[Openicc] color-policy / RGB to CMYK

[Leonard Rosenthol]

At 01:50 PM 3/1/2005, Jan-Peter Homann wrote:
>If the free available SWOP-profile from Adobe is used as outputprofile in 
>Scribus, all RGB-gray or RGB-black is converted to CMYK-colors with each 
>channel containing some color. This happens because of the fixed 
>black-generation in an CMYK ICC-profile.
>If the user wants RGB-gray or RGB-black only converted to the 
>black-channel of the CMYK-output, he needs a version of the SWOP-profile 
>with maximum GCR.

         UNLESS the color managing software (Scribus in this case), is 
smart enough to special case R==G==B and handle it as a direct map to [0 0 
0 1-R].  This is similar in concept to what the Windows PS driver or tools 
such as PDF Enhancer (http://www.pdfenhancer.com) do.


>So the functionality of changing the black generation in an 
>ICC-CMYK-profile is something, which is useful for all softwares, 
>targeting the graphics arts market.

         Yes, but it's also a complex operation that most users won't 
understand.  Most folks don't get color management as is - and adding 
something like Black Gen is just going to confuse them...


>A second big market is e.g. producing CMYK-PDF from docbook-manuals.
>In manuals, you have often a lot of screenshots. If Screenshots should be 
>printed in offset, RGB-black should stay pure CMYK-black.

         See above ;).

         But you are right, that is easier to solve on images via ICC since 
for images are you (hopefully) sending entire scanlines into the CMS.


Leonard

---------------------------------------------------------------------------
Leonard Rosenthol                            <mailto:leonardr at pdfsages.com>
Chief Technical Officer                      <http://www.pdfsages.com>
PDF Sages, Inc.                              215-938-7080 (voice)
                                              215-938-0880 (fax)