[OpenICC] colour palettes/lists

[Jan-Peter Homann]

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 
applications ?

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 
handle colorlists.

:-) Jan-Peter











Kai-Uwe Behrmann wrote:
> Hi,
> 
> 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? 
> 
> regards
> 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
> http://lists.freedesktop.org/mailman/listinfo/openicc
> 


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