362 lines
8.5 KiB
HTML
362 lines
8.5 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of PPMCIE</TITLE>
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</HEAD><BODY>
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<H1>PPMCIE</H1>
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Section: User Commands (1)<BR>Updated: 26th September 1994<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<P>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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ppmcie - draw a CIE color chart as a PPM image
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<P>
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>ppmcie</B>
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[<B>-rec709</B>|<B>-cie</B>|<B>-ebu</B>|<B>-hdtv</B>|<B>-ntsc</B>|<B>-smpte</B>]
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[<B>-xy</B>|<B>-upvp</B>]
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[<B>-red</B>
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<I>rx</I>
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<I>ry</I>]
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[<B>-green</B>
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<I>gx</I>
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<I>gy</I>]
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[<B>-blue</B>
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<I>bx</I>
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<I>by</I>]
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[<B>-white</B>
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<I>wx</I>
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<I>wy</I>]
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[<B>-size</B>
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<I>edge</I>]
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[<B>-xsize</B>|<B>-width</B>
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<I>width</I>]
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[<B>-ysize</B>|<B>-height</B>
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<I>height</I>]
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[<B>-noblack</B>]
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[<B>-nowpoint</B>]
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[<B>-nolabel</B>]
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[<B>-noaxes</B>]
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[<B>-full</B>]
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<P>
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All options can be abbreviated to their shortest unique prefix.
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<P>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>ppmcie</B>
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creates a PPM file containing a plot of the CIE ``tongue'' color
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chart -- to the extent possible in a PPM image. Alternatively,
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creates a pseudo-PPM image of the color tongue using RGB values from
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a color system of your choice.
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<P>
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The CIE color tongue is an image of all the hues that can be
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described by CIE X-Y chromaticity coordinates. They are arranged on
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a two dimensional coordinate plane with the X chromaticity on the
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horizontal axis and the Y chromaticity on the vertical scale.
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(You can choose alternatively to use CIE u'-v' chromaticity coordinates,
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but the general idea of the color tongue is the same).
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<P>
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Note that the PPM format specifies that the RGB values in the file are
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from CIE Rec. 709 color system, gamma-corrected. And positive. See
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<B><A HREF="/cgi-bin/man/man2html?5+ppm">ppm</A></B>(5)
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for details. If you use one of the color system options on
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<B>ppmcie</B>,
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what you get is not a true PPM image, but is very similar. If you display
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such
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<B>ppmcie</B>
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output using a device that expects PPM input (which includes just about
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any computer graphics display program), it will display the wrong colors.
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<P>
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However, you may have a device that expects one of these variations on
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PPM.
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<P>
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In every RGB color system you can specify, including the default
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(which produces a true PPM image) there are hues in the color tongue
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that can't be represented. For example, monochromatic blue-green with
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a wavelength of 500nm cannot be represented in a PPM image.
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<P>
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For these hues,
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<B>ppmcie</B>
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substitutes a similar hue as follows: They are desaturated and
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rendered as the shade where the edge of the Maxwell triangle
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intersects a line drawn from the requested shade to the white point
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defined by the color system's white point. Furthermore, unless you
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specify the
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<B>-full</B>
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option,
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<B>ppmcie</B>
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reduces their intensity by 25% compared to the true hues in the
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image.
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<P>
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<B>ppmcie</B>
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draws and labels the CIE X-Y coordinate axes unless you choose otherwise
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with options.
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<P>
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<B>ppmcie</B>
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draws the Maxwell triangle for the color system in use on the color
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tongue. The Maxwell triangle is the triangle whose vertices are the
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primary illuminant hues for the color system. The hues inside the
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triangle show the color gamut for the color system. They are also the
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only ones that are correct for the CIE X-Y chromaticity coordinates
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shown. (See explanation above).
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<P>
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<B>ppmcie</B>
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also places a mark at the color system's white point and displays in
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text the CIE X-Y chromaticities of the primary illuminants and white
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point for the color system. You can turn this off with options, though.
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<P>
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<B>ppmcie</B>
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annotates the periphery of the color tongue with the wavelength, in
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nanometers of the monochromatic hues which appear there.
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<P>
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Finally,
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<B>ppmcie</B>
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displays the black body chromaticity curve for Planckian radiators from
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1000 to 30000 kelvins on the image.
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<P>
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You can choose from several standard color systems, or specify one of
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your own numerically.
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<P>
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<P>
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CIE charts, by their very nature, contain a very large number of
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colors. If you're encoding the chart for a color mapped device or
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file format, you'll need to use
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<B>ppmquant</B>
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or
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<B>ppmdither</B>
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to reduce the number of colors in the image.
