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User manual for Netpbm(0)                            User manual for Netpbm(0)

       netpbm - netpbm library overview

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

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

       Netpbm is an open source software package, distributed via the  Source-
       forge  netpbm project .

Table Of Contents
       o       Overview Of Netpbm

       o       The Netpbm Formats

       o       Implied Format Conversion

       o       Netpbm and Transparency

       o       The Netpbm Programs

       o       Common Options

       o       Directory

       o       How To Use The Programs

       o       The Netpbm Library

       o       netpbm-config

       o       Memory Usage

       o       CPU Usage

       o       Netpbm For Gimp

       o       Companion Software

       o       PHP-NetPBM

       o       Other Graphics Software

       o       Image Viewers

       o       Visual Graphics Software

       o       Programming Tools

       o       Tools For Specific Graphics Formats

       o       Document/Graphics Software

       o       Other

       o       Other Graphics Formats

       o       History

       o       Author

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
       anything but that.

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

       The  Netpbm  programs can read and write files greater than 2 GiB wher-
       ever the underlying system can.  There may be exceptions where the pro-
       grams  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

   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
              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_mes-
              sage() service of the Netpbm library).

              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 Netpbm format, generate it
              in the "plain" (aka "ascii") version of the format,  as  opposed
              to the "raw" (aka "binary") version.

              This option was introduced in Netpbm 10.10 (October 2002).

       Here is a complete list of all the Netpbm programs (with links to their


   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

       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 $_ | ppmbrighten -v 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 hypotheti-
       cal  program  printcmyk takes the filename of a Tiff CMYK file as input
       and what you have is a PNG file abc.png.

       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

The Netpbm Formats
       All of the programs work with a set  of  graphics  formats  called  the
       'netpbm'  formats.   Specifically,  these formats are pbm(5) , pgm(5) ,
       ppm(5) , and pam(5)

       The first three of these are sometimes known generically as 'pnm'.

       Many of the Netpbm programs convert from a  Netpbm  format  to  another
       format  or  vice  versa.  This is so you can use the Netpbm programs to
       work on graphics of any format.  It is also common to use a combination
       of  Netpbm  programs  to  convert from one non-Netpbm format to another
       non-Netpbm format.  Netpbm has converters for about 100  graphics  for-
       mats,  and as a package Netpbm lets you do more graphics format conver-
       sions 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
        Implied Format Conversion .

        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, 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 pro-
       duces 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
       Implied Format Conversion .

       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
       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-

       The formats are described in the specifications of pbm(5)  ,  pgm(5)  ,
       ppm(5) , and pam(5)

   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, ignor-
       ing 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 sepa-
       rate (slightly redefined) PGM image.  In this  pseudo-PGM,  what  would
       normally  be  a  pixel's intensity is instead an opaqueness value.  See
       pgm(5) pamcomp(1)
        is an example of a program that uses a PGM transparency mask.

       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  pri-
       marily  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

       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 thePAMspecification(5)

The Netpbm Library
       The Netpbm programming library, libnetpbm(3) , 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-

       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.

       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 typ-
       ically see in the /etc/ directory of a Unix system.

           $netpbm-config --datadir

       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
       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  mem-
       ory, 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
       totally  describe the pixel.  Netpbm does this expansion to make imple-
       menting 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 ordi-
       nary 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:

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

       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
       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 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  par-
       ticular,  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 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
       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.

CPU Usage
       People sometimes wonder what CPU facilities  Netpbm  programs  and  the
       Netpbm  programming library use.  The programs never depend on particu-
       lar features existing (assuming they're  compiled  properly),  but  the
       speed  and cost of running a program varies depending upon the CPU fea-

       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  instruc-
       tions  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  pro-
       grams  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  pro-
       grams do that: pamscale(1)

       (shrink/expand an image), 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 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
       program (remember that a fundamental mission of Netpbm is make  writing
       image  manipulation programs easy) and then use netpbm2gimp  to compile
       that same source code into a Gimp plugin.

       You can turn a program that converts from a certain graphics file  for-
       mat to Netpbm format into a Gimp load plugin.  Likewise, you can turn a
       program 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
       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
       PHP-NetPBM  , a PHP class that interacts with Netpbm.  Its main goal is
       to decrease the pain of using Netpbm when working with images in  vari-
       ous  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.

   Graphics Viewers
       The first thing you will want to make use of any of these  tools  is  a
       viewer.   (On  GNU/Linux,  you can use 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 library.  You
       can  find  zgv  at  ftp://ftp.ibiblio.org/pub/Linux/apps/graphics/view-
       ers/svga .

       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.

       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 xine .

       See ftp://metalab.unc.edu/pub/Linux/apps/graphics/viewers/X .

   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.

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

       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 mainte-
       nance, though.

       The Gimp is a visual image editor for Unix and X, in the same  category
       as  the more famous, less capable, and much more expensive Adobe Photo-
       shop, etc. for Windows.  See http://www.gimp.org .   And  you  can  add
       most of Netpbm's function to The Gimp using Netpbm2gimp .

