[scribus] RGB to CMYK not using ICC profile for R=G=B colors

[Patrick Noffke]

On Thu, Dec 22, 2011 at 10:59 AM, Gregory Pittman <gregp_ky at yahoo.com>wrote:

> On 12/22/2011 11:10 AM, Patrick Noffke wrote:
>
>>
>>>
>>>  Another reason why I think this is incorrect behavior is with respect to
>> gradients.  If you create a rectangle with Black R=G=B=0 on the ends, and
>> a
>> dark red (for example), with R=75, G= 45, B=45 in the middle, then when
>> you
>> make the PDF, the black ends will get K only, and the middle will have
>> 4-color, with the CMYK coverage depending on the output intent (for the
>> SWOPcoated5_240 TAC profile, the middle red CMYK is (40%, 70%, 36%, 76%)).
>>  If you want to print this on a high-quality device, which is capable of
>> handling high TAC levels, the black ends will be too light from what the
>> author intends.  Or to put it another way, if you work with RGB colors, to
>> get a nice saturated black on a high quality device, you have to create a
>> color like R=0, G=1, B=0.
>>
>> What do others think?  I'm happy to file a bug report (with a patch), if
>> you think it makes sense to change the behavior.
>>
>>  From time to time, we have this discussion, about what black is, how
> black black is, etc. You might consider whether to use rich black in your
> instance:
>
> http://wiki.scribus.net/**canvas/What_is_Rich_Black%3F<http://wiki.scribus.net/canvas/What_is_Rich_Black%3F>
>
> but I don't think that Scribus should make this decision for you. If
> someone such as yourself has knowledge of and uses a high-quality printer,
> then you would want to be aware of options, but even then, there are
> various options.
>
> Greg
>
>
I'm concerned about the general usability, not so much my particular
instance anymore.

I completely agree on having some pre-defined CMYK colors, such as "Black"
which is defined as C=M=Y=0, K=100.  Though perhaps this should be called
"Process Black."

But when a user is working with RGB colors (including custom ones),
shouldn't the output intent determine how rich the colors become?  And in
the gradient example I gave, the red in the middle will be darker (in terms
of L*) than the edges, due to the higher total coverage.  I cannot see how
this would be the intended result.

Pat
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