---
name: "ppmtopgm"
section: "1"
platform: "linux"
package: "netpbm"
version: "10.86.51-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/ppmtopgm"
---

# ppmtopgm(1)

convert a PPM image to a PGM image

## NAME

ppmtopgm - convert a PPM image to a PGM image

## SYNOPSIS

**ppmtopgm**

\[*ppmfile*\]

## DESCRIPTION

This program is part of **Netpbm**(1) .

**ppmtopgm** reads a PPM as input and produces a PGM as output. The output is a "black and white" rendering of the original image, as in a black and white photograph.  The quantization formula **ppmtopgm** uses is y = .299 r + .587 g + .114 b.

The dimensions and maxval of the output are the same as the input. Note that with only one color plane, there are far fewer brightnesses that can be represented with the same maxval than with three color planes, so you may want to increase the maxval of the input with **pamdepth** before giving it to **ppmtopgm** to avoid loss of information.  For example, with a maxval of 1, there are 8 brightnesses that are possible in a PPM (though some of them are barely distinguishable), but only 2 brightness levels possible in a PGM.

Note that although there is a **pgmtoppm** program, it is not necessary for simple conversions from pgm to ppm , because any ppm program can read pgm (and pbm ) files automatically.  **pgmtoppm** is for colorizing a pgm file.  Also, see **ppmtorgb3** for a different way of converting color to gray.  And **ppmdist** generates a grayscale image from a color image, but in a way that makes it easy to differentiate the original colors, not necessarily a way that looks like a black and white photograph.

## OPTIONS

There are no command line options defined specifically for **ppmtopgm**, but it recognizes the options common to all programs based on libnetpbm (See \
  Common Options ⟨index.html#commonoptions⟩ .)

## QUOTE

```
Cold-hearted orb that rules the night
Removes the colors from our sight
Red is gray, and yellow white
But we decide which is right
And which is a quantization error.
```

## SEE ALSO

[**pgmtoppm**(1)](/pgmtoppm/1.md) , [**ppmtorgb3**(1)](/ppmtorgb3/1.md) , [**rgb3toppm**(1)](/rgb3toppm/1.md) , [**ppmdist**(1)](/ppmdist/1.md) , **ppm**(1) , **pgm**(1)

## AUTHOR

Copyright (C) 1989 by Jef Poskanzer.

## DOCUMENT SOURCE

This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation is at

-

  **http://netpbm.sourceforge.net/doc/ppmtopgm.html**