From: Wolfgang Schuster <wolfgang.schuster.lists@gmail.com>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>,
"Jan U. Hasecke" <juh+ntg-context@mailbox.org>
Subject: Re: Issues with RGB to CMYK conversion with color profiles
Date: Wed, 14 Nov 2018 16:51:13 +0100 [thread overview]
Message-ID: <efae6915-eabf-de47-daa4-085bd6e4042c@gmail.com> (raw)
In-Reply-To: <3ee393c1-46c3-b6f6-0357-e6dc7f2b49de@mailbox.org>
Jan U. Hasecke schrieb am 14.11.18 um 11:39:
> Hi all,
>
> attached you find my colormanagement tests and I need your help to
> understand and debug the situation.
>
> I am testing together with a friend of mine, a professional
> colormanager, who does not know ConTeXt.
Even without a color profile the results from the normal conversion of
colors from cmyk to rgb
can result in differences between ConTeXt and Gimp because both use
different formulas.
This is the formula from ConTeXt (attr-col.lua)
r = 1.0 - math.min(1.0,c+k)
g = 1.0 - math.min(1.0,m+k)
b = 1.0 - math.min(1.0,y+k)
and this is the one from Gimp
(https://gitlab.gnome.org/GNOME/gimp/blob/master/libgimpcolor/gimpcolorspace.c)
r = 1.0 - math.min(1.0,c*(1.0-k)+k)
g = 1.0 - math.min(1.0,m*(1.0-k)+k)
b = 1.0 - math.min(1.0,y*(1.0-k)+k)
Wolfgang
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next prev parent reply other threads:[~2018-11-14 15:51 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-09 15:24 Colormanagement Jan U. Hasecke
2018-11-09 16:03 ` Colormanagement Hans Hagen
2018-11-09 16:18 ` Colormanagement Tomas Hala
2018-11-10 13:29 ` Colormanagement Jan U. Hasecke
2018-11-09 16:20 ` Colormanagement luigi scarso
2018-11-10 13:34 ` Colormanagement Jan U. Hasecke
2018-11-10 16:24 ` Colormanagement Hans Hagen
2018-11-12 8:02 ` Issues with RGB to CMYK conversion with color profiles (was: Colormanagement) Jan U. Hasecke
2018-11-12 8:34 ` Issues with RGB to CMYK conversion with color profiles Hans Hagen
2018-11-14 10:39 ` Issues with RGB to CMYK conversion with color profiles (was: Colormanagement) Jan U. Hasecke
2018-11-14 10:41 ` Jan U. Hasecke
2018-11-14 13:58 ` Peter Rolf
2018-11-14 14:36 ` Jan U. Hasecke
2018-11-14 15:04 ` Peter Rolf
2018-11-14 15:31 ` Jan U. Hasecke
2018-11-14 15:51 ` Wolfgang Schuster [this message]
2018-11-18 18:26 ` Issues with RGB to CMYK conversion with color profiles Hans Hagen
2018-11-19 9:56 ` Henning Hraban Ramm
2018-11-19 10:14 ` luigi scarso
2018-11-21 14:01 ` Jan U. Hasecke
2018-11-21 14:42 ` luigi scarso
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