                       netscape file:`pwd`/alien.html &
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NOTES

125       HTMLMAP  was adapted from the CELL driver in GRASS 4.3.  Point-in-poly‐
126       gon test code was lifted from Randolph Franklin's web page, see
127              http://www.ecse.rpi.edu/Homepages/wrf/
128              http://www.ecse.rpi.edu/Homepages/wrf/research/geom/pnpoly.html
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130       If you create an HTML file with two or more images and image maps,  you
131       will  need  to  edit  the map names. The HTMLMAP driver creates its map
132       with the name map. A small sed script can easily change the map name:
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NAME

NAME

DESCRIPTION

USAGE

NOTES

SEE ALSO