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 pseudocolor 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  Common
       Options ), 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 effect 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, xwdtopnm has  to  use  a  large  maxval.   In  this
       example,  it  would use maxval 31 * 63 = 1953, which requires two bytes per sample, totalling 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 common
       option .  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)