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netpbm(1) General Commands Manual netpbm(1)


netpbm - package of graphics manipulation programs and libraries


Netpbm is a package of graphics programs and programming libraries.

There are over 220 separate programs in the package, most of which have "pbm", "pgm", "ppm", or "pnm" in their names. For example, pnmscale and giftopnm.

For example, you might use pnmscale to shrink an image by 10%. Or use pnmcomp to overlay one image on top of another. Or use pbmtext to create an image of text. Or reduce the number of colors in an image with pnmquant.

The Netpbm Formats

All of the programs work with a set of graphics formats called the "netpbm" formats. Specifically, these formats are pbm(5), pgm(5), ppm(5), and pam(5). The first three of these are sometimes known generically as pnm. Many of the Netpbm programs convert from a Netpbm format to another format or vice versa. This is so you can use the Netpbm programs to work on graphics of any format. It is also common to use a combination of Netpbm programs to convert from one non-Netpbm format to another non-Netpbm format. Netpbm has converters for over 80 graphics formats, and as a package Netpbm lets you do more graphics format conversions than any other computer graphics facility.

The Netpbm formats are all raster formats, i.e. they describe an image as a matrix of rows and columns of pixels. In the PBM format, the pixels are black and white. In the PGM format, pixels are shades of gray. In the PPM format, the pixels are in full color. The PAM format is more sophisticated. A replacement for all three of the other formats, it can represent matrices of general data including but not limited to black and white, grayscale, and color images.

Programs designed to work with PBM images have "pbm" in their names. Programs designed to work with PGM, PPM, and PAM images similarly have "pgm", "ppm", and "pam" in their names.

All Netpbm programs designed to read PGM images see PBM images as if they were PGM too. All Netpbm programs designed to read PPM images see PGM and PBM images as if they were PPM. See the section "Implied Format Conversion" below.

Programs that have "pnm" in their names read PBM, PGM, and PPM but unlike "ppm" programs, they distinguish between them and their function depends on the format. For example, pnmtogif creates a black and white GIF output image if its input is PBM or PGM, but a color GIF output image if its input is PPM. And pnmscale produces an output image of the same format as the input. A ppmscale program would read all three PNM input formats, but would see them all as PPM and would always generate PPM output.

If it seems wasteful to you to have three separate PNM formats, be aware that there is a historical reason for it. In the beginning, there were only PBMs. PGMs came later, and then PPMs. Much later came PAM, which realizes the possibility of having just one aggregate format.

The formats are described in the man pages pbm(5), pgm(5), ppm(5), and pam(5),

Implied Format Conversion

A program that uses the PGM library to read an image can read a PBM image as well as a PGM image. The program sees the PBM image as if it were the equivalent PGM image, with a maxval of 255.

A program that uses the PPM library to read an image can read a PGM image as well as a PPM image and a PBM image as well as a PGM image. The program sees the PBM or PGM image as if it were the equivalent PPM image, with a maxval of 255 in the PBM case and the same maxval as the PGM in the PGM case.

Netpbm and Transparency

In many graphics format, there's a means of indicating that certain parts of the image are wholly or partially transparent, meaning that if it were displayed "over" another image, the other image would show through there. Netpbm formats deliberately omit that capability, since their purpose is to be extremely simple.

In Netpbm, you handle transparency via a transparency mask in a separate (slightly redefined) PGM image. In this pseudo-PGM, what would normally be a pixel's intensity is instead it an opaqueness value. See pgm(5). pnmcomp is an example of a program that uses a PGM transparency mask.

The Netpbm Programs

The Netpbm programs are generally useful run by a person from a command shell, but are also designed to be used by programs. A common characteristic of Netpbm programs is that they are simple, fundamental building blocks. They are most powerful when stacked in pipelines. Netpbm programs do not use graphical user interfaces (in fact, none of them display graphics at all, except for a very simple Linux Svgalib displayer) and do not seek input from a user.

Each of these programs has its own man page.

Common Options

There are a few options that are present on all programs that are based on the Netpbm libraries, including virtually all Netpbm programs. These are not mentioned in the individual man pages for the programs.

