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User manual for Netpbm(1) General Commands Manual User manual for Netpbm(1)

NAME
netpbm - netpbm library overview

Overview Of Netpbm
Netpbm is a package of graphics programs and a programming library.

There are over 330 separate programs in the package, most of which have "pbm", "pgm", "ppm",
"pam", or "pnm" in their names. For example, pamscale(1) and giftopnm(1).

For example, you might use pamscale to shrink an image by 10%. Or use pamcomp 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.

Netpbm is an open source software package, distributed via the ]8;;http://sourceforge.net/projects/netpbm\Sourceforge netpbm project]8;;\ .

Table Of Contents
•

]8;;#overview\Overview Of Netpbm]8;;\

•

]8;;#formats\The Netpbm Formats]8;;\

•

]8;;#impconv\Implied Format Conversion]8;;\

•

]8;;#transparency\Netpbm and Transparency]8;;\

•

]8;;#programs\The Netpbm Programs]8;;\

•

]8;;#commonoptions\Common Options]8;;\

•

]8;;#directory\Directory]8;;\

•

]8;;#prognotes\How To Use The Programs]8;;\

•

]8;;#libnetpbm\The Netpbm Library]8;;\

•

]8;;#config\netpbm-config]8;;\

•

]8;;#memoryusage\Memory Usage]8;;\

•

]8;;#cpuusage\CPU Usage]8;;\

•

]8;;#netpbmforgimp\Netpbm For Gimp]8;;\

•

]8;;#companion\Companion Software]8;;\

•

]8;;#phpnetpbm\PHP-NetPBM]8;;\

•

]8;;#othersoftware\Other Graphics Software]8;;\

•

]8;;#viewers\Image Viewers]8;;\

•

]8;;#capturers\Image Capturers]8;;\

•

]8;;#visual\Visual Graphics Software]8;;\

•

]8;;#programmingtools\Programming Tools]8;;\

•

]8;;#toolsforformats\Tools For Specific Graphics Formats]8;;\

•

]8;;#document\Document/Graphics Software]8;;\

•

]8;;#otherothersoftware\Other]8;;\

•

]8;;#otherfmt\Other Graphics Formats]8;;\

•

]8;;#history\History]8;;\

•

]8;;#author\Author]8;;\

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 and do not seek input from a user. The
only programs that display graphics at all are the very primitive display programs pamx and
ppmsvgalib, and they don't do anything but that.

Each of these programs has its own manual, as linked in the directory below.

The Netpbm programs can read and write files greater than 2 GiB wherever the underlying sys‐
tem can. There may be exceptions where the programs use external libraries (The JPEG li‐
brary, etc.) to access files and the external library does not have large file capability.
Before Netpbm 10.15 (April 2003), no Netpbm program could read a file that large.

Common Options
There are a few options that are present on all programs that are based on the Netpbm li‐
brary, including virtually all Netpbm programs. These are not mentioned in the individual
manuals for the programs.

You can use two hyphens instead of one on these options if you like.

-quiet
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() ser‐
vice of the Netpbm library).

-version
Instead of doing anything else, report the version of the libnetpbm 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 library are installed at
the same time, so this tells you the version of the program and all the other Netpbm
files it uses as well.

-plain If the program generates an image in PNM format, generate it in the "plain" (aka
"ascii") version of the format, as opposed to the "raw" (aka "binary") version.

Note that the other Netpbm format, PAM, does not have plain and raw versions, so this
option has no effect on a program that generates PAM output.

This option was introduced in Netpbm 10.10 (October 2002). From Netpbm 10.32 (Febru‐
ary 2006) through Netpbm 10.62 (March 2013), the option is invalid with a program that
generates PAM output (instead of ignoring the option, the program fails).

Directory
Here is a complete list of all the Netpbm programs (with links to their manuals):

Netpbm program directory(1)

How To Use The Programs
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 Stan‐
dard Output. This is for flexibility, since you so often have to pipeline many tools to‐
gether.