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<P>
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<A NAME="lbAE"> </A>
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<H2>OPTIONS</H2>
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<DL COMPACT>
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<DT id="1"><B>-rec709</B>|<B>-cie</B>|<B>-ebu</B>|<B>-hdtv</B>|<B>-ntsc</B>|<B>-smpte</B>
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<DD>
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Select a standard color system whose gamut to plot. The default is
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<B>-rec709</B>,
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which chooses CIE Rec. 709, gamma-corrected. This is the only color
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system for which
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<B>ppmcie</B>'s
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output is a true PPM image. See explanation above.
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<B>-ebu</B>
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chooses the primaries used in the PAL and SECAM broadcasting standards.
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<B>-ntsc</B>
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chooses the primaries specified by the NTSC broadcasting system
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(few modern monitors actually cover this range).
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<B>-smpte</B>
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selects the primaries recommended by the Society of Motion
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Picture and Television Engineers (SMPTE) in standards RP-37 and
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RP-145, and
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<B>-hdtv</B>
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uses the much broader
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<I>HDTV ideal</I>
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primaries.
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<B>-cie</B>
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chooses a color system that has the largest possible gamut within the
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spectrum of the chart. This is the same color system as you get with
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the
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<B>-cie</B>
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option to John Walker's
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<B>cietoppm</B>
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program.
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<P>
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<DT id="2"><B>-xy</B>
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<DD>
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plot CIE 1931 x y chromaticities.
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This is the default.
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<DT id="3"><B>-upvp</B>
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<DD>
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plot u' v' 1976 chromaticities rather than CIE 1931 x y chromaticities.
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The advantage of u' v' coordinates is that equal intervals of distance
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on the u' v' plane correspond roughly to the eye's ability to discriminate
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colors.
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<DT id="4"><B>-red</B><I> rx ry</I>
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<DD>
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specifies the CIE
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<I>x</I> and <I>y</I>
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co-ordinates of the red illuminant of a custom color system and selects the
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custom system.
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<DT id="5"><B>-green</B><I> gx gy</I>
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<DD>
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specifies the CIE
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<I>x</I> and <I>y</I>
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co-ordinates of the green illuminant of the color system and selects the
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custom system.
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<DT id="6"><B>-blue</B><I> bx by</I>
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<DD>
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specifies the CIE
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<I>x</I> and <I>y</I>
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co-ordinates of the blue illuminant of the color system and selects the
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custom system.
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<DT id="7"><B>-white</B><I> wx wy</I>
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<DD>
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specifies the CIE
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<I>x</I> and <I>y</I>
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co-ordinates of the white point of the color system and selects the
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custom system.
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<DT id="8"><B>-size</B><I> edge</I>
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<DD>
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Create a pixmap of
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<I>edge</I> by <I>edge</I>
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pixels. The default is 512x512.
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<DT id="9"><B>-xsize|-width</B><I> width</I>
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<DD>
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Sets the width of the generated image to
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<I>width</I>
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pixels. The default width is 512 pixels. If the height and width of
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the image are not the same, the CIE diagram will be stretched in the
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longer dimension.
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<DT id="10"><B>-ysize|-height</B><I> height</I>
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<DD>
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Sets the height of the generated image to
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<I>height</I>
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pixels. The default height is 512 pixels. If the height and width of
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the image are not the same, the CIE diagram will be stretched in the
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longer dimension.
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<DT id="11"><B>-noblack</B>
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<DD>
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Don't plot the black body chromaticity curve.
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<DT id="12"><B>-nowpoint</B>
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<DD>
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Don't plot the color system's white point.
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<DT id="13"><B>-nolabel</B>
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<DD>
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Omit the label.
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<DT id="14"><B>-noaxes</B>
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<DD>
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Don't plot axes.
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<DT id="15"><B>-full</B>
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<DD>
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Plot the entire CIE tongue in full intensity; don't enhance the gamut of
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the specified color system.
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<P>
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</DL>
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<A NAME="lbAF"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+ppmdither">ppmdither</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?1+ppmquant">ppmquant</A></B>(1),
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<B><A HREF="/cgi-bin/man/man2html?5+ppm">ppm</A></B>(5)
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<P>
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<A NAME="lbAG"> </A>
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<H2>AUTHOR</H2>
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<CENTER>
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Copyright (C) 1995 by John Walker (<A HREF="mailto:kelvin@fourmilab.ch">kelvin@fourmilab.ch</A>)<BR>
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WWW home page: <A HREF="http://www.fourmilab.ch/">http://www.fourmilab.ch/</A><BR>
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</CENTER>
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<P>
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Permission to use, copy, modify, and distribute this software and its
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documentation for any purpose and without fee is hereby granted,
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without any conditions or restrictions. This software is provided ``as
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is'' without express or implied warranty.
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="16"><A HREF="#lbAB">NAME</A><DD>
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<DT id="17"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="18"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="19"><A HREF="#lbAE">OPTIONS</A><DD>
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<DT id="20"><A HREF="#lbAF">SEE ALSO</A><DD>
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<DT id="21"><A HREF="#lbAG">AUTHOR</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:24 GMT, March 31, 2021
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</HTML>
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