R-beta: graphics: ``gamma correction'' -- state / feedback ?

Martin Maechler (maechler@stat.math.ethz.ch)
Thu, 6 Nov 1997 20:08:01 +0100


Date: Thu, 6 Nov 1997 20:08:01 +0100
Message-Id: <199711061908.UAA05479@sophie.ethz.ch>
From: Martin Maechler <maechler@stat.math.ethz.ch>
To: R-help@stat.math.ethz.ch
Subject: R-beta: graphics: ``gamma correction'' -- state / feedback ?

In 'CHANGES' of 0.49, you find among "NEW FEATURES"

 o  There is a new graphical parameter "gamma" which is designed to
    let users apply a ``gamma'' correction for their graphics
    displays.  Most monitors produce a color intensity which is
    related to voltage by the equation
			intensity = voltage ^ gamma
    with gamma about 2.5 for most PC monitors.  A typical symptom
    of this non-linearity is that a colorwheel produced by
			piechart(rep(1,48), col=48)
    shows a marked over representation of the red, green and blue
    and blue primaries.  If this is the case try
			par(gamma=1/2.5)
    and redraw the color wheel.  Vary gamma till you have a "nice"
    spectrum.  This is experimental and feedback would be welcome.
	       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    (If this is useful we will do the same for postscript).
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

		(underlines "~~" by me).

- What is the state of this?  
- Is it still experimental?  
- Does it also work in postscript?
- Who of you R users has used it?  successfully?
- if yes, can you dig out a nice example of its use?

The main reason for my questions is that I am updating the online
documentation,  and I'd like to write something in (at least)
	?hsv   and   ?par

Thank you for your feedback!
{{If you are not one of R&R, 
  you also may e-mail to me alone, and I'll summarize to the list ..}}

----

Martin Maechler <maechler@stat.math.ethz.ch>		 <><
Seminar fuer Statistik, SOL G1
ETH (Federal Inst. Technology)	8092 Zurich	 SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1086
http://www.stat.math.ethz.ch/~maechler/
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