ppmcie

 

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 PPMCIE(1)                                               PPMCIE(1)
 
 
 
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, 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.
 
        -green gx gy
                  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
        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 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.
 
 
 
                        26th September 1994              PPMCIE(1)

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