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<H1>Netpbm</H1>
Updated: 31 January 2014
<BR>
<?makeman .SH NAME ?>
<?makeman netpbm - netpbm library overview ?>
<H2 id="overview">Overview Of Netpbm</H2>
<?makeman .UN overview ?>
<P><B>Netpbm</B> is a package of graphics programs and a programming
library. <P> There are over 220 separate programs in the package,
most of which have "pbm", "pgm", "ppm",
"pam", or "pnm" in their names. For example,
<B><a href="pamscale.html">pamscale</a></B> and <B><a
href="giftopnm.html">giftopnm</a></B>.
<P>For example, you might use <B>pamscale</B> to shrink an image by
10%. Or use <B>pamcomp</B> to overlay one image on top of another.
Or use <B>pbmtext</B> to create an image of text. Or reduce the number
of colors in an image with <B>pnmquant</B>.
<p><b>Netpbm</b> is an open source software package, distributed via
the <a href="http://sourceforge.net/projects/netpbm">Sourceforge
<b>netpbm</b> project</a>.
<H2 id="index">Table Of Contents</H2>
<UL>
<LI><A HREF="#overview">Overview Of Netpbm</A>
<LI><A HREF="#formats">The Netpbm Formats</A>
<UL>
<LI><A HREF="#impconv">Implied Format Conversion</A>
<LI><A HREF="#transparency">Netpbm and Transparency</A>
</UL>
<LI><A HREF="#programs">The Netpbm Programs</A>
<UL>
<LI><A HREF="#commonoptions">Common Options</A>
<LI><A HREF="#directory">Directory</A>
<LI><A HREF="#prognotes">How To Use The Programs</A>
</UL>
<LI><A HREF="#libnetpbm">The Netpbm Library</A>
<LI><A HREF="#config">netpbm-config</A>
<li><a href="#memoryusage">Memory Usage</a>
<li><a href="#cpuusage">CPU Usage</a>
<LI><A HREF="#netpbmforgimp">Netpbm For Gimp</A>
<LI><A HREF="#companion">Companion Software</A>
<ul>
<LI><A HREF="#phpnetpbm">PHP-NetPBM</A>
</ul>
<LI><A HREF="#othersoftware">Other Graphics Software</A>
<ul>
<li><a href="#viewers">Image Viewers</a>
<li><a href="#capturers">Image Capturers</a>
<li><a href="#visual">Visual Graphics Software</a>
<li><a href="#programmingtools">Programming Tools</a>
<li><a href="#toolsforformats">Tools For Specific Graphics Formats</a>
<li><a href="#document">Document/Graphics Software</a>
<li><a href="#otherothersoftware">Other</a>
</ul>
<LI><A HREF="#otherfmt">Other Graphics Formats</A>
<LI><A HREF="#history">History</A>
<LI><A HREF="#author">Author</A>
</UL>
<H2 id="programs">The Netpbm Programs</H2>
<P>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 <b>pamx</b> and <b>ppmsvgalib</b>,
and they don't do anything but that.
<P>Each of these programs has its own manual, as linked in the
directory below.
<P>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.
<H3 id="commonoptions">Common Options</H3>
<P>
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.
<p>You can use two hyphens instead of one on these options if you like.
<DL COMPACT>
<DT><B>-quiet</B>
<DD> 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 <B>pm_message()</B>
service of the Netpbm library).
<DT><B>-version</B>
<DD>Instead of doing anything else, report the version of the
<B>libnetpbm</B> 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.
<DT><B>-plain</b>
<DD>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.
<P>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.
<p>
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).
</DL>
<H3 id="directory">Directory</H3>
<P>Here is a complete list of all the Netpbm programs (with links to
their manuals):
<p>
<a href="directory.html">Netpbm program directory</a>
<H3 id="prognotes">How To Use The Programs</H3>
<P>
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.
<P>
Often, you need to apply some conversion or edit to a whole bunch of files.
<P>
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.
<P>
Here is an example of a shell command to convert all your of PNG files
(named *.png) to JPEG files named *.jpg:
<pre>
for i in *.png; do pngtopam $i | ppmtojpeg >`basename $i .png`.jpg; done
</pre>
<P>
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:
<pre>
ls *.yuv
| perl -ne 'chomp;
print yuvtoppm $_ | ppmbrighten -v 100 | ppmtoyuv >tmp$$.yuv;
mv tmp$$.yuv $_
'
| sh
</pre>
<P>The tools <B>find</B> (with the <B>-exec</B> option) and
<B>xargs</B> are also useful for simple manipulation of groups of files.
