ppmcie - draw a CIE colour chart in a portable pixmap
SYNOPSIS
ppmcie [-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
ppmcie creates a portable pixmap containing a plot of the
CIE ``tongue'' colour chart, showing the colour gamut of
either a standard or user-specified colour system, anno
tated 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 kelvins. The axes
are labeled with the CIE X and Y coordinates, the periph
ery 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 kelvins.
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
primary 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 pri
maries specified by the NTSC broadcasting system
(few modern monitors actually cover this range).
-smpte selects the primaries recommended by the
Society of Motion Picture and Television Engi
neers (SMPTE) in standards RP-37 and RP-145, and
-hdtv uses the much broader HDTV ideal pri
maries. -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 se
lects the custom system.
specifies the CIE x and y co-ordinates of the
green illuminant of the colour system and se
lects 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
interpolation line. By default, the white de
fined 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
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 sys
tem's white point, if -interpwp is specified). These out
of gamut colours are drawn ``subdued'' at 3/4 the intensi
ty of the shades within the gamut unless the -full switch
is specified, in which case in-gamut and out of gamut
colours are not distinguished.
SEE ALSO
ppmdither(1), ppmquant(1), ppm(5)
AUTHOR
Copyright (C) 1995 by John Walker (kelvin@fourmilab.ch)
WWW home page: http://www.fourmilab.ch/
Permission to use, copy, modify, and distribute this soft
ware and its documentation for any purpose and without fee
is hereby granted, without any conditions or restrictions.
This software is provided ``as is'' without express or im
plied warranty.
Man(1) output converted with
man2html