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Diffstat (limited to 'ppmwheel.html')
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1 files changed, 55 insertions, 10 deletions
diff --git a/ppmwheel.html b/ppmwheel.html index ff62a609..3328cf7b 100644 --- a/ppmwheel.html +++ b/ppmwheel.html @@ -2,7 +2,7 @@ <HTML><HEAD><TITLE>Ppmwheel User Manual</TITLE></HEAD> <BODY> <H1>ppmwheel</H1> -Updated: 13 January 2019 +Updated: 03 February 2019 <BR> <A HREF="#index">Table Of Contents</A> @@ -13,6 +13,9 @@ ppmwheel - make a PPM image of a color wheel <B>ppmwheel</B> <I>diameter</I> +[{<b>-huevalue</b> | <b>-huesaturation</b>}] +[<b>-maxval=</b><I>N</I>] + <H2 id="description">DESCRIPTION</H2> @@ -21,19 +24,60 @@ ppmwheel - make a PPM image of a color wheel <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 are distributed -radially and the saturation is 100% everywhere. The values are zero at -the center, increasing linearly to maximum at the edge. The maximum value -corresponds to the maxval of the PPM image. +<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>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. +<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>None. +<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> @@ -55,6 +99,7 @@ Copyright (C) 1995 by Peter Kirchgessner <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> |