PPMCIE
Section: User Commands (1)
Updated: 26th September 1994
Index
Return to Main Contents
NAME
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, 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 kelvins. 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 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 primaries 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 Engineers (SMPTE) in standards 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 default 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
defined by an equal mix of the three primaries is used.
All flags can be abbreviated to their shortest unique prefix.
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 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 software 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 implied warranty.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- BUGS
-
- SEE ALSO
-
- AUTHOR
-
This document was created by
man2html,
using the manual pages.
Time: 16:15:56 GMT, July 31, 2024