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 pngtopam $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
| perl -ne 'chomp;
print yuvtoppm $_ | pambrighten -value +100 | ppmtoyuv >tmp$$.yuv;
mv tmp$$.yuv $_
'
| 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 the hypothetical program printcmyk takes the filename of a Tiff CMYK file as input and
what you have is a PNG file abc.png.

Try:
printcmyk <({ pngtopam 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.

The Netpbm Formats
All of the programs work with a set of graphics formats called the "netpbm" formats. Specif‐
ically, these formats are pbm(1), pgm(1), ppm(1), and pam(1).

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 an‐
other non-Netpbm format. Netpbm has converters for about 100 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 for‐
mat, 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 rep‐
resent 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
]8;;#impconv\ Implied Format Conversion]8;;\ .

Programs that have "pnm" in their names read PBM, PGM, and PPM but unlike "ppm" programs,
they distinguish between those formats and their function depends on the format. For exam‐
ple, pnmtopng(1) creates a black and white PNG output image if its input is PBM or PGM, but a
color PNG output image if its input is PPM. And pnmrotate produces an output image of the
same format as the input. A hypothetical ppmrotate program would also read all three PNM in‐
put formats, but would see them all as PPM and would always generate PPM output.

Programs that have "pam" in their names read all the Netpbm formats: PBM, PGM, PPM, and PAM.
They sometimes treat them all as if they are PAM, using an implied conversion, but often they
recognize the individual formats and behave accordingly, like a "pnm" program does. See ]8;;#impconv\Im‐
plied Format Conversion]8;;\ .

Finally, there are subformats of PAM that are equivalent to PBM, PGM, and PPM respectively,
and Netpbm programs designed to read PBM, PGM, and/or PPM see those PAM images as if they
were the former. For example, ppmhist can analyze a PAM image of tuple type RGB (i.e. a
color image) as if it were PPM.

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 for‐
mat.

The formats are described in the specifications of pbm(1), pgm(1), ppm(1), and pam(1).

Implied Format Conversion
A program that uses the PGM library subroutines 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. note: This sometimes confuses people who are looking at the formats at a
lower layer than they ought to be because a zero value in a PBM raster means white, while a
zero value in a PGM raster means black.

A program that uses the PPM library subroutines 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.

A program that uses the PAM library subroutines to read an image can read a PBM, PGM, or PPM
image as well as a PAM image. The program sees a PBM image as if it were the equivalent PAM
image with tuple type BLACKANDWHITE. It sees a PGM image as if it were the equivalent PAM
image with tuple type GRAYSCALE. It sees a PPM image as if it were the equivalent PAM image
with tuple type RGB. But the program actually can see deeper if it wants to. It can tell
exactly which format the input was and may respond accordingly. For example, a PAM program
typically produces output in the same format as its input.

A program that uses the PGM library subroutines to read an image can read a PAM image as well
a PGM image, if the PAM is a grayscale or black and white visual image. That canonically
means the PAM has a depth of 1 and a tuple type of GRAYSCALE or BLACKANDWHITE, but most
Netpbm programs are fairly liberal and will take any PAM at all, ignoring all but the first
plane.

There is a similar implied conversion for PPM library subroutines reading PAM. There is
nothing similar for PBM, so if you need for a PBM program to read a PAM image, run it through
pamtopnm.

Netpbm and Transparency
In many graphics formats, 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 an
opaqueness value. See pgm(1). pamcomp(1) is an example of a program that uses a PGM trans‐
parency mask.

Another means of representing transparency information has recently developed in Netpbm, us‐
ing PAM images. In spite of the argument given above that Netpbm formats should be too sim‐
ple to have transparency information built in, it turns out to be extremely inconvenient to
have to carry the transparency information around separately. This is primarily because Unix
shells don't provide easy ways to have networks of pipelines. You get one input and one out‐
put from each program in a pipeline. So you'd like to have both the color information and
the transparency information for an image in the same pipe at the same time.

For that reason, some new (and recently renovated) Netpbm programs recognize and generate a
PAM image with tuple type RGB_ALPHA or GRAYSCALE_ALPHA, which contains a plane for the trans‐
parency information. See the PAM specification(1).

