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Xwdtopnm User Manual(0) 						  Xwdtopnm User Manual(0)

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

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

       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 out-
       put  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 cap-
       ture 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 pseu-
       docolor 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 pack-
       age 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 con-
       vert one with more than 24 bits per pixel.

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

	      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).

   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
       that 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:

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

       o      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,  byte  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 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 common option <index.html#commonoptions> .  The warning was new in Netpbm
       10.46 (March 2009).

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

       Copyright (C) 1989, 1991 by Jef Poskanzer.

netpbm documentation			  8 January 2010		  Xwdtopnm User Manual(0)
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