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RedHat 9 (Linux i386) - man page for ppmcie (redhat section 1)

PPMCIE(1)			     General Commands Manual				PPMCIE(1)

NAME
       ppmcie - draw a CIE color chart as a PPM image

SYNOPSIS
       ppmcie [-rec709|-cie|-ebu|-hdtv|-ntsc|-smpte] [-xy|-upvp] [-red rx ry] [-green gx gy]
		[-blue bx by] [-white wx wy] [-size edge] [-xsize|-width width] [-ysize|-height
		height] [-noblack] [-nowpoint] [-nolabel] [-noaxes] [-full]

       All options can be abbreviated to their shortest unique prefix.

DESCRIPTION
       ppmcie  creates	a  PPM file containing a plot of the CIE ``tongue'' color chart -- to the
       extent possible in a PPM image.	Alternatively, creates a pseudo-PPM image  of  the  color
       tongue using RGB values from a color system of your choice.

       The  CIE  color	tongue is an image of all the hues that can be described by CIE X-Y chro-
       maticity coordinates.  They are arranged on a two dimensional coordinate plane with the	X
       chromaticity  on  the  horizontal axis and the Y chromaticity on the vertical scale.  (You
       can choose alternatively to use CIE u'-v' chromaticity coordinates, but the  general  idea
       of the color tongue is the same).

       Note  that  the PPM format specifies that the RGB values in the file are from CIE Rec. 709
       color system, gamma-corrected.  And positive.  See ppm(5) for details.  If you use one  of
       the color system options on ppmcie, what you get is not a true PPM image, but is very sim-
       ilar.  If you display such ppmcie output using a device that expects PPM input (which  in-
       cludes  just  about any computer graphics display program), it will display the wrong col-
       ors.

       However, you may have a device that expects one of these variations on PPM.

       In every RGB color system you can specify, including the default (which	produces  a  true
       PPM  image)  there  are	hues in the color tongue that can't be represented.  For example,
       monochromatic blue-green with a wavelength of 500nm cannot be represented in a PPM image.

       For these hues, ppmcie substitutes a similar hue as follows: They are desaturated and ren-
       dered as the shade where the edge of the Maxwell triangle intersects a line drawn from the
       requested shade to the white point defined by the color system's  white	point.	 Further-
       more,  unless you specify the -full option, ppmcie reduces their intensity by 25% compared
       to the true hues in the image.

       ppmcie draws and labels the CIE X-Y coordinate axes unless you choose otherwise	with  op-
       tions.

       ppmcie  draws  the  Maxwell triangle for the color system in use on the color tongue.  The
       Maxwell triangle is the triangle whose vertices are the primary illuminant  hues  for  the
       color  system.	The  hues  inside the triangle show the color gamut for the color system.
       They are also the only ones that are correct for  the  CIE  X-Y	chromaticity  coordinates
       shown.  (See explanation above).

       ppmcie  also  places a mark at the color system's white point and displays in text the CIE
       X-Y chromaticities of the primary illuminants and white point for the color  system.   You
       can turn this off with options, though.

       ppmcie  annotates  the periphery of the color tongue with the wavelength, in nanometers of
       the monochromatic hues which appear there.

       Finally, ppmcie displays the black body chromaticity curve for  Planckian  radiators  from
       1000 to 30000 kelvins on the image.

       You  can choose from several standard color systems, or specify one of your own numerical-
       ly.

       CIE charts, by their very nature, contain a very large number of colors.  If you're encod-
       ing the chart for a color mapped device or file format, you'll need to use ppmquant or pp-
       mdither to reduce the number of colors in the image.

OPTIONS
       -rec709|-cie|-ebu|-hdtv|-ntsc|-smpte
		 Select a standard color system whose gamut to plot.   The  default  is  -rec709,
		 which	chooses CIE Rec. 709, gamma-corrected.	This is the only color system for
		 which ppmcie's output is a true PPM image.  See explanation above.  -ebu chooses
		 the  primaries  used in the PAL and SECAM broadcasting standards.  -ntsc chooses
		 the primaries specified by the NTSC broadcasting system (few modern monitors ac-
		 tually cover this range).  -smpte selects the primaries recommended by the Soci-
		 ety of Motion Picture and Television Engineers (SMPTE) in  standards  RP-37  and
		 RP-145,  and  -hdtv  uses the much broader HDTV ideal primaries.  -cie chooses a
		 color system that has the largest possible gamut  within  the	spectrum  of  the
		 chart.   This	is  the same color system as you get with the -cie option to John
		 Walker's cietoppm program.

       -xy	 plot CIE 1931 x y chromaticities.  This is the default.

       -upvp	 plot u' v' 1976 chromaticities rather than CIE 1931 x y chromaticities.  The ad-
		 vantage  of  u'  v' coordinates is that equal intervals of distance on the u' v'
		 plane correspond roughly to the eye's ability to discriminate colors.

       -red rx ry
		 specifies the CIE x and y co-ordinates of the red illuminant of a  custom  color
		 system and selects the custom system.

       -green gx gy
		 specifies the CIE x and y co-ordinates of the green illuminant of the color sys-
		 tem and selects the custom system.

       -blue bx by
		 specifies the CIE x and y co-ordinates of the blue illuminant of the color  sys-
		 tem and selects the custom system.

       -white wx wy
		 specifies  the  CIE  x and y co-ordinates of the white point of the color 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 dia-
		 gram will be stretched in the longer dimension.

       -noblack  Don't plot the black body chromaticity curve.

       -nowpoint Don't plot the color system's white point.

       -nolabel  Omit the label.

       -noaxes	 Don't plot axes.

       -full	 Plot the entire CIE tongue in full intensity; don't enhance  the  gamut  of  the
		 specified color system.

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.

				       26th September 1994				PPMCIE(1)


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