[cairo] Subtractive API, part 0

[ecir hana]

On Sat, Jan 30, 2010 at 9:07 PM, Chris Murphy <lists at colorremedies.com> wrote:

> On Jan 29, 2010, at 4:32 PM, ecir hana wrote:

>> For printing, even with untagged cmyk, nothing stops the application
>> or CMS to supply correct cmyk values to Cairo. Those values would get
>> baked-in into the pdf, making them possibly unusable on another device
>> - so what? Do you print a poster on two different printers?

> Absolutely, all the time. Movie posters will be printed on dozens of printers, perhaps in multiple geographic locations.

I'm  still trying to connect the dots and struggling with this one:

I read your post above as if you were suggesting that the better
alternative to untagged CMYK PDF would be tagged one because the
printer at the other location could easily just swap the profile and
print it on different paper, say.

But that means going to LAB again, and back to CMYK again. And I just
did a small experiment, trying to convert 40% 30% 30% 100% CMYK SWOP
to Euroscale Coated and it completely messed-up the colors. And from
the little I read about ICC profiles it seems (?) that there is no
official way (intent) of how to preserve such blacks.

> Untagged CMYK in a PDF is OK, but I would then require that an outputintent is set for the PDF, so that we know what the intended CMYK output condition is, in case the PDF needs to be repurposed.

So wouldn't it better solution to just use untagged PDF and then name
the file something like "new_movie-poster_final-cmyk_uncoated.pdf"
(that's only because I'm not yet familiar with PDF specs on
"outputintent", yet)?