The Netpbm Library
The Netpbm programming library, libnetpbm(1), makes it easy to write programs that manipulate
graphic images. Its main function is to read and write files in the Netpbm formats, and be‐
cause 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 library also contain some utility functions, such as character drawing and RGB/YCrCb
conversion.

The library has the conventional C linkage. Virtually all programs in the Netpbm package are
based on the Netpbm library.

netpbm-config
In a standard installation of Netpbm, there is a program named netpbm-config in the regular
program search path. We don't consider this a Netpbm program -- it's just an ancillary part
of a Netpbm installation. This program tells you information about the Netpbm installation,
and is intended to be run by other programs that interface with Netpbm. In fact, netpbm-con‐
fig is really a configuration file, like those you typically see in the /etc/ directory of a
Unix system.

Example:
$netpbm-config --datadir
/usr/local/netpbm/data

If you write a program that needs to access a Netpbm data file, it can use such a shell com‐
mand to find out where the Netpbm data files are.

netpbm-config is the only file that must be installed in a standard directory (it must be in
a directory that is in the default program search path). You can use netpbm-config as a
bootstrap to find all the other Netpbm files.

There is no detailed documentation of netpbm-config. If you're in a position to use it, you
should have no trouble reading the file itself to figure out how to use it.

Memory Usage
An important characteristic that varies among graphics software is how much memory it uses,
and how. Does it read an entire image into memory, work on it there, then write it out all
at once? Does it read one and write one pixel at a time? In Netpbm, it differs from one
program to the next, but there are some generalizations we can make.

Most Netpbm programs keep one row of pixels at a time in memory. Such a program reads a row
from an input file, processes it, then writes a row to an output file. Some programs execute
algorithms that can't work like that, so they keep a small window of rows in memory. Others
must keep the entire image in memory. If you think of what job the program does, you can
probably guess which one it does.

When Netpbm keeps a pixel in memory, it normally uses a lot more space for it than it occu‐
pies in the Netpbm image file format.

The older programs (most of Netpbm) use 12 bytes per pixel. This is true even for a PBM im‐
age, for which it only really takes one bit to totally describe the pixel. Netpbm does this
expansion to make implementing the programs easier -- it uses the same format regardless of
the type of image.

Newer programs use the "pam" family of library functions internally, which use memory a lit‐
tle differently. These functions are designed to handle generic tuples with a variable num‐
bers of planes, so no fixed size per-tuple storage is possible. A program of this type uses
4 bytes per sample (a tuple is composed of samples), plus a pointer (4-8 bytes) per tuple.
In a graphic image, a tuple is a pixel. So an ordinary color image takes 16-20 bytes per
pixel.

When considering memory usage, it is important to remember that memory and disk storage are
equivalent in two ways:

• Memory is often virtual, backed by swap space on disk storage. So accessing memory
may mean doing disk I/O.

• Files are usually cached and buffered, so that accessing a disk file may just mean ac‐
cessing memory.

This means that the consequences of whether a program works from the image file or from a
memory copy are not straightforward.

Note that an image takes a lot less space in a Netpbm format file, and therefore in an oper‐
ating system's file cache, than in Netpbm's in-memory format. In non-Netpbm image formats,
the data is even smaller. So reading through an input file multiple times instead of keeping
a copy in regular memory can be the best use of memory, and many Netpbm programs do that.
But some files can't be read multiple times. In particular, you can't rewind and re-read a
pipe, and a pipe is often the input for a Netpbm program. Netpbm programs that re-read files
detect such input files and read them into a temporary file, then read that temporary file
multiple times.

A few Netpbm programs use an in-memory format that is just one bit per pixel. These are pro‐
grams that convert between PBM and a format that has a raster format very much like PBM's.
In this case, it would actually make the program more complicated (in addition to much
slower) to use Netpbm's generic 12 byte or 8 byte pixel representation.

By the way, the old axiom that memory is way faster than disk is not necessarily true. On
small systems, it typically is true, but on a system with a large network of disks, espe‐
cially with striping, it is quite easy for the disk storage to be capable of supplying data
faster than the CPU can use it.

