man > xwdtopnm(1)

Xwdtopnm User Manual(1)                General Commands Manual               Xwdtopnm User Manual(1)

NAME
       xwdtopnm - convert an X11 or X10 window dump file to a PNM image


SYNOPSIS
       xwdtopnm [-verbose] [-headerdump] [xwdfile]


DESCRIPTION
       This program is part of Netpbm(1).

       xwdtopnm  reads  an  X11 or X10 window dump file as input and produces a PNM image as output.
       The type of the output image depends on the input file - if it's black and white, the  output
       is  PBM.   If it's grayscale, the output is PGM.  Otherwise, it's PPM.  The program tells you
       which type it is writing.

       Using this program, you can convert anything you can display on  an  X  workstation's  screen
       into a PNM image.  Just display whatever you're interested in, run the xwd program to capture
       the  contents  of the window, run it through xwdtopnm, and then use pamcut to select the part
       you want.

       Note that a pseudocolor XWD image (typically what you get when you make a dump of  a  pseudo‐
       color X window) has maxval 65535, which means the PNM file that xwdtopnm generates has maxval
       65535.   Many  older  image  processing  programs (that aren't part of the Netpbm package and
       don't use the Netpbm programming library) don't know how to handle a PNM  image  with  maxval
       greater  than  255 (because there are two bytes instead of one for each sample in the image).
       So you may want to run the output of xwdtopnm through pamdepth before feeding it  to  one  of
       these old programs.

       xwdtopnm  can't  convert every kind of XWD image (which essentially means it can't convert an
       XWD created from every kind of X display configuration).  In particular,  it  cannot  convert
       one with more than 24 bits per pixel.



OPTIONS
       In  addition  to  the options common to all programs based on libnetpbm (most notably -quiet,
       see ]8;;index.html#commonoptions\ Common Options]8;;\ ), xwdtopnm recognizes the following command line options:



       -verbose
              This option causes xwdtopnm to display handy information about the input image and the
              conversion process


       -headerdump
              This option causes xwdtopnm to display the contents of the X11 header.  It has no  ef‐
              fect when the input is X10.  This option was new in Netpbm 10.26 (December 2004).




NOTES
   Two Byte Samples
       xwdtopnm  sometimes  produces  output with a maxval greater than 255, which means the maximum
       value of a sample (one intensity value, e.g. the red component of a pixel)  is  greater  than
       255 and therefore each sample takes 2 bytes to represent.  This can be a problem because some
       programs expect those bytes in a different order from what the Netpbm format specs say, which
       is  what  xwdtopnm  produces,  which  means  they will see totally different colors than they
       should.   xv is one such program.

       If this is a problem (e.g. you want to look at the output of xwdtopnm with xv), there are two
       ways to fix it:



       •      Pass the output through pamendian to produce the format the program expects.

       •      Pass the output through pamdepth to reduce the maxval below 256 so there is  only  one
              byte per sample.


       Often, there is no good reason to have a maxval greater than 255.  It happens because in XWD,
       but  not  PNM,  each  color component of a pixel can have different resolution, for example 5
       bits for blue (maxval 31), 5 bits for red (maxval 31), and 6 bits for green (maxval 63),  for
       a  total of 16 bits per pixel.  In order to reproduce the colors as closely as possible, xwd‐
       topnm has to use a large maxval.  In this example, it would use 31 * 63 = 1953,  and  use  48
       bits per pixel.

       Because  this  is  a common and frustrating problem when using xwdtopnm, the program issues a
       warning whenever it generates output with two byte samples.  You can quiet this warning  with
       the -quiet ]8;;index.html#commonoptions\common option]8;;\ .  The warning was new in Netpbm 10.46 (March 2009).



SEE ALSO
       pnmtoxwd(1), pamendian(1), pamdepth(1), pnm(1), xwd man page


AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.

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/xwdtopnm.html

netpbm documentation                       08 January 2010                   Xwdtopnm User Manual(1)