Path: utzoo!attcan!darkover!nebulus!druid!darcy
From: darcy@druid.uucp (D'Arcy J.M. Cain)
Newsgroups: comp.graphics
Subject: Re: RGB ---> YMCK
Message-ID: <1990Feb10.151544.19088@druid.uucp>
Date: 10 Feb 90 15:15:44 GMT
References: <1990Feb7.220805.27260@allgfx.agi.oz> <260002@hplred.HP.COM>
Reply-To: darcy@druid.UUCP (D'Arcy J.M. Cain)
Organization: D'Arcy Cain Consulting, West Hill, Ontario
Lines: 25

In article <260002@hplred.HP.COM> piety@hplred.HP.COM (Bob Piety) writes:
>Given components in the 0..1 range,
>
>C = 1 - R
>M = 1 - G
>Y = 1 - B
>K = .59R + .30G + .11B = Luminance

I previously posted a different algorithm for this problem and it appears
now that I may have been wrong (not a first for me :-) ).  My algorithm
basically subtracted an equal amount from each of the resulting C, M and Y
values making this subtracted amount the black component.  I recognize the
RGB->Greyscale calculation in the above statement and I can understand that
the different components might have differing weights in the calculation but
doesn't the black component, at least to some extent, have to be adjusted
by reducing the CMY components.  Is the above generally accepted.  None of
the texts I have seen really details this algorithm.

Thanks for your help.

-- 
D'Arcy J.M. Cain (darcy@druid)     |   Thank goodness we don't get all 
D'Arcy Cain Consulting             |   the government we pay for.
West Hill, Ontario, Canada         |
(416) 281-6094                     |