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From: palmerj@westminster.ac.uk (Jake Palmer)
Subject: Re: RGB to HCV conversion
Message-ID: <CxIBuG.45E@westminster.ac.uk>
Organization: University of Westminster
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Date: Tue, 11 Oct 1994 11:56:40 GMT
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Xref: glinda.oz.cs.cmu.edu sci.image.processing:10245 comp.graphics:62670

tyshih@cc.nctu.edu.tw wrote:
: Dear Asha:

: Pratt, 1991.  Digital Image Processing. Wiley. pp70-71 provides
: transformation from RGB to Luv, then take the equation on pp 72

As do a number of books, but it cannot be done like that. Think
about it: Computer RGB is some internal representation that 
gives a pleasing rendition with any old monitor, graphics card;
CIE LUV is a quantitative, defined description of the viewed
output colour.  Suppose you change your monitor, display the 
colour on a different system, or just twiddle with the knobs
on the front...Your RGB has not changed-nor indeed the L*u*v* you
calculated using Pratt's (or anyone's) transformation,  but it
should be clear to any wombat that the displayed colour is 
different, so the *REAL*  CIELUV values have changed.

If anyone really wants to calculate CIELUV from RGB then consult
various papers by R Berns and be prepared for a lot of work.

Jake Palmer
Imaging Technology Research Group.

