diff options
| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2009-01-21 17:52:56 +0000 |
|---|---|---|
| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2009-01-21 17:52:56 +0000 |
| commit | fe50b429374a2bdf22c892c610fe96c191ef321f (patch) | |
| tree | ee3abe2b9c76eef7b5c77879d349e126b3b75b8b /xwdtopnm.html | |
| parent | a8f37df0f40833d99475480cc5a4d132b9e8ff52 (diff) | |
| download | netpbm-mirror-fe50b429374a2bdf22c892c610fe96c191ef321f.tar.gz netpbm-mirror-fe50b429374a2bdf22c892c610fe96c191ef321f.tar.xz netpbm-mirror-fe50b429374a2bdf22c892c610fe96c191ef321f.zip | |
"miscellaneous update"
git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@821 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'xwdtopnm.html')
| -rw-r--r-- | xwdtopnm.html | 70 |
1 files changed, 51 insertions, 19 deletions
diff --git a/xwdtopnm.html b/xwdtopnm.html index 3b28615d..285d2e2f 100644 --- a/xwdtopnm.html +++ b/xwdtopnm.html @@ -2,24 +2,21 @@ <HTML><HEAD><TITLE>Xwdtopnm User Manual</TITLE></HEAD> <BODY> <H1>xwdtopnm</H1> -Updated: 21 October 2003 +Updated: 21 January 2009 <BR> <A HREF="#index">Table Of Contents</A> -<A NAME="lbAB"> </A> <H2>NAME</H2> xwdtopnm - convert an X11 or X10 window dump file to a PNM image -<A NAME="lbAC"> </A> -<H2>SYNOPSIS</H2> +<H2 id="synopsis">SYNOPSIS</H2> <B>xwdtopnm</B> [<b>-verbose</b>] [<b>-headerdump</b>] [<I>xwdfile</I>] -<A NAME="lbAD"> </A> -<H2>DESCRIPTION</H2> +<H2 id="description">DESCRIPTION</H2> <p>This program is part of <a href="index.html">Netpbm</a>. @@ -45,8 +42,7 @@ two bytes instead of one for each sample in the image). So you may want to run the output of <b>xwdtopnm</b> through <b>pamdepth</b> before feeding it to one of these old programs. -<A NAME="options"> </A> -<H2>OPTIONS</H2> +<H2 id="options">OPTIONS</H2> <dl> <dt><b>-verbose</b> @@ -61,30 +57,66 @@ new in Netpbm 10.26 (December 2004). </dl> +<h2 id="notes">NOTES</h2> -<A NAME="lbAF"> </A> -<H2>SEE ALSO</H2> +<h3 id="twobytesamples">Two Byte Samples</h3> + +<p><b>xwdtopnm</b> 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 <b>xwdtopnm</b> produces, which means they will see totally +different colors that they should. <b>xv</b> is one such program. + +<p>If this is a problem (e.g. you want to look at the output of <b>xwdtopnm</b> +with <b>xv</b>), there are two ways to fix it: + +<ul> +<li>Pass the output through <b>pamendian</b> to produce the format the +program expects. +<li>Pass the output through <b>pamdepth</b> to reduce the maxval below 256 +so there is only one byte per sample. +</ul> + +<p>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, +<b>xwdtopnm</b> has to use a large maxval. In this example, it would use 31 * +31 * 63 = 60543, and use 48 bits per pixel. + +<p>Because this is a common and frustrating problem when using <b>xwdtopnm</b>, +the program issues a warning whenever it generates output with two byte +samples. You can quiet this warning with the <b>-quiet</b> <a href="index.html#commonoptions">common option</a>. + + +<H2 id="seealso">SEE ALSO</H2> <A HREF="pnmtoxwd.html">pnmtoxwd</A>, +<A HREF="pamendian.html">pamendian</A>, +<A HREF="pamdepth.html">pamdepth</A>, <A HREF="pnm.html">pnm</A>, <b>xwd</b> man page -<A NAME="lbAG"> </A> -<H2>AUTHOR</H2> +<H2 id="author">AUTHOR</H2> Copyright (C) 1989, 1991 by Jef Poskanzer. <HR> -<A NAME="index"> </A> -<H2>Table Of Contents</H2> +<H2 id="index">Table Of Contents</H2> <UL> -<LI><A HREF="#lbAB">NAME</A> -<LI><A HREF="#lbAC">SYNOPSIS</A> -<LI><A HREF="#lbAD">DESCRIPTION</A> +<LI><A HREF="#synopsis">SYNOPSIS</A> +<LI><A HREF="#description">DESCRIPTION</A> <LI><A HREF="#options">OPTIONS</A> -<LI><A HREF="#lbAF">SEE ALSO</A> -<LI><A HREF="#lbAG">AUTHOR</A> +<li><a href="#notes">NOTES</a> + <ul> + <li><a href="#twobytesamples">Two Byte Samples</a> + </ul> +<LI><A HREF="#seealso">SEE ALSO</A> +<LI><A HREF="#author">AUTHOR</A> </UL> </BODY> </HTML> |