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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2008-01-20 00:16:10 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2008-01-20 00:16:10 +0000 |
| commit | 2d95a3a4e16940583b1dbce3fb085b4e39f1b3fe (patch) | |
| tree | 9e2209128d54dcb284ee7c0f64a87f4c6030c5f8 /pamflip.html | |
| parent | 215d2a6bdb43a9e73327a6dfe860404cc6692415 (diff) | |
| download | netpbm-mirror-2d95a3a4e16940583b1dbce3fb085b4e39f1b3fe.tar.gz netpbm-mirror-2d95a3a4e16940583b1dbce3fb085b4e39f1b3fe.tar.xz netpbm-mirror-2d95a3a4e16940583b1dbce3fb085b4e39f1b3fe.zip | |
"miscellaneous update"
git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@567 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'pamflip.html')
| -rw-r--r-- | pamflip.html | 113 |
1 files changed, 73 insertions, 40 deletions
diff --git a/pamflip.html b/pamflip.html index 664b3967..e5ad9ae0 100644 --- a/pamflip.html +++ b/pamflip.html @@ -2,17 +2,15 @@ <HTML><HEAD><TITLE>Pamflip User Manual</TITLE></HEAD> <BODY> <H1>pamflip</H1> -Updated: 18 February 2005 +Updated: 20 January 2008 <BR> <A HREF="#index">Table Of Contents</A> -<A NAME="lbAB"> </A> <H2>NAME</H2> pamflip - flip or rotate a PAM or PNM image -<A NAME="lbAC"> </A> -<H2>SYNOPSIS</H2> +<H2 id="synopsis">SYNOPSIS</H2> <B>pamflip</B> { @@ -30,8 +28,7 @@ pamflip - flip or rotate a PAM or PNM image [<I>pamfile</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>. @@ -55,8 +52,7 @@ hand, can do this particular transformation directly on the compressed data without loss. -<A NAME="lbAE"> </A> -<H2>OPTIONS</H2> +<H2 id="options">OPTIONS</H2> <P>All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may @@ -139,34 +135,75 @@ a complete explanation in comments in the source code. <dt><b>-memsize=</b><i>mebibytes</i> <dd><i>mebibytes</i> is the size in mebibytes (aka megabytes) of -<em>real</em> memory (not virtual) available for <b>pamflip</b>. +memory available for <b>pamflip</b>. It is the lesser of the amount +of real or virtual memory available. + <b>pamflip</b> does nothing special to allocate real memory or control it's allocation -- it gets whatever it gets just by referencing -virtual memory normally. This is the maximum amount that -<b>pamflip</b> can be expected to end up with by doing that. This is -just about impossible for you to know, of course, but you can -estimate. The total real memory in your system should be a major -factor in your estimate. - -<p>When you specify <b>-memsize</b> and are doing a row for column type -of transformation, <b>pamflip</b> does the transformation in multiple -passes, each one with a working set size less than the specified value. - -<p>If your estimate is even slightly too large, it's the same as -infinity. If you estimate too small, <b>pamflip</b> will use more -passes than it needs to, and thus will slow down proportional to the -underestimate. - -<p>If you do not specify <b>-memsize</b>, <b>pamflip</b> assumes infinite -real memory and does the entire transformation in one pass. +virtual memory normally. The real memory figure in question is the +maximum amount that <b>pamflip</b> can be expected to end up with by +doing that. This is just about impossible for you to know, of course, +but you can estimate. The total real memory in your system should be +a major factor in your estimate. + +<p>If <b>pamflip</b> cannot fit the entire image in the amount of +memory you specify, it does the transformation in chunks, using temporary +files for intermediate results. + +<p>Strict horizontal transformations (either left for right or null), +<b>pamflip</b> never keeps more than one row in memory, so the memory +size is irrelevant and <b>pamflip</b> doesn't use temporary files. + +<p>The real memory is important when you do a column for row type of +transformation (e.g. <b>-rotate90</b>). In that case, even if +<b>pamflip</b> can fit the entire image in virtual memory at once, if +it does not also fit in real memory, the program will thrash like +crazy because of the order in which <b>pamflip</b> accesses the +pixels, and that means it will take a ridiculously long time to run. +A proper <b>-memsize</b> drastically reduces the paging. + +<p>If you specify <b>-memsize</b> too large, <b>pamflip</b> may +attempt to get more virtual memory than the system allows it and fail. +If it can get the virtual memory, but <b>-memsize</b> is larger than +the amount of real memory the system allows it and the transformation +is row for column, it will page thrash and run very slowly. A value +even slightly too high is the same as infinity. + +<p>If you specify <b>-memsize</b> too small, the program will run +slightly more slowly due to extra overhead in manipulating temporary +files. Also, if your environment isn't set up to make temporary files +possible, <b>pamflip</b> will fail. + +<p>Doing the entire transformation "in memory" doesn't speed +things up as much as you might think, because even with the temporary +files, the data is just as likely to be in memory. Virtual memory +gets paged to disk and disk files get cached in memory. In fact, the +pixels fit much more compactly into memory when stored in a temporary +file than when stored "in memory" because <b>pamflip</b> +uses a more efficient format. So you're likely to have <em>less</em> +disk I/O when you allow <b>pamflip</b> less memory. + +<p>If you do not specify <b>-memsize</b>, <b>pamflip</b> assumes +infinity. <p>This option did not exist before Netpbm 10.7 (August 2002). + +<p>Before Netpbm 10.42 (March 2008), this option applied only to real +memory. <b>pamflip</b> would always keep the entire image in virtual +memory and if it could not get enough virtual memory, it failed. +<b>pamflip</b> accessed the pixels in an order designed to keep real +memory use within the specified amount. <dt><b>-pagesize=</b><i>bytes</i> <dd><i>bytes</i> is the size in bytes of a paging unit -- the amount of memory that gets paged in or out as an indivisible unit -- in your system. The default is 4KiB. +<p>This option has no effect. + +<p>Before Netpbm 10.42 (March 2008), <b>pamflip</b> used it to control its +use of real memory. + <p>This option did not exist before Netpbm 10.7 (August 2002). </dl> @@ -179,36 +216,32 @@ about its progress. </dl> -<A NAME="lbAF"> </A> -<H2>SEE ALSO</H2> +<H2 id="seealso">SEE ALSO</H2> <A HREF="pnmrotate.html">pnmrotate</A>, <A HREF="pnm.html">pnm</A>, +<A HREF="pam.html">pam</A>, <b>jpegtran</b> manual -<A NAME="lbAG"> </A> -<A NAME="history"></A> -<H2>HISTORY</H2> +<H2 id="history">HISTORY</H2> <P><b>pamflip</b> replaced <b>pnmflip</b> in Netpbm 10.13 (December 2002). <b>pamflip</b> is backward compatible, but also works on PAM images. -<H2>AUTHOR</H2> +<H2 id="author">AUTHOR</H2> Copyright (C) 1989 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="#lbAE">OPTIONS</A> -<li><A HREF="#lbAF">SEE ALSO</A> +<li><A HREF="#synopsis">SYNOPSIS</A> +<li><A HREF="#description">DESCRIPTION</A> +<li><A HREF="#options">OPTIONS</A> +<li><A HREF="#seealso">SEE ALSO</A> <li><A HREF="#history">HISTORY</A> -<li><A HREF="#lbAG">AUTHOR</A> +<li><A HREF="#author">AUTHOR</A> </UL> </BODY> </HTML> |