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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.3//EN">
<html><head><title>Ppmwheel User Manual</title></head>
<body>
<h1>ppmwheel</h1>
Updated: 03 February 2019
<br>
<a href="#index">Table Of Contents</a>
<h2>NAME</h2>
ppmwheel - make a PPM image of a color wheel
<h2 id="synopsis">SYNOPSIS</h2>
<b>ppmwheel</b>
<i>diameter</i>
[{<b>-huevalue</b> | <b>-huesaturation</b>}]
[<b>-maxval=</b><i>N</i>]
<h2 id="description">DESCRIPTION</h2>
<p>This program is part of <a href="index.html">Netpbm</a>.
<p><b>ppmwheel</b> produces a PPM image of a color wheel of the
specified diameter inside a white square just large enough to hold it.
<p>The color wheel is based on the HSV color model. Hues are distributed
angularly around the circle and the values and saturations are distributed
radially.
<p>You can generate three kinds of color wheel:
<ul>
<li>Hue-value: Select this with a <b>-huevalue</b> option.
<p>The saturation is 100% everywhere. The value goes from zero to 100%
linearly, from the center of the wheel to the edge. So the center is black.
<p>Hence, the image consists of all of the secondary colors based on the
red, green, and blue primary colors. A secondary color is one that is
composed of light of at most two of the three primary colors.
<li>Hue-saturation: Select this with a <b>-huesaturation</b> option.
<p>The value is 100% everywhere. The saturation goes from zero to 100%
linearly, from the center of the wheel to the edge. So the center is white.
<li>Ppmcirc: Select this by not specifying any other wheel type option.
<p>The saturation is 100% everywhere. The value is a strange function of
the distance from the center, increasing as the square root of the distance
until halfway out, then decreasing as the 8th root of the distance the rest
of the way. We don't know what the point of this is, but it is what the
program Ppmcirc by Peter Kirchgessner in 1995 does, and was the only option
in <b>ppmwheel</b> from its inception in 2003 to 2019.
</ul>
<h2 id="arguments">ARGUMENTS</h2>
<p>You must specify one non-option argument: the radius of the color wheel
in pixels.
<p>This is also the height and width of the output image.
<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>ppmwheel</b> recognizes the following
command line options:
<dl>
<dt><b>-huevalue</b>
<dd>This selects a hue-value color wheel.
<p>This option was new in Netpbm 10.86 (March 2019).
<dt><b>-huesaturation</b>
<dd>This selects a hue-saturation color wheel.
<p>This option was new in Netpbm 10.86 (March 2019).
<dt><b>-maxval=</b><i>N</i>
<dd>This selects the maxval for the image. The default is 255.
<p>This option was new in Netpbm 10.86 (March 2019).
</dl>
<h2 id="seealso">SEE ALSO</h2>
<b><a href="ppmcie.html">ppmcie</a></b>,
<b><a href="ppmrainbow.html">ppmrainbow</a></b>,
<b><a href="ppm.html">ppm</a></b>
<h2 id="history">HISTORY</h2>
<p><b>ppmwheel</b> was added to Netpbm in Release 10.14 (March 2003).
<h2 id="author">AUTHOR</h2>
Copyright (C) 1995 by Peter Kirchgessner
<hr>
<h2 id="index">Table Of Contents</h2>
<ul>
<li><a href="#synopsis">SYNOPSIS</a>
<li><a href="#description">DESCRIPTION</a>
<li><a href="#arguments">ARGUMENTS</a>
<li><a href="#options">OPTIONS</a>
<li><a href="#seealso">SEE ALSO</a>
<li><a href="#history">HISTORY</a>
<li><a href="#author">AUTHOR</a>
</ul>
</body>
</html>
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