<P>
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 <b>printcmyk</b>
takes the filename of a Tiff CMYK file as input and what you have is a
PNG file
<B>abc.png</B>.
Try:
<pre>
printcmyk <({ pngtopam abc.png | pnmtotiffcmyk ; })
</pre>
<P>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.
<H2 id="formats">The Netpbm Formats</H2>
<P>
All of the programs work with a set of graphics formats called the
"netpbm" formats. Specifically, these formats are
<A HREF="pbm.html">pbm</A>,
<A HREF="pgm.html">pgm</A>,
<A HREF="ppm.html">ppm</A>,
and
<A HREF="pam.html">pam</A>.
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 about 100
graphics formats, and as a package Netpbm lets you do more graphics
format conversions than any other computer graphics facility.
<P>
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.
<P>
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.
<P>
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 <a href="#impconv">
Implied Format Conversion</a>.
<P> 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 example, <B><a
href="pnmtopng.html">pnmtopng</a></B> 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 <B>pnmrotate</B> produces an output image of
the same format as the input. A hypothetical <B>ppmrotate</B> program
would also read all three PNM input formats, but would see them all as
PPM and would always generate PPM output.
<P>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 <a href="#impconv">Implied Format Conversion</a>.
<p>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, <b>ppmhist</b> can analyze a PAM image of tuple type
RGB (i.e. a color image) as if it were PPM.
<P> 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.
<P>The formats are described in the specifications of
<B><A HREF="pbm.html">pbm</A></B>,
<B><A HREF="pgm.html">pgm</A></B>,
<B><A HREF="ppm.html">ppm</A></B>,
and
<B><A HREF="pam.html">pam</A></B>.
<H3 id="impconv">Implied Format Conversion</H3>
<P>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.
<strong>note:</strong> 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.
<P>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.
<P>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 <b>BLACKANDWHITE</b>. It sees a PGM image as if it were the
equivalent PAM image with tuple type <b>GRAYSCALE</b>. It sees a PPM
image as if it were the equivalent PAM image with tuple type
<b>RGB</b>. 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.
<p>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.
<p>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 <b>pamtopnm</b>.
<H3 id="transparency">Netpbm and Transparency</H3>
<P>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.
<P>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 <B><A HREF="pgm.html">pgm</A></B>. <B><a
href="pamcomp.html">pamcomp</a></B> is an example of a program that uses
a PGM transparency mask.
<P>Another means of representing transparency information has recently
developed in Netpbm, using PAM images. In spite of the argument given
above that Netpbm formats should be too simple 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 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.
<p>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 transparency
information. See <a href="pam.html">the PAM specification</a>.
<H2 id="libnetpbm">The Netpbm Library</H2>
<P>The Netpbm programming library, <B><a
href="libnetpbm.html">libnetpbm</a></B>, 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
program reads and writes the Netpbm formats, you can use it with any
formats.
<P>
But the library also contain some utility functions, such as character
drawing and RGB/YCrCb conversion.
<P>
The library has the conventional C linkage. Virtually all programs
in the Netpbm package are based on the Netpbm library.
<h2 id="config">netpbm-config</h2>
<p>In a standard installation of Netpbm, there is a program named
<b>netpbm-config</b> 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, <b>netpbm-config</b> is really a
configuration file, like those you typically see in the <i>/etc/</i>
directory of a Unix system.
<p>Example:
<pre>
$netpbm-config --datadir
/usr/local/netpbm/data
</pre>
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.
<p><b>netpbm-config</b> 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 <b>netpbm-config</b> as a bootstrap
to find all the other Netpbm files.
<p>There is no detailed documentation of <b>netpbm-config</b>. 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.
<h2 id="memoryusage">Memory Usage</h2>
<p>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.
<p>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.
<p>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.
<p>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 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.
<p>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.
<p>When considering memory usage, it is important to remember that
memory and disk storage are equivalent in two ways:
<ul>
<li>Memory is often virtual, backed by swap space on disk storage. So
accessing memory may mean doing disk I/O.
<li>Files are usually cached and buffered, so that accessing a disk file
may just mean accessing memory.
</ul>
<p>This means that the consequences of whether a program works from
the image file or from a memory copy are not straightforward.
