Manual: xwdtopnm

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 xwd‐
       topnm, 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 in‐
       tensity value, e.g. the red component of a pixel) is greater than 255 and therefore each sample takes 2 bytes to rep‐
       resent.	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 gener‐
       ates  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)