Ppmwheel User Manual(1) General Commands Manual Ppmwheel User Manual(1)
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 dis-
tributed
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 op-
tion.
The saturation is 100% everywhere. The value is a strange func-
tion 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 dis-
tance 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 ]8;;index.html#commonoptions\ Common Options]8;;\ ), 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
netpbm documentation 03 February 2019 Ppmwheel User Manual(1)
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