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CIETOPPM(1) USER COMMANDS CIETOPPM(1)
NAME
cietoppm - draw a CIE colour chart in a portable pixmap
SYNOPSIS
cietoppm [-noblack] [-nowpoint] [-interpwp] [-full]
[-cie|-ebu|-hdtv |-ntsc|-smpte] [-red rx ry]
[-green gx gy] [-blue bx by] [-white wx wy] [-size
edge] [-xsize|-width width] [-ysize|-height height]
DESCRIPTION
cietoppm creates a portable pixmap containing a plot of the
CIE ``tongue'' colour chart, showing the colour gamut of ei-
ther a standard or user-specified colour system, annotated
with axes, a mark indicating the white point of the colour
system, and the black body chromaticity curve for Planckian
radiators from 1000 to 30000 degrees Kelvin. The axes are
labeled with the CIE X and Y coordinates, the periphery of
the tongue is annotated with the wavelength of light, in
nanometres, of the pure hues which appear there, and the
black body chromaticity curve is marked with the temperature
in degrees Kelvin.
CIE charts, by their very nature, contain a very large
number of colours. If you're encoding the chart for a
colour mapped device or file format, you'll need to use
ppmquant or ppmdither to reduce the number of colours in the
image.
OPTIONS
-cie|-ebu|-hdtv|-ntsc|-smpte
Select a standard colour system whose gamut (the
area inside the triangle formed by the three pri-
mary colours) and white point are plotted within
the CIE tongue chart. The default is -ebu, the
primaries used in the PAL and SECAM broadcasting
standards. -ntsc chooses the primaries specified
by the NTSC broadcasting system (few modern moni-
tors actually cover this range). -smpte selects
the primaries recommended by the Society of Motion
Picture and Television Engineers (SMPTE) in stan-
dards RP-37 and RP-145, and -hdtv uses the much
broader HDTV ideal primaries. -cie uses the CIE
RGB primaries with wavelengths of 700 nm, 546.1
nm, and 438.8 nm respectively; the CIE white point
is defined by equal R, G, and B intensities.
-red rx ry
specifies the CIE x and y co-ordinates of the red
illuminant of a custom colour system and selects
the custom system.
-green gx gy
specifies the CIE x and y co-ordinates of the
green illuminant of the colour system and selects
the custom system.
-blue bx by
specifies the CIE x and y co-ordinates of the blue
illuminant of the colour system and selects the
custom system.
-white wx wy
specifies the CIE x and y co-ordinates of the
white point of the colour system and selects the
custom system.
-size edge
Create a pixmap of edge by edge pixels. The de-
fault is 512x512.
-xsize|-width width
Sets the width of the generated image to width
pixels. The default width is 512 pixels. If the
height and width of the image are not the same,
the CIE diagram will be stretched in the longer
dimension.
-ysize|-height height
Sets the height of the generated image to height
pixels. The default height is 512 pixels. If the
height and width of the image are not the same,
the CIE diagram will be stretched in the longer
dimension.
-noblack Don't plot the black body chromaticity curve.
-nowhite Don't plot the colour system's white point.
-full Plot the entire CIE tongue in full intensity;
don't enhance the gamut of the specified colour
system.
-interpwp Interpolate out-of-gamut colours using the colour
system's white point as the origin of the interpo-
lation line. By default, the white defined by an
equal mix of the three primaries is used.
All flags can be abbreviated to their shortest unique pre-
fix.
BUGS
Obviously, colours outside the gamut of the device used to
view or print the CIE chart cannot be rendered accurately.
Colours outside the Maxwell's triangle formed by the three
illuminants are desaturated and rendered as the shade where
the edge of the gamut triangle intersects a line drawn from
the requested shade to the white point defined by an equal
mixture of the illuminants (or the colour system's white
point, if -interpwp is specified). These out of gamut
colours are drawn ``subdued'' at 3/4 the intensity of the
shades within the gamut unless the -full switch is speci-
fied, in which case in-gamut and out of gamut colours are
not distinguished.
SEE ALSO
ppmdither(1), ppmquant(1), ppm(5)
AUTHOR
Copyright (C) 1994 by John Walker (kelvin@fourmilab.ch).
WWW home page: http://www.fourmilab.ch/
Permission to use, copy, modify, and distribute this
software and its documentation for any purpose and without
fee is hereby granted, without any conditions or restric-
tions. This software is provided ``as is'' without express
or implied warranty.