       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  gd  .   Netpbm  contains a C library for drawing images, but it is
       probably not as capable or documented as gd.  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  func-
       tions that do the same thing.

       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 k5n.us .  Netpbm
       also includes character drawing functions in the libnetpbm(3)
        library, but they do not have as fancy font capabilities  (see  ppmla-

       for an example of use of the Netpbm character drawing functions).

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

   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.

       MJPEGTools  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
       http://www.lcdf.org/gifsicle .

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

       http://schaik.com/pngsuite   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.

       pngwriter  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

       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.
       jpegtran comes with the Independent Jpeg Group's ( http://www.ijg.org)
       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 (( http://topo.math.u-
       psud.fr/~bousch/exifdump.py) ) or Jhead .

       A Python EXIF library and dumper: http://pyexif.sourceforge.net.

       Here's some software to work with IOCA (Image Object Content  Architec-
       ture):  ImageToolbox    ($2500, demo available).  This can convert from
       TIFF -> IOCA and back again.  Ameri-Imager(1)

       ($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,
       notably, color.  However, it is more of a printer driver than a Netpbm-
       style  primitive graphics building block.  See The Pnm2ppa /Sourceforge

       DjVuLibre is a package of software  for  using  the  DjVu  format.   It
       includes viewers, browser plugins, decoders, simple encoders, and util-
       ities.  The encoders and decoders can convert  between  DjVu  and  PNM.
        the DjVu website.

   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  Ghostscript  ,  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 process-
       ing 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.

       xpdf  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

       Two packages that produce more kinds of  Encapsulated  Postscript  than
       the Netpbm programs, including compressed kinds, are bmeps  and imgtops

       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  graphi-

       wvware  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.

       Document  Printer    converts various print document formats (Microsoft
       Word, PDF, HTML, etc.)  to various graphic image formats.   ($38,  Win-
       dows 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.

       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 ftp://ftp.astron.com/pub/file .

       The Utah Raster Toolkit serves a lot of the same purpose as Netpbm, but
       without the emphasis on format conversions.  This package is  based  on
       the  RLE  format, which you can convert to and from the Netpbm formats.
       The website of the Geometric Design  And  Computation  group    in  the
       Department of Computer Science at University of Utah used to (ca. 2002)
       have information on the Utah Raster Toolkit, but now it doesn't.

       Ivtools is a suite of free X Windows drawing  editors  for  Postscript,
       Tex,  and web graphics production, as well as an embeddable and extend-
       able vector  graphic  shell.   It  uses  the  Netpbm  facilities.   See
       http://www.ivtools.org .

       Senri  Yamauchi has written a free c/Fortran graphic library: EGGX/Pro-
       Call .  He says he tried to write the ultimate easy-to-use graphic  kit
       for  X.   It  is for drawing upon X11, but for storage, it outputs PPM.
       He suggests Netpbm to convert to other formats.  The manual is only  in

       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
       http://xmorph.sourceforge.net/ .

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

       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.

       o      DjVu  is  a  web-centric  format  and software platform for dis-
              tributing documents and images.  Promoters  say  it  is  a  good
              replacement  for  PDF,  PS, TIFF, JPEG, and GIF for distributing
              scanned documents, digital documents,  or  high-resolution  pic-
              tures, 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
               the DjVu website.

       o       VRML (Virtual Reality Modelling Language)

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

       o      Computer Aided Logistics Support

       o      Computer Aided Acquisition and Logistics Support

       o      Continuous Acquisition and Life-cycle Support

       o      Commerce At Light Speed

              The US Navy publishes specs(1)

              for it.

              The web page http://www.sollers.ca  describes a program for con-
              verting from CALS to TIFF.

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

       o       CGM+

       o      HDR formats OpenEXR, SGI TIFF LogLuv, floating point TIFF, Radi-
              ance RGBE

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

       o      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.

       o      RTF

       o       DXF (AutoCAD)

       o        IOCA  (Image Object Content Architecture) The specification of
              this format is documented by IBM:
               Data Stream and  Object  Architectures:  Image  Object  Content
              Architecture  Reference .  See above for software that processes
              this format.

       o      OpenEXR is an HDR format (like PFM(1) ).  See
               http://www.openexr.com .

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

       o      YUV 4:2:0, aka YUV 420, and the simlar 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.

       o       MJPEG  movie format.

       o      YUV4MPEG2  is a movie format whose purpose is similar to that of
              the Netpbm formats for still images.  You use it for  manipulat-
              ing  movies, but not for storing or transmitting them.  The only
              known use of the format is with MJPEGTools .  The programs  pnm-
              toy4m  and  y4mtopnm  (and predecesors 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 ulti-
              mately MPEG2.

       Netpbm has a long history, starting with Jef Poskanzer's Pbmplus  pack-
       age in 1988.  See the Netpbmwebsite(1)

       for details.

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

       Netpbm is based on the Pbmplus package by  Jef  Poskanzer,  first  dis-
       tributed  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

       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.

netpbm documentation           22 February 2009      User manual for Netpbm(0)

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