Black preservation

Hi Larry,

The actual K-preservation implementation is just a
first try. I am pretty sure there is a lot of room for
improvement. So, I would be happy to know of
cases where the actual algorithm does NOT work,
specifically, if you can send me the involved profiles
I would be very gratefull.

Regards
Marti Maria
The littleCMS project
http://www.littlecms.com



----- Original Message ----- 
From: Larry Tseng
To: lcms-userlists.sourceforge.net
Sent: Thursday, March 09, 2006 2:25 AM
Subject: [Lcms-user] Black preservation


Hello list,

I find the preserve black feature to be very helpful in cmyk
to cmyk 
conversions when k-only images, text and graphics should
remain k-only after 
the conversion. Lcms does this nicely, and with proper
k-only tone 
compensation as well. Unfortunately, "colorful"
cmyk text and images can 
experience large color shifts, enough to render the feature
unusable, and 
very problematic in situations where both k-only and
colorful cmyk material 
are both present in the source.

I am wondering whether the idea of
"clean-blacks", as implemented in 
devicelink profiles created by ColorThink Pro, Link-o-lator,
and 
GretagMacBeth, isn't the better way to go. Here, cmyk
converts in the usual 
way except for the special case of k, where c=m=y=0%, which
is subjected to 
a k-only to k-only transform.

Regards,

Larry Tseng 



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