Suppress all informational messages that would otherwise be issued to Standard Error. (To be precise, this only works to the extent that the program in question implements the Netpbm convention of issuing all informational messages via the pm_message() service of the Netpbm libraries).
Instead of doing anything else, report the version of the libpbm library linked with the program (it may have been linked statically into the program, or dynamically linked at run time). Normally, the Netpbm programs and the libraries are installed at the same time, so this tells you the version of the program and all the other Netpbm libraries and files it uses as well.

Here is a directory of the Netpbm programs. You can also use man -k to search for a program that does what you want.


convert series of PPM frames to an MPEG movie
convert JFIF/JPEG/EXIF file to Netpbm format
convert PPM to JPEG/JFIF/EXIF format
convert any graphics format to Netpbm format
convert Windows or OS/2 Bitmap file to PPM
convert PPM to Windows or OS/2 Bitmap file
convert Windows icon file to PPM
convert PPM to Windows icon file
convert GIF to portable anymap
convert PPM to GIF
convert Netpbm format to Portable Network Graphics
convert PNG (Portable Network Graphics) to Netpbm formats
convert Palm pixmap to Netpbm formats
convert Netpbm formats to Palm pixmap
convert JBIG BIE (compressed bitmap) to PBM
convert a PAM image to PBM, PGM, or PPM
convert PBM to JBIG BIE (compressed bitmap)
convert Netpbm image to Fiasco (wfa) highly compressed format
convert Fiasco (wfa) highly compressed format to Netpbm image
convert photo CD to PPM
convert PBM to Nokia Smart Messaging Format (SMF)
convert PBM to WAP (Wireless App Protocol) Wireless Bitmap
convert WAP (Wireless App Protocol) Wireless Bitmap to PBM
convert Atari Neochrome (.neo) image to PPM
convert PPM image to Atari Neochrome (.neo)
convert from PBM to Microdesign (for Amstrad PCWs)
convert from Microdesign (for Amstrad PCWs) to PBM
convert Andrew Toolkit raster object to PBM
convert PBM to Andrew Toolkit raster object
convert Xerox doodle brushes to PBM
convert CMU window manager format to PBM
convert Group 3 FAX to PBM
convert PBM to Group 3 FAX
convert Sun icon to PBM
convert PBM to Sun icon
convert GEM .img format to PBM or pixmap
convert MacPaint to PBM
convert PBM to MacPaint
convert MGR format to PBM
convert PBM to MGR format
convert Atari Degas .pi3 to PBM
convert PBM to Atari Degas .pi3
convert X10 or X11 bitmap to PBM
convert PBM to X11 bitmap
convert PBM to X10 bitmap
convert Bennet Yee "face" file into PBM
convert PBM into Bennet Yee "face" file
convert PBM to Gemini 10x printer graphics
convert PBM to ASCII graphic form
convert ASCII character graphics to PGM
convert PBM to BBN BitGraph graphics
convert PBM to CMU window manager format
convert PBM to Epson printer graphics
convert PBM into GEM .img file
convert PBM to GraphOn graphics
convert PBM to HP LaserJet black and white graphics
convert PPM to HP LaserJet color graphics (PCL)
convert HP PaintJet file to PPM
convert PPM to HP PaintJet file
convert HP Thinkjet printer stream to PBM
convert PBM into Unix plot(5) file
convert PBM to Printronix graphics
convert PBM to Zinc Interface Library icon
convert FITS format to portable anymap
convert Netpbm formats to FITS format
convert Usenix FaceSaver(tm) format to PGM
convert PGM to Usenix FaceSaver(tm) format
convert HIPS format to PGM
convert a Lisp Machine bitmap file into PGM format
convert PGM into Lisp Machine format
convert Netpbm formats to Postscript
convert Postscript to Netpbm formats
convert PostScript "image" data to PGM
convert PBM image to Postscript using lines
convert a PBM image to encapsulated Postscript preview bitmap
convert PBM images to Postscript using G3 fax compression.
convert raw grayscale bytes to PGM
convert PGM to PBM
convert Gould scanner file to PPM
convert IFF ILBM to PPM
convert PPM to IFF ILBM
convert Img-whatnot to PPM
convert MTV ray-tracer output to PPM
convert PC Paintbrush format to PPM
colorize a portable graymap into a PPM
convert Atari Degas .pi1 to PPM
convert PPM to Atari Degas .pi1
convert Macintosh PICT to PPM
convert PPM to Macintosh PICT
convert QRT ray-tracer output to PPM
convert raw RGB bytes to PPM
convert an AutoCAD slide file into a PPM
convert Atari compressed Spectrum to PPM
convert Atari uncompressed Spectrum to PPM
convert TrueVision Targa file to PPM
convert PPM to TrueVision Targa file
convert Xim to PPM
convert XPM format to PPM
convert PPM to XPM format
convert Abekas YUV format to PPM
convert Encoder/Berkeley YUV format to PPM
convert PPM to Encoder/Berkeley YUV format
convert PPM to Abekas YUV format
convert PPM to 3 subsampled raw YUV files
merge 3 subsampled raw YUV files to one PPM
convert PPM to AutoCAD database or slide
convert PPM to NCSA ICR graphics
convert PPM to PC Paintbrush format
convert PPM to portable graymap
convert PPM to X11 "puzzle" file
convert Sun raster file to Netpbm formats
convert Netpbm formats to Sun raster file
convert TIFF file to portable anymap
convert Netpbm formats to TIFF RGB file
convert Netpbm formats to TIFF CMYK file
convert X10 or X11 window dump to Netpbm formats
convert Netpbm formats to X11 window dump
convert regular Netpbm format image into plain Netpbm format
convert PBM file to PGM by averaging areas
convert 411 (Sony Mavica) to PPM
convert PPM to DEC sixel format
convert PPM to Motif UIL icon file
convert Santa Barbara Instrument Group CCD file to PGM
convert Parallax XVideo JPEG to sequence of PPM files
convert PNM to Utah Raster Toolkit (urt/rle) file
convert Utah Raster Toolkit (urt/rle) file to PNM
convert PPM to Interleaf
convert Interleaf to PPM
convert Biorad confocal image to PGM
convert PGM image to Dec LN03+ Sixel image
convert PBM image to packed format (PK) font
convert packed format (PK) font to PBM image

