[GRASS-CVS] glynn: grass6/lib/cairodriver description.html, NONE, 1.1

grass at intevation.de grass at intevation.de
Fri Nov 23 22:25:47 EST 2007 

Author: glynn

Update of /grassrepository/grass6/lib/cairodriver
In directory doto:/tmp/cvs-serv3622/lib/cairodriver

Added Files:
	description.html 
Log Message:
Added description.html file


--- NEW FILE: description.html ---
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
 <TITLE>Cairo 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>Cairo driver</B></EM> - driver for bitmap or vector output using the Cairo graphics library
<BR><EM>(drivers)</EM> 
<H2>DESCRIPTION</H2>
<P>
The Cairo driver generates PNG, BMP, PPM, PS, PDF or SVG images from GRASS display commands, using the <A HREF="http://www.cairographics.org/">Cairo graphics library</A>. The image format is selected from the extension of the output file.
<P>
It is started as 'pseudo' monitor (output to an image file) and when stopped, all output from previously used display commands are written to the output file.

<H2>USAGE</H2>
<H3>Environment variables</H3>
Several environment variables affect the operation of the Cairo driver:
<UL>
  <LI><B>GRASS_WIDTH=xxx</B><BR>
     the width of the image.<BR><BR>
  <LI><B>GRASS_HEIGHT=yyy</B><BR>
    the height of the image.<BR><BR>
  <LI><B>GRASS_CAIROFILE=filename</B><BR>
     the name and format of the resulting image file, default is
     <b>map.png</b>.<BR>
     The image format is determined from the file extension.<BR>
     Supported bitmap formats:
     <UL>
     <LI><B>.png</B> - Portable Network Graphics (PNG)
     <LI><B>.bmp</B> - Windows Bitmap (BMP)
     <LI><B>.ppm</B> - Portable Pixmap (PPM)
     </UL>
     Supported vector formats:
     <UL>
     <LI><B>.pdf</B> - Portable Document Format (PDF)
     <LI><B>.ps</B> - PostScript (PS)
     <LI><B>.svg</B> - Scalable Vector Graphics (SVG)
     </UL>
     (Note: Some formats may not be available, depending on your platform and
     the Cairo library that GRASS was built with.)
     <br><br> 
  <LI><B>GRASS_BACKGROUNDCOLOR=RRGGBB</B><BR>
     specifies the background color to use in RGB
     notation (hex values). Default is <b>FFFFFF</b> (white).<br><br>
  <LI><B>GRASS_TRANSPARENT=[TRUE|FALSE]</B><BR>
    sets transparent background on (TRUE) or off (FALSE, default).<BR><BR>
  <LI><B>GRASS_AUTO_WRITE=[TRUE|FALSE]</B><BR>
     if set to "TRUE", the image file will be written after each 
     operation (i.e. whenever a client disconnects), rather than
     only being written out when the driver terminates.<BR>
     (Note: This only applies to bitmap formats - vector formats
     are always written directly to file)<BR><BR>
  <LI><B>GRASS_CAIRO_READ</B><BR>
     if "TRUE", the Cairo driver will initialize the image from
     the contents of $GRASS_CAIROFILE.<BR>
     (Note: This is only supported for bitmap formats)<BR><BR>
  <LI><B>GRASS_CAIRO_MAPPED</B><BR>
     if "TRUE", the Cairo driver will map $GRASS_CAIROFILE as its framebuffer,
     rather than using memory. This only works with BMP files.<BR><BR>
</UL>


<H3>Examples</H3>
<P>
Example using the driver directly (bash-syntax):
<PRE>
export GRASS_TRUECOLOR=TRUE
export GRASS_CAIROFILE=spearfish.png
export GRASS_WIDTH=800
export GRASS_HEIGHT=800

d.mon start=cairo
d.rast map=elevation.10m
d.vect map=streams width=1 color=blue fcolor=aqua type=area,line
d.vect map=roads width=2
d.mon stop=cairo
</PRE>

<P>
Example using <I>d.out.file</I>:
<PRE>
d.mon x0
d.rast map=elevation.10m
d.vect map=streams width=1 color=blue fcolor=aqua type=area,line
d.vect map=roads width=2

d.out.file -c sf_cairo format=png size=800,800
</PRE>

<P>
A more complicated example using <I>d.out.file</I>:
<PRE>
r.shaded.relief map=elevation.dem
r.watershed elev=elevation.dem basin=watershed.basin thresh=10000

d.mon x1
d.shadedmap rel=elevation.dem.shade drape=watershed.basin bright=30
d.vect streams color=aqua fcolor=aqua type=area,line
d.vect roads where="label ~ 'light-duty road'" color=grey
d.vect roads where="label ~ 'unimproved'" color=orange
d.vect roads where="label ~ 'secondary highway'" color=100:100:100 width=2
d.vect roads where="label ~ 'primary highway'" color=50:50:50 width=2
d.vect railroads col=red width=2
d.vect roads where="label = 'interstate'" color=black width=3

d.vect archsites icon=basic/star size=25 fcolor=yellow

d.font Andale_Mono
echo "Spearfish, SD" | d.text color=black at=28.6,53.5 -b

d.out.file -c sf_cairo2 format=png
</PRE>


<H2>NOTES</H2> 

<P>To enable Cairo driver support, build grass with
<PRE>
make USE_CAIRO=1
</PRE>
This requires a reasonably recent version of the cairo libraries (cairo.h).
</P>

<P>Antialiasing is enabled by default for bitmap formats. There is currently no way of disabling this.</P>

<P>Cairo supports true vector format output whenever possible. However, if the selected format doesn't support a necessary feature, Cairo may fall back on rendering a bitmap representation of the image wrapped in the selected vector format.</P>

<P>Cairo driver output via <A HREF="d.out.file.html">d.out.file</A> is supported via the -c flag.</P>

<h2>SEE ALSO</h2>
<EM>
<A HREF="htmlmapdriver.html">HTML map driver</A>,
<A HREF="pngdriver.html">PNG driver</A>,
<A HREF="psdriver.html">PostScript driver</A>,
<A href="xdriver.html">XDRIVER</A>
<BR>
<A HREF="d.frame.html">d.frame</A>,
<A href="d.mon.html">d.mon</A>,
<A href="d.rast.html">d.rast</A>,
<A href="d.vect.html">d.vect</A>
<A href="d.out.file.html">d.out.file</A>
</EM>

<H2>AUTHOR</H2>
Lars Ahlzen &lt;<I>lars (at) ahlzen.com</I>&gt;<BR>
and the GRASS Development Team.

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