<p>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-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.
<p>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 actually
make the program more complicated (in addition to much slower) to use
Netpbm's generic 12 byte or 8 byte pixel representation.
<p>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, especially with striping, it is
quite easy for the disk storage to be capable of supplying data faster
than the CPU can use it.
<h2 id="cpuusage">CPU Usage</h2>
<p>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.
<p>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.
<p>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.
<p>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.
<p>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 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: <a href="pamscale.html"><b>pamscale</b></a>
(shrink/expand an image), <a href="pamcomp.html"><b>pamcomp</b></a>
(overlay an image over another one), and <a
href="pamditherbw.html"><b>pamditherbw</b></a> (Make a black and white
image that approximates a grayscale image).
<p>The Netpbm image formats use 16 bit integers. The Netpbm code uses
"unsigned int" size integers to work with them.
<H2 id="netpbmforgimp">Netpbm For Gimp</H2>
<P>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.
<p>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 <b><a
href="http://netpbm2gimp.sourceforge.net/">netpbm2gimp</a></b> to compile
that same source code into a Gimp plugin.
<p>You can turn a program that converts from a certain graphics file format
to Netpbm format into a Gimp <i>load</i> plugin. Likewise, you
can turn a program that converts <em>to</em> a certain graphics format
<em>from</em> Netpbm format into a Gimp <i>store</i> plugin. Finally,
a program that transforms images in Netpbm format can become a
<i>process</i> plugin.
<p>And the <b>netpbm2gimp</b> 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.
<h2 id="companion">Companion Software</h2>
<h3 id="phpnetpbm">PHP-NetPBM</h3>
<p>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 <a href="http://sourceforge.net/projects/phpnetpbm">PHP-NetPBM</a>,
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.
<p>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.
<H2 id="othersoftware">Other Graphics Software</H2>
<P>Netpbm contains primitive building blocks. It certainly is not a
complete graphics software library.
<h3 id="othercmdline">Command Line Programs</h3>
<P><B>ImageMagick</B> does many of the same things — mainly the more
popular ones — that Netpbm does, including conversion between popular
formats and basic editing. <b>convert</b>, <b>mogrify</b>, <b>montage</b>, and
<b>animate</b> are popular programs from the <B>ImageMagick</B>
package. <B>ImageMagick</B> runs on Unix, Windows, Windows NT, Macintosh, and
VMS.
<p><b>ImageMagick</b> also contains the program <b>display</b>, which is a
<a href="#viewers">viewer</a> and <a href="#visual">visual editor</a>.
<h3 id="viewers">Image Viewers</h3>
<P>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 <b>pamx</b> or <B>ppmsvgalib</B>
in a pinch, but it is pretty limiting). <B>zgv</B> is a good full service
viewer to use on a GNU/Linux system with the SVGALIB graphics display driver
library. You can find <B>zgv</B>
at <B><A HREF="ftp://ftp.ibiblio.org/pub/Linux/apps/graphics/viewers/svga">ftp://ftp.ibiblio.org/pub/Linux/apps/graphics/viewers/svga</A>.</B>
<P><B>zgv</B> even has a feature in it wherein you can visually crop
an image and write an output file of the cropped image using
<B><a href="pamcut.html">pamcut</a></B>.
See the <B>-s</B> option to <B>zgv</B>.
<P>For the X inclined, there is also <B>xzgv</B>.
<p><b>xwud</b> (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 <a href="pnmtoxwd.html"><b>pnmtoxwd</b></a> to create it. You're
probably better off just using Netpbm's <a href="pamx.html"><b>pamx</b></a>.
<P><B>xloadimage</B> and its extension <B>xli</B> are also common
ways to display a graphic image in X.
<p><b>gqview</b> is a more modern X-based image viewer.
<p><b>qiv</b> is a small, very fast viewer for X.
<P>To play mpeg movies, such as produced by <B>ppmtompeg</B>,
try <b><a href="http://www.mplayerhq.hu/design7/info.html">mplayer</a></b> or
<b><a href="http://sourceforge.net/projects/xine">xine</a>.</b>
<p>See <B><A
HREF="ftp://metalab.unc.edu/pub/Linux/apps/graphics/viewers/X">ftp://metalab.unc.edu/pub/Linux/apps/graphics/viewers/X</A></B>.
