r.out.ppm.1grass man page

r.out.ppm — Converts a GRASS raster map to a PPM image file.


raster, export


r.out.ppm --help
r.out.ppm [-gh] input=name [output=name] [--overwrite] [--help] [--verbose] [--quiet] [--ui]


Output greyscale instead of color
Suppress printing of PPM header
Allow output files to overwrite existing files
Print usage summary
Verbose module output
Quiet module output
Force launching GUI dialog


input=name [required]
Name of input raster map
Name for new PPM file (use ’-’ for stdout)
Default: <rasterfilename>.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 raster=[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_RENDER_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.file, r.out.ascii, r.out.gdal, r.out.mpeg, r.out.png, r.out.ppm3


Bill Brown, UIUC

Last changed: $Date: 2014-12-19 22:55:37 +0100 (Fri, 19 Dec 2014) $

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