Note: A new GRASS GIS stable version has been released: GRASS GIS 7, available here. And see the new manual page here
r.out.ppm - Converts a GRASS raster map to a PPM image file at the pixel resolution of the currently defined region.
r.out.ppm [-qG] input=name [output=name] [--verbose] [--quiet]
- Run quietly
- Output greyscale instead of color
- Verbose module output
- Quiet module output
- Name of input raster map
- Name for new PPM file (use '-' for stdout)
- Default: .ppm
r.out.ppm 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:
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.
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 'out=- > outfile.ppm'. (When sending
output to stdout, no comments are written.)
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:
pnmtopng -transparent white raster.ppm > raster.png
Bill Brown, UIUC
Last changed: $Date: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $
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