<h3 id="capturers">Image Capturers</h3>
<p><b>xwd</b> (X Window Dump), a classic application program in the X Window
System, captures the contents of an X window, in its own special image format,
called X Window Dump File. You can use
Netpbm's <a href="xwdtopnm.html"><b>xwdtopnm</b></a> to turn it into something
more useful.
<p><a href="http://www.rcdrummond.net/fbdump/"><b>fbdump</b></a>
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.
<h3 id="visual">Visual Graphics Software</h3>
<p>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.
<p><b>xv</b> 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.
<P>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 <B><A HREF="http://www.gimp.org">http://www.gimp.org</A></B>. And you can
add most of Netpbm's function to Gimp
using <a href="http://netpbm2gimp.sourceforge.net/">Netpbm2gimp</a>.
<p><b>ImageMagick</b> contains the program <b>display</b>, which is another
visual image editor. It has fewer functions than Gimp. This program uses the
X Window System. The package also contains <a href="othercmdline">command
line</a> graphics programs.
<p>Electric Eyes, <b>kuickshow</b>, and <b>gthumb</b> are also visual
editors for the X/Window system, and <b>KView</b> and <b>gwenview</b>
are specifically for KDE.
<h3 id="programmingtools">Programming Tools</h3>
<P>If you're writing a program in C to draw and manipulate images, check out
<a href="http://www.boutell.com/gd">gd</a>. Netpbm contains a C library for
drawing images (<b>libnetpbm</b>'s "ppmd" routines), but it is
probably not as capable or documented as <b>gd</b>. You can easily run any
Netpbm program from a C program with the <b>pm_system</b> function from the
Netpbm programming library, but that is less efficient than <b>gd</b>
functions that do the same thing.
<p><a href="http://cairographics.org/">Cairo</a> is similar.
<P><B>Ilib</B> is a C subroutine library with functions for adding
text to an image (as you might do at a higher level with
<B>pbmtext</B>, <B>pamcomp</B>, etc.). It works with Netpbm input and
output. Find it at <B><A
HREF="http://www.k5n.us/Ilib.php">k5n.us</A></B>.
Netpbm also includes character drawing functions in the <B><a
href="libnetpbm.html">libnetpbm</a></B> library, but they do not have as
fancy font capabilities (see <B><a href="ppmdraw.html">ppmdraw</a></B>
for an example of use of the Netpbm character drawing functions).
<p><a href="http://www.pango.org/">Pango</a> is another text rendering
library, with an emphasis on internationalization.
<p>Pango and Cairo complement each other and work well together.
<P><B>GD</B> 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.
<h3 id="toolsforformats">Tools For Specific Graphics Formats</h3>
<p><b>mencode</b>, which is part of the <b><a
href="http://www.mplayerhq.hu/design7/info.html">mplayer</a></b> package,
creates movie files. It's like a much more advanced version of <a
href="ppmtompeg.html"><b>ppmtompeg</b></a>, without the Netpbm
building block simplicity.
<p><a href="http://mjpeg.sourceforge.net"><b>MJPEGTools</b></a> is software
for dealing with the MJPEG movie format.
<P>To create an animated GIF, or extract a frame from one, use
<B>gifsicle</B>. <B>gifsicle</B> converts between animated GIF and
still GIF, and you can use <B>pamtogif</B> and <B>giftopnm</B> to
connect up to all the Netpbm utilities. See <B><A
HREF="http://www.lcdf.org/gifsicle">http://www.lcdf.org/gifsicle</A></B>.
<P>To convert an image of text to text (optical character recognition
- OCR), use <B>gocr</B> (think of it as an inverse of <B>pbmtext</B>).
See <B> <a
href="http://jocr.sourceforge.net/">http://jocr.sourceforge.net/</a></b>.
<P><B><A HREF="http://schaik.com/pngsuite">http://schaik.com/pngsuite</A></B>
contains a PNG test suite -- a whole bunch of PNG images exploiting the
various features of the PNG format.
<P>Other versions of Netpbm's <B>pnmtopng</B>/<B>pngtopam</B> are at
<A HREF="http://www.schaik.com/png/pnmtopng.html">
http://www.schaik.com/png/pnmtopng.html</A>.
<p>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.
<p><b><a href="http://pngwriter.sourceforge.net">pngwriter</a></b> 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.
<P><B>jpegtran</B> 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. <B>jpegtran</B> comes with the
Independent JPEG Group's (<A
HREF="http://www.ijg.org">http://www.ijg.org)</A> JPEG library.
