[Wylug-help] CUPS printing

[Roger Leigh]

Anne Wilson <cannewilson@tiscali.co.uk> writes:

> I have my printer set up under CUPS with 4 different
> names/configurations.  I would like to be able to use the Grayscale
> setting to use black ink only, to avoid the muddy gray that the
> colour cartridge gives.  The printer can do it - under windows - but
> I have found no way of doing it under CUPS.
>
> During last meet's talk on printing, I made a note to check the CUPS
> admin tool for this.  I have looked at it again, but still can't find
> any such setting.  Does anyone know whether it is actually possible?

Firstly, go to the configuration screen for the printer:

http://localhost:631/admin/?op=config-printer&printer_name=queuename,
where queuename is the name of the printer)

On this screen the first option is Output Mode; change this to "Black &
White".

If you are using Gimp-Print, you can now use the "Ordered", "Fast" and
"Very Fast" dither algorithms, (in increasing order of speed/loss of
quality), because they are suited to fast B&W dithering without
noticeable loss in quality (because the higher quality dithers are
geared to high-res colour).  The Image Type can also be changed to
"Line Art".

There is a problem with this: a threshold intensity level is used to
determine what is black and what is white, with the result that half
the gray is black, and half is white, so this is very likely not what
you want...


With a setting of "Grayscale", colour inks will be used for all but
the darkest grays, because they usually give smoother, more pleasing,
shades.  For this reason (and it's certainly true for my printer), I
don't think Gimp-Print supports B&W dithered grays--you will need to
manually dither your image using gs first.  By forcing CUPS to give a
monochrome image to Gimp-Print (or whichever driver you are using), it
has no choice but to use black for everything.

(If anyone has tried any of the development versions of Gimp-Print,
it's possible to do this using the new support for Linear, Spline and
Gamma curves to create a sharp threshold and convert all colours to
grays--it's quite nifty.)

What you want to do is perfectly reasonable, and Gimp-Print can
certainly be made to do this, it just needs to let the user choose
"black ink only, please", which it doesn't currently allow.  The Epson
driver supports multiple inksets, but I'm not sure about the PCL (HP)
driver.  I'll see if this functionality can be added, and in the
mean-time, I would suggest looking at HPIJS/Foomatic as a possible
solution.


Regards,
Roger

--
Roger Leigh

                Printing on GNU/Linux?  http://gimp-print.sourceforge.net/
                GPG Public Key: 0x25BFB848 available on public keyservers