CPU Usage
People sometimes wonder what CPU facilities Netpbm programs and the Netpbm programming li‐
brary use. The programs never depend on particular features existing (assuming they're com‐
piled properly), but the speed and cost of running a program varies depending upon the CPU
features.

Note that when you download a binary that someone else compiled, even though it appears to be
compiled properly for your machine, it may be compiled improperly for that machine if it is
old, because the person who compiled it may have chosen to exploit features of newer CPUs in
the line. For example, an x86 program may be compiled to use instructions that are present
on an 80486, but not on an 80386. You would probably not know this until you run the program
and it crashes.

But the default build options almost always build binaries that are as backward compatible
with old CPUs as possible. An exception is a build for a 64 bit x86 CPU. While the builder
could build a program that runs on a 32 bit x86, it does not do so by default. A default
build builds a program will not run on an older 32-bit-only x86 CPU.

One common build option is to use MMX/SSE operands with x86 CPUs. Those are not available on
older x86 CPUs. The builder by default does not generate code that uses MMX/SSE when build‐
ing for 32 bit x86 CPUs, but does when building for 64 bit x86.

One area of particular importance is floating point arithmetic. The Netpbm image formats are
based on integers, and Netpbm arithmetic is done with integers where possible. But there is
one significant area that is floating point: programs that must deal with light intensity.
The Netpbm formats use integers that are proportional to brightness, and brightness is expo‐
nentially related to light intensity. The programs have to keep the intermediate intensity
values in floating point in order not to lose precision. And the conversion (gamma function)
between the two is heavy-duty floating point arithmetic.

Programs that mix pixels together have to combine light intensity, so they do heavy floating
point. Three of the most popular Netpbm programs do that: pamscale(1) (shrink/expand an im‐
age), pamcomp(1) (overlay an image over another one), and pamditherbw(1) (Make a black and
white image that approximates a grayscale image).

The Netpbm image formats use 16 bit integers. The Netpbm code uses "unsigned int" size inte‐
gers to work with them.

Netpbm For Gimp
The Gimp is a visual image editor for Unix and X, so it does the kinds of things that Netpbm
does, but interactively in a user-friendly way. The Gimp knows a variety of graphics file
formats and image transformations, but you can extend it with plugins.

A particularly easy way to write a Gimp plugin is to write a Netpbm program (remember that a
fundamental mission of Netpbm is make writing image manipulation programs easy) and then use
]8;;http://netpbm2gimp.sourceforge.net/\netpbm2gimp]8;;\ to compile that same source code into a Gimp plugin.

You can turn a program that converts from a certain graphics file format to Netpbm format
into a Gimp load plugin. Likewise, you can turn a program that converts to a certain graph‐
ics format from Netpbm format into a Gimp store plugin. Finally, a program that transforms
images in Netpbm format can become a process plugin.

And the netpbm2gimp project has already packaged for you a few hundred of the Netpbm programs
as Gimp plugins. With this package you can, for example, edit an image in any of the arcane
graphics file formats that Netpbm understands but no other image editor in existence does.

Companion Software
PHP-NetPBM
If you're using Netpbm to do graphics for a website, you can invoke the Netpbm programs from
a PHP script. To make this even easier, check out ]8;;http://sourceforge.net/projects/phpnetpbm\PHP-NetPBM]8;;\ , a PHP class that interacts
with Netpbm. Its main goal is to decrease the pain of using Netpbm when working with images
in various formats. It includes macro commands to perform manipulations on many files.

I can't actually recommend PHP-NetPBM. I spent some time staring at it and was unable to
make sense of it. Some documentation is in fractured English and other is in an unusual
character set. But a PHP expert might be able to figure it out and get some use out of it.

Other Graphics Software
Netpbm contains primitive building blocks. It certainly is not a complete graphics software
library.

Command Line Programs
ImageMagick does many of the same things - mainly the more popular ones - that Netpbm does,
including conversion between popular formats and basic editing. convert, mogrify, montage,
and animate are popular programs from the ImageMagick package. ImageMagick runs on Unix,
Windows, Windows NT, Macintosh, and VMS.

