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Re:physical colors and Mathematica colors

• To: mathgroup at smc.vnet.net
• Subject: [mg26418] Re:[mg26392] physical colors and Mathematica colors
• From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
• Date: Wed, 20 Dec 2000 00:21:40 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Preston Nichols wrote:
I am working on a package for which I need a function which takes a
wavelength of light (in nanometers, for example) and returns an RGBColor
specification. Has anyone made such a function for Mathematica? 
Of course, it is not essential that the result be RGBColor; any other
standard computer-graphics color model would do the job (HSB, HLS, CMY,
CMYK, etc.), because the conversions are standard. It's only the conversion
between one of these and physical wavelengths which I don't know.
-------------------

As you explore different regions of Hue[h,s,b], RGBColor[r,g,b] you might
find my ColorPlot Mathematica package helpful. With it you can make a color
wheel or a rectangle containing all shades in a certain region of Hue or
RGBColor space.  Download the package from 
 http://www.mathsource.com/cgi-bin/msitem?0210-700


I was able to use the package to empirically find approximations for several
colors in a Rainbow. They are:
 
  Red  - Hue[0,1,1] 
Orange - Hue[1/12,6/10,1]  
Yellow - Hue[1/6,1,1]
 Green - Hue[1/3,1/2,1]
  Blue - Hue[2/3,1,1]
Violet - Hue[5/6,1,1]


I trust you can find a chart that shows the shades for various wavelengths.
You can then correspond several  wavelengths with the Hue[h,s,b] settings
that produce approximately the same color.  Once you have a sufficient
number of shades paired up you can perform an interpolation between adjacent
colors. You might also find my 'ColorScale' function in the package helpful.
It shows all shades along a linear interpolation between any two shades
using Hue or RGBColor specification.

Notice, Hue[0,1,1]  gives the same color as  Hue[1,1,1].  To get an
interpolation between Violet and Red you should interpolate between
Hue[5/6,1,1] and Hue[1,1,1] respectively.

--------------------
Regards,
Ted Ersek

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