On 11/14/2018 4:51 PM, Wolfgang Schuster wrote:
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....)
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) Are there more variants? Do we need to support variants?
Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------