Geografic-Information-System/raster/r.out.ppm/r.out.ppm.html

<h2>DESCRIPTION</h2>

<em>r.out.ppm</em> converts a GRASS raster map into a PPM image 
at the pixel resolution of the CURRENTLY DEFINED REGION. 
To get the resolution and region settings of the raster map, run:<p>
<div class="code"><pre>
g.region -p rast=[mapname]
</pre></div>

<p>
before running <em>r.out.ppm</em>.<p>
By default the PPM file created is 24-bit color, rawbits storage.
You can use the <b>-g</b> flag to force <em>r.out.ppm</em> to 
output an 8-bit greyscale instead.
The greyscale conversion uses the NTSC conversion:<p>
<div class="code"><pre>
Y = .30*Red + .59*Green + .11*Blue
</pre></div>

<p>One pixel is written for each cell value, so if <tt>ew_res</tt> and 
<tt>ns_res</tt> differ, the aspect ratio of the resulting image will be off.


<h2>NOTES</h2>
A few ppm file comments are written: the name of the GRASS
raster map, resolution, etc.  Although these are perfectly legal,
I've found one PD image utility that chokes on them, so if you need 
a commentless PPM file, use '<tt>out=-&nbsp;&gt;&nbsp;outfile.ppm</tt>'. (When sending 
output to stdout, no comments are written.)

<h2>HINTS</h2>

You can create a PNG image with NULL values represented by a transparent 
background by using the <a href="pngdriver.html">PNG driver</a> with 
<a href="variables.html">GRASS_TRANSPARENT</a> set to TRUE.
Alternatively, you can use the <em>pnmtopng</em> program from 
<a href="http://netpbm.sourceforge.net">netpbm</a> to do this:

<div class="code"><pre>
r.out.ppm raster
pnmtopng -transparent white raster.ppm > raster.png
</pre></div>

<h2>SEE ALSO</h2>
<em><a href="d.out.png.html">d.out.png</a></em><br>
<em><a href="r.out.ascii.html">r.out.ascii</a></em><br>
<em><a href="r.out.mpeg.html">r.out.mpeg</a></em><br>
<em><a href="r.out.png.html">r.out.png</a></em><br>
<em><a href="r.out.ppm3.html">r.out.ppm3</a></em><br>
<em><a href="r.out.tiff.html">r.out.tiff</a></em>
 
<h2>AUTHOR</h2>

Bill Brown, UIUC

<p><i>Last changed: $Date$</i>