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diff --git a/pbmnoise.html b/pbmnoise.html new file mode 100644 index 00000000..19d9be03 --- /dev/null +++ b/pbmnoise.html @@ -0,0 +1,169 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.3//EN"> +<html><head><title>Pbmnoise User Manual</title></head> +<body> +<h1>pgmnoise</h1> +Updated: 18 December 2021 +<br> +<a href="#index">Table Of Contents</a> + +<h2>NAME</h2> +pbmnoise - create a PBM image made up of white noise + +<h2 id="synopsis">SYNOPSIS</h2> + +<b>pbmnoise</b> <i>width</i> <i>height</i> + +[<b>-ratio=</b><i>M</i><b>/</b><i>N</i>] +[<b>-pack</b>] +[<b>-randomseed=</b><i>integer</i>] +[<b>-endian=</b>]{<b>big</b>|<b>little</b>|<b>native</b>|<b>swap</b>}] + +<p>Minimum unique abbreviations of option are acceptable. You may use double +hyphens instead of single hyphen to denote options. You may use white space +in place of the equals sign to separate an option name from its value. + +<h2 id="description">DESCRIPTION</h2> + +<p>This program is part of <a href="index.html">Netpbm</a>. + +<p><b>pbmnoise</b> creates a PBM image with random pixels. You specify the +probability each pixel will be black or white (essentially, the proportion of +black to white pixels in the image). + +<p>You specify the dimensions of the image with the <i>width</i> and +<i>height</i> arguments. + + +<h2 id="options">OPTIONS</h2> + +<p>In addition to the options common to all programs based on libnetpbm (most +notably <b>-quiet</b>, see <a href="index.html#commonoptions"> Common +Options</a>), <b>pbmnoise</b> recognizes the following command line options: + +<dl> +<dt><b>-ratio=</b><i>M</i><b>/</b><i>N</i> +<dd>The proportion of black pixels in the generated image. + +<p>To be precise, this is the probability that any given pixel will be black. +By the law of large numbers, we can expect the proportion of black pixels in a +reasonably large image to be close to this fraction. + +<p>The option value is a fraction. The denominator must be 1 or an integer +power of 2 up to 65536. the numerator must be 0 or a positive integer not +exceeding denominator. + +<p>The default is 1/2, meaning the output image has essentially the same +number of black and white pixels. + +<p>If the ratio is 0 the output image is entirely white. If 1, the output is +entirely black. + +<dt><b>-pack</b> +<dd> +The program generates pixels in 32-bit units discarding any fractional pixels +at row ends by default. When this option is specified, the unused pixels are +carried over to the next row, eliminating waste in exchange for some overhead +cost. + +<p>Using this option improves performance when the image width is small. + +<dt><b>-randomseed=</b><i>integer</i> +<dd> +This is the seed for the random number generator that generates the pixels. + +<p>Use this to ensure you get the same image on separate invocations. + +<p>By default, <b>pbmnoise</b> uses a seed derived from the time of day and +process ID, which gives you fairly uncorrelated results in multiple +invocations. + +<dt><b>-endian=</b><i>mode</i> +<dd> +<b>pbmnoise</b> internally generates random 32-bit integers and uses the +machine's binary encoding of those integers as strings of pixels. Because the +integers are random, it doesn't normally matter what binaary encoding is used +for them, but if you need consistent results between machines using the same +random number generator, it matters. For that reason (mainly for testing the +program), this option lets you control that encoding, between big-endian and +little-endian. + +<p><i>mode</i> is one of the following: + +<dl compact> +<dt><b>big</b> +<dd> +Force big-endian output by rearranging bytes on little-endian machines. No +effect on big-endian machines. + +<dt><b>little</b> +<dd> +Likewise, force little-endian output. + +<dt><b>native</b> + +<dd> +Do not rearrange anything. This is the default. + +<dt><b>swap</b> +<dd> +Always swap regardless of system endianness. +</dl> +</dl> + + +<h2 id="examples">EXAMPLES</h2> + +<p>This generates a random PBM image with roughly one-third of pixels colored +black: +<pre><code> + pbmnoise -ratio=11/32 1200 1200 > random.pbm +</code></pre> + +<p>The following is an alternate method for generating a random PBM image +which uses <b>pgmnoise</b> and <b>pgmtopbm</b> instead of <b>pbmnoise</b>. It +is less efficient. +<pre><code> + pgmnoise -maxval=100 1200 1200 | \ + pgmtopbm -threshold -value=0.333 > random.pbm +</code></pre> + +<p>This generates a random PPM image, maxval 1: +<pre><code> + pbmnoise 600 400 > red.pbm + pbmnoise 600 400 > green.pbm + pbmnoise 600 400 > blue.pbm + rgb3topbm red.pbm green.pbm blue.pbm > random.ppm +</code></pre> + + +<h2 id="seealso">SEE ALSO</h2> + +<a href="pbm.html">pbm</a> +<a href="pgmnoise.html">pgmnoise</a> +<a href="pgmnoise.html">pgmtopbm</a> + +<h2 id="history">HISTORY</h2> + +<p><b>pbmnoise</b> was new in Netpbm 10.97 (December 2021). + +<p>In Netpbm before that, you can use <b>pgmnoise</b>. + + +<h2 id="author">AUTHOR</h2> +<p> +Akira F Urushibata wrote this program and contributed it to the public domain +in December 2021. +<p> + +<hr> +<h2 id="index">Table Of Contents</h2> +<ul> +<li><a href="#synopsis">SYNOPSIS</a> +<li><a href="#description">DESCRIPTION</a> +<li><a href="#options">OPTIONS</a> +<li><a href="#examples">EXAMPLES</a> +<li><a href="#seealso">SEE ALSO</a> +<li><a href="#author">AUTHOR</a> +</ul> +</body> +</html> |