[OpenICC] colour palettes/lists
homann at colormanagement.de
Thu Sep 15 23:12:22 EST 2005
Hi Kai-Uwe, he list
There are two big differences in colorlists.
Easy colorlists containin a name and RGB or CMYK values which are may
connected to a standard-profile e.g. sRGB for webdesign or SWOP /
ISOcoated for print-design.
The resulting files for the complete design are RGB-files for web or
CMYK-files for printing
The next step are Lab-based colorlists, which can be converted to RGB or
CMYK with the standard-profiles for different design-projects. The
resulting files re still pure RGB or CMYK.
ncl2 style profiles are e.g. fine for it.
The last step are colorlists for printing processes wich are not
CMYK-based. In this case special inks (often named spot colors) are used
for printing. In PDF, such colors are stored as deviceN objects.
Working with such colors, we need iinformtions about gradation of tints
of such colors and a model for opacity / transparency.
Actually such parameters are not defined by the ICC.
In Photoshop, Adobe has a nice model by using a greyscale profile for
defining the gradation and value for opacity during definition of the color.
Actualy, I have not tested, if such information is stored, during "Save
as Photoshop-PDF" and is displayed correctly with the Acrobatreader.
If yes, we should look a littlebit deeper to the PDF-specifications, to
may find some more infos.
By the way, are there any people in the list, who are interested to
build a creative commons system for spotcolors in LINUC graphic arts
I will give a short overview, how this could be made:
If you are talking with ink-manufactures or ink-distributors, you can
order special Inks for e.g. offsetprinting by a Lab-specification.
So, instead of ordering Pantone XYZ, you order a color with Lab ABC.
A creative commons systems for spotcolors could e.g. based on the
LCH-System. The names of the spotcolors are the LCH-values.
This makes it easy for the designer to define harmonic colorgroups by
using the similar L, C or H values for a group of colors. From the view
of colormanagement, it is easy to convert LCH to Lab and display correct
colors on screen or print.
It is also easy to convert the colors to sRGB for webdesign or to
standard-printing-profile for using a CMYK eqivalent.
If the user has a profiled printer, he can print his own swatchbook.
If he want to go to to offset-printing, the printing house has to order
a ink specified by Lab-values.
For the realy professional users, the system allows an easy
quality-control for the printed product. Just measure the LCH/Lab values
on the printproduct and compare it to the original colordefinition.
If anyone is interested on doing this, lets work it out together in this
list and implement it e.g. in Scribus, Inkscape or other apps, which can
Kai-Uwe Behrmann wrote:
> I want to bring over a discussion from the create list:
> What is a usual/standard format to store colour lists for exchanging
> between applications.
> For years CGATS was used for profiling applications and later
> ncl2 style ICC profiles.
> Is something new coming, maybe like an xml based format?
> Kai-Uwe Behrmann
> + development for color management
> + imaging / panoramas
> + email: ku.b at gmx.de
> + http://www.behrmann.name
> openicc mailing list
> openicc at lists.freedesktop.org
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