[Openicc] CUPS Color Management under Linux... (what is to do ?)

[Graeme Gill]

Hal V. Engel wrote:
> 1.  If an app turns this switch on and then sends a PDF with only DeviceXXX
> objects and with no OutputIntent then this is an app that is explicity
> requesting that the output go unaltered to the printer.   There is absolutely
> no ambiguity.

What if a DeviceXXX inappropriate for the device is used ? How are device independent
colorspace definitions handled ? (ie. should it error ?)

[One of the issues we saw in the PS world was PS files that were in just
  a single device space DeviceRGB or DeviceCMYK _except_ that they had
the odd bits of DeviceGray for lettering, lines etc. It shouldn't happen,
but it did.]

> 3. Like #2 except the app sets an OutputIntent and it is over riding the
> system default profile.  The profile setup in OutputIntent will always be used.

What about 3a, where you want to proof ? (ie. the file gets rendered to the
OutputIntent, and then re-rendered to the actual output device).

> 4. If the app does not set this switch then we know it is CM dumb and any
> untagged RGB objects are assumed to be sRGB and will be tagged by the CPD that
> way before the PDF is sent to CUPS.   Most existing apps will be of this type.
> This is the "it just works" case where the app sends the CPD a PDF that may
> not be well formed from a CM point of view and it expects the printing workflow
> to do the best it can with it even if the result is not perfect.  I am not
> sure what to do if such a file has CMY(K) objects.  Perhaps tag these with a
> SWAP profile or something similar?  On the other hand I don't expect too may CM

The correct answer is that it should be configurable somewhere, even if
its a single global setting. An arbitrary hard coded behaviour will not work
well in the real world.

A question to be answered is how existing PDF files are handled. Is it
assumed that they will be re-processed into PDF spool files that follow
the above scheme ? There's a big temptation for apps to just shovel
them at the spooler, and at that point you need a lot more configurability
to get the right result out of an arbitrary PDF.

Graeme Gill.