ImageMagick also contains the program display, which is a ]8;;#viewers\viewer]8;;\ and ]8;;#visual\visual editor]8;;\ .

Image Viewers
The first thing you will want to make use of any of these tools is a viewer. (On GNU/Linux,
you can use Netpbm's pamx or ppmsvgalib in a pinch, but it is pretty limiting). zgv is a
good full service viewer to use on a GNU/Linux system with the SVGALIB graphics display dri‐
ver library. You can find zgv at ]8;;ftp://ftp.ibiblio.org/pub/Linux/apps/graphics/viewers/svga\ftp://ftp.ibiblio.org/pub/Linux/apps/graphics/viewers/svga]8;;\
.

zgv even has a feature in it wherein you can visually crop an image and write an output file
of the cropped image using pamcut(1).

See the -s option to zgv.

For the X inclined, there is also xzgv.

xwud (X Window Undump) is a classic application program in the X Window System that displays
an image in an X window. It takes the special X Window Dump format as input; you can use
Netpbm's pnmtoxwd(1) to create it. You're probably better off just using Netpbm's pamx(1).

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

gqview is a more modern X-based image viewer.

qiv is a small, very fast viewer for X.

To play mpeg movies, such as produced by ppmtompeg, try mplayer(1) or ]8;;http://sourceforge.net/projects/xine\xine]8;;\ .

See ]8;;ftp://metalab.unc.edu/pub/Linux/apps/graphics/viewers/X\ftp://metalab.unc.edu/pub/Linux/apps/graphics/viewers/X]8;;\ .

Image Capturers
xwd (X Window Dump), a classic application program in the X Window System, captures the con‐
tents of an X window, in its own special image format, called X Window Dump File. You can
use Netpbm's xwdtopnm(1) to turn it into something more useful.

]8;;http://www.rcdrummond.net/fbdump/\fbdump]8;;\ Capturers the current contents of a video display on the local computer and generates
a PPM image of it. It works with Linux framebuffer devices.

Visual Graphics Software
Visual graphics software is modern point-and-click software that displays an image and lets
you work on it and see the results as you go. This is fundamentally different from what
Netpbm programs do.

xv is a very old and very popular simple image editor in the Unix world. It does not have
much in the way of current support, or maintenance, though.

Gimp is a visual image editor for Unix and the X Window System, in the same category as the
more famous, less capable, and much more expensive Adobe Photoshop, etc. for Windows. See
]8;;http://www.gimp.org\http://www.gimp.org]8;;\ . And you can add most of Netpbm's function to Gimp using ]8;;http://netpbm2gimp.sourceforge.net/\Netpbm2gimp]8;;\ .

ImageMagick contains the program display, which is another visual image editor. It has fewer
functions than Gimp. This program uses the X Window System. The package also contains ]8;;#othercmdline\com‐
mand line]8;;\ graphics programs.

Electric Eyes, kuickshow, and gthumb are also visual editors for the X/Window system, and
KView and gwenview are specifically for KDE.

Programming Tools
If you're writing a program in C to draw and manipulate images, check out ]8;;https://github.com/libgd/libgd\gd]8;;\ . Netpbm con‐
tains a C library for drawing images (libnetpbm's "ppmd" routines), but it is not as capable
or documented as gd. There are wrapper libraries available for Perl, PHP, and other lan‐
guage.

You can easily run any Netpbm program from a C program with the pm_system function from the
Netpbm programming library, but that is less efficient than gd functions that do the same
thing.

]8;;http://cairographics.org/\Cairo]8;;\ is similar.

Ilib is a C subroutine library with functions for adding text to an image (as you might do at
a higher level with pbmtext, pamcomp, etc.). It works with Netpbm input and output. Find it
at ]8;;http://www.k5n.us/Ilib.php\k5n.us]8;;\ . Netpbm also includes character drawing functions in the libnetpbm(1) library,
but they do not have as fancy font capabilities (see ppmdraw(1) for an example of use of the
Netpbm character drawing functions).

]8;;http://www.pango.org/\Pango]8;;\ is another text rendering library, with an emphasis on internationalization.