Image Generators

All of these generate Netpbm format output.

create a blank PBM image of a specified size
create a PPM image of a specified size and color
generate a grayscale ramp
create a pretty PPM image
create a spectrum-like image with colors fading together.
create a PGM image of white noise
render text into a PBM image
create a Universal Product Code PBM image
generate a CIE color map PPM image
create a printer test pattern page in PBM format
create a color map (PPM image) containing all possible colors of given maxval

Image Editors

All of these work on the Netpbm formats

Add text to an image
add a shadow to an image so it looks like it's floating
brighten or dim an image -- change saturation and value
dim an image - different way from ppmbrighten
reduce a PBM N times, using Floyd-Steinberg
normalize contrast in a PGM image
normalize contrast in a PPM image
enlarge a PBM image with edge smoothing
scale an image with high precision
scale an image quickly with low precision
enlarge an image N times
ordered dither for color images
Choose the N best colors to represent an image; create a colormap
Replace colors in an image with those from a color map
quantize colors in a color image down to fewer colors
quantize colors/shades in a color or grayscale image down to fewer
quantize colors on many files
run a Laplacian Relief filter on a PPM
perform arithmetic on two images
concatenate images
add borders to an image
create composite (overlay) of images
mix (overlay) two images.
crop all like-colored borders off an image
select a rectangular region from an image
obsolete version of pamcut (kept because it may have fewer bugs)
slice an image into many horizontally and/or vertically
remove every other row from an image
extract a single plane (channel, e.g. R, G, or B) from an image
change the maxval in an image
perform one or more flip operations on an image
scale up an image by inserting interpolated pixels
scale by non-integer values using pamstretch and pnmscale
invert an image
perform gamma correction on an image
histogram equalize image to increase contrast
add a margin to an image
paste a rectangle into an image
rotate an image
shear an image
smooth am image
replicate an image into a specified size
remove lone pixels (snow) from a PBM image
antialias an image
change all of one color to another in PPM image
filter an image by replacing each pixel with a function of nearby pixels
shift lines of PPM image left or right a random amount
move pixels of PPM image a random amount
general MxN convolution on an image
combine three portable graymaps into one PPM
separate a PPM into three portable graymaps
apply Conway's rules of Life to a PBM image
map colors to high contrast grayscales arbitrarily
adjust colors so they are legal for NTSC or PAL television

Image Analyzers

These all work on the Netpbm formats as input.

