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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2020-06-28 21:56:20 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2020-06-28 21:56:20 +0000 |
| commit | 85b85b4ff98bc89a853529b318b205a8a798dc6f (patch) | |
| tree | 2ccba5cccf61f60b1df619b5815b99746ddec9f7 /pnmscalefixed.html | |
| parent | 0653136526daf503445f03c46daa23297f9a4296 (diff) | |
| download | netpbm-mirror-85b85b4ff98bc89a853529b318b205a8a798dc6f.tar.gz netpbm-mirror-85b85b4ff98bc89a853529b318b205a8a798dc6f.tar.xz netpbm-mirror-85b85b4ff98bc89a853529b318b205a8a798dc6f.zip | |
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git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@3879 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'pnmscalefixed.html')
| -rw-r--r-- | pnmscalefixed.html | 92 |
1 files changed, 65 insertions, 27 deletions
diff --git a/pnmscalefixed.html b/pnmscalefixed.html index 27fc5d9c..ad8b7ebf 100644 --- a/pnmscalefixed.html +++ b/pnmscalefixed.html @@ -1,48 +1,48 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN"> -<HTML><HEAD><TITLE>Pnmscalefixed User Manual</TITLE></HEAD> -<BODY> -<H1>pnmscalefixed</H1> -Updated: 18 November 2000 -<BR> -<A HREF="#index">Table Of Contents</A> +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.3//EN"> +<html><head><title>Pnmscalefixed User Manual</title></head> +<body> +<h1>pnmscalefixed</h1> +Updated: 28 June 2020 +<br> +<a href="#index">Table Of Contents</a> -<H2>NAME</H2> +<h2>NAME</h2> pnmscalefixed - scale a PNM file quickly -<H2 id="description">DESCRIPTION</H2> +<h2 id="description">DESCRIPTION</h2> <p>This program is part of <a href="index.html">Netpbm</a>. -<B>pnmscalefixed</B> is like <B>pamscale</B> except that +<b>pnmscalefixed</b> is like <b>pamscale</b> except that it uses fixed point arithmetic internally instead of floating point, which may make it run faster. In turn, it is less accurate and may distort the image. It also lacks many of the features of <b>pamscale</b>. -<P>Use the <B>pamscale</B> user manual with <B>pnmscalefixed</B>. This +<p>Use the <b>pamscale</b> user manual with <b>pnmscalefixed</b>. This document only describes the difference. Avoid any feature mentioned in the <b>pamscale</b> manual as not existing before Netpbm 9.9. -<P><B>pnmscalefixed</B> uses fixed point 12 bit arithmetic. By -contrast, <B>pamscale</B> uses floating point arithmetic which on most +<p><b>pnmscalefixed</b> uses fixed point 12 bit arithmetic. By +contrast, <b>pamscale</b> uses floating point arithmetic which on most machines is probably 24 bit precision. This makes -<B>pnmscalefixed</B> run faster (30% faster in one experiment), but +<b>pnmscalefixed</b> run faster (30% faster in one experiment), but the imprecision can cause distortions at the right and bottom edges. -<P>The distortion takes the following form: One pixel from the edge of +<p>The distortion takes the following form: One pixel from the edge of the input is rendered larger in the output than the scaling factor requires. Consequently, the rest of the image is smaller than the scaling factor requires, because the overall dimensions of the image are always as requested. This distortion will usually be very hard to see. -<P><B>pnmscalefixed</B> with the <B>-verbose</B> option tells you how +<p><b>pnmscalefixed</b> with the <b>-verbose</b> option tells you how much distortion there is. -<P>The amount of distortion depends on the size of the input image and how +<p>The amount of distortion depends on the size of the input image and how close the scaling factor is to an integral 1/4096th. -<P>If the scaling factor is an exact multiple of 1/4096, there is no +<p>If the scaling factor is an exact multiple of 1/4096, there is no distortion. So, for example doubling or halving an image causes no distortion. But reducing it or enlarging it by a third would cause some distortion. To consider an extreme case, scaling a 100,000 row @@ -50,19 +50,57 @@ image down to 50,022 rows would create an output image with all of the input squeezed into the top 50,000 rows, and the last row of the input copied into the bottom 22 rows of output. -<P><B>pnmscalefixed</B> could probably be modified to use 16 bit or +<p><b>pnmscalefixed</b> could probably be modified to use 16 bit or better arithmetic without losing anything. The modification would consist of a single constant in the source code. Until there is a demonstrated need for that, though, the Netpbm maintainer wants to keep the safety cushion afforded by the original 12 bit precision. -<P><B>pnmscalefixed</B> does not have <B>pamscale</b>'s <B>-nomix</B> +<p><b>pnmscalefixed</b> does not have <b>pamscale</b>'s <b>-nomix</b> option. -<HR> -<H2 id="index">Table Of Contents</H2> -<UL> -<LI><A HREF="#description">DESCRIPTION</A> -</UL> -</BODY> -</HTML> +<h2 id="options">OPTIONS</h2> + +<dl compact> +<dt><b>-xsize</b> + +<dt><b>-width</b> + +<dt><b>-ysize</b> + +<dt><b>-height</b> + +<dt><b>-xscale</b> + +<dt><b>-yscale</b> + +<dt><b>-pixels</b> + +<dt><b>-xysize</b> + +<dt><b>-reduce</b> + +<dt><b>-verbose</b> + +<dd>Same as <a href="pamscale.html"><b>pamscale</b></a>. +</dl> + +<h2 id="seealso">SEE ALSO</h2> + +<ul> + <li><a href="pamscale.html"><b>pamscale</b></a> + <li><a href="pnmscale.html"><b>pnmscale</b></a> +</ul> + +<hr> +<h2 id="index">Table Of Contents</h2> +<ul> +<li><a href="#description">DESCRIPTION</a> +<li><a href="#options">OPTIONS</a> +<li><a href="#seealso">SEE ALSO</a> +</ul> +</body> +</html> + + + |