NAME

       ppmwheel - make a PPM image of a color wheel

SYNOPSIS

       ppmwheel diameter [{-huevalue | -huesaturation}] [-maxval=N]

DESCRIPTION

       This program is part of Netpbm(1).

       ppmwheel  produces  a  PPM image of a color wheel of the specified diameter inside a white
       square just large enough to hold it.

       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.

       You can generate three kinds of color wheel:

       •      Hue-value: Select this with a -huevalue option.

              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.

              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.

       •      Hue-saturation: Select this with a -huesaturation option.

              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.

       •      Ppmcirc: Select this by not specifying any other wheel type option.

              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 ppmwheel from its inception in 2003 to 2019.

ARGUMENTS

       You must specify one non-option argument: the radius of the color wheel in pixels.

       This is also the height and width of the output image.

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common  Options  ⟨index.html#commonoptions⟩  ), ppmwheel recognizes the following command
       line options:

       -huevalue

              This selects a hue-value color wheel.

              This option was new in Netpbm 10.86 (March 2019).

       -huesaturation

              This selects a hue-saturation color wheel.

              This option was new in Netpbm 10.86 (March 2019).

       -maxval=N

              This selects the maxval for the image.  The default is 255.

              This option was new in Netpbm 10.86 (March 2019).

SEE ALSO

       ppmcie(1), ppmrainbow(1), ppm(1)

HISTORY

       ppmwheel was added to Netpbm in Release 10.14 (March 2003).

AUTHOR

       Copyright (C) 1995 by Peter Kirchgessner

DOCUMENT SOURCE

       This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The  master
       documentation is at

              http://netpbm.sourceforge.net/doc/ppmwheel.html