describe an image's vital characteristics
measure difference between two images
edge-detect a PGM image
edge-enhance a PGM image
print grayscale values for a row or column of a PGM image
calculate textural features on a PGM image
print a histogram of the values in a PGM image
print a histogram of a PPM
draw a histogram of a PGM or PPM
generate a map of all colors in an image
generate a blue/green 3D glasses image from two images


display a PPM image on a Linux virtual console using Svgalib
create a mask bitmap from a regular bitmap
create mask of areas of a certain color in an image
split a multi-image Netpbm file into multiple 1-image files
build a visual index of a bunch of Netpbm images
build a visual index of a photo CD from PCD overview file
build multiple Netpbm images into a single montage image
Bentleyize a PGM image
create cratered terrain by fractal forgery
turn a PNM or PAM image into an oil painting
fractal forgeries of clouds, planets, and starry skies
generate a convolution kernel
Make an image lined so it looks like an old TV
Display PBM image on AT&T 4425 ASCII terminal with gfx chars

Uncatalogued As Yet

The Netpbm Libraries

The Netpbm programming libraries, libpbm(3), libpgm(3), libppm(3), and libpnm(3), make it easy to write programs that manipulate graphic images. Their main function is to read and write files in the Netpbm format, and because the Netpbm package contains converters for all the popular graphics formats, if your program reads and writes the Netpbm formats, you can use it with any formats.

But the libraries also contain some utility functions, such as character drawing and RGB/YCrCb conversion.

The libraries have the conventional C linkage. Virtually all programs in the Netpbm package are based on the Netpbm libraries.

Application Notes

As a collection of primitive tools, the power of Netpbm is multiplied by the power of all the other unix tools you can use with them. These notes remind you of some of the more useful ways to do this. Often, when people want to add high level functions to the Netpbm tools, they have overlooked some existing tool that, in combination with Netpbm, already does it.

Often, you need to apply some conversion or edit to a whole bunch of files.

As a rule, Netpbm programs take one input file and produce one output file, usually on Standard Output. This is for flexibility, since you so often have to pipeline many tools together.

Here is an example of a shell command to convert all your of PNG files (named *.png) to JPEG files named *.jpg:

for i in *.png; do pngtopnm $i | ppmtojpeg >`basename $i .png`.jpg; done

Or you might just generate a stream of individual shell commands, one per file, with awk or perl. Here's how to brighten 30 YUV images that make up one second of a movie, keeping the images in the same files:

ls *.yuv .br | perl -ne 'chomp;
print yuvtoppm $_ | ppmbrighten -v 100 | ppmtoyuv >tmp$$.yuv; ,
mv tmp$$.yuv $_0
' .br | sh

The tools find (with the -exec option) and xargs are also useful for simple manipulation of groups of files.

Some shells' "process substitution" facility can help where a non-Netpbm program expects you to identify a disk file for input and you want it to use the result of a Netpbm manipulation. Say printcmyk takes the filename of a Tiff CMYK file as input and what you have is a PNG file abc.png. Try:

printcmyk <({ pngtopnm abc.png | pnmtotiffcmyk ; })

It works in the other direction too, if you have a program that makes you name its output file and you want the output to go through a Netpbm tool.

Other Graphics Software

Netpbm contains primitive building blocks. It certainly is not a complete graphics library.

The first thing you will need to make use of any of these tools is a viewer. For the X inclined, there is xzgv. See

xloadimage and its extension xli are also common ways to display a graphic image in X.

ImageMagick is like a visual version of Netpbm. Using the X/Window system on Unix, you can do basic editing of images and lots of format conversions. The package does include at least some non-visual tools. Convert, Mogrify, Montage, and Animate are popular programs from the ImageMagick package. ImageMagick runs on Unix, Windows, Windows NT, Macintosh, and VMS.

The Gimp is a visual image editor for Unix and X, in the same category as the more famous, less capable, and much more expensive Adobe Photoshop, etc. for Windows. See

The file program looks at a file and tells you what kind of file it is. It recognizes most of the graphics formats with which Netpbm deals, so it is pretty handy for graphics work. Netpbm's anytopnm program depends on file. See

The Utah Raster Toolkit serves a lot of the same purpose as Netpbm, but without the emphasis on format conversions. This package is based on the RLE format, which you can convert to and from the Netpbm formats. gives some information on the Utah Raster Toolkit, but does not tell where to get it.