Pango and Cairo complement each other and work well together.

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

Tools For Specific Graphics Formats
mencode, which is part of the mplayer(1) package, creates movie files. It's like a much more
advanced version of ppmtompeg(1), without the Netpbm building block simplicity.

]8;;http://mjpeg.sourceforge.net\MJPEGTools]8;;\ is software for dealing with the MJPEG movie format.

To create an animated GIF, or extract a frame from one, use gifsicle. gifsicle converts be‐
tween animated GIF and still GIF, and you can use pamtogif and giftopnm to connect up to all
the Netpbm utilities. See ]8;;http://www.lcdf.org/gifsicle\http://www.lcdf.org/gifsicle]8;;\ .

To convert an image of text to text (optical character recognition - OCR), use gocr (think of
it as an inverse of pbmtext). See ]8;;http://jocr.sourceforge.net/\http://jocr.sourceforge.net/]8;;\ .

]8;;http://schaik.com/pngsuite\http://schaik.com/pngsuite]8;;\ contains a PNG test suite -- a whole bunch of PNG images ex‐
ploiting the various features of the PNG format.

Other versions of Netpbm's pnmtopng/pngtopam are at http://www.schaik.com/png/pnmtopng.html"
(1).

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 pack‐
age. It may be a little less consistent with the Netpbm project and less exploitive of re‐
cent Netpbm format enhancements, though.

]8;;http://pngwriter.sourceforge.net\pngwriter]8;;\ is a C++ library for creating PNG images. With it, you plot an image pixel by
pixel. You can also render text with the FreeType2 library.

jpegtran Does some of the same transformations as Netpbm is famous for, but does them specif‐
ically 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. Of course, only a few kinds of lossless
transformation are possible. jpegtran comes with the Independent JPEG Group's (
]8;;http://www.ijg.org\http://www.ijg.org)]8;;\ JPEG library.

Some tools to deal with EXIF files (see also Netpbm's jpegtopnm(1) and pnmtojpeg(1)):

To dump (interpret) an EXIF header: Exifdump (( ]8;;http://www.math.u-psud.fr/~bousch/exifdump.py\http://www.math.u-psud.fr/~bousch/exif‐
dump.py)]8;;\ ) or ]8;;http://www.sentex.net/~mwandel/jhead\Jhead]8;;\ .

A Python EXIF library and dumper: ]8;;http://pyexif.sourceforge.net.\http://pyexif.sourceforge.net.]8;;\

Here's some software to work with IOCA (Image Object Content Architecture): ]8;;http://www.forminnovation.com\ImageToolbox]8;;\
($2500, demo available). This can convert from TIFF -> IOCA and back again.

]8;;https://ameri-imager.software.informer.com/\Ameri-Imager]8;;\ is an image and video editor. ($40 Windows only).

pnm2ppa converts to HP's "Winprinter" format (for HP 710, 720, 820, 1000, etc). It is a su‐
perset 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 ]8;;http://sourceforge.net/projects/pnm2ppa\The Pnm2ppa /Sourceforge
Project]8;;\

DjVuLibre is a package of software for using the DjVu format. It includes viewers, browser
plugins, decoders, simple encoders, and utilities. The encoders and decoders can convert be‐
tween DjVu and PNM. See ]8;;http://djvu.sourceforge.net/\ the DjVu website.]8;;\

Document/Graphics Software
There is a large class of software that does document processing, and that is somewhat re‐
lated to graphics because documents contain graphics and a page of a document is for many
purposes a graphic image. Because of this slight intersection with graphics, I cover docu‐
ment processing software here briefly, but it is for the most part beyond the scope of this
document.

First, we look at where Netpbm meets document processing. pstopnm converts from Postscript
and PDF to PNM. It effectively renders the document into images of printed pages. pstopnm
is nothing but a convenient wrapper for ]8;;http://www.ghostscript.com/\Ghostscript]8;;\ , and in particular Netpbm-format device
drivers that are part of it. pnmtops and pbmtoepsi convert a PNM image to a Postscript pro‐
gram for printing the image. But to really use PDF and Postscript files, you generally need
more complex document processing software.

