---
name: "r.out.ppm"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/r.out.ppm"
---

# r.out.ppm(1grass)

Converts a GRASS raster map to a PPM image file.

## NAME

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

## KEYWORDS

raster, export, output

## SYNOPSIS

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

### Flags:

- **-g**

  Output greyscale instead of color

- **-h**

  Suppress printing of PPM header

- **--overwrite**

  Allow output files to overwrite existing files

- **--help**

  Print usage summary

- **--verbose**

  Verbose module output

- **--quiet**

  Quiet module output

- **--ui**

  Force launching GUI dialog

### Parameters:

- **input**=*name* **\[required\]**

  Name of input raster map

- **output**=*name*

  Name for new PPM file (use ’-’ for stdout)\
   Default: *\<rasterfilename\>.ppm*

## DESCRIPTION

*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.

## NOTES

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.)

## HINTS

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*

## AUTHOR

Bill Brown, UIUC

## SOURCE CODE

Available at: r.out.ppm source code (history)

Accessed: Monday Feb 24 17:50:44 2025

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