There are some Netpbm-like graphics tools distributed by the Army High Performance Computing Research Center at These operate directly on non-Netpbm format images, so they aren't included in the Netpbm package. However, you can use them with any image format by using the Netpbm format converters.

Ivtools is a suite of free X Windows drawing editors for Postscript, Tex, and web graphics production, as well as an embeddable and extendable vector graphic shell. It uses the Netpbm facilities. See

Ilib is a C subroutine library with functions for adding text to an image (as you might do at a higher level with pbmtext, pnmcomp, etc.). It works with Netpbm input and output. Find it at Netpbm also includes character drawing functions in the libppm library, but they do not have as fancy font capabilities (see ppmlabel for an example of use of the Netpbm character drawing functions).

GD is a library of graphics routines that is part of PHP. It has a subset of Netpbm's functions and has been found to resize images more slowly and with less quality.

pnm2ppa converts to HP's "Winprinter" format (for HP 710, 720, 820, 1000, etc). It is a superset of Netpbm's pbmtoppa and handles, notably, color. However, it is more of a printer driver than a Netpbm-style primitive graphics building block. See

The program morph morphs one image into another. It uses Targa format images, but you can use tgatoppm and ppmtotga to deal with that format. You have to use the graphical (X/Tk) Xmorph to create the mesh files that you must feed to morph. morph is part of the Xmorph package. See

To create an animated GIF, or extract a frame from one, use gifsicle. gifsicle converts between animated GIF and still GIF, and you can use ppmtogif and giftopnm to connect up to all the Netpbm utilities. See

To convert an image of text to text (optical character recongition - OCR), use gocr (think of it as an inverse of pbmtext). See contains a PNG test suite -- a whole bunch of PNG images exploiting the various features of the PNG format.

Another version of pnmtopng/pngtopnm is at The version in Netpbm was actually based on that package a long time ago, and you can expect to find better exploitation of the PNG format, especially recent enhancements, in that package. It may be a little less consistent with the Netpbm project and less exploitive of recent Netpbm format enhancements, though.

jpegtran Does some of the same transformations as Netpbm is famous for, but does them specifically on JPEG files and does them without loss of information. By contrast, if you were to use Netpbm, you would first decompress the JPEG image to Netpbm format, then transform the image, then compress it back to JPEG format. In that recompression, you lose a little image information because JPEG is a lossy compression. jpegtran comes with the Independent Jpeg Group's ( JPEG library.

Some tools to deal with EXIF files (see also Netpbm's jpegtopnm and pnmtojpeg): To dump (interpret) an EXIF header: Exifdump (( or Jhead (

A Python EXIF library and dumper:

Latex2html converts Latex document source to HTML document source. Part of that involves graphics, and Latex2html uses Netpbm tools for some of that. But Latex2html through its history has had some rather esoteric codependencies with Netpbm. Older Latex2html doesn't work with current Netpbm. Latex2html-99.2beta8 works, though.

Other Graphics Formats

People never seem to tire of inventing new graphics formats, often completely redundant with pre-existing ones. Netpbm cannot keep up with them. Here is a list of a few that we know Netpbm does not handle (yet).

CAL (originated by US Department Of Defense, favored by architects).

array formats dx, general, netcdf, CDF, hdf, cm


Windows Meta File (.WMF). Libwmf converts from WMF to things like Latex, PDF, PNG. Some of these can be input to Netpbm.

Microsoft Word, RTF. Microsoft keeps a proprietary hold on these formats. Any software you see that can handle them is likely to cost money.



Netpbm has a long history, starting with Jef Poskanzer's Pbmplus package in 1988. The file HISTORY in the Netpbm source code contains a historical overview as well as a detailed history release by release.


Netpbm is based on the Pbmplus package by Jef Poskanzer, first distributed in 1988 and maintained by him until 1991. But the package contains work by countless other authors, added since Jef's original work. In fact, the name is derived from the fact that the work was contributed by people all over the world via the Internet, when such collaboration was still novel enough to merit naming the package after it.

Bryan Henderson has been maintaining Netpbm since 1999. In addition to packaging work by others, Bryan has also written a significant amount of new material for the package.