Adobe invented Postscript and PDF and products from Adobe are for many purposes the quintes‐
sential Postscript and PDF tools.

Adobe's free Acrobat Reader displays PDF and converts to Postscript. The Acrobat Reader for
unix has a program name of "acroread" and the -toPostScript option (also see the -level2 op‐
tion) is useful.

Other software from Adobe, available for purchase, interprets and creates Postscript and PDF
files. "Distill" is a program that converts Postscript to PDF.

]8;;http://www.foolabs.com/xpdf/\xpdf]8;;\ also reads PDF files.

GSview, ghostview, gv, ggv, and kghostview are some other viewers for Postscript and PDF
files.

The program ps2pdf, part of Ghostscript, converts from Postscript to PDF.

bmpp(1) converts from Netpbm and other formats to PDF.

Two packages that produce more kinds of Encapsulated Postscript than the Netpbm programs, in‐
cluding compressed kinds, are bmpp(1) and ]8;;http://imgtops.sourceforge.net/\imgtops]8;;\ .

dvips converts from DVI format to Postscript. DVI is the format that Tex produces. Netpbm
can convert from Postscript to PNM. Thus, you can use these in combination to work with
Tex/Latex documents graphically.

]8;;http://wvware.sourceforge.net\wvware]8;;\ converts a Microsoft Word document (.doc file) to various other formats. While the
web page doesn't seem to mention it, it reportedly can extract an embedded image in a Word
document as a PNG.

]8;;http://www.verypdf.com/artprint\Document Printer]8;;\ converts various print document formats (Microsoft Word, PDF, HTML, etc.)
to various graphic image formats. ($38, Windows only).

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 his‐
tory has had some rather esoteric codependencies with Netpbm. Older Latex2html doesn't work
with current Netpbm. Latex2html-99.2beta8 works, though.

Other
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(1) program depends on file. See ]8;;ftp://ftp.astron.com/pub/file\ftp://ftp.astron.com/pub/file]8;;\ .

The Utah Raster Toolkit from the Geometric Design And Computation group in the Department of
Computer Science at University of Utah serves a lot of the same purpose as Netpbm, but with‐
out the emphasis on format conversions. This package is based on the RLE format, which you
can convert to and from the Netpbm formats.

Ivtools is a suite of free X Window System 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 ]8;;http://www.ivtools.org\http://www.ivtools.org]8;;\ .

Chisato Yamauchi <cyamauch AT ir.jp> has written a free c/Fortran graphic library:
]8;;http://www.ir.isas.jaxa.jp/~cyamauch/eggx_procall/\EGGX/ProCall]8;;\ . He says he tried to write the ultimate easy-to-use graphic kit for X. It is
for drawing upon an X11 window, but for storage, it outputs PPM. He suggests Netpbm to con‐
vert to other formats.

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 ]8;;http://xmorph.sourceforge.net/\http://xmorph.sourceforge.net/]8;;\ .

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).

Various commercial Windows software handles dozens of formats that Netpbm does not, espe‐
cially formats typically used with Windows programs. ImageMagick is probably the most used
free image format converter and it also handles lots of formats Netpbm does not.

• WebP was announced by Google in October 2010 as a more compressed replacement for JFIF
(aka JPEG) on the web.

• JPEG-LS is similar to JFIF (aka JPEG) except that it is capable of representing all
the information in any raster image, so you could convert from, say, PNM, without los‐
ing any information. CharLS is a programming library for JPEG-LS.

• Lossless JPEG is a similarly lossless variation of JPEG. It predates every other
lossless JPEG variation, but had only brief interest. You can find code for encoding
and decoding Lossless JPEG on ]8;;https://github.com/thorfdbg/libjpeg\GitHub]8;;\ .

• JPEG XR offers greater dynamic range, a wider range of colors, and more efficient com‐
pression than JFIF (aka JPEG). Windows and Internet Explorer understand this format,
starting with Windows 7 and Internet Explorer 9, along with many other programs. This
format was previously known as Windows Media Photo and HD Photo.

