CIETOPPM(1) CIETOPPM(1) NAME cietoppm - draw a CIE colour chart in a portable pixmap SYNOPSIS cietoppm [-noblack] [-nowpoint] [-nolabel] [-noaxes] [-full] [-cie|-ebu|-hdtv |-ntsc|-smpte] [-red rx ry] [-green gx gy] [-blue bx by] [-white wx wy] [-gamma gamma] [-size edge] [-xsize|-width width] [-ysize|-height height] DESCRIPTION cietoppm 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, an­ notated 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 degrees Kelvin. 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 degrees Kelvin. 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. -gamma gamma specifies the nonlinear gamma correction. The default is to use ITU-R Recommendation BT 709 (1990), which specifies gamma = 1/4.5 = 2.22, modified by small linear ramp near black. The RGB guns on a colour monitor respond nonlinearly to their inputs in a fashion that mimics the nonlinear response of the human eye. The light power emitted by the guns is approximately pro­ portional to the gamma'th power of the RGB lev­ els specified in software, with the result that the eye perceives an approximately linear in­ crease in brightness for a linear increase in RGB. -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. -nowpoint Don't plot the colour 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 colour system. 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 the colour system's white point. These out of gamut colours are drawn ``subdued'' at 3/4 the intensity of the shades within the gamut unless the -full switch is speci­ fied, 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 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.