
NAME
r.out.ppm  - Converts a GRASS raster file to a PPM image file at the pixel resolution of the CURRENTLY DEFINED REGION.
KEYWORDS
raster
SYNOPSIS
r.out.ppm
r.out.ppm help
r.out.ppm [-qG] input=string  [output=string]  
Flags:
- -q
 
- Run quietly
 
- -G
 
- Output greyscale instead of color
 
Parameters:
- input=string
 
- Raster input map
 
- output=string
 
- Name for new PPM file. (use out=- for stdout)
 
- Default: .ppm
 
DESCRIPTION
r.out.ppm converts a GRASS raster file 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:
g.region -p rast=[mapname]
 
before running r.out.ppm.
By default the PPM file created is 24-bit color, rawbits storage.
You can use the -G flag to force r.out.ppm to 
output an 8-bit greyscale instead.
The greyscale conversion uses the NTSC conversion:
Y = .30*Red + .59*Green + .11*Blue
 
One pixel is written for each cell value, so if ew_res and 
ns_res differ, the aspect ratio of the resulting image will be off.
NOTES
A few ppm file comments are written: the name of the GRASS
raster file, 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 'out=- > outfile.ppm'. (When sending 
output to stdout, no comments are written.)
HINTS
You can create a PNG image with NULL values represented by a transparent 
background by using the PNG driver with 
GRASS_TRANSPARENT set to TRUE.
Alternatively, you can use the pnmtopng program from 
netpbm to do this:
r.out.ppm raster
pnmtopng -transparent white raster.ppm > raster.png
 
SEE ALSO
d.out.png
r.out.ascii
r.out.mpeg
r.out.png
r.out.ppm3
r.out.tiff
 
AUTHOR
Bill Brown, UIUC
Last changed: $Date: 2007/01/28 22:18:17 $
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