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From: hoffmann@fho-emden.de (Gernot Hoffmann)
Newsgroups: comp.graphics.algorithms
Subject: Re: CMYK to GrayScale Conversion ?
Date: 5 Dec 2002 11:39:26 -0800
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vishak@postmark.net (Vishak) wrote in message news:<480936aa.0212042137.44ced98@posting.google.com>...
> I am in the look out for the equation (/algorithm)to convert CMYK to GrayScale.
> Any sort of pointers, sample code is highly appriciated.
> 
> Thanks in Advance,
> 
> Vishak.

Warning:

In one of the posts you will find this link:
http://www.easyrgb.com/math.html

Donīt believe the wisdom there.

a) CMYK to CMY depends on the UCR/GCR mode.
   (Undercolor Removal, Gray Component Replacement)
   This is the strategy, how much of the common value of C,M,Y
   is replaced by K.

b) The so called dot gain is not taken into account.
   This says: use lower CMYK numbers because the dot becomes
   larger on the paper. 

c) CMY to RGB depends on gamut compression, gamut clipping,
   RGB primaries definition, white point definition.
   RGB - CMY - RGB is NOT reversible.
   The naive formula  R=1-C and so on is wrong.

d) Inverse Gamma distortion for the monitor is not taken into 
   account.

   If the CMYK has an embedded profile, then the conversion
   is better, but very complex.

   A Google search "CMYK RGB" shows immediately, how difficult
   this problem is.

Perhaps "Little Color Management" can help further ...

Best regards  --Gernot Hoffmann