<P> Some tools to deal with EXIF files (see also Netpbm's <B><a
href="jpegtopnm.html">jpegtopnm</a></B> and <B><a
href="pnmtojpeg.html">pnmtojpeg</a></B>):
To dump (interpret) an EXIF header: Exifdump ((<A
HREF="http://topo.math.u-psud.fr/~bousch/exifdump.py">http://topo.math.u-psud.fr/~bousch/exifdump.py)</A>)
or <A HREF="http://www.sentex.net/~mwandel/jhead">Jhead</a>.
<P>A Python EXIF library and dumper: <A
HREF="http://pyexif.sourceforge.net.">http://pyexif.sourceforge.net.</A>
<P>Here's some software to work with IOCA (Image Object Content
Architecture): <a
href="http://www.forminnovation.com">ImageToolbox</a> ($2500, demo
available). This can convert from TIFF -> IOCA and back again.
<a href="http://www.thethinktanksoftware.com/details.html">Ameri-Imager</a>
($40 Windows only).
<P><B>pnm2ppa</B> converts to HP's "Winprinter" format (for
HP 710, 720, 820, 1000, etc). It is a superset of Netpbm's
<B>pbmtoppa </B> and handles, notably, color. However, it is more of
a printer driver than a Netpbm-style primitive graphics building
block. See <A
HREF="http://sourceforge.net/projects/pnm2ppa">The Pnm2ppa /Sourceforge
Project</a>
<p><b>DjVuLibre</b> 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
between DjVu and PNM. See <a
href="http://djvu.sourceforge.net/"> the DjVu website.</a>
<h3 id="document">Document/Graphics Software</h3>
<p>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.
<p>First, we look at where Netpbm meets document processing.
<b>pstopnm</b> converts from Postscript and PDF to PNM. It
effectively renders the document into images of printed pages.
<b>pstopnm</b> is nothing but a convenient wrapper for <a
href="http://www.ghostscript.com/">Ghostscript</a>, and in particular
Netpbm-format device drivers that are part of it. <b>pnmtops</b> and
<b>pbmtoepsi</b> 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.
<P>Adobe invented Postscript and PDF and products from Adobe are for many
purposes the quintessential Postscript and PDF tools.
<P>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.
<P>Other software from Adobe, available for purchase, interprets and
creates Postscript and PDF files. "Distill"
is a program that converts Postscript to PDF.
<p><a href="http://www.foolabs.com/xpdf/"><b>xpdf</b></a> also reads
PDF files.
<p>GSview, ghostview, gv, ggv, and kghostview are some other viewers
for Postscript and PDF files.
<p>The program <b>ps2pdf</b>, part of Ghostscript, converts from Postscript
to PDF.
<P>Two packages that produce more kinds of Encapsulated Postscript
than the Netpbm programs, including compressed kinds, are <a
href="http://bmeps.sourceforge.net/">bmeps</a> and <a
href="http://imgtops.sourceforge.net/">imgtops</a>.
<p><b>dvips</b> 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.
<p><a href="http://wvware.sourceforge.net"><b>wvware</b></a> 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.
<p><A href="http://www.verypdf.com/artprint">Document Printer</a>
converts various print document formats (Microsoft Word, PDF, HTML, etc.)
to various graphic image formats. ($38, Windows only).
<P>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.
<h3 id="otherothersoftware">Other</h3>
<P>The <B>file</B> 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
<B><a href="anytopnm.html">anytopnm</a></B> program depends on <B>file.</B>
See
<B><A HREF="ftp://ftp.astron.com/pub/file">ftp://ftp.astron.com/pub/file</A></B>.
<P>The <a href="http://www.cs.utah.edu/gdc/projects/urt">Utah Raster
Toolkit</a> from the <a href="http://www.cs.utah.edu/gdc">Geometric Design And
Computation group</a> 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 conversions. This package is based on the RLE format, which you can
convert to and from the Netpbm formats.
<P><B>Ivtools</B> 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 <B><A
HREF="http://www.ivtools.org">http://www.ivtools.org</A></B>.
<p>Chisato Yamauchi <cyamauch@ir.isas.jaxa.jp> has written a free
c/Fortran graphic library: <a
href="http://www.ir.isas.jaxa.jp/~cyamauch/eggx_procall/">EGGX/ProCall</a>.
