[okular] [Bug 449709] Print Color Mode: not possible to print in black-white

[Sergio]

https://bugs.kde.org/show_bug.cgi?id=449709

--- Comment #17 from Sergio <sergio.callegari at gmail.com> ---
I have looked a bit more into this. My conclusions:

1. I do not think that this is an issue in okular at all.
2. The problem is with cups, but won't be fixed because cups developers think
they are right and that printer manufacturers are wrong. See the exchange at
https://github.com/OpenPrinting/cups/issues/1364#issuecomment-3292398029. They
seem not to care very much about the fact that you need to print on real world
printer that work in the way their manufacturers choose. They might well not be
right either. But still "don'tfix".
3. You see the issue with okular and not with other PDF viewers, because when
you ask to print in B/W, okular passes the original job to the printer driver
telling it to print in B/W, while most viewers rasterize it in B/W to start
with. But I think that the okular behavior is the correct one.
4. Given the fact that the problem in cups won't be fixed, at this point there
are only two possible solutions. The first one is to use printers only via
driverless printing for which the color/BW selection works. Unfortunately, this
is often not something that can be done. Not all printers support driverless
operation and even for those that do, cups in this mode often gives you an
unacceptably bad rasterization (experiencing this with Brother and Canon
printers). The second solution is to set up two different queues, one for B/W
printing and the other one for color printing. This is basically, installing
each printer twice and set the color/BW mode at the printer install time (i.e.
at the queue level). Also horrible, but probably the best solution.

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