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, pam-
scale(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 cre-
ate 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\Source-
forge 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 charac-
teristic of Netpbm programs is that they are simple, fundamental build-
ing 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 any-
thing 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 system can. There may be exceptions where the programs
use external libraries (The JPEG library, 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 library, 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 is-
sued to Standard Error. (To be precise, this only works to the
extent that the program in question implements the Netpbm conven-
tion of issuing all informational messages via the pm_message()
service of the Netpbm library).
-version
Instead of doing anything else, report the version of the lib-
netpbm 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 gen-
erates PAM output.
This option was introduced in Netpbm 10.10 (October 2002). From
Netpbm 10.32 (February 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, al-
ready 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 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. Specifically, 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 for-
mat 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 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 pix-
els 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 ]8;;#impconv\ Implied Format Conversion]8;;\
.
Programs that have "pnm" in their names read PBM, PGM, and PPM but un-
like "ppm" programs, they distinguish between those formats and their
function depends on the format. For example, 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 input 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 individ-
ual 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 exam-
ple, ppmhist can analyze a PAM image of tuple type RGB (i.e. a color im-
age) 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 format.
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 equiva-
lent 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 im-
age 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 read-
ing 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 transparency mask.
Another means of representing transparency information has recently de-
veloped in Netpbm, using PAM images. In spite of the argument given
above that Netpbm formats should be too simple to have transparency in-
formation 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 output 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 rec-
ognize and generate a PAM image with tuple type RGB_ALPHA or
GRAYSCALE_ALPHA, which contains a plane for the transparency informa-
tion. 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 because the Netpbm package
contains converters for all the popular graphics formats, if your pro-
gram reads and writes the Netpbm formats, you can use it with any for-
mats.
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-config is really a configuration file, like those you typi-
cally 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 command to find out where the Netpbm data files are.
netpbm-config is the only file that must be installed in a standard di-
rectory (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 po-
sition 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 occupies in the Netpbm image file format.
The older programs (most of Netpbm) use 12 bytes per pixel. This is
true even for a PBM image, for which it only really takes one bit to to-
tally describe the pixel. Netpbm does this expansion to make implement-
ing 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 little differently. These functions are designed to
handle generic tuples with a variable numbers 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 accessing memory.
This means that the consequences of whether a program works from the im-
age 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 operating system's file cache, than in Netpbm's in-mem-
ory 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 pro-
grams do that. But some files can't be read multiple times. In partic-
ular, 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 tempo-
rary file multiple times.
A few Netpbm programs use an in-memory format that is just one bit per
pixel. These are programs that convert between PBM and a format that
has a raster format very much like PBM's. In this case, it would actu-
ally 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 sys-
tem with a large network of disks, especially 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 library use. The programs never depend on particular
features existing (assuming they're compiled 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 building 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 exponentially related to light intensity. The programs
have to keep the intermediate intensity values in floating point in or-
der 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 image), pamcomp(1) (overlay an
image over another one), and pamditherbw(1) (Make a black and white im-
age that approximates a grayscale image).
The Netpbm image formats use 16 bit integers. The Netpbm code uses "un-
signed int" size integers 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 transforma-
tions, but you can extend it with plugins.
A particularly easy way to write a Gimp plugin is to write a Netpbm pro-
gram (remember that a fundamental mission of Netpbm is make writing im-
age 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 pro-
gram that converts to a certain graphics 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 com-
plete 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 ba-
sic editing. convert, mogrify, montage, and animate are popular pro-
grams 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 driver li-
brary. You can find zgv at ]8;;ftp://ftp.ibiblio.org/pub/Linux/apps/graphics/viewers/svga\ftp://ftp.ibiblio.org/pub/Linux/apps/graph-
ics/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 Sys-
tem, captures the contents of an X window, in its own special image for-
mat, 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 frame-
buffer devices.
Visual Graphics Software
Visual graphics software is modern point-and-click software that dis-
plays 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 Win-
dow System. The package also contains ]8;;#othercmdline\command 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 contains 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 language.
You can easily run any Netpbm program from a C program with the pm_sys-
tem function from the Netpbm programming library, but that is less effi-
cient 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 im-
age (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 exam-
ple of use of the Netpbm character drawing functions).
]8;;http://www.pango.org/\Pango]8;;\ is another text rendering library, with an emphasis on interna-
tionalization.
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 sub-
set of Netpbm's functions 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 between 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 exploiting 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 package. It may be a little
less consistent with the Netpbm project and less exploitive of recent
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 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. Of
course, only a few kinds of lossless transformation are possible. jpeg-
tran 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/exifdump.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 Architec-
ture): ]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 superset of Netpbm's pbmtoppa and handles, no-
tably, 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 in-
cludes viewers, browser plugins, decoders, simple encoders, and utili-
ties. The encoders and decoders can convert between 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 related 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 document 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 con-
verts from Postscript and PDF to PNM. It effectively renders the docu-
ment 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 program 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 quintessential 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 option) is useful.
Other software from Adobe, available for purchase, interprets and cre-
ates 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, including 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 history 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 de-
pends 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 without the emphasis on format con-
versions. This package is based on the RLE format, which you can con-
vert to and from the Netpbm formats.
Ivtools is a suite of free X Window System drawing editors for Post-
script, 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@ir.isas.jaxa.jp> has written a free c/Fortran
graphic library: ]8;;https://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 convert 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 com-
pletely 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, especially formats typically used with Windows pro-
grams. ImageMagick is probably the most used free image format con-
verter 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 losing any information.
CharLS is a programming library for JPEG-LS.
• Lossless JPEG is a similarly lossless variation of JPEG. It pre-
dates every other lossless JPEG variation, but had only brief in-
terest. 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 compression 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 compression, as used in all modern realtime graph-
ics applications. Besides Windows-based tools, there is a Gimp
plugin for this format.
• DjVu is a web-centric format and software platform for distribut-
ing documents and images. 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, be-
cause it downloads faster, displays and renders faster, looks
nicer on a screen, and consumes less client resources than com-
peting 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 archi-
tects). It is described in this 1997 listing of graphics for-
mats: ]8;;http://www.faqs.org/faqs/graphics/fileformats-faq/part3/\ http://www.faqs.org/faqs/graphics/fileformats-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, Radi-
ance 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 documented by IBM: ]8;;http://publibz.boulder.ibm.com/epubs/pdf/c3168055.pdf\ Data Stream and Object Archi-
tectures: Image Object Content Ar- chitecture 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 rep-
resentation 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 distrib-
uted 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.
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)
Generated by dwww version 1.16 on Tue Dec 16 03:55:55 CET 2025.