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.
<P>The program <B>morph</B> morphs one image into another. It uses
Targa format images, but you can use <B>tgatoppm</B> and
<B>ppmtotga</B> to deal with that format. You have to use the
graphical (X/Tk) Xmorph to create the mesh files that you must feed to
<B>morph</B>. <B>morph</B> is part of the Xmorph package. See <B><A
HREF="http://xmorph.sourceforge.net/">http://xmorph.sourceforge.net/</A></B>.
<H2 id="otherfmt">Other Graphics Formats</H2>
<P>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
<em>not</em> handle (yet).
<p>Various commercial Windows software handles dozens of formats that
Netpbm does not, especially 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.
<UL>
<li>WebP was announced by Google in October 2010 as a more compressed
replacement for JFIF (aka JPEG) on the web.
<li>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. <a href="http://charls.codeplex.com">CharLS</a> is a programming
library for JPEG-LS.
<LI>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 <a href="https://github.com/thorfdbg/libjpeg">GitHub</a>.
<li>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.
<li>Direct Draw Surface (DDS)is the de facto standard wrapper format for S3
texture compression, as used in all modern realtime graphics applications.
Besides Windows-based tools, there is a <b>Gimp</b> plugin for this format.
<li>DjVu is a web-centric format and software platform for
distributing 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, because it
downloads faster, displays and renders faster, looks nicer on a
screen, and consumes less client resources than competing formats.
<p>For more information, see <a
href="http://djvu.sourceforge.net/"> the DjVu website.</a>
<LI> <a
href="http://www.web3d.org/x3d/specifications/vrml">VRML
(Virtual Reality Modelling Language)</a>
<LI>
CALS (originated by US Department Of Defense, favored by architects).
It is described in this 1997 listing of graphics formats:
<A HREF="http://www.faqs.org/faqs/graphics/fileformats-faq/part3/">
http://www.faqs.org/faqs/graphics/fileformats-faq/part3/</A>. CALS
has at times been an abbreviation of various things, all of which appear
to be essentially the same format, but possibly slightly different:
<ul>
<li>Computer Aided Logistics Support
<li>Computer Aided Acquisition and Logistics Support
<li>Continuous Acquisition and Life-cycle Support
<li>Commerce At Light Speed
</ul>
The US Navy publishes <a
href="http://www.dt.navy.mil/tot-shi-sys/des-int-pro/tec-inf-sys/cal-std/index.html">specs</a>
for it.
<p>The web page <a
href="http://www.sollers.ca/projects/cals2tiff/">http://www.sollers.ca</a>
describes a program for converting from CALS to TIFF.
<LI>
array formats dx, general, netcdf, CDF, hdf, cm
<LI>
CGM+
<li>HDR formats OpenEXR, SGI TIFF LogLuv, floating point TIFF,
Radiance RGBE
<LI>Windows Meta File (.WMF). Libwmf converts from WMF to things like
Latex, PDF, PNG. Some of these can be input to Netpbm.
<LI>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.
<li>RTF
<LI>
DXF (AutoCAD)
<LI>
IOCA (Image Object Content Architecture)
The specification of this format is documented by IBM:
<a href="http://publibz.boulder.ibm.com/epubs/pdf/c3168055.pdf">
Data Stream and Object Architectures: Image Object Content Architecture
Reference</a>. See above for software that processes this format.
<LI>OpenEXR is an HDR format (like <a href="pamtopfm.html">PFM</a>).
See <a href="http://www.openexr.com">
http://www.openexr.com</a>.
<li>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.
<li>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.
<li><a href="http://en.wikipedia.org/wiki/MJPEG">MJPEG</a> movie
format.
<li>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 <a
href="http://mjpeg.sourceforge.net"><b>MJPEGTools</b></a>. The programs
<b>pnmtoy4m</b> and <b>y4mtopnm</b> (and predecessors <b>ppmtoy4m</b>
and <b>y4mtoppm</b>) 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.
</UL>
<H2 id="history">History</H2>
<P>Netpbm has a long history, starting with Jef Poskanzer's Pbmplus
package in 1988. See the <a
href="http://netpbm.sourceforge.net/history.html">Netpbm web site</a>
for details.
<p>The file <B>doc/HISTORY</B> in the Netpbm source code contains a
detailed change history release by release.
<H2 id="author">Author</H2>
<P>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.
<P>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.
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