• Direct Draw Surface (DDS)is the de facto standard wrapper format for S3 texture com‐
pression, as used in all modern realtime graphics applications. Besides Windows-based
tools, there is a Gimp plugin for this format.

• DjVu is a web-centric format and software platform for distributing documents and im‐
ages. Promoters say it is a good replacement for PDF, PS, TIFF, JFIF(JPEG), and GIF
for distributing scanned documents, digital documents, or high-resolution pictures,
because it downloads faster, displays and renders faster, looks nicer on a screen, and
consumes less client resources than competing formats.

For more information, see ]8;;http://djvu.sourceforge.net/\ the DjVu website.]8;;\

•

]8;;http://www.web3d.org/x3d/specifications/vrml\VRML (Virtual Reality Modelling Language)]8;;\

•

CALS (originated by US Department Of Defense, favored by architects). It is described
in this 1997 listing of graphics formats: ]8;;http://www.faqs.org/faqs/graphics/fileformats-faq/part3/\ http://www.faqs.org/faqs/graphics/filefor‐
mats-faq/part3/]8;;\ . CALS has at times been an abbreviation of various things, all of
which appear to be essentially the same format, but possibly slightly different:

• Computer Aided Logistics Support

• Computer Aided Acquisition and Logistics Support

• Continuous Acquisition and Life-cycle Support

• Commerce At Light Speed

The US Navy publishes ]8;;https://www.navsea.navy.mil/Home/Warfare-Centers/NSWC-Carderock/Resources/Technical-Information-Systems/IETMs/Specifications-Standards/CALS-Standards/\specs]8;;\ for it.

•

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

•

CGM+

• HDR formats OpenEXR, SGI TIFF LogLuv, floating point TIFF, Radiance RGBE

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

• Microsoft Word .doc format. Microsoft keeps a proprietary hold on this format. Any
software you see that can handle it is likely to cost money.

• RTF

•

DXF (AutoCAD)

•

IOCA (Image Object Content Architecture) The specification of this format is docu‐
mented by IBM: ]8;;http://publibz.boulder.ibm.com/epubs/pdf/c3168055.pdf\ Data Stream and Object Architectures: Image Object Content Architec‐
ture Reference]8;;\ . See above for software that processes this format.

• OpenEXR is an HDR format (like PFM(1)). See ]8;;http://www.openexr.com\ http://www.openexr.com]8;;\ .

• Xv Visual Schnauzer thumbnail image. This is a rather antiquated format used by the
Xv program. In Netpbm circles, it is best known for the fact that it is very similar
to Netpbm formats and uses the same signature ("P7") as PAM because it was developed
as sort of a fork of the Netpbm format specifications.

• YUV 4:2:0, aka YUV 420, and the similar YUV 4:4:4, YUV 4:2:2, YUV 4:1:1, YUV 4:1:1s,
and YUV 4:1:0. Video systems often use this.

•

]8;;http://en.wikipedia.org/wiki/MJPEG\MJPEG]8;;\ movie format.

• YUV4MPEG2 is a movie format whose purpose is similar to that of the Netpbm formats for
still images. You use it for manipulating movies, but not for storing or transmitting
them. The only known use of the format is with ]8;;http://mjpeg.sourceforge.net\MJPEGTools]8;;\ . The programs pnmtoy4m
and y4mtopnm (and predecessors ppmtoy4m and y4mtoppm) in that package convert between
a Netpbm stream and a YUV4MPEG2 stream. As you might guess from the name, YUV4MPEG2
uses a YUV representation of data, which is more convenient than the Netpbm formats'
RGB representation for working with data that is ultimately MPEG2.

History
Netpbm has a long history, starting with Jef Poskanzer's Pbmplus package in 1988. See the
Netpbm web site(1) for details.

The file doc/HISTORY in the Netpbm source code contains a detailed change history release by
release.

Author
Netpbm is based on the Pbmplus package by Jef Poskanzer, first distributed in 1988 and main‐
tained 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 con‐
tributed 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.

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/index.html

netpbm documentation 08 August 2020 User manual for Netpbm(1)